Browse Prior Art Database

Image Alignment for Semiconductor Processing

IP.com Disclosure Number: IPCOM000093020D
Original Publication Date: 1967-Apr-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Schiavone, RN: AUTHOR

Abstract

In the manufacture of monolithic type microcircuits, patterns are conventionally processed onto a semiconductor material by use of a photocontact printing method. Alignment between the first pattern and all succeeding patterns is performed manually with the aid of optical magnification.

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Image Alignment for Semiconductor Processing

In the manufacture of monolithic type microcircuits, patterns are conventionally processed onto a semiconductor material by use of a photocontact printing method. Alignment between the first pattern and all succeeding patterns is performed manually with the aid of optical magnification.

This method is for the automatic precision alignment between the first pattern processed on a semiconductor circuit and all succeeding patterns. The principle of alignment provides, as in A, the physical location of a PN junction which is processed from a first pattern. Junction 1 is located by illuminating it with a narrow slit of light 2 which traverses the junction.

With PN junction 1 in reverse bias, a voltage output V(o) is obtained depending upon the position of the light slit. This function is shown in B. Junction 1 is defined when the slope of this function is zero. It can also be defined as a point at which the voltage is maximum. The application of this principle to this system is shown in C.

Such system includes light source 3, filter 4, and lens system 5 for projecting a pattern from photoplate 7 to semiconductor wafer 6. Photoplate 7 carries a pattern which is precisely related to rectangular transparent regions 8, 9, and 10. These regions are projected as slits 8', 9', and 10' on surface 13 of wafer 6.

Proper selection of filter 4 insures that the frequency of light impinging on the photoresist, coated on wafer 6, passes through the resist without poly...