Patent US3875415A successfully refreshed from Google Patents.
US3875415A
Expired / Lapsed
US
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Method and apparatus for detecting a registration mark on a target such as a semiconductor wafer
Assignee: International Business Machines Corp
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Filing: 1974-01-28
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Granted: 1975-04-01
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Expires: 1994-01-28
Abstract
Abstract A square-shaped beam of charged particles is passed over a registration mark, which is formed by a depression in the surface of a semiconductor wafer. When the beam passes over one edge of the mark, a positive peak signal is produced while a negative peak signal is produced when the beam passes over the other edge of the mark. These positive and negative signals are compared with positive and negative threshold signals in comparators with an output signal being produced from each of the comparators when its threshold signal is crossed. This enables location of each of the edges of the mark to be determined. The positive and negative threshold signals are set for each of the areas of the wafer having one of the marks since different signal baseline voltages are produced by different areas of the wafer.
Inventors
- 👤 Ollie C Woodard
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 12:17
CPC Classifications
H; H01; H01J; H01J37/00; H01J37/30; H01J37/304
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
221 words
An apparatus for determining the location of a registration mark on a target including: means to sense the beginning of the registration mark and the end of the registration mark when the registration mark is scanned by a beam of charged particles; said sensing means including means to produce a first peak electrical signal at the beginning of the registration mark and a second peak electrical signal at the end of the registration mark with the two peak electrical signals being of opposite polarity; first means to produce a first threshold signal correlated to the first peak electrical signal and to a signal baseline voltage determined by the surface of the target in the area having the registration mark; second means to produce a second threshold signal correlated to the second peak electrical signal and to a signal baseline voltage determined by the surface of the target in the area having the registration mark; third means to produce a first signal when the first peak electrical signal crosses the first threshold signal; fourth means to produce a second signal when the second peak electrical signal crosses the second threshold signal; and means to determine the positions of the beginning and end of the registration mark in accordance with the positions of the beam when the first and second signals are produced.
Claim 2
Independent Claim
221 words
An apparatus for determining the location of a registration mark on a target including: means to sense the beginning of the registration mark and the end of the registration mark when the registration mark is scanned by a beam of charged particles; said sensing means including means to produce a first peak electrical signal at the beginning of the registration mark and a second peak electrical signal at the end of the registration mark with the two peak electrical signals being of opposite polarity; first means to produce a first threshold signal correlated to the first peak electrical signal and to a signal baseline voltage determined by the surface of the target in the area having the registration mark; second means to produce a second threshold signal correlated to the second peak electrical signal and to a signal baseline voltage determined by the surface of the target in the area having the registration mark; third means to produce a first signal when the first peak electrical signal crosses the first threshold signal; fourth means to produce a second signal when the second peak electrical signal crosses the second threshold signal; and means to determine the positions of the beginning and end of the registration mark in accordance with the positions of the beam when the first and second signals are produced.
Claim 3
Dependent Claim
18 words
The apparatus according to claim 1 including means to maintain the signal baseline voltage within a predetermined range.
Claim 4
Dependent Claim
23 words
The apparatus according to claim 2 including means to control the amplitude of each of the peak electrical signals with a predetermined range.
Claim 5
Dependent Claim
14 words
The apparatus according to claim 3 in which the target is a semiconductor wafer.
Claim 6
Dependent Claim
23 words
The apparatus according to claim 1 including means to control the amplitude of each of the peak electrical signals within a predetermined range.
