Shaped Cavities for Embedding SiGe in Semiconductor Devices
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Solution Overview
Problem
Conventional semiconductor manufacturing techniques for silicon germanium (SiGe) devices face challenges in scaling down, particularly in maintaining carrier mobility and device performance due to difficulties in growing lattice-matched SiGe alloys and uniformly embedding SiGe at the Si-STI interface, leading to inadequate cavity shapes for embedding SiGe materials.
Innovation Solution
The development of shaped cavities with convex regions in semiconductor substrates, which increase the volume of SiGe material that can be embedded, improving carrier mobility and device performance by allowing for a larger opening size and controlled deposition of SiGe material, enhancing the performance of CMOS devices compared to conventional U-shaped and Σ-shaped cavities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional U-shaped or Σ-shaped cavities are used for embedding SiGe material, then the manufacturing process is simple, but the cavity volume is insufficient leading to inadequate carrier mobility and device performance
Solution Approach 1:
The patent applies curvature by transitioning from conventional U-shaped or Σ-shaped cavities to cavities with curved sidewalls. The curved sidewalls increase the cavity volume compared to straight-walled cavities of the same footprint, allowing more SiGe material to be embedded. This curvature-based design resolves the contradiction by providing increased volume without proportionally increasing manufacturing complexity, as the curved walls can be formed through standard deposition and etching processes.
Solution Approach 2:
The patent extends the cavity design into the vertical dimension by creating overhanging sidewalls that protrude laterally. This dimensional extension increases the effective cavity volume beyond what would be achievable with simple planar expansions. The overhanging structure allows SiGe material to be embedded in a three-dimensional configuration, resolving the volume limitation while maintaining compatibility with existing manufacturing processes through controlled deposition techniques.
2Quantity of substance
If the cavity opening size is increased to embed more SiGe material, then the SiGe volume increases, but the control over SiGe deposition becomes difficult
Solution Approach 1:
The patent applies local quality by creating regions with different sidewall characteristics within the same cavity. The overhanging sidewalls provide localized geometric features that guide SiGe deposition, ensuring that material is deposited preferentially in desired regions. This local geometric variation allows precise control over where SiGe material accumulates, resolving the contradiction by enabling large total volumes while maintaining deposition control through spatially differentiated cavity geometry.
Solution Approach 2:
The patent employs preliminary action by pre-forming the cavity structure with specific overhanging sidewall geometries before SiGe deposition. This pre-configured geometry acts as a template that guides subsequent SiGe material deposition, ensuring controlled filling even for large volumes. The preliminary cavity shaping establishes deposition pathways and termination points, resolving the control issue while enabling increased material quantity.
3Reliability
If SiGe material is embedded at the Si-STI interface, then device performance is improved, but uniform embedding is difficult to achieve with conventional cavity shapes
Solution Approach 1:
The patent applies curvature to the cavity sidewalls to create smooth, continuous surfaces that facilitate uniform SiGe deposition. The curved geometry eliminates sharp corners and abrupt transitions that cause non-uniform material distribution. This curved surface design ensures consistent SiGe embedding along the entire Si-STI interface, resolving the contradiction by providing both high device performance through complete interface coverage and manufacturing precision through uniform deposition.
Solution Approach 2:
The patent achieves homogeneity by designing cavity geometries that promote uniform SiGe material distribution. The overhanging sidewalls and curved surfaces create consistent deposition conditions throughout the cavity, ensuring homogeneous SiGe embedding at the Si-STI interface. This homogeneous structure delivers reliable device performance while maintaining manufacturing precision through uniform material properties throughout the embedded region.
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
The shaped cavities provide a 5-10% increase in volume for SiGe material, resulting in improved PMOS performance and yield, with better control over SiGe material deposition, addressing the limitations of existing techniques by enhancing carrier mobility and device performance.
Implementation Method 1
maintaining carrier mobility and device performance due to difficulties in growing lattice-matched SiGe alloys
Implementation Method 2
The middle portion includes convex sidewalls interfacing the substrate
Data Source
AI summary
The present invention is directed to semiconductor processes and devices. More specifically, embodiments of the present invention provide a shaped cavity that this later to be filled with SiGe material. The shape cavity comprises convex regions interfacing the substrate. There are other embodiments as well.