Process and apparatus for diamond synthesis

Patent metadata

Field	Value
Publication number	US-9487858-B2
Application number	US-38127009-A
Country	US
Kind code	B2
Filing date	Mar 10, 2009
Priority date	Mar 13, 2008
Publication date	Nov 8, 2016
Grant date	Nov 8, 2016

Abstract

The present invention relates to a microwave plasma deposition process and apparatus for producing diamond, preferably as single crystal diamond (SCD). The process and apparatus enables the production of multiple layers of the diamond by the use of an extending device to increase the length and the volume of a recess in a holder containing a SCD substrate as layers of diamond are deposited. The diamond is used for abrasives, cutting tools, gems, electronic substrates, heat sinks, electrochemical electrodes, windows for high power radiation and electron beams, and detectors.

First claim

What is claimed:

1. A process for growing diamond in a microwave plasma reactor, the process comprising:
(a) providing a substrate holder for holding a growth substrate and growing the diamond, the substrate holder comprising a bottom surface, a top surface opposing the bottom surface in a longitudinal axis direction defined by the substrate holder, a base surface between the top surface and bottom surface, and one or more sidewalls extending between the base surface and the top surface, wherein:
(i) the one or more sidewalls and the base surface define a cavity in the substrate holder, the cavity having a depth in the longitudinal axis direction extending between the base surface and the top surface,
(ii) the cavity comprises a first recess in a lower portion of the cavity and a second recess in an upper portion of the cavity,
(iii) the first recess is adjacent the base surface, and
(iv) the second recess is directly above the first recess and extends a predetermined distance above the first recess to define a growth volume space in the cavity;

(b) placing the substrate in the first recess of the cavity;
(c) placing the holder in the plasma reactor so that the plasma can contact the holder and the substrate in the growth volume space;
(d) generating a plasma in the reactor from a feedgas comprising methane, hydrogen and optionally nitrogen in an amount and at a temperature and pressure which deposits a first thickness of diamond on the substrate and at least partially within the second recess growth volume in the cavity;
(e) providing a recess extending means for extending the distance of the second recess above the first recess along the longitudinal axis direction to increase the growth volume space in the cavity and the cavity depth;
(f) extending the distance of the second recess above the first thickness of diamond on the substrate and increasing the growth volume space in the cavity with the recess extending means and depositing a second thickness of diamond on the first thickness of diamond and at least partially within the extended second recess growth volume in the cavity; and
(g) stopping the diamond growth in the reactor and opening the reactor to provide the substrate with at least the first and second thicknesses of diamond.

2. The process of claim 1 , wherein the holder is fabricated from molybdenum.

3. The process of claim 1 , wherein the substrate is a member selected from the group consisting of diamond and silicon.

4. The process of claim 3 , wherein the diamond growth on the substrate forms polycrystalline diamond.

5. The process of claim 3 , wherein the feedgas in step (d) further comprises diborane (B 2 H 6 ) into the reactor, thereby producing boron doped diamond (BDD).

6. The process of claim 1 , wherein the substrate is a single crystal diamond substrate and the diamond growth is single crystal diamond (SCD).

7. The process of claim 1 , wherein the substrate holder comprises a plurality of separate and spaced apart cavities, wherein:
(i) each cavity is defined by one or more sidewalls and a base surface of the substrate holder,
(ii) each cavity comprises a first recess in a lower portion of the cavity and a second recess in an upper portion of the cavity, and
(iii) each cavity is adapted to hold a substrate for simultaneous multiple diamond growth.

8. The process of claim 7 , wherein a substrate is placed in the first recess of each cavity and is individually adjusted in height relative to the top surface of the substrate holder by placing an insert having a thickness selected such that the temperature of each chip can be adjusted to a suitable value for deposition.

9. The process of claim 8 , wherein each substrate is grown into a thickness range position such that a top portion of the the second thickness of diamond is located from just below to just above the top surface of the substrate holder.

