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Measuring the Doping Distribution on Semiconductor Wafers

IP.com Disclosure Number: IPCOM000087384D
Original Publication Date: 1977-Jan-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Pfeiffer, E: AUTHOR [+3]

Abstract

It is known that the semiconductor doping concentration can be determined from the gradient dC(V)/dV of the CV curve, and the absolute value of the voltage-dependent MOS capacity C(V) [1]. Furthermore, it has already been suggested to obtain the doping concentration from the harmonic analysis of a measuring signal of frequency f, as the amplitude of the fundamental wave is proportional to the absolute value of the capacity, and as the amplitude of the first harmonic with frequency 2f is proportional to the gradient of the CV curve [2].

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Measuring the Doping Distribution on Semiconductor Wafers

It is known that the semiconductor doping concentration can be determined from the gradient dC(V)/dV of the CV curve, and the absolute value of the voltage-dependent MOS capacity C(V) [1]. Furthermore, it has already been suggested to obtain the doping concentration from the harmonic analysis of a measuring signal of frequency f, as the amplitude of the fundamental wave is proportional to the absolute value of the capacity, and as the amplitude of the first harmonic with frequency 2f is proportional to the gradient of the CV curve [2].

The disadvantage of the above-indicated harmonic analysis method is that the relatively high amplitude of the AC measurement signal is, on the one hand, already harmonic-containing (approximately 1%), and that, on the other hand, it generates harmonics in the successive amplifiers and filters. Besides, the result of the measurement is affected by oxide charges.

It is suggested that the doping distribution on a semiconductor wafer be measured by a bridge circuit 1, as shown in the figure. For that purpose, MOS or Schottky structures are generated on the semiconductor wafer to be examined. When an AC voltage is applied to these non-linear components, harmonics are produced. By utilizing the first harmonic, relative doping differences of a silicon wafer are determined with high precision in this measuring process, as described in detail below. I. Reference 1. A reference MOS capacitor 2 on the wafer is connected in the bridge. 2. A balance of the bridge is effected with balance capacitor C and indicator 3 for fundamental wave f. Due to the...