Patent EP0352004A2 successfully refreshed from Google Patents.
EP0352004A2
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EP
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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: 1989-07-11
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Granted: —
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Expires: 2009-07-11
Abstract
Abstract The disclosure relates to a method for endpoint detection in a semiconductor wafer etching ysstem characterised in the steps of: 1) scanning a semiconductor wafer (10) with a narrowly focussed laser beam (24); 2) analyzing a reflected portion of the beam to determine a preferred parking spot (P) on a preferred flat area (#8) of the wafer; 3) parking the beams at the preferred spot; and 4) analyzing the reflected portion of the beam to determine when the preferred flat area has been etched through. The beam spot (18) of the laser beam (24) is amller than the width of the preferred flat area to eliminate noise generated at the transition boundaries of the flat area. Preferably, the wafer is scanned several times along the same beam path to permit the comparison of several scans to determine the preferred parking spot. The apparatus includes a beam forming assembled (62, 64, 66); a scanning assembly which causes the laser beam to scan across the wafer; a detection assembly (76) responsive to a portiom of the laser beam which is reflected off the wafer; and a controller (78) which operates the laser and the scanning assembly and which is responsive to an output of the detection assembly. When output of the detection assembly indicates a cessation of the characteristic etching curve, the controller develops an endpoint detection signal which can automatically shut down the etching system.
Inventors
- 👤 Peter Ebbing
- 👤 Manoocher Birang
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 17:10
CPC Classifications
B; B24; B24B; B24B37/00; B24B37/005; B24B37/013; B24D; B24D7/00; B24D7/12; G; G01; G01B; G01B11/00; G01B11/02; G01B11/026; G01B11/06; G01B11/0616; G01B11/0683; G02; G02B; G02B7/00; G02B7/28; G02B7/30; G02B7/32; G03; G03F; G03F7/00; G03F7/70; G03F7/70216; G03F7/70358; H; H10; H10P; H10P72/00; H10P72/04; H10P72/0402; H10P72/0418; H10P72/0421; H10P72/06; H10P72/0604; H10P74/00; H10P74/23; H10P74/238
Claims Analysis
Total Claims: 36
Claim 1
Independent Claim
96 words
A method for endpoint detection in a semiconductor wafer etching system comprising the steps of: scanning a semiconductor wafer surface with a narrowly focussed beam of radiant energy and detecting a reflected portion of said beam; analyzing said reflected portion to determine a preferred parking spot on a preferred flat area of said surface, said preferred flat area having a minimum transverse dimension greater than a spot size of said beam; parking said beam at said preferred spot; analyzing said reflected portion of said beam to determine when said preferred flat area has been etched through.
Claim 2
Independent Claim
96 words
A method for endpoint detection in a semiconductor wafer etching system comprising the steps of: scanning a semiconductor wafer surface with a narrowly focussed beam of radiant energy and detecting a reflected portion of said beam; analyzing said reflected portion to determine a preferred parking spot on a preferred flat area of said surface, said preferred flat area having a minimum transverse dimension greater than a spot size of said beam; parking said beam at said preferred spot; analyzing said reflected portion of said beam to determine when said preferred flat area has been etched through.
Claim 3
Dependent Claim
27 words
A method as claimed in claim 1 wherein said step of scanning said semiconductor wafer surface with said beam includes multiple scans along a substantially identical path.
Claim 4
Dependent Claim
31 words
A method as claimed in claim 2 wherein said step of analyzing said reflected portion includes analyzing a region of a first scan with a corresponding region of a second scan.
Claim 5
Dependent Claim
35 words
A method as claimed in claim 3 wherein said step of analyzing said reflected portions includes analyzing a series of regions of said first scan with a corresponding series of regions of said second scan.
Claim 6
Independent Claim
47 words
A method as claimed in any of claims 1 to 4 wherein said step of analyzing said reflected portion of said beam to determine when said surface at said preferred flat are has been etched through includes comparing an actual etcgubg cyrve with a projected etching curve.
