US5567304A
Expired / Lapsed
US
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Elimination of island formation and contact resistance problems during electroetching of blanket or patterned thin metallic layers on insulating substrate
Assignee: International Business Machines Corp
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Filing: 1995-01-03
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Granted: 1996-10-22
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Expires: 2015-01-03
Abstract
Abstract In through-mask electroetching of a metal film on top of an insulating substrate, the shape of the metal film being etched is a function of the mask opening, the spacing between the openings and the thickness of the mask. An analysis of the electric field around the mask and the metal film is used to determine conditions leading to the formation of islands of unetched metal films within the openings. The analysis is then used to design the mask pattern and eliminate these islands. The increase in the ratio of the mask thickness to the opening width for eliminating the islands also lowers the undercutting of the mask. Premature stoppage of the electroetching process arising from the isolation of the sample film from the contact is also addressed. The electrical contact to the sample is made at one end and a nozzle jet of electrolyte is slowly swept from the far end of the sample towards the electrical contact. The nozzle speed is matched with the metal removal rate and the electrical contact is exposed to the electrolyte at the end of the process.
Inventors
- 👤 Madhav Datta
- 👤 Lubomyr T. Romankiw
- 👤 Ravindra V. Shenoy
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 02:01
CPC Classifications
C; C25; C25F; C25F3/00; C25F3/02; C25F3/14; B; B23; B23H; B23H3/00; B23H9/00; B23H9/06; H; H05; H05K; H05K3/00; H05K3/02; H05K3/06; H05K3/07; H05K3/08
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
129 words
A method of electrochemically micromachining a metal film having a surface at least partially covered with an insulating mask having a plurality of openings, said method comprising the steps of: calculating a numerical relationship among a plurality of values including a, h, and L wherein the insulating mask has a thickness h and at least one of said plurality of openings has a width 2L and is spaced a distance 2a apart from another one of said plurality of openings wherein the numerical relationship among a, h, and L is calculated and h is varied to prevent island formation during electrochemical micromachining of the metal film: forming the insulating mask on the surface of the metal film according to the calculated numerical relationship; and electrochemically micromachining the metal film.
Claim 2
Independent Claim
129 words
A method of electrochemically micromachining a metal film having a surface at least partially covered with an insulating mask having a plurality of openings, said method comprising the steps of: calculating a numerical relationship among a plurality of values including a, h, and L wherein the insulating mask has a thickness h and at least one of said plurality of openings has a width 2L and is spaced a distance 2a apart from another one of said plurality of openings wherein the numerical relationship among a, h, and L is calculated and h is varied to prevent island formation during electrochemical micromachining of the metal film: forming the insulating mask on the surface of the metal film according to the calculated numerical relationship; and electrochemically micromachining the metal film.
Claim 3
Dependent Claim
41 words
A method of electrochemically micromachining a metal film according to claim 1, wherein said electrochemical micromachining is performed in an electrolyte and said numerical relationship is formulated by an analysis of at least one of voltage and current in said electrolyte.
Claim 4
Dependent Claim
32 words
A method of electrochemically micromachining a metal film according to claim 2, wherein said analysis of at least one of voltage and current in said electrolyte is performed using the Laplace equation.
Claim 5
Dependent Claim
100 words
A method of electrochemical micromachining a metal film according to claim 2, wherein said analysis of at least one of voltage and current in said electrolyte is performed using the boundary element method said method comprising the steps of: determining three of a plurality of variables including a, b, h, and L where the metal film has a thickness b; calculating another of a, b, h, and L according to a numerical relationship; forming the metal film and the insulating mask according to said respective determining and calculating of a, b, h, and L; and electrochemically micromachining the metal film.
Claim 6
Dependent Claim
119 words
A method of electrochemically micromachining a metal film according to claim 1, wherein said metal film is connected to a contact prior to electrochemical machining, and wherein said step of electrochemically micromachining the metal film comprises the steps of: providing an electrolyte; initiating impingement of said electrolyte onto said metal film at a point on said metal film away from said contact so as to etch said metal film; and continuing impingement of said electrolyte onto said metal film so as to continue etching said metal film from said point on said metal film away from said contact towards said contact in a single sweeping motion to prevent loss of electrical continuity between said contact and said metal film.
