US20130334536A1 - SINGLE-CRYSTAL REO BUFFER ON AMORPHOUS SiOx - Google Patents
SINGLE-CRYSTAL REO BUFFER ON AMORPHOUS SiOx Download PDFInfo
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- US20130334536A1 US20130334536A1 US13/771,514 US201313771514A US2013334536A1 US 20130334536 A1 US20130334536 A1 US 20130334536A1 US 201313771514 A US201313771514 A US 201313771514A US 2013334536 A1 US2013334536 A1 US 2013334536A1
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title abstract description 30
- 229910052814 silicon oxide Inorganic materials 0.000 title description 9
- 229910001404 rare earth metal oxide Inorganic materials 0.000 claims abstract description 58
- 239000000758 substrate Substances 0.000 claims abstract description 55
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 50
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 50
- 239000010703 silicon Substances 0.000 claims abstract description 49
- 229910021332 silicide Inorganic materials 0.000 claims abstract description 30
- FVBUAEGBCNSCDD-UHFFFAOYSA-N silicide(4-) Chemical compound [Si-4] FVBUAEGBCNSCDD-UHFFFAOYSA-N 0.000 claims abstract description 29
- 150000002910 rare earth metals Chemical class 0.000 claims abstract description 27
- 229910052761 rare earth metal Inorganic materials 0.000 claims abstract description 25
- 229910021417 amorphous silicon Inorganic materials 0.000 claims abstract description 18
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 18
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 18
- 239000001301 oxygen Substances 0.000 claims abstract description 18
- 230000002950 deficient Effects 0.000 claims abstract description 6
- 229910021419 crystalline silicon Inorganic materials 0.000 claims abstract description 4
- 239000000463 material Substances 0.000 claims description 26
- 239000004065 semiconductor Substances 0.000 claims description 24
- 229910052688 Gadolinium Inorganic materials 0.000 claims description 5
- 238000000137 annealing Methods 0.000 claims description 4
- UIWYJDYFSGRHKR-UHFFFAOYSA-N gadolinium atom Chemical compound [Gd] UIWYJDYFSGRHKR-UHFFFAOYSA-N 0.000 claims description 4
- 230000008021 deposition Effects 0.000 claims description 2
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 claims 1
- 229910052733 gallium Inorganic materials 0.000 claims 1
- 238000000034 method Methods 0.000 abstract description 31
- 238000000151 deposition Methods 0.000 abstract description 3
- 239000013078 crystal Substances 0.000 description 13
- 230000035882 stress Effects 0.000 description 13
- 230000015572 biosynthetic process Effects 0.000 description 10
- 230000003647 oxidation Effects 0.000 description 6
- 238000007254 oxidation reaction Methods 0.000 description 6
- 235000012431 wafers Nutrition 0.000 description 6
- 235000012239 silicon dioxide Nutrition 0.000 description 5
- 239000000377 silicon dioxide Substances 0.000 description 5
- 238000009792 diffusion process Methods 0.000 description 4
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 description 2
- 238000000231 atomic layer deposition Methods 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000004549 pulsed laser deposition Methods 0.000 description 2
- 230000008646 thermal stress Effects 0.000 description 2
- 229910021486 amorphous silicon dioxide Inorganic materials 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 229910052747 lanthanoid Inorganic materials 0.000 description 1
- 150000002602 lanthanoids Chemical class 0.000 description 1
- 238000002488 metal-organic chemical vapour deposition Methods 0.000 description 1
- 238000001451 molecular beam epitaxy Methods 0.000 description 1
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- -1 rare earth silicate Chemical class 0.000 description 1
- 238000011946 reduction process Methods 0.000 description 1
- 229910052706 scandium Inorganic materials 0.000 description 1
- SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 230000007847 structural defect Effects 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 description 1
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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
- H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
- H01L29/12—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
- H01L29/20—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed including, apart from doping materials or other impurities, only AIIIBV compounds
- H01L29/2003—Nitride compounds
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B1/00—Single-crystal growth directly from the solid state
- C30B1/02—Single-crystal growth directly from the solid state by thermal treatment, e.g. strain annealing
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
- C30B25/02—Epitaxial-layer growth
- C30B25/18—Epitaxial-layer growth characterised by the substrate
- C30B25/183—Epitaxial-layer growth characterised by the substrate being provided with a buffer layer, e.g. a lattice matching layer
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/16—Oxides
- C30B29/22—Complex oxides
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/40—AIIIBV compounds wherein A is B, Al, Ga, In or Tl and B is N, P, As, Sb or Bi
