Method of electrochemically fabricating multilayer structures having improved interlayer adhesion

• US 20050029109A1
• Filed: 05/07/2004
• Published: 02/10/2005
• Est. Priority Date: 05/07/2002
• Status: Abandoned Application

• Current Assignee: University of Southern California
• Original Assignee: University of Southern California
• Inventors: Zhang, Gang, Cohen, Adam L.
• Application Number:
  US10/841,384
• Publication Number:
  US 20050029109A1
• Time in Patent Office: Days
• US Class Current: 205/118
• CPC Class Codes: C25D 1/003 3D structures, e.g. superposed patterned layers
• CPC Class Codes: C25D 5/022 using masking means
• CPC Class Codes: C25D 5/10 Electroplating with more than one layer of the same or of different metals for bearings C25D7/10
• CPC Class Codes: C25D 5/12 at least one layer being of nickel or chromium
• CPC Class Codes: C25D 5/14 two or more layers being of nickel or chromium, e.g. duplex or triplex layers
• CPC Class Codes: C25D 5/34 Pretreatment of metallic surfaces to be electroplated
• CPC Class Codes: C25D 5/40 Nickel; Chromium
• CPC Class Codes: C25D 5/48 After-treatment of electroplated surfaces
• CPC Class Codes: C25D 5/50 by heat-treatment
• CPC Class Codes: H01L 21/2885 using an external electrical current, i.e. electro-deposition
• CPC Class Codes: H01L 21/76879 by selective deposition of conductive material in the vias, e.g. selective C.V.D. on semiconductor material, plating plating on semiconductors in general H01L21/288
• CPC Class Codes: H05K 3/241 characterised by the electroplating method; means therefor, e.g. baths or apparatus
• CPC Class Codes: H05K 3/243 characterised by selective plating, e.g. for finish plating of pads selective plating for making the circuit pattern H05K3/108, H05K3/182

Abstract

Multi-layer microscale or mesoscale structures are fabricated with adhered layers (e.g. layers that are bonded together upon deposition of successive layers to previous layers) and are then subjected to a heat treatment operation that enhances the interlayer adhesion significantly. The heat treatment operation is believed to result in diffusion of material across the layer boundaries and associated enhancement in adhesion (i.e. diffusion bonding). Interlayer adhesion and maybe intra-layer cohesion may be enhanced by heat treating in the presence of a reducing atmosphere that may help remove weaker oxides from surfaces or even from internal portions of layers.

Claims

1. A fabrication process for forming a multi-layer three-dimensional structure, comprising:

(a) forming and adhering a layer of material to a previously formed layer and/or to a substrate, wherein the layer comprises a desired pattern of at least one material; and

(b) repeating the forming and adhering operation of (a) at least twice to build up a three-dimensional structure from a plurality of adhered layers, wherein the desired patterning on at least two layers is different;

(c) after formation of at least a plurality of layers, subjecting the multi-layer structure to a heat treatment;

wherein the structure comprises at least one metal, and wherein the forming and adhering of at least one layer comprises use of a conformable contact mask in the selective patterning of at least one material.

2. The process of claim 1 wherein the forming and adhering for at least two layers comprises electrodepositing the at least one metal.

3. The process of claim 2 wherein the heat treatment results in improvement of adhesion strength between metal deposits.

4. The process of claim 1 wherein the electrodepositing comprises electroplating the at least one metal.

5. The process of claim 4 wherein the heat treatment results in improvement of adhesion strength between metal deposits.

6. The process of claim 2 wherein the at least one metal comprises nickel.

7. The process of claim 1 wherein each of a plurality of layers comprises at least two metals, wherein at least one of the metals is a sacrificial material and at least one other metal is a structural material that forms at least part of the structure.

8. The process of claim 7 wherein the sacrificial material comprises copper.

9. The process of claim 7 wherein the structural material comprises nickel.

10. The process of claim 3 wherein the adhesion strength increases by at least a factor of about two.

11. The process of claim 10 wherein the adhesion strength increases by at least a factor of about five.

12. The process of claim 1 wherein the formation of a layer additionally comprises the planarization of deposited material.

13. A process for forming a multi-layer three-dimensional structure, comprising:

(a) forming a patterned deposit of at least one first material on to a substrate or previously deposited material such that at least one void exists around or within the patterned deposit of the at least first material;

(b) depositing at least one second material into at least a portion of the at least one void;

(c) trimming the deposit of the at least one first material or the at least one second material to a desired level;

(d) repeating the forming and adhering operations of (a)-(c) a plurality of times to build up a three-dimensional structure from a plurality of adhered layers;

(e) after formation of at least a plurality of layers, subjecting the multi-layer structure to heat treatment,

wherein at least one deposited material comprises a metal, and wherein the forming and adhering of at least one layer comprises use of a conformable contact mask in the selective patterning of at least one material.

14. The process of claim 13 wherein the heat treatment results in an increase in the adhesion between at least a portion of the overlaying depositions of at least one of the first and/or at least one of the second deposited materials.

