JIPELEC and LPM (INSA de Lyon/France) have developed LPCVD process of low-stress silicon nitride films (silicon-rich nitride) with average stress lower than 150 MPa in a TubeStar Jipelec furnace.

The TubeStar furnace is a conventional tubular horizontal hot-wall LPCVD reactor with 3 heat zones in wich batch of up to 50 wafers (100mm dia.) can be loaded on a quartz boat system. The wafers can be stacked vertically at the flat temperature zone (17 cm @ 800-1000°C ).
LPCVD SiN films were deposited from dichlorosilane (DCS) and ammonia (NH3) decomposition under different process conditions (temperature, pressure, gas ratio).

Fig. 1: Average stress in LPCVD SiN films vs. Process Gas Ratio.		Fig. 2: Refractive index of LPCVD SiN films vs. Process Gas Ratio.
Thickness uniformity of around 2.5% was obtained across 100 mm wafer. The total stress in the SiN layers was determined by wafer curvature measurements. SiN films with a reduction of stress to 46 MPa have been produced when excess DCS is used (see Fig.1). It appeared clearly that stress reduction could be achieved for Si-rich SiN films (see Fig.2).
JIPELEC Contact: Bachir Semmache JIPELEC 11 Chemin du vieux chêne F-38240 MEYLAN Phone: 33 4 76 04 06 06 Fax: 33 4 76 04 81 40 E-mail: semmache@jipelec.com		LPM (INSA de Lyon) Contact: Mustapha Lemiti LPM, Bât 502 (2ème étage) 20 Avue A. Einstein 69621 Villeurbanne cedex Phone: 33 (0)4 72 43 87 31 Fax: +33 (0)4 72 43 83 29 E-mail: lemiti@insa-lyon.fr