US20070087505A1 - Method of forming a semiconductor device - Google Patents
Method of forming a semiconductor device Download PDFInfo
- Publication number
- US20070087505A1 US20070087505A1 US11/538,760 US53876006A US2007087505A1 US 20070087505 A1 US20070087505 A1 US 20070087505A1 US 53876006 A US53876006 A US 53876006A US 2007087505 A1 US2007087505 A1 US 2007087505A1
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- US
- United States
- Prior art keywords
- oxide
- gate
- providing
- level
- semiconductor device
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000000034 method Methods 0.000 title claims abstract description 60
- 239000004065 semiconductor Substances 0.000 title claims abstract description 23
- 238000004140 cleaning Methods 0.000 claims abstract description 27
- 230000003647 oxidation Effects 0.000 claims abstract description 25
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 25
- 230000003750 conditioning effect Effects 0.000 claims abstract description 12
- BPUBBGLMJRNUCC-UHFFFAOYSA-N oxygen(2-);tantalum(5+) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ta+5].[Ta+5] BPUBBGLMJRNUCC-UHFFFAOYSA-N 0.000 claims description 50
- 239000000356 contaminant Substances 0.000 claims description 21
- 238000000151 deposition Methods 0.000 claims description 10
- 239000000463 material Substances 0.000 claims description 10
- PBCFLUZVCVVTBY-UHFFFAOYSA-N tantalum pentoxide Inorganic materials O=[Ta](=O)O[Ta](=O)=O PBCFLUZVCVVTBY-UHFFFAOYSA-N 0.000 claims description 8
- 230000001590 oxidative effect Effects 0.000 claims description 7
- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims description 7
- 229920005591 polysilicon Polymers 0.000 claims description 7
- 229910052732 germanium Inorganic materials 0.000 claims description 5
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 5
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 claims description 4
- NRTOMJZYCJJWKI-UHFFFAOYSA-N Titanium nitride Chemical compound [Ti]#N NRTOMJZYCJJWKI-UHFFFAOYSA-N 0.000 claims description 2
- 238000005247 gettering Methods 0.000 claims description 2
- 230000003472 neutralizing effect Effects 0.000 claims description 2
- 230000005855 radiation Effects 0.000 claims description 2
- 239000000126 substance Substances 0.000 claims description 2
- 229910052721 tungsten Inorganic materials 0.000 claims description 2
- 239000010937 tungsten Substances 0.000 claims description 2
- -1 tungsten nitride Chemical class 0.000 claims description 2
- 230000001939 inductive effect Effects 0.000 claims 1
- 230000001678 irradiating effect Effects 0.000 claims 1
- 239000000758 substrate Substances 0.000 abstract description 34
- 230000015654 memory Effects 0.000 abstract description 12
- 230000015572 biosynthetic process Effects 0.000 abstract description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 abstract 2
- 229910052757 nitrogen Inorganic materials 0.000 abstract 1
- 238000003672 processing method Methods 0.000 abstract 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 38
- 235000012431 wafers Nutrition 0.000 description 20
- 239000000377 silicon dioxide Substances 0.000 description 19
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 17
- 229910052710 silicon Inorganic materials 0.000 description 17
- 239000010703 silicon Substances 0.000 description 17
- 239000000470 constituent Substances 0.000 description 8
- 238000012876 topography Methods 0.000 description 8
- 238000002955 isolation Methods 0.000 description 7
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 6
- WGTYBPLFGIVFAS-UHFFFAOYSA-M tetramethylammonium hydroxide Chemical compound [OH-].C[N+](C)(C)C WGTYBPLFGIVFAS-UHFFFAOYSA-M 0.000 description 6
- 239000000460 chlorine Substances 0.000 description 5
- 229910052801 chlorine Inorganic materials 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 230000007547 defect Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 229910052581 Si3N4 Inorganic materials 0.000 description 3
- 239000012298 atmosphere Substances 0.000 description 3
- 239000008367 deionised water Substances 0.000 description 3
- 229910021641 deionized water Inorganic materials 0.000 description 3
- 230000008021 deposition Effects 0.000 description 3
- 230000000873 masking effect Effects 0.000 description 3
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 2
- 238000000429 assembly Methods 0.000 description 2
- 230000000712 assembly Effects 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 238000005229 chemical vapour deposition Methods 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 239000012299 nitrogen atmosphere Substances 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000002161 passivation Methods 0.000 description 2
- 229910001868 water Inorganic materials 0.000 description 2
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- 230000005689 Fowler Nordheim tunneling Effects 0.000 description 1
- 208000012868 Overgrowth Diseases 0.000 description 1
- 229910000577 Silicon-germanium Inorganic materials 0.000 description 1
- LEVVHYCKPQWKOP-UHFFFAOYSA-N [Si].[Ge] Chemical compound [Si].[Ge] LEVVHYCKPQWKOP-UHFFFAOYSA-N 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 239000000908 ammonium hydroxide Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- MROCJMGDEKINLD-UHFFFAOYSA-N dichlorosilane Chemical compound Cl[SiH2]Cl MROCJMGDEKINLD-UHFFFAOYSA-N 0.000 description 1
- 239000003989 dielectric material Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910052736 halogen Inorganic materials 0.000 description 1
- 150000002367 halogens Chemical class 0.000 description 1
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 1
- 230000005661 hydrophobic surface Effects 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 239000013618 particulate matter Substances 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- MZLGASXMSKOWSE-UHFFFAOYSA-N tantalum nitride Chemical compound [Ta]#N MZLGASXMSKOWSE-UHFFFAOYSA-N 0.000 description 1
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- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
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- H01L21/28211—Making the insulator on single crystalline silicon, e.g. using a liquid, i.e. chemical oxidation in a gaseous ambient using an oxygen or a water vapour, e.g. RTO, possibly through a layer
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- H01L21/3165—Inorganic layers composed of oxides or glassy oxides or oxide based glass formed by oxidation
- H01L21/31654—Inorganic layers composed of oxides or glassy oxides or oxide based glass formed by oxidation of semiconductor materials, e.g. the body itself
- H01L21/3167—Inorganic layers composed of oxides or glassy oxides or oxide based glass formed by oxidation of semiconductor materials, e.g. the body itself of anodic oxidation
- H01L21/31675—Inorganic layers composed of oxides or glassy oxides or oxide based glass formed by oxidation of semiconductor materials, e.g. the body itself of anodic oxidation of silicon
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/76—Making of isolation regions between components
- H01L21/762—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers
- H01L21/76202—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using a local oxidation of silicon, e.g. LOCOS, SWAMI, SILO
- H01L21/76221—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using a local oxidation of silicon, e.g. LOCOS, SWAMI, SILO with a plurality of successive local oxidation steps
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/40—Electrodes ; Multistep manufacturing processes therefor
- H01L29/43—Electrodes ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
- H01L29/49—Metal-insulator-semiconductor electrodes, e.g. gates of MOSFET
- H01L29/51—Insulating materials associated therewith
- H01L29/518—Insulating materials associated therewith the insulating material containing nitrogen, e.g. nitride, oxynitride, nitrogen-doped material
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/40—Electrodes ; Multistep manufacturing processes therefor
- H01L29/401—Multistep manufacturing processes
- H01L29/4011—Multistep manufacturing processes for data storage electrodes
- H01L29/40114—Multistep manufacturing processes for data storage electrodes the electrodes comprising a conductor-insulator-conductor-insulator-semiconductor structure
Definitions
- the present invention relates to the formation of semiconductor devices. More particularly, the present invention relates to the formation of an oxide layer as part of a device or as used in the fabrication of the device.
