Threshold Alloy Thickness Uniformity via Plasma Etch
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Solution Overview
Problem
The manufacturing sequence for providing threshold adjusting semiconductor alloys in advanced integrated circuits leads to significant threshold variability across active regions due to non-uniform growth rates during epitaxial growth, affecting transistor performance and compatibility with performance requirements.
Innovation Solution
Enhancing the surface topography of active semiconductor regions before selective epitaxial growth by controlled material removal, such as using plasma-assisted etch recipes to reduce growth rate variability and achieve uniformity in the thickness of the threshold adjusting semiconductor alloy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If selective epitaxial growth is performed on active regions with existing surface topography variations, then transistor threshold voltage adjustment is achieved, but significant threshold variability occurs across active regions due to non-uniform growth rates
Solution Approach 1:
The patent applies preliminary planarization by performing controlled material removal (recessing) on the active regions before the selective epitaxial growth process. This preliminary action creates a uniform starting surface topography, which eliminates the non-uniform growth rates that would otherwise occur during epitaxial growth. By preparing the surface in advance, the subsequent threshold adjusting alloy deposition achieves uniform thickness and consistent threshold voltage across all active regions.
2Manufacturing precision
If material removal is performed to enhance surface topography uniformity, then epitaxial growth uniformity improves, but additional process steps are required
Solution Approach 1:
The patent merges the surface planarization step with the existing masking and patterning processes. The material removal is performed through the previously formed mask layer, combining multiple functions (pattern definition, surface preparation, and selective exposure) into an integrated process sequence. This merging approach achieves the necessary surface uniformity while minimizing the addition of separate, standalone process steps.
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 significantly reduces threshold variability, ensuring consistent transistor characteristics and improved compatibility with sophisticated semiconductor device performance requirements by enhancing the uniformity of the epitaxial growth process.
Implementation Method 1
using plasma-assisted etch recipes to reduce growth rate variability
Implementation Method 2
a threshold adjusting semiconductor alloy is selectively formed on the recessed first silicon-containing crystalline semiconductor region
Data Source
AI summary
The growth rate in a selective epitaxial growth process for depositing a threshold adjusting semiconductor alloy, such as a silicon/germanium alloy, may be enhanced by performing a plasma-assisted etch process prior to performing the selective epitaxial growth process. For example, a mask layer may be patterned on the basis of the plasma-assisted etch process, thereby simultaneously providing superior device topography during the subsequent growth process. Hence, the threshold adjusting material may be deposited with enhanced thickness uniformity, thereby reducing overall threshold variability.