Properties of SiO2 on Si after Exposure to 3:1 H 2 + N 2 and NH 3

Thermal oxides ≃100 nm thick were exposed to 3:1 for 30 min at 950°C; similar films were treated in pure ammonia for 30 min at 950°C. The oxides were examined by high frequency and quasi‐static capacitance‐voltage measurements. A silicon internal reflection element (IRE) was processed in a similar manner in order to assess the effects of the thermal processing on the infrared spectrum of the thin film. The IRE was used for attenuated total reflection infrared spectroscopy, a technique that provides greater sensitivity to molecular groups such as Si‐OH, , Si‐H, , and (1, 2). Secondary ion mass spectrometry revealed the quantitative distributions of N, O, and H throughout a sample film. Ammonia exposure resulted in replacement of oxygen by nitrogen in the amorphous tetrahedral network. Films annealed in (the expected dissociation products of ) were found to exhibit significantly different properties from films nitrided in , because did not attain thermodynamic equilibrium before coming in contact with the films. The anneal apparently increased the degree of oxygen bridging in . Based on the IR data, a new model is proposed to explain the annealing of interface traps via . Hydrogen is suspected to act as a catalyst, promoting bond rearrangement in the amorphous network. Nonbridging oxygen atoms are thought to bond to dangling silicon orbitals at the oxide/Si interface, thereby reducing the density of defects responsible for .