3D Contact Cavity Structure for Lower MOSFET Contact Resistance
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Solution Overview
Problem
Contact resistance in semiconductor devices, particularly in multi-gate metal-oxide-semiconductor field-effect transistors (MOSFETs), is increasing due to their 3D designs and small sizes, leading to decreased device performance.
Innovation Solution
A method involving cavity shaping processes to form n-MOS and p-MOS cavities in semiconductor structures, followed by selective deposition to create electrical contacts, which includes forming contact cavities using hydrogen (H2) and chlorine (Cl2) plasma etching, and biasing the substrate to enhance the contact interface surface area without increasing the critical dimension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the contact size is increased to reduce contact resistance, then the contact resistance decreases, but the critical dimension increases which is not acceptable in scaled devices
Solution Approach 1:
The patent transitions from a planar contact interface to a three-dimensional cavity structure. By etching contact cavities into the semiconductor substrate and filling them with conductive material, the contact interface extends vertically into the substrate, increasing the effective contact area without expanding the lateral critical dimension. This dimensional transition allows reduced contact resistance while maintaining scaled device dimensions.
Solution Approach 2:
The contact structure is nested within the semiconductor device architecture. Contact cavities are formed and embedded within the substrate, with conductive fill material nested within the cavity structures. This nesting approach increases contact area by utilizing the vertical space within the existing device footprint, rather than expanding outward.
2Reliability
If a cavity shaping process is performed to increase contact interface surface area, then contact resistance decreases, but the manufacturing process complexity increases
Solution Approach 1:
The contact formation process is segmented into distinct sequential steps: cavity definition, cavity shaping/etching, and conductive fill. This segmentation allows each step to be optimized independently and performed using specialized equipment, making the complex overall process more manageable and controllable despite the increased number of steps.
Solution Approach 2:
Contact cavities are formed and shaped before the final conductive fill step. This preliminary action of creating the cavity structure in advance allows for precise control of the contact interface geometry and ensures proper preparation of the substrate surface before introducing the conductive material, facilitating better process control despite the additional steps.
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 reduces contact resistance by increasing the contact interface surface area, thereby improving the performance of electrical contacts in semiconductor devices.
Implementation Method 1
forming contact cavities using hydrogen (H2) and chlorine (Cl2) plasma etching
Data Source
AI summary
A method of forming an electrical contact in a semiconductor structure includes performing a cavity shaping process on a semiconductor structures having an n-type metal oxide semiconductor (n-MOS) region and/or a p-type MOS (p-MOS) region, the cavity shaping process comprising forming an n-MOS cavity in an exposed surface of the n-MOS region and/or a p-MOS cavity in an exposed surface of the p-MOS region, wherein the cavity shaping process is configured to increase the surface area of the exposed surface of the n-MOS region or the p-MOS region. In some embodiments, the method includes performing a first selective deposition process to form a p-MOS cavity contact, selectively in the p-MOS cavity.