RCLED Cavity Formation Using Etch Stop and Hybrid Bonding
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Solution Overview
Problem
Conventional RCLED manufacturing processes face challenges in defining the cavity length accurately and require separate CMOS fabrication, which complicates the integration of resonant cavity light emitting elements, especially for micro-LED displays.
Innovation Solution
A method for forming resonant cavity light emitting elements in a CMOS environment using an etch stop layer to define cavity length during processing, involving etching, hybrid bonding, and deposition of a distributed Bragg reflector, enabling precise cavity definition and integration with a wafer-to-wafer bonding backplane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional RCLED manufacturing process is used, then light emitting elements can be produced, but cavity length definition is inaccurate and requires complex fine-tuning
Solution Approach 1:
The patent introduces an etch stop layer as an intermediary element within the epitaxial structure. This layer serves as a precise reference plane that defines the cavity length by stopping the etching process at a predetermined depth, thereby eliminating the need for complex fine-tuning and achieving accurate cavity length definition through a simple process control mechanism.
2Ease of manufacture
If separate CMOS fabrication process is used for RCLED manufacturing, then light emitting elements can be produced, but integration with backplane becomes complex
Solution Approach 1:
The patent merges the RCLED fabrication process with the standard CMOS backplane fabrication process into a single integrated flow. By incorporating the etch stop layer during the epitaxial growth stage and using it as a reference for subsequent etching and bonding operations, the method enables both the light emitting elements and the backplane to be manufactured in the same CMOS facility without requiring separate fabrication processes, thereby simplifying integration.
3Manufacturing precision
If etch stop layer is introduced in epitaxial stack, then cavity length can be accurately defined, but additional processing step is required
Solution Approach 1:
The etch stop layer is incorporated during the initial epitaxial growth stage, performing the cavity length definition action in advance. By establishing the precise etching termination plane before subsequent processing steps, the method enables accurate cavity length definition to be achieved as part of the standard fabrication sequence rather than requiring additional corrective or adjustment steps later in the process.
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
Facilitates accurate cavity length definition and integration of RCLEDs in a CMOS environment, enhancing manufacturing efficiency and suitability for micro-LED displays by improving electrical and optical performance.
Implementation Method 1
introducing the etch stop layer in the epitaxial stack... the etch stop layer effectively supports the etching process as well as defines one side of the cavity
Implementation Method 2
depositing a distributed Bragg reflector on top of the optically transparent conductive oxide layer
Implementation Method 3
a second substrate dielectrically bonded to the optically transparent conductive oxide layer... hybrid bonding the previously etched first structure to a carrier substrate
Data Source
Figure 1
Figure 2A~2B
Figure 2C~2D
AI summary
A method (100) is provided for forming resonant cavity light emitting elements. The method comprises a step (101) of forming a first structure comprising a first substrate, a stop layer, a light emitting epitaxial structure, a conductive oxide layer, and a second substrate dielectrically bonded to the conductive oxide layer. The method further comprises a step (102) of etching from the first substrate up to the stop layer to etch away the first substrate. Additionally, the method comprises a step (103) of forming a plurality of light emitting mesa modules, each having a metal layer deposited on the stop layer. Furthermore, the method comprises a step (104) of hybrid bonding the previously etched first structure to a carrier substrate to form a second structure. Furthermore, the method comprises a step (105) of etching from the second substrate up to the conductive oxide layer. Moreover, the method comprises a step (106) of depositing a distributed Bragg reflector on top of the conductive oxide layer, thereby forming the resonant cavity light emitting elements.