Lifetime is a property of a bulk semiconductor material, telling the amout of time, on average, an excess carrier exists in a semiconductor material before recombining to achieve equilibrium. The same parameter is also called “minority carrier lifetime,” “carrier lifetime,” and “recombination lifetime.” Lifetime of a semiconductor with a perfect crystal lattice and no comtamination will be long, and any imperfections in the semiconductor material or contamination will reduce the lifetime. Thus, monitoring lifetime is an excellent method to detect contamination.
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The most common way of measuring lifetime is via a technique called microwave PCD (µ-PCD). Many Semilab products include µ-PCD measurement technology. The WT-2000 offers maps of lifetime measurements for semiconductor wafers, via a benchtop system. The WT-3000 offers similar capability via a dual FOUP system for 300mm wafers. Semilab’s WT-2000MCT measures lifetime as a function of temperature for narrow band semiconductors.
Technical Note #200 explains the theory of µ-PCD measurements of lifetime.
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