Fast Reticle Equipment for Europe

FREE - 5030

Keywords reticle, E-beam generator, resist

Start Date: 01-JUN-90 / Duration: 22 months

Objectives and Approach

The proliferation in the number of designs for ASICs, the increase in the number of functions per chip, and the decrease in the minimum feature size, necessitate faster turn-around times not only for IC prototypes, but also for mask fabrication tools. This, together with current demands and projections toward 0.3 micron minimum feature size, larger chips and higher placement accuracy, dictates the need for a new generation of tools for mask and reticle fabrication. The FREE project aimed at the development of a new electron-beam writing system for reticle fabrication that will answer the needs of the European IC industry for at least the next decade.

The target specifications of the system were a throughput of two reticles per hour, with a minimum feature size of 1.5 micron (5x reticle), and be capable of writing small test structures down to 0.2 micron. It was to attain a placement accuracy of 70 nm (0.07 micron) for 6" reticles and critical dimension (CD) tolerance of 50 nm (0.05 micron), both at 3 sigma. Two beam-writing strategies were followed: beam-shaping techniques (ELISA), in order to speed up the writing of large features, and a gaussian electron beam system (Leica Cambridge) with increased writing speed. Both basic systems already existed from the start, but required improvements in several areas.

Progress and Results

During the project the two machines were upgraded, as described below, to achieve the writing objectives:

Source: A thermal field emitter source giving a higher brightness than LaB6 and a 16 tungsten hairpin filament assembly with a long lifetime were designed and charcterised.
Column: The design of a new column associated with high-frequency detection (up to 25 MHz) was constructed and charcterised.
Data Processing: To achieve high throughput, the data rate handled by the pattern generator must be significantly improved. This was achieved by data compression techniques and higher electronic speeds for data transfer.
Automatic Loading: It was proposed to change the current batch-loading strategy to a serial, single-blank high-speed handler that would be compatible with other reticle fabrications tools. Suitable designs were prepared.
Resist Processing: Very high current densities are needed to achieve very high writing speeds. A very high sensitivity, short processing time and dry-etch compatible resist has been sysnthesised and characterised.

At the end of the project, evaluation of both the variable-shaped and gaussian beam machines against the ultimately desired specifications were performed, following the test procedure developed by the end user partners. Both machines showed significant improvement over the initial configurations, offering good prospects for the consolidation of a European system capable of competing in world markets. A comparison between them revealed their strong and weak points, and plans for further improvements were presented by both the manufacturers.

CONTACT POINT

Mr Jacques Perrocheau
ELISA SA
Avenue du Quebec, 18
ZA de Courtaboeuf BP 736
F - 91962 LES ULIS CEDEX
tel: + 33/ 1-69280809
fax: + 33/ 1-69280870

Participants

ELISA SA - F - C
LEICA CAMBRIDGE LTD - UK - P
SGS-THOMSON MICROELECTRONICS SRL - I - P
PHILIPS SEMICONDUCTORS - D - P
UNIVERSITY OF CAMBRIDGE - UK - P
NCSQ "DEMOKRITOS" - GR - P
TECHNISCHE UNIVERSITEIT DELFT - NL - P

FREE - 5030, December 1993

please address enquiries to the ESPRIT Information Desk

html version of synopsis by Nick Cook