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Etching Technique for Minimum Undercutting

IP.com Disclosure Number: IPCOM000076274D
Original Publication Date: 1972-Feb-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Elijah, LM: AUTHOR [+4]

Abstract

In large scale semiconductor integration, using silicon or other substrates, increased packing density of devices on a chip has placed stringent tolerances on photolithographic processes involving etching. Lateral undercutting which normally is encountered, therefore, must be reduced to a minimum. The following technique achieves optimum results. The method provides the following steps: (a) Coat a clean dry semiconductor wafer with suitable surfactant and negative type photoresist, followed by an elevated temperature cure; (b) Expose with appropriate mask; (c) Develop, bake or cure; (d) Etch with appropriate reagents to a shallow predetermined depth less than finally required;

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Etching Technique for Minimum Undercutting

In large scale semiconductor integration, using silicon or other substrates, increased packing density of devices on a chip has placed stringent tolerances on photolithographic processes involving etching. Lateral undercutting which normally is encountered, therefore, must be reduced to a minimum. The following technique achieves optimum results. The method provides the following steps: (a) Coat a clean dry semiconductor wafer with suitable surfactant and negative type photoresist, followed by an elevated temperature cure; (b) Expose with appropriate mask; (c) Develop, bake or cure; (d) Etch with appropriate reagents to a shallow predetermined depth less than finally required;

(e) Heat for predetermined time interval and temperature to flow photoresist, thus protecting sidewalls, as shown at 1 in Fig. 1, and continue the etching.

In special cases, a second and even third repeat of steps (d) and (e) may be necessary to produce a reflow as shown in Fig. 2. Fig. 3 illustrates the completed, etched opening. Reference numeral 2 of the drawing is silicon. This reflow technique has useful application when utilized with materials of varying compositions and composites.

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