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Protection of Photoresist Used as a Sputter Etch Mask

IP.com Disclosure Number: IPCOM000088732D
Original Publication Date: 1977-Jul-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Krongelb, S: AUTHOR

Abstract

When photoresist is used as a mask for sputter-etching, photoresist is eroded. During etching in a nonreactive discharge (e.g., pure argon), the resist etch rate is relatively predictable, and one can compensate to some extent for eroded photoresist. However, when the discharge is first turned on, it is virtually impossible to avoid the presence of oxygen in the plasma since the discharge provides an effective clean-up of the water vapor and oxygen adsorbed on the walls of the chamber. It takes several minutes for the discharge to stabilize to a pure, nonreactive state. During this time, the photoresist is eroded rapidly and uncontrollably. (Note that exposure to an oxygen containing plasma is a widely used, effective means of stripping photoresist.

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Protection of Photoresist Used as a Sputter Etch Mask

When photoresist is used as a mask for sputter-etching, photoresist is eroded. During etching in a nonreactive discharge (e.g., pure argon), the resist etch rate is relatively predictable, and one can compensate to some extent for eroded photoresist. However, when the discharge is first turned on, it is virtually impossible to avoid the presence of oxygen in the plasma since the discharge provides an effective clean-up of the water vapor and oxygen adsorbed on the walls of the chamber. It takes several minutes for the discharge to stabilize to a pure, nonreactive state. During this time, the photoresist is eroded rapidly and uncontrollably. (Note that exposure to an oxygen containing plasma is a widely used, effective means of stripping photoresist.) Furthermore, the edge profile of the photoresist, which has a direct bearing on the profile of the etched pattern also is altered rapidly during this period.

The photoresist can be protected from the initially reactive plasma by evaporating a thin protective layer of metal over the entire structure after the photoresist pattern has been formed. During the initial minutes of etching, the photoresist is shielded by the evaporated layer, and the reactive gases act only on it. By the time the evaporated layer has been removed to expose the photoresist, the oxygen evolved from the chamber will have been exhausted and desired conditions established. Materials such as al...