US4456879A
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Method and apparatus for determining the doping profile in epitaxial layers of semiconductors
Assignee: Intersil Corp
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Filing: 1981-09-02
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Granted: 1984-06-26
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Expires: 2001-09-02
Abstract
Abstract An apparatus and method for determining the doping profile of an epitaxial layer of a semiconductor as a function of conductivity (or resistivity) vs. distance (depth) includes modifying a d.c. generated current by a focused laser beam modulated at high frequencies in the order of 20 MHz, and directed in sequence on a point-by-point basis to the layer surface. Photocurrent variations from point-to-point effected by the laser beam striking the layer at each of the sequence of points are detected to provide a signal related to conductivity, (or, if desired, resistivity) of the layer material.
Inventors
- 👤 Hans P. Kleinknecht
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 20:23
CPC Classifications
G; G01; G01R; G01R31/00; G01R31/26; G01R31/265; G01R31/2656; Y; Y10; Y10S; Y10S148/00; Y10S148/093
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
93 words
Apparatus for determining the doping profile in an epitaxial layer of semiconductor material comprising: (a) means for applying direct current to an epitaxial layer of a semiconductor; (b) means for providing a laser beam modulated at a relatively high frequency; (c) means for focusing and directing said laser beam to one or more locations in sequence on an exposed surface of said layer to cause photocurrents to generate current flow variations in the layer; and (d) means for monitoring said current flow variations including means for detecting a signal representing said photocurrent variations.
Claim 2
Dependent Claim
93 words
Apparatus for determining the doping profile in an epitaxial layer of semiconductor material comprising: (a) means for applying direct current to an epitaxial layer of a semiconductor; (b) means for providing a laser beam modulated at a relatively high frequency; (c) means for focusing and directing said laser beam to one or more locations in sequence on an exposed surface of said layer to cause photocurrents to generate current flow variations in the layer; and (d) means for monitoring said current flow variations including means for detecting a signal representing said photocurrent variations.
Claim 3
Dependent Claim
20 words
The apparatus according to claim 1, wherein said laser beam is modulated at a frequency of at least 1 MHz.
Claim 4
Dependent Claim
12 words
The apparatus according to claim 1, wherein said semiconductor layer is beveled.
Claim 5
Dependent Claim
29 words
The apparatus according to claim 1, wherein said laser beam focusing means includes a beam expander and a microscopic objective lens for focusing said beam to a small diameter.
Claim 6
Dependent Claim
19 words
The apparatus according to claim 4, wherein said beam is focused with a diameter no greater than 1 μm.
Claim 7
Dependent Claim
22 words
The apparatus according to claim 1, wherein said detecting means includes a filter for detection of said signal representing the photocurrent variations.
Claim 8
Dependent Claim
25 words
The apparatus according to claim 1, wherein said detecting means includes a phase sensitive detection means for detection of said signal representing the photocurrent variations.
Claim 9
Dependent Claim
23 words
The apparatus according to claim 1, wherein said detecting means includes a heterodyning means for detection of said signal representing the photocurrent variations.
Claim 10
Dependent Claim
20 words
The apparatus according to claim 1, wherein said laser means comprises a He-Ne laser at a wavelength of 0.6328 μm.
Claim 11
Dependent Claim
35 words
The apparatus according to claim 1, wherein said d.c. applying means includes a pair of contacts spaced apart respectively on the upper surface of the epitaxial layer and the lower surface of the semiconductor substrate.
Claim 12
Dependent Claim
42 words
The apparatus according to claim 1, wherein said d.c. applying means includes a pair of contacts on the surface of said epitaxial layer for connection to direct current and positioned so that current flows parallel to the plane of the epitaxial layer.
Claim 13
Dependent Claim
63 words
The apparatus according to claim 1, wherein said layer of said semiconductor material is arranged so that said layer is beveled relative to a substrate of said layer and extends longitudinally outwardly from the substrate, a relatively small area contact being formed on the upper surface of the epitaxial layer, whereby said current flow variations in the beveled epitaxial layer are significantly enhanced.
Claim 14
Independent Claim
104 words
A method for determining the doping profile in an epitaxial layer of a semiconductor comprising the steps of: (a) applying direct current to an epitaxial layer of a semiconductor; (b) providing a laser beam modulated at a relatively high frequency; (c) focusing and directing said laser beam to one or more locations in sequence on an exposed surface of said layer to cause photocurrent to generate current flow variations in the layer; (d) monitoring said current flow variations to generate a doping profile of the layer along the path of one or more of said locations by detecting a signal representing said photocurrent variations.
Claim 15
Independent Claim
104 words
A method for determining the doping profile in an epitaxial layer of a semiconductor comprising the steps of: (a) applying direct current to an epitaxial layer of a semiconductor; (b) providing a laser beam modulated at a relatively high frequency; (c) focusing and directing said laser beam to one or more locations in sequence on an exposed surface of said layer to cause photocurrent to generate current flow variations in the layer; (d) monitoring said current flow variations to generate a doping profile of the layer along the path of one or more of said locations by detecting a signal representing said photocurrent variations.
Claim 16
Dependent Claim
19 words
The method according to claim 13, comprising modulating the laser beam at a frequency of at least 1 MHz.
Claim 17
Dependent Claim
22 words
The method according to claim 13, comprising the step of focusing the laser beam to a diameter of 1 μm or less.
Claim 18
Dependent Claim
25 words
The method according to claim 13, wherein said monitoring step comprises phase sensitive detecting the current flow for determining said photocurrent variations in the current.
Claim 19
Dependent Claim
23 words
The method according to claim 13, wherein said monitoring step comprises filtering the current flow for determining said photocurrent variations in the current.
Claim 20
Dependent Claim
23 words
The method according to claim 13, wherein said monitoring step comprises heterodyning the current flow for determining said photocurrent variations in the current.
References Cited (Backward Citations)
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