A semiquantitative analysis is performed and correlation between the major parameters and structural perfection of silicon pin-photodetectors is found using currently available methods. Both virgin single-crystal silicon wafers, high-resistance silicon structures (HRS), structures upon intermediate treatments, and finished pin-devices are investigated. In most cases oxygen and hydrogen are found to be the major impurities in virgin silicon, and doping inhomogeneities affect the photodetector parameters but slightly. Oxygen in an electrically active state generates additional energy levels, leading to changes in the concentration of major charge-carriers and in the parameters of structural defects. This also indirectly affects the parameters of finished devices.Silicon pin-structures are used as effective photodetectors due to the high injection coefficients, which allows photodetectors with high photocurrent-amplification factor and quantum efficiency to be produced.One of the most important problems in production of silicon pin-photodetectors is studying the effect of impurity composition and imperfection on major parameters of the devices. The structural and impurity defects and their distribution over the semiconductor wafers may play a crucial role in the yield ratio of known-good devices. In spite of a great deal of works on this problem (see, for example, [1-3]), it is rather difficult to systematize the main data available.This work is aimed at finding correlation between the major parameters of silicon pin-photodetectors and structural and impurity composition of virgin silicon, intermediate structures, and finished devices. The dependence of structuraldefect parameters on the impurity type and concentration is also studied.
SUBJECTS AND INVESTIGATION TECHNIQUESThe virgin single-crystal high-resistance silicon wafers with ρ = 1000-2000 Ω⋅сm, HRS structures (i-n + -structures n + with ρ = 0.05 Ω⋅сm), intermediate structures upon main treatments, and finished pin-devices fabricated using a conventional vertical-topology technique (shallow р-і transition is located atop at a depth of 0.5 µm) were examined. An electron image of the pin-photodetector surface in a conduction mode is shown in Fig. 1.The wafer surfaces subjected to pretreatment in the Caro and ammonical-peroxide solutions [4,5] were further treated by selective Sirtle (111 surface) and Secco (100 surface) etchants to reveal structural defects, the etching rate being about 2-3 µm/min. The pretreatment improved the revealing properties of the selective etchants used.The following techniques and equipment were used for examination of the silicon surface upon chemical treatment: -scanning electron microscopy (SEM), a Cam Scan-4D scanning electron microscope-analyzer with a Link-860 energy-dispersion analyzer system (the mass sensitivity of the device being 0.01% and the beam diameter varied between 5⋅10 -9 and 1⋅10 -6 m, according to a "Zaf" program code used), -Auger electron spectroscopy (AES), a Riber LAS-3000 spectrometer (spatial resolution 3 µm...