Unique technology for measuring effective carrier number by dynamic resistivity measurement.

Conventionally, reflected microwave photoconductivity decay method (μ-PCD), which measures minority carrier lifetime on a substrate surface, has been employed as a quality evaluation method of Si crystal substrate. The method has been used for shipping inspection of Si crystal substrates for solar cells by Si crystal manufacturers and acceptance inspection of crystal substrates by solar cell manufacturers.

However, there was a problem that correlation could not be obtained between average value or maximum value (or minimum value) of this measured value and energy conversion efficiency of solar cell. In order to know the solar cell characteristics of Si crystal substrate, there is only way to manufacture a solar cell and measure its energy conversion efficiency.
However, since much cost and time are spent to manufacture solar cells, currently, it is decided whether or not to ship or purchase Si crystal substrates only by average value, maximum value (or minimum value) or resistivity of their lifetime value. As a result, quality dispersion and defect rate have been increasing in the solar cell manufacturing industry.