US3908118A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Cross correlation anomaly detection system
Assignee: California Institute of Technology
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Filing: 1973-09-27
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Granted: 1975-09-23
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Expires: 1993-09-27
Abstract
Abstract This invention provides a method and means for automatically inspecting the surface of an object, such as an integrated circuit chip, whereby the data obtained by the light reflected from the surface, caused by a scanning light beam, is automatically compared with data representing acceptable values for each unique surface. A signal output is provided indicative of acceptance or rejection of the chip. Acceptance is based on predetermined statistical confidence intervals calculated from known good regions of the object being tested, or their representative values. The method can utilize a known good chip, a photographic mask from which the I.C. was fabricated, or a computer stored replica of each pattern being tested.
Inventors
- 👤 Ernest Z Micka
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-22 23:44
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/84; G01N21/88; G01N21/95; G01N21/956; G01R; G01R31/00; G01R31/28; G01R31/302; G01R31/308
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
327 words
In a system for inspecting the surface of a test chip by deriving reflectance signals from a reflectance beam caused by scanning the surface of said test chip with a scanning light beam, using, as criteria for such inspection, data derived from an acceptable chip or chips, said data being in the form of a plurality of calculated terms arranged in a predetermined pattern in a first matrix, a rotation matrix of said first matrix, and acceptable ranges for metal, oxide and edge regions of said chip, the improvement comprising means for generating a plurality of first signals each representative of the product of K and a different on of said terms in said first matrix, where K is a constant selected to provide a desired inspection sensitivity, means for generating a plurality of second signals each representative of the product of K and a different one of said terms in said rotation matrix, means for generating a plurality threshold signals respectively representative of said acceptable ranges for metal, oxide and edge regions, means for simultaneously and sequentially selecting each of said plurality of first signals and said second signals as each element of the surface of said test chip is scanned by said scanning beam, means for representing the surface regions of an acceptable chip, means for deriving from said means for representing the surface regions of an acceptable chip in synchronism with the surface scan of said test chip signals representative of the region of the surface of an acceptable chip that should be scanned at that time by said scanning light beams, means responsive to said signals representative of the region of the surface of an acceptable chip for selecting the threshold signals for the region represented from said means for generating a plurality of threshold signals, means responsive to said first signals, said second signals and to said reflectance signals from said chip for generating a first function signal representative of the function
Claim 2
Dependent Claim
327 words
In a system for inspecting the surface of a test chip by deriving reflectance signals from a reflectance beam caused by scanning the surface of said test chip with a scanning light beam, using, as criteria for such inspection, data derived from an acceptable chip or chips, said data being in the form of a plurality of calculated terms arranged in a predetermined pattern in a first matrix, a rotation matrix of said first matrix, and acceptable ranges for metal, oxide and edge regions of said chip, the improvement comprising means for generating a plurality of first signals each representative of the product of K and a different on of said terms in said first matrix, where K is a constant selected to provide a desired inspection sensitivity, means for generating a plurality of second signals each representative of the product of K and a different one of said terms in said rotation matrix, means for generating a plurality threshold signals respectively representative of said acceptable ranges for metal, oxide and edge regions, means for simultaneously and sequentially selecting each of said plurality of first signals and said second signals as each element of the surface of said test chip is scanned by said scanning beam, means for representing the surface regions of an acceptable chip, means for deriving from said means for representing the surface regions of an acceptable chip in synchronism with the surface scan of said test chip signals representative of the region of the surface of an acceptable chip that should be scanned at that time by said scanning light beams, means responsive to said signals representative of the region of the surface of an acceptable chip for selecting the threshold signals for the region represented from said means for generating a plurality of threshold signals, means responsive to said first signals, said second signals and to said reflectance signals from said chip for generating a first function signal representative of the function
Claim 3
Dependent Claim
28 words
In a system as recited in claim 1 wherein said means for representing the surface regions of an acceptable chip includes a photographic representation of an acceptable chip.
Claim 4
Dependent Claim
43 words
In a system as recited in claim 1 wherein said means for representing the surface regions of an acceptable chip comprise means for storing signals representative of the surface of an acceptable chip in a distribution corresponding to that of said surface region.
