Keywords lithography, DUV, stepper, photoresist
Start Date: 01-NOV-88 / Duration: 36 months
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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.
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:
In the first year of the project, a prototype of the deep UV stepper was realised by ASM-L and tested, featuring 5x reduction all-quartz optics designed and manufactured by C. Zeiss. A new alignment system, operating through the lens with direct reference to the reticle, was successfully incorporated. Due to this improved feature (compared with competing systems) 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 micron with top surface imaging resist. All imaging specifications, including field uniformity and distortion, are within the requirements for sub-halfmicron lithography. The throughput of the system (30-40 wph) compares very favourably with the state of the art worldwide. An overlay accuracy of 60 nm has been realised.
Two 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 by Siemens research, 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.
Before the end of the project the prototype stepper developed had already been commercialised and sold worldwide. The negative resist developed by Hoechst is commercially available. The bilayer resist system (CARL) developed by Siemens is being utilised in one of the pilot lines of the company. Several subsystems and concepts developed in this project are being exploited in other types of steppers marketed by ASM-L.
Dr S. Wittekoek
NL - 5503 HN VELDHOVEN
tel: + 31/ 40-580800
fax: + 31/ 40-580333
telex: 59165 ASMLI NL
ASM-LITHOGRAPHY BV - NL - C
FRAUNHOFER GESELLSCHAFT - D - P
CEA - F - P
SIEMENS AG - D - P
UNIVERSITY OF EDINBURGH - UK - P
CARL ZEISS - D - P
SIEMENS AG -
SEMICONDUCTOR GROUP - D - P
NEDERLANDSE PHILIPS BEDRIJVEN BV - NL - P
HOECHST AG - D - P
DEEP-UV - 2048, December 1993
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html version of synopsis by Nick Cook