US6245213B1
Expired / Lapsed
US
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Method for anisotropic etching of structures in conducting materials
Assignee: Obducat AB
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Filing: 1999-03-05
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Granted: 2001-06-12
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Expires: 2019-03-05
Abstract
Abstract In a method for anisotropic etching of a structure in an electrically conductive substance to be etched, use is made of an etchant which in concentrated solution is usable for isotopic etching of structures in the substance to be etched. The substance to be etched is contacted with the etchant in a solution which is so diluted that the etchant is unusable for isotropic etching. The etchant is subjected, adjacent to the substance to be etched, to an electric field of such a strength that anisotropic etching of the substance to be etched is accomplished. Moreover, an etching fluid is described, comprising an etchant in dilute solution, in which the etchant is present in a concentration of 200 mM at most, and use of such an etching fluid for making structures which are 50 μm or less is also described.
Inventors
- 👤 Lennart Olsson
- 👤 Babak Heidari
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 15:53
CPC Classifications
C; C23; C23F; C23F1/00; C23F1/02; C25; C25F; C25F3/00; C25F3/02; H; H05; H05K; H05K3/00; H05K3/02; H05K3/06; H05K3/07
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
142 words
A method for anisotropic etching of a structure in an electrically conductive substance by means of an etchant which in a first solution at a first concentration and in the absence of an electric field will isotropically etch structures in the substance by spontaneous chemical reaction with the substance, said method comprising the steps of: contacting the substance with a second solution of the etchant which is diluted to a second concentration lower than said first concentration and which will isotropically etch structures in the substance by spontaneous chemical reaction with the substance in the absence of an electric field at a maximum etching rate of 5 nm/s; and subjecting the second solution adjacent to the area of the substance to be etched to an electric field of such a strength that anisotropic etching of said structure in the substance is accomplished.
Claim 2
Independent Claim
142 words
A method for anisotropic etching of a structure in an electrically conductive substance by means of an etchant which in a first solution at a first concentration and in the absence of an electric field will isotropically etch structures in the substance by spontaneous chemical reaction with the substance, said method comprising the steps of: contacting the substance with a second solution of the etchant which is diluted to a second concentration lower than said first concentration and which will isotropically etch structures in the substance by spontaneous chemical reaction with the substance in the absence of an electric field at a maximum etching rate of 5 nm/s; and subjecting the second solution adjacent to the area of the substance to be etched to an electric field of such a strength that anisotropic etching of said structure in the substance is accomplished.
Claim 3
Dependent Claim
23 words
The method as claimed in claim 1 , wherein the concentration of the etchant in the second solution is 200 mM at most.
Claim 4
Dependent Claim
28 words
The method as claimed in claim 1 , wherein the maximum isotropic etching rate of the second solution in the absence of an electric field is 3 nm/s.
Claim 5
Dependent Claim
42 words
The method as claimed in claim 1 , wherein the strength of the electric field is such that the rate of the anisotropic etching is at least two times greater than the isotropic etching rate in the absence of the electric field.
Claim 6
Dependent Claim
31 words
The method as claimed in claim 4 , wherein the anisotropic etching rate is at least ten times greater than the isotropic etching rate in the absence of an electric field.
Claim 7
Dependent Claim
23 words
The method as claimed in claim 2 , wherein the concentration of the etchant in the second solution is 100 mM at most.
Claim 8
Dependent Claim
23 words
The method as claimed in claim 6 , wherein the concentration of the etchant in the second solution is 50 mM at most.
Claim 9
Dependent Claim
22 words
The method as claimed in claim 7 , wherein the concentration of the etchant in the second solution is below 10 mM.
Claim 10
Dependent Claim
28 words
The method as claimed in claim 1 , wherein the etchant is an ionic substance that chemically reacts in an etching manner with the substance to be etched.
Claim 11
Dependent Claim
44 words
The method as claimed in claim 1 , wherein the step of subjecting the second solution to an electric field comprises contacting an electrode with the second solution and applying a voltage between the electrode and the area of the substance to be etched.
Claim 12
Dependent Claim
32 words
The method as claimed in claim 10 , wherein the electrode is arranged at a distance from a surface of the substance to be etched, the distance being 3 cm at most.
Claim 13
Dependent Claim
16 words
The method as claimed in claim 11 , wherein the distance is 1 cm at most.
Claim 14
Dependent Claim
16 words
The method as claimed in claim 12 , wherein the distance is 1 mm at most.
Claim 15
Dependent Claim
34 words
The method as claimed in claim 10 , wherein the applied voltage between the electrode and the area of the substance to be etched is at least 0.5 V and 10 V at most.
Claim 16
Dependent Claim
22 words
The method as claimed in claim 14 , wherein the applied voltage is at least 1 V and 5 V at most.
Claim 17
Dependent Claim
22 words
The method as claimed in claim 15 , wherein the applied voltage is at least 1.5 V and 3 V at most.
Claim 18
Dependent Claim
37 words
The method as claimed in claim 10 , wherein the electrode has a tapering portion directed toward the electrically conductive substance and arranged at a distance of 10 nm at most from the substance to be etched.
Claim 19
Dependent Claim
28 words
The method as claimed in claim 1 , wherein the anisotropic etching is carried out during a plurality of first periods, between which the electric field is changed.
Claim 20
Dependent Claim
24 words
The method as claimed in claim 18 , wherein the direction of the electric field, between said first periods, is reversed during second periods.
Claim 21
Dependent Claim
31 words
The method as claimed in claim 19 , wherein plating is accomplished during said second periods, and a portion of previously etched-away substance is returned to the substance to be etched.
Claim 22
Dependent Claim
31 words
The method as claimed in claim 19 , wherein, between said first periods, measurement of the etched depth is carried out during periods in which no electric field affects the circuit.
Claim 23
Dependent Claim
34 words
The method as claimed in claim 19 , wherein the duration of said first periods is as great as the time interval therebetween and is 200 ms at most and at least 10 ms.
Claim 24
Dependent Claim
25 words
The method as claimed in claim 22 , wherein the duration of said first periods is 100 ms at most and at least 50 ms.
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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) | 2004-06-11 | 2004-12-11 | 2005-06-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2008-06-11 | 2008-12-11 | 2009-06-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2012-06-11 | 2012-12-11 | 2013-06-12 | $7700.00 | Window Closed / Lapsed |