Surface voltage decay, measurement

Surface voltage decay was measured with a Trek Model 341 high voltage electrostatic voltmeter (ESVM). The ESVM drives the potential of a probe body to the same potential as the film surface voltage. This device measures the voltage independent of distance within 5 mm of the film surface without causing current flow, which would modify the data. After poling, the corona needle was removed and the probe of the ESVM was placed 3 mm from the film surface. 

There are numerous techniques to measure the recombination lifetime. Some of the better known are photoconductive decay (13). diode reverse recovery (14). diode open circuit voltage decay (15). surface photovoltage (JL ) and forward-biased pn junction I-V characteristic (17. I will describe one particular photoconductive decay method, because it is a relatively new, non-contact method that requires no junctions. This makes it very suitable for a large number of measurements as for a process sequence characterization tool. 

A number of characterization methods for wafers are used today. One group of experiments aims at the purely electronic parameters like DLTS and Photoluminiscence. While DLTS and related measurements give information on the trap energies, methods like surface photovoltage (SPV) or open circuit voltage decay (OCVD) give information on effective diffusion length. 

What is impUed by unequal generation and recombination lifetimes The lifetime measurement techniques and the resulting lifetimes measured with them must be clearly understood to avoid confusion. For example, the recombination lifetime is measured by such methods as photoconductive decay, open-circuit voltage decay, diode reverse-recovery, surface photo voltage, electron-beam induced current and others. 

Fig. 2. Measuring static charge, (a) Field voltage measurement (b) Faraday cage (c) surface resistivity measurement and (d) static decay test.

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