Patent US3847776A successfully refreshed from Google Patents.
US3847776A
Expired / Lapsed
US
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Method of preparing a pattern of a layer of refractory metal by masking
Assignee: Cegelec SA
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Filing: 1972-03-01
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Granted: 1974-11-12
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Expires: 1992-03-01
Abstract
Abstract A layer of refractory metal for example of tungsten or molybdenum, and about one micron thick is prepared in accordance with a predetermined pattern by masking by applying the refractory metal on a substrate which may be conductive or is close to a conductor; the refractory metal is covered by a protective layer, in the mask pattern. The protective layer may, in turn, have been covered with a photoresist and have been partly etched away. The masked, continuous layer of refractory metal is exposed to an electro-erosive environment which selectively attacks only the refractory metal but does not attack the protective masking layer, and the exposed refractory metal layer is removed; the masking layer is then dissolved in a substance which is inert with respect to the refractory metal. The refractory metal may be removed by placing the metal in an ionized gaseous medium or by electrolytic compositions. A suitable protective layer is silicon nitride.
Inventors
- 👤 P Coppier
- 👤 B Bourdon
- 👤 C Duong
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 17:16
CPC Classifications
H; H10; H10P; H10P95/00; C; C23; C23F; C23F4/00; H10P50/00; H10P50/20; H10W; H10W74/00; H10W74/40
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
89 words
A METHOD OF PREPARING A PATTERN OF A LAYER OF REFRACTORY METAL ON A SUBSTRATE BY MASKING, COMPRISING: APPLYING THE REFRATORY METAL ON THE SUBSTRATE AS A CONTINUOUS LAYER; COVERING THE CONTINUOUS LAYER OF REFRACTORY MATERIAL WITH A CONTINUOUS PROTECTIVE LAYER OF A MATERIAL SUBSTANTIALLY MORE RESISTANT TO ION BOMBARDMENT THAN SAID REFRACTORY METAL; PHOTOLITHOGRAPHICALLY APPLYING A MASK ON SAID PROTECTIVE LAYER CORRESPONDING TO SAID PATTERN; CHEMICALLY ETCHING SAID PROTECTIVE LAYER WITH AN ETCHANT TO WHICH SAID REFRACTORY METAL IS RESISTANT, TO EXPOSE SAID REFRACTORY METAL IN SELECTED AREAS;
Claim 2
Independent Claim
89 words
A METHOD OF PREPARING A PATTERN OF A LAYER OF REFRACTORY METAL ON A SUBSTRATE BY MASKING, COMPRISING: APPLYING THE REFRATORY METAL ON THE SUBSTRATE AS A CONTINUOUS LAYER; COVERING THE CONTINUOUS LAYER OF REFRACTORY MATERIAL WITH A CONTINUOUS PROTECTIVE LAYER OF A MATERIAL SUBSTANTIALLY MORE RESISTANT TO ION BOMBARDMENT THAN SAID REFRACTORY METAL; PHOTOLITHOGRAPHICALLY APPLYING A MASK ON SAID PROTECTIVE LAYER CORRESPONDING TO SAID PATTERN; CHEMICALLY ETCHING SAID PROTECTIVE LAYER WITH AN ETCHANT TO WHICH SAID REFRACTORY METAL IS RESISTANT, TO EXPOSE SAID REFRACTORY METAL IN SELECTED AREAS;
Claim 3
Dependent Claim
58 words
A method according to claim 1 in which said gaseous medium is ionized by an applied electric field in which said substrate is at relative electro-negative potential, and in which said electric field is of sufficient strength to produce enough secondary emission from the refractory metal to maintain the ionization of the gas during the ion bombardment step.
Claim 4
Dependent Claim
78 words
A method according to claim 1 in which said gaseous medium is ionized by electron emission from an electron emissive cathode electronegatively polarized relative to an electron collecting anode, said gaseous medium, cathode and anode being in a space sufficiently evacuated for such electron emission and gas ionization, and in which, further, said refractory metal is negatively polarized by means of a controllable d.c. voltage source providing a voltage between the refractory metal and said electron emissive cathode.
Claim 5
Dependent Claim
41 words
A method according to claim 1 in which said gaseous medium is ionized by an ultraviolet light source and is subjected to an electric field with respect to which said refractory metal is electronegatively polarized, so as to attract positive ions.
Claim 6
Dependent Claim
41 words
A method according to claim 1 in which said gaseous medium is ionized by a radioactive radiation source and is subjected to an electric field with respect to which said refractory metal is electronegatively polarized, so as to attract positive ions.
Claim 7
Dependent Claim
20 words
Method according to claim 1, wherein the refractory metal is tungsten or molybdenum, and the protective layer is silicon nitride.
Claim 8
Dependent Claim
24 words
Method according to claim 1, wherein the protective layer is an insulating material selected from the group consisting of insulating oxides and insulating nitrides.
Claim 9
Dependent Claim
21 words
Method according to claim 1, wherein the step of removal of the refractory metal in the non-protected locations includes electrolytic attack.
Claim 10
Dependent Claim
15 words
Method according to claim 1, wherein the gaseous medium comprises at least one noble gas.
Claim 11
Dependent Claim
23 words
Method according to claim 1, wherein the gaseous medium comprises a mixture of gases of which at least one is a noble gas.
Claim 12
Dependent Claim
56 words
Method according to claim 1, wherein the step of removing the refractory metal comprises locating the substrate, the metal thereon and the protective layer in an electrically conductive environment and applying a voltage to the metal with respect to the environment of such polarity as to provide for removal of said metal due to said voltage.
Claim 13
Dependent Claim
35 words
Method according to claim 11, wherein the protective layer is an insulator and its thickness is just enough to insulate, without breakdown, the refractory metal therebeneath with respect to said voltage against the conductive environment.
Claim 14
Dependent Claim
12 words
Method according to claim 1, wherein the substrate is a semiconductor body.
Claim 15
Dependent Claim
19 words
Method according to claim 1, wherein the refractory metal layer has a thickness in the order of 1 micron.
Claim 16
Dependent Claim
19 words
Method according to claim 1, wherein the protective layer is an insulator of a thickness of about 1,000 A.
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) | 1977-11-11 | 1978-05-13 | 1978-11-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-11-11 | 1982-05-13 | 1982-11-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-11-11 | 1986-05-13 | 1986-11-12 | $7700.00 | Window Closed / Lapsed |