Composite Substrate Grinding for Sapphire Thickness Uniformity
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Solution Overview
Problem
The challenge in manufacturing composite substrates for optical devices is achieving uniform thickness of the sapphire substrate while bonding a heat sink substrate, as existing methods result in exposure of the optical device layer and instability in device quality due to non-uniform thicknesses.
Innovation Solution
A method involving sequential grinding steps to uniform the sapphire substrate thickness, forming the optical device layer, bonding the heat sink substrate, and further grinding to ensure uniform composite substrate thickness, preventing exposure of the optical device layer during thickness reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the sapphire substrate thickness is reduced to about 10 μm by grinding in the conventional method, then the productivity is improved and the device size is reduced, but the optical device layer may be exposed causing degradation in quality and stability
Solution Approach 1:
The patent applies preliminary action by performing a first grinding step to uniform the sapphire substrate thickness to a predetermined value (e.g., 10 μm) **before** bonding the heat sink substrate. This preliminary thickness uniforming ensures that when subsequent grinding is performed after bonding, the optical device layer will not be exposed, thus preventing quality degradation while maintaining productivity benefits of thin substrates.
Solution Approach 2:
The patent segments the grinding process into two distinct stages: (1) first grinding of the sapphire substrate before bonding to achieve preliminary thickness uniformity, and (2) second grinding of the composite substrate after bonding to achieve final thickness uniformity. This segmentation allows each grinding step to be optimized independently, ensuring the optical device layer is protected while achieving the desired final thickness.
2Ease of manufacture
If the thicknesses of sapphire substrate, bonding metal layer, and heat sink substrate are non-uniform, then the bonding process becomes simpler, but the composite substrate thickness cannot be uniformed causing quality instability
Solution Approach 1:
The patent performs preliminary grinding of the sapphire substrate to uniform thickness **before** bonding, establishing a consistent baseline thickness. This preliminary action compensates for subsequent variations introduced during bonding, allowing the bonding process to remain simple while ensuring the final composite substrate achieves uniform thickness after the second grinding step.
Solution Approach 2:
The patent employs a feedback mechanism through two sequential grinding steps. The first grinding establishes an initial thickness reference, bonding is performed, then the second grinding adjusts the final thickness based on the combined thickness of all layers. This feedback approach allows the system to compensate for non-uniformities introduced during bonding while maintaining manufacturing simplicity.
3Reliability
If individual heat sinks are bonded to each small-sized optical device, then the heat radiation efficiency is improved, but the productivity is reduced due to troublesome individual bonding
Solution Approach 1:
The patent merges multiple individual bonding operations into a single batch bonding process. By bonding one heat sink substrate to an entire optical device wafer containing multiple devices simultaneously, the method maintains the heat radiation efficiency of individual heat sinks while dramatically improving productivity through parallel processing of multiple devices in one bonding step.
Solution Approach 2:
The heat sink substrate serves as a universal component that can be bonded to multiple optical devices simultaneously. This multi-functional approach allows a single heat sink substrate to provide heat radiation service to numerous devices at once, eliminating the need for separate bonding operations for each device while maintaining effective heat dissipation for each individual device.
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 ensures uniform thickness of the sapphire substrate and composite substrate, maintaining the integrity of the optical device layer and stabilizing the quality of each optical device, even when reducing the sapphire substrate thickness to 5 μm.
Implementation Method 1
grinding the back side of the heat sink substrate in the condition where the sapphire substrate of the composite substrate is held on a chuck table of a grinding apparatus
Implementation Method 2
bonding the front side of the heat sink substrate through a bonding metal layer to the front side of the optical device layer
Data Source
AI summary
A composite substrate manufacturing method including the steps of grinding a sapphire substrate to uniform the thickness of the sapphire substrate, next forming an optical device layer on the front side of the sapphire substrate, next bonding the front side of a heat sink substrate through a bonding metal layer to the front side of the optical device layer formed on the front side of the sapphire substrate to thereby form a composite substrate, next grinding the back side of the heat sink substrate of the composite substrate to uniform the thickness of the composite substrate, and finally grinding the back side of the sapphire substrate of the composite substrate to reduce the thickness of the sapphire substrate to a predetermined thickness.