Methods of forming three-dimensional structures having reduced stress and/or curvature

• US 9,540,233 B2
• Filed: 02/28/2014
• Issued: 01/10/2017
• Est. Priority Date: 05/07/2002
• Status: Expired due to Term

• Current Assignee: Microfabrica Incorporated (Technoprobe S.P.A.)
• Original Assignee: Microfabrica Incorporated (Technoprobe S.P.A.)
• Inventors: Albarran, Jorge S., Kumar, Ananda H., Cohen, Adam L., Kim, Kieun, Lockard, Michael S., Frodis, Uri, Smalley, Dennis R.
• Primary Examiner(s): ZHAO, XIAO SI
• Application Number:
  US14/194,564
• Publication Number:
  US 20140238865A1
• Time in Patent Office: 1,047 Days
• Field of Search: 205/135
• US Class Current: 1/1
• CPC Class Codes: B81C 1/00666 Treatments for controlling internal stress or strain in MEMS structures
• CPC Class Codes: C25D 5/022 using masking means

Abstract

Electrochemical fabrication processes and apparatus for producing single layer or multi-layer structures where each layer includes the deposition of at least two materials and wherein the formation of at least some layers includes operations for reducing stress and/or curvature distortion when the structure is released from a sacrificial material which surrounded it during formation and possibly when released from a substrate on which it was formed. Six primary groups of embodiments are presented which are divide into eleven primary embodiments. Some embodiments attempt to remove stress to minimize distortion while others attempt to balance stress to minimize distortion.

Claims

1. In a method of forming a multi-layer three-dimensional structure, comprising:

(A) forming a plurality of successive layers of the structure with each successive layer adhered to a previously formed layer and with each successive layer comprising at least two materials, one of which is a structural material and the other of which is a sacrificial material, and wherein each successive layer defines a successive cross-section of the three-dimensional structure, and wherein the forming of each of the plurality of successive layers comprises;

(i) depositing a first of the at least two materials;

(ii) depositing a second of the at least two materials; and

(B) after the forming of the plurality of successive layers, separating at least a portion of the sacrificial material from the structural material to reveal the three-dimensional structure, wherein the improvement comprises;

in association with the formation of a given one of the successive layers, depositing a primary structural material in a lateral region of the given one of the successive layers to form at least a majority of the given one of the successive layers in the lateral region, and thereafter planarizing the primary structural material to form a surface of the given one of the successive layers, and thereafter sequentially exposing portions of the surface to selected laser radiation which results in less distortion of the lateral region after the separating than would exist in absence of the exposing.

2. The method of claim 1 wherein operations applied to the given one of the successive layers is applied to the formation of a plurality of the successive layers.

3. The method of claim 1 wherein the laser radiation provides annealing of the material that is exposed to the laser radiation.

4. The method of claim 3 wherein a depth of annealing is selected from the group consisting of (1) as great as a depth of work hardening, (2) less than a thickness of one layer, and (3) more than a thickness of one layer.

5. The method of claim 1 wherein the exposing is performed prior to separating the sacrificial material from the structural material.

6. The method of claim 1 wherein the exposing of portions of the surface does not expose all lateral portions of the structural material.

7. The method of claim 6 wherein the exposing of portions of the surface exposes those portions of the surface of the structural material having a structural thickness of less than 100 microns in the layer stacking direction.

8. The method of claim 1 wherein the exposing of portions of the surface exposes all portions of the surface of the structural material.

9. The method of claim 8 wherein the exposing of portions of the surface further exposes at least some lateral regions occupied by sacrificial material.

10. In a method of forming a multi-layer three-dimensional structure, comprising:

(A) forming a plurality of successive layers of the structure with each successive layer adhered to a previously formed layer and with each successive layer comprising at least two materials, one of which is a structural material and the other of which is a sacrificial material, and wherein each successive layer defines a successive cross-section of the three-dimensional structure, and wherein the forming of each of the plurality of successive layers comprises;

(i) depositing a first of the at least two materials;

(ii) depositing a second of the at least two materials; and

(B) after the forming of the plurality of successive layers, separating at least a portion of the sacrificial material from the structural material to reveal the three-dimensional structure, wherein the improvement comprises;

in association with the formation of at least one of the successive layers, depositing a primary structural material in a lateral region of the layer to form at least a majority of the one successive layer in the lateral region, and thereafter planarizing the primary structural material to form a surface of the one successive layer, and thereafter applying heat to selected portions of the surface or to the surface as a whole which results in less distortion of the lateral region after the separating than would exist in absence of the heating.

11. The method of claim 10 wherein operations applied to the given one of the successive layers is applied to the formation of a plurality of the successive layers.

12. The method of claim 10 wherein the heating is supplied by laser radiation.

13. The method of claim 10 wherein the exposing is performed prior to separating the sacrificial material from the structural material.

14. The method of claim 10 wherein the selected portions are selected from the group consisting of:

(1) selected structural material regions but less than all structural material regions, (2) all structural material regions, (3) selected structural and sacrificial material regions but less than all structural and sacrificial material regions, and (4) all structural and sacrificial material regions.

15. The method of claim 10 wherein the exposing of portions of the surface exposes those portions of the surface of the structural material having a structural thickness of less than 100 microns in the layer stacking direction.