Measurement of Toughness for Sin Films on Silicon Using Channel Cracking Technique

Abstract

Silicon nitride thin films used for transistor spacer are usually under large tensile residual stresses. When a film is thick enough, it can crack by channel cracking mechanism. The toughness of these films, used in models for failure criteria, can be obtained by determining the critical thickness for channel cracking of blanket films with known residual stresses. However, depositing films of a range of different thickness to determine the critical thickness is tedious, and this process also introduces risks of producing particles in the deposition chamber when the film exceeds the critical thickness. An alternative technique is to deposit films of thickness below critical thickness and then to apply additional tensile stresses to the film by bending the substrate. A critical film stress can be determined for channel cracking from which the film toughness is obtained. This paper describes the experiments performed for a new SiN film and presents the results.

Creep of Al Underlayer Determined by Channel Cracking of Topical Si3N4Film

“…Finally the fracture toughness of a brittle film on an elastic substrate can be calculated from the following [12,13]:…”

“…This gives a viscosity of 9 6 × 10 16 Pa.s as shown in Table 1. The values of , , and E for the films and the substrates are taken from Liang et al [11,15,16] and Ma et al [12,13]. The calculated value is based on the …”

“…Ma et al [12,13] have reported two values for the fracture toughness of Si 3 N 4 based on the nature of substrates. A fracture toughness of 4.9 J/m 2 was reported [13] for Si 3 N 4 deposited on Si.…”

“…Channel cracking [9][10][11][12][13][14][15] has been developed to study and compute [10,16] the steady state energy release rate of channeling cracks in thin films. The application of this method is important in the prediction of the fracture behavior of multilayered structures that are under residual stress developed during the fabrication process.…”

“…The creep properties of the underlayer and the fracture toughness of the topical inelastic layer are interrelated such that if one is known the other one can be calculated. Ma et al [12,13] studied channel cracking in brittle Si 3 N 4 films deposited on Al [12] and on Si [13] substrates. They reported two different values for the fracture toughness of Si 3 N 4 , as will be discussed later.…”