Claim 7
Independent Claim
83 words
A method for finding a preferred parking spot for a laser beam of a laser beam interferometer comprising the steps of: making at least one scan along a scan path on a semiconductor wafer surface with a narrowly focussed laser beam and detecting a reflected portion of said beam; analyzing said reflected portion of said beam to determine a preferred parking spot within a preferred flat area having a minimum transverse dimension which is larger than a spot size of said laser beam.
Claim 8
Independent Claim
83 words
A method for finding a preferred parking spot for a laser beam of a laser beam interferometer comprising the steps of: making at least one scan along a scan path on a semiconductor wafer surface with a narrowly focussed laser beam and detecting a reflected portion of said beam; analyzing said reflected portion of said beam to determine a preferred parking spot within a preferred flat area having a minimum transverse dimension which is larger than a spot size of said laser beam.
Claim 9
Dependent Claim
50 words
A method as claimed in claim 6 wherein said spot size is sufficiently small such that a plurality of data values can be taken within said preferred flat area, thereby minimizing the effects of transitions and steps on a said semiconductor wafer surface which may surround said preferred flat area.
Claim 10
Dependent Claim
29 words
A method as claimed in claim 7 wherein multiple scans are made along said scan path, and wherein each of said multiple scans comprise a set of data values.
Claim 11
Dependent Claim
32 words
A method as claimed in claim 8 wherein a first subset of data values of first scan S1 is compared to a corresponding first subset of data values of second scan S2.
Claim 12
Dependent Claim
26 words
A method as claimed in claim 9 wherein said first subsets are compared to find the minimum difference S1S2 min between any two corresponding data values.
Claim 13
Dependent Claim
84 words
A method as claimed in claim 10 wherein a second subset of scan S1 is used to calculate a factor S1 max corresponding to the maximum difference between any two data values within said second subset of scan S1, and wherein a second subset of scan S2 is used to calculate a factor S2 max corresponding to the maximum difference between any two data values within said second subset of scan S2, wherein said second subsets are not necessarily different from said first subsets.
Claim 14
Dependent Claim
48 words
A method as claimed in claim 11 wherein a relative value R is calculated as follows: R = S1S2 min - [S1 max + S2 max ] where if R < 0 then R = 0; where said relative value R represents the relative desirability of said spot.
Claim 15
Dependent Claim
35 words
A method as claimed in claim 12 wherein a plurality of R values are calculated for scans S1 and S2, the maximum of which corresponds to a quality factor Q for scans S1 and S2.
Claim 16
Dependent Claim
33 words
A method as claimed in claim 13 wherein more than one pair of scans are compared to determine a plurality of Q values, the maximum of which corresponds to said preferred parking spot.
Claim 17
Independent Claim
71 words
A method for endpoint detection in a semiconductor wafer etching system comprising the steps of: parking a beam of radiant energy on a spot of a semiconductor wafer surface; detecting a reflected portion of said beam to determine an actual etching curve; and analyzing said reflected portion to determine when said surface at said preferred spot has been etched through by comparing said actual etching curve to a projected etching curve.
Claim 18
Independent Claim
71 words
A method for endpoint detection in a semiconductor wafer etching system comprising the steps of: parking a beam of radiant energy on a spot of a semiconductor wafer surface; detecting a reflected portion of said beam to determine an actual etching curve; and analyzing said reflected portion to determine when said surface at said preferred spot has been etched through by comparing said actual etching curve to a projected etching curve.
Claim 19
Dependent Claim
39 words
A method as claimed in claim 15 wherein endpoint is detected when the actual etching curve is greater than a predetermined fraction of the difference between a peak value of said actual etching curve and said projected etching curve.
Claim 20
Independent Claim
51 words
A method for focussing a beam of radiant energy comprising: scanning a beam of radiant energy across a test pattern comprising areas of differing reflectivity; detecting the variance in a reflected portion of said beam as it is scanned across said test pattern; and adjusting said beam to minimize said variance.
Claim 21
Independent Claim
51 words
A method for focussing a beam of radiant energy comprising: scanning a beam of radiant energy across a test pattern comprising areas of differing reflectivity; detecting the variance in a reflected portion of said beam as it is scanned across said test pattern; and adjusting said beam to minimize said variance.
