Compact ESD Protection Using Multi-Gate HEMT
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Solution Overview
Problem
Existing ESD protection structures for high-electron-mobility transistors (HEMTs) require large areas due to the need for cascading multiple Schottky diodes, which are inefficient in terms of space and cost, as HEMTs lack a robust P-N junction diode for compact ESD protection.
Innovation Solution
A compact ESD protection device using a multiple-gate HEMT structure with diodes and resistors to form ESD trigger and charge draining paths, reducing the area required for protection by integrating the diodes and resistors on an integrated circuit die, thereby minimizing the need for multiple Schottky diodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple Schottky diodes are cascaded in series to protect the gate of a HEMT device, then ESD protection capability is improved, but die area consumption increases significantly
Solution Approach 1:
The patent combines multiple Schottky diodes into a single integrated ESD protection structure that shares common electrodes and processing steps. The first and second Schottky diodes are formed using the same gate electrode, reducing the total area required compared to separate discrete diodes. This merging approach maintains the ESD protection functionality while significantly reducing die area consumption.
Solution Approach 2:
The gate electrode serves multiple functions: it acts as the gate for the HEMT device during normal operation and simultaneously serves as a common electrode for both Schottky diodes during ESD protection events. This multi-functionality eliminates the need for separate dedicated ESD protection structures, reducing overall die area while maintaining protection capability.
2Reliability
If Schottky diodes are used for ESD protection in HEMT circuits, then ESD protection is provided, but manufacturing complexity and cost increase due to additional processing steps
Solution Approach 1:
The patent merges the ESD protection structure with the existing HEMT fabrication process by forming Schottky contacts using the same metal deposition and annealing steps already required for gate electrode formation. This integration eliminates additional manufacturing steps and reduces process complexity compared to implementing separate Schottky diodes.
Solution Approach 2:
The ESD protection structure utilizes the gate electrode itself as a functional component for both device operation and ESD protection. The gate electrode's inherent properties (metal-semiconductor junction) automatically provide the Schottky barrier needed for ESD protection without requiring separate dedicated structures or additional processing.
3Reliability
If large Schottky diodes are formed to handle ESD current, then ESD protection capability is improved, but die area consumption increases
Solution Approach 1:
The patent combines the current handling paths of multiple Schottky diodes through a shared common electrode structure. The first and second Schottky diodes share the gate electrode as a common terminal, allowing ESD current to be distributed through this shared path. This merging of current paths maintains ESD handling capability while reducing the total area required compared to separate large-area diodes.
Solution Approach 2:
The patent transitions from a planar arrangement of separate diodes to a three-dimensional integrated structure where Schottky contacts are formed at different locations but share common electrodes. This dimensional integration allows current handling capability to be maintained through vertical and lateral current paths without proportionally increasing die area.
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 solution provides effective ESD protection in a smaller area than traditional multi-diode structures, enhancing system efficiency and reducing die area consumption while maintaining high switching speed and efficiency.
Implementation Method 1
In a Schottky diode, a semiconductor-metal junction is formed between a semiconductor and a metal, thus creating a Schottky barrier. This Schottky barrier results in both a low forward voltage drop and very fast switching.
Implementation Method 2
A HEMT, also known as heterostructure FET (HFET) or modulation-doped FET (MODFET), is a field-effect transistor incorporating a junction between two materials with different band gaps (i.e., a heterojunction) as the channel instead of a doped region
Data Source
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AI summary
A multi-gate Schottky depletion-mode field effect transistor (FET), at least one diode and two resistors comprise a compact electrostatic discharge (ESD) protection structure. This ESD protection structure can be laid out in a smaller area than typical multiple diode ESD devices. The multi-gate FET may comprise various types of high-electron-mobility transistor (HEMT) devices, e.g., (pseudomorphic) pHEMT, (metamorphic) mHEMT, induced HEMT. The multiple gates of the Schottky field effect device are used to form an ESD trigger and charge draining paths for protection of circuits following the ESD protection device. Both single and dual polarity ESD protection devices may be provided on an integrated circuit die for protection of input-output circuits thereof.