Buellton, CA, United States
Buellton, CA, United States

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Patent
SixPoint Materials, Inc. and Seoul Semiconductor | Date: 2017-03-29

In one instance, the invention provides a bulk crystal of group III nitride having a thickness of more than 1 mm without cracking above the sides of a seed crystal. This bulk group III nitride crystal is expressed as Gax1Aly1In1-x1-y1N (0x11, 0x2Aly2In1-x2-y2N (0x21, 0x2+y21). The bulk crystal of group III nitride can be grown in supercritical ammonia or a melt of group III metal using at least one seed crystal having basal planes of c-orientation and sidewalls of m-orientation. By exposing only c-planes and m-planes in this instance, cracks originating from the sides of the seed crystal are avoided.


Patent
SixPoint Materials, Inc. | Date: 2017-03-07

The present invention discloses a method of removing contaminant from group III nitride single-crystal wafers. The method involves annealing a wafer to concentrate a contaminant in a region of the crystal near the surface of the crystal and removing some of the crystal near the surface that contains at least a portion of the region containing concentrated contaminant. The resultant thinner wafer therefore has less contaminant in it.


Patent
SixPoint Materials, Inc. and Seoul Semiconductor | Date: 2017-02-08

A high-pressure cylindrical reactor suitable for a high-pressure process using supercritical ammonia to form bulk crystals of group III nitride or transition metal nitride is disclosed. In one instance, the reactor has a reactor body and lid formed of precipitation hardenable Ni-Cr superalloy and is sealed by a gasket made of Ni-based metal. Ni content of the gasket is greater than Ni content of both the reactor body and lid. The gasket is tapered so that its thickest part is at or near the gaskets inner radius or circumference, and the thinnest part of the gasket is more than 0.2 inch thick and is at or near the gaskets outer radius or circumference. The gaskets surfaces are compressed at 60,000 psi or higher. This construction provides a consistent seal of the reactor for repeated use.


The present invention discloses methods to create higher quality group III-nitride wafers that then generate improvements in the crystalline properties of ingots produced by ammonothermal growth from an initial defective seed. By obtaining future seeds from carefully chosen regions of an ingot produced on a bowed seed crystal, future ingot crystalline properties can be improved. Specifically, the future seeds are optimized if chosen from an area of relieved stress on a cracked ingot or from a carefully chosen N-polar compressed area. When the seeds are sliced out, miscut of 3-10 helps to improve structural quality of successive growth. Additionally a method is proposed to improve crystal quality by using the ammonothermal method to produce a series of ingots, each using a specifically oriented seed from the previous ingot. When employed, these methods enhance the quality of Group III nitride wafers and thus improve the efficiency of any subsequent device.


Patent
SixPoint Materials, Inc. and Seoul Semiconductor | Date: 2016-01-22

In one instance, the invention provides a method of growing bulk crystal of group III nitride using a seed crystal selected by (a) measuring x-ray rocking curves of a seed crystal at more than one point, (b) quantifying the peak widths of the measured x-ray rocking curves, and (c) evaluating the distribution of the quantified peak widths. The invention also includes the method of selecting a seed crystal for growing bulk crystal of group III nitride. The bulk crystal of group III nitride can be grown in supercritical ammonia or a melt of group III metal using at least one seed selected by the method above.


Patent
SixPoint Materials, Inc. and Seoul Semiconductor | Date: 2015-04-01

A high-pressure cylindrical reactor suitable for a high-pressure process using supercritical ammonia to form bulk crystals of group III nitride or transition metal nitride is disclosed. In one instance, the reactor has a reactor body and lid formed of precipitation hardenable NiCr superalloy and is sealed by a gasket made of Ni-based metal. Ni content of the gasket is greater than Ni content of both the reactor body and lid. The gasket is tapered so that its thickest part is at or near the gaskets inner radius or circumference, and the thinnest part of the gasket is more than 0.2 inch thick and is at or near the gaskets outer radius or circumference. The gaskets surfaces are compressed at 60,000 psi or higher. This construction provides a consistent seal of the reactor for repeated use.


