Mask-Less Fabrication of Thin Film Batteries
Thin film batteries (TFB) are fabricated by a process which eliminates and/or minimizes the use of shadow masks. A selective laser ablation process, where the laser patterning process removes a layer or stack of layers while leaving layer(s) below intact, is used to meet certain or all of the patterning requirements. For die patterning from the substrate side, where the laser beam passes through the substrate before reaching the deposited layers, a die patterning assistance layer, such as an amorphous silicon layer or a microcrystalline silicon layer, may be used to achieve thermal stress mismatch induced laser ablation, which greatly reduces the laser energy required to remove material.
1 . A method of fabricating a thin film battery, comprising:
depositing a first stack of blanket layers on a substrate, said stack comprising a cathode current collector layer, a cathode layer, an electrolyte layer, an anode layer and an anode current collector layer;
laser die patterning said first stack to form a second stack;
laser patterning said second stack to form a device stack, said laser patterning revealing a cathode current collector area and a portion of said electrolyte layer adjacent to said cathode current collector area, wherein said laser patterning of said second stack includes removing a part of the thickness of said portion of said electrolyte layer to form a step in said electrolyte layer; and
depositing on said device stack and patterning encapsulation and bonding pad layers.
2 . The method of claim 1 , wherein said depositing said first stack of blanket layers is completed without breaking vacuum.
3 . The method of claim 1 , further comprising depositing a blanket die patterning assistance layer on said substrate before said depositing said first stack of blanket layers, said first stack of blanket layers being deposited on said die patterning assistance layer, wherein said substrate is transparent to laser light and wherein said die patterning assistance layer includes a layer of material for achieving thermal stress mismatch between said die patterning assistance layer and said substrate.
4 . The method of claim 3 , wherein said laser die patterning includes laser irradiation through said substrate of a portion of said die patterning assistance layer and thermal stress mismatch induced ablation of a corresponding portion of said first stack.
5 . The method of claim 1 , wherein said laser patterning said second stack includes leaving a portion of the thickness of said cathode layer over the surface of said cathode current collector area.
6 . The method of claim 1 , wherein said bonding pad layer is deposited using a mask.
7 . The method of claim 1 , wherein said bonding pad layer and said encapsulation layer are blanket deposited on said device stack and laser patterned.
8 . The method of claim 7 , wherein said bonding pad layer is patterned to completely cover said encapsulation layer for providing further protection from the environment of active layers of said thin film battery.
9 . An apparatus for forming thin film batteries, comprising:
a first system for depositing a first stack of blanket layers on a substrate, said stack comprising a cathode current collector layer, a cathode layer, an electrolyte layer, an anode layer and an anode current collector layer;
a second system for laser die patterning said first stack to form a second stack; and
a third system for laser patterning said second stack to form a device stack, said laser patterning revealing a cathode current collector area and a portion of said electrolyte layer adjacent to said cathode current collector area, wherein said laser patterning said second stack includes removing a part of the thickness of said portion of said electrolyte layer to form a step in said electrolyte layer.
10 . The apparatus of claim 9 , wherein said second system and said third system are the same.
11 . The apparatus of claim 9 , further comprising a fourth system for depositing on said device stack and patterning encapsulation and bonding pad layers.
12 . The apparatus of claim 9 , wherein said first system further deposits a blanket die patterning assistance layer on said substrate before said depositing said first stack of blanket layers, said first stack of blanket layers being deposited on said die patterning assistance layer, wherein said substrate is transparent to laser light and wherein said die patterning assistance layer includes a layer of material for achieving thermal stress mismatch between said die patterning assistance layer and said substrate, and wherein said second system includes lasers configured to irradiate, through said substrate, a portion of said die patterning assistance layer to induce thermal stress mismatch ablation of a corresponding portion of said first stack.
13 . The apparatus of claim 9 , wherein said laser patterning said second stack includes leaving a portion of the thickness of said cathode layer over the surface of said cathode current collector area.
14 . A method of fabricating a thin film battery, comprising:
blanket depositing on a substrate and serially selectively laser patterning a current collector layer, a cathode layer and an electrolyte layer to form a first stack;
forming a lithium anode on said first stack to form a second stack;
blanket depositing and selectively laser patterning a bonding pad layer on said second stack to form a third stack; and
laser die patterning said third stack.
15 . The method of claim 14 , wherein said forming said lithium anode includes blanket depositing on said first stack and selectively laser patterning a lithium anode layer.
16 . The method of claim 14 , wherein said forming said lithium anode includes depositing lithium on said first stack using a mask.
17 . The method of claim 14 , further comprising depositing a blanket die patterning assistance layer on said substrate before said blanket depositing on a substrate and serially selectively laser patterning said current collector layer, said cathode layer and said electrolyte layer, said first stack of blanket layers being deposited on said die patterning assistance layer, wherein said substrate is transparent to laser light and wherein said die patterning assistance layer includes a layer of material for achieving thermal stress mismatch between said die patterning assistance layer and said substrate.
18 . The method of claim 17 , wherein said laser die patterning includes laser irradiation through said substrate of a portion of said die patterning assistance layer and thermal stress mismatch induced ablation of a corresponding portion of said first stack.
19 . An apparatus for forming thin film batteries, comprising:
a first system for blanket depositing on a substrate and serially selectively laser patterning a current collector layer, a cathode layer and an electrolyte layer to form a first stack;
a second system for forming a lithium anode on said first stack to form a second stack;
a third system for blanket depositing and selectively laser patterning a bonding pad layer on said second stack; and
a fourth system for laser die patterning said second stack.
20 . The apparatus of claim 19 , wherein said first system further deposits a blanket die patterning assistance layer on said substrate before said blanket depositing on a substrate and serially selectively laser patterning said current collector layer, said cathode layer and said electrolyte layer, said first stack of blanket layers being deposited on said die patterning assistance layer, wherein said substrate is transparent to laser light and wherein said die patterning assistance layer includes a layer of material for achieving thermal stress mismatch between said die patterning assistance layer and said substrate, and wherein said second system includes lasers configured to irradiate, through said substrate, a portion of said die patterning assistance layer to induce thermal stress mismatch ablation of a corresponding portion of said first stack.