Browse Prior Art Database

Non Contact Local Measurement of Semiconductor Resistivity

IP.com Disclosure Number: IPCOM000095169D
Original Publication Date: 1965-Sep-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Bryant, CA: AUTHOR [+2]

Abstract

The local resistivity of semiconductor crystal 10 is obtained by measuring the radio frequency spreading resistance of small probe 13 placed on flat surface 12 of crystal 10.

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Non Contact Local Measurement of Semiconductor Resistivity

The local resistivity of semiconductor crystal 10 is obtained by measuring the radio frequency spreading resistance of small probe 13 placed on flat surface 12 of crystal 10.

Flat face 12 on crystal 10 is placed on flat surface 14 of outer electrode 15. RF current flowing from center electrode 16 spreads out in crystal 10. Resistivity of crystal 10 determines the real part of the impedance Z=R +jX between the electrodes 15 and 16. This impedance is measured by RF bridge 18. Such is separated from the electrodes by coaxial transmission line 20.

The electrical length of line 20 is made exactly equal to an integral number of half wavelengths at the measuring frequency of 450 Mc produced by generator
22. This can be modulated at an audio frequency, so that bridge 18 measures directly the value of the impedance at the interface between crystal 10 and electrode 15. The bridge 18 provides the magnitude absolute Z absolute and the phase angle tan/-1/ (X/R) of the electrode impedance.

The bridge detector is a superheterodyne system. This uses crystal mixer 24, oscillator 26, amplifier 28 and detector 30. If local oscillator 26 is modulated by modulator 32, headphones 34 can be used as a null indicator.

The electrodes 16 and 15 are formed by the end face of the inner coaxial 20 conductor and the top surface 14 of a flange connected to the outer conductor of coaxial 20. The end of the inner conductor is held concent...