Laser-induced flaw formation in nitride semiconductors
View Patent ↗An embodiment is a method to induce flaw formation in nitride semiconductors. Regions of a thin film structure are selectively decomposed within a thin film layer at an interface with a substrate to form flaws in a pre-determined pattern within the thin film structure. The flaws locally concentrate stress in the pre-determined pattern during a stress-inducing operation. The stress-inducing operation is performed. The stress-inducing operation causes the thin film layer to fracture at the pre-determined pattern.
1. A method comprising:
selectively decomposing regions of a thin film structure within a thin film layer to form flaws in a pre-determined pattern within the thin film structure, the flaws locally concentrating stress in the pre-determined pattern during a stress-inducing operation to fracture the thin film layer at the pre-determined pattern during the stress-inducing operation, wherein the thin film layer has a thickness and each of the flaws are formed to have a depth, wherein the thickness of the thin film layer is greater than the depth of the flaws, and wherein the predetermined pattern is configured to maintain the thickness of the thin film layer when the thin film layer is fractured in the stress-inducting operation; and
performing the stress-inducing operation, the stress-inducing operation causing the thin film layer to fracture at the pre-determined pattern.
2. The method of claim 1 wherein selectively decomposing comprises:
irradiating the thin film structure by a focused laser with a small spot size to form focused spots; and
stitching the focused spots at a fixed spacing to form the pre-determined pattern.
3. The method of claim 2 further comprising:
repeating irradiating and stitching until a desired penetration depth is achieved, wherein the desired penetration depth corresponds to the depth of the flaws.
4. The method of claim 2 wherein the stress-inducing operation further causing a substrate that is attached to the thin film layer to be removed, and wherein irradiating the thin film structure comprises:
irradiating from top surface of the thin film structure toward the interface with the substrate.
5. The method of claim 2 wherein the stress-inducing operation further causing a substrate that is attached to the thin film layer to be removed, and wherein irradiating the thin film structure comprises:
irradiating from backside of the thin film structure through the substrate.
6. The method of claim 1 wherein selectively decomposing comprises:
decomposing the regions near diced edges of the thin film structure.
7. The method of claim 1 wherein at least one of the flaws is a trench, a notch, or a void formation.
8. The method of claim 1 wherein the thin film layer is an alloy containing nitrogen.
9. The method of claim 8 wherein the alloy is one of Gallium Nitride (GaN), Aluminum Gallium Nitride (AlGaN), Indium Gallium Nitride (InGaN), and Aluminum Indium Gallium Nitride (AlInGaN).
10. The method of claim 1 wherein performing the stress-inducing operation comprises:
performing a laser lift-off (LLO) procedure.
11. The method of claim 1 wherein the thin film structure is one of a light emitting diode (LED) structure, a transistor structure, and a laser structure.
12. The method of claim 11 wherein the thin film layer is an epitaxially grown LED, transistor, or laser layer.