Source Drain Etch Stop Layer for Transistor Depth Control
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Solution Overview
Problem
Current transistor architectures face challenges in controlling the source and drain etch process for stacked gate-all-around transistor structures, leading to uncontrollable exposure of the substrate layer and increased leakage paths due to the lack of selectivity between channel and substrate materials.
Innovation Solution
A buried monocrystalline source and drain etch stop layer with a different chemical composition than the channel and substrate materials is introduced, which prevents the etch process from advancing into the substrate and acts as a diffusion barrier, ensuring precise control over the source and drain material depth and reducing leakage paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the source and drain etch process is performed to remove semiconductor material layers, then the source and drain materials can be formed, but the etch process cannot be precisely controlled and may expose the substrate layer
Solution Approach 1:
An etch stop layer is formed between the channel layer and the substrate layer before the source and drain material formation. This preliminary structure prevents the etch process from advancing into the substrate, ensuring precise depth control without exposing the substrate layer.
Solution Approach 2:
The etch stop layer acts as an intermediary layer between the channel layer and the substrate layer. It provides a selective stopping point for the etch process, allowing precise control of etch depth while preventing substrate exposure.
2Ease of manufacture
If the source and drain etch process is performed without selective control, then the etch can proceed freely, but leakage paths increase due to uncontrollable substrate exposure
Solution Approach 1:
The etch stop layer serves as a mediator that provides selective stopping for the etch process. This allows the etch to proceed freely through the channel layer while being automatically stopped at the etch stop layer, preventing substrate exposure and reducing leakage current without complicating the manufacturing process.
3Device complexity
If no etch stop layer is used, then the fabrication process is simpler, but the control of source and drain material depth is poor
Solution Approach 1:
The etch stop layer is formed in advance between the channel layer and substrate layer. This preliminary structure provides a predetermined stopping point for the etch process, enabling precise control of source and drain material depth without significantly increasing fabrication process complexity.
4Loss of substance
If the etch process advances into the substrate layer, then more material is removed, but leakage paths are created between source and drain
Solution Approach 1:
The etch stop layer acts as an intermediary barrier that allows controlled material removal through the channel layer while preventing further advancement into the substrate layer. This selective stopping mechanism removes necessary material for source and drain formation while preventing the creation of leakage paths.
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 solution effectively controls the depth of the source and drain materials, preventing substrate exposure and reducing leakage currents, thereby enhancing transistor performance and yield by providing a precise etch stop and diffusion barrier.
Implementation Method 1
A buried monocrystalline source and drain etch stop layer with a different chemical composition than the channel and substrate materials is introduced, which prevents the etch process from advancing into the substrate
Implementation Method 2
acts as a diffusion barrier, ensuring precise control over the source and drain material depth and reducing leakage paths
Data Source
Figure 1
Figure 2A~2D
Figure 3
AI summary
Integrated circuitry comprising transistor structures with a source/drain etch stop layer to limit the depth of source and drain material relative to a channel of the transistor. A portion of a channel material layer may be etched in preparation for source and drain materials. The etch may be stopped at an etch stop layer buried between a channel material layer and an underlying planar substrate layer. The etch stop layer may have a different composition than the channel layer while retaining crystallinity of the channel layer. The source and drain etch stop layer may provide adequate etch selectivity to ensure a source and drain etch process does not punch through the etch stop layer. Following the etch process, source and drain materials may be formed, for example with an epitaxial growth process. The source and drain etch stop layer may be, for example, primarily silicon and carbon.