US3924113A
Expired / Lapsed
US
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Electron beam registration system
Assignee: International Business Machines Corp
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Filing: 1973-06-08
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Granted: 1975-12-02
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Expires: 1993-06-08
Abstract
Abstract In semiconductor manufacture, very accurate patterns must be formed in the photoresist on the surface of the semiconductor material. Chips are formed on a semiconductor wafer utilizing a beam of charged particles to expose the photoresist material on the surface of the semiconductor. If the plurality of chips, is to have the same characteristics and pattern, it is necessary that the electrons or beam of charged particles be moved such that any point within the field to which the beam is applied is always reached by the same history. This requires that patterns produced by an electron beam be properly registered with respect to previously generated patterns. This registration is accomplished by scanning previously placed registration marks on the chip with a beam of electrons and monitoring the reflected or back-scattered electrons to determine where the beam crosses said registration marks. The method disclosed herein is a system of processing the signals encountered during beam contact with the registration marks on the chip usually at the four corners thereof, whereby the location of the marks is accurately determined. This is accomplished by first improving the signal to noise ratio of the detected signal followed by a rapid crosscorrelation between the averaged signal and another signal having certain specific and especially desirable characteristics. The final step utilizes a least squares curve fitting procedure tuned up to extract the essential parameter, that is the center of the cross-correlation, with a minimum of on-line computation.
Inventors
- 👤 Charles D Gill
- 👤 Philip M Ryan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 13:36
CPC Classifications
H; H01; H01J; H01J37/00; H01J37/30; H01J37/304; H01J37/3045; H10; H10P; H10P95/00
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
69 words
A method for extracting the true position of a random noise corrupted signal with respect to a pre-determined signal, comprising multiple sampling of said random noise corrupted signal and adding corresponding points of said multiple samples and cross correlating said added samples with said pre-determined signal and extracting from a suitable portion of said cross-correlation an expression capable of determining the center of the original random noise corrupted signal.
Claim 2
Independent Claim
69 words
A method for extracting the true position of a random noise corrupted signal with respect to a pre-determined signal, comprising multiple sampling of said random noise corrupted signal and adding corresponding points of said multiple samples and cross correlating said added samples with said pre-determined signal and extracting from a suitable portion of said cross-correlation an expression capable of determining the center of the original random noise corrupted signal.
Claim 3
Dependent Claim
14 words
A method in accordance with claim 1 wherein said multiple sampled signal is digitized.
Claim 4
Dependent Claim
21 words
A method in accordance with claim 1 wherein said noise-corrupted signal emanates from back-scattered electrons of a beam of charged particles.
Claim 5
Dependent Claim
24 words
A method in accordance with claim 1 wherein said center of the first noise-corrupted signal is determined by a least squares curve fitting technique.
Claim 6
Dependent Claim
17 words
A method in accordance with claim 1 wherein said added sample is stored in a suitable memory.
Claim 7
Independent Claim
90 words
A method of registering a sweeping beam relative to an object bearing a registration mark or marks representing a reference position on said object comprising serially scanning said registration mark or marks with a beam of charged particles and adding corresponding points of each scan of a resulting current of back-scatter particles and storing the sum in a memory and cross-correlating the stored scan sum with an ideal signal and extracting from a suitable portion of the cross-correlation an expression capable of determining the center of the original noise-corrupted signal.
Claim 8
Independent Claim
90 words
A method of registering a sweeping beam relative to an object bearing a registration mark or marks representing a reference position on said object comprising serially scanning said registration mark or marks with a beam of charged particles and adding corresponding points of each scan of a resulting current of back-scatter particles and storing the sum in a memory and cross-correlating the stored scan sum with an ideal signal and extracting from a suitable portion of the cross-correlation an expression capable of determining the center of the original noise-corrupted signal.
Claim 9
Dependent Claim
24 words
A method in accordance with claim 6 wherein said center of the original noise-corrupted signal is determined by a least square curve fitting technique.
