Correlation of The Mechanical Properties of Silicon Oxynitride Films to Processing Parameters, Film Stoichiometry, and H
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I. INTRODUCTION PECVD silicon oxynitride films have not only been shown to have excellent electrical properties [1-51 for usage as insulating dielectrics but with their tunable bandgap [61, they also have demonstrated excellent optical properties in the blue and ultraviolet regions of the spectrum making it useful for an encapsulation layer of ultraviolet erasable programmable read only memories (UVEPROMS) [2,7]. Equally important characteristics of the films are the mechanical properties. These properties include the stress and modulus which are directly linked to stress induced failure in aluminum lines[8-1 1]. Another mechanical property, hardness, is an important characteristic of passivation layers because it can be related to how well the material deter moisture permeation and contamination from the outside environment in addition to how well it can resist abrasion and scratching. Film processing is largely responsible for these mechanical properties. By varying the process parameters such as power, pressure, and gas flow rates of N2 0, N2 , NH 3 and Sill4 , a range of silicon oxynitride films of different stoichiometry and microstructure and, hence, optical and mechanical properties can be made.[12] In this paper, we first relate the film stoichiometry and hydride bond concentrations (N-H nitrogen hydride, Si-H silicon hydride) of the hydrated oxynitride films, to the processing parameters such as the gas flow rates and the plasma power. We then relate the stoichiometry and hydride bond concentrations of the films to the mechanical properties such as hardness (H), modulus (E), and stress. As references, results from an atmospheric pressure chemically vapor deposited (APCVD) silicon dioxide film, a PECVD silicon dioxide and a PECVD silicon nitride
film are also reported. Results define a useful base of film properties for the range of films analyzed.
479 Mat. Res. Soc. Symp. Proc. Vol. 3bi1 1995 Materials Research Society
II. EXPERIMENT The oxynitride films used for this experiment were prepared using the AMAT 5000 PECVD system. A synopsis of the experimental parameters is given in Table 1. These films were prepared to have a relatively large range of mechanical properties. All films were deposited on 200 mm, p-type Si(100) wafers and were approximately one micron thick.
Table 1. Processing Parameters of Silicon Oxynitride Time "Groun(sec) A 100
Pressure (toff 4.7
RF Power (watts) •ccm) 690
Susceptor Temp L09 400
Susceptor Spacing (nil) 500
SiH4 195
N2 (seem) 4000
N20 NH3 (sccm°)(scea) 90 80
B
154
4.2
540
400
500
116
666
80
86
C D E
100 100 100
4.7 4.7 4.7
690 620 645
400 400 400
500 500 500
150 150 150
4000 4000 4000
84 75 75
100 100 100
A UMIS microhardness indentor was used to analyze the mechanical properties of several films for hardness and modulus at the center and edge locations of each wafer. From force versus displacement behavior and knowledge of the tip profile, hardness and modulus are calculated. Samples prepared in a class 1 clean room environment using the PECV
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