Patent US5077464A successfully refreshed from Google Patents.
US5077464A
Expired / Lapsed
US
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Method and apparatus for endpoint detection in a semiconductor wafer etching system
Assignee: Applied Materials Inc
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Filing: 1991-02-05
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Granted: 1991-12-31
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Expires: 2011-02-05
Abstract
Abstract A method for focussing a radiant energy beam characterized by the steps of scanning a beam of radiant energy across a test pattern including areas of differing reflectivity, detecting the variance in a reflected portion of the scanned beam and adjusting the beam to minimize the variance. Preferably, the test pattern includes areas of varying widths, e.g. relatively non-reflective areas of varying widths separated by reflective areas of uniform widths. As the beam is scanned perpendicularly across the test pattern it will be highly reflected by the reflective areas and will be partially absorbed by the non-reflective areas. If the beam is wider than a non-reflective area a portion of the beam will be absorbed and a portion of the beam will be reflected, resulting in a greater total reflection than if the beam is narrower than the non-reflective region. In consequence, the intensity of the reflected beam will vary as the energy beam is scanned across the test pattern as it encounters non-reflective areas of varying widths. The amount of variance in the reflected beam is related to the width of the beam and, therefore, the beam can be focussed by adjusting the beam to minimize this variance.
Inventors
- 👤 Peter Ebbing
- 👤 Manoocher Birang
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 23:25
CPC Classifications
B; B24; B24B; B24B37/00; B24B37/005; B24B37/013; B24D; B24D7/00; B24D7/12; G; G01; G01B; G01B11/00; G01B11/02; G01B11/06; G01B11/0616; G01B11/0683; G03; G03F; G03F7/00; G03F7/70; G03F7/70216; G03F7/70358; H; H10; H10P; H10P72/00; H10P72/06; H10P72/0604; H10P74/00; H10P74/23; H10P74/238
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
104 words
A method of focussing a beam of radiant energy comprising: scanning a beam of radiant energy across a test pattern comprising areas of differing reflectivity, said test pattern including a first plurality of areas of a first reflectivity alternated with a second plurality of areas of a second reflectivity, said first plurality of areas being of variable width; detecting an intensity variance in a reflected portion of said beam as it is scanned across said first plurality of areas; and adjusting the focus of said beam to minimize said intensity variance of said reflected portion between successive areas of said first plurality of areas.
Claim 2
Independent Claim
104 words
A method of focussing a beam of radiant energy comprising: scanning a beam of radiant energy across a test pattern comprising areas of differing reflectivity, said test pattern including a first plurality of areas of a first reflectivity alternated with a second plurality of areas of a second reflectivity, said first plurality of areas being of variable width; detecting an intensity variance in a reflected portion of said beam as it is scanned across said first plurality of areas; and adjusting the focus of said beam to minimize said intensity variance of said reflected portion between successive areas of said first plurality of areas.
Claim 3
Dependent Claim
22 words
A method as claimed in claim 1 wherein said first plurality of areas and said second plurality of areas define separate planes.
Claim 4
Dependent Claim
17 words
A method as claimed in claim 1 wherein said second plurality of areas are of variable width.
Claim 5
Independent Claim
72 words
A method for focussing a beam of radiant energy comprising: (a) varying the focus of a beam of radiant energy; (b) scanning said beam of radiant energy across a test pattern comprising areas of differing reflectivity; (c) analyzing a reflected portion of said scanned beam against a pre-existing criteria to determine the relative focus of said beam; and (d) repeating steps a, b and c to improve the focus of said beam.
Claim 6
Independent Claim
72 words
A method for focussing a beam of radiant energy comprising: (a) varying the focus of a beam of radiant energy; (b) scanning said beam of radiant energy across a test pattern comprising areas of differing reflectivity; (c) analyzing a reflected portion of said scanned beam against a pre-existing criteria to determine the relative focus of said beam; and (d) repeating steps a, b and c to improve the focus of said beam.
Claim 7
Dependent Claim
25 words
A method as claimed in claim 4 wherein said pre-existing criteria includes criteria derived from a previous scan of said beam across said test pattern.
Claim 8
Dependent Claim
32 words
A method as claimed in claim 4 wherein said test pattern includes a first plurality of areas of a first reflectivity alternated with a second plurality of areas of a second reflectivity.
Claim 9
Dependent Claim
17 words
A method as claimed in claim 6 wherein said first plurality of areas are of variable width.
Claim 10
Dependent Claim
17 words
A method as claimed in claim 7 wherein said second plurality of areas are of variable width.
Claim 11
Independent Claim
84 words
An apparatus for focussing a beam of radiant energy comprising: a test pattern comprising areas of differing reflectivity; source means for generating a beam of radiant energy; means for varying the focus of said beam; means for scanning said beam across a surface of said test pattern; detection means for detecting a portion of said beam reflected from said test pattern; and analysis means for analyzing the reflected portion of said beam against a pre-existing criteria to determine the relative focus of said beam.
Claim 12
Independent Claim
84 words
An apparatus for focussing a beam of radiant energy comprising: a test pattern comprising areas of differing reflectivity; source means for generating a beam of radiant energy; means for varying the focus of said beam; means for scanning said beam across a surface of said test pattern; detection means for detecting a portion of said beam reflected from said test pattern; and analysis means for analyzing the reflected portion of said beam against a pre-existing criteria to determine the relative focus of said beam.
Claim 13
Dependent Claim
26 words
An apparatus as claimed in claim 9 wherein said pre-existing criteria includes criteria derived from a previous scan of said test beam across said test pattern.
Claim 14
Dependent Claim
32 words
An apparatus as claimed in claim 9 wherein said test pattern includes a first plurality of areas of a first reflectivity alternated with a second plurality of areas of a second reflectivity.
Claim 15
Dependent Claim
17 words
An apparatus as claimed in claim 11 wherein said first plurality of areas are of variable width.
Claim 16
Dependent Claim
17 words
An apparatus as claimed in claim 12 wherein said second plurality of areas are of variable width.
Claim 17
Dependent Claim
86 words
A target useful for focussing a beam of radiant energy comprising: a body having a test surface provided with a first plurality of areas of a first reflectivity alternating with a second plurality of areas of a second reflectivity, said first plurality of areas being of variable width ranging from a width greater than the width of a focussed beam spot to a width less than the width of a focussed beam spot, said first plurality of areas being varied in width in a regular pattern.
Claim 18
Dependent Claim
86 words
A target useful for focussing a beam of radiant energy comprising: a body having a test surface provided with a first plurality of areas of a first reflectivity alternating with a second plurality of areas of a second reflectivity, said first plurality of areas being of variable width ranging from a width greater than the width of a focussed beam spot to a width less than the width of a focussed beam spot, said first plurality of areas being varied in width in a regular pattern.
Claim 19
Dependent Claim
18 words
A target as recited in claim 14 wherein said second plurality of areas are of substantially constant width.
Claim 20
Dependent Claim
17 words
A target as recited in claim 14 wherein said second plurality of areas are of variable width.
Claim 21
Dependent Claim
27 words
A target as recited in claim 14 wherein said first plurality of areas are in a different plane of said surface than said second plurality of areas.
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) | 1994-12-30 | 1995-07-01 | 1995-12-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-12-30 | 1999-07-01 | 1999-12-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-12-30 | 2003-07-01 | 2003-12-31 | $7700.00 | Window Closed / Lapsed |