Selective Epitaxial Growth of Silicon-Germanium Source-Drain Layers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for manufacturing fin-type field effect transistors (finFETs) face challenges in forming source/drain layers with precise geometry and composition, particularly in achieving a smooth, conformal growth and etching of silicon-germanium layers to fill trenches between gate structures, which affects device performance.
Innovation Solution
A method involving selective epitaxial growth (SEG) using a combination of silicon and germanium source gases, etching gases, and carrier gases, with controlled ratios and temperatures, to form multiple layers of silicon-germanium with varying germanium and boron content, followed by purging to etch and shape the layers, ensuring a pentagon or hexagon cross-section and a flat top surface, and repeated growth and etching cycles to fill the trench.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If selective epitaxial growth is used to form silicon-germanium layers in the trench, then the germanium content and conformal shape are improved, but the process complexity and manufacturing precision requirements increase
Solution Approach 1:
The source/drain layer is formed through multiple sequential SEG steps with different gas compositions and parameters. Each step deposits a portion of the required thickness with specific germanium content, allowing precise control of the overall layer composition and shape. The trench is filled in stages rather than a single step, enabling better shape control.
Solution Approach 2:
The manufacturing process employs periodic alternation between SEG growth steps and etching steps. This periodic action allows the silicon-germanium layer to be grown and then selectively removed to achieve the desired conformal shape and germanium distribution. The cycle of growth and removal is repeated multiple times to build up the final structure.
2Stability of the object's composition
If multiple SEG steps with varying gas ratios are performed, then the germanium content distribution is improved, but the processing time and energy consumption increase
Solution Approach 1:
The process dynamically changes gas flow ratios, temperatures, and pressure conditions between SEG steps to control germanium incorporation. By adjusting these parameters systematically across multiple steps, the desired germanium content distribution is achieved while attempting to minimize total processing time through optimized parameter transitions.
Solution Approach 2:
The multiple SEG and etching steps are performed in continuous sequence without interrupting the chamber vacuum or removing the substrate. The process maintains continuous useful action by keeping the chamber sealed and proceeding through all deposition and etching operations in an uninterrupted manner, reducing time loss from chamber cycling.
3Manufacturing precision
If the trench is completely filled with silicon-germanium layer, then the source/drain layer geometry is improved, but the etching selectivity and layer uniformity become more difficult to control
Solution Approach 1:
The process uses monitored control of gas flow ratios and deposition rates during each SEG step to ensure uniform layer formation. By maintaining consistent process parameters and monitoring deposition characteristics, the system achieves reliable trench filling while controlling the uniformity of germanium distribution throughout the layer.
Solution Approach 2:
The segmented approach allows different regions of the trench to receive different amounts of germanium incorporation based on local conditions. Areas with better gas access receive higher germanium content while maintaining overall trench filling, achieving local optimization of composition and shape control simultaneously.
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 source/drain layers with a smooth, conformal shape and high germanium content, reducing facet defects and ensuring complete trench filling, thereby enhancing the performance and reliability of finFETs.
Implementation Method 1
perform a selective epitaxial growth (SEG) process using a top surface of the active fin exposed by the trench as a seed so that a silicon-germanium layer is grown
Implementation Method 2
purging the chamber by providing the carrier gas into the chamber to etch the silicon-germanium layer
Data Source
AI summary
A method of manufacturing a semiconductor device includes partially removing an upper portion of an active fin of a substrate loaded in a chamber to form a trench; and forming a source/drain layer in the trench, which includes providing a silicon source gas, a germanium source gas, an etching gas and a carrier gas into the chamber to perform a selective epitaxial growth (SEG) process using a top surface of the active fin exposed by the trench as a seed so that a silicon-germanium layer is grown; and purging the chamber by providing the carrier gas into the chamber to etch the silicon-germanium layer.