Alumina insulation for coating implantable components and other microminiature devices

• US 20030087197A1
• Filed: 09/20/2002
• Published: 05/08/2003
• Est. Priority Date: 12/20/1996
• Status: Active Grant

• 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.
• Granted Patent: US 6,844,023 B2
• Time in Patent Office: Days
• 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. An implantable component comprising:

a substrate;

at least one electrical component mounted on said substrate, and

a biocompatible, insulative coating applied to selected portions of the substrate and the at least one electrical component, said-insulative coating comprising;

a layer of alumina, zirconia, magnesium oxide, or alloys of alumina, zirconia or magnesium oxide that is less than about 25 microns thick, said coating exhibiting insulative properties that maintain electrical leakage through said coating to less than about 1 μ

a/cm².

2. An implantable component comprising:

an electrical component; and

a biocompatible, insulative coating applied to said electrical component, said insulative coating comprising;

a layer of alumina, zirconia, magnesium oxide, or alloys of alumina, zirconia or magnesium oxide that is less than about 25 microns thick, said coating exhibiting insulative properties that maintain electrical leakage through said coating to less than about 1 μ

a/cm².

3. A biocompatible, insulative coating applied to a component, said insulative coating comprising a layer of alumina, zirconia, magnesium oxide, or alloys of alumina, zirconia or magnesium oxide, deposited on said component so as to form an insulative and protective coating that is less than about 25 microns thick, said coating exhibiting insulative properties that maintain electrical leakage through said coating to less than about 1 μ

a/cm², whereby said component with said coating applied thereto is implantable.

4. The biocompatible, insulative coating of claim 3 wherein said coating is less than about 10 microns thick.

5. The biocompatible, insulative coating of claim 3 wherein said component comprises a hybrid circuit having a substrate and a least one electrical component mounted on said substrate.

6. The biocompatible, insulative coating of claim 3 wherein said component comprises an integrated circuit chip.

7. The biocompatible, insulative coating of claim 3 wherein said component comprises a magnet.

9. The method set forth in claim 3 wherein step (b) comprises depositing, using an ion-enhanced evaporative sputtering technique, successive layers of alumina, zirconia, magnesium oxide, alloys of alumina, zirconia or magnesium oxide over the entire surface of the object.

10. The method set forth in claim 3 wherein step (b) comprises depositing, using an ion-beam deposition (IBD) technique, successive layers of alumina, zirconia, magnesium oxide, alloys of alumina, zirconia or magnesium oxide over selected portions of the object.

8. A method of placing a sealed, protective and insulative coating on an object to be submersed in a conductive medium, such as living tissue, said method comprising:

(a) depositing a layer of titanium on a surface of the object that is about 300 Å

thick; and

(b) depositing a layer of alumina, zirconia, magnesium oxide, alloys of alumina, zirconia or magnesium oxide over the surface of the object that is about 5-10 microns thick.

11. A method of applying a ceramic insulation layer over a device or component to be insulated comprising the steps of:

(a) sputtering a layer of titanium of at least about 300 Å

thick over those portions of the device or component which are to be insulated;

(b) applying a layer of photosensitive polyamide onto a surface of the device or component which is to be insulated;

(c) applying a mask that exposes those areas on the surface of the device or component where alumina is not to be applied;

(d) shining ultra violet (UV) light through the mask to polymerize the polyamide;

(e) washing off any unpolymerized polyamide with xylene or an equivalent substance;

(f) depositing a layer of alumina having a thickness of between 4 and 10 microns on the surface of the device or component which is to be insulated;

(g) breaking or scribing the alumina that was deposited over the polyamide;

(h) soaking the device or component in a pyrana solution (H₂SO₄×

4+H₂O₂×

2 heated to 60°

) for 30 to 60 minutes; and

(i) lifting off the polyamide, thereby removing alumina from those areas on the surface of the device or component in those areas where alumina is not wanted.