- oxide films are used in a variety of applications. Oftentimes they are used for scratch protection and passivation purposes. Oxide films are also used as a dielectric or insulative layer, electrically separating various regions or structures. For example, an oxide film can be used as a dielectric between different levels of metal in a semiconductor device. Such a film could also be used for field isolation. Moreover, an oxide film can serve as a gate oxide, wherein the film is provided above an area, such as a semiconductor substrate, having a source region, a drain region, and an interposing channel region. A gate, in turn, is formed on the oxide film.
- the voltage applied to the gate must reach a particular threshold before overcoming the insulative effects of the oxide and allowing current to flow through the channel.
- an oxide is formed in order to electrically insulate one device, such as a transistor, from another.
- providing the oxide typically begins by exposing designated oxide regions of a substrate to an oxidizing ambient through a patterned mask.
- the mask may be made, for example, of silicon nitride.
- the substrate represents the surface of a wafer and is comprised generally of silicon. Nevertheless, this invention is understood to cover devices having a substrate comprising any construction made of semiconductive material, including but not limited to bulk semiconductive materials such as a semiconductor wafer (either alone or in assemblies comprising other materials thereon) and semiconductive material layers (either alone or in assemblies comprising other materials).
- the unprotected portions of the silicon substrate oxidize into silicon dioxide (SiO 2 ).
- SiO 2 silicon dioxide
- the silicon at and below the surface of the substrate that oxidizes is often referred to as having been “consumed.” It follows that the amount of silicon consumed can indicate the depth of SiO 2 beneath the substrate's original surface. As a result, greater consumption allows for a greater depth of SiO 2 and, thus, greater electrical isolation between devices or between active areas within a device.
- the consuming effect of oxide films on silicon serves other purposes as well. For example, greater consumption in a particular area of the wafer allows access to a lower level of silicon within the substrate. Accordingly, removing the oxide results in a wafer topography having different elevations of silicon, depending upon the amount of prior oxidation in each area. This is particularly helpful in embedded dynamic random access memory (DRAM) processing, wherein the memory cell array should be embedded deeper within the wafer than other memory elements.
- DRAM embedded dynamic random access memory
- Oxidizing the exposed substrate is often referred to as “growing” the oxide.
- Oxides can be grown in a “dry” process using oxygen (O 2 ) or in a “wet” process using steam as the oxidizing agent.
- oxides can be deposited on the substrate with techniques such as sputter deposition or chemical vapor deposition (CVD).
- Oxide layers have a large impact on device performance due to their role in isolating active device regions and in establishing voltage thresholds for devices. Thus, there is always a need in the art for high quality oxide films. Further, as the dimensions of semiconductor devices are scaled down to enhance circuit density and speed, the oxide films must advance accordingly. Therefore, those skilled in the art are constantly striving to provide oxide films that are thinner and that have a high dielectric constant.
- defects in the oxide can occur due to the presence of certain constituents within the layer, such as contaminants exposed to the oxide.
- particulate matter in the process atmosphere is one source of contamination.
- filters and other techniques attempt to remove particles from the environment, particles that are too small for these techniques to handle may nevertheless end up within the oxide layer.
- Further attempts at reducing defects have been made by clustering together the chambers for several wafer processes in an environment isolated from and even more controllable than the clean room atmosphere. Transferring the wafers between the clustered chambers can involve the use of a wafer carrier capable of maintaining a vacuum or a nitrogen atmosphere. See, for example, U.S. Pat. No.
- FIG. 1 is a process flow diagram of one exemplary embodiment of the present invention.
- FIGS. 2 a through 2 e illustrates a prior art process for forming an embedded DRAM.
- FIGS. 3 a through 3 c depicts a second exemplary embodiment of the current invention.
- FIGS. 4 a through 4 e demonstrates a third exemplary embodiment of the current invention.
- FIG. 5 shows a portion of a flash-electrically erasable programmable read only memory.
- FIG. 6 illustrates an in-process semiconductor device that is electrically isolated using a shallow trench isolation process.
- At least one embodiment of the current invention comprises a cleaning stage 20 , a stage involving forming an oxide (or an oxynitride) 22 , and a stage of forming a structure 24 .
- cleaning stage 20 includes a vapor clean 20 b .
- this vapor clean 20 b is performed in at least five seconds and occurs at a temperature ranging between 50° and 75° C.
- This vapor clean 20 b may take the form of an ultraviolet-chlorine clean, wherein ultraviolet light excites and dissociates a gas containing chlorine. As a result, chlorine radicals are generated.
- This ultraviolet-chlorine clean generally takes between ten and sixty seconds and may occur at pressures less than, greater than, or equal to 760 torr.
- the temperature for this process is generally between 50° and 150° C. but is preferably between 60° and 80° C.
- the vapor clean 20 b may comprise an HF vapor clean.
- the pressure should be 1 mtorr
- the temperature should be less than 200° C.
- the exposure to HF should last five to ten seconds.
- the pH can be established at any level between 1 and 10.
- Still other alternatives include using tetramethylammonium hydroxide (TMAH) in the vapor clean process to assist in cleaning.
- TMAH tetramethylammonium hydroxide
- the TMAH is assumed to have a pH of 3, although one of ordinary skill in the art can appreciate that the pH level can vary according to the particular passivation requirements of a given embodiment.
- the cleaning stage helps to remove residue from etches executed earlier in the device-formation process.
- an optional wet clean 20 a may be performed in addition to the vapor clean 20 b .
- the wet clean 20 a is performed before the vapor clean 20 b .
