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New Cassettes for Tank Processing

IP.com Disclosure Number: IPCOM000120012D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 159K

Publishing Venue

IBM

Related People

Belloto, D: AUTHOR [+4]

Abstract

For the etching, developing, stripping and lift-off steps in tanks, the wafers are processed in cassettes. The wafer area which is between slots is very often affected by: - Local overetching of the chips - Redeposited particles - Bad removal of the resist or polyimide

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New Cassettes for Tank Processing

      For the etching, developing, stripping and lift-off steps
in tanks, the wafers are processed in cassettes. The wafer area which
is between slots is very often affected by:
          - Local overetching of the chips
          - Redeposited particles
          - Bad removal of the resist or polyimide

      For lift-off processes, the particles are aluminum residues
which damage lands creating the so-called micromechanical damage.
This last defect is a real reliability concern.

      To reduce these detrimental effects and have no particles or
contamination products on the wafers, the flow of the solution
between the slots and the wafers must be increased. For such a goal,
a new design of cassettes is proposed. According to the present
disclosure the cassettes are provided with reduced slots and the
bottom of the slots is opened.

      The photograph shows the design of an improved cassette. With
such cassettes for polyimide etching at the terminal via layer, the
percentage of rejected chips was reduced from the range 0.4-0.3% to
0.1-0.2%.

      For lift-off, the rework was also reduced from 15% to 5%.