METHOD FOR PRODUCING A THIN FILM PASSIVE CIRCUIT ELEMENT

• US 3,862,017 A
• Filed: 04/24/1973
• Issued: 01/21/1975
• Est. Priority Date: 02/04/1970
• Status: Expired due to Term

• Current Assignee: Hideo Tsunemitsu, Hiroshi Shiba
• Original Assignee: Hideo Tsunemitsu, Hiroshi Shiba
• Inventors: Shiba, Hiroshi, Tsunemitsu, Hideo
• Primary Examiner(s): Tufariello, T. M.
• Application Number:
  US05/353,959
• Time in Patent Office: 637 Days
• Field of Search: 204/15 29/625-628,576 317/234R 117/212
• US Class Current: 205/124
• CPC Class Codes: C25D 11/26 of refractory metals or alloys based thereon
• CPC Class Codes: H01C 17/02 adapted for manufacturing resistors with envelope or housing
• CPC Class Codes: H01C 17/262 by electrolytic treatment, e.g. anodic oxydation
• CPC Class Codes: H01L 21/707 of thin-film circuits or parts thereof
• CPC Class Codes: Y10T 428/24917 including metal layer

Abstract

A thin film of a high resistivity metal such as Ta, Ti, Mo or Nb is formed on a substrate. The side faces of the thin resistive film are surrounded by, and at least a greater part of the top surface of the thin resistive film is covered with an insulating substance which is a compound, such as an oxide or nitride of the high resistivity metal. The thin resistive film and the insulating substance form a substantially flat layer.

Claims

1. A METHOD OF PRODUCING A THIN FILM RESISTOR ELEMENT COMPRISING THE STEPS OF PREPARING A SUBSTRATE IN WHICH AT LEAST TWO CONDUCTIVE WIRING PATHS ARE EMBEDDED, SAID SUBSTRATE HAVING AN INSULATING SURFACE TO RESPECTIVELY EXPOSE A PORTION OF IN SAID INSULATING SURFACE TO RESPECTIVELY EXPOSE A PORTION OF THE SURFACE OF EACH OF SAID TWO CONDUCTIVE WIRING PATHS;

DEPOSITING A METALLIC FILM HAVING A SUBSTANTIALLY UNIFORM THICKNESS OVER THE SURFACE OF SAID SUBSTRATE AND SAID EXPOSE PORTIONS, SAID METALLIC FILM BEING OF A METAL OF HIGH RESISTIVTY SELECTED FROM THE GROUP CONSISTING OF TANTALUM, TITANIUM, MOLYBDENUM, AND NIOBIUM, ANODICALLY OXIDIZING SAID METALLIC FILM TO CONVERT THE SURFACE OF SAID METALLIC FILM INTO THE OXIDE OF SAID METAL;

AND THEREAFTER ANODICALLY OXIDIZING A PREDETERMINED PORTION OF SAID METALLIC FILM TO CONVERT THE REMAINING THICKNESS OF SAID METALLIC FILM INTO THE OXIDE OF SAID METAL EXCEPT FOR A PREDETERMINED RESISTOR PORTION IN CONTACT WITH THE PREVIOUSLY EXPOSED PORTIONS OF THE SURFACE OF SAID TWO CONDUCTIVE WIRING PATHS.

2. The method claimed in claim 1, in which said metallic film is of tantalum.

3. The method claimed in claim 2, in which said conductive wiring paths are of aluminum.

4. A method of producing a thin film resistor element comprising the steps of preparing a substrate having first and second embedded conductive wiring paths and an insulating surface;

opening first and second apertures in said surface of said insulating surface to partially expose the surface of said first and second embedded conductive wiring paths, respectively;

depositing a film of anodizable material of high resistivity having a substantially uniform thickness over the surface of said substrate, first and second portions of said film extending to and being in contact with said first and second embedded conductive wiring paths through said first and second apertures, respectively; and

converting by anodic oxidation a predetermined portion of said film into the oxide of said anodizable material to provide a resistor portion electrically connected between said first and second portions of said film and enclosed by the oxide of said anodizable material.

5. The method claimed in claim 4, in which said converting step includes anodically oxidizing the surface of said film, and thereafter selectively anodically oxidizing the remaining thickness of said film.

6. The method claimed in claim 4, in which said converting step includes anodically oxidizing the surface portion of said film, anodically oxidizing a selected portion of said film to a predetermined depth of said film, and thereafter anodically oxidizing another selected portion of said film to the bottom of said film.

7. The method claimed in claim 4, in which said anodizable material is tantalum.

8. A method of producing a semiconductor device having a thin film resistor element comprising the steps of preparing a semiconductor substrate having circuit elements formed therein, the surface of said semiconductor substrate being coated with an insulating film having apertures to allow electrical connection to said circuit elements;

depositing an aluminum film on the surface of said insulating film;

anodically oxidizing a selected portion of said aluminum film to provide aluminum wiring paths;

depositing a tantalum film on the selectively anodically oxidized aluminum film; and

thereafter anodically oxidizing a selected portion of said tantalum film to provide a tantalum resistor element connected between selected ones of said circuit elements.