WO1992022689A1 - Process for making large-area single crystal diamond films - Google Patents

Process for making large-area single crystal diamond films Download PDF

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Publication number
WO1992022689A1
WO1992022689A1 PCT/US1992/005149 US9205149W WO9222689A1 WO 1992022689 A1 WO1992022689 A1 WO 1992022689A1 US 9205149 W US9205149 W US 9205149W WO 9222689 A1 WO9222689 A1 WO 9222689A1
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Prior art keywords
diamond
substrate
invention recited
layer
pits
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PCT/US1992/005149
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French (fr)
Inventor
Roger W. Pryor
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The Board Of Governors Of Wayne State University
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Publication of WO1992022689A1 publication Critical patent/WO1992022689A1/en

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    • CCHEMISTRY; METALLURGY
    • C30CRYSTAL GROWTH
    • C30BSINGLE-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
    • C30B25/00Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
    • C30B25/02Epitaxial-layer growth
    • C30B25/18Epitaxial-layer growth characterised by the substrate
    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/02Pretreatment of the material to be coated
    • C23C16/0227Pretreatment of the material to be coated by cleaning or etching
    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/02Pretreatment of the material to be coated
    • C23C16/0272Deposition of sub-layers, e.g. to promote the adhesion of the main coating
    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/22Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
    • C23C16/26Deposition of carbon only
    • C23C16/27Diamond only
    • CCHEMISTRY; METALLURGY
    • C30CRYSTAL GROWTH
    • C30BSINGLE-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
    • C30B25/00Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
    • C30B25/02Epitaxial-layer growth
    • C30B25/10Heating of the reaction chamber or the substrate
    • C30B25/105Heating of the reaction chamber or the substrate by irradiation or electric discharge
    • CCHEMISTRY; METALLURGY
    • C30CRYSTAL GROWTH
    • C30BSINGLE-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
    • C30B29/00Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/02Elements
    • C30B29/04Diamond

