Carbon-Containing Silicon Germanium Cap Layer for Transistor Reliability
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Solution Overview
Problem
In semiconductor manufacturing, germanium in epitaxial layers tends to precipitate to the surface during subsequent processes, leading to the formation of black spots and degradation of transistor performance.
Innovation Solution
A carbon-containing silicon germanium cap layer is formed on the epitaxial layer using an in-situ epitaxial process or by doping carbon into a silicon germanium cap layer, preventing germanium diffusion and reducing tensile stresses on the gate channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon germanium cap layer is formed on the epitaxial layer, then germanium diffusion is prevented, but germanium precipitates to the surface forming black spots
Solution Approach 1:
The patent changes the chemical composition parameter of the cap layer by introducing carbon elements to form a carbon-containing silicon germanium cap layer. This parameter change prevents germanium precipitation while maintaining diffusion barrier functionality, thereby resolving the contradiction between reliability and manufacturing precision
Solution Approach 2:
The patent creates a composite material structure by combining carbon, silicon, and germanium elements in the cap layer. This composite carbon-containing silicon germanium material exhibits improved properties where carbon prevents germanium precipitation, thus maintaining both surface quality and transistor performance
2Manufacturing precision
If carbon is doped into the silicon germanium cap layer, then germanium precipitation is prevented, but the process complexity increases
Solution Approach 1:
The patent applies preliminary action by incorporating carbon elements during the in-situ epitaxial growth process itself, rather than requiring separate post-processing doping steps. This preliminary incorporation of carbon prevents germanium precipitation while maintaining process efficiency and reducing overall process complexity
3Speed
If the epitaxial layer is grown to improve transistor speed, then carrier mobility increases, but germanium diffuses easily and pollutes peripheries
Solution Approach 1:
The patent introduces a carbon-containing silicon germanium cap layer as an intermediary between the epitaxial layer and the environment. This intermediary layer acts as a barrier that prevents germanium diffusion and pollution while allowing the underlying epitaxial layer to maintain its high-speed performance characteristics
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 prevents the formation of black spots on the surface and maintains the compressive stresses induced by the epitaxial layer, enhancing transistor performance by controlling germanium diffusion and adjusting carbon content gradients.
Implementation Method 1
forms a carbon-containing silicon germanium cap layer on an epitaxial layer, to prevent germanium in the epitaxial layer or in the cap layer from precipitating to the surface of the cap layer
Implementation Method 2
An in-situ epitaxial process is performed to form a carbon-containing silicon germanium cap layer on the epitaxial layer
Data Source
AI summary
A semiconductor structure includes a gate structure, an epitaxial layer and a carbon-containing silicon germanium cap layer. The gate structure is located on a substrate. The epitaxial layer is located in the substrate beside the gate structure. The carbon-containing silicon germanium cap layer is located on the epitaxial layer. Otherwise, semiconductor processes for forming said semiconductor structure are also provided.