Effect of Deep-Level Defects on Surface Recombination Velocity at the Interface Between Silicon and Dielectric Films

The surface recombination velocity (SRV) characteristic of deep-level defects at Si interfaces with dielectric thin films was obtained from conductance measurements on metal-insulator-semiconductor capacitor (MISCAP) devices. The dielectrics in contact with Si were thermal SiO(2) (Tox), chemical SiO(2), and atomic layer deposition (ALD) Al(2)O(3), which were annealed and exposed to a low flux of X-rays. A modified conductance technique was developed in which a large ac signal was superimposed on a dc bias and the surface potential was swept across the band gap of a MISCAP from near accumulation to deep depletion. The frequency-dependent energy loss due to all defects across the band gap and their correlations were measured using the effective equivalent conductance. A model containing one resistor and one capacitor was sufficient to describe the frequency-dependent energy losses due to defects with similar activities. The total SRV was 112 +/- 19 cm/s for Si/Tox, 1045 +/- 150 cm/s for Si/chemical SiO(2)/Al(2)O(3), and 578 +/- 96 cm/s for Si/Al(2)O(3) interfaces. After forming gas annealing at 400 degrees C, the SRV decreased to similar to 1 cm/s for both Si/Tox and Si/chemical SiO(2)/Al(2)O(3) and 47 +/- 6 cm/s for Si/Al(2)O(3). Vacuum annealing improved the Si/chemical SiO(2)/Al(2)O(3) interface but had an adverse effect on Si/Al(2)O(3). Soft X-ray exposure increased the SRV of both Si/chemical SiO(2)/Al(2)O(3) and Si/Al(2)O(3).