Source/Drain Epitaxy With In-Situ PECVD for High Etch Selectivity
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Solution Overview
Problem
The increasing demand for smaller semiconductor devices poses challenges in forming source/drain (S/D) regions with high etch selectivity at low temperatures, as existing methods suffer from etch selectivity loss and require additional ex-situ etching processes to remove nodules and clogs from dielectric side surfaces.
Innovation Solution
The use of a plasma-enhanced chemical vapor deposition (PECVD) process at temperatures of about 500°C or below, with in-situ deposition and etching in the PECVD chamber, to form S/D regions with undoped or doped semiconductor materials, achieving etch selectivity greater than 6 and eliminating the need for additional ex-situ etching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional epitaxial processes are used to form S/D regions, then S/D regions can be formed, but etch selectivity is lost and additional ex-situ etching processes are required to remove nodules and clogs
Solution Approach 1:
The patent combines deposition and etching operations into a single in-situ process within the PECVD chamber. The plasma-enhanced chemical vapor deposition process simultaneously forms the epitaxial S/D regions and performs selective etching of nodules and clogs from dielectric side surfaces, eliminating the need for separate ex-situ etching steps while maintaining high etch selectivity
Solution Approach 2:
The patent utilizes plasma enhancement to change the physical and chemical parameters of the deposition process, enabling it to occur at lower temperatures (500°C or below) while achieving both high etch selectivity and complete nodule removal. The plasma provides the necessary energy to maintain etch selectivity at temperatures where conventional thermal processes would fail
2Productivity
If thermal CVD process is used for epitaxial growth, then S/D regions can be formed, but additional ex-situ etching is required due to etch selectivity loss
Solution Approach 1:
The patent merges the epitaxial growth and nodule removal operations into a single in-situ PECVD process step. By performing both functions simultaneously in the same chamber without intermediate handling, the process eliminates the time required for separate ex-situ etching steps while improving overall productivity
3Reliability
If high temperature process is used for epitaxial growth, then S/D regions with good quality can be formed, but process complexity increases and additional etching steps are needed
Solution Approach 1:
The patent changes the temperature parameter to 500°C or below, which is lower than conventional thermal CVD processes. The plasma enhancement compensates for the reduced thermal energy, enabling the formation of high-quality crystalline S/D regions with appropriate doping activation while simultaneously achieving selective etching of defects, thereby reducing process complexity
Solution Approach 2:
The patent replaces the purely thermal mechanism with a plasma-enhanced mechanism. The plasma provides the necessary energy and reactive species to enable epitaxial growth and selective etching at lower temperatures, substituting thermal activation with plasma-driven chemical reactions
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 the formation of S/D regions with improved qualities, such as lower resistivity, at lower temperatures, while preventing the formation of defective amorphous semiconductor regions and nodules on dielectric side surfaces, thus enhancing the overall efficiency and cost-effectiveness of the semiconductor fabrication process.
Implementation Method 1
The use of a plasma-enhanced chemical vapor deposition (PECVD) process at temperatures of about 500°C or below
Implementation Method 2
with in-situ deposition and etching in the PECVD chamber, to form S/D regions with undoped or doped semiconductor materials, achieving etch selectivity greater than 6
Data Source
AI summary
A method of forming source/drain regions of semiconductor devices is disclosed. The method includes forming a fin structure on a substrate, forming a polysilicon structure on the fin structure, removing a portion of the fin structure adjacent to the polysilicon structure to form an opening, and forming a S/D region in the opening. The forming the S/D region includes exposing the fin structure in the opening to a first flow rate of a precursor gas during a first phase of a gas flow cycle, a second flow rate of the precursor gas during a second phase of the gas flow cycle. The exposing the fin structure in the opening to the precursor gas, the etching gas, and the plasma is performed in an in-situ process.