Implantable microelectronic device and method of manufacture
An implantable hermetically sealed microelectronic device and method of manufacture are disclosed. The microelectronic device of the present invention is hermetically encased in a insulator, such as alumina formed by ion bean assisted deposition (“IBAD”), with a stack of biocompatible conductive layers extending from a contact pad on the device to an aperture in the hermetic layer. In a preferred embodiment, one or more patterned titanium layers are formed over the device contact pad, and one or more platinum layers are formed over the titanium layers, such that the top surface of the upper platinum layer defines an external, biocompatible electrical contact for the device. Preferably, the bottom conductive layer is larger than the contact pad on the device, and a layer in the stack defines a shoulder.
1. A method of making an implantable electronic device comprising:
providing an electronic component having contact pads on a surface;
applying a polymer layer to the surface of the electronic component;
patterning the polymer layer including forming voids over the contact pads;
applying a conductive layer to the surface including the polymer layer and the voids over the contact pads; and
removing the polymer layer by physically pulling and peeling the polymer layer off of the surface, leaving a patterned conductive layer covering at least the contact pads.
2. The method according to claim 1 , wherein the step of patterning is patterning by photolithography.
3. The method according to claim 1 , wherein the electronic component is an integrated circuit having on its surface a passivation layer including openings for the contact pads.
4. The method according to claim 1 , wherein the contact pads are aluminum.
5. The method according to claim 1 , wherein the step of applying a polymer layer is applying polyimide.
6. The method according to claim 5 , wherein the polyimide is applied between 5 μm and 15 μm thick.
7. The method according to claim 1 , wherein the step of patterning includes
sputtering an aluminum mask on the polymer layer,
patterning the aluminum mask through photolithography, and
patterning the polymer layer through reactive ion etch through the aluminum mask.
8. The method according to claim 7 , wherein the step of patterning the polymer layer through reactive ion etch also roughens a surface of the electronic component to improve metal adhesions.
9. The method according to claim 1 , wherein the step of applying a conductive layer comprises applying a titanium layer.
10. The method according to claim 9 , wherein the titanium layer is applied by ion beam assisted deposition.
11. The method according to claim 10 , wherein the titanium layer is applied between 2 μm and 8 μm thick.
12. The method according to claim 9 , further comprising applying a platinum layer over the titanium layer.
13. The method according to claim 1 , wherein the conductive layer extends beyond the edges of the contract pad.
14. The method according to claim 1 , wherein the conductive layer is biocompatible.
15. The method according to claim 14 , wherein the contact pad is not biocompatible.
16. The method according to claim 1 , further comprising applying an insulating layer over the electronic component defining voids over the conductive layer, but smaller than the conductive layer.
17. The method according to 16 , wherein the insulating layer is ceramic.
18. The method according to claim 17 , wherein the ceramic is alumina.
19. The method according to claim 16 , wherein the insulating layer and the conductive layer form a hermetic seal around the electronic component.