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US3798754A Expired / Lapsed US ⏱️ 0.0 years remaining

Semiconductor strain gage and method of fabricating same

Assignee: Motorola Solutions Inc
•
Filing: 1972-05-15
•
Granted: 1974-03-26
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Expires: 1992-05-15
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Abstract

Abstract A piezoresistive semiconductor strain gage for transforming mechanical stress into a changed resistance of the semiconductor and therefore a changed electrical current therethrough representative of the amount of stress is described. Also described is a method of fabricating the strain gage that is reliable and results in each produced strain gage having the characteristics of all of the others. The strain gage is comprised of a piezoresistive silicon body having enlarged ends. A KOH etch is made in each end and an epitaxial layer is therein. THEREIN. The epitaxial layer is of the same conductivity type as the piezoresistive silicon but is much more heavily doped to provide low resistance paths to solderable contacts connected to the epitaxially grown material. The combination of enlarged ends and reduced center provides stress amplification, resulting in a greater sensitivity of the strain gage.

Inventors

  • 👤 J Price
  • 👤 I Lesk

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-10-25 05:38
CPC Classifications
H; H10; H10D; H10D48/00; H10D48/50; G; G01; G01L; G01L1/00; G01L1/18; H10D99/00; H10P; H10P50/00; H10P50/60; H10P50/64; H10P50/642; H10P50/644; H10P95/00; Y; Y10; Y10S; Y10S148/00; Y10S148/05; Y10S148/051; Y10S148/085; Y10S438/00; Y10S438/928; Y10T; Y10T29/00; Y10T29/42; Y10T29/49; Y10T29/49002; Y10T29/49082; Y10T29/49103

Claims Analysis

Total Claims: 7
Claim 1
Independent Claim 39 words
The method of claim 1 wherein the monocrystalline substrate is comprised of N conductivity type silicon cut along the 100 crystallographic plane and the epitaxial growth is comprised of N conductivity type silicon more heavily doped then the substrate.
Claim 2
Dependent Claim 39 words
The method of claim 1 wherein the monocrystalline substrate is comprised of N conductivity type silicon cut along the 110 crystallographic plane and the epitaxial growth is comprised of N conductivity type silicon, more heavily doped than the substrate.
Claim 3
Dependent Claim 21 words
The method of claim 2 wherein each of the etching steps is accomplished through the use of KOH as an etchant.
Claim 4
Dependent Claim 29 words
The method of claim 4 further comprising, before the step of etching to a first depth, the step of depositing silicon nitride on the bottom surface of the substrate.
Claim 5
Dependent Claim 48 words
The method of claim 5 further comprising, after the step of growing epitaxial monocrystalline semiconductive material, the steps of: g. polishing the top surface of the substrate to smooth the epitaxial growth; and h. sirtl etching the top surface of the substrate to make the epitaxial growth visible.
Claim 6
Dependent Claim 64 words
The method of claim 6 wherein the step of forming the electrical contacts further comprises: e. i. evaporating aluminum over thE gage; ii. removing the evaporated aluminum except for the desired terminal areas; iii. evaporating successively, through a mask, over the remaining aluminum, chromium, copper, and gold; and iv. depositing a mixture of lead and tin over the evaporated metals to form solderable terminals.
Claim 7
Dependent Claim 73 words
The method of claim 7 wherein the step of removing material from the bottom side of the substrate further comprises: g. i. applying an adhesive wax to the top surface of a plate; ii. contacting the waxed top surface of the plate with the substrate causing adhesion between the plate and the substrate; and iii. lapping and polishing from the bottom surface of the substrate until a desired thickness of gage is reached.

References Cited (Backward Citations)

US3331124A Cited
US3351880A Cited
US3369290A Cited
US3492513A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1977-03-25 1977-09-24 1978-03-26 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1981-03-25 1981-09-24 1982-03-26 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1985-03-25 1985-09-24 1986-03-26 $7700.00 Window Closed / Lapsed

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