- This wet clean step 20 a may be an RCA clean, which involves cleaning solutions developed by RCA. These solutions employ hydrogen peroxide chemistry, the two most common solutions being “standard clean 1” (SC-1) and “standard clean 2” (SC-2).
- SC- 1 typically comprises ammonium hydroxide, hydrogen peroxide, and deionized water in the following volume ratio: 1 NH 4 OH:1 H 2 O 2 :5 H 2 O.
- the solution SC- 2 generally has the following composition: 6 H 2 O:1 H 2 O 2 :1 HCl.
- wafers are immersed in the RCA cleaning solutions for 10 minutes at 20° to 80° C. for each solution, with deionized water rinses between immersions. There is also a final deionized water rinse after all immersions.
- the wet clean 20 a serves to passivate the wafer by allowing for a termination of the silicon surface with hydrogen atoms. In this way, a hydrophilic or a hydrophobic surface can be prepared.
- this stage 22 initially involves growing an oxide on the wafer surface 22 c , which consumes the silicon down to a particular level within the substrate.
- the current invention includes embodiments wherein oxide is deposited 22 b at the initiation of this stage 22 .
- oxide growth can be accomplished through a rapid thermal oxidation (RTO) process 22 d at a temperature generally ranging from 800° to 1100° C. This RTO process 22 d is carried out until it has produced an oxide thickness of at least generally 10 angstroms.
- RTO rapid thermal oxidation
- an ultraviolet-ozone treatment 22 a wherein ultraviolet radiation is used to enhance the oxidation rate of the silicon substrate in an ozone environment.
- This treatment 22 a is preferably carried out long enough to provide a high-quality oxide layer having a thickness generally ranging from 10 to 15 angstroms. Regardless of whether the oxide is provided in one step or a plurality of steps, it is preferable to have approximately 30 to 40 angstroms of oxide once step 22 d has been completed.
- oxide 22 g there is an option to provide additional amounts of oxide 22 g .
- Further growth 22 k from the consumption of silicon may be used to provide oxide similar to that resulting from the initial growth.
- an oxide, such as Ta 2 O 5 ( 22 h ) could be deposited.
- a greater oxide contribution in one step may relieve the need to produce more oxide in other steps.
- This “given thickness” of oxide varies depending on the structures formed, as one skilled in the art can appreciate. Exemplary thicknesses are discussed below.
- an optional additional cleaning step 22 e such as a second vapor clean 22 f performed after an oxidation step and, preferably, interposed between oxidation steps such as 22 d and 22 g .
- this vapor clean 22 f some or all of the oxide present may be removed. If a gate dielectric such as Ta 2 O 5 is deposited, some of the oxide provided in a prior step should remain to act as an adhesion layer between the substrate and the gate dielectric.
- this second vapor clean 22 f also serves to remove defects that would otherwise exist in the finished device.
- Defective oxides can arise if there are certain constituents, such as contaminants, in the silicon from which the oxide grows. As the silicon is consumed in steps such as 22 d and 22 a , the resulting oxide may retain those contaminants. By removing all or part of this grown oxide, the second vapor clean 22 f also removes those contaminants associated with the removed oxide.
- FIG. 2 illustrates how this topography is achieved in the prior art.
- a thin layer of SiO 2 30 is grown on the silicon substrate 32 .
- FIG. 2 b indicates that the SiO 2 layer 30 is then covered with a mask layer 34 , such as one made of silicon nitride.
- the mask layer 34 is patterned to expose an area 36 where further oxide growth is desired. Additional oxide growth is then carried out in FIG.
- FIG. 2 d the mask 34 and SiO 2 layer 30 are removed, leaving behind a bi-level topography for the substrate 32 . It is preferred that the resulting levels be parallel, but differences in slopes are allowable to the extent that the devices would still be functional. Further oxidation and masking steps are carried out to form structures such as the field oxide isolation regions 38 and gate oxide regions 40 and 41 depicted in FIG. 2 e .
- This prior art method depends on the higher levels of the substrate 32 being relatively free of constituents such as contaminants. Should the substrate 32 be contaminated in an area under the mask layer 34 , then the gate oxide 40 formed by consuming silicon in that area will also be contaminated.
- FIG. 3 a depicts the unoxidized substrate 32 having contaminants 42 . Some of these contaminants 42 become part of the grown SiO 2 layer 30 after oxidation, as depicted in FIG. 3 b .
- the effect of the second vapor clean step 22 f , shown in FIG. 1 can be seen in FIG. 3 c , wherein the SiO 2 layer 30 , along with its associated contaminants 42 , is removed. Subsequent oxidation, masking, and removal steps may then be taken to achieve the bi-level topography needed for embedded DRAM devices. Assuming some contaminants 42 remain in the substrate 32 , the subsequent oxidation and removal steps will preferably eliminate most if not all of these contaminants 42 .
- FIG. 4 a once again shows the substrate 32 with the SiO 2 layer 30 grown on top.
- FIG. 4 b depicts the in-process wafer after the second vapor clean 22 f , wherein only part of the SiO 2 layer 30 has been removed as a result of that cleaning.
- this partial oxide removal or subsequent oxide removals will eliminate most if not all of any existing contaminants or other undesired constituents within the SiO 2 layer. Assuming an exemplary embedded memory topography is desired, it is preferred that approximately 40 angstroms of the SiO 2 layer 30 remain after the second vapor clean 22 f .
- the mask layer 34 is then provided and patterned to expose the area 36 . If desired, further cleaning steps could be taken to remove more of the exposed SiO 2 layer 30 before additional oxide is grown. Alternatively, one may retain the existing SiO 2 layer and continue to grow more oxide, as demonstrated in FIG. 4 d . Regardless of whether this latest cleaning is performed, it is preferred that the final thickness of the SiO 2 layer 30 in the exposed area 36 be within a range of approximately 70 to 90 angstroms for this exemplary embedded memory structure. Removing the SiO 2 layer 30 and the mask layer 34 reveals the bi-level topography of the wafer of FIG. 4 e . Field oxide regions and gate oxide regions may then be formed by the oxidation/cleaning steps described in the above embodiments or by a method known in the art.
- a nitridation step 22 j (seen in FIG. 1 ) may be performed on the oxide layer.
- One possible way to carry out this step 22 j involves rapid thermal nitridation (RTN), wherein ammonia (Nh 3 ) is introduced to the wafer environment and heated with a source, such as a halogen lamp, to a temperature generally ranging from 850° to 1050° C. As a result of this process, the oxide film is rapidly changed to an oxynitride film.
- RTN rapid thermal nitridation
- an optional conditioning step 22 i may be performed.
- this conditioning step 22 i comprises hardening the oxide in a nitridizing ambient, such as NO or N 2 O.
