SiGe Source/Drain Structure Without Inner Spacers for Mobility
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Solution Overview
Problem
The presence of inner spacers between the gate structure and source/drain patterns in semiconductor devices, particularly in nanosheet transistors, affects device performance by causing crystal defects and reducing the effectiveness of compressive stress on channel layers, thereby impairing mobility and overall device performance.
Innovation Solution
The semiconductor device is manufactured without inner spacers, with source/drain patterns having varying germanium concentrations, allowing epitaxial growth from channel structures, thereby eliminating crystal defects and enhancing mobility through the use of silicon germanium (SiGe) to apply appropriate stress to the channel layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inner spacers are formed between gate structure and source/drain pattern, then isolation and protection are improved, but crystal defects increase and mobility decreases
Solution Approach 1:
The patent removes the inner spacer structure entirely from the device architecture. By extracting this problematic component, the invention eliminates the source of crystal defects and mobility degradation while maintaining device functionality through alternative design approaches.
Solution Approach 2:
The source/drain pattern is merged directly with the channel structure without intervening spacer layers. This direct integration eliminates the harmful interface between inner spacers and source/drain patterns, preventing crystal defects while maintaining proper electrical isolation through the gate structure itself.
2Loss of energy
If inner spacers are formed between gate structure and source/drain pattern, then parasitic capacitance is reduced, but compressive stress effectiveness on channel layers decreases
Solution Approach 1:
The inner spacer is removed to eliminate the barrier that prevents effective stress transmission. Without the spacer, compressive stress from the source/drain pattern can be directly applied to the channel layers, improving carrier mobility while energy loss from parasitic capacitance is managed through gate structure design.
Solution Approach 2:
The source/drain pattern is designed with differentiated germanium concentrations in specific regions to provide localized compressive stress where needed. This local optimization of material composition enables effective stress application to the channel without requiring inner spacers.
3Manufacturing precision
If source/drain pattern is grown without inner spacers, then crystal defects are eliminated and mobility is enhanced, but manufacturing complexity increases
Solution Approach 1:
The source/drain pattern employs spatially varying germanium concentrations with different compositions in different regions. This local quality variation enables direct growth from the channel structure without inner spacers, improving crystal quality while the gradient design simplifies the manufacturing process by eliminating spacer formation steps.
Solution Approach 2:
The germanium concentration parameter is varied continuously or in steps across the source/drain pattern structure. This parameter change enables direct epitaxial growth from the channel with improved crystal quality, and the controlled gradient simplifies manufacturing by replacing multi-step spacer processes with a single variable-composition growth step.
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 improves device performance by preventing crystal defects and increasing the contact area between channel layers and source/drain patterns, thereby enhancing hole and electron mobility, respectively, without the need for inner spacers.
Implementation Method 1
source/drain patterns having varying germanium concentrations, allowing epitaxial growth from channel structures
Implementation Method 2
use of silicon germanium (SiGe) to apply appropriate stress to the channel layers
Data Source
Figure 1
Figure 2A~2B
Figure 2C
AI summary
Provided is a semiconductor device which includes: a channel structure; a source/drain pattern on the channel structure; a gate structure on the channel structure; and a contact layer on the channel structure, wherein the contact layer contacts the source/drain pattern and includes silicon germanium (SiGe), the source/drain pattern includes a 1st portion and a 2nd portion between the 1st portion and the contact layer, the 1st portion and the 2nd portion have different germanium (Ge) concentrations, and a Ge concentraiotn in the contact layer is higher than a Ge concentration of the 1st portion and lower than a Ge concentration of the 1st portion.