SiGe Substrate With Multiple Germanium Concentrations
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Solution Overview
Problem
The continued miniaturization of metal oxide semiconductor field effect transistors (MOSFETs) is reaching scaling limits, necessitating new methods to improve performance beyond traditional scaling techniques.
Innovation Solution
A method for preparing a semiconductor substrate with multiple Silicon-Germanium (SiGe) regions of different Germanium concentrations using a single epitaxy process, involving the deposition of SiGe layers, a silicon layer, and thermal mixing to form new SiGe layers with uniform but distinct Germanium concentrations for each active region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If traditional scaling techniques are used to improve MOSFET performance, then device size is reduced, but scaling limits are reached and performance improvement becomes difficult
Solution Approach 1:
The patent applies local quality by creating regions with different Germanium concentrations (e.g., 0%, 25%, 50%, 75%) in specific areas of the semiconductor substrate. Each active region is selectively doped with Germanium to achieve desired threshold voltages and performance characteristics, rather than uniformly scaling all devices. This allows performance optimization through material composition variation instead of continued size reduction.
2Adaptability or versatility
If multiple pFETs with different Germanium concentrations are fabricated on the same substrate, then device performance and threshold voltage variation are improved, but process complexity increases
Solution Approach 1:
The patent segments the substrate into multiple active regions, each receiving different Germanium concentrations through selective epitaxial growth. Mask layers are used to define and protect specific regions during sequential Germanium deposition, enabling independent control of material composition in each segment without affecting others.
Solution Approach 2:
Mask layers are deposited and patterned in advance to define which regions will receive Germanium doping at each stage. This preliminary structuring allows subsequent epitaxial growth to selectively modify only intended regions, simplifying the overall process by pre-establishing the spatial configuration before material deposition begins.
3Manufacturing precision
If multiple epitaxy process runs are used to create different SiGe regions, then manufacturing precision is improved, but productivity decreases
Solution Approach 1:
The patent merges multiple Germanium deposition operations into a single continuous epitaxial process run. By sequentially depositing Germanium layers with different concentrations on different regions within one process cycle, the method achieves the precision of multiple separate runs while eliminating the downtime and reconfiguration required between independent process steps.
Solution Approach 2:
The epitaxial growth process continues uninterrupted through multiple deposition stages, with each stage adding Germanium at a different concentration to different regions. This continuous operation maintains optimal process conditions throughout, avoiding the start-stop cycles and parameter re adjustments that would occur with multiple separate runs, thereby improving both precision and productivity.
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 enables the creation of semiconductor devices with varying threshold voltages by forming regions with different Germanium concentrations on the same substrate, enhancing device performance and efficiency.
Implementation Method 1
thermally mixing the remaining Si and SiGe layers of the at least two active regions to form a new SiGe layer with uniform Germanium concentration
Data Source
AI summary
A substrate with two SiGe regions having different Germanium concentrations and a method for making the same. The method includes: providing a substrate with at least two active regions; epitaxially depositing a first SiGe layer over each active regions; epitaxially depositing a Silicon layer over each SiGe layer; epitaxially depositing a second SiGe layer over each Silicon layer; forming a hard mask over the second SiGe layer of one of the active regions; removing the epitaxially deposited second SiGe layer of the unmasked active region, removing the hard mask, and thermally mixing the remaining Silicon and SiGe layers of the active regions to form a new SiGe layer with uniform Germanium concentration for each of the active regions, where the new SiGe layer with uniform Germanium concentration of one of the at least two active regions has a different concentration of Germanium than the new SiGe layer with uniform Germanium concentration of the other SiGe layer.