Definitions

  • the present invention relates generally to techniques fo forming synthetic diamond films. More specifically, the presen invention relates to the fabrication of large-area, mosaic homoepitaxia diamond films.
  • Synthetic diamond films have received widespread interest i the field of microelectronics. It is known that diamond films can b formed from carbon gases such as methane and the like by a number o deposition techniques, including RF, microwave, combustion and therma deposition. Each deposition technique is unique in terms of th deposition apparatus, operating parameters, reproducibility and purit of the resultant diamond film.
  • homoepitaxial diamond films ca be produced by chemical vapor deposition, to date only small-area, high-purity films have been successfully fabricated. Attempts t produce large-area, high-purity diamond films have generally resulted i inferior films which are unsuitable for use in microelectronics wher the presence of even minor defects and trace impurities can interfer with device operation.
  • the development of high-quality diamon films for use in high-speed, high-power semiconductor devices at reasonable cost, requires the successful fabrication of large-area, single crystal high-purity mosaic homoepitaxial diamond films.
  • One recent approach by others to the problem of fabricating large-area diamond sheets involves the u ⁇ e of acetone through which gas is bubbled to form a mixture of gases which includes the acetone as a carDon source gas.
  • Diamond is deposited in this manner on a silico substrate on which an array of diamond seed crystals is formed by firs etching an array of pits in the silicon and then placing diamond grit i the pits.
  • a thermal CVD plasma is generated from the gas mixture Nucleated by the diamond grit, synthetic diamond is grown at eac nucleation site in the array, extending vertically and laterally fro each seed crystal. As diamond growth continues, the diamonds merge.
  • the present invention solves the problems of the prior art and provides a unique approach for the fabrication of large-area, single crystal mosaic diamond sheets for microelectronic and mechanical applications.
  • the present invention provides a method of forming a large-area homoepitaxial synthetic mosaic diamond film on a substrate by creating an array of pits on the surface of a substrate; placing a diamond seed crystal in each of the pits; and growing single crystal homoepitaxial synthetic diamond nucleated by the diamond seed crystals on the substrate through formation of a plasma of a controlled feedstock gas mixture which contains CH ⁇ , H and 0 2 - A single unitary mosaic sheet of diamond is formed as the individual deposit sites merge.
  • the diamond seed crystals are preferably oriented in the pits such that the (100) plane of each seed crystal is substantially co-planar with the surface of the substrate to promote single crystal diamond growth.
  • the seed crystal may extend above the surface of the substrate as ⁇ hown in somewhat exaggerated form in the drawings (none of which are t scale) or be recessed below the surface somewhat. Growth o homoepitaxial synthetic diamond is nucleated in this manner by each see crystal. Growth continues laterally and vertically at the site of eac seed crystal such that the individual growth sites combine or merge wit one another to produce a large-area, single crystal mosaic diamond shee on the substrate. The substrate may then be removed by conventiona means. In a most preferred embodiment, the plasma of feedstock gases is generated by microwave CVD.
  • the present invention provides a method for fabricating large-area mosaic sheets of single crystal homoepitaxial synthetic diamond by forming an array of pits in the surface of a substrate; (coating the substrate to form a layer of non-diamond nucleating material on the principal surface of the substrate, including in the pits) placing a diamond seed crystal in each of the pits; and growing single crystal diamond nucleated by the diamond seed crystals on the substrate as a single unitary mosaic sheet.
  • the layer of non-diamond nucleating material is preferably an oxide layer which inhibits the growth of polycrystalline diamond on the substrate.
  • Figure 1 illustrates diagrammatically in cross-section a side view of a silicon wafer having an array of pits in accordance with the present invention.
  • Figure 2 illustrates - diagrammatically a plan view of the silicon wafer of Figure 1 in which a diamond seed crystal is shown in each pit.
  • Figure 3 illustrates diagrammatically in cross-section of the silicon wafer substrate of Figure 2 with partial growth of homoepitaxial synthetic diamond at each seed crystal site.
  • Figure h illustrates diagrammatically in cross-section a side view of the silicon wafer substrate of Figure 3 after formation of a single crystal mosaic diamond film.
  • Figure 5 illustrates diagrammatically in cross-section a side view of a silicon wafer having an array of tetrahedral pits in accordance with the present invention.
  • Figure 6 illustrates diagrammatically a plan view of the silicon wafer of Figure 5 in which a diamond seed crystal is shown in each pit.
  • Figure 7 illustrates diagrammatically in cross-section a side view of the silicon wafer substrate of Figure 6 following growth of an oxide layer.
  • Figure 8 illustrates diagrammatically in cross-section a side view of the silicon wafer substrate of Figure 7 after formation of a single crystal mosaic diamond film.
  • Figure 9 shows the Raman spectrum of a diamond sample made in accordance with the present invention.
  • substrate 20 i shown which may comprise a silicon wafer, or other substrate "such as metal substrate coated with silicon dioxide or another suitabl non-nucleating coating, upon which a large-area mosaic diamond shee will be formed.
  • a plurality of pits, preferably tetrahedral pits 22 are etched or otherwise formed in the surface of substrate 20 Tetrahedral pits 22 are preferably formed by patterned etching substrat 20 although other techniques of forming pits 22 may be suitable.
  • a layer of oxide is formed thermally o principal surface 23 which comprises the (100) plane of silicon wafe substrate 20.
  • the SiO layer is patterned to form a mask that allows tetrahedral pits 22 to b etched into principal substrate 23.
  • a preferred etchant is an aqueou solution of (CH 3 ) z ,N0H (10% by weight) at 90* C.
  • the (100) planes of silico wafer substrate 20 are etched preferentially by these etchant approximately 1000 times faster than the (111) planes.
  • the mask is substantially undercut by the action of the etchant and is then removed with HF. In this manner, principal surface 23 consists essentially of intersecting (111) planes.
  • a square array of tetrahedral pits be formed such as that shown in Figure 2 of the drawing ⁇ so that even, symmetrical growth of synthetic diamond from each seed crystal site occurs.
  • Other arrays may also be suitable.
  • Regularly spaced square openings 90 microns by 90 microns x 50 microns on 100 micron centers are particularly preferred, but the size of the pits is essentially dictated by the size of the seed crystals utilized.
  • Diamond seed crystals 24 are selected to be placed in tetrahedral pits 22.
  • Diamond seed crystals 24 should be high-quality diamond crystals having a geometry such that one seed " crystal substantially fills each tetrahedral pit 22.
  • diamond seed crystals or grit approximately 75 microns to about 100 microns in size (largest dimension of the crystal) faceted on (111) planes are particularly preferred.
  • Suitable seed crystals may be obtained from a number of commercial suppliers such as General Electric Corporation or De Beers and are manufactured by high-pressure techniques.
  • seed crystals 24 In order to remove any foreign matter on the surface of seed crystals 24 they are washed, preferably in a solution of aN03 followed by a concentrated bath of HF and HNO3. Following a deionized H 2 0 rinse the seed crystals are then dried.
