SiGe Regrowth Region for PMOS Carrier Mobility
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Solution Overview
Problem
Conventional epitaxial methods struggle to achieve high Ge concentration in SiGe films for PMOS devices, limiting strain and performance due to sensitivity to surface preparation and growth conditions, making it challenging to meet increasing Ge concentration requirements and maintain proper SiGe profile control.
Innovation Solution
The semiconductor structure involves regrown source/drain regions with predetermined dimensions and lattice constants, optimized geometric shapes, and controlled doping to enhance carrier mobility and reduce threshold voltage variation, using techniques like selective epitaxial growth and ion implantation to form recesses and adjust Ge concentration profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional epitaxial methods are used to grow SiGe film, then the process is sensitive to surface preparation and growth conditions, but achieving high Ge concentration becomes extremely difficult
Solution Approach 1:
The patent performs preliminary actions by forming a mandrel structure and defining a recess region before attempting SiGe growth. This pre-structured approach allows subsequent selective epitaxial growth to occur only in the predefined recess area, making the process less sensitive to overall surface conditions while enabling better Ge concentration control in the target region.
Solution Approach 2:
The patent applies local quality by creating a recess with specific geometric characteristics (depth, width, aspect ratio) that are optimized for SiGe growth. The selective epitaxial growth is confined to this localized region, allowing different Ge concentrations to be achieved in specific areas while maintaining control over the overall device structure.
2Reliability
If higher Ge concentration is used in SiGe film, then strain and carrier mobility are enhanced, but it becomes challenging to maintain proper SiGe profile control
Solution Approach 1:
The patent changes key parameters including recess depth (5-50 nm), recess width (20-200 nm), and aspect ratio (0.1-2.5) to optimize SiGe profile control. By adjusting these geometric parameters along with growth temperature and pressure, the method achieves better control over Ge concentration profiles while maintaining the desired strain and carrier mobility enhancement.
Solution Approach 2:
The patent employs feedback mechanisms through in-situ monitoring during selective epitaxial growth. The growth process is controlled based on real-time measurements of layer thickness and composition, allowing dynamic adjustment of growth conditions to maintain proper SiGe profile control even at high Ge concentrations.
3Reliability
If selective epitaxial growth is used to form SiGe in undercut regions, then PMOS strain is achieved, but very high Ge concentration SiGe film is difficult to realize
Solution Approach 1:
The patent transitions from planar undercut growth to vertical recess growth by defining three-dimensional recess structures with controlled depth and width. This dimensional change allows the SiGe film to grow vertically into the recess, enabling much higher Ge concentrations (up to 70-80%) to be achieved while maintaining the strain necessary for PMOS performance enhancement.
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 higher carrier mobility, increased drive current, and reduced threshold voltage variation among transistors, achieving better device performance by optimizing regrowth region dimensions and doping profiles.
Implementation Method 1
The larger lattice constant of the SiGe film provides the uniaxial strain to the Si channel
Implementation Method 2
One of the most widely used methods is chemical vapor deposition ('CVD'), in which atoms or molecules contained in a vapor deposit on a surface to form a film
Implementation Method 3
CVD allows for the growth of films on device surface areas, including 'epitaxial' films comprised of a crystalline silicon-containing material
Data Source
AI summary
Some embodiments of the present disclosure provide a semiconductor structure, including a substrate and a regrowth region. The substrate is made of a first material with a first lattice constant, and the regrowth region is made of the first material and a second material, having a lattice constant different from the first lattice constant. The regrowth region is partially positioned in the substrate. The regrowth region has a “tip depth” measured vertically from a surface of the substrate to a widest vertex of the regrowth region, and the tip depth being less than 10 nm. The regrowth region further includes a top layer substantially made of the first material, and the top layer has substantially the first lattice constant.