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Photochemical Deposition of Graded Silicon Nitride

IP.com Disclosure Number: IPCOM000040806D
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Jasinski, JM: AUTHOR [+2]

Abstract

Silicon nitride films can be photochemically deposited from mixtures of silane and ammonia, using excimer lasers (193 nm). However, essentially all of the laser light is absorbed by the ammonia which photodissociates and induces film growth. Consequently, films grown by this technique can be silicon deficient, or, at best, stoichiometric. In order to provide a system which can easily deposit stoichiometric films, or films of graded composition (with excess silicon), disilane is introduced into the system in place of silane.

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Photochemical Deposition of Graded Silicon Nitride

Silicon nitride films can be photochemically deposited from mixtures of silane and ammonia, using excimer lasers (193 nm). However, essentially all of the laser light is absorbed by the ammonia which photodissociates and induces film growth. Consequently, films grown by this technique can be silicon deficient, or, at best, stoichiometric. In order to provide a system which can easily deposit stoichiometric films, or films of graded composition (with excess silicon), disilane is introduced into the system in place of silane.

Unlike silane which absorbs only very weakly at the excimer laser wavelength (193 nm), disilane absorbs readily and photodissociates to form silicon-bearing gas phase radicals which contribute to film growth. Films grown using this chemistry are found to be silicon-rich as judged by their indices of refraction (n greater than 2.4). With the use of appropriate mixtures of ammonia with silane and/or disilane, photochemically deposited silicon nitride films of continuously variable stoichiometry can be produced. In this manner, structures such as stacked dielectrics may be readily fabricated in a single pass, and without process interruption.

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