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Alignment Control on Test Site

IP.com Disclosure Number: IPCOM000062385D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Bonnet, J: AUTHOR

Abstract

On most commercially available step and repeat machines, alignment control of the cells at level N+1, with respect to the cells at level N, implies developing the wafer, to reveal the pattern at level N+1. The proposed method avoids this developing in certain conditions, and thus saves time.

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Alignment Control on Test Site

On most commercially available step and repeat machines, alignment control of the cells at level N+1, with respect to the cells at level N, implies developing the wafer, to reveal the pattern at level N+1. The proposed method avoids this developing in certain conditions, and thus saves time. The proposed method can be used in the following cases: (1) The level is critical as to the alignment but not as to the image size, (a) either because the image size has a relatively wide dispersion specification, (b) because the time of exposure is given by the preceding batch of wafers (the exposure duration causes the image size to vary), or (c) because the pattern sizes on the mask are calculated so as to be in an area of the image size curve in accordance with the exposure duration in which the image size shows small variations (small overexposure). (2) The level is critical as to the alignment and image size, but there are several reticles at this level. In this case, a normal test is carried out (i.e., with development), the alignment and overlay are checked, and for the second reticle, the alignment is tested by applying the following method. The details of the method are: (1) Exposing a test cell located under the pointing lenses on the test wafer. (2) Reloading the test wafer at the end of exposure. (3) Checking* the alignment and computing the corrections to be introduced into the program (Barbara Peck's method): if necessary, exposin...