  • seed crystals 24 are placed in position in pits 22, the most preferred technique is through the use of a slurry.
  • An excess of diamond seed crystals is added to a 0.01% by weight solution of a novolac polymer in an organic solvent.
  • Substrate 20 is placed in a bath of the diamond slurry whereupon a single seed crystal 24 settles into each tetrahedral pit 22; this process may be enhanced by gentle agitation.
  • the slurry is then drained off and any seed crystals on substrate 20 other than those in pits 22 are removed.
  • Substrate 20 is then dried by heating.
  • the polymer serves to attach diamond seed crystals 24 in tetrahedral pits 22.
  • pits 24 Due to variations in the sizes of pits 22 and of diamond seed crystals 24, as well as the nature of the slurry technique used to ⁇ eposit diamond seed crystals in pits 22 some pits may be vacant and others may contain two seed crystals, however these occurrences are relatively insignif cant where the various parameters are closely controlled. Most preferably, at least 90% of pits 24 should contain only a single properly oriented seed crystal 24, i.e. the (100) face is substantially co-planar with principle surface 23. In other "words, in the plan view shown in Figure 2 of the drawings diamond seed crystals 24 are shown with the (100) crystalline plane face up. Although this face should be substantially co-planar with principal surface 26, minor deviations where the grit is slightly recessed in pit 22 or extends above the plane of principal surface 23 may be acceptable in some circumstances.
  • Substrate 20 having diamond grit 24 positioned in the array of tetrahedral pits 22 is then placed in a deposition chamber by which plasma enhanced deposition of synthetic diamond is achieved in the following manner.
  • substrate 20 having diamond grit 24 in the array of tetrahedral pits 22 is placed on a susceptor in the chamber of a microwave chemical vapor deposition apparatus (not shown).
  • a hydrogen etch is performed in the conventional manner which removes native oxide and other contaminants from principal surface 23 of substrate 20 and from the exposed surfaces of diamond grit 24.
  • 100% hydrogen at 45 torr, 900 ⁇ C, 900 SSCM at a microwave power level of 1.0 kw is preferably utilized, although values - which are near the stated values are also suitable.
  • the hydrogen etch is typically carried out for about 15 to about 60 minutes.
  • principal surface 23 may be further conditioned by an oxygen treatment which utilizes a mixture of gases comprising by volume from about 15-25% oxygen, from about 60-75% argon and from about 0.1-10% hydrogen.
  • the flow of gases during thi step will typically be within the following ranges: 0 2 about 15-2
  • SSCM most preferably about 20SSCM, argon about 60-75 SSCM, mos preferably about 68 SSCM; and hydrogen about 0.1 to about 10 SSCM, mos preferably about 0.1 SSCM.
  • the oxygen treatment is in the nature of passivation of principal surface 23 to inhibit the nucleation and growt of polycrystalline diamond at points other than at seed crystals 24.
  • the oxygen treate ent is performed in the deposition chamber at abou
  • a mixture of gases is flowed into the chamber for microwave assisted chemical vapor deposition at a microwave power level of from about 1.0 to 2.0 kw, or preferably 1.5 kw, and at a temperature of from about 700-1000" C, preferably 900 ⁇ C.
  • the concentration and the proportions of the feedstock gases are relatively critical.
  • the most preferred technique for the deposition of synthetic diamond from the feedstock gases in the present invention is plasma-enhanced chemical vapor deposition and most preferably microwave-enhanced plasma CVD. It has been found that a frequency of 2.45 GH Z is particularly useful for all steps in the present invention. Other plasma-enhanced CVD techniques may also be suitable for use herein.
  • Diamond growth is nucleated at each seed crystal 24 and grows both vertically and laterally as shown in Figure 3 of the drawings. Under the preferred conditions set forth herein, diamond growth which has been estimated at about 4 microns to 10 microns/hr has been observed.
  • the individual diamond deposits 26 begin to merge to form a mosaic diamond sheet which is equivalent to a single synthetic diamond sheet for many purposes.
  • a silicon wafer having a diameter of about 1.0 cm utilizing a square array of about 10,000 tetrahedral pits, it has been found that in approximately 60-70 hours a large-area homoepitaxial synthetic mosaic diamond sheet covering the majority of principal surface 23 is formed.
  • substrate 20 may then be removed by etching, machining, or other means.
  • the mosaic diamond sheet 28 which is formed by the method of the present invention has minimal dislocations at the boundaries of the merged deposits and minimal polycrystalline inclusions.
  • Mosaic diamon sheet 28 is essentially a single crystal sheet which is useful in man applications, including as a material for use in microelectronic devices.
  • substrate 40 is prepared in the previously described manner to provide an array of tetrahedral pits 42 in which diamond seed crystals 44 are positioned at principal surface 43, as shown in Figure 6.
  • the method of preparation and materials used are those described in connection with the previous embodiment.
  • Substrate 40 having an array of diamond seed crystals 44 is then placed in a deposition chamber for plasma enhanced chemical vapor deposition of synthetic diamond.
  • substrate 40 is placed on a susceptor in the chamber of a plasma-enhanced chemical vapor deposition apparatus, which again is preferably a microwave CVD apparatus.
  • Oxide layer 45 serves to inhibit the formation of diamond growth at locations on substrate 40 other than at diamond seed crystals 44. In other words, as previously explained during the deposition of synthetic diamond, sites directly on substrate 40 between seed crystal 44 may nucleate diamond growth. This type of diamond growth proceeds in random planes forming polycrystalline regions which appear as polycrystalline inclusions in the finished mosaic diamond sheet and which interfere with the desired properties of the final diamond product. Thus, the purpose of oxide layer 45 is to inhibit thi unwanted growth. Oxide layer 45 is preferably from about 100 angstrom to about 300 angstroms thick and more preferably about 200 angstrom thick.
  • substrate 40 is oxidized, or coated in some other manner with a layer of material which inhibits polycrystalline diamond growt prior to the insertion of the seed crystals.
  • th inner surfaces of the pits are also oxidized or coated as shown i Figures 3, 4, 7 and 8.
  • a hydrogen etch is again performed as described above whic removes contaminants from diamond grit 44 and which modifies oxide laye 45 in a manner not fully understood.
  • An oxygen treatment again in th manner described above, is then performed which generally re-establishe the integrity of oxide layer 45.
  • mixture of feedstock gases is then flowed into the chamber in the sam manner and proportions as described in the previous embodiment fo diamond deposition vapor and diamond is grown by CVD.
  • Substrate 40 including oxide layer 45, ma then be removed using conventional techniques.
  • an intermittent diamond growth/oxygen treatment process is very effective in reducing polycrystalline growth. Accordingly, in this embodiment, following a short interval of several hours of diamond growth, th deposition of diamond is interrupted and the oxygen treatment describe above is instituted for about 15 to 60 minutes, preferably about 3 minutes. Diamond growth is rein ⁇ tituted for another few hours followe by another short period of oxygen treatment. Diamond growth and oxyge treatment are continuously cycled in this manner throughout th formation of the diamond mosaic sheet. It is believed that thi technique continuously maintains the integrity of the passivation laye and removes any contaminants from diamond surfaces.