Claim 7
Dependent Claim
20 words
A method of electrochemically micromachining a metal film according to claim 5, wherein said electrolyte includes a neutral salt solution.
Claim 8
Independent Claim
129 words
A method of electrochemically micromachining a metal film having a surface at least partially covered with an insulating mask having a plurality of openings and said method comprising the steps of: calculating a numerical relationship along a plurality of values including, a, h and L wherein the insulating mask has a thickness h and at least one of said plurality of openings has a width 2L and is spaced a distance 2a apart from another one of said plurality of openings wherein the numerical relationship among a, h, and L is calculated and h is varied to at least partially prevent undercut of said metal film; forming the insulating mask on the surface of the metal film according to the calculated numerical relationship; and electrochemically micromachining the metal film.
Claim 9
Independent Claim
129 words
A method of electrochemically micromachining a metal film having a surface at least partially covered with an insulating mask having a plurality of openings and said method comprising the steps of: calculating a numerical relationship along a plurality of values including, a, h and L wherein the insulating mask has a thickness h and at least one of said plurality of openings has a width 2L and is spaced a distance 2a apart from another one of said plurality of openings wherein the numerical relationship among a, h, and L is calculated and h is varied to at least partially prevent undercut of said metal film; forming the insulating mask on the surface of the metal film according to the calculated numerical relationship; and electrochemically micromachining the metal film.
Claim 10
Dependent Claim
41 words
A method of electrochemically micromachining a metal film according to claim 7, wherein said electrochemical micromachining is performed in an electrolyte and said numerical relationship is formulated by an analysis of at least one of voltage and current in said electrolyte.
Claim 11
Dependent Claim
32 words
A method of electrochemically micromachining a metal film according to claim 8, wherein said analysis of at least one of voltage and current in said electrolyte is performed using the Laplace equation.
Claim 12
Dependent Claim
100 words
A method of electrochemical micromachining a metal film according to claim 8, wherein said analysis of at least one of voltage and current in said electrolyte is performed using the boundary element method, said method comprising the steps of: determining three of a plurality of variables including a, b, h and L where the metal film has a thickness b: calculating another of a, b, h, and L according to a numerical relationship; forming the metal film and tile insulating mask according to said respective determining and calculating of a, b, h, and L; and electrochemically micromachining the metal film.
Claim 13
Independent Claim
156 words
A method of electrochemically micromachining a metal film having a surface at least partially covered with an insulating mask having a plurality of openings, said method comprising the steps of: determining three of a plurality of variables including a, b, h, and L where the metal film has a thickness b, the insulating mask has a thickness h and at least one of said plurality of openings has a width 2L and is spaced a distance 2a apart from another one of said plurality of openings; calculating another of a, b, h, and L according to a numerical relationship; forming the metal film and the insulating mask according to said respective determining and calculating of a, b, h, and L; and electrochemically micromachining the metal film, wherein said another of a, b, h, and L is calculated and one of b and h is varied to prevent island formation during electrochemical micromachining of the metal film.
Claim 14
Independent Claim
156 words
A method of electrochemically micromachining a metal film having a surface at least partially covered with an insulating mask having a plurality of openings, said method comprising the steps of: determining three of a plurality of variables including a, b, h, and L where the metal film has a thickness b, the insulating mask has a thickness h and at least one of said plurality of openings has a width 2L and is spaced a distance 2a apart from another one of said plurality of openings; calculating another of a, b, h, and L according to a numerical relationship; forming the metal film and the insulating mask according to said respective determining and calculating of a, b, h, and L; and electrochemically micromachining the metal film, wherein said another of a, b, h, and L is calculated and one of b and h is varied to prevent island formation during electrochemical micromachining of the metal film.