- C30B29/403—AIII-nitrides
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- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02104—Forming layers
- H01L21/02365—Forming inorganic semiconducting materials on a substrate
- H01L21/02367—Substrates
- H01L21/0237—Materials
- H01L21/02373—Group 14 semiconducting materials
- H01L21/02381—Silicon, silicon germanium, germanium
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- H01L21/02365—Forming inorganic semiconducting materials on a substrate
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- H01L21/02104—Forming layers
- H01L21/02365—Forming inorganic semiconducting materials on a substrate
- H01L21/02436—Intermediate layers between substrates and deposited layers
- H01L21/02439—Materials
- H01L21/02488—Insulating materials
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- H01L21/02104—Forming layers
- H01L21/02365—Forming inorganic semiconducting materials on a substrate
- H01L21/02436—Intermediate layers between substrates and deposited layers
- H01L21/02494—Structure
- H01L21/02496—Layer structure
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- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
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- H01L21/02365—Forming inorganic semiconducting materials on a substrate
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- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
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- H01L21/02365—Forming inorganic semiconducting materials on a substrate
- H01L21/02518—Deposited layers
- H01L21/02521—Materials
- H01L21/02538—Group 13/15 materials
- H01L21/0254—Nitrides
Definitions
- This invention relates in general to the formation of amorphous silicon oxide on silicon wafers between the substrate and a single-crystal rare earth oxide buffer for the growth of III-N semiconductor material.
- III-N materials are a desirable semiconductor material in many electronic and photonic applications.
- the III-N semiconductor material must be provided as a crystalline or single-crystal formation for the most efficient and useful bases for the fabrication of various electronic and photonic devices therein.
- the single-crystal III-N semiconductor material is most conveniently formed on single-crystal silicon wafers because of the extensive background and technology developed in the silicon semiconductor industry.
- the crystal lattice constant mismatch between silicon and a III-N material, such as GaN is 17% if grown c-axis on (111) oriented silicon.
- the thermal expansion difference between the III-N material, such as GaN is 56%. Both of these factors lead to residual stress and consequently to structural defects and mechanical damage (e.g. cracks) in the structure.
- a buffer layer between the silicon substrate and the III-N layer that could absorb stress would help solve the problem.
- Several copending patent applications have been filed in the U.S. in which rare earth oxides were grown on a silicon substrate to serve as a stress engineered buffer layer for the subsequent growth of III-N semiconductor material.
- Two of these copending U.S. patent applications are: Strain Compensated REO Buffer for III-N on Silicon, filed 21 Oct. 2011, bearing Ser. No. 13/278,952; and Nucleation of III-N on REO Templates, filed 20 Mar. 2012, bearing Ser. No. 61/613,289, both of which are included herein by reference.
- the rare earth oxide (REO) stress engineered buffer layers can reduce stress to a manageable level the stress can be conveniently reduced or substantially eliminated by including a layer of amorphous silicon oxide between the silicon substrate and the rare earth oxide buffer.
- Silicon oxide is amorphous material and has low viscosity at temperatures above 500° C. that results in stress relaxation, critical from the point of view of thermal stress during cooling down of GaN (III-N material) on silicon heterostructure.
- a major problem is that the formation of the amorphous silicon oxide layer must take place during the growth of the single-crystal REO buffer because growth of the REO on an amorphous silicon layer would lead to a polycrystalline REO buffer which is not suitable for single-crystal III-N growth.
- the method includes providing a crystalline silicon substrate and depositing a layer of rare earth metal on the silicon substrate in an oxygen deficient ambient at a temperature above approximately 500° C.
- the rare earth metal forms a layer of rare earth silicide on the substrate.
- a first layer of rare earth oxide is deposited on the layer of rare earth silicide with a structure and lattice constant substantially similar to the substrate.
- the structure is annealed in an oxygen ambience to transform the layer of rare earth silicide to a layer of amorphous silicon and an intermediate layer of rare earth oxide between the substrate and the first layer of rare earth oxide.
- a crystalline silicon substrate including a layer of rare earth metal deposited on the silicon substrate in an oxygen deficient ambient at a temperature above approximately 500° C.
