Selective Epitaxial Source/Drain Deposition for Low-Temperature hGAA
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Solution Overview
Problem
Conventional methods for forming n-channel metal oxide semiconductor (NMOS) source/drain regions in horizontal gate-all-around (hGAA) device structures face challenges such as precursor incompatibility, selectivity loss, and increased dopant diffusion at higher temperatures, leading to higher production costs and parasitic capacitance.
Innovation Solution
A method involving the use of a chlorinated silicon precursor, an antimony-containing precursor, and a phosphorous-containing precursor is employed to form epitaxial source/drain regions at temperatures below 550°C, with co-flowing these precursors during epitaxial deposition to enhance selectivity and growth rate, while maintaining low temperature processing and reducing faceting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional approaches are used to form NMOS source/drain regions at low temperatures, then temperature is reduced, but precursor incompatibility and selectivity loss occur
Solution Approach 1:
The patent changes the chemical parameters of the precursor system by using a chlorinated silicon precursor combined with antimony and phosphorous dopant precursors. This parameter change enables low-temperature deposition while maintaining precursor compatibility and selectivity, as the chlorinated silicon precursor system is specifically optimized to work with these dopants at temperatures below 550°C
Solution Approach 2:
The patent employs a composite precursor system consisting of chlorinated silicon precursor, antimony-containing precursor, and phosphorous dopant precursor flowing together. This composite approach allows multiple functions (silicon deposition, doping, and selectivity maintenance) to be achieved simultaneously, resolving the contradiction between low temperature and precursor compatibility
2Manufacturing precision
If separate etching and deposition steps are used, then process control is improved, but device production cost increases
Solution Approach 1:
The patent merges the etching and deposition steps into a single unified process. The chlorinated silicon precursor system performs both functions: it deposits silicon while simultaneously etching non-crystalline materials through the chlorine component. This consolidation maintains precise process control while reducing the number of separate steps and associated costs
3Productivity
If temperature is increased to form NMOS source/drain regions, then deposition rate is improved, but dopant diffusion increases and ramp times increase
Solution Approach 1:
The patent changes the chemical composition parameters of the precursor system to enable low-temperature deposition with high effectiveness. The chlorinated silicon precursor combined with antimony and phosphorous dopants allows sufficient deposition rate at temperatures below 550°C, preventing dopant diffusion while maintaining productivity
Solution Approach 2:
The patent replaces the thermal mechanism (relying on high temperature to drive deposition) with a chemical mechanism (using reactive precursors that deposit at low temperatures). The chlorinated silicon system provides chemically-driven deposition that does not require high thermal energy, thus avoiding dopant diffusion while maintaining deposition rate
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 high-concentration antimony-doped source/drain regions with improved adhesion and growth rates, reducing parasitic capacitance and dopant migration, thus enhancing the performance and efficiency of hGAA device structures.
Implementation Method 1
flowing a chlorinated silicon containing precursor, co-flowing an antimony-containing precursor with the chlorinated silicon containing precursor, co-flowing an n-type dopant precursor with the chlorinated silicon containing precursor and the antimony-containing precursor
Implementation Method 2
heating the substrate to a temperature of less than about 550° C.
Implementation Method 3
The source region and the drain region are selectively formed on the crystalline first layers of the substrate, wherein the formed source region and drain region contain an antimony concentration of greater than about 5×1020 atoms/cm3
Data Source
AI summary
A method for the selective formation of epitaxial layers is described herein. In the method, epitaxial layers are deposited to form source and drain regions around a horizontal gate all around (hGAA structure). The method includes co-flowing a combination of chlorinated silicon containing precursors, antimony containing precursors, and n-type dopant precursors. The resulting source and drain regions are selectively grown from crystalline nanosheets or nanowires of the hGAA structure over the non-crystalline gate structure and dielectric layers. The source and drain regions are predominantly grown in a <110> direction.