In 2005, the development of II-VI silicon carbide substrates was still very slow, but by 2020, the revenue of II-VI semi-insulating SiC substrates surpassed Cree. The Yole report shows that the market share of II-VI in 2020 has increased from 27% in 2019 to 35%, while Cree has dropped from 42% to 33%.
According to reports, North Carolina State University has carried out research on SiC sublimation growth very early. With a number of key patents, Cree-Research was formally established in 1987 and became the first company to provide commercial silicon carbide in 1991.
In addition to Cree-Research, in the early 1990s, Westinghouse Technology Center and Advanced Technology Materials Corporation (ATMI) also actively participated in the research and development of SiC.
However, the early SiC sublimation growth research was full of ups and downs, and there were various technical challenges that were difficult to overcome, including microtubules, doping, polytype control, diameter expansion, and crystal defects.
Cree-Research launched 25mm 6H SiC and 50mm 4H SiC in 1991 and 1998, respectively. Although there are multiple suppliers producing similar products, the prices are very expensive, and the density of microtubes exceeds 100cm-2.
In order to promote the wider commercialization of SiC, in 1999, the "Title III Program" of the US National Defense Production Act provided much-needed start-up funds for the SiC industry. The US Air Force provided three companies with "cost sharing contracts", including Cree -Research, Sterling (ATMI) and Litton-Airtron, the goal is to expand the diameter of the SiC substrate to 75mm and improve the crystal quality.
Beginning in 2002, the WBGS program of the US National Defense Advanced Research Projects Agency also paid close attention to the development of wide band gap semiconductor materials. Both Cree and Sterling won relevant contracts. The goal is to expand the diameter of N-type and semi-insulating SiC substrates to 100 mm and The density of microtubes is reduced to below 1cm-2.
In December 2000, Litton Industries was acquired by Northrop Grumman for US$3.8 billion (approximately RMB 24.5 billion) or US$80 per share. At the end of 2001, Litton-Airtron's SiC R&D department was acquired by II-VI.
In 2002, a few weeks after obtaining the DARPA contract, Sterling's parent company Uniroyal Corporation filed for bankruptcy, resulting in the outflow of key technical personnel. Dow Corning immediately acquired Sterling.
Moreover, the early development of SiC technology is far from achieving the goals of the contract plan. As can be seen from the figure below, Cree's quality is significantly better than its competitors.
In 2005, DARPA's support for SiC substrates basically ended, and only Cree showed strong signs of accelerating the commercialization of SiC substrates. At that time, Dow Corning's research and development was still struggling, and the progress of II-VI was also very slow.
Subsequently, DARPA will mainly invest in SiC power switches and GaN RF devices, benefiting from Cree's substrate business.
U.S. Gov Support II-VI
After WBGS stopped funding, Title III plans to continue to promote the development of SiC substrates, by providing more than 75 million US dollars (approximately 484 million yuan) of government funding, and cooperation with Cree (Wolfspeed), Raytheon, Northrop Grumman and Triquint (Qorvo) to increase the The manufacturability of the first generation of GaN HEMT.
In the early 2000s, Cree continued to take the lead in the development and promotion of SiC substrate technology. Through vertical integration, they were able to directly promote the improvement of material quality through internal use requirements, but this also meant that their substrate and epitaxial customers were also theirs. Main competitor.
The United States believes that there is only a single supplier of SiC substrates, which may hinder the development of the industry. Pure SiC substrate suppliers are critical to the long-term development and commercialization of SiC and GaN device technologies.
As a result, from 2003 to 2017, AFRL provided II-VI with 4 large contracts, totaling more than 350 million yuan.
The main goal of the first two contracts is to expand the diameter of 4HN SiC to 100 mm. However, at that time, the edge area of the 100 mm semi-insulating 6H SiC of II-VI was full of formed grains and other defects, and the microtube density reached 117cm-2.
Therefore, while supporting II-VI, AFRL also supports Intrinsic's development of SiC. Intrinsic is composed of key personnel after Sterling was acquired.
In less than two years, Intrinsic quickly and successfully demonstrated high-quality 100-mm SiC. More importantly, in September 2005, Intrinsic took the lead to release zero microtubules (ZMPTM) 4HN SiC.
But in July 2006, Cree acquired Intrinsic. In 2007, Cree released 100mm 4HN ZMPTM SiC and 100mm semi-insulating SiC.
Fortunately, the development of II-VI has also progressed. During 2003-2010, II-VI expanded the crystal diameter from 50 mm to 100 mm, and also released 100 mm 4HNSiC and semi-insulating SiC.
II-VI 100-mm semi-insulating 6H SiC substrate and 100mm 4HN SiC substrate.
At the end of 2010, AFRL and II-VI signed the largest contract-more than 20 million US dollars (about 130 million yuan), focusing on the development and commercialization of 6-inch 4HN SiC and semi-insulating 6H SiC, and the continued expansion of the diameter to 8 inch.
After receiving funding, II-VI made substantial investments in facilities and equipment, including the expansion of the New Jersey plant and the establishment of two manufacturing plants in Mississippi.
In the end, II-VI relied on its exclusive patented Advanced Physical Vapor Transport (APVT) and Axial Gradient Transport (AGT) crystal growth technology to achieve the goal of 6-inch and 8-inch SiC single crystals.
II-VI demonstrated microtube-free 100mm 6H semi-insulating and 150mm 4HN SiC in 2013 and 2014 respectively; in July 2015, it became the first company to showcase 8-inch 4HN SiC.
In March 2017, AFRL provided the fourth contract for II-VI for a period of 5 years with government funding of 12 million U.S. dollars (approximately 774.8 billion yuan). The focus of this work is to improve manufacturing efficiency, reduce defects and reduce costs to grow and manufacture 200 mm 4HN SiC and semi-insulating SiC.
These defect-free large-diameter crystals were grown using a new fully automated growth platform, and II-VI successfully reduced the dislocation density of 200mm 4HN SiC to 1881 cm-2, including a screw density of 598 cm-2 and 272 cm -2 base area density.
In terms of semi-insulating silicon carbide, II-VI uses vanadium compensation to introduce deep energy levels in the band gap. It is the only market supplier of semi-insulating SiC doped with vanadium, and its reproducible and highly uniform resistivity exceeds 1011Ω·cm.
In October 2019, II-VI demonstrated the 200 mm 6H semi-insulating SiC for the first time in the industry.
In the past 30 years, the US Department of Defense has funded more than US$1 billion (approximately RMB 6.457 billion) for wide band gap semiconductors, which can be said to have spawned a whole new industry. Some companies such as Cree Research, Westinghouse, Northrop-Grumman, ATMI, Sterling, Litton-Airtron, Dow and Intrinsic have been merged and some have disappeared. And Wolfspeed-Cree, II-VI "the winner is king", the two companies currently have a combined global market share of more than 70%.
In recent years, with the rapid growth of SiC commercial and military demand, these two companies have also continued to expand their production. In September 2019, Wolfspeed-Cree announced a commitment to invest USD 1 billion to build the world's largest SiC power and RF manufacturing plant. And II-VI continues to expand manufacturing capacity in New Jersey, Pennsylvania and Massachusetts.