- the rare earth metal forms a layer of rare earth silicide on the substrate.
- the layer of rare earth silicide is transformed by annealing into a layer of amorphous silicon and an intermediate layer of rare earth oxide positioned between the substrate and the first layer of rare earth oxide.
- a first layer of rare earth oxide is deposited on the layer of rare earth silicide with a structure and lattice constant substantially similar to the substrate.
- the preferred embodiment can further include a second layer of rare earth oxide with a structure and lattice constant substantially similar to the substrate.
- the second layer of rare earth oxide is positioned on the first layer of rare earth oxide to form a template for the subsequent deposition of a III-N semiconductor material.
- the preferred embodiment can further include a layer of III-N semiconductor material positioned on the second layer of rare earth oxide.
- the III-N semiconductor material has a structure and lattice constant substantially similar to the substrate.
- FIGS. 1-5 are simplified layer diagrams illustrating several sequential steps in a process of the formation of amorphous silicon oxide on silicon wafers between a substrate and a single-crystal rare earth oxide buffer for the growth of III-N semiconductor material in accordance with the present invention
- FIG. 6 illustrates a final step in which a III-N layer of semiconductor material is grown on a single-crystal rare earth oxide buffer
- FIG. 7 is a pictorial view of a REO layer grown on an amorphous silicon oxide on a silicon wafer, in accordance with the present invention.
- a silicon substrate 10 is illustrated which is, as understood in the art, a single-crystal material including silicon and may in some applications include other materials all of which are included in the general term “silicon” substrate. Also, the substrate may be for example a silicon wafer or some part thereof and is referred to herein by the general term “substrate”. While silicon substrate 10 is illustrated as having a ⁇ 111> crystal orientation, it will be understood, is not limited to any specific crystal orientation but could include ⁇ 111> silicon, ⁇ 110> silicon, ⁇ 100> silicon or any other orientation or variation known and used in the art.
- rare earth metal layer 12 a at the typical growth temperatures in an oxygen deficient ambience transforms to silicide (layer 12 b ) during reaction with silicon atoms in substrate 10 .
- layer 12 is designated with different letter designations (i.e. a, b, c) to show the changes that occur. It is important to keep layer 12 b very thin so that the following single-crystal growth steps can be performed.
- Thin silicide layer 12 b is epitaxially stabilized to silicon substrate 10 so that the crystalline structure is similar to silicon and has a similar lattice constant. As an example, some gadolinium silicides have a very close structure with silicon.
- REO layer 14 oxygen is introduced into the process and growth of a single-crystal rare earth oxide (REO) layer 14 is accomplished.
- silicide layer 12 b is very thin REO layer 14 has the atom stacking sequence from the silicon substrate, that is REO layer 14 and substrate 10 have a similar crystalline structure and a similar lattice constant.
- REO layer 14 is grown with a thickness from several nanometers (3 nm or less) to 10 nm or more, depending on the subsequent annealing time. Primarily, REO layer 14 is grown thin enough to promote oxygen diffusion through layer 14 .
- the structure is annealed preferably at approximately 900° C. in an oxygen ambience for oxide diffusion to the interface between silicide layer 12 b and REO layer 14 .
- Silicide layer 12 b is transformed to a rare earth silicate and ultimately to rare earth oxide because rare earth metals are strong reducers.
- excessive oxygen in cooperation with the silicon in silicide layer 12 b forms a layer 12 c of amorphous silicon oxide at the interface with substrate 10 .
- silicide layer 12 b is essentially reduced to a thin layer 12 c of amorphous silicon oxide and a thin layer of rare earth oxide (illustrated in FIG. 4 as part of layer 14 .
- the REO silicide layer 12 b includes gadolinium silicide as an example.
- the gadolinium silicide is reduced to a thin amorphous layer of SiO x and a thin Gd z Si y O x layer.
- the silicide layer 12 b is not stable because both Si and Gd have a very high affinity to oxygen.
- it is substantially easier to transform the silicide of layer 12 b to amorphous silicate and silicon dioxide than to transform the silicon of substrate 10 to silicon dioxide.
- the silicide transforms easier than the substrate silicon because oxidation of silicon is a diffusion limited process (i.e. the oxidation rate slows with the oxide thickness) and requires higher temperatures and oxygen pressures when compared to the present silicide reduction process.
- a thicker layer 16 of rare earth oxide (REO) is grown on REO layer 14 .
