8TA

A vapor prime and image reversal system is a front-end wafer processing tool used around photolithography. A vapor prime process prepares wafer surfaces for photoresist coating by promoting adhesion. An image reversal process changes the behavior of a positive resist so that a negative image can be formed.

The YES 8TA supports 8 cassettes of 5-6 in. wafers, or 2 cassettes of 8 in. wafers, or 1 cassette of 12 in. wafers. The YES 8TA has a cleanliness specification of less than 5 x 1 micron particles per 6-in. wafer. The YES 8TA has a throughput of 2 1/2 loads per hour for image reversal processing. The YES 8TA has a maximum temperature of 160°C, and the image reversal process is specified at 90°C.^[2]

Vapor prime and image reversal equipment sits in the lithography track area between wafer cleaning or dehydration preparation and photoresist pattern transfer. Vapor priming is used before resist coat steps to improve adhesion. Image reversal processing is used after resist exposure within a sequence that enables negative-tone patterning from a positive resist platform.

Image reversal reverses the action of positive resist so that negative images can be formed. Image reversal allows negative imaging with the resolution and ease of processing associated with positive resist. Image reversal also allows variations of photoresist sidewall slope for higher resolution or lift-off profiles. The most common user was the mask maker. The technique is also used where small-geometry metal lines and lift-off processing are required, including gallium arsenide, lithium niobate, indium phosphide, and some silicon applications.^[2]