Abstract

A method for fabricating large-area mosaic homoepitaxial synthetic diamond sheets. An array of tetrahedral pits (22) is formed in the surface of a substrate (20). A diamond seed crystal is placed in each pit (22). The substrate is placed in the chamber of a plasma-enhanced chemical vapor deposition apparatus wherein diamond is grown on the substrate surface (20). Diamond growth is nucleated by the diamond crystals in the tetrahedral pits (22). A passivating layer of oxide may be formed on the substrate prior to the deposition of synthetic diamond which inhibits the growth of polycrystalline diamond on the substrate (20) between the seed crystals (24). Growth of diamond at each seed crystal (24) occurs and the individual deposits merge to form a high-quality, mosaic diamond sheet.

Description

PROCESS FOR MAKING LARGE-AREA STNGLE CRYSTAL DIAMOND FILMS
ΓΈCTNICAJ. FIEU
The present invention relates generally to techniques fo forming synthetic diamond films. More specifically, the presen invention relates to the fabrication of large-area, mosaic homoepitaxia diamond films.
BACKGROUND OF THE INVENTION
Synthetic diamond films have received widespread interest i the field of microelectronics. It is known that diamond films can b formed from carbon gases such as methane and the like by a number o deposition techniques, including RF, microwave, combustion and therma deposition. Each deposition technique is unique in terms of th deposition apparatus, operating parameters, reproducibility and purit of the resultant diamond film. Although homoepitaxial diamond films ca be produced by chemical vapor deposition, to date only small-area, high-purity films have been successfully fabricated. Attempts t produce large-area, high-purity diamond films have generally resulted i inferior films which are unsuitable for use in microelectronics wher the presence of even minor defects and trace impurities can interfer with device operation. Thus, the development of high-quality diamon films for use in high-speed, high-power semiconductor devices, at reasonable cost, requires the successful fabrication of large-area, single crystal high-purity mosaic homoepitaxial diamond films.
One recent approach by others to the problem of fabricating large-area diamond sheets involves the uβe of acetone through which gas is bubbled to form a mixture of gases which includes the acetone as a carDon source gas. Diamond is deposited in this manner on a silico substrate on which an array of diamond seed crystals is formed by firs etching an array of pits in the silicon and then placing diamond grit i the pits. A thermal CVD plasma is generated from the gas mixture Nucleated by the diamond grit, synthetic diamond is grown at eac nucleation site in the array, extending vertically and laterally fro each seed crystal. As diamond growth continues, the diamonds merge. Difficulties with this technique, however, have been encountered, including the formation of polycrystalline inclusions in the diamond sheet as well as a general inability to reliably produce large-area diamond sheets. The present invention solves the problems of the prior art and provides a unique approach for the fabrication of large-area, single crystal mosaic diamond sheets for microelectronic and mechanical applications.
SIMIARY OF THE INVENTION
In one aspect, the present invention provides a method of forming a large-area homoepitaxial synthetic mosaic diamond film on a substrate by creating an array of pits on the surface of a substrate; placing a diamond seed crystal in each of the pits; and growing single crystal homoepitaxial synthetic diamond nucleated by the diamond seed crystals on the substrate through formation of a plasma of a controlled feedstock gas mixture which contains CH^, H and 02- A single unitary mosaic sheet of diamond is formed as the individual deposit sites merge. The diamond seed crystals are preferably oriented in the pits such that the (100) plane of each seed crystal is substantially co-planar with the surface of the substrate to promote single crystal diamond growth. By substantially co-planar, it is to be understood that the seed crystal may extend above the surface of the substrate as εhown in somewhat exaggerated form in the drawings (none of which are t scale) or be recessed below the surface somewhat. Growth o homoepitaxial synthetic diamond is nucleated in this manner by each see crystal. Growth continues laterally and vertically at the site of eac seed crystal such that the individual growth sites combine or merge wit one another to produce a large-area, single crystal mosaic diamond shee on the substrate. The substrate may then be removed by conventiona means. In a most preferred embodiment, the plasma of feedstock gases is generated by microwave CVD.
In still another aspect, the present invention provides a method for fabricating large-area mosaic sheets of single crystal homoepitaxial synthetic diamond by forming an array of pits in the surface of a substrate; (coating the substrate to form a layer of non-diamond nucleating material on the principal surface of the substrate, including in the pits) placing a diamond seed crystal in each of the pits; and growing single crystal diamond nucleated by the diamond seed crystals on the substrate as a single unitary mosaic sheet. The layer of non-diamond nucleating material is preferably an oxide layer which inhibits the growth of polycrystalline diamond on the substrate.
These and other objects, advantages and features of the present invention will be more fully described in the detailed description of the preferred embodiments of the invention with reference to the drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates diagrammatically in cross-section a side view of a silicon wafer having an array of pits in accordance with the present invention. Figure 2 illustrates - diagrammatically a plan view of the silicon wafer of Figure 1 in which a diamond seed crystal is shown in each pit.
Figure 3 illustrates diagrammatically in cross-section of the silicon wafer substrate of Figure 2 with partial growth of homoepitaxial synthetic diamond at each seed crystal site.
Figure h illustrates diagrammatically in cross-section a side view of the silicon wafer substrate of Figure 3 after formation of a single crystal mosaic diamond film.
Figure 5 illustrates diagrammatically in cross-section a side view of a silicon wafer having an array of tetrahedral pits in accordance with the present invention.
Figure 6 illustrates diagrammatically a plan view of the silicon wafer of Figure 5 in which a diamond seed crystal is shown in each pit.
Figure 7 illustrates diagrammatically in cross-section a side view of the silicon wafer substrate of Figure 6 following growth of an oxide layer.
Figure 8 illustrates diagrammatically in cross-section a side view of the silicon wafer substrate of Figure 7 after formation of a single crystal mosaic diamond film.
