To remain competitive, the European industry must have production capability for minimum details below 0.5 micron in the early 1990s, with the potential to extend down to 0.25 micron in the mid-1990s. Many production requirements must be addressed for this increased integration, but central among these is lithography and pattern transfer, since these strategic techniques define the minimum feature size and packing density of the new devices.
The overall objective of the project was to develop the equipment and basic processes required for a high-throughput pattern definition capability with 0.25 micron resolution that can be applied in the manufacturing process of all types of semiconductor devices. A modular concept was envisaged, which can be configured to meet the production needs of the full range of devices from high-volume memories to low-volume ASICs.
The objective of the project was to develop the equipment and basic processes required for a high throughput pattern definition capability with 0.25 micron resolution that can be applied in the manufacturing process of all types of semiconductor devices.
A prototype of the deep ultraviolet (UV) stepper was realized and tested, featuring 5x reduction all quartz optics. A new alignment system, operating through the lens with direct reference to the reticle, was incorporated. Due to this improved feature a high overlay accuracy, better than 125 nm, has been demonstrated.
The projection system has demonstrated resolution capability of 0.35 micron with single layer resist and 0.25 micorn with top surface imaging resist. All imaging specifications, including field uniformity and distortion, are within the requirements for subhalfmicron lithography. The thoroughput of the system compares favourably with the state of the art worldwide. An overlay accuracy of 60 nm has been realized.
2 single layer resist materials were under development. A negative resist has been developed with a resolution capability of 0.35 micron. In view of user requirements, the development concentrated on a positive tone material, which is now under test. In parallel, a bilayer resist system (CARL) has been developed, requiring more complex processing. Resolution of 0.25 micron has been demonstrated. Studies on how to integrate the deep UV wafer stepper with respect to environmental control (contamination, temperature) and interfacing (reticle management, automation) have been completed.
More specifically, this project aimed to develop the equipment, materials and techniques necessary for delineation of sub-halfmicron patterns. Included were a deep UV wafer stepper prototype, compatible photoresist systems (together with a study into the necessary resist processing), automation, and environmental aspects (with the goal of process integration in mind).
The project comprised three interdependent work packages covering the development of:
- a deep UV wafer stepper with excimer laser (248 nm) illumination
- deep UV photoresists compatible with 248 nm illumination
- automation and environmental engineering for the integration of equipment, especially of the deep UV stepper, in the clean-room.
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