Selective Epitaxy Trenches for Defect-Free III-V Growth
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods fail to effectively co-integrate lattice mismatched materials like III-V materials with Silicon substrates, leading to defects and performance issues in CMOS devices due to large lattice mismatches, particularly during selective epitaxial growth in trenches.
Innovation Solution
The solution involves selectively epitaxially growing a buffer material with sloped or vertically oriented sidewalls in trenches to trap and prevent crystalline defects, using aspect ratio trapping (ART) and specific growth conditions to ensure the epitaxial material grows without colliding with oxide sidewalls, thereby reducing defects and improving device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lattice mismatched materials (III-V, Ge) are grown on Silicon substrate, then device performance and electron/hole movement are improved, but crystalline defects are generated due to large lattice mismatch
Solution Approach 1:
The epitaxial growth process is segmented into multiple stages: initial growth stage where defects are allowed to form, and subsequent growth stage where defect-free material is deposited. This segmentation separates the harmful defect generation from the final device structure, allowing high-quality material to be obtained despite lattice mismatch.
Solution Approach 2:
The method performs preliminary defect trapping by growing material with sloped sidewalls that intercept defects before they can propagate into the device region. This preliminary action prevents defects from reaching the critical device areas, enabling reliable device operation despite using lattice mismatched materials.
2Manufacturing precision
If selective epitaxial growth is performed in trenches with vertical oxide sidewalls, then manufacturing precision is improved, but sidewall defects are generated due to collision between epitaxial material and oxide sidewalls
Solution Approach 1:
Instead of maintaining vertical sidewalls and accepting collision defects, the method inverts the approach by intentionally creating sloped sidewalls that angle away from the epitaxial growth direction. This inversion prevents collision between the growing material and sidewalls, eliminating sidewall defects while maintaining manufacturing precision through controlled slope angles.
3Speed
If trench depth is increased to improve device performance, then electron movement in n-MOS channels is improved, but defect propagation into device layers increases
Solution Approach 1:
The sloped sidewalls act as an intermediary structure that intercepts and traps defects before they can propagate vertically into the device layers. This intermediary mechanism allows deep trenches to be formed for high-performance devices while preventing defect propagation, as the sloped geometry creates a barrier that deflects defects away from the vertical growth path.
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 crystalline defects, enhancing the performance and yield of CMOS devices by preventing defects from propagating into device layers, resulting in faster and more reliable circuit devices.
Implementation Method 1
selectively epitaxially growing a buffer material... on a top surface of a substrate material
Implementation Method 2
aspect ratio trapping (ART)... to trap and prevent crystalline defects
Data Source
AI summary
Trenches (and processes for forming the trenches) are provided that reduce or prevent crystaline defects in selective epitaxial growth of type III-V or Germanium (Ge) material (e.g., a “buffer” material) from a top surface of a substrate material. The defects may result from collision of selective epitaxial sidewall growth with oxide trench sidewalls. Such trenches include (1) a trench having sloped sidewalls at an angle of between 40 degrees and 70 degrees (e.g., such as 55 degrees) with respect to a substrate surface; and/or (2) a combined trench having an upper trench over and surrounding the opening of a lower trench (e.g., the lower trench may have the sloped sidewalls, short vertical walls, or tall vertical walls). These trenches reduce or prevent defects in the epitaxial sidewall growth where the growth touches or grows against vertical sidewalls of a trench it is grown in.