THIN FILM BATTERY DEVICE HAVING RECESSED SUBSTRATE AND METHOD OF FORMATION

1 . A device, comprising:

a substrate, the substrate comprising:

an upper surface; and

a recess extending from the upper surface into the substrate;

an active device region, the active device region disposed within the recess and having a first thickness; and

an encapsulant, the encapsulant disposed over the recess and over the active device region, wherein the encapsulant has a second thickness, wherein the encapsulant extends above the upper surface of the substrate to a first distance, and wherein the first distance is less than a sum of the first thickness and second thickness.

2 . The device of claim 1 , wherein the recess extends to a first depth from the upper surface into the substrate, wherein the first depth is greater than or equal to the first thickness.

3 . The device of claim 1 , the active device region comprising a plurality of layers.

4 . The device of claim 3 , wherein the device is a thin film battery, the plurality of layers comprising:

a cathode current collector;

a lithium-containing cathode;

a solid state electrolyte disposed on the lithium-containing cathode; and

an anode region disposed on the solid state electrolyte;

and an anode current collector disposed on the anode region, the anode current collector being further disposed adjacent the encapsulant.

5 . The device of claim 1 , wherein the encapsulant comprises a plurality of layers, wherein the plurality of layers comprises at least one rigid layer and at least one polymer layer.

6 . The device of claim 1 , wherein a portion of the encapsulant is disposed around the active device region within the recess.

7 . The device of claim 1 , further comprising a planarizing polymer layer disposed between the encapsulant and the active device region.

8 . The device of claim 7 , wherein the planarizing polymer layer comprises a cured polymer.

9 . The device of claim 7 , wherein the planarizing polymer layer comprises at least one of: an elongation till break of 70% or greater and an elastic modulus of less than 20 GPa.

10 . A thin film battery, comprising:

a substrate, the substrate comprising:

an upper surface; and

a recess extending from the upper surface into the substrate along a first direction;

an active device region, the active device region being disposed within the recess and having a first thickness, wherein the active device region comprises:

a lithium-containing cathode;

a solid state electrolyte disposed on the lithium-containing cathode; and

an anode region disposed on the solid state electrolyte; and

an encapsulant disposed on the active device region, wherein the encapsulant comprises:

at least one rigid layer; and

at least one polymer layer.

11 . The thin film battery of claim 10 , wherein the encapsulant has a second thickness, wherein the encapsulant extends above the upper surface of the substrate to a first distance, and wherein the first distance is less than a sum of the first thickness and second thickness.

12 . The thin film battery of claim 10 , wherein the recess comprises a localized height variation along the first direction.

13 . The thin film battery of claim 10 , wherein the active device region further comprises an anode current collector and a cathode current collector, the anode current collector and the cathode current collector extending onto the upper surface of the substrate.

14 . The thin film battery of claim 10 wherein the at least one polymer layer is encapsulated within the encapsulant.

15 . A method of forming a device, comprising:

providing a substrate having an upper surface;

forming a recess within the substrate, the recess extending from the upper surface into the substrate;

forming an active device region within the recess, the active device region having a first thickness; and

forming an encapsulant over the active device region, wherein the encapsulant has a second thickness, and wherein the encapsulant extends above the upper surface of the substrate to a first distance, wherein the first distance is less than a sum of the first thickness and second thickness.

16 . The method of claim 15 , wherein the forming the active device region comprises:

depositing a cathode current collector;

depositing a lithium-containing cathode layer on the cathode current collector;

depositing a solid state electrolyte layer on the lithium-containing cathode layer;

depositing an anode layer of the solid state electrolyte layer;

depositing an anode current collector; wherein the cathode current collector, the lithium-containing cathode layer, solid state electrolyte, the anode layer, and the anode current collector form an active device stack; and

patterning the active device stack to define a patterned stack disposed within the recess.

17 . The method of claim 15 , wherein the forming the encapsulant comprises:

depositing a polymer layer; and

depositing a rigid layer, wherein the polymer layer and the rigid layer form a stack of layers.

18 . The method of claim 15 wherein the forming the recess comprises:

forming a substrate precursor in a green state;

molding the substrate precursor to form a recessed structure having an initial size in the substrate precursor; and

heating the substrate precursor to form the recess in the substrate, wherein the recess has a final size different from the initial size.

19 . The method of claim 15 wherein the forming the recess comprises:

providing the substrate as a planar substrate; and

etching the substrate to form the recess using laser micromachining, or using lithographic patterning and etching.