10. The process of claim 8 , wherein a temperature at each cavity is controlled by adjusting the plasma, a cooling means, the substrate height into the plasma, or a combination thereof to create temperature uniformity among each of the plurality of substrates.

11. The process of claim 1 , wherein the feedgas further comprises diborane (B 2 H 6 ) in a quantity of up to 100 parts per million (ppm).

12. The process of claim 11 , wherein the feedgas comprises nitrogen in a quantity of up to 500 ppm.

13. The process of claim 1 , wherein the methane is provided between 3-15% of the feedgas and the reactor is operated at a pressure between 14-160 Torr, a power between 2-3 kW and using a 2.45 GHz microwave reactor.

14. The process of claim 1 , wherein the reactor operates under a microwave frequency selected from the group consisting of a 2.45 GHz reactor and a 915 MHz reactor.

15. The process of claim 1 , wherein feedgas has (i) a flow rate between 100 and 1200 sccm, (ii) a molar ratio of methane to hydrogen of 3-15%, and (iii) a molar ratio of nitrogen to hydrogen of 0-10%.

16. The process of claim 1 , wherein the cavity has a square cross-sectional geometry in the longitudinal axis direction.

17. The process of claim 1 , wherein the second recess has a larger cross sectional area than that of the first recess taken perpendicular to the longitudinal axis direction.

18. The process of claim 1 , wherein:
(i) the substrate is placed on the base surface in the first recess of the cavity in the substrate holder; and
(ii) the substrate, the first thickness of diamond, and the second thickness of diamond are spaced apart from the one or more sidewalls in the cavity during and after deposition of the first thickness of diamond and the second thickness of diamond.

19. The process of claim 18 , wherein the substrate, the first thickness of diamond, and the second thickness of diamond are spaced apart from the one or more sidewalls during and after deposition of the first thickness of diamond and the second thickness of diamond by a distance ranging from 0.1 mm to 2 mm.

20. The process of claim 18 , wherein the second recess has a larger cross sectional area than the cross sectional area of the first recess taken perpendicular to the longitudinal axis direction of the holder.

21. The process of claim 18 , wherein the plasma reactor comprises:
(i) a reactor chamber enclosing the substrate holder after placing the substrate holder in the plasma reactor in step (c), during deposition of the first thickness of diamond in step (d), and during deposition of the second thickness of diamond during step (f); and
(ii) a quartz dome as a component of the reactor chamber enclosing the substrate holder, the quartz dome being positioned to facilitate generation of the plasma in the reactor chamber during deposition of the first thickness of diamond in step (d), and during deposition of the second thickness of diamond during step (f).

22. The process of claim 1 , wherein the plasma reactor comprises:
(i) a reactor chamber enclosing the substrate holder after placing the substrate holder in the plasma reactor in step (c), during deposition of the first thickness of diamond in step (d), and during deposition of the second thickness of diamond during step (f); and
(ii) a quartz dome as a component of the reactor chamber enclosing the substrate holder, the quartz dome being positioned to facilitate generation of the plasma in the reactor chamber during deposition of the first thickness of diamond in step (d), and during deposition of the second thickness of diamond during ste

Assignees

• Asmussen Jes
• Grotjohn Timothy
• Reinhard Donnie
• Ramamurti Rahul
• Yaran M Kagan
• Schuelke Thomas
• Becker Michael
• King David
• Univ Michigan State
• Fraunhofer Usa

Inventors

• Asmussen Jes
• Grotjohn Timothy
• Reinhard Donnie
• Ramamurti Rahul
• Yaran M Kagan
• Schuelke Thomas
• Becker Michael
• King David

Classifications

• C30B25/105 Primary

  by irradiation or electric discharge · CPC title

• C23C16/278 Primary

  doping or introduction of a secondary phase in the diamond · CPC title

• C30B25/08

  Reaction chambers; Selection of materials therefor · CPC title

• C23C16/4586

  Elements in the interior of the support, e.g. electrodes, heating or cooling devices · CPC title

• C23C16/4585

  Devices at or outside the perimeter of the substrate support, e.g. clamping rings, shrouds · CPC title