Backside Ballast Resistor Layout for Uniform Nanosheet Current
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Solution Overview
Problem
Existing semiconductor devices lack effective mechanisms to uniformly distribute current and prevent over-current faults, particularly in nanosheet transistors, which are prone to instability due to varying current levels.
Innovation Solution
Incorporation of a backside ballast resistor that electrically contacts the bottommost surface of the source/drain region, allowing for dynamic resistance adjustment based on current levels to maintain a constant current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If no ballast resistor is used, then the device structure remains simple, but current distribution becomes non-uniform and over-current faults occur
Solution Approach 1:
The ballast resistor is formed on the backside of the substrate rather than the frontside, utilizing the third dimension (substrate thickness) to resolve the contradiction. This allows current regulation functionality to be added without occupying valuable frontside device area and without interfering with the transistor structure, thereby improving current distribution uniformity while maintaining relatively simple device structure
Solution Approach 2:
The ballast resistor acts as an intermediary element between the power supply and the transistor source/drain region. It mediates the current flow by providing dynamic resistance adjustment, preventing over-current faults and ensuring uniform current distribution to the transistor while maintaining overall system simplicity
2Stability of the object's composition
If a ballast resistor is added to regulate current, then current stability improves, but the device structure becomes more complex
Solution Approach 1:
By placing the ballast resistor on the backside of the substrate and having it extend through a portion of the substrate thickness, the invention utilizes the vertical dimension to achieve current stability without adding lateral complexity to the device structure. The resistor contacts the bottommost surface of the source/drain region, providing stable current regulation while maintaining a compact overall structure
Solution Approach 2:
The backside ballast resistor structure serves multiple functions: it provides current regulation, acts as a structural support element, and utilizes the substrate itself as part of the resistor body. This multi-functionality reduces the need for additional separate components, thereby improving current stability while minimizing the increase in device complexity
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 backside ballast resistor effectively stabilizes current flow in nanosheet transistors, preventing over-current faults and ensuring uniform current distribution, thereby enhancing the reliability and performance of semiconductor devices.
Implementation Method 1
Ballast resistors are able to change resistance with the current. If the current flowing through the resistor increases above the threshold value, the resistance increases. The resistance can then correspondingly decrease as the current decreases.
Data Source
AI summary
A semiconductor device is provided that includes a transistor located in a first device area and including a gate structure, a first source/drain region located on a first side of the gate structure and a second source/drain region located on a second side of the gate structure. The semiconductor device also includes a frontside source/drain contact structure contacting a topmost surface of the first source/drain region, a backside ballast resistor electrically contacting a bottommost surface of the second source/drain region, and a backside source/drain contact structure in contact with the backside ballast resistor.