Methods of minimizing etch undercut and providing clean metal liftoff
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United States of America Patent
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Jun 14, 2011
Grant Date -
Apr 30, 2009
app pub date -
Oct 30, 2007
filing date -
Oct 30, 2007
priority date (Note) -
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Abstract
A method of minimizing etch undercut and providing clean metal liftoff in subsequent metal deposition is provided. In one embodiment a bilayer resist mask is employed and used for etching of underlying substrate material and subsequent metal liftoff. In one embodiment, the top layer resist such as positive photoresist which is sensitive to selected range of energy, such as near UV or violet light, is first patterned by standard photolithography techniques and resist development in a first developer to expose portion of a bottom resist layer which is sensitive to a different selected range of energy, such as deep UV light. The exposed portion of the bottom layer resist is then removed by anisotropic etching such as oxygen reactive ion etching using the top layer resist as the etch mask to expose portion of the underlying substrate. This minimizes the undercut in the bottom resist around the top photoresist opening. The resultant patterned bilayer resist stack is then used as the etch mask for the subsequent etching of the exposed portion of the underlying substrate material. Because there is no undercut in the bottom resist layer, the etch undercut in the substrate material is also minimized relative to the edges of the top photoresist opening.
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