Site: SORTEC Corporation
Tsukuba Research Laboratory
16-1 Wadai, Tsukuba-chi
Ibaraki 300-42, Japan
Date Visited: September 28, 1993
Report Author: H. Guckel
Takeshi Kishimoto Mitsubishi Electric
M. Nishimura Canon, Inc.
Mr. Takeshi Kishimoto explained the basic purpose, organization, and funding of SORTEC. SORTEC is a synchrotron facility that has a defined charter for the period 1986 to 1996. The charter involves ULSI lithography with a 1993 to 1995 goal of 0.15 mm linewidth with 0.04 mm overlay. For this purpose, it is funded at ¥14.3 billion over a ten-year period, and has a staff of eight administrators and twenty-two scientists. There are thirty membership companies. The synchrotron is a 1 GeV machine with a Linac injector into a booster synchrotron that feeds the storage ring. The storage ring is now operated at 500 mA beam current in a constant current mode, 1 to 2 percent accuracy, for more than twenty-five hours. The critical wavelength for the machine is 15.5 A. The machine supports users from Monday to Thursday, and uses Friday for maintenance and development.
The synchrotron SORTEC-1 can support eight beam lines; there are now four active beam lines. One of these is used with a Panasonic stepper, which has achieved alignment at 3s of 240 A. The exposure and alignment times are large. A second beam line is used with a Schwarzschild objective for projection lithography at 32:1 reduction. This system has produced 500 A line and spaces into PMMA.
In the ULSI area, photoresist tests are performed with 0.6 mm of AZ-PH 100 Hoechst negative resists. The mask is formed on a silicon nitride blank with 90 percent transmission at 6,330 A, which is fabricated by Oki Electric. The absorber is evaporated tantalum. This material when evaporated at an angle can produce linewidths to 800 A.
The visit to the facility included a tour of the booster synchrotron, the storage ring, and the stepper clean room area.
Discussions with Mr. Nishimura and Mr. Kishimoto included two main topics: the use of synchrotron radiation for high-aspect-ratio processing and the need for higher energy radiation for LIGA-like processing.
In the high-aspect-ratio area, Mr. Nishimura showed results of 0.7 mm lines and spaces in 5 mm thick photoresist. Mechanical failure in these geometries was assigned to the drying process after wet processing of the photoresist. This failure was related to surface tension forces, with additional complications due to spin drying.
In a very interesting discussion, deep X-ray lithography for micromechanics became the major topic. SORTEC researchers have attempted to expose LIGA-like photoresist layers in a very exploratory manner. Exposure times were long which is not surprising for this type of ring. Modification of the synchrotron via an insertion device is somewhat hampered by the fact that maximum straight section length is 2 meters.
Mr. Nishimura and Mr. Kishimoto indicated that they were aware of the attempts by the Fujita Corporation, a major Japanese Construction Company, to build and operate a high energy ring as a private enterprise, an effort that Fujita Corporation representatives had described earlier in a meeting at the Wisconsin Center for Applied Microelectronics in Madison, Wisconsin.
Atoda, N., et al. 1992. "Present Status of SORTEC SR Facility." Rev. Sci. Instrum. 63(1).
Kishimoto, T., et al. 1993. "Present Status of SORTEC 1-GeV 500 mA SR Source Facility." Paper presented at the 9th Symposium of Accelerator Science and Technology. Tsukuba, Japan.
Morigami, M., et al. 1993. "Exposure and Resist Process Condition Dependence of Replicated Pattern Accuracy in SR Lithography." SPIE Proceedings, Vol. 1924, March.