Anisotropic liquid phase photochemical etch

• US 5,460,687 A
• Filed: 05/20/1994
• Issued: 10/24/1995
• Est. Priority Date: 10/30/1992
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Douglas, Monte A.
• Primary Examiner(s): Breneman, R. Bruce
• Assistant Examiner(s): CHANG, JONI YUK YING
• Application Number:
  US08/246,388
• Time in Patent Office: 522 Days
• Field of Search: 156/635, 156/643, 156/656, 156/659.1, 156/666, 156/901, 156/902
• US Class Current: 216/48
• CPC Class Codes: C23F 1/02 Local etching
• CPC Class Codes: H01L 21/30655 comprising alternated and repeated etching and passivation steps, e.g. Bosch process
• CPC Class Codes: H01L 21/32134 by liquid etching only

Abstract

An anisotropic liquid phase photochemical etch is performed by submersing a substrate 30 (e.g. copper) in a liquid 34 containing an etchant (e.g. hydrochloric acid) and a passivant (e.g. iodine), the passivant forming an insoluble passivation layer 36 (e.g. Cul) on the surface, preventing the etchant from etching the surface. The passivant and its concentration are chosen such that the passivation layer 36 has a solubility which is substantially increased when it is illuminated with radiation 38 (e.g. visible/ultraviolet light). Portions of the surface are then illuminated with radiation 38, whereby the passivation layer 36 is removed from those illuminated portions of the surface, allowing the etch to proceed there. Portions of the surface not illuminated are not etched, resulting in an anisotropic etch. Preferably, an etch mask 32 is used to create the unilluminated areas. This etch mask 32 may be formed on the surface or it may be interposed between the surface and the radiation source.

Claims

1. An anisotropic etch method comprising:

(a) supplying a substrate having an etch mask in contact with a surface of said substrate, said surface having one or more exposed areas not covered by said etch mask;

(b) submersing said substrate in a liquid, said liquid including at least one etchant and one passivant, said etchant capable of etching said surface, said passivant forming a passivation layer on said surface, said passivation layer being substantially insoluble in said liquid; and

(c) illuminating said substrate with radiation to produce illuminated areas and unilluminated areas on said substrate, said radiation removing said passivation layer from said illuminated areas, causing said illuminated areas to be etched while said unilluminated areas remain substantially unetched;

whereby an anisotropic etch of said surface in said exposed areas is achieved.

2. The method according to claim 1, wherein said passivant is added to said liquid before said submersing step.

3. The method according to claim 1, wherein said etch is accelerated by said radiation.

4. The method according to claim 1, wherein said liquid flows with respect to said substrate.

5. The method of claim 1, wherein the intensity of said radiation varies in time.

6. The method of claim 1, wherein the intensity of said radiation varies across said surface.

7. The method of claim 1, wherein said liquid is maintained at approximately 25 C. during said etch.

8. The method of claim 1, wherein said radiation is monochromatic.

9. The method of claim 1, wherein said liquid contains two or more passivants.

10. The method of claim 1, wherein said liquid contains two or more etchants.

11. The method of claim 1, wherein said liquid comprises H₂ O and at least one passivant.

12. The method of claim 1, wherein said etch mask is formed of patterned photoresist.

13. An anisotropic etch method comprising:

(a) supplying a substrate having an etch mask in contact with a surface said substrate, said surface having one or more exposed areas not covered by said etch mask;

(b) submersing said substrate in an aqueous solution, said aqueous solution including at least one passivant, said aqueous solution capable of etching said surface, said passivant forming a passivation layer on said surface, said passivation layer being substantially insoluble in said aqueous solution; and

(c) illuminating said substrate with radiation to produce illuminated areas and unilluminated areas on said substrate, said radiation removing said passivation layer from said illuminated areas, causing said illuminated areas to be etched while said unilluminated areas remain substantially unetched;

whereby an anisotropic etch of said surface in said exposed areas is achieved.