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

Chlorine distribution in the system has been studied for two types of Cl‐doped oxides, both formed at 900°C: ( i ) thermal oxide grown with a trichloroethane (TCA) additive at 1.0, 2.5, and 4.0 equivalent percent and ( ii ) low pressure chemical vapor deposition (LPCVD) oxide, produced by the reaction of and at low pressure. Using SIMS profiles, it was found that Cl introduced by TCA oxidation piles up at the interface, reaching a peak of 4–10E18 atom/cm 3 . This Cl level proved adequate for metal oxide semiconductor (MOS) device passivation of alkali contamination. Conversely, LPCVD oxide deposited over 1000Å generates a uniformly high Cl level across the deposited oxide (7–10E19 atom/cm 3 ), but very low concentration at the silicon interface (< 1E18 atom/cm 3 ). Only after a high temperature anneal (1000°C for 1h) does this level become similar to the TCA value. However, such a treatment conflicts with the present trend toward reduced temperature processing. Since MOS stability is mainly dependent on interface properties, this behavior suggests that TCA oxidation is more effective than LPCVD for alkali contamination control in MOS integrated circuits fabrication.