193-mm Breakthrough at japans ASET group

06/01/1997

193-nm breakthrough at Japan`s ASET group

The Japanese government-funded Association of Super-Advanced Electronics Technologies (ASET) research co-op has successfully fabricated features ranging from 0.14 to 0.08 ?m using 193-nm lithographic techniques, and will begin transferring some of its research findings to the industry-funded SELETE research and development organization where 300-mm work and other development is taking place.

The transfer of intellectual property from ASET to SELETE comes earlier than anticipated; most government projects release their knowledge only after completion, and ASET will operate until 2000. However, Japanese sources said chipmakers were not inclined to wait for access to the information since much of it can be used in the development of 300-mm-compatible hardware. ASET is set up to look at long-term technology research; SELETE will work on nearer-term issues.

As part of the technology transfer, ASET`s 193-nm lithography engineering team has recently been transferred to SELETE in order to refine the technology for production use. SELETE now hopes to develop a prototype ArF laser-based system in 1998, and complete 193-nm process development by 2000. Member companies would then be able to start ramping production in the 2002-03 time frame.

ASET`s optical lithography work has been conducted at a leased Hitachi facility in Yokohama, the same location where SELETE`s 300-mm evaluation cleanrooms are located. The ASET team fabricated its 0.14 lines and spaces using a single-layer chemically enhanced photoresist, applied in a half-micron thick layer. Over 150 candidate resists have been evaluated. The exposure tool, from an unidentified supplier, has a 0.55 numerical aperture.

The group used half-tone phase shift masks to produce 0.12-?m lines and spaces, and Levenson-type phase shift masks to make 0.11-?m patterns. In another experiment, with a top-surface imaging process, 0.08-?m resolution was achieved.

ASET plans to continue researching and developing new types of 193-nm resists, which are generally seen as the biggest barrier to practical application of the new wavelength. A primary goal is to greatly enhance photosensitivity; a cooperative project with the Tokyo Institute of Technology is looking at acid-multiplied formulas.

The developments at ASET indicate that 193-nm technology may be extendible to the 0.10-?m device generation. This may be necessary if the wavelength is to be commercially viable, since there is a general perception that 193 will not be ready for use at 0.18 ?m. Thus, it will need to be brought into fabs at the 0.15-?m level. Extendibility beyond that point is critical if chipmakers are to amortize their acquisition costs, which will include the steep costs of development by stepper makers.

This is the first major accomplishment to be disclosed by ASET, which began work in 1996 on a variety of programs, including direct-write e-beam and x-ray lithography. Other efforts include advanced mask fabrication, plasma research, and particle control and cleaning. There are 22 member companies, including the top ten Japanese chip companies, IBM Japan, Texas Instruments Japan, and Merck. - P.N.D.