Figure 9 shows the Raman spectrum of a diamond sample made in accordance with the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to Figure 1 of the drawings, substrate 20 i shown which may comprise a silicon wafer, or other substrate "such as metal substrate coated with silicon dioxide or another suitabl non-nucleating coating, upon which a large-area mosaic diamond shee will be formed. A plurality of pits, preferably tetrahedral pits 22 are etched or otherwise formed in the surface of substrate 20 Tetrahedral pits 22 are preferably formed by patterned etching substrat 20 although other techniques of forming pits 22 may be suitable.
More specifically, a layer of oxide is formed thermally o principal surface 23 which comprises the (100) plane of silicon wafe substrate 20. Using conventional photolithographic techniques, the SiO layer is patterned to form a mask that allows tetrahedral pits 22 to b etched into principal substrate 23. A preferred etchant is an aqueou solution of (CH3)z,N0H (10% by weight) at 90* C. Also suitable is a aqueous solution of KOH (25% by weight). The (100) planes of silico wafer substrate 20 are etched preferentially by these etchant approximately 1000 times faster than the (111) planes. In a few hours the mask is substantially undercut by the action of the etchant and is then removed with HF. In this manner, principal surface 23 consists essentially of intersecting (111) planes.
It is preferred that a square array of tetrahedral pits be formed such as that shown in Figure 2 of the drawingε so that even, symmetrical growth of synthetic diamond from each seed crystal site occurs. Other arrays may also be suitable. Regularly spaced square openings 90 microns by 90 microns x 50 microns on 100 micron centers are particularly preferred, but the size of the pits is essentially dictated by the size of the seed crystals utilized.
Next, seed crystals 24 are selected to be placed in tetrahedral pits 22. Diamond seed crystals 24 should be high-quality diamond crystals having a geometry such that one seed " crystal substantially fills each tetrahedral pit 22. For example, diamond seed crystals or grit approximately 75 microns to about 100 microns in size (largest dimension of the crystal) faceted on (111) planes are particularly preferred. Suitable seed crystals may be obtained from a number of commercial suppliers such as General Electric Corporation or De Beers and are manufactured by high-pressure techniques.
In order to remove any foreign matter on the surface of seed crystals 24 they are washed, preferably in a solution of aN03 followed by a concentrated bath of HF and HNO3. Following a deionized H20 rinse the seed crystals are then dried.
Although a number of techniques may be available to place seed crystals 24 in position in pits 22, the most preferred technique is through the use of a slurry. An excess of diamond seed crystals is added to a 0.01% by weight solution of a novolac polymer in an organic solvent. Substrate 20 is placed in a bath of the diamond slurry whereupon a single seed crystal 24 settles into each tetrahedral pit 22; this process may be enhanced by gentle agitation. The slurry is then drained off and any seed crystals on substrate 20 other than those in pits 22 are removed. Substrate 20 is then dried by heating. The polymer serves to attach diamond seed crystals 24 in tetrahedral pits 22.
Due to variations in the sizes of pits 22 and of diamond seed crystals 24, as well as the nature of the slurry technique used to αeposit diamond seed crystals in pits 22 some pits may be vacant and others may contain two seed crystals, however these occurrences are relatively insignif cant where the various parameters are closely controlled. Most preferably, at least 90% of pits 24 should contain only a single properly oriented seed crystal 24, i.e. the (100) face is substantially co-planar with principle surface 23. In other "words, in the plan view shown in Figure 2 of the drawings diamond seed crystals 24 are shown with the (100) crystalline plane face up. Although this face should be substantially co-planar with principal surface 26, minor deviations where the grit is slightly recessed in pit 22 or extends above the plane of principal surface 23 may be acceptable in some circumstances.
Substrate 20 having diamond grit 24 positioned in the array of tetrahedral pits 22 is then placed in a deposition chamber by which plasma enhanced deposition of synthetic diamond is achieved in the following manner. In the most preferred embodiment, substrate 20 having diamond grit 24 in the array of tetrahedral pits 22 is placed on a susceptor in the chamber of a microwave chemical vapor deposition apparatus (not shown). Prior to deposition of synthetic diamond on substrate 20, a hydrogen etch is performed in the conventional manner which removes native oxide and other contaminants from principal surface 23 of substrate 20 and from the exposed surfaces of diamond grit 24. For the hydrogen etch, 100% hydrogen at 45 torr, 900βC, 900 SSCM at a microwave power level of 1.0 kw is preferably utilized, although values - which are near the stated values are also suitable. The hydrogen etch is typically carried out for about 15 to about 60 minutes.
Optionally at this stage, principal surface 23 may be further conditioned by an oxygen treatment which utilizes a mixture of gases comprising by volume from about 15-25% oxygen, from about 60-75% argon and from about 0.1-10% hydrogen. The flow of gases during thi step will typically be within the following ranges: 02 about 15-2
SSCM, most preferably about 20SSCM, argon about 60-75 SSCM, mos preferably about 68 SSCM; and hydrogen about 0.1 to about 10 SSCM, mos preferably about 0.1 SSCM. The oxygen treatment is in the nature of passivation of principal surface 23 to inhibit the nucleation and growt of polycrystalline diamond at points other than at seed crystals 24.
The oxygen treate ent is performed in the deposition chamber at abou
10-60 torr, preferably about 40 torr at a microwave power of about 400 and at a temperature of from about 700-1000βC, most preferably about
900βC.
Following the hydrogen etch, or the optional oxygen passivation treatment described above, a mixture of gases is flowed into the chamber for microwave assisted chemical vapor deposition at a microwave power level of from about 1.0 to 2.0 kw, or preferably 1.5 kw, and at a temperature of from about 700-1000" C, preferably 900β C. For optimum mosaic diamond fabrication, the concentration and the proportions of the feedstock gases are relatively critical. It has been found that from about .5% to about 5.0% and more preferably about 1.5% by volume of a carbon forming gas, from about .5% to about 1.5% and more preferably about 1.0% by volume oxygen and from about 93.5% to 99.5% and most preferably about 97.5% by volume hydrogen as the feedstock gas mixture produces excellent mosaic diamond growth in accordance with the present invention. Concentrations significantly outside these ranges produce poor diamond growth which is substantially polycrystalline in nature. Although the gas pressure may vary substantially, it is typically from about 40 to about 60 torr and more preferably about 40 torr. A number of carbon source gases are suitable for use in th present invention such as methane, ethanol and acetylene. Mos preferred is methane. The presence of hydrogen is based on th knowledge that hydrogen prevents the accumulation of non-diamond materials during the deposition process.