- a nitridizing ambient such as NO or N 2 O.
- the conditioning step can alternatively include exposure to an ambient comprised of Nh 3 ; dichlorosilane (SiCl 2 H 2 ) and Nh 3 ; an oxygen environment, such as ozone; N 2 ; Ar; or H 2 .
- This exposure would last for at least ten seconds at preferably five to fifteen atmospheres and at a temperature generally between 500° to 750° C.
- Another conditioning alternative involves steam oxidation, wherein the dielectric is exposed to a mixture of H 2 and O 2 .
- a plasma torch is not used; rather, H 2 and O 2 are brought together within the process chamber at a pressure of generally one atmosphere or lower and at a temperature generally ranging from 500° to 900° C.
- an embodiment of the current invention is used to provide a gate oxide, one advantage will be to reduce the current leakage of a device or, at least, counteract factors that could increase the leakage.
- the cleaning, oxidizing, and conditioning steps described above have uses in addition to altering the topography of the silicon substrate and to providing some form of gate oxide. These steps, for example, can be used to form the tunnel oxide 44 of a flash memory cell 46 depicted in FIG. 5 , as well as the entire oxide 48 for that cell 46 .
- the flash memory cell 46 pictured is more specifically a flash-electrically erasable programmable read only memory (flash-EEPROM) cell formed in a p-type substrate 50 having n-type source and drain regions 52 , 54 .
- flash-EEPROM flash-electrically erasable programmable read only memory
- a floating gate 56 is provided within the oxide 48 .
- a control gate 58 is also within oxide 48 and is located over the floating gate 56 .
- the floating gate 56 is separated from the substrate by the tunnel oxide 44 .
- This tunnel oxide 44 is a relatively thin oxide layer; while it can be as thin as thirty to forty angstroms, it is preferably closer to seventy to one hundred angstroms thin.
- the tunnel oxide 44 is so named because memory programming and erasing is accomplished by way of Fowler-Nordheim tunneling through this tunnel oxide 44 .
- the tunnel oxide 44 could be provided through an initial oxidation step with a cleaning to reduce the oxide to a desired thickness.
- the oxide could be completely cleaned away, allowing a subsequent oxidation step to form the tunnel oxide 44 at a lower level of the substrate 50 .
- the rest of the oxide 48 could be formed by an additional oxidation step or by still more oxidation/cleaning cycles.
- these cleaning, oxidizing, and conditioning steps can be used to provide a gate oxide for devices isolated using a shallow trench isolation (STI) process.
- STI shallow trench isolation
- FIG. 6 Such a device in-progress appears in FIG. 6 , wherein an etched substrate 60 defines trenches 62 that electrically isolate one cell site from another.
- the gate oxide 66 is grown in a high-pressure oxidation environment using the steps described above. For instance, the gate oxide 66 could be grown at a pressure generally ranging from five to fifteen atmospheres.
- the specific steps taken within the stage of forming a structure 24 will depend in part on the context in which the oxide is formed—such as whether it is formed for a gate in an embedded DRAM or to sculpt the substrate to accommodate such a gate, for a floating gate in a tunnel oxide, for a gate in an STI cell, or for other structures.
- the stage of forming a structure 24 will involve a step of forming a gate 24 a which, in turn, is often formed by depositing a polysilicon film.
- a silicon-germanium film may be provided as an option by doping the polysilicon film with germanium, wherein the germanium concentration may generally range from 2% to 25%.
- Other alternatives to depositing polysilicon include depositing tantalum nitride, titanium nitride, and tungsten nitride.
- the wafer may undergo further processing, such as steps taken to form word lines. It should also be noted that, in a preferred embodiment, it is desirable to cluster the steps from the first vapor clean 20 b to the stage involving forming a structure 24 . Of course, in an even more preferred embodiment, every step would be clustered. This would serve to further reduce the constituents such as contaminants that might appear in an oxide as well as other layers.
- this documents discusses, among other things, methods for providing an oxide layer during the processing of a semiconductor device.
- One exemplary embodiment relates to a method wherein an oxide is provided on a substrate surface and is then subjected to a cleaning process, followed by a provision of still more oxide.
- the oxide in either step could be grown or deposited.
- the cleaning step may be used to remove all or some of the first provision of oxide.
- This embodiment has the advantage of removing any oxide that may carry constituents such as contaminants that were part of the underlying substrate.
- this embodiment can be used to provide a more contaminant-free oxide for a semiconductor device.
- this embodiment can be used to selectively consume portions of a substrate, thereby allowing memory structures such as embedded memories to be formed within the lower elevations of the substrate.
- Another exemplary embodiment allows for providing a gate dielectric having a high dielectric constant.
- dielectrics include oxides such as tantalum pentoxide (Ta 2 O 5 ), or layers produced through rapid thermal nitridation (RTN), such as oxynitrides.
- a layer of oxide or oxynitride serves as an adhesion layer between the substrate and the subsequently deposited Ta 2 O 5 .
- a cleaning step between providing the adhesion layer and providing the Ta 2 O 5 layer is optional.
- One advantage of this embodiment is that leakage current can be improved.
- Yet another exemplary embodiment covers a range of steps for processing the semiconductor device, including a vapor clean, an initial oxide growth or deposition, a subsequent oxide growth or deposition, an optional second vapor clean between the two oxide steps, an oxide hardening, and the formation of an electrode over the second oxide.
- these steps are clustered, wherein transportation between the various processes are performed in a common controlled environment, such as a nitrogen atmosphere or a vacuum.
- the cluster process environment lowers the amount of contaminants having access to the in-process semiconductor device, and the cleaning steps help to negate the effects of any contaminants that appear within the device despite the attempts to control the environment.
Abstract
In the formation of semiconductor devices, a processing method is provided, including steps for forming an oxide layer. The embodied methods involve a series of oxidation steps, with optional interposed cleanings, as well as an optional conditioning step after oxidation. In a preferred embodiment, these steps are clustered and transportation between the clustered process chambers takes place in a controlled environment such as nitrogen or a vacuum. In some embodiments, the method provides an oxide layer to be used as part of the device, such as a tunnel oxide for a flash-EEPROM, or as a general gate oxide. Alternatively, the steps can be used to sculpt through oxidation various levels of a substrate, thereby allowing for embedded memory architecture. Cleaning between oxidation steps offers the advantage of providing a more defect-free oxide layer or providing access to a more defect-free level of substrate.
Description
- This application is a divisional of application Ser. No. 10/133,132, filed Apr. 25, 2002; which is a divisional of application Ser. No. 09/652,723, filed Aug. 31, 2000, now U.S. Pat. No. 6,589,877; which is a divisional of application Ser. No. 09/017,453, filed Feb. 2, 1998, now U.S. Pat. No. 6,475,927.
