III-Nitride LED Wafer Bonding to High-Index Glass Substrate
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Solution Overview
Problem
Current methods for forming light emitting devices limit the choice of materials due to temperature constraints, leading to potential deterioration of performance and delamination or cracking, especially when using glasses that require bonding temperatures above 400°C, which also tend to be optically absorbing at shorter wavelengths.
Innovation Solution
A semiconductor structure with a light emitting layer between n-type and p-type regions is bonded to a high index substrate after growth, allowing processing into light emitting devices at higher temperatures, enabling the use of materials with higher melting points and lower optical absorption, such as high refractive index glasses, which improves device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If bonding is performed before processing into light emitting devices, then lower processing temperatures are used, but the choice of materials is limited and performance deteriorates
Solution Approach 1:
The wafer is bonded to the second substrate before being processed into individual light emitting devices. This preliminary bonding action enables subsequent high-temperature processing steps that would otherwise be impossible, allowing the use of superior materials and higher processing temperatures that improve device performance while maintaining manufacturing feasibility
2Reliability
If higher bonding temperatures are used, then material performance improves, but delamination and cracking occur
Solution Approach 1:
The bonding temperature is increased to enable the use of high melting point materials with lower optical absorption. By carefully selecting materials with matched thermal expansion coefficients and controlling the bonding process parameters, the method achieves high-temperature bonding without causing delamination or cracking, thereby improving device performance
3Object-affected harmful factors
If glasses with higher bonding temperatures are used, then optical absorption decreases, but bonding temperature requirements increase
Solution Approach 1:
The method changes the bonding temperature parameter to match the requirements of high-temperature glasses that have lower optical absorption characteristics. By performing bonding after device fabrication, the process can utilize these superior optical materials without being constrained by low-temperature bonding limitations
4Reliability
If thermal expansion matching is improved, then bonding reliability improves, but material selection becomes more constrained
Solution Approach 1:
By performing bonding after device fabrication rather than before, the method changes the process sequence parameter that enables the use of materials with higher melting points and better optical properties. This sequence change allows for improved thermal expansion matching between bonded materials while maintaining or expanding material selection flexibility for the optical components
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 allows for the use of higher bonding temperatures, reducing the risk of delamination and cracking, and improves the optical performance of light emitting devices by using materials with lower optical absorption and better thermal expansion matching, resulting in enhanced device performance and reliability.
Implementation Method 1
the wafer is bonded to a second substrate
Implementation Method 2
a stack of semiconductor layers of different compositions and dopant concentrations on a sapphire, silicon carbide, III-nitride, or other suitable substrate by metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or other epitaxial techniques
Implementation Method 3
The phosphor converts a portion of the primary light to secondary light at longer wavelengths
Data Source
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AI summary
A method according to embodiments of the invention includes providing a wafer including a semiconductor structure grown on a growth substrate, the semiconductor structure comprising a III-nitride light emitting layer sandwiched between an n-type region and a p-type region. The wafer is bonded to a second substrate. The growth substrate is removed. After bonding the wafer to the second substrate, the wafer is processed into multiple light emitting devices.