Browse Prior Art Database

Method of Evenly Filling Isolation Trenches

IP.com Disclosure Number: IPCOM000043440D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 64K

Publishing Venue

IBM

Related People

Greschner, J: AUTHOR [+3]

Abstract

Onto a substrate, provided with trenches, a polyimide layer and a photoresist layer with a planar surface are deposited and etched at a photoresist/polyimide etch rate ratio of about 0.7 until the substrate surface is exposed and small elevations, that disappear upon baking, are left above the filled trenches. The described method is self-aligned. The first method steps are explained with reference to the cross-sectional view of Fig. 1. Onto substrate 1, provided with trenches 2, a polyimide coating 3 is spun and baked at about 125ŒC. Then, a photoresist layer 4 is spun onto polyimide coating 3, baked at about 95ŒC, and blanket-exposed at 300 to 400 mjoules. The structure (Fig. 1) thus obtained has a planar surface.

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Method of Evenly Filling Isolation Trenches

Onto a substrate, provided with trenches, a polyimide layer and a photoresist layer with a planar surface are deposited and etched at a photoresist/polyimide etch rate ratio of about 0.7 until the substrate surface is exposed and small elevations, that disappear upon baking, are left above the filled trenches. The described method is self-aligned. The first method steps are explained with reference to the cross-sectional view of Fig. 1. Onto substrate 1, provided with trenches 2, a polyimide coating 3 is spun and baked at about 125OEC. Then, a photoresist layer 4 is spun onto polyimide coating 3, baked at about 95OEC, and blanket-exposed at 300 to 400 mjoules. The structure (Fig. 1) thus obtained has a planar surface. This is followed by an etch step in an alkaline agent, such as potassium hydroxide or tetramethylammonium hydroxide, with the photoresist/polyimide etch rate ratio being about 0.7. This etch rate ratio causes the indentation in polyimide layer 3 (Fig. 1) to be converted into an elevation, according to Fig. 2, which shows an intermediate stage during etching. Fig. 3 illustrates the structure upon completion of etching, i.e., after exposure of the substrate surface. Finally, the polyimide is baked at about 400OEC, when the polyimide shrinks, so that the elevation, shown in Fig. 3, is planarized or converted into a small, negligible recess in the trench area (Fig. 4).

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