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Determination of the Quality of Silicon Surfaces

IP.com Disclosure Number: IPCOM000074010D
Original Publication Date: 1971-Mar-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Evrenidis, P: AUTHOR [+3]

Abstract

This method allows determination of the quality of silicon surfaces used in MOS and bipolar devices by examination of the low frequency characteristic of an MOS capacitor operated in the inversion region.

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Determination of the Quality of Silicon Surfaces

This method allows determination of the quality of silicon surfaces used in MOS and bipolar devices by examination of the low frequency characteristic of an MOS capacitor operated in the inversion region.

Circuit A consists of an AC generator 1 in series with a biasing voltage 2, MOS capacitor 3 and load resistor R. After biasing capacitor 3 in the region of strong inversion, the voltage V, representative of capacitance C across capacitor 3, measured across resistor R is indication of the defect density of the silicon surface of capacitor 3. Low values indicate low-defect density and a high quality surface and high values indicate high-defect density and a poor quality surface. Circuit B is similar to A but utilizes an I-V technique. Voltage generator 4 generates a ramp voltage to cause capacitor 5 to go from accumulation to inversion. Current I, measured by ammeter A, is noted at one particular voltage in the region of expected inversion. Calibration is achieved by choosing a ramp rate which will not cause inversion in the best quality devices to be tested. Shown at C is a plot of C, for circuit A, or I for circuit B, versus applied voltage V(g). Devices are graded according to the value of C, or I, at a particular value of V(g).

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