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

• US 8,808,800 B2
• Filed: 03/01/2012
• Issued: 08/19/2014
• Est. Priority Date: 05/07/2002
• Status: Expired due to Fees

• Current Assignee: Microfabrica Incorporated (Technoprobe S.P.A.)
• Original Assignee: Microfabrica Incorporated (Technoprobe S.P.A.)
• Inventors: Kumar, Ananda H., Albarran, Jorge Sotelo, Cohen, Adam L., Kim, Kieun, Lockard, Michael S., Frodis, Uri, Smalley, Dennis R.
• Primary Examiner(s): Empie, Nathan
• Assistant Examiner(s): ZHAO, XIAO SI
• Application Number:
  US13/409,950
• Publication Number:
  US 20120222960A1
• Time in Patent Office: 901 Days
• Field of Search: 427/271, 438/381, 324/762
• US Class Current: 427/271
• 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, except for a first 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 includes;

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

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

(iii) planarizing 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, thereafter planarizing the primary structural material to a height that bounds the desired height of the given one of the successive layers and such that at least a portion of the primary structural material of the given one of the successive layers is work hardened, and thereafter etching into the planarized primary structural material of the given one of the successive layers to form one or more openings that extend into the given one of the successive layers in a least a portion of the lateral region to remove at least a portion of the work hardened primary structural material such that a majority of the given one of the successive layers in the lateral region is formed, and

after the etching, depositing structural material into the one or more openings to form an additional part of the given one of the successive layers,

wherein the removal of work hardened primary structural material by etching and then depositing of structural material results in a structure having less internal stress than the structure would otherwise have.

3. The method of claim 1 where curvature during formation of the structure is reduced by plating material periodically on the back side of the substrate as a thickness of deposited material on the front side is increased, wherein the reduction in curvature is based on the curvature that would have existed in the absence of the plating of material periodically on the back side.

4. The method of claim 3 wherein the material plated on the back side of the substrate is planarized after being deposited.

2. 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, except for a first 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 includes;

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

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

(iii) planarizing 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, performing the following steps in order;

(1) depositing a primary structural material in a lateral region of the given one of the successive layers, (2) planarizing the primary structural material to a height that bounds the desired height of the given one of the successive layers and such that at least a portion of the primary structural material of the given one of the successive layers is work hardened, and (3) etching into the planarized primary structural material of the given one of the successive layers to form one or more openings that extend into the given one of the successive layers in a least a portion of the lateral region to remove at least a portion of the work hardened primary structural material such that a majority of the given one of the successive layers in the lateral region is formed, and

wherein in association with formation of a subsequent successive layer that is located on the given one of the successive layers, depositing structural material into the one or more openings.

5. 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, except for a first 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 includes;

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

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

(iii) planarizing 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;

forming at least given one layer such that a structural material on the given layer is provided with an upper surface, planarizing the upper surface, and thereafter forming notches in the planarized upper surface in a desired pattern where the notches provide decoupling of stress located in separated regions of structural material.