15. The process of claim 14 wherein the enhanced adhesion results, at least in part, from heat-aided diffusion of material across a boundary joining two deposits.

16. A fabrication process for forming a multi-layer three-dimensional structure, comprising:

(a) forming and adhering a layer to a previously formed layer and/or to a substrate; and

(b) repeating the forming and adhering operation of (a) at least once to build up a three-dimensional structure from a plurality of adhered layers, wherein at least a plurality of the layers each comprise at least two deposited materials;

(c) after formation of at least a plurality of layers, subjecting the multi-layer structure to a heat treatment;

wherein the structure comprises at least one metal, and wherein the forming and adhering of at least one layer comprises use of a conformable contact mask in the selective patterning of at least one material.

17. A fabrication process for forming a multi-layer three-dimensional structure, comprising:

(a) forming and adhering a layer to a previously formed layer and/or to a substrate; and

(b) repeating the forming and adhering operation of (a) at least once to build up a three-dimensional structure from a plurality of adhered layers, wherein the forming of at least a plurality of layers comprises removing at least some deposited material in a planarization operation;

(c) after formation of at least a plurality of layers, subjecting the multi-layer structure to a heat treatment;

wherein the structure comprises at least one metal, and wherein the forming and adhering of at least one layer comprises use of a conformable contact mask in the selective patterning of at least one material.

18. A fabrication process for forming a multi-layer three-dimensional structure, comprising:

(a) forming and adhering a layer to a previously formed layer and/or to a substrate, wherein the layer comprises a desired pattern of at least one material; and

(b) repeating the forming and adhering operation of (a) at least once to build up a three-dimensional structure from a plurality of adhered layers, wherein the desired patterning of at least one material deposited on a subsequent layer adheres directly to the desired patterning of at least one material deposited on a preceding layer;

(c) after formation of at least a plurality of layers, subjecting the multi-layer structure to a heat treatment;

wherein the structure comprises at least one metal, and wherein the forming and adhering of at least one layer comprises use of a conformable contact mask in the selective patterning of at least one material.

19. A fabrication process for forming a multi-layer three-dimensional structure, comprising:

(a) forming and adhering a layer to a previously formed layer and/or to a substrate, wherein the layer comprises a desired pattern of at least one material; and

(b) repeating the forming and adhering operation of (a) at least once to build up a three-dimensional structure from a plurality of adhered layers;

(c) after formation of at least a plurality of layers, subjecting the multi-layer structure to a heat treatment, wherein the structure is heated in a manner such that any local temperature variations within the structure do not directly result from localized differences in electrical conductivity of the structural material;

wherein the structure comprises at least one metal, and wherein the forming and adhering of at least one layer comprises use of a conformable contact mask in the selective patterning of at least one material.

20. A fabrication process for forming a multi-layer three-dimensional structure, comprising:

(a) forming and adhering a layer to a previously formed layer and/or to a substrate, wherein the layer comprises a desired pattern of at least one material; and

(b) repeating the forming and adhering operation of (a) at least once to build up a three-dimensional structure from a plurality of adhered layers;

(c) after formation of at least a plurality of layers, subjecting the multi-layer structure to a heat treatment, wherein a maximum temperature during heat treatment is less than a recrystallization temperature of at least one metal forming part of the structure,

wherein the forming and adhering of at least one layer comprises use of a conformable contact mask in the selective patterning of at least one material.

21. A fabrication process for forming a multi-layer three-dimensional structure, comprising:

(a) forming and adhering a layer of material to a previously formed layer and/or to a substrate, wherein the layer comprises a desired pattern of at least one material; and

(b) repeating the forming and adhering operation of (a) at least twice to build up a three-dimensional structure from a plurality of adhered layers;

(c) after formation of at least a plurality of layers, subjecting the multi-layer structure to a heat treatment; and

(d) releasing the structure from the substrate,

wherein the structure comprises at least one metal, and wherein the forming and adhering of at least one layer comprises use of a conformable contact mask in the selective patterning of at least one material.

22. A fabrication process for forming a multi-layer three-dimensional structure, comprising:

(a) forming and adhering a layer to a previously formed layer and/or to a substrate, wherein the layer comprises a desired pattern of at least one material; and

(b) repeating the forming and adhering operation of (a) at least once to build up a three-dimensional structure from a plurality of adhered layers;

(c) after formation of at least a plurality of layers, subjecting the multi-layer structure to a heat treatment, wherein a maximum effective temperature during heat treatment is less than a recrystallization temperature of at least one metal forming part of the structure, and wherein the heat treatment is applied for a sufficient time and at a sufficient temperature and in an environment that allows interlayer adhesion to be enhanced a substantial amount,

wherein the structure comprises at least one metal, and wherein the forming and adhering of at least one layer comprises use of a conformable contact mask in the selective patterning of at least one material.

23. The process of claim 22 wherein the substantial amount comprises at least a factor of two.

24. The process of claim 22 wherein the substantial amount comprises at least a factor of five.