Patent US3890564A successfully refreshed from Google Patents.
US3890564A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus for inducing eddy current in a semiconductor wafer for measuring the electric conductivity or resistivity thereof
Assignee: Ohkura Electric Co Ltd
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Filing: 1972-11-03
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Granted: 1975-06-17
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Expires: 1992-11-03
Abstract
Abstract An apparatus for measuring electric conductivity or resistivity of a semiconductor wafer with no electric contact to the wafer, which comprises an exciting circuit including a first exciting coil for measuring, and a second exciting coil for compensation, which are connected in series to each other, and an oscillator for supplying an alternating current to the first and second exciting coils. A detecting circuit has a first detecting coil which is positioned spaced apart from the first exciting coil to form a gap therebetween, the wafer being inserted in the gap for measurement, and a second detecting coil for compensation which is connected in series to the first detecting coil and is magnetically connected to the second exciting coil, thereby a differential output being obtained between each end of the first, and second detecting coils. A bandpass filter eliminates higher harmonics and noise component and is contained in the output of the detecting circuit, and a phase shifter shifts the phase of the output of the bandpass filter to the phase of the voltage induced in the second detecting coil. A synchronous rectifier means rectifies synchronously the output of the phase shifter with reference to the output of the detecting circuit, and an operation circuit means is provided to obtain an output proportional to the electric conductivity or resistivity of the wafer from the output of the synchronous rectifier means and data concerning the thickness of the wafer. An indicator means indicating the output of the operation circuit means.
Inventors
- 👤 Takashi Watanabe
- 👤 Koichi Watamura
- 👤 Kazuya Kawatani
- 👤 Hideo Aoki
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 14:17
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/02; G01N27/023; G01R; G01R27/00; G01R27/02
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
305 words
An apparatus for measuring electric conductivity or resistivity of a semiconductor wafer with no electric contact to said wafer, comprising an exciting circuit including a first extending coil for measuring, and a second exciting coil for compensating which are connected in series to each other, an oscillator for supplying an alternating current to said first and second exciting coils, a detecting circuit having a first detecting coil which is positioned spaced apart from said first exciting coil to form a gap therebetween, said wafer being inserted in said gap for measurement, and a second detecting coil for compensating which is connected in series opposition to said first detecting coil and is magnetically connected to said second exciting coil, thereby a differential output being obtained between each end of said first and second detecting coils, a pair of U-shaped magnetic cores on which said first coils, respectively, are wound in such arrangement that the ends of each said magnetic core have the same polarity but the opposite polarity with respect to the ends of the other, a bandpass filter means for eliminating higher harmonics and noise component being provided in an output portion of said detecting circuit, a phase shifter means operatively connected to said bandpass filter means for shifting the phase of the output of said bandpass filter means by 90* with respect to the phase of the voltage induced in said second detecting coil, a synchronous rectifier means for rectifying synchronously the output of said phase shifter with reference to the output across said second detecting coil, an operation circuit means for obtaining an output proportional to the electric conductivity or resistivity of said wafer from the output of said synchronous rectifier means and data concerning the thickness of said wafer, and an indicator means for indicating the output of said operation circuit means.
Claim 2
Independent Claim
305 words
An apparatus for measuring electric conductivity or resistivity of a semiconductor wafer with no electric contact to said wafer, comprising an exciting circuit including a first extending coil for measuring, and a second exciting coil for compensating which are connected in series to each other, an oscillator for supplying an alternating current to said first and second exciting coils, a detecting circuit having a first detecting coil which is positioned spaced apart from said first exciting coil to form a gap therebetween, said wafer being inserted in said gap for measurement, and a second detecting coil for compensating which is connected in series opposition to said first detecting coil and is magnetically connected to said second exciting coil, thereby a differential output being obtained between each end of said first and second detecting coils, a pair of U-shaped magnetic cores on which said first coils, respectively, are wound in such arrangement that the ends of each said magnetic core have the same polarity but the opposite polarity with respect to the ends of the other, a bandpass filter means for eliminating higher harmonics and noise component being provided in an output portion of said detecting circuit, a phase shifter means operatively connected to said bandpass filter means for shifting the phase of the output of said bandpass filter means by 90* with respect to the phase of the voltage induced in said second detecting coil, a synchronous rectifier means for rectifying synchronously the output of said phase shifter with reference to the output across said second detecting coil, an operation circuit means for obtaining an output proportional to the electric conductivity or resistivity of said wafer from the output of said synchronous rectifier means and data concerning the thickness of said wafer, and an indicator means for indicating the output of said operation circuit means.
Claim 3
Dependent Claim
52 words
The apparatus as set forth in claim 1, wherein an electrostatic shielding plate is interposed between said first exciting coil and said wafer, said electrostatic shielding plate being shaped to prevent the formation of a closed circuit for the eddy current induced by the magnetic flux produced by said first exciting coil.
Claim 4
Dependent Claim
26 words
The apparatus according to claim 2 wherein said electrostatic shielding plate comprises an insulative substrate and a thin metal film in the form of a comb.
Claim 5
Dependent Claim
39 words
The apparatus, as set forth in claim 2, wherein said electrostatic shielding plate comprises an insulative substrate and a pair of thin metal films in the form of comb, said combs being opposite each other with their teeth interleaved.
Claim 6
Dependent Claim
61 words
The apparatus, as set forth in claim 1, further comprising a first condensor connected in series to said first exciting coil to form a first series resonance circuit, a second condensor connected in series to said second exciting coil to form a second series resonance circuit, and said first and second series resonance circuits are connected in series to each other.
Claim 7
Dependent Claim
67 words
The apparatus, as set forth in claim 1, further comprising a first resistor connected in parallel to said first detector coil to form a first parallel circuit, a second resistor connected in parallel to said second detector coil to form a second parallel circuit, and said first and second parallel circuits are connected such that a differential output between said first and second parallel circuits is obtained.
Claim 8
Dependent Claim
90 words
The apparatus, as set forth in claim 1, further comprising a first cylindrical casing made of a magnetic material and a second cylindrical casing made of magnetic material, each of said casings being closed at one end thereof and arranged in such a manner that the open ends thereof face each other and are spaced from each other forming said gap into which said wafer is inserted, said first magnetic core is contained in said first cylindrical casing and said second magnetic core is contained in said second cylindrical casing.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-06-16 | 1978-12-16 | 1979-06-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-06-16 | 1982-12-16 | 1983-06-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-06-16 | 1986-12-16 | 1987-06-17 | $7700.00 | Window Closed / Lapsed |