Laser Lift-Off for Thin Device Chip Substrate Removal
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Solution Overview
Problem
The demand for thinner device chips requires a method to fully remove the base substrate from silicon on insulator wafers to achieve a device chip with only the device layer, while ensuring the wafer's integrity during handling.
Innovation Solution
A manufacturing method involving a wafer preparation step with a laser beam absorbing layer, a device layer dividing step using division grooves, and a lift-off step where a laser beam is applied to absorb in the laser beam absorbing layer to remove the base substrate, allowing for the separation of individual device chips from the wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the base substrate is fully removed to achieve thinner device chips, then the device chip thickness is reduced, but the wafer integrity during handling deteriorates
Solution Approach 1:
A laser beam absorbing layer is formed on the base substrate before device fabrication. This preliminary action enables selective laser removal of the base substrate later in the process, allowing thinning of the device chip while maintaining wafer integrity during handling through controlled ablation after devices are formed and tested
Solution Approach 2:
The base substrate is selectively removed (extracted) from the wafer structure using laser ablation through the absorbing layer. This extraction enables the device chip to be thinned to the desired thickness while the absorbing layer facilitates clean removal without damaging the device layer, resolving the contradiction between thinning and maintaining integrity
2Ease of operation
If division grooves are formed to separate device chips, then individual device chips can be separated, but the structural integrity of the wafer deteriorates
Solution Approach 1:
Division grooves are formed only in specific regions where device separation is needed, while the rest of the wafer maintains its full structural integrity. This localized approach allows easy separation of individual device chips along the grooves without compromising the overall wafer strength during handling and processing
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively produces device chips with only the device layer, achieving a thickness of substantially 10 μm and addressing the need for thinner chips while maintaining wafer integrity during handling.
Implementation Method 1
applying a laser beam of such a wavelength as to be absorbed in the laser beam absorbing layer
Implementation Method 2
applying a laser beam of such a wavelength as to be absorbed in the laser beam absorbing layer, from the base substrate side, and lifting off a device chip
Data Source
AI summary
A manufacturing method for a device chip includes a wafer preparation step of preparing a wafer including a base substrate, a laser beam absorbing layer layered on a front surface of the base substrate, and a device layer being layered on the laser beam absorbing layer and having devices formed in respective separate regions demarcated by a plurality of crossing division lines, a device layer dividing step of forming respective division grooves that divide at least the device layer into individual device chips along the plurality of division lines, and a lift-off step of, after the device layer dividing step is carried out, applying a laser beam of such a wavelength as to be absorbed in the laser beam absorbing layer, from the base substrate side, and lifting off a device chip from the front surface of the base substrate.