Method and apparatus for the contactless monitoring carrier life

Details Method and apparatus for the contactless monitoring carrier life Method and apparatus for the contactless monitoring carrier life

Filed on

1979-05-18

Date issued

1981-08-25

Examiner

Karlsen, Ernest F.

Patent Class

Electricity: measuring and testing

SubClass

Measuring, testing, or sensing electricity, per se

SubSubClass

With rotor

Other Related Categories

324158D, G01R 3126

Type

Patent

Status

active

Patent number

042862159

Description

ABSTRACT:
The lifetime of minority carriers in semiconductor materials is measured by a noncontacting steady-state method adapted for monitoring of the condition of wafers during device manufacture. The method comprises coupling the sample into an LC resonant circuit which is the frequency-determining portion of a marginal-oscillator adapted to maintain either a constant amplitude RF signal, or be driven by a constant current generator, and measuring either the current required to so maintain the signal, or the difference in RF voltage, either of which is related to the sample's conductivity. Illuminating the sample with light of appropriate frequency from an intermittent source modulates the conductivity, and the difference in the steady-state values of conductivity in the illuminated and the dark condition is proportional to the minority carrier lifetime. Exemplary apparatus has a lifetime resolution of about 0.1 .mu.sec, with a measurement time of 0.4 sec, and a sampled area of about 0.3 cm.sup.2.

REFERENCES:
patent: 3234461 (1966-02-01), Trent et al.
patent: 3737803 (1973-06-01), Kojima et al.
patent: 4000458 (1976-12-01), Miller et al.
Robinson, F. N. H.; "Nuclear Resonance . . ."; J. of Sci. Instruments, vol. 36, Dec. 1959, pp. 481-487.
"Measurement of Silicon Parameters"; Electronic Design; Nov. 25, 1959, p. 167.
Weingarten et al.; "Radio-Frequency Carrier . . ."; J. of the Electrochemical Soc., vol. 108, No. 2, Feb. 1961, pp. 167-171.

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