Noncontact conductivity measuring instrument

• US 20060152229A1
• Filed: 11/05/2004
• Published: 07/13/2006
• Est. Priority Date: 11/10/2003
• Status: Active Grant

• Current Assignee: Tohoku Techno Arch Co., Ltd.
• Original Assignee: Tohoku Techno Arch Co., Ltd.
• Inventors: Ju, Yang
• Granted Patent: US 7,309,995 B2
• Time in Patent Office: Days
• US Class Current: 324/637
• CPC Class Codes: G01R 27/04 in circuits having distributed constants , e.g. having very long conductors or involving high frequencies
• CPC Class Codes: G01R 31/2648 Characterising semiconductor materials testing of materials or semi-finished products G01R31/2831; testing during manufacture H01L22/00

Abstract

The present invention relates to measurement of conductivity, particularly to the noncontact measurement of the conductivity using a microwave. A microwave oscillated by an oscillator (110) using a Gunn diode is applied through an isolator (120), a circulator (130), and a horn antenna (140) to a silicon wafer (150). The isolator (120) is used for reducing the standing wave influencing the operation of the instrument. The reflected wave is received by the same horn antenna (140), detected by a detector (160) connected to the circulator (130), and outputted in the form of a voltage. The detector (160) produces an output voltage proportional to the square of the amplitude of an electric field. Since the amplitude of the reflected wave from a silicon wafer (150) is proportional to the absolute value of the reflectance, the output voltage is also proportional to the square of the absolute value of the reflectance. The reflectance is in a certain relationship with the conductivity, the conductivity of the silicon wafer (150) can be determined.

Claims

1. A noncontact conductivity measuring instrument using a microwave, the noncontact conductivity measuring instrument characterized by including:

an oscillator which performs oscillation of the microwave;

a circulator which is connected to the oscillator;

a horn antenna which is connected to the circulator, the horn antenna transmitting the microwave to a sample and receiving a reflected wave;

a detector which is connected to said circulator, the detector outputting a voltage proportional to a square of magnitude of the received microwave; and

computing means for inputting said voltage to compute conductivity.

2. A noncontact conductivity measuring instrument according to claim 1, characterized in that said circulator is in contact with the oscillator through an isolator.

3. A noncontact conductivity measuring instrument according to claim 1, characterized in that a frequency of the microwave oscillating in said oscillator is 94 GHz when a silicon wafer is measured.

4. A noncontact conductivity measuring instrument according claim 2, characterized in that a frequency of the microwave oscillating in said oscillator is 94 GHz when a silicon wafer is measured.