- The present invention relates to the formation of semiconductor devices. More particularly, the present invention relates to the formation of an oxide layer as part of a device or as used in the fabrication of the device.
- In the semiconductor industry, oxide films are used in a variety of applications. Oftentimes they are used for scratch protection and passivation purposes. Oxide films are also used as a dielectric or insulative layer, electrically separating various regions or structures. For example, an oxide film can be used as a dielectric between different levels of metal in a semiconductor device. Such a film could also be used for field isolation. Moreover, an oxide film can serve as a gate oxide, wherein the film is provided above an area, such as a semiconductor substrate, having a source region, a drain region, and an interposing channel region. A gate, in turn, is formed on the oxide film. As a result, the voltage applied to the gate must reach a particular threshold before overcoming the insulative effects of the oxide and allowing current to flow through the channel. When used as field isolation, an oxide is formed in order to electrically insulate one device, such as a transistor, from another.
- Whether for field isolation purposes or for application in the gate stack of a transistor, providing the oxide typically begins by exposing designated oxide regions of a substrate to an oxidizing ambient through a patterned mask. The mask may be made, for example, of silicon nitride. For purposes of explaining the current invention, it is assumed that the substrate represents the surface of a wafer and is comprised generally of silicon. Nevertheless, this invention is understood to cover devices having a substrate comprising any construction made of semiconductive material, including but not limited to bulk semiconductive materials such as a semiconductor wafer (either alone or in assemblies comprising other materials thereon) and semiconductive material layers (either alone or in assemblies comprising other materials). Upon exposure to the oxidizing ambient, the unprotected portions of the silicon substrate oxidize into silicon dioxide (SiO2). The silicon at and below the surface of the substrate that oxidizes is often referred to as having been “consumed.” It follows that the amount of silicon consumed can indicate the depth of SiO2 beneath the substrate's original surface. As a result, greater consumption allows for a greater depth of SiO2 and, thus, greater electrical isolation between devices or between active areas within a device.
- The consuming effect of oxide films on silicon serves other purposes as well. For example, greater consumption in a particular area of the wafer allows access to a lower level of silicon within the substrate. Accordingly, removing the oxide results in a wafer topography having different elevations of silicon, depending upon the amount of prior oxidation in each area. This is particularly helpful in embedded dynamic random access memory (DRAM) processing, wherein the memory cell array should be embedded deeper within the wafer than other memory elements.
- Oxidizing the exposed substrate, as discussed above, is often referred to as “growing” the oxide. Oxides can be grown in a “dry” process using oxygen (O2) or in a “wet” process using steam as the oxidizing agent. As an alternative to growing, oxides can be deposited on the substrate with techniques such as sputter deposition or chemical vapor deposition (CVD).
- Oxide layers have a large impact on device performance due to their role in isolating active device regions and in establishing voltage thresholds for devices. Thus, there is always a need in the art for high quality oxide films. Further, as the dimensions of semiconductor devices are scaled down to enhance circuit density and speed, the oxide films must advance accordingly. Therefore, those skilled in the art are constantly striving to provide oxide films that are thinner and that have a high dielectric constant.
- However, during the deposition or growth of oxides, defects in the oxide can occur due to the presence of certain constituents within the layer, such as contaminants exposed to the oxide. For example, particulate matter in the process atmosphere is one source of contamination. Even when the oxide or other layers are developed in a “clean room” environment, wherein filters and other techniques attempt to remove particles from the environment, particles that are too small for these techniques to handle may nevertheless end up within the oxide layer. Further attempts at reducing defects have been made by clustering together the chambers for several wafer processes in an environment isolated from and even more controllable than the clean room atmosphere. Transferring the wafers between the clustered chambers can involve the use of a wafer carrier capable of maintaining a vacuum or a nitrogen atmosphere. See, for example, U.S. Pat. No. 5,613,821 and U.S. Pat. No. 5,344,365. Nonetheless, there is a constant need in the art for further lowering the number of defects in oxide films, including a need for methods of handling contaminants that find their way to the wafer despite the controlled environment.
-
FIG. 1 is a process flow diagram of one exemplary embodiment of the present invention. -
FIGS. 2 a through 2 e illustrates a prior art process for forming an embedded DRAM. -
FIGS. 3 a through 3 c depicts a second exemplary embodiment of the current invention. -
FIGS. 4 a through 4 e demonstrates a third exemplary embodiment of the current invention. -
FIG. 5 shows a portion of a flash-electrically erasable programmable read only memory. -
FIG. 6 illustrates an in-process semiconductor device that is electrically isolated using a shallow trench isolation process. - As seen in
FIG. 1 , at least one embodiment of the current invention comprises acleaning stage 20, a stage involving forming an oxide (or an oxynitride) 22, and a stage of forming astructure 24. These basic stages, 20, 22, and 24, further comprise more detailed steps. For example,cleaning stage 20 includes a vapor clean 20 b. In many cases this vapor clean 20 b is performed in at least five seconds and occurs at a temperature ranging between 50° and 75° C. This vapor clean 20 b may take the form of an ultraviolet-chlorine clean, wherein ultraviolet light excites and dissociates a gas containing chlorine. As a result, chlorine radicals are generated. These chlorine radicals act as gettering agents, penetrating the oxide layer and bonding with constituents therein, such as contaminants. These radicals are particularly useful in neutralizing the harm caused by metallic constituents within an oxide layer. This ultraviolet-chlorine clean generally takes between ten and sixty seconds and may occur at pressures less than, greater than, or equal to 760 torr. The temperature for this process is generally between 50° and 150° C. but is preferably between 60° and 80° C. - Alternatively, the vapor clean 20 b may comprise an HF vapor clean. As one example of the parameters needed for an HF vapor clean, the pressure should be 1 mtorr, the temperature should be less than 200° C., and the exposure to HF should last five to ten seconds. The pH can be established at any level between 1 and 10. Still other alternatives include using tetramethylammonium hydroxide (TMAH) in the vapor clean process to assist in cleaning. For purposes of explaining the current invention, the TMAH is assumed to have a pH of 3, although one of ordinary skill in the art can appreciate that the pH level can vary according to the particular passivation requirements of a given embodiment. Also for purposes of explanation, it is assumed that a wafer is undergoing the methods of the current invention, although this is not required to practice the invention, as individual devices could also be processed. In general, the cleaning stage helps to remove residue from etches executed earlier in the device-formation process.
