Browse Prior Art Database

Trench-Forming Process

IP.com Disclosure Number: IPCOM000042861D
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 58K

Publishing Venue

IBM

Related People

Dreves, RF: AUTHOR [+3]

Abstract

A trench-forming process is provided which uses a lift-off technique with a non-erodible material to form a mask having vertical sidewalls which may be used for reactive ion etching to produce a narrow trench in a semiconductor substrate, e.g., silicon. The process may be better understood by referring to Figs. 1 through 4 wherein a semiconductor substrate 10 has formed thereon successive layers of grown silicon dioxide 12, silicon nitride 14 and pyrolytically deposited silicon dioxide 16. Each of the layers 12 and 14 may have a thickness of approximately 850 angstroms, and layer 16 may have a thickness of 0.64 micrometer. Over layer 16 there is deposited a layer of photoresist which is patterned as segment 18 to define a trench location.

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Trench-Forming Process

A trench-forming process is provided which uses a lift-off technique with a non- erodible material to form a mask having vertical sidewalls which may be used for reactive ion etching to produce a narrow trench in a semiconductor substrate, e.g., silicon. The process may be better understood by referring to Figs. 1 through 4 wherein a semiconductor substrate 10 has formed thereon successive layers of grown silicon dioxide 12, silicon nitride 14 and pyrolytically deposited silicon dioxide 16. Each of the layers 12 and 14 may have a thickness of approximately 850 angstroms, and layer 16 may have a thickness of 0.64 micrometer. Over layer 16 there is deposited a layer of photoresist which is patterned as segment 18 to define a trench location. The photoresist segment 18 is formed with a reentrant slope in a known manner so that its lower portion or base has a smaller width than its upper portion. A layer of aluminum 20 having a thickness of approximately 2000 angstroms is then evaporated over photoresist segment 18 and over portions of silicon dioxide layer 16, as indicated in Fig. 1. The photoresist segment 18 is lifted off along with the portion of the aluminum layer 20 disposed thereon, as shown in Fig. 2. With the use of, e.g., carbon tetrafluoride (CF4), an opening 22 is formed in layers 16, 14 and 12 by reactive ion etching techniques, providing a zero etch bias, as indicated in Fig. 3. The remaining portion of the aluminum layer is strip...