Microdefects In Oxide-Films Deposited On Featured Surfaces Of Vlsi Substrates By Thermal Cvd Of Teos And O2

Silicon dioxide films formed by tetraethylorthosilicate, Si(OC2H5)4 (TEOS), oxidation have been used for passivation of transistors and integrated circuits. Microdefects tend to occur during film formation on featured surfaces of very large scale integration (VLSI) devices, and this degrades the integrity of the passivation films. To understand the mechanisms of microdefect formation better, we measured the density of microdefects in SiO2 films formed by TEOS oxidation on featured VLSI substrates. The deposited film thickness was 450 nm and, after deposition, the films were annealed and wet etched. The microdefect density was measured as a function of the film thickness after etching, showing the higher density for thinner film. The formation of microdefects occurred because of the film stress resulting from the large shrinkage that occurred during annealing. This shrinkage is partly due to densification, but we believe another major factor is that shrinkage occurs because of the decomposition of silanol radicals and unreacted intermediate molecules deposited during film formation. By correlating the tendencies of microdefects to form in terms of the solid angle made between the deposition species and the film surface, we also observed that defects tended to occur mostly in small holes and narrow grooves. This is a result of stress-induced etching in these structures because of the sharp curvature of the films.