Strained SiGe Fin Formation on Single Substrate
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Solution Overview
Problem
The continued miniaturization of metal oxide semiconductor field effect transistors (MOSFETs) is reaching scaling limits, and existing methods for applying strain to silicon germanium alloy fins are insufficient to achieve desired performance targets, particularly for high percentage compressive and tensile strained silicon germanium alloy fins integrated on the same substrate.
Innovation Solution
A method of forming semiconductor structures with compressive strained silicon germanium alloy fins and tensile strained silicon germanium alloy fins on the same substrate, where a germanium containing layer and a silicon layer are formed on silicon germanium alloy fins and then converted using thermal anneal to achieve the desired strain and germanium content, allowing for the fabrication of p-channel and n-channel FET devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If embedded stressor materials are used in the source region and drain region to apply strain, then some strain effect is achieved, but the strain values are insufficient to obtain desired performance targets due to the small volume of epitaxy in 10 nm and beyond technologies
Solution Approach 1:
The substrate is divided into first and second portions with different crystal orientations (e.g., <110> and <100>). Silicon germanium alloy fins are selectively formed on each portion, allowing independent strain engineering for nFETs and pFETs. This segmentation enables each fin type to be optimized for its specific device requirements without compromising the other.
Solution Approach 2:
Different germanium contents are assigned to different portions of the substrate: higher germanium content (50-70 atomic percent) on the first portion for compressive strain in pFETs, and lower germanium content (10-40 atomic percent) on the second portion for tensile strain in nFETs. This local differentiation of material composition enables optimized strain characteristics for each device type.
2Reliability
If high percentage compressive strained silicon germanium alloy fins are formed for pFETs, then desired performance targets are achieved, but it becomes difficult to integrate tensile strained silicon germanium alloy fins for nFETs on the same substrate using traditional methods
Solution Approach 1:
The substrate is segmented into distinct regions with different crystal orientations, allowing independent formation of compressive and tensile strained fins. This spatial segmentation resolves the conflict between integrating high percentage compressive strained fins for pFETs and tensile strained fins for nFETs on the same substrate.
Solution Approach 2:
The patent employs asymmetric substrate portions with different crystal orientations (<110> vs. <100>) to enable different strain types. This asymmetry allows the formation of both high percentage compressive strained fins and tensile strained fins on the same substrate, accommodating both pFET and nFET requirements.
3Stress or pressure
If the germanium content is increased to achieve high percentage compressive strain for pFETs, then performance targets are met, but the ability to provide tensile strain for nFETs on the same substrate is compromised
Solution Approach 1:
The patent applies different germanium contents to different substrate portions: high germanium content (50-70 atomic percent) on the first portion for compressive strain in pFETs, and low germanium content (10-40 atomic percent) on the second portion for tensile strain in nFETs. This local quality differentiation enables both strain types to coexist on the same substrate.
Solution Approach 2:
By segmenting the substrate into regions with different germanium contents and crystal orientations, the patent enables simultaneous formation of high percentage compressive strained fins and tensile strained fins, providing both strain types needed for complementary CMOS devices.
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 integration of high percentage compressive and tensile strained silicon germanium alloy fins on the same substrate, enhancing drive currents and overcoming the limitations of traditional strain application methods, thus improving CMOS device performance beyond traditional scaling.
Implementation Method 1
the first set of the silicon germanium alloy fins containing the germanium containing layer is converted into compressive strained silicon germanium alloy fins having a first germanium content, while also converting the second set of the silicon germanium alloy fins containing the silicon layer into tensile strained silicon germanium alloy fins having a second germanium content
Data Source
AI summary
A method of forming a semiconductor structure that includes compressive strained silicon germanium alloy fins having a first germanium content and tensile strained silicon germanium alloy fins having a second germanium content that is less than the first germanium content is provided. The different strained and germanium content silicon germanium alloy fins are located on a same substrate. The method includes forming a cladding layer of silicon around a set of the silicon germanium alloy fins, and forming a cladding layer of a germanium containing material around another set of the silicon germanium alloy fins. Thermal mixing is then employed to form the different strained and germanium content silicon germanium alloy fins.