US4579760A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Wafer shape and method of making same
Assignee: International Business Machines Corp
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Filing: 1985-01-08
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Granted: 1986-04-01
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Expires: 2005-01-08
Abstract
Abstract A semiconductor wafer shape which when subjected to a simultaneous polishing of both wafer surfaces produces a wafer of superior flatness and surface finish, the said wafer having a diametral cross-sectional shape like that of a "dogbone" wherein the wafer is thinner in its medial region than it is in the peripheral region and has rounded edges, this shape resulting from a chemical thinning operation.
Inventors
- 👤 James R. Hause
- 👤 Eric Mendel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 08:29
CPC Classifications
H; H10; H10P; H10P90/00; H10P90/12; H10P90/18; H10D; H10D62/00; H10D62/10; H10D62/117; H10P50/00; H10P50/60; H10P50/64; H10P50/642; H10P90/126; H10W; H10W46/00; H10W46/201; Y; Y10; Y10T; Y10T428/00; Y10T428/21; Y10T428/219; Y10T428/24; Y10T428/24942; Y10T428/2495
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
102 words
An improved semiconductor wafer shape, which when subjected to a subsequent polishing operation, in which both surfaces are simultaneously free-polished, produces a finished wafer having improved surface flatness and parallelism for the fabrication of very large scale integrated circuit devices, characterized by; The said wafer has a diametral cross-sectional shape wherein (a) The thickness of the wafer varies smoothly from a thin portion in the medial region of the wafer to a thicker portion at the peripheral region of the wafer, and; (b) The edges of the wafer are rounded whereby the cross-section can be visualized as having a "dogbone" like shape.
Claim 2
Dependent Claim
102 words
An improved semiconductor wafer shape, which when subjected to a subsequent polishing operation, in which both surfaces are simultaneously free-polished, produces a finished wafer having improved surface flatness and parallelism for the fabrication of very large scale integrated circuit devices, characterized by; The said wafer has a diametral cross-sectional shape wherein (a) The thickness of the wafer varies smoothly from a thin portion in the medial region of the wafer to a thicker portion at the peripheral region of the wafer, and; (b) The edges of the wafer are rounded whereby the cross-section can be visualized as having a "dogbone" like shape.
Claim 3
Dependent Claim
54 words
The wafer shape as claimed in claim 1 wherein; The difference in thickness (ΔT) between the thinner medial region and the thicker peripheral region satisfies the following relationship: ΔT=aD wherein ΔT=the difference between the respective thicknesses D=the diameter of the wafer a=a dimensionless constant within the range from 5×10 -6 to 1×10 -4 .
Claim 4
Dependent Claim
51 words
The wafer shape as claimed in claims 1 or 2 wherein; the edges of the wafer are rounded with a radius of curvature (R) satisfying the following relationship: R=b(T) wherein R=radius of curvature of the rounded edge T=thickness of the wafer b=a dimensionless constant within the range of 0.01 to 0.15.
Claim 5
Dependent Claim
18 words
The wafer shape as claimed in claim 1 wherein the shape is produced by a chemical thinning operation.
Claim 6
Dependent Claim
112 words
The wafer shape as claimed in claim 4 wherein the chemical thinning comprises the steps of: (a) Including the wafer coaxially among a nest of spaced apart wafers wherein the spacing (S) between the wafers has a dimension equal to S=bD wherein S=the linear distance separating adjacent wafers D=diameter of the wafers b=dimensionless constant within the range of 0.016 to 0.200. (b) Immersing the thus-nested wafers in an etching solution having an etch rate for the semiconductor material in the range from 0.10 to 0.53 microns per second. (c) and rotating the thus-immersed wafers at a speed of from 50 RPM to 110 RPM for a time between 2 and 5 minutes.
Claim 7
Dependent Claim
24 words
The wafer shape as claimed in claim 5 wherein the preferred spacing between wafers having a nominal diameter of 3 inches is 3 mm.
Claim 8
Dependent Claim
24 words
The wafer shape as claimed in claim 5 wherein the preferred spacing between wafers having a nominal diameter of 5 inches is 7 mm.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-03-31 | 1989-09-30 | 1990-04-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-03-31 | 1993-09-30 | 1994-04-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-03-31 | 1997-09-30 | 1998-04-01 | $7700.00 | Window Closed / Lapsed |