Site: Super Silicon Crystal Research Institute (SSi) Corp.
555-1, Nakanoya, An-naka
Gunma 379-0125, Japan
Date Visited: 12 October 1998
WTEC Attendees: G. Gamota, P. O'Neill-Brown
Silicon is the main element used for most electronic components. For this purpose, silicon is made in form of wafers, and with the push for greater integration of components on single wafer, there is a need for super-large wafer diameters. The present standard for wafers is 200 mm, and this effort is to create high quality 400 mm diameter wafers. Larger silicon wafers are critical to the realization of each new generation of semiconductors. The 300 mm wafer is well on the way to becoming the choice of the next generation substrate, so work on the 400 mm wafer is critical, and Japan hopes to be in the lead for its development.
To achieve such a goal, a number of semiconductor manufacturing companies came together and proposed to the JKTC a 5 year project whose purpose is to develop the technology for 400 mm diameter wafers.
The stockholder companies are the following:
SSi was established on March 29, 1996, and is to run until January 2001, or four years and 11 months (one of the shorter JKTC projects). The total capital for research is ¥13.4 billion (or approximately $100 million). Fifty percent comes from JKTC and the remainder from the companies. SSi employs 36 people, including 28 researchers. Almost all employees come from the stockholding companies.
SSi is organized traditionally, with a Board of Directors made up entirely from the private sector and a steering committee. The steering committee is made up of company employees who review progress four times per year and provide guidance. There are three subcommittees, one each for the three departments: Crystal Technology, Wafer Technology, and Epitaxial Technology.
SSi's research program is laid out in four phases.
Research has progressed on target, and as of October 1998, during the panel's visit, wafer diameter of 400 mm had been achieved. A wafer demonstration "World Premiere" was made at the SEMICON West conference '98. This was quite an achievement, and the Japanese researchers acknowledged that while it was their program that put it all together, much of the credit for specific technologies came from overseas, starting with work of Czochralski in 1917, Bardeen, Brattain and Shockley in 1948-49, and Siemens in 1955. Basically it was excellent engineering work putting things together to push the state of technology.
Current challenges include increasing the crystal weight from 100 kg to 400 kg; reducing flatness from 0.35 micron to 0.13 micron; reducing particle size from 0.12 micron to 0.04 micron; reducing metal impurity from less than 1010 to 108 atoms per cm2; reducing epi layer thickness from 2-5 microns to 1-3 microns; and finally reducing epi layer uniformity from less than 4% to less than 1%.
SSi's approach is to cooperate with worldwide companies interested in this technology, including manufacturers of equipment. It utilizes machines from the following sources:
The company staff members were open in their appreciation for a JKTC type program and felt that it can be a big asset for pushing world technology. Even though the stockholding companies will not have any priority in technology licensing, staff experience in working in this environment is very important to the companies. The laboratory was well equipped, and the staff seemed very motivated and interested in sharing results.