US5055871A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method and apparatus for enhancing illumination uniformity in wafer steppers using photochromic glass in the optical path
Assignee: LSI Corp
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Filing: 1989-10-05
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Granted: 1991-10-08
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Expires: 2009-10-05
Abstract
Abstract Enhanced uniformity of illumination is achieved in photolithography by interposing photochromic glass in the light path between the illuminator light source and a semiconductor wafer. In one embodiment of the invention, the photochromic glass is disposed immediately adjacent and before (upstream of) the mask. In another embodiment of the invention, the photochromic glass is disposed upstream of the mask, and an intermediate lens is disposed between the photochromic glass and the mask. In a still further embodiment of the invention, the photochromic glass is disposed in a reflector behind the illuminator light source. In other embodiments of the invention. The photochromic glass is disposed downstream of the mask. In yet another embodiment of the invention, the photochromic glass is exposed by two or more copies of a mask on a reticle to effect averaging. The photochromic glass is then used as a virtual mask to expose the wafer. Each of the described embodiments has its own advantages. Method and apparatus are disclosed.
Inventors
- 👤 Nicholas F. Pasch
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 09:06
CPC Classifications
G; G03; G03F; G03F7/00; G03F7/70; G03F7/70058; G03F7/70216; G03F7/70241
Claims Analysis
Total Claims: 35
Claim 1
Independent Claim
76 words
Photolithographic apparatus comprising: a light source disposed at the upstream end of an optical path; means for locating a mask downstream from the light source in the optical path; and means for locating a semiconductor wafer downstream from the means for locating the mask in the optical path; and a photochromic glass interposed in the optical path upstream of the means for locating a mask between the light source and the means for locating the mask.
Claim 2
Dependent Claim
76 words
Photolithographic apparatus comprising: a light source disposed at the upstream end of an optical path; means for locating a mask downstream from the light source in the optical path; and means for locating a semiconductor wafer downstream from the means for locating the mask in the optical path; and a photochromic glass interposed in the optical path upstream of the means for locating a mask between the light source and the means for locating the mask.
Claim 3
Dependent Claim
18 words
Photolithographic apparatus according to claim 1, further comprising: means for stepping a reticle containing a plurality of masks.
Claim 4
Dependent Claim
27 words
Photolithographic apparatus according to claim 1, wherein: the photochromic glass is interposed in the optical path in close juxtaposition with a mask disposed in the optical path.
Claim 5
Dependent Claim
50 words
Photolithographic apparatus according to claim 1, further comprising: a condensor lens disposed in the optical path upstream of the means for locating a mask; and an intermediate lens disposed between the mask and the condensor lens; wherein the photochromic glass is disposed between the condensor lens and the intermediate lens.
Claim 6
Dependent Claim
35 words
Photolithographic apparatus according to claim 1, further comprising: a condensor lens disposed in the optical path upstream of the means for locating a mask; and wherein the photochromic glass is coincident with the condensor lens.
Claim 7
Dependent Claim
19 words
Photolithographic apparatus according to claim 1, further comprising: a taking lens disposed between the mask and the semiconductor wafer.
Claim 8
Dependent Claim
24 words
Photolithographic apparatus according to claim 1, further comprising: a condensor lens disposed in the optical path upstream of the means for locating a mask.
Claim 9
Dependent Claim
24 words
Photolithographic apparatus according to claim 1, further comprising: a uniformizer located in the optical path upstream of the photochromic glass in the optical path.
Claim 10
Dependent Claim
27 words
Photolithographic apparatus according to claim 1, further comprising: an intermediate lens disposed in the optical path between the means for locating the mask and the photochromic glass.
Claim 11
Dependent Claim
19 words
Photolithographic apparatus according to claim 1, wherein: the photochromic glass is disposed in a reflector behind the light source.
Claim 12
Dependent Claim
43 words
Photolithographic illuminator assembly for use with photolithographic apparatus having means for locating a mask, comprising: a light source emitting light along a light path; and a photochromic glass disposed in the light path downstream of the light source and upstream of a mask.
Claim 13
Dependent Claim
43 words
Photolithographic illuminator assembly for use with photolithographic apparatus having means for locating a mask, comprising: a light source emitting light along a light path; and a photochromic glass disposed in the light path downstream of the light source and upstream of a mask.
Claim 14
Dependent Claim
20 words
Photolithographic illuminator according to claim 11, further comprising: a condensor lens disposed between the light source and the photochromic glass.
Claim 15
Dependent Claim
20 words
Photolithographic illuminator assembly according to claim 11, further comprising: a uniformizer interposed between the light source and the photochromic glass.
