Diffusivity of Implanted Chlorine Atoms in Thermal Oxides on Silicon

Abstract

It is well known (1–4) that substantial amounts of chlorine can be incorporated in normalHCl grown thermal oxides on silicon to effectively passivate sodium ions. It has been of interest to find out if similar effects can be obtained for oxides chlorinated by implanting Cl ions at the surface of SiO2 films on Si. It appears (5, 6), however, that when these films are annealed at temperatures in excess of 700°C, no Na neutralization property is evident. In this paper, we show with the help of 4He ion Rutherford backscattering (RBS) experiments on chlorine implanted into a thermal oxide film on Si that the oxide loses about 10 (50) percent of the implanted Cl during annealing at 600°C (1100°C) in nitrogen for 30 min. We obtain the diffusion coefficient D of Cl in SiO2 at various temperatures with the help of a process simulation program (SUPREM II) and show that for D∼D0expfalse(−Enormala/normalkTfalse) , D0=10−12 cm2/normals and Enormala∼0.5 normaleV . Corrections for system resolution and energy straggling effects are made to obtain the actual Cl density profiles in the SiO2 film. It is seen that Cl at 50 keV has a range of 440Å in SiO2 with a standard deviation of 220Å for a gaussian form.

Chlorine Levels in SiO2 Formed Using TCA and LPCVD at Low Temperatures

“…This means that the diffusivity of C( through oxide during oxidation is so high that it is not a limiting factor on achieving its thermochemical equilibrium distribution. Recently published diffusion coefficients of C1 in SiO2 agree with this finding (24).…”

“…The majority of the C1 (98%) left the oxide, presumably by diffusion to the free interface and desorbing. Recently the loss of C1 by evaporation from SiO2 during annealing at 600~176 was also observed by other workers (17,24). Annealing the TCA oxide for lh at 1000~ caused only a slight decrease in the total and maximum C1 levels.…”