The objective of ASPRO is to develop and qualify a high-throughput optical wafer-stepper with a resolution of 0.4 micron that can be used in the manufacturing processes of a wide range of silicon devices, ranging from high-volume memories to low-volume ASICs. By the mid-1990s the design rules for advanced device production will very likely be based on feature sizes of 0.5 to 0.35 microns, and the lithographic production capability resulting from this project will be essential for the effective exploitation of ESPRIT silicon technology developments.
The prototype stepper PAS 5500/100 has been built with the variable NA lens and variable coherence, aimed at the 0.35 micron semiconductor market. It has been fully characterized and is now commercially available. Improvements in illuminator efficiency and filter transmission have lead to higher stepper throughput as well as longer component lifetime.
The characteristics of the new stepper are:
0.4 micron resolution using i-line technology under production conditions;
large field size (30-32.5 mm);
variable numerical aperture, enabling trade offs between resolution and field size;
variable illumination coherence, enabling the evaluation of phase shift technology for geometries below 0.4 micron.
The targeted characteristics of the new stepper are:
- 0.4 micron resolution using i-line technology under production conditions
- large field-size (30-32.5 mm)
- variable numerical aperture, enabling trade-offs between resolution and field size
- variable illumination coherence, enabling the evaluation of phase shift technology for geometries below 0.4 micron.
Substantial user involvement is the key factor in successfully developing and applying advanced wafer fabrication equipment, and the new wafer-stepper will be evaluated under pilot production conditions at Centre Commun CNET SGS-Thomson, with the active participation of IBM and Philips. The wide range of different products manufactured by these partners will help the equipment manufacturer adapt the stepper for various roles. An equipment improvement and contamination reduction programme will be set up to facilitate this process.
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