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Method of Measuring Overhanging Photoresist Lift Off Patterns in Scanning Electron Microscope

IP.com Disclosure Number: IPCOM000048981D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 80K

Publishing Venue

IBM

Related People

Hawks, SW: AUTHOR [+2]

Abstract

Fig. 1 shows a profile of a photoresist lift-off pattern used to form metal lands in VLSI (very large-scale integrated) circuits. The profile of the photoresist is used to determine the amount of overhang and how much of the toe sticks out, and is important in characterizing how well the lift-off operation will be performed. Typically, a monitor wafer (blank wafer with photoresist pattern) and a product wafer are sent for SEM (Scanning Electron Microscope) micro photos on a regular basis. The wafer is fractured through the pattern on a single chip, and an SEM micrograph is made. From the amount of overhang and how much the toe sticks out from the edge, an estimate of the lift-off capability can be made.

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Method of Measuring Overhanging Photoresist Lift Off Patterns in Scanning Electron Microscope

Fig. 1 shows a profile of a photoresist lift-off pattern used to form metal lands in VLSI (very large-scale integrated) circuits. The profile of the photoresist is used to determine the amount of overhang and how much of the toe sticks out, and is important in characterizing how well the lift-off operation will be performed. Typically, a monitor wafer (blank wafer with photoresist pattern) and a product wafer are sent for SEM (Scanning Electron Microscope) micro photos on a regular basis. The wafer is fractured through the pattern on a single chip, and an SEM micrograph is made. From the amount of overhang and how much the toe sticks out from the edge, an estimate of the lift-off capability can be made. This method consumes product and monitor wafers, takes considerable time, has some inaccuracies because only the edge of the fracture can be measured, and the wafer is destroyed so the lift-off cannot be checked on that wafer.

If a top view of the wafer is observed in the SEM, a bright band may be seen along each side of the photoresist pattern. This is the overhang region (Fig. 2). A line scan may be done of the same region, and the width of the overhang and amount that the toe sticks out may be measured. These measurements may be made at any location desired (not just at a fracture site), and the wafer may be processed and the results compared to the line scan measureme...