Claim 5
Dependent Claim
24 words
In a system as recited in claim 1 wherein said means for representing said surface regions of an acceptable chip comprises an acceptable chip.
Claim 6
Dependent Claim
247 words
In a system for inspecting the surface of a test chip by deriving reflectance signals from a reflectance beam caused by scanning the surface of said test chip with a scanning light beam, using, as criteria for such inspection, data derived from an acceptable chip, or chips, said data being in the form of a plurality of calculated terms arranged in a predetermined pattern in a first matrix, a rotation matrix of said first matrix, and acceptable ranges for metal, oxide and edge regions of said chip, the improvement comprising means for generating first signals each representative of the product of K and a different one of the calculated terms in said first matrix, where K is an empirically determined sensitivity constant, means for generating second signals each representative of the product of K and a different one of the terms in said rotation matrix, meant for generating a plurality of threshold signals respectively representative of said acceptable ranges for said metal, oxide and edge regions of said chip, means for simultaneously selecting said first signals and said second signals sequentially as each element of the surface of said test chip is scanned by said scanning beam, means for selecting the threshold signals corresponding to an acceptable range for the part of the surface of the test chip being scanned, means responsive to said first signals, said second signals and to said reflectance signals from said chip for generating a first function signal representative of the function
Claim 7
Dependent Claim
247 words
In a system for inspecting the surface of a test chip by deriving reflectance signals from a reflectance beam caused by scanning the surface of said test chip with a scanning light beam, using, as criteria for such inspection, data derived from an acceptable chip, or chips, said data being in the form of a plurality of calculated terms arranged in a predetermined pattern in a first matrix, a rotation matrix of said first matrix, and acceptable ranges for metal, oxide and edge regions of said chip, the improvement comprising means for generating first signals each representative of the product of K and a different one of the calculated terms in said first matrix, where K is an empirically determined sensitivity constant, means for generating second signals each representative of the product of K and a different one of the terms in said rotation matrix, meant for generating a plurality of threshold signals respectively representative of said acceptable ranges for said metal, oxide and edge regions of said chip, means for simultaneously selecting said first signals and said second signals sequentially as each element of the surface of said test chip is scanned by said scanning beam, means for selecting the threshold signals corresponding to an acceptable range for the part of the surface of the test chip being scanned, means responsive to said first signals, said second signals and to said reflectance signals from said chip for generating a first function signal representative of the function
Claim 8
Dependent Claim
121 words
In apparatus as recited in claim 5 wherein said means for generating said first function signal includes means for subtracting said first signal from said reflectance signal to produce a first difference signal, means for multiplying said reflectance signal with said first difference signal to produce a first product signal, meAns for squaring said first difference signal to produce a first squared signal, means for integrating said first squared signal to produce a first integrated signal, means for integrating said first product signal to produce a second integrated signal, means for squaring said second integrated signal to produce a second squared signal, and means for dividing said first integrated signal by said second squared signal to produce said first function signal.
Claim 9
Dependent Claim
121 words
In apparatus as recited in claim 5 wherein said means for generating said second function signal includes meant for subtracting said second signal from said reflectance signal to produce a second difference signal, means for multiplying said second difference signal by said reflectance signal to produce a second product signal, means for integrating said second product signal to produce a third integrated signal, means for squaring said third integrated signal to produce a third squared signal, means for squaring said second difference signal to produce a fourth squared signal, means for integrating said fourth squared signal to produce a third integrated signal, and means for dividing said third squared signal by said fourth integrated signal to produce said second function signal.
Claim 10
Dependent Claim
128 words
In a system as recited in claim 5 wherein said means for selecting said threshold signals includes a transparency constituting a representation of the surface of said test chip wherein the metal regions, the oxide regions and the edge regions produce a separately identifiable modulation of light passing through said transparency, means for scanning said transparency with a light beam simultaneously and in synchronism with the scanning of said test chip, means for detecting the modulated light beam passing through said transparency and producing a metal identifying signal, or an oxide identifying signal, or an edge identifying signal in response thereto, and means responsive to the one of said identifying signals which is obtained for selecting the associated threshold signals to be applied to said means for comparing.
