Boron-Doped Si Cap Layer for Strained SiGe Substrates
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High Ge concentration in epitaxial SiGe layers of semiconductor devices leads to strain relaxation and wavy top surfaces, negatively impacting device performance and subsequent manufacturing processes.
Innovation Solution
A manufacturing method involving a boron-doped Si cap layer formed on an epitaxial structure with a high Ge concentration, which reduces strain relaxation and maintains a flat surface, enhancing device performance and manufacturing process efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Ge concentration in the epitaxial SiGe layer is increased to improve device performance, then the strain stress is increased, but strain relaxation and wavy top surface occur
Solution Approach 1:
The patent applies parameter changes by doping the cap layer with boron to alter its physical properties. The boron concentration in the cap layer is specifically controlled to be higher than 5×10^20 atoms/cm³, which changes the stress characteristics of the cap layer and enables it to compensate for strain relaxation in the high-Ge-content epitaxial SiGe layer, thereby maintaining both high device performance and structural stability
Solution Approach 2:
The patent creates a composite structure consisting of the epitaxial SiGe layer with high Ge concentration (≥45%) and a boron-doped cap layer. This composite material system combines the high strain stress benefit of high-Ge SiGe with the strain relaxation compensation capability of the boron-doped cap layer, resolving the contradiction between performance improvement and structural stability
2Reliability
If the Ge concentration in the epitaxial SiGe layer is increased to improve device performance, then the strain stress is increased, but the top surface becomes wavy
Solution Approach 1:
The patent changes the chemical composition parameter of the cap layer by introducing boron doping with concentration higher than 5×10^20 atoms/cm³. This parameter change modifies the stress state of the cap layer, enabling it to counteract the forces causing surface waviness and maintain a flat top surface even when the underlying epitaxial SiGe layer has high Ge concentration
Solution Approach 2:
The boron-doped cap layer serves as a preliminary countermeasure against surface waviness. By pre-establishing a cap layer with controlled boron concentration before subsequent processing steps, the patent proactively prevents top surface deformation that would otherwise occur due to the high Ge concentration in the epitaxial SiGe layer
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
The method effectively reduces strain relaxation by 33% to 5% and ensures a flat top surface, improving device performance and facilitating subsequent processes by maintaining superior electrical properties and preventing agglomeration.
Implementation Method 1
the strain stress generated to the channel region of the semiconductor device, such as a metal-oxide semiconductor (MOS) transistor device, may efficiently improve the device performance
Implementation Method 2
the first cap layer is doped with boron for forming a flat top surface of the first cap layer
Data Source
AI summary
A manufacturing method of a semiconductor device is provided. The method includes at least the following steps. A gate structure is formed on a substrate. An epitaxial structure is formed on the substrate, wherein the epitaxial structure comprises SiGe, and the Ge concentration in the epitaxial structure is equal to or higher than 45%. A first cap layer is formed on the epitaxial structure, wherein the first cap layer comprises Si. The first cap layer is doped with boron for forming a flat top surface of the first cap layer.