Claim 16
Independent Claim
56 words
A method of performing photolithography on a semiconductor wafer comprising: illuminating a semiconductor wafer with light from an illuminator, a light path being defined thereby; disposing a mask in the light path between the illuminator and the wafer; interposing a photochromic glass in the light path upstream of the mask between the illuminator and the mask.
Claim 17
Independent Claim
56 words
A method of performing photolithography on a semiconductor wafer comprising: illuminating a semiconductor wafer with light from an illuminator, a light path being defined thereby; disposing a mask in the light path between the illuminator and the wafer; interposing a photochromic glass in the light path upstream of the mask between the illuminator and the mask.
Claim 18
Dependent Claim
22 words
A method according to claim 14, wherein: the semiconductor wafer includes a layer of photoactive material; and the light is actinic light.
Claim 19
Dependent Claim
12 words
A method according to claim 15, wherein: the photoactive material is photoresist.
Claim 20
Dependent Claim
17 words
A method according to claim 15, wherein: the light is in the ultraviolet or near ultraviolet range.
Claim 21
Dependent Claim
16 words
A method according to claim 17, wherein: the light has a wavelength of approximately 436 nanometers.
Claim 22
Dependent Claim
16 words
A method according to claim 17, wherein: the light has a wavelength of approximately 365 nanometers.
Claim 23
Dependent Claim
22 words
A method according to claim 14, further comprising: interposing a uniformizer in the light path between the illuminator and the photochromic glass.
Claim 24
Dependent Claim
22 words
A method according to claim 14, wherein: the photochromic glass is interposed in the optical path in close juxtaposition with the mask.
Claim 25
Dependent Claim
46 words
A method according to claim 14, further comprising: disposing a condensor lens in the optical path upstream of the mask; and disposing an intermediate lens between the mask and the condensor lens; wherein the photochromic glass is disposed between the condensor lens and the intermediate lens.
Claim 26
Dependent Claim
31 words
A method according to claim 14, further comprising: disposing a condensor lens in the optical path upstream of the mask; and wherein the photochromic glass is coincident with the condensor lens.
Claim 27
Dependent Claim
19 words
A method according to claim 14, further comprising: disposing a taking lens between the mask and the semiconductor wafer.
Claim 28
Dependent Claim
20 words
A method according to claim 14, further comprising: disposing a uniformizer in the optical path upstream of the photochromic glass.
Claim 29
Dependent Claim
20 words
A method according to claim 14, further comprising: disposing a reticle containing a plurality of masks in the light path.
Claim 30
Independent Claim
50 words
A method of photolithographically image-averaging a multiplicity of mask images onto a semiconductor wafer comprising: exposing a stationary photochromic glass to a multiplicity of mask images to create a single virtual mask on the photochromic glass; and exposing a semiconductor wafer to an image projected by the single virtual mask.
Claim 31
Independent Claim
50 words
A method of photolithographically image-averaging a multiplicity of mask images onto a semiconductor wafer comprising: exposing a stationary photochromic glass to a multiplicity of mask images to create a single virtual mask on the photochromic glass; and exposing a semiconductor wafer to an image projected by the single virtual mask.
Claim 32
Dependent Claim
51 words
A method according to claim 27, wherein: the semiconductor wafer is exposed by the single virtual image on the photochromic glass within a period of time during which out of register mask images on the photochromic glass have faded to below a threshhold sufficient for effecting exposure of the semiconductor wafer.
Claim 33
Independent Claim
48 words
A method of lowering mask contrast in photolithographic apparatus having an illuminator and a mask disposed downstream of the illuminator, comprising: locating photochromic glass, of the type that is darkened when exposed to light, downstream of the mask and upstream of a wafer being exposed by the mask.
Claim 34
Independent Claim
48 words
A method of lowering mask contrast in photolithographic apparatus having an illuminator and a mask disposed downstream of the illuminator, comprising: locating photochromic glass, of the type that is darkened when exposed to light, downstream of the mask and upstream of a wafer being exposed by the mask.
Claim 35
Dependent Claim
23 words
A method according to claim 29, further comprising: disposing an intermediate lens in the optical path between the mask and the photochromic glass.
References Cited (Backward Citations)
US2420636A
Cited
US3436353A
Cited
US3160504A
Cited
US3441346A
Cited
US3598471A
Cited
US3680956A
Cited
US3758207A
Cited
US4025191A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1994-10-07 | 1995-04-08 | 1995-10-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-10-07 | 1999-04-08 | 1999-10-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-10-07 | 2003-04-08 | 2003-10-08 | $7700.00 | Window Closed / Lapsed |