- As a part of the
cleaning stage 20, an optional wet clean 20 a may be performed in addition to the vapor clean 20 b. Preferably, the wet clean 20 a is performed before the vapor clean 20 b. This wet clean step 20 a may be an RCA clean, which involves cleaning solutions developed by RCA. These solutions employ hydrogen peroxide chemistry, the two most common solutions being “standard clean 1” (SC-1) and “standard clean 2” (SC-2). The solution SC-1 typically comprises ammonium hydroxide, hydrogen peroxide, and deionized water in the following volume ratio: 1 NH4OH:1 H2O2:5 H2O. The solution SC-2 generally has the following composition: 6 H2O:1 H2O2:1 HCl. Typically wafers are immersed in the RCA cleaning solutions for 10 minutes at 20° to 80° C. for each solution, with deionized water rinses between immersions. There is also a final deionized water rinse after all immersions. The wet clean 20 a serves to passivate the wafer by allowing for a termination of the silicon surface with hydrogen atoms. In this way, a hydrophilic or a hydrophobic surface can be prepared. - Once the wafer surface has been cleaned, it is ready for oxide or oxynitride formation, as indicated by
stage 22. In many embodiments, thisstage 22 initially involves growing an oxide on the wafer surface 22 c, which consumes the silicon down to a particular level within the substrate. However, the current invention includes embodiments wherein oxide is deposited 22 b at the initiation of thisstage 22. - In at least one embodiment, oxide growth can be accomplished through a rapid thermal oxidation (RTO) process 22 d at a temperature generally ranging from 800° to 1100° C. This RTO process 22 d is carried out until it has produced an oxide thickness of at least generally 10 angstroms.
- In addition to this initial step of growing an oxide, there are additional steps which may take place to enhance the
oxide formation stage 22. For instance, after the vapor clean 20 b has been performed, yet before the RTO process 22 d begins, it may be beneficial to induce chemical oxide growth on the wafer through an ultraviolet-ozone treatment 22 a, wherein ultraviolet radiation is used to enhance the oxidation rate of the silicon substrate in an ozone environment. This treatment 22 a is preferably carried out long enough to provide a high-quality oxide layer having a thickness generally ranging from 10 to 15 angstroms. Regardless of whether the oxide is provided in one step or a plurality of steps, it is preferable to have approximately 30 to 40 angstroms of oxide once step 22 d has been completed. - Once the ultraviolet-ozone treatment 22 a and the
RTO process 22 dhave been performed, there is an option to provide additional amounts of oxide 22 g. Further growth 22 k from the consumption of silicon may be used to provide oxide similar to that resulting from the initial growth. Alternatively, an oxide, such as Ta2O5 (22 h), could be deposited. Regardless of the precise methods of providing oxides in these steps 22 d, 22 a, and 22 g, they are understood to cooperate in achieving a given thickness of oxide at the end of theoxide formation stage 22. Thus, a greater oxide contribution in one step may relieve the need to produce more oxide in other steps. This “given thickness” of oxide varies depending on the structures formed, as one skilled in the art can appreciate. Exemplary thicknesses are discussed below. - Achieving this given thickness of oxide is further aided by an optional additional cleaning step 22 e, such as a second vapor clean 22 f performed after an oxidation step and, preferably, interposed between oxidation steps such as 22 d and 22 g. As a result of this vapor clean 22 f, some or all of the oxide present may be removed. If a gate dielectric such as Ta2O5 is deposited, some of the oxide provided in a prior step should remain to act as an adhesion layer between the substrate and the gate dielectric. In addition to curing any problems that might result from an inadvertent overgrowth of oxide, this second vapor clean 22 f also serves to remove defects that would otherwise exist in the finished device. Defective oxides can arise if there are certain constituents, such as contaminants, in the silicon from which the oxide grows. As the silicon is consumed in steps such as 22 d and 22 a, the resulting oxide may retain those contaminants. By removing all or part of this grown oxide, the second vapor clean 22 f also removes those contaminants associated with the removed oxide.
- While the amount of oxide at the end of this
stage 22 may have a generally constant thickness, such a limitation is not necessary for the present invention. In fact, providing for variations in oxide thickness is actually desired in certain circumstances, such as in providing the topography needed for embedded DRAM memory devices.FIG. 2 illustrates how this topography is achieved in the prior art. As seen inFIG. 2 a, a thin layer ofSiO 2 30 is grown on thesilicon substrate 32.FIG. 2 b indicates that the SiO2 layer 30 is then covered with amask layer 34, such as one made of silicon nitride. Themask layer 34 is patterned to expose anarea 36 where further oxide growth is desired. Additional oxide growth is then carried out inFIG. 2 c, resulting in more silicon being consumed in the exposedarea 36, while most of the SiO2 layer 30 under thesilicon nitride mask 34 retains its original thickness. InFIG. 2 d, themask 34 and SiO2 layer 30 are removed, leaving behind a bi-level topography for thesubstrate 32. It is preferred that the resulting levels be parallel, but differences in slopes are allowable to the extent that the devices would still be functional. Further oxidation and masking steps are carried out to form structures such as the fieldoxide isolation regions 38 andgate oxide regions FIG. 2 e. This prior art method, however, depends on the higher levels of thesubstrate 32 being relatively free of constituents such as contaminants. Should thesubstrate 32 be contaminated in an area under themask layer 34, then thegate oxide 40 formed by consuming silicon in that area will also be contaminated. - At least one embodiment of the current invention is free of such dependency.
