Strain Buffer Oxide Layer for MOS Device Lattice Mismatch
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Solution Overview
Problem
Conventional methods for generating stress in MOS device channel regions to improve carrier mobility result in lattice misfit defects and high leakage currents due to lattice mismatch between semiconductor materials.
Innovation Solution
The formation of strain buffer layers by oxidizing interface regions between semiconductor regions with mismatched lattice constants, which reduces defects and separates the channel regions from underlying layers, thereby reducing leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a first semiconductor material is grown on a second semiconductor material through epitaxy to generate stress in the channel region, then carrier mobility is improved, but lattice misfit defects occur at the interface between the first and second semiconductor materials
Solution Approach 1:
An intermediate layer is introduced between the first semiconductor material and the second semiconductor material. This intermediate layer has a lattice constant that gradually transitions from the lattice constant of the second semiconductor material to the lattice constant of the first semiconductor material, thereby reducing lattice misfit defects at the interface while maintaining the stress-induced carrier mobility improvement in the channel region.
Solution Approach 2:
The lattice constant parameter is gradually changed across the intermediate layer, creating a gradient structure that transitions from the lattice constant of the second semiconductor material to that of the first semiconductor material. This gradual parameter change reduces the abrupt lattice mismatch that causes misfit defects.
2Reliability
If a first semiconductor material is grown on a second semiconductor material through epitaxy to generate stress in the channel region, then carrier mobility is improved, but leakage current increases due to interface defects
Solution Approach 1:
The intermediate layer acts as a mediator that reduces interface defects between the first and second semiconductor materials. By providing a gradual lattice constant transition, it minimizes the generation of misfit defects that would otherwise create leakage current paths, thereby reducing harmful leakage current while preserving carrier mobility enhancement.
Solution Approach 2:
The intermediate layer converts the potentially harmful abrupt lattice mismatch into a beneficial gradual transition. What would normally be a source of defects and leakage current (the lattice mismatch) is transformed into a controlled gradient structure that reduces defects and leakage current while maintaining the desired stress effect for carrier mobility improvement.
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 formation of strain buffer layers effectively eliminates lattice misfit defects and reduces leakage currents, enhancing the performance of MOS devices by managing stress and improving carrier mobility.
Implementation Method 1
performing an oxidation process to form an oxide in an interface region between the first semiconductor region and the second semiconductor region
Data Source
AI summary
A device includes a substrate, insulation regions extending into the substrate, and a semiconductor fin higher than top surfaces of the insulation regions. The semiconductor fin has a first lattice constant. A semiconductor region includes sidewall portions on opposite sides of the semiconductor fin, and a top portion over the semiconductor fin. The semiconductor region has a second lattice constant different from the first lattice constant. A strain buffer layer is between and contacting the semiconductor fin and the semiconductor region. The strain buffer layer includes an oxide.