US Patent:
20030017700, Jan 23, 2003
Inventors:
Gary Was - Ann Arbor MI, US
David Srolovitz - Highland Park NJ, US
Zhenqiang Ma - Ann Arbor MI, US
Liang Dong - Santa Clara CA, US
International Classification:
H01L021/20
H01L021/44
Abstract:
This invention produces a film which is resistant to hillocking without compromising the electrical conductivity of the interconnects, the circuit architecture or any other function affecting the operation of the integrated circuit. The invention works on the principle that hillocking is caused by the squeezing or extrusion of certain grains (crystals) in the film due to a compressive residual stress state that arises from annealing (heating) treatments applied to the film following the deposition of the film. These grains are in a “weak” crystallographic orientation relative to the great majority of the grains. The coordinated orientation of this great majority of grains is known as the texture and aluminum films are deposited with a strong () texture, where () refers to specific crystallographic planes and < . Refers to the direction normal to the () plane. Any grains which are not aligned in the < direction, are weaker than those that are and are susceptible to being squeezed out of the plane of the film by the residual stresses imposed by the annealing step. Essentially, the strong grains push on each other and on the weak grains and only the weak grains are squeezed out. Our invention consists of depositing a film with a texture that is mechanically weak. In this way, the great majority of grains will be weak, and under a compressive residual stress, they will deform in a homogeneous manner. The few strong grains will not deform.