Improved Photo Alignment Using Trench Proximity
Original Publication Date: 1989-May-01
Included in the Prior Art Database: 2005-Jan-28
Through the placement of a deep trench adjacent to wafer alignment markers, precise photo mask alignment is achieved. Typical photo alignment schemes optically align a mask to a wafer. As shown in Fig. 1, the aligner looks through the photoresist-coated wafer to see the wafer alignment aids. Different photo levels utilize different types and thickness of resist, and some techniques utilize multi-level resist (MLR) patterns. In all of these schemes, the resist is planarized over the wafer surface and over alignment aids as well, adding to the complexity of mask/wafer alignment. The inherent error introduced by looking through the various types of resist schemes to see the alignment aids can be eliminated by exposing the alignment aids.