Strained Semiconductor Zone Formation via Trench Layout
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Solution Overview
Problem
Existing methods for forming microelectronic devices with both tensile and compressive strained semiconductor zones are complex and lengthy, requiring multiple epitaxy steps and the formation of buried strained dielectric zones.
Innovation Solution
A method involving the formation of trenches in a pre-strained layer above semiconductor zones, with specific dimensions and layouts, to create both tensile and compressive strained zones on the same substrate, allowing for strain transfer and improved strain control without the need for multiple epitaxy steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple epitaxy steps and buried strained dielectric zones are used to form both tensile and compressive strained zones, then both NMOS and PMOS transistor mobility is improved, but the manufacturing process becomes complex and lengthy
Solution Approach 1:
The patent changes the manufacturing approach from multiple epitaxy steps to a single epitaxy step followed by selective removal. By changing the process parameters (number of epitaxy steps, use of sacrificial layers), the patent achieves the same strain differentiation effect with reduced process complexity
Solution Approach 2:
The patent segments the semiconductor layer into different regions (first and second semiconductor layers) with different critical dimensions, allowing each region to experience different strain states from the same pre-strained substrate, thereby eliminating the need for multiple epitaxy steps
2Reliability
If different pre-strained substrates are used for NMOS and PMOS regions, then carrier mobility is enhanced, but the manufacturing process requires multiple substrate preparations
Solution Approach 1:
The patent makes a single pre-strained substrate serve multiple functions by creating different strain conditions in different regions through geometric design rather than requiring different substrates. The same substrate provides both tensile and compressive strain to different semiconductor regions
Solution Approach 2:
The patent applies local quality by making the critical dimension of semiconductor layers location-dependent. The first semiconductor layer has a smaller critical dimension than the second, causing different strain transfer characteristics to adjacent transistor regions, thereby achieving localized strain differentiation
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 simplifies the process of forming microelectronic devices with both tensile and compressive strained zones, enhancing strain control and reducing complexity, while maintaining high strain levels and electrical performance.
Implementation Method 1
A method involving the formation of trenches in a pre-strained layer above semiconductor zones, with specific dimensions and layouts, to create both tensile and compressive strained zones on the same substrate, allowing for strain transfer
Data Source
AI summary
A method of forming a microelectronic device comprising, on a same support: at least one semi-conductor zone strained according to a first strain, and at least one semi-conductor zone strained according to a second strain, different to the first strain, comprising: the formation of semi-conductor zones above a pre-strained layer, then trenches extending through the thickness of the pre-strained layer, the dimensions and the layout of the semi-conductor zones as a function of the layout and the dimensions of the trenches being so as to obtain semi-conductor zones having a strain of the same type as that of the pre-strained layer and semi-conductor zones having a strain of a different type to that of the pre-strained layer.