FinFET Body-Bias Control via Segmented Source Contacts
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Solution Overview
Problem
Existing FinFETs face challenges with controlling threshold voltage due to floating fins on SOI substrates, leading to increased junction leakage current, off-current, and contact resistance, which reduces integration density and performance.
Innovation Solution
The semiconductor device employs a structure with fins protruding from a substrate, where source and drain regions are formed within each fin, and a gate electrode is positioned between the channel regions on the inner sides of the fins, with source and drain contact plugs insulated from the body, allowing for better control of body-bias and reduced contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If FinFETs are fabricated using SOI substrate with floating fins, then channel area is increased and current flow is enhanced, but threshold voltage control becomes difficult and body-bias control is compromised
Solution Approach 1:
The device is divided into two separate structures: a first FinFET with its source and drain regions, and a second FinFET with its source and drain regions. This segmentation allows independent control of each FinFET's source and drain, enabling body-bias control while maintaining the benefits of increased channel area from the fin structure.
Solution Approach 2:
A first contact plug is introduced as an intermediary element that contacts both the first source and the second source simultaneously. This intermediary structure enables electrical connection and control between the two separated FinFET sources, facilitating body-bias control without requiring direct contact between the FinFETs and the substrate.
2Power
If drain depletion region is expanded using bulk substrate, then device performance is improved, but junction leakage current and off-current increase
Solution Approach 1:
By separating the FinFETs into two independent structures with individually controlled sources and drains, the patent achieves better control over the depletion regions. This segmentation prevents excessive expansion of the drain depletion region into the substrate, thereby reducing junction leakage current and off-current while maintaining device performance.
3Reliability
If bit line contacts are formed to run across fins, then electrical connection is achieved, but contact resistance increases and fabrication difficulty increases
Solution Approach 1:
Instead of forming contacts that run across the fins (horizontal approach), the patent inverts the approach by forming contact plugs that contact the sources vertically from the substrate. This inversion simplifies the fabrication process by avoiding the need to bend fins or create complex through-fin contacts, while still achieving reliable electrical connection.
4Reliability
If source and drain regions are formed wider to ensure contact area, then contact reliability is improved, but distance between fins increases and integration density is reduced
Solution Approach 1:
The patent transitions from increasing contact area in the lateral dimension (wider source and drain regions) to increasing contact area in the vertical dimension (contact plugs extending from the substrate to the sources). This dimensional change allows for reliable electrical connection without increasing the lateral footprint, thereby maintaining high integration density.
Data Source
AI summary
A semiconductor device may include at least one pair of fins on a semiconductor substrate. A channel region may be formed in each fin. The semiconductor device may further include a gate electrode corresponding to each pair of channel regions, a source contact plug electrically connected to each of at least one source formed on a respective fin concurrently, and a drain contact plug electrically connected to each of at least one drain formed on a respective fin concurrently.