Claim 10
Dependent Claim
169 words
Apparatus for providing the true position of a noise corrupted signal comprising: means for sampling said noise corrupted signal and providing a binary value representative of the amplitude of the sampled noise corrupted signal; adder means operatively associated with and responsive to said means for sampling, said adding means also being operatively associated with and responsive to binary signals provided by an electronic memory; said adder means adding the data contained in a selected address of memory to the sampled noise corrupted signal and providing said result to the said same selected address of electronic memory; a second electronic memory storing a predetermined binary pattern; gating means electrically connected between said first electronic memory and said adding means for transferring data from said first electronic memory to said adding means under the control of said second electronic memory, and output means for providing the output of said adding means to a computing means for determining the center of a waveform representative of the binary output of said adding means.
Claim 11
Dependent Claim
169 words
Apparatus for providing the true position of a noise corrupted signal comprising: means for sampling said noise corrupted signal and providing a binary value representative of the amplitude of the sampled noise corrupted signal; adder means operatively associated with and responsive to said means for sampling, said adding means also being operatively associated with and responsive to binary signals provided by an electronic memory; said adder means adding the data contained in a selected address of memory to the sampled noise corrupted signal and providing said result to the said same selected address of electronic memory; a second electronic memory storing a predetermined binary pattern; gating means electrically connected between said first electronic memory and said adding means for transferring data from said first electronic memory to said adding means under the control of said second electronic memory, and output means for providing the output of said adding means to a computing means for determining the center of a waveform representative of the binary output of said adding means.
Claim 12
Dependent Claim
21 words
Apparatus as in claim 8 wherein said center of the original noise-corrupted signal is determined by a least curve fitting technique.
Claim 13
Dependent Claim
202 words
Apparatus for locating the precise position of registration marks on a semiconductor substrate comprising: a semiconductor substrate having registration marks thereon with a beam of charged particles impinging on said registration marks; means for sampling back-scattered particles emanating from said semiconductor substrate and for converting the analog level of said back scattered particles to a binary value representative of the resulting current from said back scattered particles; adder means operatively associated with and responsive to said means for sampling, said adding means also being operatively associated with and responsive to binary signals provided by an electronic memory; said adder means adding the data contained in a selected address of memory to the sampled noise corrupted signal and providing said result to the said same selected address of electronic memory; a second electronic memory storing a predetermined binary pattern; gating means electrically connected between said first electronic memory and said adding means for transferring data from said first electronic memory to said adding means under the control of said second electronic memory; and output means for providing the output of said adding means to a computing means for determining the center of a waveform representative of the binary output of said adding means.
Claim 14
Dependent Claim
202 words
Apparatus for locating the precise position of registration marks on a semiconductor substrate comprising: a semiconductor substrate having registration marks thereon with a beam of charged particles impinging on said registration marks; means for sampling back-scattered particles emanating from said semiconductor substrate and for converting the analog level of said back scattered particles to a binary value representative of the resulting current from said back scattered particles; adder means operatively associated with and responsive to said means for sampling, said adding means also being operatively associated with and responsive to binary signals provided by an electronic memory; said adder means adding the data contained in a selected address of memory to the sampled noise corrupted signal and providing said result to the said same selected address of electronic memory; a second electronic memory storing a predetermined binary pattern; gating means electrically connected between said first electronic memory and said adding means for transferring data from said first electronic memory to said adding means under the control of said second electronic memory; and output means for providing the output of said adding means to a computing means for determining the center of a waveform representative of the binary output of said adding means.
Claim 15
Dependent Claim
18 words
Apparatus as in claim 10 wherein said registration mark comprises: a stripe consisting of an oxide of silicon.
Claim 16
Dependent Claim
16 words
Apparatus as in claim 10 wherein said registration mark comprises: a plurality of silicon oxide stripes.
Claim 17
Dependent Claim
30 words
Appparatus as in claim 10 wherein said registration mark comprises: a plurality of oxide stripes at least two of said stripes being placed transverse to at least two additional stripes.
Claim 18
Dependent Claim
29 words
Apparatus as in claim 10 wherein at least one registration mark is placed at each of the four corners of a field to be defined by said registration marks.
References Cited (Backward Citations)
US3328795A
Cited
US3329813A
Cited
US3535516A
Cited
US3614736A
Cited
US3646333A
Cited
US3745317A
Cited
US3644899A
Cited
US3717756A
Cited
US3777133A
Cited
US3823398A
Cited
US3718813A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-12-01 | 1979-06-02 | 1979-12-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-12-01 | 1983-06-02 | 1983-12-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-12-01 | 1987-06-02 | 1987-12-02 | $7700.00 | Window Closed / Lapsed |