Nanosheet ESD Protection Layout for High-Capability Diodes
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Solution Overview
Problem
Existing ESD protection circuits using nanowire FETs face challenges in forming effective diodes due to the difficulty in forming pads at the ends of nanowires, leading to increased area requirements and inefficient discharge capabilities, while no effective structures have been explored for nanosheet devices.
Innovation Solution
A semiconductor integrated circuit device incorporating a nanosheet FET with a specific layout configuration for an ESD protection circuit, where pad groups of different conductivity types are arranged to form diodes, with the opposing length in one direction being greater than the other, allowing for a larger capability diode to be configured within a small area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pads are formed at both ends of nanowire by epitaxial growth, then the nanowire structure is maintained, but the area for forming diode increases and discharge capability decreases
Solution Approach 1:
The patent transitions from one-dimensional nanowire structures to two-dimensional nanosheet structures. By forming multiple nanosheets stacked in the vertical direction, the diode structure achieves larger effective area for ESD protection without increasing lateral footprint. The nanosheets extend in the gate width direction, providing enhanced discharge capability while maintaining compact lateral dimensions.
Solution Approach 2:
The patent implements a stacked configuration where multiple nanosheets are nested vertically to form the diode structure. This nested arrangement allows the diode to utilize the vertical dimension for increased area, enabling larger discharge capability within a compact lateral footprint. The stacked nanosheets function collectively as a high-capability diode for ESD protection.
2Adaptability or versatility
If nanowire portions are used in ESD protection circuit, then the FET structure is utilized, but the nanowire does not contact substrate and cannot function as diode
Solution Approach 1:
The patent transitions from one-dimensional nanowire structures to two-dimensional nanosheet structures that make proper contact with the substrate. The nanosheets are configured to extend in the gate width direction and contact the substrate, enabling effective diode function for ESD protection while maintaining FET structure utilization.
3Ease of manufacture
If pads are formed by epitaxial growth from nanowire, then the growth process is utilized, but it is very difficult to form only pads
Solution Approach 1:
The patent extracts and utilizes the pad formation capability from the epitaxial growth process. By forming pads through epitaxial growth from the nanosheet structure, the method leverages existing growth processes to create functional pad regions without requiring separate complex fabrication steps, thereby simplifying manufacturing while enabling effective diode formation.
Data Source
AI summary
In an ESD protection circuit using a nanosheet device, a first device structure constituting one of the anode and the cathode is opposed to a second device structure constituting the other in the Y direction, and to a third device structure constituting the other in the X direction. The first device structure includes a pad group of a first conductivity type, and the second and third device structures each include a pad group of a second conductivity type. The length of a range in the X direction in which the pad group of the first device structure is opposed to the pad group of the second device structure in the Y direction is greater than the length of a range in the Y direction in which it is opposed to the pad group of the third device structure in the X direction.