Claim 11
Dependent Claim
103 words
In a system as recited in claim 5 wherein said means for selecting said threshold signals includes means for storing signals representative of the surface regions of an acceptable chip in a distribution corresponding to that of said surface regions, means for sequentially reading out of said memory said signals representative of the surface regions of said acceptable chip while simultaneously scanning the surface of said test chip, and means responsive to each one of said signals representative of the surface regions which is read out of said memory for selecting the associated threshold signals to be applied to said means for comparing.
Claim 12
Dependent Claim
282 words
In a system for inspecting the surface of a test chip by deriving reflectance signals from a reflectance beam caused by scanning the surface of said test chip with a scanning light beam, using, as criteria for such inspection, data derived from an acceptable chip or chips, said data being in the form of a plurality of calculated terms arranged in a predetermined pattern in a first matrix, a rotation matrix of said first matrix, and acceptable ranges for metal, oxide and edge regions of said chip, the improved inspection method comprising generating a plurality of first signals each representative of the product of K and a different one of said terms in said rotation matrix, where k is a constant selected to provide a desired inspection sensitivity, generating a plurality of second signals each representative of the product and a different one of said terms in said transpose matrix, generating a plurality of threshold signals respectively representative of said acceptable ranges for metal, oxide and edge regions, simultaneously and sequentially selecting each of said plurality of first and second signals as each element of the surface of said test chip is Scanned by said scanning beam, generating in synchronism with the surface scan of said test chip signals representative of the region of the surface of an acceptable chip that should be scanned at that time by said scanning light beam, selecting the threshold signals indicated by said signals representative of the region of the surface of an acceptable chip that should be scanned at that time, generating, responsive to said first and second signals and to said reflectance signals from said chip, a first function signal representative of the function
Claim 13
Dependent Claim
282 words
In a system for inspecting the surface of a test chip by deriving reflectance signals from a reflectance beam caused by scanning the surface of said test chip with a scanning light beam, using, as criteria for such inspection, data derived from an acceptable chip or chips, said data being in the form of a plurality of calculated terms arranged in a predetermined pattern in a first matrix, a rotation matrix of said first matrix, and acceptable ranges for metal, oxide and edge regions of said chip, the improved inspection method comprising generating a plurality of first signals each representative of the product of K and a different one of said terms in said rotation matrix, where k is a constant selected to provide a desired inspection sensitivity, generating a plurality of second signals each representative of the product and a different one of said terms in said transpose matrix, generating a plurality of threshold signals respectively representative of said acceptable ranges for metal, oxide and edge regions, simultaneously and sequentially selecting each of said plurality of first and second signals as each element of the surface of said test chip is Scanned by said scanning beam, generating in synchronism with the surface scan of said test chip signals representative of the region of the surface of an acceptable chip that should be scanned at that time by said scanning light beam, selecting the threshold signals indicated by said signals representative of the region of the surface of an acceptable chip that should be scanned at that time, generating, responsive to said first and second signals and to said reflectance signals from said chip, a first function signal representative of the function
Claim 14
Dependent Claim
99 words
In a system as recited in claim 10 wherein said step of generating in synchronism with the surface scan of said test chip signals, signals representative of the region of the surface of an acceptable chip that should be scanned at that time comprises scanning a photographic representation of an acceptable chip with another light beam in synchronism with the scanning of the surface of said test chip to provide light signals modulated by said photographic representation, detecting said modulated light signals to provide signals indicative of either an oxide region or metal region or edge region being scanned.
Claim 15
Dependent Claim
71 words
In a system as recited in claim 10 wherein said step of generating in synchronism with the surface scan of said test chip signals, signals representative of the region of the surface of an acceptable chip that should be scanned at that time comprises storing signals representing the surface of an acceptable chip, and reading said stored signals out in synchronism with the scanning of the surface of said test chip.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-09-22 | 1979-03-24 | 1979-09-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-09-22 | 1983-03-24 | 1983-09-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-09-22 | 1987-03-24 | 1987-09-23 | $7700.00 | Window Closed / Lapsed |