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Minority Carrier Lifetime Measurements for Contactless Oxidation Process Characterization and Furnace Profiling
摘要： Contactless minority carrier lifetime (lifetime) measurements by means of microwave detected photoconductivity are employed for oxidation process characterization and furnace profiling. Characterization is performed on oxidized float zone substrates with high resistivity and outstanding bulk quality, suggesting that the measured effective lifetime is strongly dominated by interface recombination and therefore reflects the oxide quality. The applied approach requires neither test structures nor time consuming measurements and is therefore of particular interest if high throughput is required. The method is used to investigate the impact of oxidation furnace leakage as well as to analyze the oxidation homogeneity across a horizontal oxidation furnace. For comparison, capacitance-voltage measurements are conducted to characterize the oxide properties. It is found that any type of furnace leakage, which induces fixed oxide charges as well as interface states, has a heavy impact on the measured effective lifetime, especially on the shape of generation rate dependent lifetime curves. Furthermore, a distinct lifetime decrease towards the tube door of the oxidation furnace could be observed. The latter is even detectable in an ideal oxidation process, generating high quality oxides. Besides plain equipment characterization, the presented approach is suitable to optimize the oxidation process itself regarding different parameters like temperature, gas flow, pressure, or process time.
关键词： oxide characterization,float zone,lifetime,high-resistivity,furnace profiling
更新于2025-09-19 17:15:36
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AIP Conference Proceedings [AIP Publishing 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Fes, Morocco (25–27 March 2019)] 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Investigation of LeTID where we can control it – Application of FZ silicon for defect studies
摘要： In this work we present results of a series of experiments to investigate the origin of the defects causing light and elevated temperature induced degradation (LeTID). It has been demonstrated that LeTID effects can be observed even in high purity monocrystalline silicon. The experiments are therefore performed on float-zone silicon and feature a variety of process schemes to test important hypotheses on LeTID and reproduce them under more defined conditions. Different surface passivation schemes based on aluminium oxide layers are combined with a designated hydrogenation treatment and subjected to different thermal processes on both p- and n-type wafers. The results on p-type wafers confirm several previous observations concerning, e.g., the influence of silicon nitride layers and the firing peak temperature. However, we do not observe a crucial influence of the specific firing temperature profile in the experiment. The investigated n-type wafers do not feature a typical LeTID behaviour but appear to be affected by the LeTID defect nonetheless. Firstly, we observe an improvement of the effective lifetime under LeTID testing conditions that is driven by an improvement of the bulk lifetime. Secondly, identical pattern are observed in lifetime images of n-type wafers directly after firing and of p-type wafers in the degraded state. These findings strongly indicate that LeTID defects can be present in the initial state of n-type wafers after firing.
关键词： surface passivation,float-zone silicon,defect studies,hydrogenation treatment,LeTID
更新于2025-09-19 17:13:59