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Substrate Contact for Tapered Polysilicon Filled Trench

IP.com Disclosure Number: IPCOM000043296D
Original Publication Date: 1984-Aug-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 60K

Publishing Venue

IBM

Related People

Bhatia, HS: AUTHOR [+3]

Abstract

A process, with some alternate steps, is described which provides contact to the semiconductor substrate using a tapered polysilicon trench technology. The substrate is, for example, p- silicon 1 with n+ layer 2 and n epi layer 3. The substrate is first oxidized to form a SiO2 layer 4, and a Si3N4 layer 5 is reactive ion etched (RIE) in CF4 and the photoresist is removed. The exposed oxide is wet etched in 7:1 buffered hydrofluoric acid (BHF). The exposed silicon is first etched using an anisotropic alkaline wet etch to form a tapered wall trench 6. This trench is then extended to the p- silicon 1 by RIE in a CCl4/O2 mixture, giving the configuration shown in Fig. 1. At this point either of two process sequences may be followed. In the first sequence, about 2000 ˜ of silicon is isotropically etched.

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Substrate Contact for Tapered Polysilicon Filled Trench

A process, with some alternate steps, is described which provides contact to the semiconductor substrate using a tapered polysilicon trench technology. The substrate is, for example, p- silicon 1 with n+ layer 2 and n epi layer 3. The substrate is first oxidized to form a SiO2 layer 4, and a Si3N4 layer 5 is reactive ion etched (RIE) in CF4 and the photoresist is removed. The exposed oxide is wet etched in 7:1 buffered hydrofluoric acid (BHF). The exposed silicon is first etched using an anisotropic alkaline wet etch to form a tapered wall trench 6. This trench is then extended to the p- silicon 1 by RIE in a CCl4/O2 mixture, giving the configuration shown in Fig. 1. At this point either of two process sequences may be followed. In the first sequence, about 2000 ~ of silicon is isotropically etched. This moves the tapered wall 6 back so it will not be affected by the next step, which is to implant nitrogen in the bottom of the trench, forming Si3N4 . The trench sidewalls, including the tapered walls, are then oxidized. The Si3N4 is then wet etched from the bottom of the trench, and boron is implanted to act as a channel stopper. In the alternate sequence, the entire trench is oxidized 7 and a Si3N4 layer 8 is deposited. Photoresist 9 is applied and patterned. A blanket layer of oxide 10 is deposited by plasma enhanced chemical vapor deposition, resulting in the structure shown in Fig. 2. The plasma enhanced...