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Totally Sealed Spacer Structure

IP.com Disclosure Number: IPCOM000038174D
Original Publication Date: 1989-Dec-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Chesebro, DG: AUTHOR [+2]

Abstract

To preserve good silicon line-to-spacer properties while protecting against later process damage to spacer integrity, a spacer structure comprised of a first thin layer of silicon (SiO2), a second thicker silicon nitride (Si3N4) layer, and, following a light SiO2 etch, a third thin sidewall coating of Si3N4 is added. At a small processing cost increase, significant yield improvement is obtained with this process.

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Totally Sealed Spacer Structure

To preserve good silicon line-to-spacer properties while protecting against later process damage to spacer integrity, a spacer structure comprised of a first thin layer of silicon (SiO2), a second thicker silicon nitride (Si3N4) layer, and, following a light SiO2 etch, a third thin sidewall coating of Si3N4 is added. At a small processing cost increase, significant yield improvement is obtained with this process.

Referring to Fig. 1, polysilicon gate electrode 10 is disposed over gate dielectric 12 on substrate 14. This process begins with formation of a thin, conformal SiO2 layer 16 on all exposed silicon surfaces by chemical vapor deposition (CVD) followed by thermal oxidation. Next nitride 18 is conformally deposited by CVD, creating the cross section shown in Fig. 1.

Referring to Fig. 2, reactive ion etching is used to remove nitride 18 from horizontal surfaces. Next, a dip etch is used to remove any remaining oxide 16 on horizontal surfaces and to undercut the sidewall Si3N4 remnant of layer 18 as shown.

Referring to Fig. 3, a conformal layer 20 of Si3N4 having thickness equal to or slightly greater than the thickness of oxide layer 16 is deposited, filling undercut regions and covering all surfaces.

Referring to Fig. 4, RIE removal of layer 20 from horizontal surfaces results in the totally sealed sidewall spacer structure shown in this cross section.

Disclosed anonymously.

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