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PELLICLE MASK PROTECTION FOR I:1 PROJECTION ALIGNERS

IP.com Disclosure Number: IPCOM000005448D
Original Publication Date: 1982-Jan-01
Included in the Prior Art Database: 2001-Oct-10
Document File: 2 page(s) / 88K

Publishing Venue

Motorola

Related People

John Lent: AUTHOR

Abstract

One major problem associated with 1:l projection printing is defects caused by airborne COntamina- hon. This contamination problem becomes more serious as the printed geometries become Smaller, especially as the ratio of geometry area versus particulate area approaches 1. Unfortunately, the smaller particulates are harder to see and remove.

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&'OyaRaLA Technical Developments Volume 2 January 1982

PELLICLE i'dASK PROTECTION FOR I:1 PROJECTION ALIGNERS By John Lent

   One major problem associated with 1:l projection printing is defects caused by airborne COntamina- hon. This contamination problem becomes more serious as the printed geometries become Smaller, especially as the ratio of geometry area versus particulate area approaches 1. Unfortunately, the smaller particulates are harder to see and remove.

   A number of methods, e.g., cover glass coatings, have been used in an attempt to solve this problem. Unfortunately, all of the methods thus far have had serious drawbacks when used with projection print- ing. The only method which comes close to achieving elimination of particulate contamination is single mask insertion. This method, while producing good results, is very cumbersome, difficult, and expensive to implement. The ability to control such a method is very difficult at best in a production environment.

   Recently, however, an optical element has become available which has characteristics which allow it to be used in the semiconductor industry for mask protectlon. This element is called a Pelticle. ESSential- ly, a pellicle is a membrane thin enough to be optically transparent, strong enough to be stretched across a supporting ring sufficiently large to cover the entire 4" printable array of a 5" mask, durable enough to withstand cleaning and handling, stable enough to retain its shape over long periods of time, and inex- pensive enough to be cost effective.

   Figure 1, combined with some basic assumptions, demonstrates how a pellicle can protect a mask. It makes the particulate stand far enough away from the mask so that the ratio of the area Of the particulate with respect to the ar...