Multi-Wafer Photodetector Bonding to Reduce SiGe Defect Leakage
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Solution Overview
Problem
The integration of germanium (Ge) or silicon germanium (SiGe) based photodetectors with silicon substrates is hindered by a dense defect layer caused by lattice mismatch, leading to increased leakage current and degraded signal-to-noise ratio due to high threading dislocation density, which is challenging to address using traditional semiconductor manufacturing technologies.
Innovation Solution
The use of pre-PD homogeneous and heterogeneous wafer bonding techniques, along with multi-stack PD device structures, allows for the transfer of high-quality Si x Ge 1-x materials from a donor wafer to a carrier wafer, reducing the impact of the defect layer and enabling the fabrication of photodetectors with improved performance by burying the heterogeneous interface within high dopant concentrations and removing the high TDD Ge layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If direct growth of SiGe materials on silicon substrates is used, then photodetector fabrication is enabled using traditional semiconductor manufacturing technologies, but a dense defect layer with high threading dislocation density is formed causing leakage current and degraded signal-to-noise ratio
Solution Approach 1:
The patent segments the photodetector structure into multiple functional layers grown on separate wafers that are subsequently bonded together. The SiGe absorption layer is grown on one wafer while the Si substrate is prepared separately, allowing defect minimization through controlled bonding interfaces rather than direct growth on the substrate.
Solution Approach 2:
The patent introduces an intermediary bonding interface between the SiGe layer and Si substrate through wafer bonding technology. This intermediary approach allows the two materials to be joined without direct epitaxial growth, thereby avoiding the formation of a dense defect layer while maintaining structural integrity.
2Reliability
If wafer bonding techniques are used to transfer SiGe materials, then the defect layer impact is reduced and photodetector performance is improved, but the device structure and fabrication process become more complex
Solution Approach 1:
The patent performs preliminary actions by growing the SiGe absorption layer and preparing the Si substrate on separate wafers before bonding them together. This preliminary preparation allows optimization of each layer independently and simplifies the overall fabrication process despite the multi-wafer approach.
Solution Approach 2:
The patent employs a nested structure where the SiGe layer is transferred and bonded onto the Si substrate in a controlled sequence. The multi-layer structure is built through nested bonding steps, with each layer being precisely positioned and integrated, managing complexity through systematic layer-by-layer construction.
3Manufacturing precision
If high-quality SiGe materials are transferred from donor wafer to carrier wafer, then material quality and photodetector performance are enhanced, but additional wafer bonding steps and process control are required
Solution Approach 1:
The patent utilizes parameter changes in the wafer bonding process, such as controlling bonding temperature, pressure, and atmosphere, to achieve high-quality material transfer. By optimizing these parameters, the bonding process becomes more predictable and controllable, reducing the perceived complexity despite multiple bonding steps.
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 significantly reduces leakage current and enhances the signal-to-noise ratio of photodetectors by minimizing the effect of the defect layer, improving the quality of the photodetector material and facilitating integration with CMOS technologies.
Implementation Method 1
bonding the donor wafer and the carrier wafer together
Implementation Method 2
semiconductor photodetector
Data Source
Figure 1A
Figure 1B~1C
Figure 2A~2B
AI summary
Structures and techniques introduced here enable the design and fabrication of photodetectors (PDs) and/or other electronic circuits using typical semiconductor device manufacturing technologies meanwhile reducing the adverse impacts on PDs' performance. Examples of the various structures and techniques introduced here include, but not limited to, a pre-PD homogeneous wafer bonding technique, a pre-PD heterogeneous wafer bonding technique, a post-PD wafer bonding technique, their combinations, and a number of mirror equipped PD structures. With the introduced structures and techniques, it is possible to implement PDs using typical direct growth material epitaxy technology while reducing the adverse impact of the defect layer at the material interface caused by lattice mismatch.