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Focus Matrix Technique for a Projection Printer

IP.com Disclosure Number: IPCOM000060664D
Original Publication Date: 1986-Apr-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Barr, RL: AUTHOR [+2]

Abstract

Precise Z-axis mask location for best focus in the wafer image plane is found by utilizing a single test object on a product mask to create a matrix of images on a test wafer from varying Z-axis locations of the mask. The matrix is formed by stepping the test wafer or mask to several positions in the X-Y plane, and making an exposure after setting the mask to a predetermined, new Z location at each X-Y position on the wafer. The matrix of images on the test wafer is confined to an area sufficiently small that the entire matrix is within the field of view of the evaluation microscope.

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Focus Matrix Technique for a Projection Printer

Precise Z-axis mask location for best focus in the wafer image plane is found by utilizing a single test object on a product mask to create a matrix of images on a test wafer from varying Z-axis locations of the mask. The matrix is formed by stepping the test wafer or mask to several positions in the X-Y plane, and making an exposure after setting the mask to a predetermined, new Z location at each X- Y position on the wafer. The matrix of images on the test wafer is confined to an area sufficiently small that the entire matrix is within the field of view of the evaluation microscope.

The usual test object comprised of vertical and horizontal bars is included in several regions of a product mask. Sufficient opaque region surrounds the test object in the mask that desired number of images, comprising the matrix of images, may be formed on the test wafer without double exposure.

For more detailed evaluation of best focus at many points over the wafer area, a test object comprised of a single small diameter (e.g., 1.5 micron) hole is placed in the kerf region of each chip area in the product mask. This test object requires a much smaller opaque region surrounding it and results in the ability to create a larger matrix of test images which are within the field of view of the evaluation microscope.

Evaluation of best image quality within the matrix or matrices is performed in the usual manner, by visual examination of th...