Capacitors, generation lifetime

In contrast to r measurements, in which the decay of excess carriers is monitored the generation lifetime is determined from the reverse-biased pn junction leakage current or from the pulsed MOS capacitor (22.) latter and the more popular of the two, an MOS-C is pulsed into deep depletion and the capacitance is monitored as a function of time. An appropriate analysis of the C-t response yields t. ... 

Applying these considerations to generation lifetime we would expect a drop in lifetime outside of the DZ (fig. 17). This in fact is observed. Fig.18 shows lifetime-measurements on a wafer, which after precipitation was slightly wedge shaped polished in order to vary the depth of the DZ. Subsequently MOS capacitors had been built and the lifetime measured. The increase in lifetime is due to the DZ. 

Figure 18. Generation lifetime of capacitors with varying distances to the precipitated area of the wafer.

Figure 21. MOS generation lifetime map. Each point represents a MOS capacitor. The average lifetime is 500 psec, the standard deviation is 70 psec.

The generation lifetime is measured with the pulsed MOS capacitor or the gate-controlled diode technique. It is important to understand that the lifetime measured by this technique can, and generally does, give very different values from the recombination lifetime measured by one of the techniques indicated above. 

Electrical Characterization of Semiconductor Materials and Devices 23 4.2.2 Generation Lifetime Pulsed MOS Capacitor... 

The pulsed MOS capacitor (MOS-C) method is the most common technique to measure the generation lifetime. To determine it is necessary for scr generation to be dominant For silicon devices this is generally true when the pulsed MOS-C measurement is done at room temperature. For Xg determination the MOS-C is pulsed from accumulation into deep depletion. As a result of thermal ehp generation the device relaxes to its inversion state. [21] To extract the generation lifetime the capacitance, C, is measured as a function of time, as shown in Fig. 10(a). From such a C-t plot one generates a Zerbst Plot. [89] A Zerbst plot is a plot of vs. (Cp/C-1). It is related to the device... 

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