- REO layer 16 is preferably grown to a thickness in a range from less than approximately 50 nm to greater than approximately 500 nm so as to serve as a template for the subsequent growth of a III-N semiconductor layer.
- REO templates are disclosed in more detail in the copending patent applications described above and included herein by reference.
- FIG. 6 a final step in the process of the growth of III-N semiconductor material on a silicon substrate is illustrated. It will of course be understood that this is simply described as a final step because a layer 20 of III-N semiconductor material (in this example GaN) is grown on the REO template 14 / 16 . Once layer 20 is grown additional steps in a process of fabricating a semiconductor product (e.g. photonic device, sensor, etc.) can be performed. As explained above, layer 12 c of amorphous silicon oxide has low viscosity at temperatures above 500° C. that results in stress relaxation, which is critical in point of view of thermal stress during cooling down of III-N on Si heterostructure.
- a semiconductor product e.g. photonic device, sensor, etc.
- the silicide of layer 12 b is transformed to amorphous silicate and silicon dioxide rather than attempting to transform the silicon of substrate 10 to silicon dioxide as in prior art methods.
- the present novel method is relatively easy to perform and results in a substantially uniform layer of amorphous silicon oxide that is sufficiently thick to provide the desired stress relief during the cool down of a III-N semiconductor layer of material deposited on the REO template.
Abstract
A method of forming a layer of amorphous silicon oxide positioned between a layer of rare earth oxide and a silicon substrate. The method includes providing a crystalline silicon substrate and depositing a layer of rare earth metal on the silicon substrate in an oxygen deficient ambient at a temperature above approximately 500° C. The rare earth metal forms a layer of rare earth silicide on the substrate. A first layer of rare earth oxide is deposited on the layer of rare earth silicide with a structure and lattice constant substantially similar to the substrate. The structure is annealed in an oxygen ambience to transform the layer of rare earth silicide to a layer of amorphous silicon and an intermediate layer of rare earth oxide between the substrate and the first layer of rare earth oxide.
Description
- This invention relates in general to the formation of amorphous silicon oxide on silicon wafers between the substrate and a single-crystal rare earth oxide buffer for the growth of III-N semiconductor material.
- It has been found that III-N materials are a desirable semiconductor material in many electronic and photonic applications. As understood in the art, the III-N semiconductor material must be provided as a crystalline or single-crystal formation for the most efficient and useful bases for the fabrication of various electronic and photonic devices therein. Further, the single-crystal III-N semiconductor material is most conveniently formed on single-crystal silicon wafers because of the extensive background and technology developed in the silicon semiconductor industry. However, the crystal lattice constant mismatch between silicon and a III-N material, such as GaN, is 17% if grown c-axis on (111) oriented silicon. Also, the thermal expansion difference between the III-N material, such as GaN, is 56%. Both of these factors lead to residual stress and consequently to structural defects and mechanical damage (e.g. cracks) in the structure.
- A buffer layer between the silicon substrate and the III-N layer that could absorb stress would help solve the problem. Several copending patent applications have been filed in the U.S. in which rare earth oxides were grown on a silicon substrate to serve as a stress engineered buffer layer for the subsequent growth of III-N semiconductor material. Two of these copending U.S. patent applications are: Strain Compensated REO Buffer for III-N on Silicon, filed 21 Oct. 2011, bearing Ser. No. 13/278,952; and Nucleation of III-N on REO Templates, filed 20 Mar. 2012, bearing Ser. No. 61/613,289, both of which are included herein by reference.
- While the rare earth oxide (REO) stress engineered buffer layers can reduce stress to a manageable level the stress can be conveniently reduced or substantially eliminated by including a layer of amorphous silicon oxide between the silicon substrate and the rare earth oxide buffer. Silicon oxide is amorphous material and has low viscosity at temperatures above 500° C. that results in stress relaxation, critical from the point of view of thermal stress during cooling down of GaN (III-N material) on silicon heterostructure. A major problem is that the formation of the amorphous silicon oxide layer must take place during the growth of the single-crystal REO buffer because growth of the REO on an amorphous silicon layer would lead to a polycrystalline REO buffer which is not suitable for single-crystal III-N growth.