Patent
SixPoint Materials, Inc. and Seoul Semiconductor | Date: 2016-06-27

Provided is a high-pressure reactor suitable for a high-pressure process using supercritical ammonia grow bulk crystal of group III nitride having lateral dimension larger than 2 inches or to form various transition metal nitrides. The reactor has nutrient distributed along the reactors longitudinal axis and seed material positioned at the reactors inner wall and along the reactors longitudinal axis. Nutrient diffuses through supercritical ammonia from the reactors longitudinal axis and deposits on the seed material positioned by the reactors inner wall. Both the nutrient and seed material are heated by the same heater. Material growth can primarily be due to material diffusion through supercritical ammonia. This configuration and methodology reduce convective movement of supercritical ammonia due to temperature differential, providing a more quiescent environment in which group III nitride or transition metal nitride is formed.


Patent
SixPoint Materials, Inc. and Seoul Semiconductor | Date: 2016-06-27

Provided is a high-pressure reactor suitable for a high-pressure process using supercritical ammonia grow bulk crystal of group III nitride having lateral dimension larger than 2 inches or to form various transition metal nitrides. The reactor has nutrient distributed along the reactors longitudinal axis and seed material positioned at the reactors inner wall and along the reactors longitudinal axis. Nutrient diffuses through supercritical ammonia from the reactors longitudinal axis and deposits on the seed material positioned by the reactors inner wall. Both the nutrient and seed material are heated by the same heater. Material growth can primarily be due to material diffusion through supercritical ammonia. This configuration and methodology reduce convective movement of supercritical ammonia due to temperature differential, providing a more quiescent environment in which group III nitride or transition metal nitride is formed.


Grant
Agency: Department of Energy | Branch: ARPA-E | Program: STTR | Phase: Phase II | Award Amount: 1.50M | Year: 2014

SixPoint Materials will create low-cost, high-quality vertical gallium nitride (GaN) substrates using a multi-phase production approach that employs both hydride vapor phase epitaxy (HVPE) technology and ammonothermal growth techniques to lower costs and maintain crystal quality. Substrates are thin wafers of semiconducting material needed for power devices. In its two-phase project, SixPoint Materials will first focus on developing a high-quality GaN substrate and then on expanding the substrate’s size. If successful, SixPoint Materials will enable high-power GaN circuits that can convert power for electric motors and electric vehicles with half the energy loss compared to today’s GaN devices.


Grant
Agency: Department of Energy | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 150.00K | Year: 2015

Significant effort has been exerted to develop cost-effective ammonothermal growth of bulk GaN crystals; however, due to extreme hardness and chemical stability, the wafering process for bulk GaN crystals has not been established yet. Currently, chemical mechanical polishing CMP) to achieve damage-free, atomically-flat wafer surface is so inefficient that ~150 hours are required to finish the surface. To achieve a time and cost efficient process to finish the surface epi-ready, we need to develop a wafer shaping process which minimizes subsurface damage and therefore CMP time. This project proposes a novel grinding method called electrolytic in-process dressing ELID) grinding, which can replace the conventional steps of grinding, lapping and polishing. In addition, ELID grinding potentially causes less subsurface damage than the conventional process. During Phase I, an ELID grinding machine is constructed by adding necessary components to SixPoint's existing grinding machine and the process conditions of ELID grinding will be optimized using small-sized ~10 mm) GaN wafers. At the same time, subsurface damage of the conventional wafering process will be characterized in detail so that we can compare the damage by ELID grinding with the conventional process. After successful demonstration of a proof of concept, we will expand the capacity to 2" GaN wafers in Phase II. The developed ELID grinding process will be incorporated in the wafering process at SixPoint, which will significantly reduce the production cost of GaN substrates.

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