L-Shaped Sidewall Spacer for Epitaxial Faceting Control
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Solution Overview
Problem
Achieving consistent faceting of epitaxial source/drain regions in semiconductor manufacturing is challenging due to variability in boron concentration and deposition pressure, leading to inconsistent performance across wafers and lots, and existing spacer formation processes fail to provide manufacturable solutions.
Innovation Solution
The use of an L-shaped sidewall spacer technique forces consistent faceting of epitaxial material adjacent to the gate structure, reducing gate-to-source/drain capacitance variability and improving yield by employing a bi-layer or tri-layer spacer stack with sacrificial materials and selective etching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing spacer formation processes are used, then manufacturing is simpler, but faceting consistency and performance reliability deteriorate due to extreme variability within wafer, wafer-to-wafer, and lot-to-lot
Solution Approach 1:
The spacer formation process is segmented into multiple distinct steps: forming a first spacer layer, forming a second spacer layer, and selectively removing portions. This segmentation allows each layer to serve a specific function - the first spacer layer provides the primary spacer structure while the second spacer layer enables precise control of the facet geometry through selective removal, thereby achieving consistent faceting across wafers and lots
Solution Approach 2:
The first spacer layer is formed in advance before the second spacer layer. This preliminary action establishes a foundation structure that guides the subsequent formation of the final spacer geometry. The pre-formed first spacer layer ensures that when the second layer is selectively removed, the resulting facet structure is consistent and reproducible across different manufacturing batches
2Manufacturing precision
If boron concentration and deposition pressure are balanced to achieve consistent facets, then faceting consistency improves, but manufacturability deteriorates due to unrealistic balance requirements that vary drastically across pitch, density and epi tools
Solution Approach 1:
The invention changes the controlling parameters from material deposition parameters (boron concentration, deposition pressure) to structural geometry parameters (spacer layer thicknesses, pattern dimensions). By controlling the thickness of the first and second spacer layers through standard lithography and deposition processes, consistent facet geometry is achieved without requiring unrealistic balances of epi deposition parameters that vary across different tools and conditions
3Reliability
If conventional epi processes are used, then process simplicity is maintained, but performance consistency deteriorates due to extreme variability in faceting across chip-to-chip, wafer-to-wafer, and lot-to-lot
Solution Approach 1:
The bi-layer spacer structure acts as an intermediary element that mediates between the gate structure and the epitaxial source/drain regions. The spacers control the facet geometry of the epi regions through their geometric configuration rather than through material composition control. This intermediary structure enables consistent performance across chips and wafers by decoupling the facet formation process from the epi deposition process, making the system less sensitive to variability in epi tool conditions
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 L-shaped spacer technique ensures consistent faceting across wafers and lots, reduces capacitance variability, and enhances manufacturing consistency, improving chip-to-chip performance and yield in semiconductor production.
Implementation Method 1
faceted epitaxial source/drain regions
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to faceted epitaxial source/drain regions and methods of manufacture. The structure includes: a gate structure over a substrate; an L-shaped sidewall spacer located on sidewalls of the gate structure and extending over the substrate adjacent to the gate structure; and faceted diffusion regions on the substrate, adjacent to the L-shaped sidewall spacer.