# US 11,299,820 B2 · Electron beam heating and atomic surface restructuring of sapphire surface

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- Number: US 11,299,820 B2
- Document ID: US11299820B2
- Status: Granted
- Kind: B2
- Application number: 15/661,903
- Filed: 2017-07-27
- Published: 2018-02-01
- Granted: 2022-04-12
- Earliest claimed: 2016-07-28
- Assignees: United States of America as represented by the Administrator of NASA
- Applicants: United States of America as represented by the Administrator of NASA
- Inventors: Sang H. Choi; Adam J. Duzik
- Web page: https://patentgrep.com/patent/US11299820B2

## CPC

- C30B 23/063: {Heating of the substrate}
- C30B 23/025: {characterised by the substrate}
- C30B 25/06: by reactive sputtering
- C30B 25/186: {being specially pre-treated by, e.g. chemical or physical means}
- C30B 29/20: Aluminium oxides
- C30B 29/52: Alloys
- H10P 14/2905: {Silicon, silicon germanium or germanium}
- H10P 14/2921: {being crystalline insulating materials}
- H10P 14/2926: {Crystal orientations}
- H10P 14/3411: {Silicon, silicon germanium or germanium}
- H10P 14/3416: {Nitrides}
- H10P 14/3421: {Arsenides}
- H10P 14/3432: {Tellurides}
- H10P 14/3466: {Crystal orientation}
- C30B 29/406: {Gallium nitride}
- C30B 29/48: AIIBVI compounds {wherein A is Zn, Cd or Hg, and B is S, Se or Te}
- C30B: SINGLE-CRYSTAL GROWTH (by using ultra-high pressure, e.g. for the formation of diamonds, B01J3/06); UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL (zone-refining of metals or alloys C22B); PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (casting of metals, casting of other substances by the same processes or devices B22D; working of plastics B29; modifying the physical structure of metals or alloys C21D, C22F); SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (for producing semiconductor devices or parts thereof H10); APPARATUS THEREFOR
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

Systems, methods, and devices of the various embodiments may provide a mechanism to enable the growth of a rhombohedral epitaxy at a lower substrate temperature by energizing the atoms in flux, thereby reducing the substrate temperature to a moderate level. In various embodiments, sufficiently energized atoms provide the essential energy needed for the rhombohedral epitaxy process which deforms the original cubic crystalline structure approximately into a rhombohedron by physically aligning the crystal structure of both materials at a lower substrate temperature.

## Claims

### Claim 1

A method for heating a wafer to support epitaxy film growth on the wafer, comprising:
providing the wafer, wherein the wafer is a sapphire wafer;
heating the wafer with a radiative heating element;
locally restructuring a crystalline structure of a surface of the wafer by applying irradiation to locally heat the surface of the wafer with an electron beam until the surface of the wafer reaches a selected surface temperature for a selected duration, wherein applying the irradiation includes modifying the atomic crystalline structure of the surface of the wafer by colliding electrons of the electron beam with surface atoms in a top layer of the wafer and therein heating the surface atoms to a temperature that is higher than the temperature of the rest of the wafer and sufficient to provide energy needed for deforming an original cubic crystalline structure of a growing epitaxy film into a rhombohedron; and
growing the epitaxy film on the wafer during or after applying the irradiation, wherein growing the epitaxy film includes using the modified atomic surface crystalline structure to facilitate single-crystal epitaxial layer growth.

### Claim 2 (depends on 1)

The method of claim 1, wherein
applying the irradiation comprises uniformly applying the irradiation to heat a thin region of the surface of the wafer to a higher temperature, relative to a temperature of the rest of the wafer, wherein the thin region is a top layer of surface atoms, and
growing the epitaxy film includes using the restructured crystalline structure to orient and anchor the epitaxial film to the wafer as the epitaxial film is grown.

### Claim 3 (depends on 2)

The method of claim 2, wherein heating the wafer with the radiative heating element includes heating the entire wafer to a first temperature from about 400° C. to about 500° C.

### Claim 4 (depends on 3)

The method of claim 3, wherein the selected duration is from about 1 minute to about 2 minutes.

### Claim 5 (depends on 4)

The method of claim 4, wherein the selected surface temperature is about 500° C. and the selected duration is about 2 minutes.

### Claim 6 (depends on 3)

The method of claim 3, wherein the epitaxy film comprises SiGe, CdTe, or GaN.

### Claim 7 (depends on 2)

The method of claim 2, further comprising rotating the wafer while applying the irradiation.

### Claim 8

A vacuum deposition system, comprising:
a growth chamber configured to support a sapphire wafer therein, the sapphire wafer having a diameter;
a radiative heating element configured to heat a back surface of the sapphire wafer;
a flood electron beam gun rated for providing 40 keV to 50 keV electron beam energy, wherein the flood electron beam gun is configured in the growth chamber to make an expansion angle of an electron beam of the flood electron beam gun illuminate a whole surface area of a front surface of the sapphire wafer opposite the back surface based on the sapphire wafer's diameter and wherein the flood electron beam gun has been configured in the growth chamber such that the electron beam uniformly irradiates and evenly heats the front surface of the sapphire wafer via thermalization losses from colliding electrons of the electron beam with the front surface of the sapphire wafer to modify the crystalline structure of the surface by the collision of the colliding electrons of the electron beam with surface atoms in a top layer of the sapphire wafer and therein heating the surface atoms to a temperature that is sufficient to provide energy needed for deforming an original cubic crystalline structure of a growing epitaxy film into a rhombohedron to facilitate single-crystal epitaxial layer growth.

### Claim 9 (depends on 8)

The system of claim 8, wherein the flood electron beam gun is configured and arranged to irradiate the substrate surface to heat a thin region of the top substrate surface of the sapphire wafer to a higher temperature sufficient to cause restructuring of the crystalline structure of the thin region of the surface of the sapphire wafer, such that the epitaxy film is oriented and anchored by the restructured crystalline structure.

### Claim 10 (depends on 9)

The system of claim 9, wherein the radiative heating element is configured and arranged to heat the sapphire wafer to a temperature from about 400° C. to about 500° C.

### Claim 11 (depends on 10)

The system of claim 10, wherein the selected duration is from about 1 minute to about 2 minutes.

### Claim 12 (depends on 11)

The system of claim 11, wherein the selected surface temperature is about 500° C. and the selected duration is about 2 minutes.

### Claim 13 (depends on 12)

The system of claim 12, wherein the epitaxy film comprises SiGe, CdTe, or GaN.

### Claim 14 (depends on 9)

The system of claim 9, further comprising a spinning platform configured to support and impart a rotation to the sapphire wafer while the electron beam irradiates the top surface and while the radiative heating element heats the back surface.

### Claim 15 (depends on 1)

The method of claim 1, wherein growing the epitaxy film includes using the modified atomic surface structure to promote growth of a rhombohedral crystalline film by physically aligning the crystalline structure of the modified atomic surface structure with the crystalline structure of the epitaxy film as it is grown.

### Claim 16 (depends on 8)

The system of claim 8, further including a sputtering gun configured and arranged with the flood electron beam gun to grow the epitaxy film on the sapphire wafer by sputtering particles and using the modified atomic crystalline structure to control crystallization formation of the particles and a resulting orientation thereof upon the surface.

### Claim 17 (depends on 8)

The system of claim 8, wherein the flood electron beam gun and the radiative heating element are positioned oppositely from each other with the sapphire wafer between them and with the flood electron beam gun oriented perpendicularly to the sapphire wafer.