Claim 7
Independent Claim
331 words
A method of locating a registration mark on a target defined by at least one pair of edges by moving a beam of charged particles over the area of the target having the registration mark in a plurality of line-by-line scans including: making a first scan over the area of the target having the registration mark to cause a signal baseline voltage to be within a predetermined range in accordance with the material of the area having the registration mark; making a second scan over the area of the target having the registration mark to ascertain the signal baseline voltage in accordance with the material of the area having the registration mark and to ascertain the highest positive and negative peak signals produced from the beam passing over the edges of the registration mark; selecting a percentage of the positive peak signal in comparison with the signal baseline voltage obtained during the second scan to produce a positive threshold signal for all scans after the second scan; selecting a percentage of the negative peak signal in comparison with the signal baseline voltage obtained during the second scan to produce a negative threshold signal for all scans after the second scan; producing a first signal when one of the positive and negative threshold signals is crossed by a signal produced by the beam passing over one of the pair of edges of the registration mark during a third scan; producing a second signal when the other of the positive and negative threshold signals is crossed by a signal produced by the beam passing over the other of the pair of edges of the registration mark during the third scan; making a plurality of additional scans to produce additional first and second signals; and utilizing the first and second signals in conjunction with the location of the beam during the scan in which each of the first and second signals is produced to locate the position of the registration mark on the target.
Claim 8
Independent Claim
331 words
A method of locating a registration mark on a target defined by at least one pair of edges by moving a beam of charged particles over the area of the target having the registration mark in a plurality of line-by-line scans including: making a first scan over the area of the target having the registration mark to cause a signal baseline voltage to be within a predetermined range in accordance with the material of the area having the registration mark; making a second scan over the area of the target having the registration mark to ascertain the signal baseline voltage in accordance with the material of the area having the registration mark and to ascertain the highest positive and negative peak signals produced from the beam passing over the edges of the registration mark; selecting a percentage of the positive peak signal in comparison with the signal baseline voltage obtained during the second scan to produce a positive threshold signal for all scans after the second scan; selecting a percentage of the negative peak signal in comparison with the signal baseline voltage obtained during the second scan to produce a negative threshold signal for all scans after the second scan; producing a first signal when one of the positive and negative threshold signals is crossed by a signal produced by the beam passing over one of the pair of edges of the registration mark during a third scan; producing a second signal when the other of the positive and negative threshold signals is crossed by a signal produced by the beam passing over the other of the pair of edges of the registration mark during the third scan; making a plurality of additional scans to produce additional first and second signals; and utilizing the first and second signals in conjunction with the location of the beam during the scan in which each of the first and second signals is produced to locate the position of the registration mark on the target.
Claim 9
Dependent Claim
18 words
The method according to claim 6 including removing prior positive and negative threshold signals during the first scan.
Claim 10
Dependent Claim
32 words
The method according to claim 7 including maintaining the amplitude of the signals produced by the beam passing over the edges of the registration mark within a predetermined range during the scans.
Claim 11
Dependent Claim
45 words
The method according to claim 8 in which prior positive and negative threshold signals are removed during the first scan by removing the signal baseline voltage, the positive peak voltage, and the negative peak voltage obtained during the second scan of the prior scan cycle.
Claim 12
Dependent Claim
14 words
The method according to claim 9 in which the target is a semiconductor wafer.
Claim 13
Dependent Claim
45 words
The method according to claim 7 in which prior positive and negative threshold signals are removed during the first scan by removing the signal baseline voltage, the positive peak voltage, and the negative peak voltage obtained during the second scan of the prior scan cycle.
Claim 14
Dependent Claim
14 words
The method according to claim 11 in which the target is a semiconductor wafer.
Claim 15
Dependent Claim
32 words
The method according to claim 6 including maintaining the amplitude of the signals produced by the beam passing over the edges of the registration mark within a predetermined range during the scans.
Claim 16
Dependent Claim
14 words
The method according to claim 13 in which the target is a semiconductor wafer.
Claim 17
Dependent Claim
31 words
The apparatus according to claim 1 including means to supply a bias signal to said producing means of said sensing means to maintain the signal baseline voltage within a predetermined range.
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) | 1978-03-31 | 1978-09-30 | 1979-04-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-03-31 | 1982-09-30 | 1983-04-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-03-31 | 1986-09-30 | 1987-04-01 | $7700.00 | Window Closed / Lapsed |