Claim 15
Dependent Claim
41 words
A method of electrochemically micromachining a metal film according to claim 11, wherein said electrochemical micromachining is performed in an electrolyte and said numerical relationship is formulated by an analysis of at least one of voltage and current in said electrolyte.
Claim 16
Dependent Claim
32 words
A method of electrochemically micromachining a metal film according to claim 12, wherein said analysis of at least one of voltage and current in said electrolyte is performed using the Laplace equation.
Claim 17
Dependent Claim
33 words
A method of electrochemical micromachining a metal film according to claim 12, wherein said analysis of at least one of voltage and current in said electrolyte is performed using the boundary element method.
Claim 18
Dependent Claim
41 words
A method of electrochemical micromachining a metal film according to claim 11, wherein another of a, b, h and L is graphically derived to prevent island formation during electrochemical micromachining of the metal film by correlating a, b, h and L.
Claim 19
Dependent Claim
34 words
A method of electrochemical micromachining a metal film according to claim 11, wherein another of a, b, h and L is numerically calculated to prevent island formation during electrochemical micromachining of the metal film.
Claim 20
Dependent Claim
119 words
A method of electrochemically micromachining a metal film according to claim 11, wherein said metal film is connected to a contact prior to electrochemical machining, and wherein said step of electrochemically micromachining the metal film comprises the steps of: providing an electrolyte; initiating impingement of said electrolyte onto said metal film at a point on said metal film away from said contact so as to etch said metal film; and continuing impingement of said electrolyte onto said metal film so as to continue etching said metal film from said point on said metal film away from said contact towards said contact in a single sweeping motion to prevent loss of electrical continuity between said contact and said metal film.
Claim 21
Dependent Claim
20 words
A method of electrochemically micromachining a metal film according to claim 17, wherein said electrolyte includes a neutral salt solution.
Claim 22
Independent Claim
152 words
A method of electrochemically micromachining a metal film having a surface at least partially covered with an insulating mask having a plurality of openings, said method comprising the steps of: determining three of a plurality of variables including a, b, h, and L where the metal film has a thickness b, the insulating mask has a thickness h and at least one of said plurality of openings has a width 2L and is spaced a distance 2a apart from another one of said plurality of openings; calculating another of a, b, h, and L according to a numerical relationship; wherein said another of a, b, h and L is calculated and one of b and h is varied to prevent undercut of said metal film; forming the metal film and the insulating mask according to said respective determining and calculating of a, b, h, and L; and electrochemically macromachining the metal film.
Claim 23
Independent Claim
152 words
A method of electrochemically micromachining a metal film having a surface at least partially covered with an insulating mask having a plurality of openings, said method comprising the steps of: determining three of a plurality of variables including a, b, h, and L where the metal film has a thickness b, the insulating mask has a thickness h and at least one of said plurality of openings has a width 2L and is spaced a distance 2a apart from another one of said plurality of openings; calculating another of a, b, h, and L according to a numerical relationship; wherein said another of a, b, h and L is calculated and one of b and h is varied to prevent undercut of said metal film; forming the metal film and the insulating mask according to said respective determining and calculating of a, b, h, and L; and electrochemically macromachining the metal film.
Claim 24
Dependent Claim
40 words
A method of electrochemically micromachining metal film according to claim 19, wherein said electrochemical micromachining is performed in an electrolyte and said numerical relationship is formulated by an analysis of at least one of voltage and current in said electrolyte.
Claim 25
Dependent Claim
32 words
A method of electrochemically micromachining a metal film according to claim 20, wherein said analysis of at least one of voltage and current in said electrolyte is performed using the Laplace equation.
Claim 26
Dependent Claim
33 words
A method of electrochemical micromachining a metal film according to claim 20, wherein said analysis of at least one of voltage and current in said electrolyte is performed using the boundary element method.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1999-10-22 | 2000-04-22 | 2000-10-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-10-22 | 2004-04-22 | 2004-10-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-10-22 | 2008-04-22 | 2008-10-22 | $7700.00 | Window Closed / Lapsed |