Alumina insulation for coating implantable components and other microminiature devices

• US 7,160,672 B2
• Filed: 06/10/2005
• Issued: 01/09/2007
• Est. Priority Date: 12/20/1996
• Status: Expired due to Fees

• Current Assignee: Alfred E. Mann Foundation For Scientific Research
• Original Assignee: Alfred E. Mann Foundation For Scientific Research
• Inventors: Shah, Rajiv, Schulman, Joseph H., Lucisano, Joseph Y., Byers, Charles L., Pendo, Shaun M.
• Primary Examiner(s): McPherson; John A.
• Assistant Examiner(s): CHACKO DAVIS, DABORAH
• Application Number:
  US11/150,547
• Publication Number:
  US 20050233172A1
• Time in Patent Office: 578 Days
• Field of Search: None
• US Class Current: 430/315
• CPC Class Codes: A61N 1/02 Details
• CPC Class Codes: C23C 14/042 using masks
• CPC Class Codes: G03F 7/70641 Focus
• CPC Class Codes: H01L 21/308 using masks H01L21/3063, H01L21/3065 take precedence
• CPC Class Codes: H01L 23/291 Oxides or nitrides or carbides, e.g. ceramics, glass
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H05K 3/284 for encapsulating mounted components H05K1/185 takes precedence
• CPC Class Codes: Y10T 29/49144 by metal fusion
• CPC Class Codes: Y10T 428/24802 Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]
• CPC Class Codes: Y10T 428/24917 including metal layer
• CPC Class Codes: Y10T 428/24926 including ceramic, glass, porcelain or quartz layer
• CPC Class Codes: Y10T 428/265 1 mil or less

Abstract

A protective, biocompatible coating or encapsulation material protects and insulates a component or device intended to be implanted in living tissue. The coating or encapsulation material comprises a thin layer or layers of alumina, zerconia, or other ceramic, less than 25 microns thick, e.g., 5–10 microns thick. The alumina layer(s) may be applied at relatively low temperature. Once applied, the layer provides excellent hermeticity, and prevents electrical leakage. Even though very thin, the alumina layer retains excellent insulating characteristics. In one embodiment, an alumina layer less than about 6 microns thick provides an insulative coating that exhibits less than 10 pA of leakage current over an area 75 mils by 25 mils area while soaking in a saline solution at temperatures up to 80° C. over a three month period.

Claims

1. A method of selectively applying a ceramic coating to an object, comprising:

(a) forming a layer of metal over the object;

(b) forming a layer of photosensitive polyamide over the metal layer;

(c) applying a mask over the object for exposing areas of the polyamide layer that are formed over portions of the metal layer where the ceramic layer is not to be applied;

(d) exposing the object to radiation through the mask such that exposed areas of the polyamide layer are polymerized and unexposed areas of the polyamide layer remain unpolymerized;

(e) removing the unpolymerized areas of the polyamide layer;

(f) forming a layer of ceramic material over the object such that first portions of the ceramic layer are formed over the polymerized areas of the polyamide layer and second portions of the ceramic layer are formed over the metal layer;

(g) scribing the first portions of the ceramic layer;

(h) soaking the object in a solution for removing the first portions of the ceramic layer and the polymerized areas of the polyamide layer; and

(i) removing the first portions of the ceramic layer and the polymerized areas of the polyamide layer.

2. The method recited in claim 1, wherein the ceramic material is selected from the group consisting essentially of alumina, zirconia, magnesium oxide, alloy of alumina, alloy of zirconia, and alloy of magnesium oxide.

3. The method recited in claim 1, wherein the ceramic layer has a thickness less than about 25 microns.

4. The method recited in claim 3, wherein the ceramic layer has a thickness of between about 4 and 10 microns.

5. The method recited in claim 1, wherein the ceramic layer is formed using ion enhanced evaporation.

6. The method recited in claim 1, wherein the ceramic layer is formed using ion beam deposition.

7. The method recited in claim 1, wherein the solution for removing the first portions of the ceramic layer and the polymerized areas of the polyamide layer is a H₂SO₄×

4+H₂O₂×

2 solution.

8. The method recited in claim 7, wherein the solution is heated to approximately 60 degrees Centigrade.

9. The method recited in claim 1, wherein the metal layer is a titanium layer.

10. The method recited in claim 1, wherein the metal layer has a thickness of approximately 300 Angstroms.

11. The method recited in claim 1, further including iteratively repositioning the object while the ceramic layer is being formed.

12. The method recited in claim 1, further including:

(f) testing the formed ceramic layer for desired properties; and

repeating (f) and (f) if properties of the formed ceramic layer are not the desired properties.

13. The method recited in claim 12, wherein testing the formed ceramic layer for desired properties includes:

(a) contacting at least a portion of the object having the ceramic layer formed thereon with a substance reactive to the metal layer; and

(b) determining if there is a reaction between the substance and the metal layer.

14. The method recited in claim 13, wherein the desired properties include an absence of micro-holes.

15. The method recited in claim 12, wherein testing the formed ceramic layer for desired properties includes:

(a) immersing the object in a conductive solution; and

(b) applying a voltage to the object.

16. The method recited in claim 15, wherein the desired properties include an electrical leakage through the ceramic layer of less than about 1 μ

a/cm².

17. The method recited in claim 1, wherein the radiation is ultra violet light.

18. The method recited in claim 1, wherein the unpolymerized areas of the polyamide layer are removed using xylene.