Image Sensor Pixel Recess Structure for Dislocation Defect Control
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Solution Overview
Problem
The integration of non-silicon semiconductor materials into silicon wafers for image sensor devices often results in dislocation defects due to lattice mismatch, leading to poor performance and premature device failure, as these defects introduce stress and degrade electrical and optical properties.
Innovation Solution
The method involves modifying the profile of recesses in the silicon substrate to aggregate dislocation defects at the bottom portion, using curve-based bottom surfaces or protruded patterns, and covering sidewalls with doped dielectric layers to constrain threading dislocation defects, which are then removed to minimize their impact on the active regions of the image sensor device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-silicon semiconductor materials are integrated into silicon wafers, then performance of image sensor devices is improved, but dislocation defects occur due to lattice mismatch
Solution Approach 1:
A graded buffer layer is introduced as an intermediary between the silicon substrate and the non-silicon semiconductor layer. This buffer layer has a composition that gradually transitions from pure silicon at the substrate interface to the final non-silicon composition at the top surface, acting as a mediator that reduces lattice mismatch and minimizes dislocation defects
Solution Approach 2:
The composition parameter of the buffer layer is changed gradually through its thickness. By varying the non-silicon material concentration from 0% at the silicon substrate interface to 100% at the top surface, the lattice constant changes progressively, reducing stress and dislocation formation compared to abrupt interfaces
2Adaptability or versatility
If epitaxial growth is performed to form non-silicon semiconductor layers, then device functionality is achieved, but threading dislocation defects propagate through the layers
Solution Approach 1:
The dislocation defects that form during epitaxial growth are converted from harmful propagating defects into beneficial aggregated defects confined to the buffer layer. The buffer layer acts as a defect sink, where dislocations are generated but then pinned and aggregated at specific regions, preventing them from propagating into the active device layers
Solution Approach 2:
The semiconductor structure is segmented into distinct functional regions: a silicon substrate, a graded buffer layer for defect management, and active device layers for functionality. This segmentation isolates the defect-generating epitaxial growth process to the buffer layer region, separating harmful defect propagation from the functional device regions
3Ease of manufacture
If standard CMOS process is used for fabricating circuitry, then cost-efficiency is improved, but integration with non-silicon materials becomes complex
Solution Approach 1:
The graded buffer layer structure serves multiple functions: it provides lattice matching for epitaxial growth, acts as a defect sink for dislocation aggregation, and maintains compatibility with standard CMOS fabrication processes. This multi-functionality allows simultaneous achievement of low-cost manufacturing and reliable non-silicon device integration
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 dislocation defects in the epitaxially grown non-silicon semiconductor layers, enhancing the performance and reliability of the image sensor device by minimizing their negative impact on electrical and optical properties.
Implementation Method 1
covering sidewalls with doped dielectric layers to constrain threading dislocation defects
Implementation Method 2
filling the plurality of openings with a second semiconductor material... epitaxially grown non-silicon semiconductor layers
Data Source
AI summary
A method includes forming a plurality of openings extending into a substrate from a front surface of the substrate. The substrate includes a first semiconductor material. Each of the plurality of openings has a curve-based bottom surface. The method includes filling the plurality of openings with a second semiconductor material. The second semiconductor material is different from the first semiconductor material. The method includes forming a plurality of pixels that are configured to sense light in the plurality of openings, respectively, using the second semiconductor material.