- There are potentially several ways to form the silicon oxide interface layer all of which have severe drawbacks. In a first method, an atmosphere of excess oxygen can be provided during the REO growth. Some problems with this method are that high oxygen pressure is needed during the process which causes the lifetime of the MBE components in the chamber to deteriorate and the SiOx layer is not thick enough to adequately perform the stress relief. In a second method, the REO is grown and the structure is subsequently annealed in oxygen atmosphere. A method of this type is described in U.S. Pat. No. 7,785,706, entitled “Semiconductor Wafer and Process for its Production”, issued Aug. 31, 2010 and U.S. Pub. 2010/0221869 of the same title. One problem with this type of method is that the formation of the interface can be hard to control, the oxidation needs long time, temperature and/or high oxygen pressure because oxidation of silicon is diffusion limited process, which means that oxidation becomes slower with increasing of thickness of the silicon dioxide layer.
- It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
- Accordingly, it is an object of the present invention to provide new and improved methods of forming a layer of amorphous silicon between a REO buffer and a silicon substrate.
- It is another object of the present invention to provide new and improved methods of forming a layer of amorphous silicon dioxide between a REO buffer and a silicon substrate that is sufficiently thick to adequately perform stress relief that is easy and reliable to control.
- It is another object of the present invention to provide a new and improved III-N semiconductor layer on a silicon substrate including a layer of amorphous silicon between a REO buffer and the substrate.
- Briefly, the desired objects and aspects of the instant invention are achieved in accordance with a preferred method of forming a layer of amorphous silicon oxide positioned between a layer of rare earth oxide and a silicon substrate. The method includes providing a crystalline silicon substrate and depositing a layer of rare earth metal on the silicon substrate in an oxygen deficient ambient at a temperature above approximately 500° C. The rare earth metal forms a layer of rare earth silicide on the substrate. A first layer of rare earth oxide is deposited on the layer of rare earth silicide with a structure and lattice constant substantially similar to the substrate. The structure is annealed in an oxygen ambience to transform the layer of rare earth silicide to a layer of amorphous silicon and an intermediate layer of rare earth oxide between the substrate and the first layer of rare earth oxide.
- The desired objects and aspects of the instant invention are further realized in accordance with a preferred embodiment of a crystalline silicon substrate including a layer of rare earth metal deposited on the silicon substrate in an oxygen deficient ambient at a temperature above approximately 500° C. The rare earth metal forms a layer of rare earth silicide on the substrate. The layer of rare earth silicide is transformed by annealing into a layer of amorphous silicon and an intermediate layer of rare earth oxide positioned between the substrate and the first layer of rare earth oxide. A first layer of rare earth oxide is deposited on the layer of rare earth silicide with a structure and lattice constant substantially similar to the substrate.
- The preferred embodiment can further include a second layer of rare earth oxide with a structure and lattice constant substantially similar to the substrate. The second layer of rare earth oxide is positioned on the first layer of rare earth oxide to form a template for the subsequent deposition of a III-N semiconductor material. The preferred embodiment can further include a layer of III-N semiconductor material positioned on the second layer of rare earth oxide. The III-N semiconductor material has a structure and lattice constant substantially similar to the substrate.
- The foregoing and further and more specific objects and advantages of the instant invention will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment thereof taken in conjunction with the drawings, in which:
-
FIGS. 1-5 are simplified layer diagrams illustrating several sequential steps in a process of the formation of amorphous silicon oxide on silicon wafers between a substrate and a single-crystal rare earth oxide buffer for the growth of III-N semiconductor material in accordance with the present invention; -
FIG. 6 illustrates a final step in which a III-N layer of semiconductor material is grown on a single-crystal rare earth oxide buffer; and -
FIG. 7 is a pictorial view of a REO layer grown on an amorphous silicon oxide on a silicon wafer, in accordance with the present invention. - In view of the need for stress relaxation in a process of forming III-N semiconductor layers on silicon substrates some effort and study has gone into the formation of an amorphous layer of silicon oxide (SiOx) between the silicon substrate and the III-N layer or layers. However, to date various proposed methods for the formation of the amorphous layer all have several drawbacks or problems that substantially reduce the efficiency or effectiveness of the process and results. Accordingly, a new method for the formation of an amorphous layer of silicon oxide (SiOx) between the silicon substrate and the III-N layer or layers is herein disclosed. The new method is greatly improved and results in the formation of an amorphous layer that can be accurately controlled and which substantially absorbs or reduces stress between the silicon substrate and the III-N semiconductor layer.