FIG. 3 a depicts theunoxidized substrate 32 havingcontaminants 42. Some of thesecontaminants 42 become part of the grown SiO2 layer 30 after oxidation, as depicted inFIG. 3 b. The effect of the second vapor clean step 22 f, shown inFIG. 1 , can be seen inFIG. 3 c, wherein the SiO2 layer 30, along with its associatedcontaminants 42, is removed. Subsequent oxidation, masking, and removal steps may then be taken to achieve the bi-level topography needed for embedded DRAM devices. Assuming somecontaminants 42 remain in thesubstrate 32, the subsequent oxidation and removal steps will preferably eliminate most if not all of thesecontaminants 42. - Moreover, it is not necessary to completely remove the initial SiO2 layer 30, as shown in the embodiment depicted in
FIGS. 4 a through 4 e.FIG. 4 a once again shows thesubstrate 32 with the SiO2 layer 30 grown on top.FIG. 4 b depicts the in-process wafer after the second vapor clean 22 f, wherein only part of the SiO2 layer 30 has been removed as a result of that cleaning. Preferably, this partial oxide removal or subsequent oxide removals will eliminate most if not all of any existing contaminants or other undesired constituents within the SiO2 layer. Assuming an exemplary embedded memory topography is desired, it is preferred that approximately 40 angstroms of the SiO2 layer 30 remain after the second vapor clean 22 f. Themask layer 34 is then provided and patterned to expose thearea 36. If desired, further cleaning steps could be taken to remove more of the exposed SiO2 layer 30 before additional oxide is grown. Alternatively, one may retain the existing SiO2 layer and continue to grow more oxide, as demonstrated inFIG. 4 d. Regardless of whether this latest cleaning is performed, it is preferred that the final thickness of the SiO2 layer 30 in the exposedarea 36 be within a range of approximately 70 to 90 angstroms for this exemplary embedded memory structure. Removing the SiO2 layer 30 and themask layer 34 reveals the bi-level topography of the wafer ofFIG. 4 e. Field oxide regions and gate oxide regions may then be formed by the oxidation/cleaning steps described in the above embodiments or by a method known in the art. - If an oxynitride layer is desired, then a nitridation step 22 j (seen in
FIG. 1 ) may be performed on the oxide layer. One possible way to carry out this step 22 j involves rapid thermal nitridation (RTN), wherein ammonia (Nh3) is introduced to the wafer environment and heated with a source, such as a halogen lamp, to a temperature generally ranging from 850° to 1050° C. As a result of this process, the oxide film is rapidly changed to an oxynitride film. - Regardless of the particular devices being developed on the wafer, once the correct amount of oxide or oxynitride is present, an optional conditioning step 22 i may be performed. In at least one embodiment, this conditioning step 22 i comprises hardening the oxide in a nitridizing ambient, such as NO or N2O. In other embodiments, particularly those involving high dielectric constant materials such as Ta2O5, the conditioning step can alternatively include exposure to an ambient comprised of Nh3; dichlorosilane (SiCl2H2) and Nh3; an oxygen environment, such as ozone; N2; Ar; or H2. This exposure would last for at least ten seconds at preferably five to fifteen atmospheres and at a temperature generally between 500° to 750° C. Another conditioning alternative involves steam oxidation, wherein the dielectric is exposed to a mixture of H2 and O2. Those skilled in the art understand that such a mixture may be generated by using a plasma torch. The current invention, however, also includes a conditioning step wherein a plasma torch is not used; rather, H2 and O2 are brought together within the process chamber at a pressure of generally one atmosphere or lower and at a temperature generally ranging from 500° to 900° C.
- If an embodiment of the current invention is used to provide a gate oxide, one advantage will be to reduce the current leakage of a device or, at least, counteract factors that could increase the leakage. Moreover, the cleaning, oxidizing, and conditioning steps described above have uses in addition to altering the topography of the silicon substrate and to providing some form of gate oxide. These steps, for example, can be used to form the
tunnel oxide 44 of aflash memory cell 46 depicted inFIG. 5 , as well as theentire oxide 48 for thatcell 46. Theflash memory cell 46 pictured is more specifically a flash-electrically erasable programmable read only memory (flash-EEPROM) cell formed in a p-type substrate 50 having n-type source and drainregions substrate 50, a floatinggate 56 is provided within theoxide 48. Acontrol gate 58 is also withinoxide 48 and is located over the floatinggate 56. The floatinggate 56 is separated from the substrate by thetunnel oxide 44. Thistunnel oxide 44 is a relatively thin oxide layer; while it can be as thin as thirty to forty angstroms, it is preferably closer to seventy to one hundred angstroms thin. Thetunnel oxide 44 is so named because memory programming and erasing is accomplished by way of Fowler-Nordheim tunneling through thistunnel oxide 44. Thus, through an embodiment of the current invention, thetunnel oxide 44 could be provided through an initial oxidation step with a cleaning to reduce the oxide to a desired thickness. Alternatively, the oxide could be completely cleaned away, allowing a subsequent oxidation step to form thetunnel oxide 44 at a lower level of thesubstrate 50. The rest of theoxide 48 could be formed by an additional oxidation step or by still more oxidation/cleaning cycles. - As another example, these cleaning, oxidizing, and conditioning steps can be used to provide a gate oxide for devices isolated using a shallow trench isolation (STI) process. Such a device in-progress appears in
FIG. 6 , wherein an etchedsubstrate 60 definestrenches 62 that electrically isolate one cell site from another. After providing atrench fill 64, thegate oxide 66 is grown in a high-pressure oxidation environment using the steps described above. For instance, thegate oxide 66 could be grown at a pressure generally ranging from five to fifteen atmospheres. - Given these varying environments for the oxide, the specific steps taken within the stage of forming a
structure 24 will depend in part on the context in which the oxide is formed—such as whether it is formed for a gate in an embedded DRAM or to sculpt the substrate to accommodate such a gate, for a floating gate in a tunnel oxide, for a gate in an STI cell, or for other structures. many instances, the stage of forming astructure 24 will involve a step of forming a gate 24 a which, in turn, is often formed by depositing a polysilicon film. Moreover, a silicon-germanium film may be provided as an option by doping the polysilicon film with germanium, wherein the germanium concentration may generally range from 2% to 25%. Other alternatives to depositing polysilicon include depositing tantalum nitride, titanium nitride, and tungsten nitride. - Once the stage of forming a
structure 24 has been completed, the wafer may undergo further processing, such as steps taken to form word lines. It should also be noted that, in a preferred embodiment, it is desirable to cluster the steps from the first vapor clean 20 b to the stage involving forming astructure 24. Of course, in an even more preferred embodiment, every step would be clustered. This would serve to further reduce the constituents such as contaminants that might appear in an oxide as well as other layers. - In general, this documents discusses, among other things, methods for providing an oxide layer during the processing of a semiconductor device. One exemplary embodiment relates to a method wherein an oxide is provided on a substrate surface and is then subjected to a cleaning process, followed by a provision of still more oxide. The oxide in either step could be grown or deposited. Moreover, the cleaning step may be used to remove all or some of the first provision of oxide. This embodiment has the advantage of removing any oxide that may carry constituents such as contaminants that were part of the underlying substrate. Thus, this embodiment can be used to provide a more contaminant-free oxide for a semiconductor device. Alternatively, this embodiment can be used to selectively consume portions of a substrate, thereby allowing memory structures such as embedded memories to be formed within the lower elevations of the substrate.
- Another exemplary embodiment allows for providing a gate dielectric having a high dielectric constant. Such dielectrics include oxides such as tantalum pentoxide (Ta2O5), or layers produced through rapid thermal nitridation (RTN), such as oxynitrides. In this embodiment, a layer of oxide or oxynitride serves as an adhesion layer between the substrate and the subsequently deposited Ta2O5. A cleaning step between providing the adhesion layer and providing the Ta2O5 layer is optional. One advantage of this embodiment is that leakage current can be improved.
