Method of maintaining photolithographic precision alignment after wafer bonding process
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United States of America Patent
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Nov 22, 2005
Grant Date -
Jan 20, 2005
app pub date -
Nov 28, 2003
filing date -
Jul 18, 2003
priority date (Note) -
Expired
status (Latency Note)
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Abstract
A method of maintaining photolithographic precision alignment for a wafer after being bonded, wherein two cavities are formed at the rear surface of a top wafer at the position corresponding to alignment marks made on a bottom wafer. The depth of both cavities is deeper than that of a final membrane structure. The top wafer is then bonded to the bottom wafer which already has alignment marks and a microstructure. This bonded wafer is annealed to intensify its bonding strength. After that, a thinning process is applied until the thickness of the top wafer is reduced to thinner than the cavity depth such that the alignment marks are emerged in the top wafer cavities thereby serving as alignment marks for any exposure equipment.
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