- Turning now to
FIG. 1 , asilicon substrate 10 is illustrated which is, as understood in the art, a single-crystal material including silicon and may in some applications include other materials all of which are included in the general term “silicon” substrate. Also, the substrate may be for example a silicon wafer or some part thereof and is referred to herein by the general term “substrate”. Whilesilicon substrate 10 is illustrated as having a <111> crystal orientation, it will be understood, is not limited to any specific crystal orientation but could include <111> silicon, <110> silicon, <100> silicon or any other orientation or variation known and used in the art. - A very
thin layer 12 a of rare earth metal is deposited on the surface ofsilicon substrate 10. Rareearth metal layer 12 a is grown directly on the surface ofsubstrate 10 using any of the well-known growth methods, such as MBE, MOCVD, PLD (pulsed laser deposition), sputtering, ALD (atomic layer deposition), or any other known growth method for thin films. Throughout this disclosure whenever rare earth materials are mentioned it will be understood that “rare earth” materials are generally defined as any of the lanthanides as well as scandium and yttrium.Metal layer 12 a is grown 1-2 monolayers thick which is about 0.5 nm to about 1.0 nm thick. The typical growth temperature for the rare earth metal is above approximately 550° C. - As illustrated in
FIG. 2 , rareearth metal layer 12 a at the typical growth temperatures in an oxygen deficient ambience transforms to silicide (layer 12 b) during reaction with silicon atoms insubstrate 10. For convenience of understanding layer 12 is designated with different letter designations (i.e. a, b, c) to show the changes that occur. It is important to keeplayer 12 b very thin so that the following single-crystal growth steps can be performed.Thin silicide layer 12 b is epitaxially stabilized tosilicon substrate 10 so that the crystalline structure is similar to silicon and has a similar lattice constant. As an example, some gadolinium silicides have a very close structure with silicon. By starting growth ofmetal layer 12 a with a lower oxygen pressure (oxide deficient condition) initial oxidation of the silicide is prevented which leads to the formation of athicker silicide layer 12 b. - Referring to
FIG. 3 , it will be understood that for convenience and efficiency of procedure the growth process fromFIG. 2 is continued (i.e. in situ). In the step illustrated inFIG. 3 , oxygen is introduced into the process and growth of a single-crystal rare earth oxide (REO)layer 14 is accomplished. Becausesilicide layer 12 b is verythin REO layer 14 has the atom stacking sequence from the silicon substrate, that isREO layer 14 andsubstrate 10 have a similar crystalline structure and a similar lattice constant.REO layer 14 is grown with a thickness from several nanometers (3 nm or less) to 10 nm or more, depending on the subsequent annealing time. Primarily,REO layer 14 is grown thin enough to promote oxygen diffusion throughlayer 14. - Referring to
FIG. 4 , after the growth ofREO layer 14 the structure is annealed preferably at approximately 900° C. in an oxygen ambience for oxide diffusion to the interface betweensilicide layer 12 b andREO layer 14.Silicide layer 12 b is transformed to a rare earth silicate and ultimately to rare earth oxide because rare earth metals are strong reducers. During this process excessive oxygen in cooperation with the silicon insilicide layer 12 b forms alayer 12 c of amorphous silicon oxide at the interface withsubstrate 10. Thus,silicide layer 12 b is essentially reduced to athin layer 12 c of amorphous silicon oxide and a thin layer of rare earth oxide (illustrated inFIG. 4 as part oflayer 14. - Referring additionally to
FIG. 7 , in the pictorial view theREO silicide layer 12 b includes gadolinium silicide as an example. As can be seen from the pictorial, after the annealing layer described above, the gadolinium silicide is reduced to a thin amorphous layer of SiOx and a thin GdzSiyOx layer. Thesilicide layer 12 b is not stable because both Si and Gd have a very high affinity to oxygen. Thus, it is substantially easier to transform the silicide oflayer 12 b to amorphous silicate and silicon dioxide than to transform the silicon ofsubstrate 10 to silicon dioxide. The silicide transforms easier than the substrate silicon because oxidation of silicon is a diffusion limited process (i.e. the oxidation rate slows with the oxide thickness) and requires higher temperatures and oxygen pressures when compared to the present silicide reduction process. - In a subsequent step illustrated in