- Yet another exemplary embodiment covers a range of steps for processing the semiconductor device, including a vapor clean, an initial oxide growth or deposition, a subsequent oxide growth or deposition, an optional second vapor clean between the two oxide steps, an oxide hardening, and the formation of an electrode over the second oxide. In a more preferred version of this embodiment, these steps are clustered, wherein transportation between the various processes are performed in a common controlled environment, such as a nitrogen atmosphere or a vacuum. The cluster process environment lowers the amount of contaminants having access to the in-process semiconductor device, and the cleaning steps help to negate the effects of any contaminants that appear within the device despite the attempts to control the environment.
- Finally, one skilled in the art can appreciate that, although specific embodiments of this invention have been described above for purposes of illustration, various modifications may be made without departing from the spirit and scope of the invention. For example, providing oxide under the current invention is not limited to at most two oxidation steps; any number of oxidation steps and cleaning steps as needed are covered, as shown by the arrow in
FIG. 1 looping from step 22 g back to 22 e. Further, any masking steps that might be needed to allow oxidation and cleaning in selected areas are also included. Accordingly, the invention is not limited except as stated in the claims.
Claims (23)
1. A method for forming a semiconductor device, comprising:
removing a contaminant from a surface of the semiconductor device;
forming a first oxide over the surface;
forming a second oxide over the surface;
forming an electrode over the surface; and
clustering the removing the contaminant, the providing the first oxide, the providing the second oxide, and the providing the electrode over the surface.
2. The method of claim 1 , wherein providing the first oxide over the surface comprises growing oxide on the surface.
3. The method of claim 2 , wherein growing the oxide on the surface comprises rapidly thermally oxidizing the surface.
4. The method of claim 3 , wherein growing the oxide on the surface comprises inducing chemical oxide growth through an ultraviolet-ozone treatment before rapidly thermally oxidizing the surface.
5. The method of claim 4 , wherein providing the second oxide comprises depositing the second oxide onto the grown oxide.
6. The method of claim 4 , wherein providing the second oxide comprises providing an oxide having a composition similar to a composition of the first oxide.
7. A method for processing a semiconductor device, comprising:
performing a vapor clean on the semiconductor device;
growing a first amount of oxide on the semiconductor device;
depositing a second amount of oxide on the semiconductor device; and
forming a gate on the second amount of oxide.
8. The method of claim 7 , further comprising gettering the first amount of oxide.
9. The method of claim 8 , wherein forming the gate comprises depositing polysilicon on the second amount of oxide.
10. The method of claim 9 , wherein forming the gate comprises doping the polysilicon with germanium.
11. The method of claim 10 , wherein doping the polysilicon with germanium comprises providing a germanium concentration generally ranging from 2% to 25% within the polysilicon.
12. A method for forming a gate for a semiconductor device, comprising:
bonding contaminants at a level of the semiconductor device;
providing an adhesion layer at a gate site on the level;
forming a gate oxide made of tantalum pentoxide over the gate site; and
providing a gate material over the gate oxide.
13. The method of claim 12 , wherein providing the adhesion layer comprises providing an oxynitride layer over the level.
14. The method of claim 13 , further comprising conditioning the gate oxide.
15. The method of claim 14 , wherein conditioning the gate oxide comprises hardening the gate oxide.
16. The method of claim 15 , wherein conditioning the gate oxide comprises exposing the gate oxide to a nitridizing ambient.
17. The method of claim 16 , wherein providing the gate material comprises depositing a material selected from a group of materials comprising titanium nitride and tungsten nitride.
18. The method of claim 14 , wherein conditioning the gate oxide comprises performing steam oxidation of the gate oxide.
19. A method for developing a semiconductor device, comprising:
cleaning a level of the semiconductor device;
furnishing a first oxide layer at the level;
cleaning the first oxide layer;
furnishing a second oxide layer over the level;
hardening the second oxide layer; and
furnishing an electrode on the second oxide layer.
20. The method of claim 19 , wherein cleaning the level comprises:
removing a residue from the level; and
neutralizing a contaminant within the level.
21. The method of claim 20 , wherein removing the residue comprises passivating the level.
22. The method of claim 21 , wherein furnishing the first oxide layer at the level comprises:
providing an ozone environment at the level; and
irradiating the ozone environment with ultraviolet radiation.
23. The method of claim 22 , wherein furnishing the first oxide layer at the level comprises performing rapid thermal oxidation at the level.
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US20090142903A1 (en) * | 2007-11-30 | 2009-06-04 | Taiwan Semiconductor Manufacturing Company, Ltd. | Chip on wafer bonder |
US8387674B2 (en) * | 2007-11-30 | 2013-03-05 | Taiwan Semiconductor Manufacturing Comany, Ltd. | Chip on wafer bonder |
US9093447B2 (en) | 2007-11-30 | 2015-07-28 | Taiwan Semiconductor Manufacturing Company, Ltd. | Chip on wafer bonder |
US20100009528A1 (en) * | 2008-07-08 | 2010-01-14 | Semiconductor Manufacturing International (Shanghai) Corporation | Method for Rapid Thermal Treatment Using High Energy Electromagnetic Radiation of a Semiconductor Substrate for Formation of Dielectric Films |
US7989363B2 (en) * | 2008-07-08 | 2011-08-02 | Semiconductor Manufacturing International (Shanghai) Corporation | Method for rapid thermal treatment using high energy electromagnetic radiation of a semiconductor substrate for formation of dielectric films |
US10453745B2 (en) | 2015-07-28 | 2019-10-22 | Samsung Electronics Co., Ltd. | Semiconductor device and method for fabricating the same |
Also Published As
Publication number | Publication date |
---|---|
US20070087506A1 (en) | 2007-04-19 |
WO1999039384A1 (en) | 1999-08-05 |
DE69939620D1 (en) | 2008-11-06 |
KR20010040515A (en) | 2001-05-15 |
US7135417B2 (en) | 2006-11-14 |
KR100415523B1 (en) | 2004-01-16 |
US20020119674A1 (en) | 2002-08-29 |
US6475927B1 (en) | 2002-11-05 |
ATE409356T1 (en) | 2008-10-15 |
EP1051744A1 (en) | 2000-11-15 |
US6589877B1 (en) | 2003-07-08 |
EP1051744B1 (en) | 2008-09-24 |
AU2462199A (en) | 1999-08-16 |
JP3360300B2 (en) | 2002-12-24 |
JP2002502126A (en) | 2002-01-22 |
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