Light Emitting Device Wafer Bonding Thermal Stress Management
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge in manufacturing light emitting devices is the difficulty in achieving good wafer bonding characteristics while preventing substrate cracking during heat treatment, especially when using substrates with different thermal expansion coefficients, which affects the brightness and reliability of the devices.
Innovation Solution
A method involving the formation of multilayer bodies with substrates of varying thermal expansion coefficients, where a first bonding step is performed at a lower temperature to ensure initial bonding strength, followed by a second bonding step at a higher temperature to enhance bonding strength and prevent cracking, using metal layers like Ti/Pt/Au and AuSn eutectic solder to facilitate bonding and reduce stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single high-temperature bonding step is used to achieve strong bonding, then bonding strength is improved, but substrate cracking occurs due to thermal stress from thermal expansion coefficient differences
Solution Approach 1:
The bonding process is divided into multiple stages: a first bonding step at a lower temperature (e.g., 100-300°C) to form an initial bond, followed by a second bonding step at a higher temperature (e.g., 300-600°C) to enhance bonding strength. This segmentation allows the substrate to adapt gradually to thermal stress, preventing cracking while achieving strong bonding
Solution Approach 2:
The bonding temperature parameter is changed dynamically through a two-step process. The first bonding step uses a lower temperature parameter to minimize thermal stress, and the second bonding step increases the temperature parameter to maximize bonding strength. This parameter change strategy resolves the contradiction between bonding strength and substrate integrity
2Reliability
If substrates with different thermal expansion coefficients are used to enable lattice matching, then light emission characteristics are improved, but wafer bonding becomes difficult due to thermal stress
Solution Approach 1:
The manufacturing process is segmented into multiple bonding steps with different temperature parameters. The first bonding step at lower temperature enables wafer bonding despite thermal expansion coefficient differences, while the second bonding step at higher temperature strengthens the bond. This segmentation makes the manufacturing process feasible while maintaining light emission characteristics
Solution Approach 2:
Temperature parameters are changed through a two-step bonding process. The first step uses a lower temperature parameter to enable bonding between substrates with different thermal expansion coefficients, and the second step increases the temperature to strengthen the bond. This parameter change approach resolves the manufacturing difficulty while preserving optical properties
3Reliability
If low-temperature bonding is used to prevent substrate cracking, then substrate reliability is improved, but bonding strength is insufficient
Solution Approach 1:
The bonding process is segmented into two sequential steps: a first bonding step at lower temperature to prevent substrate cracking and ensure substrate integrity, followed by a second bonding step at higher temperature to enhance bonding strength. This segmentation allows both substrate reliability and bonding strength requirements to be satisfied
Solution Approach 2:
The first bonding step performs a preliminary bonding action at lower temperature to secure substrate integrity before the second bonding step enhances bonding strength at higher temperature. This preliminary action prevents cracking early in the process, allowing subsequent strength enhancement without compromising substrate reliability
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 improves the bonding strength and reduces stress at the wafer interface, leading to increased brightness, reliability, and mass productivity of light emitting devices with reduced voids and dislocations, making them suitable for illumination and display applications.
Implementation Method 1
a first bonding step configured to heat the first metal layer and the second metal layer being in contact with each other
Implementation Method 2
a second substrate having a thermal expansion coefficient different from a thermal expansion coefficient of the first substrate
Data Source
AI summary
A method for manufacturing a light emitting device, includes: forming a first multilayer body including a first substrate, a first semiconductor layer provided on the first substrate and having a light emitting layer, and a first metal layer provided on the first semiconductor layer; forming a second multilayer body including a second substrate having a thermal expansion coefficient different from a thermal expansion coefficient of the first substrate, and a second metal layer provided on the second substrate; a first bonding step configured to heat the first metal layer and the second metal layer being in contact with each other; removing the first substrate after the first bonding step; and a second bonding step configured to perform, after the removing, heating at a temperature higher than a temperature of the first bonding step.