Skip to sections.
Dec. 1997
Nikon Corporation announced that the company starts taking orders in winter 1997,
for NSR-S202A, the second-generation of Nikon's tep-and-Repeat KrF Excimer Scanning Systems, and taking orders in spring 1998,
NSR-S102B, the Step-and-Repeat i (I)-line Scanning System.
NSR-S202A, which employs KrF excimer laser (wavelength 248 nm) for the larger 25 x 33 mm exposure field, has achieved sub-quarter micron resolution. NSR-S202A has also improved the throughput by 40% compared to its predecessor NSR-S201A.
NSR-S102B using i(I)-line (wavelength 365 nm) for its light source is concurrently offered to take an utmost advantage of the two types of machines by mix-and-matching.
Development Background
Technological innovation for ultra large scale integrated (ULSI) circuits has been rapidly shrinking the circuit geometries. The 64MDRAMs are already in the volume production stage and engineers and developers are now committed to bring the 256MDRAMs up to the volume production stage.
In response to the industry's move toward higher resolution and larger exposure area, Nikon has been developing various exposure tools such as the I-line steppers for the 64MDRAM volume production and the KrF excimer laser steppers for the 64MDRAM volume production and the 256MDRAMs development.
These steppers were designed to expose a 22 x 22 mm area in maximum by a step-and-repeat method, however, many people started to voice their concerns that the 22 x 22 mm exposure area will no longer cover even a single chip size as the industry advances to the 256MDRAM era. Productivity is another essential issue: one exposure should be able to print multiple number of chips.
To satisfy the demands for both smaller geometry and higher productivity, Nikon developed the world's first 256M DRAM volume production exposure system, NSR-S201A, Step-and-Repeat KrF Excimer Scanning System.
Since Nikon started taking orders in 1995-04, this system has been receiving high reputation.
NSR-S202A has improved the throughput by 40% over the previous model NSR-S201A by enhancing the respective element performance.
NSR-S102B, Step-and-Repeat i(I)-line Scanning System, was launched to effectively reduce the cost of ownership by mix-and-matching with NSR-S202A.
Main Features of NSR-S202A
Employment of KrF excimer laser as a light source and the lens scanning system enables NSR-S202A to achieve sub quarter micron resolution and the large 25 x 33 mm exposure area to comfortably accommodate the needs to mass produce 256MDRAMs and advanced microprocessors (MPUs).
Throughput improvement was contributed by two major factors: the wafer stage using the air guide linear motor is able to run at a faster speed; the new KrF excimer laser unit shortens the exposure time. The alignment time has also been shortened by optimizing the alignment system. NSR-S202A boasts the throughput of 80 wafers per hour in terms of 8" (200mm) wafer.
Newly developed wafer table and the enhanced alignment optical system attained 10% improvement in alignment accuracy over the previous model.
Main Features of NSR-S102B
Employment of i(I)-line as a light source and the lens scanning system enables NSR-S102B to achieve 0.35 micron or better resolution and the large 25 x 33 mm exposure area to print non-critical layers of the 256M DRAMs patterns and the next-generation advanced microprocessors (MPUs) patterns.
As in NSR-S202A , the new air guide linear motor stage and the enhanced alignment system improved the throughput and alignment accuracy.
System Overview
Scanning stages are mounted on both reticle and wafer sides ( 1), 2)) and moved simultaneously to obtain the large exposure field (25 x 33 mm).
The exposure light coming through the conventional illumination system passes the rectangular exposure slit (3)) to expose a 1:4 reduction patterns onto the wafer ( 6)).
Main Specifications:
| NSR-S202A | NSR-S102B | |
|---|---|---|
| Resolution | 0.25 micron or better | 0.35 micron or better |
| Light source | KrF excimer laser (248nm) | i(I)-line (365 nm) |
| Reduction ratio | 1:4 | |
| Exposure area | 25 x 33 mm | |
| Alignment accuracy | 45 nm or better | |
| Throughput (8 in. (200mm) wafer) | 80 wafers/hr. | 82 wafers/hr. |
