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Polysilicon Dry Etching Using Reactive Ion Etching and Plasma Etching

IP.com Disclosure Number: IPCOM000041382D
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Dillinger, TE: AUTHOR [+2]

Abstract

Barrel plasma etching techniques for polysilicon pattern definition are inadequate for VLSI technologies. The line-width resolution required by new technique for etching polysilicon provides both line-width control and edge-profile control. Barrel plasma etching of polysilicon is isotropic -- the etch rates in the lateral and vertical directions are comparable. The etch rate is a function of dopant concentration, wafer temperature, and the degree of crystallinity of the polycrystalline silicon. In addition, the etch rate tends to be nonuniform across the surface of an individual wafer, and changes with the amount of exposed area being etched (loading).

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Polysilicon Dry Etching Using Reactive Ion Etching and Plasma Etching

Barrel plasma etching techniques for polysilicon pattern definition are inadequate for VLSI technologies. The line-width resolution required by new technique for etching polysilicon provides both line-width control and edge-profile control. Barrel plasma etching of polysilicon is isotropic -- the etch rates in the lateral and vertical directions are comparable. The etch rate is a function of dopant concentration, wafer temperature, and the degree of crystallinity of the polycrystalline silicon. In addition, the etch rate tends to be nonuniform across the surface of an individual wafer, and changes with the amount of exposed area being etched (loading). The major advantage of barrel plasma etching is the high selectivity achievable between polysilicon and silicon dioxide -- etch-rate ratios for polysilicon to silicon dioxide of 20:1 are common. Reactive ion etching (RIE) of polysilicon uses the same etch gas as plasma etching (CF4); however, the etch rate is independent of the doping concentration, the wafer temperature, and the crystallinity of the material. The effect of loading on the polysilicon etch rate is less with reactive ion etching. The major disadvantage of RIE of polysilicon using CF4 is the lack of selectivity between the etching of polysilicon and the underlying silicon dioxide; indeed, the etch rate of silicon dioxide exceeds that of polysilicon. The new technique incorporates the best of both etch systems, the uniformity of RIE with the selectivity of plasma etching. The product wafers are received with polysilicon over silicon dioxide. Two monitor wafers are included with the product wafers for the thermal oxidation and polysilicon deposition steps.

The polysilicon pattern is defined on the product wafers by a standard photoresist coat/align/expose/develop pro...