Study On Photocarrier Radiometry Methods Of Semiconductor Metarial Properties

In microelectronic and photovoltaic industry, semiconductors are the base materials in which impurities or defects have a serious impact on the properties of semiconductor-based devices. To improve the integration density of microelectronic devices and the photoelectric conversion efficiency of photovoltaic devices, more requirements are required for semiconductor matarials, and the testing methods of the material properties must be nondestructive and contactless with higher sensitivity and faster speed to meet the needs of industrial production. In this thesis, optical testing methods of semiconductor metarial properties are investigated.Photocarrier radiometry(PCR) is a purely carrier-density-wave diagnostic technology for the transport property of semiconductors. In this thesis, the essential concepts of carrier generation, recombination and transportation in silicon wafers were presented for understanding the dynamical behavior better. The continuity equations with boundary conditions were derived and the solutions were given, particularly focusing on harmonically modulated excess carrier generation. From the theory of spontaneous emission of radiation by non-black bodies such as semiconductors, the PCR signal expressions were derived. A nonlinear PCR model was developed to interpret the nonlinear dependence of PCR signals on optical excitation intensity.The problems of the instrumental frequency response in PCR system were analyzed, and an approach to eliminate instrumental frequency response from PCR signals was proposed. The signal dependences on the carrier transport parameters, such as carrier lifetime, diffusion coefficient and surface recombination velocity, and the measurement sensitivities of these parameters were analyzed in theory. Both simulation and experimental results showed the approach was feasible, and could give more accurate fitted carrier transport parameters.In addition, the speed of a testing method is also important for testing online. Thus steady-state photocarrier radiometric imaging technique was developed to characterize the electronic transport properties of silicon wafers. Based on above nonlinear PCR theory, simulations were performed to investigate the effects of electronic transport parameters on the steady-state PCR intensity profiles. The electronic transport parameters of an n-type silicon wafer were simultaneously determined by fitting the measured steady-state PCR intensity profiles to the three-dimensional nonlinear PCR model. The determined transport parameters were in good agreement with the results obtained by the conventional modulated PCR technique with multiple pump beam sizes. The results indicated the proposed steady-state PCR imaging technique allows for fast determination of local electronic transport parameters from a single PCR image. In addition, the technique was also applied to characterize the ion-implanted and/or annealed silicon wafers.PCR was employed to investigate the light-induced degradation(LID) of boron-doped Czochralski-grown silicon without surface passivation. The results showed that the light-induced changes of surface state occupation had a great effect on LID under laser illumination, which were related to the density and depth profiles of the photoexcited carrier. In addition, we employed PCR technology to investigate ultra shallow junction(USJ) wafers irradiated by excimer laser with different laser parameters, such as laser fluence, shot number, and repetition rate. The results showed that the implantation-induced crystalline structural damage was reduced and the implanted ions were effectively activated without great dopant diffusion. PCR was proven to be a useful tool for laser annealing evaluation.