As stated, the most preferred technique for the deposition of synthetic diamond from the feedstock gases in the present invention is plasma-enhanced chemical vapor deposition and most preferably microwave-enhanced plasma CVD. It has been found that a frequency of 2.45 GHZ is particularly useful for all steps in the present invention. Other plasma-enhanced CVD techniques may also be suitable for use herein.
Diamond growth is nucleated at each seed crystal 24 and grows both vertically and laterally as shown in Figure 3 of the drawings. Under the preferred conditions set forth herein, diamond growth which has been estimated at about 4 microns to 10 microns/hr has been observed.
Under these conditions, the individual diamond deposits 26 begin to merge to form a mosaic diamond sheet which is equivalent to a single synthetic diamond sheet for many purposes. For a silicon wafer having a diameter of about 1.0 cm , utilizing a square array of about 10,000 tetrahedral pits, it has been found that in approximately 60-70 hours a large-area homoepitaxial synthetic mosaic diamond sheet covering the majority of principal surface 23 is formed. As will be appreciated by those skilled in the art, substrate 20 may then be removed by etching, machining, or other means.
The mosaic diamond sheet 28 which is formed by the method of the present invention has minimal dislocations at the boundaries of the merged deposits and minimal polycrystalline inclusions. Mosaic diamon sheet 28 is essentially a single crystal sheet which is useful in man applications, including as a material for use in microelectronic devices.
In still another embodiment of the present invention second method of forming a mosaic diamond sheet is described which provides even greater control over unwanted polycrystalline diamond growth. Referring now to Figure 5 of the drawings substrate 40 is prepared in the previously described manner to provide an array of tetrahedral pits 42 in which diamond seed crystals 44 are positioned at principal surface 43, as shown in Figure 6. The method of preparation and materials used are those described in connection with the previous embodiment.
Substrate 40 having an array of diamond seed crystals 44 is then placed in a deposition chamber for plasma enhanced chemical vapor deposition of synthetic diamond. In one preferred embodiment, substrate 40 is placed on a susceptor in the chamber of a plasma-enhanced chemical vapor deposition apparatus, which again is preferably a microwave CVD apparatus.
Prior to deposition of diamond on substrate 40, principal surface 43 of substrate 40 is oxidized to form an oxidation layer 45 as shown in Figure 7. Oxide layer 45 serves to inhibit the formation of diamond growth at locations on substrate 40 other than at diamond seed crystals 44. In other words, as previously explained during the deposition of synthetic diamond, sites directly on substrate 40 between seed crystal 44 may nucleate diamond growth. This type of diamond growth proceeds in random planes forming polycrystalline regions which appear as polycrystalline inclusions in the finished mosaic diamond sheet and which interfere with the desired properties of the final diamond product. Thus, the purpose of oxide layer 45 is to inhibit thi unwanted growth. Oxide layer 45 is preferably from about 100 angstrom to about 300 angstroms thick and more preferably about 200 angstrom thick. Other materials may be suitable for this purpose such as non-diamond nucleating cladding or another material such as copper whic does not support nucleation and growth of diamond. In the »preferre method, areas of substrate 40 within pits 42 which are not bonded t diamond seed crystals 44 are also effectively oxidized. In anothe embodiment, substrate 40 is oxidized, or coated in some other manner with a layer of material which inhibits polycrystalline diamond growt prior to the insertion of the seed crystals. In this embodiment, th inner surfaces of the pits are also oxidized or coated as shown i Figures 3, 4, 7 and 8.
A hydrogen etch is again performed as described above whic removes contaminants from diamond grit 44 and which modifies oxide laye 45 in a manner not fully understood. An oxygen treatment, again in th manner described above, is then performed which generally re-establishe the integrity of oxide layer 45. Following the oxygen treatment, mixture of feedstock gases is then flowed into the chamber in the sam manner and proportions as described in the previous embodiment fo diamond deposition vapor and diamond is grown by CVD.
Accordingly, individual diamond deposits grow from each see crystal 44 and extend laterally across oxide layer 45 to merge, formin mosaic diamond sheet 48. Substrate 40, including oxide layer 45, ma then be removed using conventional techniques.
In the most preferred embodiment, it has been found that an intermittent diamond growth/oxygen treatment process is very effective in reducing polycrystalline growth. Accordingly, in this embodiment, following a short interval of several hours of diamond growth, th deposition of diamond is interrupted and the oxygen treatment describe above is instituted for about 15 to 60 minutes, preferably about 3 minutes. Diamond growth is reinεtituted for another few hours followe by another short period of oxygen treatment. Diamond growth and oxyge treatment are continuously cycled in this manner throughout th formation of the diamond mosaic sheet. It is believed that thi technique continuously maintains the integrity of the passivation laye and removes any contaminants from diamond surfaces.
EXAMPLE
The following example is for the purpose of illustration only and is not in any manner intended to limit the scope of the present invention.
A silicon substrate having approximately a 1 cm principal
(100) surface having approximately 10,000 tetrahedral pits, the majority containing diamond seed crystals with (100) faces substantially co-planar with the substrate surface, was obtained and placed in a microwave CVD deposition chamber. The substrate was hydrogen etched and subsequently treated with oxygen to form a passivation layer as described herein. Synthetic diamond was deposited at a temperature of
900*C at 50 Torr using a mixture of 02, H2, and CH^ within the aforementioned described ranges at flow rates of 6 SSCM 02, 900 SSCM H2 and 12 SSCM CH^ for approximately 70 hours. Microwave power was 1.5 kw at 2.45 GHZ. A substantially continuous homoepitaxial mosaic diamond sheet was formed; the Raman spectrum for the deposit shown in Figure 9 confirms the purity of the diamond deposit.

