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Optimization of Plasma Photoresist Stripping With Low Mobile Ion Contamination Levels

IP.com Disclosure Number: IPCOM000102791D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 37K

Publishing Venue

IBM

Related People

Driscoll, TJ: AUTHOR

Abstract

A photoresist strip process on the Branson L3200 maximizes strip rates with respect to mobile ion charges as measured with Ni monitors.

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Optimization of Plasma Photoresist Stripping With Low Mobile Ion Contamination Levels

      A photoresist strip process on the Branson L3200 maximizes
strip rates with respect to mobile ion charges as measured with Ni
monitors.

      BY ALTERING THE PLASMA PARAMETERS ON A BRANSON L3200 TOOL,
mobile ion contamination is minimized while the resist strip rate is
maximized.  As the pressure is decreased, strip rates are increased,
however, at pressures of 3 Torr the mobile ion levels (Ni) jump two
orders of magnitude above a safe charge level of 109 ions/cm to 1011
ions/cm. Similarly, an increase in power leads to high strip rates
but power settings over 600 watts show the same sudden increase in Ni
levels. At these settings, the plasma has enough energy to rush past
the wafer to the pumping system which appears as a third electrode.

      EXPOSING A WAFER TO TEMPERATURES EXCEEDING 200 DEGREES C IS
also a concern for mobile ion levels. By preheating wafers to 190 to
320 degrees C, the strip rate is increased and a lower Ni level is
achieved. In an attempt to optimize the strip rate, the region of
safe Ni level can easily be surpassed. An optimized strip rate with a
safe Ni level follows:
                     1) 18 seconds of preheat.
                     2) 3500sccm of oxygen.
                     3) 400 watts of rf power.
                     4) A pressure of 4 Torr.

      Anony...