Two-frequency method for measuring impurity profiles.
A new method of plotting the impurity profile is described. It makes efficient use of the advantage of an operational amplifier and the nonlinearity of the junction capacitance in a semiconductor. When two small ac signals are applied to the inverting input terminal of the operational amplifier, intermodulation arises due to the nonlinearity of the junction capacitance inserted in the feedback loop, at the time the reverse bias voltage to the junction can be supplied from the noninverting input terminal; then the signals concerning both the depletion layer width x and the impurity concentration N (x) arise at the output terminal of the operational amplifier. By detecting each of the amplified input signals and the difference-frequency ones corresponding to x and N (x), respectively, the relation of x-N (x) can be plotted easily, at the same time, in a short time, and at a low cost.
Sukegawa
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Research Institute of Electronics, Shizuoka University, Hamamatsu, JapanJunior College of Engineering, Shizuoka University, Hamamatsu, Japan.
Ogita
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