Claims

Q1AWSWhat is claimed is:
1. A method for producing large-area synthetic diamond sheet comprising the steps of: •» providing a substrate; forming a plurality of pits in said substrate; placing a diamond crystal in substantially each of sai pits; and forming by plasma-assisted chemical vapor deposition a layer of synthetic diamond which is nucleated by said diamond crystals on the surface of said substrate.
2. The invention recited in claim 1, wherein said plasma-assisted chemical vapor deposition is microwave chemical vapor deposition.
3. The invention recited in claim 1, wherein said substrate is silicon and said pits are tetrahedral pits.
4. The invention recited in claim 1, further including the step of removing said substrate from said synthetic diamond layer.
5. The invention recited in claim 1, wherein said synthetic diamond layer forming step by plasma-assisted chemical vapor deposition includes the use of a feedstock gas mixture containing from about .5 to 5% by volume of a carbon source gas, from about .5 to about 1.5% by volume oxygen and from about 97.5 to about 99.5% by volume hydroge .
6. The invention recited in claim 5, wherein said carbo source gas is selected from the .group consisting of methane, ethanol an acetylene.
7. The invention recited in claim 1, wherein said substrate is coated with a layer of non-diamond nucleating* material prior to said diamond crystal placing step.
8. The invention recited in claim 1, wherein said substrate is coated with a non-diamond nucleating layer after said diamond crystal placing step.
9. The invention recited in claim 7, wherein said non-diamond nucleating layer is an oxide layer on said substrate.
10. The invention recited in claim 8, wherein said non-diamond nucleating layer is a layer of oxide formed on said substrate.
11. The invention recited in claim 1, wherein said substrate and said diamond crystals are hydrogen etched after said diamond crystal placing step.
12. A method for producing large-area synthetic diamond sheets comprising the steps of: providing a substrate; forming a plurality of pits in said substrate; placing a diamond crystal in substantially each of said pits; exposing said substrate to an oxygen-based gaε mixture; and forming by plasma-assisted chemical vapor deposition a laye of synthetic diamond which is nucleated by said diamond crystals on th surface of said substrate.
13. The invention recited in claim 12, wherein sai plasma-assisted chemical vapor deposition is microwave chemical vapo deposition.
14. The invention recited in claim 12, wherein sai substrate is silicon and said pits are tetrahedral pits.
15. The invention recited in claim 12, further includin the step of removing said substrate from said synthetic diamond layer.
16. The invention recited in claim 12, wherein sai synthetic diamond layer forming step by plasma-assisted chemical vapo deposition includes the use of a feedstock gas mixture containing fro about .5 to 5% by volume of a carbon source gas, from about .5 to abou 1.5% by volume oxygen and from about 97.5 to about 99.5% by volum hydrogen.
17. The invention recited in claim 16, wherein said carbo source gas is selected from the group consisting of methane, ethanol an acetylene.
18. A method for producing large-area synthetic diamon sheets comprising the steps of: providing a substrate; forming a plurality of pits in said substrate; placing a diamond crystal in substantially each of sai pits; and exposing said substrate to an oxygen-based gas mixture; forming by plasma-assisted chemical vapor deposition a layer of synthetic diamond which is nucleated by said diamond crystals on the surface of said substrate.
19. The invention recited in claim 18, wherein said oxygen-based gas mixture includes oxygen, argon and hydrogen.
20. The invention recited in claim 18, wherein, in parts by volume, said oxygen-based gas mixture contains from about 15 to 25% oxygen, from about 60 to 75% argon and from about .1 to 10% hydrogen.
21. The invention recited in claim 18, wherein said plasma-assisted chemical vapor deposition is microwave chemical vapor deposition.
22. The invention recited in claim 18, wherein said substrate is silicon and said pits are tetrahedral pits.
23. The invention recited in claim 18, wherein that further including the step of removing said substrate from said synthetic diamond layer.
24. The invention recited in claim 18, wherein said synthetic diamond layer forming step by plasma-assisted chemical vapor deposition includes the use of a feedstock gas mixture containing from about .5 to 5% by volume of a carbon source gas, from about .5 to about 1.5% by volume oxygen and from about 97.5 to about 99.5% by volume hydrogen.
25. The invention recited in claim 18, wherein said carbo source gas is selected from the group consisting of methane, ethanol an acetylene.
26. The invention recited in claim 18, wherein sai substrate is coated with a layer of non-diamond nucleating- materia prior to said diamond crystal placing step.
27. The invention recited in claim 18, further includin the step of cycling between said oxygen exposure and said diamon deposition steps to form a substantially continuous diamond sheet on said substrate.
28. The invention recited in claim 18, further including the step of hydrogen etching said substrate after said step of exposing said substrate to said oxygen-based gas mixture.
29. A method for producing large-area synthetic diamond sheets comprising the steps of: providing a βubstrate; forming a layer of material on said substrate which is substantially non-diamond nucleating forming a plurality of pits in said substrate; placing a diamond crystal in substantially each of said pits; and forming by plasma-assisted chemical vapor deposition a layer of synthetic diamond which is nucleated by said diamond crystals on the surface of said βubstrate, wherein said layer of non-diamond nucleating material inhibits the growth of polycrystalline diamond.
30. The invention recited in claim 29, wherein sa plasma-assisted chemical vapor deposition is microwave chemical vap deposition.
31. The invention recited in claim 29, wherein sai substrate is silicon and said pits are tetrahedral pits. ,
32. The invention recited in claim 29, wherein tha further including the step of removing said substrate from sai synthetic diamond layer.
33. The invention recited in claim 29, wherein sai synthetic diamond layer forming step by plasma-assisted chemical vapo deposition includes the use of a feedstock gaε mixture containing fro about .5 to 5% by volume of a carbon source gaε, from about .5 to abou 1.5% by volume oxygen and from about 97.5 to about 99.5% by volum hydrogen.
34. The invention recited in claim 29, wherein said carbon source gas is selected from the group consisting of methane, ethanol and acetylene.
35. The invention recited in claim 29, wherein said βubstrate is coated with said layer of non-diamond nucleating material prior to βaid diamond crystal placing step.
36. The invention recited in claim 29, wherein said substrate is coated with said non-diamond nucleating layer after said diamond crystal placing step.
37. The invention recited in claim 29, wherein said non-diamond nucleating layer is an oxide layer on said substrate.
38. The invention recited in claim 29, wherein said non-diamond nucleating layer is a layer of oxide formed on said substrate.
39. The invention recited in claim 29, wherein said substrate and said diamond crystals are hydrogen etched after said diamond crystal placing step.
40. A large-area synthetic diamond sheet made in accordance with the process of claim 1.
PCT/US1992/005149 1991-06-18 1992-06-17 Process for making large-area single crystal diamond films WO1992022689A1 (en)

