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Self-Aligned Process for Forming Polysilicon Contacts Over ROX or Gate Oxide

IP.com Disclosure Number: IPCOM000040600D
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Barber, J: AUTHOR [+2]

Abstract

This article describes a process for making self-aligned polysilicon contacts which allow for a significant increase in circuit density. This process is compatible with standard CMOS FET processes. Step 1 - Following the formation of the recessed oxide (ROX) regions of a semiconductor wafer 12, a layer of polysilicon 14 is deposited, followed by the growth of a thin oxide layer 16. The polysilicon layer is ion implanted with phosphorus. Step 2 - A layer of titanium 18 is evaporated on the polysilicon in a conformal manner. Step 3 - The polysilicon layer 14 is lithographically defined and dry etched using BCl3, HCl/Cl2, and HCl etch gasses in separate etch steps. The resulting device cross-section is shown in Fig. 1. Step 4 - Referring to Fig.

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Self-Aligned Process for Forming Polysilicon Contacts Over ROX or Gate Oxide

This article describes a process for making self-aligned polysilicon contacts which allow for a significant increase in circuit density. This process is compatible with standard CMOS FET processes. Step 1 - Following the formation of the recessed oxide (ROX) regions of a semiconductor wafer 12, a layer of polysilicon 14 is deposited, followed by the growth of a thin oxide layer
16. The polysilicon layer is ion implanted with phosphorus. Step 2 - A layer of titanium 18 is evaporated on the polysilicon in a conformal manner. Step 3 - The polysilicon layer 14 is lithographically defined and dry etched using BCl3, HCl/Cl2, and HCl etch gasses in separate etch steps. The resulting device cross-section is shown in Fig. 1. Step 4 - Referring to Fig. 2, a layer of photoresist 20 is applied, exposed and developed to form a block polysilicon contact mask. The photoresist covers all areas where polysilicon contacts are to be placed. Step 5 - The titanium 18 left uncovered by the photoresist contact mask is etched down to the thin oxide layer 16 remaining on the surface (Fig. 3). Step 6 - Referring to Fig. 4, oxide spacers 22 are defined on the sides of the polysilicon 14 and titanium 18 and, the diffusion regions 24, 26 are implanted as customary. Step 7 - A thin layer of oxide 28 is applied followed by a thicker planarizing layer of borophosphosilicate glass (BPSG) 30. The BPSG 30 is reflowed, and...