Browse Prior Art Database

Overlay Distortion Evaluation of Projection Printers

IP.com Disclosure Number: IPCOM000041964D
Original Publication Date: 1984-Mar-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Ananthakrishnan, RB: AUTHOR [+3]

Abstract

A simple and fast technique for the evaluation of the distortion and magnification error in a projection printer is disclosed. As the dimensions of integrated circuit features decrease in size, the accurate alignment and printing of overlay images into photoresist in sequential mask steps becomes critical. The distortions inherent in any optical projection system used to print an image will, however, change with time and thus must be continually monitored and corrected for. The distortion including magnification errors, for a particular projection system, are monitored by superimposing developed mask patterns in an oxide layer on a silicon wafer from a standard machine and the machine under test.

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Overlay Distortion Evaluation of Projection Printers

A simple and fast technique for the evaluation of the distortion and magnification error in a projection printer is disclosed. As the dimensions of integrated circuit features decrease in size, the accurate alignment and printing of overlay images into photoresist in sequential mask steps becomes critical. The distortions inherent in any optical projection system used to print an image will, however, change with time and thus must be continually monitored and corrected for. The distortion including magnification errors, for a particular projection system, are monitored by superimposing developed mask patterns in an oxide layer on a silicon wafer from a standard machine and the machine under test. Typically, the monitoring test involves printing the overlay images on a large number of wafers in order to statistically characterize the distortion. The new technique involves the printing of the image of a test mask into an oxide layer on a silicon wafer on the projection printer under test. The test mask has therein a pattern comprising a number of elements distributed across the mask which are sufficient to determine the distortion of the particular projection printer. The test mask pattern and the printed pattern in the oxide layer are then measured using a precision measuring system, such as a Nikon Model 2I Measuring Machine. For both the mask and the printed pattern the distance between elements and the sizes...