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Circuit to Automate Stripping of Photoresist in Plasma Machines

IP.com Disclosure Number: IPCOM000074670D
Original Publication Date: 1971-May-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Nerou, JP: AUTHOR [+3]

Abstract

The semiconductor industry includes considerable use of photolithographic steps. Generally these steps are critical and comprise the application, exposure, development and removal of organic photoresist material from silicon wafers. A new process for removing or stripping off these organic photoresist compounds, includes the use of a plasma machine to permit the exposure of the wafer to a RF gas plasma of oxygen. When submitted to the contact of plasma oxygen, the photoresist compounds burn and from the oxidation new chemical compounds result, like carbon dioxide and water vapor, which have to be removed.

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Circuit to Automate Stripping of Photoresist in Plasma Machines

The semiconductor industry includes considerable use of photolithographic steps. Generally these steps are critical and comprise the application, exposure, development and removal of organic photoresist material from silicon wafers. A new process for removing or stripping off these organic photoresist compounds, includes the use of a plasma machine to permit the exposure of the wafer to a RF gas plasma of oxygen. When submitted to the contact of plasma oxygen, the photoresist compounds burn and from the oxidation new chemical compounds result, like carbon dioxide and water vapor, which have to be removed.

In the present case before removing, the partial pressure of these different gases (which are characteristic of the oxidation) are measured. Since the variation of pressure is thus directly connected to the combustion, it permits continuous monitoring of the combustion products.

Accordingly at predetermined times, the pressure will be measured, both with RF and without RF. The difference between these two pressures indicates the state of the photoresist being burned. When these pressures are identical, it means the end of the combustion cycle and the wafer may be then removed from the system. This solution provides savings in time and costs, consumption of high-purity chemical products and, more important, avoids oxidation of the exposed silicon wafer zones.

In operation, it is necessary to detect whether a voltage difference delta V occurs between two designated times T1 and T2. delta V r...