Method to Eliminate Second Order Alignment Errors
Original Publication Date: 1988-Aug-01
Included in the Prior Art Database: 2005-Feb-15
By aligning a mask level to a coincident enclosed area of two prior mask level images, second order or additive alignment errors are reduced. Referring to Fig. 1, an image of a first level conductive line 2 is the reference to which an image of a square via hole 4 is misaligned by a maximum error in both x and y directions. A coincident enclosed area 6 of the two images 2 and 4 is the shaded region in Fig. 1. An image of a second level conductive line 8 is shown in perfect alignment with coincident enclosed area 6. In Fig. 2, an image 8B of the second level conductive line is shown misaligned a maximumum in both x and y directions relative to area 6 of Fig. 1. Resultant area of contact of line 2 to line 8B is shaded area 10.