US4071397A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Silicon metallographic etch
Assignee: Motorola Solutions Inc
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Filing: 1973-07-02
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Granted: 1978-01-31
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Expires: 1993-07-02
Abstract
Abstract A metallographic etch is disclosed which removes silicon at a very low rate. The removal of the silicon at a low rate means that the etch is highly controlled. Additional characteristics of the metallographic etch are that it is non-selective and it removes the silicon uniformly. Its special uses are related to an etch which is specially adapted for minimizing the Q ss charge on a silicon surface, as well as for removing work damage on wafers in which very shallow junction devices are to be formed.
Inventors
- 👤 Isabelle E. Estreicher
- 👤 James B. Price
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 17:48
CPC Classifications
H; H10; H10P; H10P90/00; H10P90/12; H10P90/126; H10P50/00; H10P50/60; H10P50/64; H10P50/642
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
63 words
A metallographic etch for use in the manufacture of semiconductor devices for the removal of work damaged silicon material at a uniform rate of 280A ±1% per minute, comprising: a mixture of nitric acid to hydrofluoric acid having a ratio by volume of mixture lying within the range of 600:1 to 750:1 at a temperature within the range of 23° to 25° C.
Claim 2
Dependent Claim
63 words
A metallographic etch for use in the manufacture of semiconductor devices for the removal of work damaged silicon material at a uniform rate of 280A ±1% per minute, comprising: a mixture of nitric acid to hydrofluoric acid having a ratio by volume of mixture lying within the range of 600:1 to 750:1 at a temperature within the range of 23° to 25° C.
Claim 3
Dependent Claim
66 words
In the manufacture of semiconductor devices for the removal of work damaged silicon wafer in a uniform and non-selective manner without texturing the surface of the silicon wafer, the process comprising the steps of: removing less than 3000A of work damaged silicon using an etch of nitric acid and hydrofluoric acid having a ratio by volume of mixture lying within the range of 600:1 to 750:1.
Claim 4
Dependent Claim
66 words
In the manufacture of semiconductor devices for the removal of work damaged silicon wafer in a uniform and non-selective manner without texturing the surface of the silicon wafer, the process comprising the steps of: removing less than 3000A of work damaged silicon using an etch of nitric acid and hydrofluoric acid having a ratio by volume of mixture lying within the range of 600:1 to 750:1.
Claim 5
Dependent Claim
69 words
In a process for use in the manufacture of MOS devices for stabilizing the threshold voltage of such a MOS device the improvement comprising the step of: etching a lapped and polished wafer in which such MOS devices are built, in an etchant solution of a mixture of nitric acid and hydrofluoric acid having a ratio by volume of mixture lying within the range of 600:1 to 750:1 respectively.
Claim 6
Dependent Claim
69 words
In a process for use in the manufacture of MOS devices for stabilizing the threshold voltage of such a MOS device the improvement comprising the step of: etching a lapped and polished wafer in which such MOS devices are built, in an etchant solution of a mixture of nitric acid and hydrofluoric acid having a ratio by volume of mixture lying within the range of 600:1 to 750:1 respectively.
Claim 7
Dependent Claim
26 words
The process as recited in claim 3 wherein the etchant removes silicon from the wafer to a depth lying within the range of 700 to 1000A.
Claim 8
Dependent Claim
26 words
A process as recited in claim 4, in which said etching step is completed prior to any other processing step on the lapped and polished wafer.
Claim 9
Dependent Claim
25 words
A process as recited in claim 4, in which said etching step is completed prior to the growth of the gate oxide on the wafer.
Claim 10
Dependent Claim
26 words
A process as recited in claim 5 in which said etching step is repeated just prior to the growth of the gate oxide on the wafer.
Claim 11
Dependent Claim
62 words
In a process for use in the manufacture of shallow base junction bipolar devices the improvement comprising the step of: etching a lapped and polished wafer in which such bipolar devices are built in an etchant solution of a mixture of nitric acid and hydrofluoric acid having a ratio by volume of mixture lying within the range of 600:1 to 750:1, respectively.
Claim 12
Dependent Claim
62 words
In a process for use in the manufacture of shallow base junction bipolar devices the improvement comprising the step of: etching a lapped and polished wafer in which such bipolar devices are built in an etchant solution of a mixture of nitric acid and hydrofluoric acid having a ratio by volume of mixture lying within the range of 600:1 to 750:1, respectively.
Claim 13
Dependent Claim
26 words
A process as recited in claim 8, wherein the etchant removes silicon from the wafer to a depth lying within the range of 700A to 1000A.
Claim 14
Dependent Claim
25 words
A process as recited in claim 9, in which said etching step is completed prior to any other processing on the lapped and polished wafer.
Claim 15
Dependent Claim
20 words
A process as recited in claim 9, in which said etching step is completed just prior to the base diffusion.
Claim 16
Dependent Claim
20 words
A process as recited in claim 10, in which the etching step is repeated just prior to the base diffusion.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-01-30 | 1981-08-01 | 1982-01-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-01-30 | 1985-08-01 | 1986-01-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-01-30 | 1989-08-01 | 1990-01-31 | $7700.00 | Window Closed / Lapsed |