FinFET Epitaxial Source/Drain Profile Control
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Solution Overview
Problem
As semiconductor devices continue to shrink in feature size, the integration density of electronic components increases, but this leads to challenges such as increased gate-to-source/drain capacitance in FinFETs, which affects performance and efficiency.
Innovation Solution
The formation of epitaxial source/drain regions with varying flow-rate ratios of semiconductor material precursors during epitaxial growth processes, adjusting the gas-phase chlorine atoms introduction to achieve a taller and slimmer profile, thereby reducing gate-to-source/drain capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the minimum feature size is reduced to increase integration density, then more components can be integrated into a given area, but gate-to-source/drain capacitance increases adversely affecting performance
Solution Approach 1:
The patent applies local quality by creating epitaxial source/drain regions with varying doping concentrations at different locations. The regions adjacent to the channel have lower doping concentrations, while regions farther away have higher doping concentrations, optimizing the electrical characteristics locally to reduce capacitance while maintaining overall device functionality
Solution Approach 2:
The patent changes the doping concentration parameter through multi-stage epitaxial growth processes. By controlling the flow rates of dopant precursors at different growth stages, the patent creates a gradient doping profile that reduces gate-to-source/drain capacitance while maintaining the scaled dimensions required for high integration density
2Ease of manufacture
If epitaxial growth is performed with constant precursor flow rates, then the process is simple to control, but the resulting source/drain regions have suboptimal shape and adhesion
Solution Approach 1:
The patent applies dynamics by transitioning from static, constant flow rate epitaxial growth to dynamic, time-varying flow rate profiles. The precursor flow rates are modulated during different stages of epitaxial growth to achieve optimal source/drain region shape and adhesion properties, with higher dopant flow rates initially and lower flow rates later in the growth process
Solution Approach 2:
The patent applies preliminary action by performing a first epitaxial growth stage with specific dopant concentrations before performing a second growth stage with different dopant concentrations. This preliminary doping establishes a foundation that improves subsequent growth quality and adhesion, preparing the structure for optimal final properties
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 results in a decreased gate-to-source/drain capacitance, enhancing the performance of FinFETs by optimizing the shape and adhesion of epitaxial source/drain regions, which is particularly beneficial for applications like ring oscillators.
Implementation Method 1
forming an epitaxial source/drain region in the recess, the forming including: growing a first layer lining sides and a bottom of the recess; and after growing the first layer, growing a second layer on the first layer
Implementation Method 2
growing a first layer lining sides and a bottom of the recess by dispensing silane, dichlorosilane, trichlorosilane, and hydrochloric acid in the recess
Data Source
AI summary
In an embodiment, a method includes: forming a first gate stack and a second gate stack on a fin; etching the fin to form a recess in the fin between the first gate stack and the second gate stack; forming an epitaxial source/drain region in the recess, the forming including: forming a first layer lining sides and a bottom of the recess by dispensing silane, dichlorosilane, trichlorosilane, and hydrochloric acid in the recess; and after forming the first layer, forming a second layer on the first layer by dispensing the silane, dichlorosilane, trichlorosilane, and hydrochloric acid in the recess, where each of the silane, dichlorosilane, trichlorosilane, and hydrochloric acid are dispensed at a first flow rate when forming the first layer and at a second flow rate when forming the second layer.