Improvement of Pin Photodiodes on the Soi Layer by Rapid Thermal Annealing

Abstract

AbstractElectrical properties of PIN photodiodes fabricated on the bonded silicon on insulator (SOI) wafers annealed at 900°C for 5 seconds were evaluated in order to investigate the effect of rapid thermal annealing (RTA) on SOI wafers. Traps in the SOI layers with different thicknesses (10,30,100 μm) were investigated using the deep level transient spectroscopy (DLTS) method. In the SOI layer with a thickness of 100 μm, a trap with deep energy level (about Ec-Et=0.55 eV) was observed and the concentration of the trap decreased from 5.0 × 1011 cm−3 to 1.5 × 1011 cm−3 by RTA. For PIN photodiodes on the 100 μm-thick SOI layer, the dark current decreased from 2 × 10−9 A to 6 × 10−10 A, and sensitivity uniformity for a 35 μmφ light spot and spectral responses were both improved by RTA. Lifetimes were obtained from open-circuit voltage (Voc) decay curves for 940 nm and 655 nm light, and they increased from 37 μs to 57 μs and from 47 μs to 62 μs, respectively, by RTA. For thinner SOI layers (thickness=10, 30 μm), PIN photodiodes have good uniformity and low dark current, and their characteristics were not changed by RTA.