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US718,308 1991-06-18

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EP0562574A2 (en) * 1992-03-26 1993-09-29 Yoichi Hirose Diamond crystal and method for forming the same
EP0612868A1 (en) * 1993-02-22 1994-08-31 Sumitomo Electric Industries, Ltd. Single crystal diamond and process for producing the same
US5632812A (en) * 1993-03-10 1997-05-27 Canon Kabushiki Kaisha Diamond electronic device and process for producing the same
EP0779859A1 (en) * 1994-08-31 1997-06-25 Ellis E. Roberts Oriented crystal assemblies
FR2746415A1 (en) * 1996-03-25 1997-09-26 Electrovac SUBSTRATE COATED WITH A POLYCRYSTALLINE DIAMOND LAYER
EP1708255A2 (en) * 2005-03-28 2006-10-04 Sumitomo Electric Industries, Ltd. Diamond substrate and manufacturing method thereof
JP2006335637A (en) * 2005-03-28 2006-12-14 Sumitomo Electric Ind Ltd Diamond substrate and manufacturing method thereof
WO2007029269A1 (en) * 2005-09-05 2007-03-15 Rajneesh Bhandari Synthesis of large homoepitaxial monocrystalline diamond
CN111962042A (en) * 2020-07-21 2020-11-20 南京航空航天大学 Laser-induced ordered nucleation diamond microstructure in-situ preparation method
CN114959891A (en) * 2022-03-30 2022-08-30 上海征世科技股份有限公司 Single crystal diamond and MPCVD preparation method thereof

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US5006203A (en) * 1988-08-12 1991-04-09 Texas Instruments Incorporated Diamond growth method
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Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0562574A2 (en) * 1992-03-26 1993-09-29 Yoichi Hirose Diamond crystal and method for forming the same
EP0562574A3 (en) * 1992-03-26 1994-08-24 Yoichi Hirose Diamond crystal and method for forming the same
US5445851A (en) * 1992-03-26 1995-08-29 Canon Kabushiki Kaisha Method for forming tabular diamond crystals
US5576107A (en) * 1992-03-26 1996-11-19 Canon Kabushiki Kaisha Diamond crystal and method for forming the same
EP0612868A1 (en) * 1993-02-22 1994-08-31 Sumitomo Electric Industries, Ltd. Single crystal diamond and process for producing the same
US5632812A (en) * 1993-03-10 1997-05-27 Canon Kabushiki Kaisha Diamond electronic device and process for producing the same
EP0779859A1 (en) * 1994-08-31 1997-06-25 Ellis E. Roberts Oriented crystal assemblies
EP0779859A4 (en) * 1994-08-31 1998-12-02 Ellis E Roberts Oriented crystal assemblies
FR2746415A1 (en) * 1996-03-25 1997-09-26 Electrovac SUBSTRATE COATED WITH A POLYCRYSTALLINE DIAMOND LAYER
EP1708255A2 (en) * 2005-03-28 2006-10-04 Sumitomo Electric Industries, Ltd. Diamond substrate and manufacturing method thereof
JP2006335637A (en) * 2005-03-28 2006-12-14 Sumitomo Electric Ind Ltd Diamond substrate and manufacturing method thereof
EP1708255A3 (en) * 2005-03-28 2010-08-25 Sumitomo Electric Industries, Ltd. Diamond substrate and manufacturing method thereof
WO2007029269A1 (en) * 2005-09-05 2007-03-15 Rajneesh Bhandari Synthesis of large homoepitaxial monocrystalline diamond
CN111962042A (en) * 2020-07-21 2020-11-20 南京航空航天大学 Laser-induced ordered nucleation diamond microstructure in-situ preparation method
CN114959891A (en) * 2022-03-30 2022-08-30 上海征世科技股份有限公司 Single crystal diamond and MPCVD preparation method thereof

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