FIG. 5 , athicker layer 16 of rare earth oxide (REO) is grown onREO layer 14.REO layer 16 is preferably grown to a thickness in a range from less than approximately 50 nm to greater than approximately 500 nm so as to serve as a template for the subsequent growth of a III-N semiconductor layer. REO templates are disclosed in more detail in the copending patent applications described above and included herein by reference. - Turning to
FIG. 6 a final step in the process of the growth of III-N semiconductor material on a silicon substrate is illustrated. It will of course be understood that this is simply described as a final step because alayer 20 of III-N semiconductor material (in this example GaN) is grown on theREO template 14/16. Oncelayer 20 is grown additional steps in a process of fabricating a semiconductor product (e.g. photonic device, sensor, etc.) can be performed. As explained above,layer 12 c of amorphous silicon oxide has low viscosity at temperatures above 500° C. that results in stress relaxation, which is critical in point of view of thermal stress during cooling down of III-N on Si heterostructure. - Thus, the silicide of
layer 12 b is transformed to amorphous silicate and silicon dioxide rather than attempting to transform the silicon ofsubstrate 10 to silicon dioxide as in prior art methods. The present novel method is relatively easy to perform and results in a substantially uniform layer of amorphous silicon oxide that is sufficiently thick to provide the desired stress relief during the cool down of a III-N semiconductor layer of material deposited on the REO template. - Various changes and modifications to the embodiments herein chosen for purposes of illustration will readily occur to those skilled in the art. To the extent that such modifications and variations do not depart from the spirit of the invention, they are intended to be included within the scope thereof which is assessed only by a fair interpretation of the following claims.
Claims (6)
1-9. (canceled)
10. A III-N on silicon wafer comprising:
a crystalline silicon substrate;
a layer of rare earth metal deposited on the silicon substrate in an oxygen deficient ambient at a temperature above approximately 500° C., the rare earth metal forming a layer of rare earth silicide on the substrate, the layer of rare earth silicide being transformed by annealing into a layer of amorphous silicon and an intermediate layer of rare earth oxide positioned between the substrate and the first layer of rare earth oxide; and
a first layer of rare earth oxide deposited on the layer of rare earth silicide with a structure and lattice constant substantially similar to the substrate.
11. A III-N on silicon wafer as claimed in claim 10 further including a second layer of rare earth oxide with a structure and lattice constant substantially similar to the substrate, the second layer of rare earth oxide positioned on the first layer of rare earth oxide to form a template for the subsequent deposition of a III-N semiconductor material.
12. A III-N on silicon wafer as claimed in claim 11 further including a layer of III-N semiconductor material positioned on the second layer of rare earth oxide, the III-N semiconductor material having a structure and lattice constant substantially similar to the substrate.
13. A III-N on silicon wafer as claimed in claim 12 wherein the second layer of rare earth oxide includes gadolinium.
14. A III-N on silicon wafer as claimed in claim 13 wherein the layer of III-N semiconductor material includes gallium.
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US8796121B1 (en) * | 2013-11-19 | 2014-08-05 | Translucent, Inc. | Stress mitigating amorphous SiO2 interlayer |
CN109690737A (en) * | 2016-04-13 | 2019-04-26 | Iqe公开有限公司 | The III group semiconductor epitaxial formed on silicon via monocrystalline REN and REO buffer layer |
US10573686B2 (en) * | 2016-06-19 | 2020-02-25 | Iqe Plc | Epitaxial AIN/cREO structure for RF filter applications |
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US20120104567A1 (en) * | 2010-11-01 | 2012-05-03 | Andrew Clark | IIIOxNy ON REO/Si |
US9496132B2 (en) * | 2012-03-20 | 2016-11-15 | Translucent, Inc. | Nucleation of III-N on REO templates |
US8501635B1 (en) * | 2012-09-29 | 2013-08-06 | Translucent, Inc. | Modification of REO by subsequent III-N EPI process |
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US8796121B1 (en) * | 2013-11-19 | 2014-08-05 | Translucent, Inc. | Stress mitigating amorphous SiO2 interlayer |
CN109690737A (en) * | 2016-04-13 | 2019-04-26 | Iqe公开有限公司 | The III group semiconductor epitaxial formed on silicon via monocrystalline REN and REO buffer layer |
US10573686B2 (en) * | 2016-06-19 | 2020-02-25 | Iqe Plc | Epitaxial AIN/cREO structure for RF filter applications |
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