Strain-creating Element with Varying Composition for Transistor Mobility
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Solution Overview
Problem
The reduction of channel length in field effect transistors leads to strain relaxation in strain-creating elements, resulting in reduced mobility of charge carriers in the channel region, which affects the performance of the transistors.
Innovation Solution
Forming strain-creating elements with a varying chemical composition, where the concentration ratio of the first and second chemical elements changes across different portions, reducing strain gradients and minimizing crystal defects, thereby maintaining strain and enhancing carrier mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the channel length is reduced to increase the number of circuit elements and improve speed, then the transistor density and operation speed are improved, but the strain in strain-creating elements relaxes leading to reduced charge carrier mobility
Solution Approach 1:
The strain-creating element is designed with a non-uniform composition distribution, where the concentration of the second material varies across different regions of the element. This local variation in composition creates different strain characteristics in different portions of the element, allowing the strain to be maintained effectively even in reduced channel length transistors.
Solution Approach 2:
The invention changes the compositional parameter of the strain-creating element by incorporating a gradient or varying concentration of the second material. This parameter change allows the strain-creating element to maintain effective strain in shorter channel lengths where conventional uniform composition elements would relax.
2Adaptability or versatility
If the channel length is reduced to enhance functionality, then the number of functional elements increases, but highly sophisticated dopant profiles and advanced photolithography techniques are required
Solution Approach 1:
By implementing a strain-creating element with non-uniform composition, the invention provides a localized strain enhancement that works effectively with reduced channel lengths without requiring complex dopant profiles or advanced photolithography techniques.
3Productivity
If the width of the channel region is reduced to increase transistor density, then the transistor density is improved, but the channel conductivity decreases
Solution Approach 1:
The non-uniform composition distribution in the strain-creating element provides localized strain enhancement in the channel region, compensating for the reduced channel width and maintaining channel conductivity despite higher transistor density.
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 maintains strain in the channel region, increasing the mobility of holes and electrons, and reducing the likelihood of crystal defects, thus improving the performance of field effect transistors.
Implementation Method 1
the lattice structure in the channel region may be modified by creating tensile or compressive strain. This leads to a modified mobility of electrons and holes, respectively.
Data Source
AI summary
A method of forming a field effect transistor comprises providing a semiconductor substrate, a gate electrode being formed over the semiconductor substrate. At least one cavity is formed adjacent the gate electrode. A strain-creating element is formed in the at least one cavity. The strain-creating element comprises a compound material comprising a first chemical element and a second chemical element. A first concentration ratio between a concentration of the first chemical element in a first portion of the strain-creating element and a concentration of the second chemical element in the first portion of the strain-creating element is different from a second concentration ratio between a concentration of the first chemical element in a second portion of the strain-creating element and a concentration of the second chemical element in the second strain-creating element.