# US 12,109,651 B2 · Laser processing method for thin film structures

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- Number: US 12,109,651 B2
- Document ID: US12109651B2
- Status: Granted
- Kind: B2
- Application number: 16/971,185
- Filed: 2019-04-02
- Published: 2021-04-08
- Granted: 2024-10-08
- Earliest claimed: 2018-04-03
- Assignees: Ilika Technologies Limited
- Applicants: Ilika Technologies Limited
- Inventors: Brian Hayden; Louise Turner; Thomas Risbridger; Thomas Foley; Nadeem Rizvi
- Web page: https://patentgrep.com/patent/US12109651B2

## CPC

- B23K 26/38: by boring or cutting
- B23K 26/36: Removing material (B23K26/55, B23K26/57 take precedence)
- B23K 26/40: taking account of the properties of the material involved
- B23K 26/402: involving non-metallic material, e.g. isolators
- H01M 10/058: Construction or manufacture
- B23K 26/0624: {using ultrashort pulses, i.e. pulses of 1 ns or less}
- B23K 26/082: Scanning systems, i.e. devices involving movement of the laser beam relative to the laser head
- B23K 2101/36: Electric or electronic devices
- B23K 2103/166: {Multilayered materials}
- B23K 2103/172: {wherein at least one of the layers is non-metallic}
- B23K 2103/18: Dissimilar materials
- B23K 2103/50: {Inorganic materials other than metals or composite materials}
- Y02E 60/10: Energy storage using batteries
- Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product
- B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

A method of processing a thin film structure comprising: providing a thin film structure comprising a stack of two or more thin film layers supported on a surface of a substrate, the stack having a depth orthogonal to the substrate surface; and forming a cut through the depth of the stack by using a direct write laser technique to scan a laser beam along a scan path covering an area of a desired cut line on a surface of the stack to ablate material of the stack along the cut line and through the depth of the stack at least to the surface of the substrate; wherein the direct write laser technique is implemented using an ultrashort pulsed laser outputting pulses with a duration of 1000 femtoseconds or less, at a wavelength in the range of 100 to 1500 nm, and delivering a fluence in the range of 50 to 100,000 mJ/cm2.

## Claims

### Claim 1

A method of processing a thin film structure comprising:
providing the thin film structure comprising a stack of two or more thin film layers supported on a surface of a substrate, the stack having a depth orthogonal to the surface of the substrate;
forming a cut having a cut line width through the depth of the stack by using a direct write laser technique to scan a laser beam having a laser beam diameter or a spot width along a scan path covering an area of a desired cut line on a surface of the stack to ablate a material of the stack by creating a plasma from the material along the cut line and through the depth of the stack at least to the surface of the substrate, wherein the laser beam diameter is smaller than the cut line width and the laser beam is scanned relative to the cut line width as well as along its length to remove a required width of material;
wherein the direct write laser technique is implemented using an ultrashort pulsed laser outputting pulses with a duration of 1000 femtoseconds or less, at a wavelength in a range of 100 to 1500 nm, and delivering a fluence in a range of 50 to 100,000 mJ/cm2;
and further wherein the spot width of the laser beam is 0.001 to 0.1 mm and the cut line has a width of 0.015 to 2 mm;
the method further comprising the steps of, after forming the cut through the depth of the stack, applying a layer of dielectric material to cover the surface of the stack, as well as to cover one or more side walls and a base of the cut; and
subsequently slicing through a remaining thickness of the substrate at the base of the cut.

### Claim 2 (depends on 1)

The method of claim 1, wherein said laser outputting pulses have a duration selected from:
a. 300 femtoseconds or less;
b. 200 femtoseconds or less; or
c. 100 to 200 femtoseconds.

### Claim 3 (depends on 1)

The method of claim 1, wherein said laser beam is scanned along the scan path at a scan speed selected from:
a. of 1 to 10,000 mm/s;
b. 50 to 600 mm/s; or
c. 100 to 500 mm/s.

### Claim 4 (depends on 1)

The method of claim 1, where said pulses are output from said laser at a repetition rate selected from:
a. 0.1 to 10,000 kHz;
b. 1 to 1000 KHz;
c. 1 to 500 KHz;
d. 1 to 200 KHz;
e. 10 to 200 kHz; or
f. 100 to 200 KHz.

### Claim 5 (depends on 1)

The method of claim 1, wherein said laser beam is scanned along the scan path one or more times to ablate the material of the stack.

### Claim 6 (depends on 1)

The method of claim 1, wherein said laser beam is incident on the surface of the stack with the spot width selected from:
a. 0.001 to 0.01 mm;
b. 0.01 to 0.1 mm; or
c. 0.01 to 0.02 mm.

### Claim 7 (depends on 1)

The method of claim 1, wherein said cut line has the width selected from:
a. 0.1 to 2 mm; or
b. 0.5 to 1 mm.

### Claim 8 (depends on 1)

The method of claim 1, wherein said laser beam is incident on the surface of the stack with the spot width which is one-fiftieth or less than the width of the cut line.

### Claim 9 (depends on 1)

The method of claim 1, wherein said laser beam is incident on the surface of the stack with a spot having an intensity profile that is greatest in a centre of the spot.

### Claim 10 (depends on 9)

The method of claim 9, wherein said intensity profile is a Gaussian profile or a Bessel profile.

### Claim 11 (depends on 1)

The method of claim 1, wherein said ablation is continued until the cut has a depth substantially level with the surface of the substrate or is continued until the cut has a depth that extends past the surface of the substrate, wherein said depth is selected from:
a. 500 μm or less;
b. 200 μm or less;
c. 100 μm or less;
d. 1-100 μm;
e. 1-50 μm;
f. 1-25 μm;
g. 1-10 μm; or
h. 10 μm or less.

### Claim 12 (depends on 1)

The method of claim 1, wherein said depth of the stack is selected from:
a. 200 μm or less;
b. 50 to 200 μm;
c. 5 to 100 μm;
d. 5 to 50 μm;
e. 10 to 40 μm; or
f. 10 to 20 μm.

### Claim 13 (depends on 1)

The method of claim 1, wherein said laser is scanned in a sinusoidal pattern.

### Claim 14 (depends on 13)

The method of claim 13, wherein said sinusoidal pattern comprises a wave with a propagation that is perpendicular to the cut line width, with peak-to-peak amplitude equal or less than the cut line width.

### Claim 15 (depends on 1)

The method of claim 1, wherein said cut line is shaped to divide the stack into a plurality of elements which are isolated from one another by the cut.

### Claim 16 (depends on 1)

The method of claim 1, wherein said thin film layers of the stack correspond to layers of a battery comprising:
a. a positive electrode active material;
b. an electrolyte material;
c. a negative electrode active material; and
d. a negative electrode current collector.

### Claim 17 (depends on 16)

The method of claim 16, wherein:
a. said substrate is a conductive substrate;
b. said positive electrode active material is LiCoO2;
c. said electrolyte material is LIPON, lithium borosilicate, or nitrogen doped lithium borosilicate;
d. said negative electrode active material is amorphous Si; and
e. said negative electrode current collector is platinum or molybdenum.

### Claim 18 (depends on 1)

A method of fabricating a thin film battery which includes using the method of claim 1 to form a cut which isolates an element intended for the battery from a thin film structure comprising a stack of thin film battery layers.