Semiconductor Substrate Removal via Underfill Support
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for removing growth substrates from light-emitting diodes (LEDs) often result in damage to the semiconductor or metallization layers, leading to poor optical extraction efficiency due to the large refractive index difference between the substrate and the III-nitride layers, and there is a need for techniques that are compatible with manufacturing processes and enable advanced device designs.
Innovation Solution
A semiconductor structure is attached to a carrier using a metal bond or interconnects like solder or gold stud bumps, with an underfill material introduced between the carrier and the semiconductor structure to support the removal of the growth substrate without causing damage, and the underfill is cured to form a rigid structure that encloses a wavelength converting material or photonic crystal for enhanced light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser dissociation is used to remove the sapphire substrate, then the substrate can be removed, but the semiconductor or metallization layers are damaged
Solution Approach 1:
The patent introduces an intermediary layer between the sapphire substrate and the III-nitride device layers. This intermediary layer is selectively removable and protects the semiconductor and metallization layers during substrate removal, preventing direct exposure to damaging laser dissociation or etching processes while allowing the substrate to be removed.
Solution Approach 2:
The patent segments the interface between the substrate and device layers by introducing a removable intermediary layer. This segmentation allows the substrate to be removed through selective removal of the intermediary layer without directly affecting the sensitive semiconductor and metallization layers, thus resolving the contradiction between substrate removal and layer protection.
2Temperature
If a sapphire substrate is used, then high temperature stability is achieved, but light extraction efficiency is reduced due to refractive index difference
Solution Approach 1:
The patent introduces an intermediary layer that serves as an optical transition medium between the sapphire substrate and the III-nitride device layers. This layer has a refractive index intermediate between sapphire (1.8) and the device layers (2.4), reducing the abrupt refractive index difference and minimizing total internal reflection, thereby improving light extraction efficiency while maintaining the high temperature stability provided by the sapphire substrate.
3Illumination intensity
If the growth substrate is removed to improve optical properties, then light extraction efficiency is improved, but the semiconductor structure becomes unsupported and vulnerable
Solution Approach 1:
The patent performs preliminary action by attaching the semiconductor structure to a carrier before removing the growth substrate. This preliminary attachment provides structural support during and after substrate removal, preventing the semiconductor structure from becoming vulnerable or damaged while still allowing the optical benefits of substrate removal to be achieved.
4Reliability
If conventional wet etches are used for Si or GaAs substrates, then substrate removal is achieved, but manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by designing the intermediary layer with specific localized properties that enable selective removal. The intermediary layer has a composition and structure tailored for selective removal by conventional wet etches used in III-nitride manufacturing, allowing substrate removal to be integrated into existing manufacturing processes without significantly increasing manufacturing complexity.
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 allows for the removal of the growth substrate without damaging the semiconductor, improving optical properties and enabling advanced device designs by increasing light extraction efficiency through the use of wavelength converting materials and photonic crystals.
Implementation Method 1
an underfill material which supports the semiconductor structure is introduced in the space between the interconnects
Implementation Method 2
the underfill is cured to form a rigid structure
Implementation Method 3
a wavelength converting material such as a phosphor is disposed on the surface of the semiconductor structure exposed by substrate removal
Implementation Method 4
a photonic crystal is formed in the surface of the semiconductor structure exposed by substrate removal
Implementation Method 5
In the case of a sapphire substrate, removal may be by means of laser dissociation of GaN at the GaN/sapphire interface
Data Source
Figure 1~2
Figure 3~5
Figure 6~7
AI summary
A semiconductor structure (110) formed on a growth substrate (10) and including a light emitting layer disposed between an n-type region and a p-type region is attached to a carrier (30) by a connection (37, 42, 44) that supports the semiconductor structure (110) sufficiently to permit removal of the growth substrate (10). In some embodiments, the semiconductor structure is a flip chip device (32). The semiconductor structure may be attached to the carrier by, for example, a metal bond (37) that supports almost the entire lateral extent of the semiconductor structure (110), or by interconnects (42) such as solder or gold stud bumps. An under fill material (44) which supports the semiconductor structure (110) is introduced in any spaces between the interconnects (42). The under fill material (44) may be a liquid that is cured to form a rigid structure. The growth substrate (10) may then be removed without causing damage to the semiconductor structure (110).