Source/Drain Recess Surface Treatment for FinFET Epitaxy
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Solution Overview
Problem
The semiconductor industry faces challenges in forming high-quality epitaxial source/drain regions in FinFETs due to rough recess surfaces, which affect device performance and yield, particularly in reducing leakage current and improving current drive efficiency.
Innovation Solution
A high temperature process in a modified processing chamber to smooth the recess surfaces, combined with a hydrogen radical treatment to prevent re-oxidation and enhance cleaning efficiency, allowing for better epitaxial growth of source/drain regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching processes are used to form source/drain recesses, then the manufacturing process is simple, but the recess surfaces are rough which degrades epitaxial growth quality
Solution Approach 1:
The patent applies preliminary action by performing surface smoothing and cleaning treatments on the recess surfaces before epitaxial growth. Specifically, the method includes forming a liner layer over the rough recess surfaces, performing chemical-mechanical polishing (CMP) to smooth the surfaces, and conducting hydrogen plasma treatment to clean and activate the surfaces. These preparatory steps are executed prior to the epitaxial growth process to ensure high-quality surfaces for subsequent material deposition, directly resolving the contradiction between manufacturing simplicity and epitaxial quality.
2Manufacturing precision
If high temperature processing is applied to smooth recess surfaces, then surface quality improves, but re-oxidation occurs during processing
Solution Approach 1:
The patent employs inert atmosphere by conducting the high-temperature surface smoothing process in a nitrogen-filled environment. The method specifies heating the recess surfaces to temperatures between 400°C and 700°C in a nitrogen atmosphere, which prevents re-oxidation of the semiconductor surfaces during thermal processing. This inert environment maintains surface quality by eliminating oxygen exposure while allowing the necessary thermal smoothing to occur, directly addressing the contradiction between surface smoothness improvement and re-oxidation prevention.
Solution Approach 2:
The patent uses a liner layer as an intermediary protective barrier during processing. The liner layer is formed over the recess surfaces before high-temperature treatment and serves as a protective intermediary that prevents direct exposure to oxidizing environments while allowing thermal energy to pass through for surface smoothing. This intermediary layer resolves the contradiction by enabling high-temperature processing without causing re-oxidation.
3Manufacturing precision
If conventional cleaning methods are used, then the process is simple, but cleaning efficiency is insufficient to achieve optimal epitaxial growth
Solution Approach 1:
The patent applies parameter changes by utilizing hydrogen plasma treatment to fundamentally alter the cleaning mechanism and surface state. The method includes exposing the recess surfaces to hydrogen plasma, which chemically reacts with surface contaminants and oxides to form volatile compounds that are removed during the plasma process. This parameter change from conventional mechanical or chemical cleaning to plasma-based cleaning dramatically improves surface cleanliness and activates the surfaces for better epitaxial growth, justifying the increased process complexity.
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 solution increases the ratio of drive current to leakage current by 3% to 4%, boosts Ion performance, and expands the yield window for contact landing, resulting in improved device efficiency and yield.
Implementation Method 1
The source/drain recess is heated at a temperature greater than 700° C. for a time period of 1 minute to 30 minutes, thereby smoothing a surface of the source/drain recess by 6% to 12%
Implementation Method 2
a hydrogen radical treatment to prevent re-oxidation and enhance cleaning efficiency
Data Source
AI summary
Embodiments provide a way of treating source/drain recesses with a high heat treatment and an optional hydrogen plasma treatment. The high heat treatment smooths the surfaces inside the recesses and remove oxides and etching byproducts. The hydrogen plasma treatment enlarges the recesses vertically and horizontally and inhibits further oxidation of the surfaces in the recesses.