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REACTIVE ION ETCHING OF POLYSILICON/OXIDE USING CCl2F2 + H2 GAS MIXTURES

IP.com Disclosure Number: IPCOM000040629D
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Dobuzinsky, DM: AUTHOR [+2]

Abstract

A highly selective, residue free and anisotropic etching process for polysilicon/silicon dioxide used in the fabrication of VLSI gate electrodes is described. When polysilicon is used for VLSI gate electrodes, etching is important in the definition of these very small structures. Technology advances now dictate the need for vertical gate profiles and selectivity between the polysilicon gate material and the thin gate oxide used. Dry etching with CCl2F2 + NH3 gas mixtures frequently leaves a polymer formation on wafer surfaces and inside the reactive ion etch (RIE) chamber. The degree of anisotropic etching of polysilicon and the selectivity over oxides is a function of the NH3 flow rate ratio variations, resulting in a narrow process window which is difficult to use in a manufacturing environment.

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REACTIVE ION ETCHING OF POLYSILICON/OXIDE USING CCl2F2 + H2 GAS MIXTURES

A highly selective, residue free and anisotropic etching process for polysilicon/silicon dioxide used in the fabrication of VLSI gate electrodes is described. When polysilicon is used for VLSI gate electrodes, etching is important in the definition of these very small structures. Technology advances now dictate the need for vertical gate profiles and selectivity between the polysilicon gate material and the thin gate oxide used. Dry etching with CCl2F2 + NH3 gas mixtures frequently leaves a polymer formation on wafer surfaces and inside the reactive ion etch (RIE) chamber. The degree of anisotropic etching of polysilicon and the selectivity over oxides is a function of the NH3 flow rate ratio variations, resulting in a narrow process window which is difficult to use in a manufacturing environment. Excellent etch rate selectivity ratios can be obtained when etching polysilicon/oxide if the RIE plasma gas mixture is CCl2F2 + H2 . No polymer residue is left on the wafer or RIE chamber surfaces, and variations in H2 flow rates only effect the etch rate ratio, i.e., a large operating window, while maintaining good anisotropic polysilicon etch profiles. The typical RIE process for polysilicon/oxide materials utilizes a parallel plate reactor operating at a frequency of 13.56 MHz, a power density of approximately 0.1 watt/cm2 and a vacuum of 100 mTorr. The figure shows the etch rate ratio variation...