Backside Trench Gate Isolation in Nanosheet Integrated Circuits
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Solution Overview
Problem
Existing integrated circuits face challenges in increasing computing power due to difficulties in forming gate terminals with desired characteristics for nanosheet transistors, leading to electrical shorting of gate electrodes.
Innovation Solution
The use of backside trenches etched from the backside of the substrate through the gate metals to electrically isolate individual gate electrodes of nanosheet transistors, avoiding the need for separate photolithography processes and allowing for high-density transistor formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gate metals are deposited over all channel regions, then continuous gate coverage is achieved, but gate electrodes become electrically shorted
Solution Approach 1:
The continuous gate metal layer is segmented into individual gate electrodes by forming trenches through the substrate and gate metal from the backside. This segmentation electrically isolates adjacent gate electrodes while maintaining a simplified frontside process where gate metal is deposited as a continuous layer.
Solution Approach 2:
Instead of forming isolation trenches from the frontside after gate metal deposition (which would require complex photolithography), the patent inverts the approach by forming trenches from the backside of the substrate. This allows gate electrode isolation to be achieved through substrate thinning and backside etching, simplifying the overall process.
2Reliability
If separate photolithography processes are used to isolate gate electrodes, then electrical isolation is achieved, but manufacturing complexity and cost increase
Solution Approach 1:
The substrate thinning process and gate electrode isolation process are merged into a single backside trench formation operation. The same trench that removes substrate material to achieve desired thickness also serves to electrically isolate gate electrodes, eliminating the need for separate photolithography and etching steps.
Solution Approach 2:
The backside trenches automatically define gate electrode boundaries through self-aligned etching. The trench formation process inherently creates the isolation structures needed for individual gate electrodes without requiring additional masking or patterning steps, allowing the process to define its own geometry.
3Reliability
If traditional frontside trench formation is used, then gate electrode isolation is achieved, but transistor density decreases
Solution Approach 1:
The patent transitions from two-dimensional frontside trench formation to three-dimensional backside trench formation. By etching through the backside of the thinned substrate, isolation trenches can be formed without occupying additional lateral space on the frontside, thereby maintaining high transistor density while achieving effective gate electrode isolation.
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
This approach effectively isolates gate electrodes, reduces transistor heights, and enables more cost-effective and efficient transistor formation with improved performance and higher wafer yields.
Implementation Method 1
a first trench is formed by removing a first portion of a substrate and removing a first portion of the gate metal
Data Source
AI summary
An integrated circuit includes a first nanosheet transistor and a second nanosheet transistor on a substrate. The first and second nanosheet each include gate electrodes. A gate isolation structure extends from a backside of the substrate between the gate electrodes. The gate isolation structure physically and electrically isolates the first and second gate electrodes from each other.