US4039370A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Optically monitoring the undercutting of a layer being etched
Assignee: RCA Corp
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Filing: 1976-06-21
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Granted: 1977-08-02
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Expires: 1996-06-21
Abstract
Abstract A technique for optically monitoring the undercutting of a layer of material being selectively etched beneath a pattern of masking material in an etchant comprises forming on a layer of the material being etched a diffraction grating pattern including spaced strips of masking material having a strip width W, exposing the diffraction grating pattern, while positioned in the etchant, to a beam of monochromatic light, whereby the grating pattern together with the layer of material therebeneath functions as a relief pattern which diffracts the beam of light into diffracted beams of various orders, and then monitoring certain of said diffracted beams to determine when a sharp decrease in the intensity thereof occurs, such a sharp decrease indicating an undercutting equal to a distance of W/2.
Inventors
- 👤 Hans Peter Kleinknecht
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 07:28
CPC Classifications
G; G01; G01B; G01B11/00; G01B11/02; Y; Y10; Y10S; Y10S359/00; Y10S359/90
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
132 words
A method of optically monitoring the undercutting of a layer of material being selectively etched beneath a pattern of masking material disposed thereon in an etchant comprising the steps of: forming on a layer of the material being etched a diffraction grating pattern including spaced strips of masking material having a strip width W; exposing said diffracion grating pattern, while positioned in said etchant, to a beam of monochromatic light, whereby said diffraction grating pattern and the layer of material therebeneath function as a relief pattern, diffracting said beam of monochromatic light into a diffraction spectrum including diffracted beams of various orders; and monitoring certain of said diffracted beams to determine when a sharp decrease in the intensity thereof occurs, said sharp decrease indicating an undercutting equal to a distance of W/2.
Claim 2
Independent Claim
132 words
A method of optically monitoring the undercutting of a layer of material being selectively etched beneath a pattern of masking material disposed thereon in an etchant comprising the steps of: forming on a layer of the material being etched a diffraction grating pattern including spaced strips of masking material having a strip width W; exposing said diffracion grating pattern, while positioned in said etchant, to a beam of monochromatic light, whereby said diffraction grating pattern and the layer of material therebeneath function as a relief pattern, diffracting said beam of monochromatic light into a diffraction spectrum including diffracted beams of various orders; and monitoring certain of said diffracted beams to determine when a sharp decrease in the intensity thereof occurs, said sharp decrease indicating an undercutting equal to a distance of W/2.
Claim 3
Dependent Claim
18 words
A method as recited in claim 1, wherein said relief pattern is utilized as a reflection phase grating.
Claim 4
Dependent Claim
25 words
A method as recited in claim 2, wherein said diffraction grating pattern comprises a pluraliy of diffracton gratings having spaced strips respectively of different widths.
Claim 5
Dependent Claim
27 words
A method as recited in claim 3, wherein said diffraction gratings are parallel to each other and have different periods equal, respectively, to twice the strip widths.
Claim 6
Dependent Claim
30 words
A method as recited in claim 4, wherein said beam of monochromatic light strikes said diffraction gratings uniformly at an angle acute to the plane of said diffraction grating pattern.
Claim 7
Dependent Claim
30 words
A method a recited in claim 4, wherein said beam of monochromatic light strikes said diffraction gratings uniformly at an angle perpendicular to the plane of said diffraction grating pattern.
Claim 8
Dependent Claim
50 words
A method as recited in claim 3, wherein said diffraction gratings are rotated by 45° from one grating to the next and have the same periodicity, and wherein said beam of monochromatic light strikes said diffraction gratings uniformly at an angle perpendicular to the plane of said diffraction grating pattern.
Claim 9
Dependent Claim
25 words
A method as recited in claim 1, wherein the step of monitoring certain of said diffracted beams is performed by monitoring first order beams only.
Claim 10
Dependent Claim
27 words
A method as recited in claim 8, wherein the monitoring step is performed by utilizing photodectors placed respectively at angular positions to receive said first order beams.
Claim 11
Dependent Claim
14 words
A method as recited in claim 9, wherein said photodectors are silicon PIN diodes.
Claim 12
Dependent Claim
17 words
A method as recited in claim 1, wherein said beam on monochromatic light is a laser beam.
Claim 13
Dependent Claim
19 words
A method as recited in claim 1, wherein said spaced strips of said masking material are noncontinuous randomly-dashed strips.
Claim 14
Dependent Claim
21 words
A method as recited in claim 1, wherein said pattern of masking material and said strips of masking material are photoresist.
Claim 15
Dependent Claim
22 words
A method as recited in claim 1, wherein said material being etched is silicon dioxide and is disposed on a silicon substrate.
Claim 16
Dependent Claim
50 words
A method as recited in claim 14, wherein the layer of material having said diffraction grating pattern formed thereon comprises a portion of the same layer of material being selectively etched beneath said pattern of masking material, and wherein said portion is disposed on a knock-out area of said substrate.
Claim 17
Independent Claim
130 words
An apparatus for optically monitoring the undercutting of a layer of material being selectively etched beneath a pattern of masking material disposed thereon in an etchant tank comprising: a diffraction grating pattern including spaced strips of masking material having a strip width W disposed on a layer of the material being etched, said diffraction grating pattern being positioned in said etchant within said tank; a monochromatic light source positioned so that a beam of said light strikes said diffraction grating pattern, whereby said beam of light is diffracted into a diffraction spectrum including diffracted beams of various orders; and means for monitoring sharp decreases in the intensity of certain of said diffracted beams, whereby a sharp decrease in the intensity thereof indicates an undercutting equal to a distance of W/2.
Claim 18
Independent Claim
130 words
An apparatus for optically monitoring the undercutting of a layer of material being selectively etched beneath a pattern of masking material disposed thereon in an etchant tank comprising: a diffraction grating pattern including spaced strips of masking material having a strip width W disposed on a layer of the material being etched, said diffraction grating pattern being positioned in said etchant within said tank; a monochromatic light source positioned so that a beam of said light strikes said diffraction grating pattern, whereby said beam of light is diffracted into a diffraction spectrum including diffracted beams of various orders; and means for monitoring sharp decreases in the intensity of certain of said diffracted beams, whereby a sharp decrease in the intensity thereof indicates an undercutting equal to a distance of W/2.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-08-01 | 1981-01-31 | 1981-08-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-08-01 | 1985-01-31 | 1985-08-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-08-01 | 1989-01-31 | 1989-08-02 | $7700.00 | Window Closed / Lapsed |