Claim 22
Dependent Claim
43 words
A method as claimed in claim 17 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, wherein said first plurality of areas are of a variable width.
Claim 23
Dependent Claim
19 words
A method as claimed in claim 18 wherein said first plurality of areas comprise raised areas of said surface.
Claim 24
Dependent Claim
20 words
A method as claimed in claim 18 or claim 19 wherein said second plurality of areas are of variable width.
Claim 25
Dependent Claim
152 words
A laser interferometer endpoint detection system comprising: beam forming means adapted to produce a narrowly focussed beam spot; scanning means coupled to said beam forming means and adapted to scan said beam spot across a surface of a semiconductor wafer in discrete steps; detection means responsive to a reflected portion of said beam spot which is reflected from said semiconductor wafer; environmental isolation means for isolating said beam forming means and said detection means from said semiconductor wafer; and control means having an input coupled to said detection means and having an output coupled to said scanning means, said control means being operative to cause said scanning means to scan across a preferred flat area which is wider than said beam spot plus one discrete step, said control means being further operative to develop an endpoint detection signal when the output said detection means indicates the cessation of a characteristic etching curve.
Claim 26
Dependent Claim
152 words
A laser interferometer endpoint detection system comprising: beam forming means adapted to produce a narrowly focussed beam spot; scanning means coupled to said beam forming means and adapted to scan said beam spot across a surface of a semiconductor wafer in discrete steps; detection means responsive to a reflected portion of said beam spot which is reflected from said semiconductor wafer; environmental isolation means for isolating said beam forming means and said detection means from said semiconductor wafer; and control means having an input coupled to said detection means and having an output coupled to said scanning means, said control means being operative to cause said scanning means to scan across a preferred flat area which is wider than said beam spot plus one discrete step, said control means being further operative to develop an endpoint detection signal when the output said detection means indicates the cessation of a characteristic etching curve.
Claim 27
Dependent Claim
66 words
A laser interferometer endpoint detection system as claimed in claim 21 wherein said beam forming means comprises: a laser source adapted to produce a laser beam; beam expanding means positioned in the path of said laser beam and adapted to produce an expanded laser beam; and beam focussing means positioned in the path of said expanded laser beam and adapted to produce a focussed laser beam.
Claim 28
Dependent Claim
54 words
A laser interferometer endpoint detection system as claimed in claim 22 wherein said beam forming means further includes optical isolation means disposed between said laser source and said beam expanding means along said path of said laser beam, whereby said optical isolation means minimizes reflection of said laser beam back to said laser source.
Claim 29
Dependent Claim
19 words
A laser interferometer endpoint detection system as claimed in claim 23 wherein said optical isolation means includes polarizing means.
Claim 30
Dependent Claim
34 words
A laser interferometer endpoint detection system as as claimed in any of claims 21 to 24 wherein said detection means includes a photodetector and detection optics for focussing said reflected beam on said photodetector.
Claim 31
Dependent Claim
33 words
A laser interferometer endpoint detection system as claimed in any of Claims 21 to 25 wherein said environmental isolation means includes window means disposed between said beam forming mean sand said semiconductor wafer.
Claim 32
Dependent Claim
36 words
A laser interferometer endpoint detection system as claimed in Claim 26 wherein said window means is adapted to isolate thermally the beam forming means side of said window from the semiconductor wafer side of said window.
Claim 33
Dependent Claim
24 words
A laser interferometer endpoint detection system as claimed in Claim 26 or Claim 27 wherein said window means includes a plurality of spaced-apart panes.
Claim 34
Dependent Claim
26 words
A laser interferometer endpoint detection system as claimed in Claim 28 further comprising heating means for heating at least the pane closest to said semiconductor wafer.
Claim 35
Dependent Claim
32 words
A laser interferometer endpoint detection system as claimed in any of Claims 26 to 29 wherein said environmental isolation means further comprises enclosure means at least partially enclosing said beam forming means.
Claim 36
Dependent Claim
37 words
A laser interferometer endpoint detection system as claims in any of Claims 21 to 30 further comprising beam focussing means coupled to said beam forming means and adapted to focus said beam spot on said semiconductor wafer.
References Cited (Backward Citations)
No citation records indexed.
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