Selective Silicide Formation on Epitaxial Germanium
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Solution Overview
Problem
Conventional silicide formation methods, particularly for titanium silicide in semiconductor devices, face challenges such as lack of selectivity at temperatures below 800°C, poor conformality, and incompatibility with advanced node contact structures, necessitating improved methods for selective and efficient silicide formation.
Innovation Solution
The method involves performing a contact trench etching and cleaning process, followed by epitaxial germanium deposition on source/drain regions, and then exposing the germanium to titanium and silicon precursors at temperatures below 550°C to form a silicide alloy with desirable resistivity properties, eliminating the need for pre-amorphization implantation and post-annealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional CVD of titanium silicide is performed at temperatures below 800°C, then the process is compatible with thermal budgets for advanced node contact structures, but the process lacks selectivity
Solution Approach 1:
An epitaxial germanium layer is deposited on the source/drain regions before the silicide formation process. This preliminary germanium layer enables selective reaction with titanium precursors at lower temperatures (below 800°C), as the germanium-silicon alloy forms a eutectic composition that reacts more selectively than conventional silicon alone, thereby resolving the contradiction between low temperature compatibility and process selectivity
Solution Approach 2:
The invention changes the material composition parameter by introducing germanium into the silicon matrix, creating a germanium-silicon alloy with specific eutectic composition. This parameter change enables the silicide formation to proceed selectively at lower temperatures, simultaneously achieving both thermal budget compatibility and improved selectivity
2Manufacturing precision
If conventional silicide formation is performed, then silicide contacts are formed, but conformality is less than desirable
Solution Approach 1:
The epitaxial germanium deposition is performed as a preliminary step before silicide formation. This pre-deposited germanium layer ensures uniform coverage and reactive sites across the source/drain regions, enabling conformal silicide formation without requiring complex post-deposition annealing processes, thus improving conformality while maintaining manufacturing simplicity
Solution Approach 2:
The germanium layer acts as an intermediary material between the silicon source/drain regions and the titanium precursors. This intermediary layer provides uniform reaction sites and controls the silicide formation kinetics, resulting in improved conformality without increasing process complexity
3Reliability
If post deposition anneal is utilized to form low resistivity phase silicides, then contact resistance is improved, but the process becomes time consuming and incompatible with thermal budgets
Solution Approach 1:
By changing the material composition to include germanium in eutectic composition with silicon, the silicide formation process achieves low resistivity phase formation directly during the deposition step without requiring subsequent annealing. The eutectic composition enables lower formation temperature and eliminates the need for time-consuming post-deposition annealing, reducing both process time and thermal budget consumption while maintaining low contact resistance
Solution Approach 2:
The invention extracts and eliminates the post-deposition annealing step from the conventional silicide formation process. By using epitaxial germanium deposition followed by direct silicide formation at lower temperatures, the process achieves the same low resistivity result without the separate annealing step, thereby reducing process time and improving compatibility with thermal budgets
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 selective silicide formation with improved contact resistance and conformality, suitable for advanced contact integration schemes, reducing pinhole density and enhancing thermal stability and uniformity across the source/drain regions.
Implementation Method 1
An epitaxial germanium deposition is performed on the S/D regions
Implementation Method 2
A thermal chemical vapor deposition silicide formation process is performed on the S/D regions by exposing the epitaxially deposited germanium to a titanium containing precursor and a silicon containing precursor
Data Source
AI summary
Methods for selective silicide formation are described herein. The methods are generally utilized in conjunction with contact structure integration schemes and provide for improved silicide formation characteristics. In one implementation, a silicide material is selectively formed on source/drain (S/D) regions at a temperature less than about 550° C. The resulting silicide is believed to exhibit desirable contact resistance and applicability in advanced contact integration schemes.