Controlled potential anodic etching process for the selective removal of conductive thin films

• US 6,737,360 B2
• Filed: 12/30/1999
• Issued: 05/18/2004
• Est. Priority Date: 12/30/1999
• Status: Expired due to Term

• Current Assignee: Beijing Xiaomi Mobile Software Co., Ltd. (Xiaomi Corp.)
• Original Assignee: Intel Corporation
• Inventors: Lee, Kevin J.
• Primary Examiner(s): CHEN, KIN CHAN
• Application Number:
  US09/475,492
• Publication Number:
  US 20020119671A1
• Time in Patent Office: 1,601 Days
• Field of Search: 438/689, 438/745, 438/747, 438/748, 438/754
• US Class Current: 438/745
• CPC Class Codes: C25F 3/14 locally
• CPC Class Codes: H01L 21/32134 by liquid etching only

Abstract

A process for selectively removing a conductive layer from a wafer that includes sub-micron sized noble metal interconnect features is disclosed. The wafer having sub-micron sized noble metal interconnect features and a conductive film to be removed is placed into an electrolyte solution. Also immersed in the electrolyte solution are a counter electrode, a reference electrode, and a working electrode. The wafer is coupled to the working electrode terminal on a potentiostat. The counter electrode is connected to the counter electrode terminal on a potentiostat, and the reference electrode is connected to a reference electrode terminal on the potentiostat. The potentiostat adjusts the electrical current flowing between the wafer and the counter electrode to maintain a constant voltage between the wafer and the reference electrode as the conductive layer is removed. The removal of the conductive layer is finished when the current that maintains the constant voltage between the wafer and the reference electrode drops to a residual level.

Claims

1. A process to selectively remove a conductive layer from a substrate, the process comprising:

depositing a conductive layer, a first noble metal layer and a barrier layer on a substrate;

placing the substrate in an HCL solution after said depositing, the substrate having sub-micron interconnect features, said sub-micron interconnect features including the first noble metal layer coupled to the conductive layer, the conductive layer of the substrate coupled to a working electrode terminal of a potentiostat;

maintaining a voltage between the substrate and a reference electrode at a fixed value by varying a first current between the substrate and a counter electrode while the substrate remains in the volatile electrolyte solution and the amount of conductive layer is reduced; and

breaking a path of the current when the current reaches a second current value substantially lower than a first current value,

wherein the first noble metal layer remains deposited on the substrate as the conductive layer is selectively removed from the barrier layer of the substrate.

2. The process of claim 1, wherein maintaining a voltage includes measuring a potential difference between the substrate and the reference electrode.

3. The process of claim 1, wherein the conductive layer of the substrate is etched on a conductive barrier layer surface of the substrate.

4. The process of claim 3, wherein the barrier layer includes titanium nitride.

5. The process of claim 1, wherein the conductive layer includes nickel.

6. The process of claim 1, wherein the sub-micron interconnect features includes a noble metal.

7. The process of claim 6, wherein the noble metal includes copper.

8. A process to selectively remove a conductive layer from a substrate, the process comprising:

depositing a conductive layer, a first noble metal layer and a barrier layer on a substrate;

placing said substrate in an HCl solution after said depositing, the substrate having sub-micron size metal interconnect features, said sub-micron size metal interconnect features including the first noble metal layer coupled to the conductive layer, the conductive layer of the substrate coupled to a working electrode terminal of a potentiostat;

maintaining a voltage between the substrate and a reference electrode at a fixed value, as the conductive layer is removed, by varying a current between said substrate and a counter electrode while the substrate remains in the HCl electrolyte solution and the amount of conductive layer is reduced; and

breaking a path of said current when a second current value reached is substantially lower than a first current value,

wherein the first noble metal layer remains substantially unaffected on the substrate as the conductive layer is selectively removed from the barrier layer of the substrate.