Stress Induced Cleaving of Semiconductor Devices
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for dicing semiconductor devices like LEDs from sapphire substrates often result in damage to the wafer and LEDs due to compressive stress from GaN layers, leading to undesired breakage and destruction.
Innovation Solution
A method involving the deposition of a continuous compressive stress layer, etching grooves to increase local stress, and generating a pattern of defects with a laser to facilitate controlled dicing using pressure, such as roll breaking, which reduces the force needed for substrate separation and allows for non-traditional geometries like hexagonal shapes for improved light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional dicing methods are used to separate LEDs from sapphire substrate, then substrate separation is achieved, but damage to wafer and LEDs occurs due to compressive stress
Solution Approach 1:
The method performs preliminary actions by depositing a sacrificial layer and creating grooves before the actual dicing process. This prepares the substrate with pre-defined weak points that guide the breaking process, preventing uncontrolled stress-induced damage to the LEDs while enabling clean separation.
Solution Approach 2:
A sacrificial layer is introduced as an intermediary between the GaN layer and the sapphire substrate. This layer absorbs and redistributes the compressive stress, preventing direct stress transfer to the substrate that would cause catastrophic failure during dicing operations.
2Productivity
If continuous GaN layer is deposited on sapphire substrate, then LED fabrication is enabled, but compressive stress causes substrate curvature and undesired breakage
Solution Approach 1:
The method extracts or removes the problematic continuous GaN layer structure by creating grooves that segment it into isolated regions. This eliminates the continuous compressive stress path while preserving the LED functional areas, preventing substrate curvature and breakage.
Solution Approach 2:
The grooves create local variations in the GaN layer structure, transforming the uniform continuous layer into a segmented structure with different mechanical properties in different regions. The areas between grooves maintain LED functionality while the groove regions relieve stress, achieving local stress management.
3Ease of manufacture
If sapphire substrate is thinned and etched to create scribe marks, then dicing is facilitated, but additional processing steps and potential damage increase
Solution Approach 1:
The grooves are created as a preliminary action during the LED fabrication process itself, before the dicing operation. This eliminates the need for separate substrate thinning and scribe mark creation steps, simplifying the overall process while enabling controlled breaking.
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 approach minimizes damage during dicing, enables the production of complex LED geometries, and enhances light extraction efficiency by reducing reflection coefficients, particularly for hexagonal shapes compared to square dies, while also being more cost-effective and scalable for large-area substrates.
Implementation Method 1
depositing a continuous first layer over the substrate, such that the first layer imparts a compressive stress to the substrate
Implementation Method 2
generating a pattern of defects in the substrate with a laser beam
Data Source
AI summary
A method of dicing semiconductor devices includes depositing a continuous first layer over the substrate, such that the first layer imparts a compressive stress to the substrate, and etching grooves in the first layer to increase local stress at the grooves compared to stress at the remainder of the first layer located over the substrate. The method also includes generating a pattern of defects in the substrate with a laser beam, such that a location of the defects in the pattern of defects substantially corresponds to a location of at least some of the grooves in the in the first layer, and applying pressure to the substrate to dice the substrate along the grooves.