400-mm development on track
08/01/1998
400-mm development on track
K. Takada, director of Japan`s Super Silicon Crystal Research Institute (SSi), said the first 400-mm CZ crystal growth furnace was installed last October and a second one will be in place in 1999 at SSi`s facility in Isobe, Gunma Prefecture, on the site of Shin Etsu Handotai`s Isobe Plant. Some 400-mm silicon crystals (mechanical samples) have already been shipped to the wafer shaping division of SSi.Takada spoke at the 8th International Symposium on Silicon Materials Science and Technology (part of the Electrochemical Society meeting held in San Diego.
The organization continues to develop 400-mm wafers because its governmental funding was earmarked for 400-mm R&D and not other diameters, but Takada said SSi does not insist on the diameter. Sources at SSi indicate that many current and future fabrication and measurement tools will be capable of producing 450-mm diameter material, which is generally seen as the next wafer size beyond 300 mm.
According to Takada`s presentation, the present technical levels for each wafer shaping techniques are as follows:
Still at a basic research level: ductile mode grinding, diamond fly cutting, computer controlled polishing, plasma chemical vaporization machining, new shaping methods (such as elastic emission machining), float polishing, and ion-beam polishing. No processes are at an application research level. At a production technology development level are surface grinding and plasma-assisted chemical etching. At a mass production level are lapping, ELID (electrolytic in-process dressing), grinding, and conventional chemical mechanical polishing. The top technical challenges for 400-mm development outlined by Takada are:
reducing metal contamination on the wafer surface and in the epi layer,
reducing production costs,
decreasing the number of defects generated from particles during epi growth,
preventing slip formation,
improving wafer support methods
on tools,
achieving more uniform wafer heating,
improving gettering capabilities,
improving thickness variation over the whole wafer, and
developing thinner epitaxial layers and narrower transition regions.
SSi was established in March 1996 by Japan`s Ministry of International Trade and Industry, the Japan Key Technology Center, and seven Japanese silicon crystal manufacturers; plans call for the development of key technologies by January 2001. SSi has three labs: crystal growth, wafer shaping, and epitaxial growth. An R&D period of approximately five years with a budget of 13.4 billion yen ($115 million dollars) is planned.
In another presentation at the same meeting, H. Tsuchikawa, general manager of the Selete 300-mm development cooperative, Yokohama, disclosed that 300-mm volume production start-up by member companies will be one year behind schedule compared to its survey disclosed last December. Many of the member firms will skip pilot production and go directly to volume production, while the top one or two firms will install pilot production lines and then move to volume production, as shown in the previous survey. Throughput on 300-mm steppers is one of the key issues for 300-mm manufacturing, according to Tsuchikawa. - P.N.D.