On-Chip ESD Sensor Using MOSCAP Arrays and Breakdown Capacitors
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Solution Overview
Problem
Electrostatic discharge (ESD) causes significant damage to integrated circuits (ICs), resulting in approximately 35% of field returns and substantial financial losses, as existing ESD protection circuits are often overwhelmed by static charge accumulation during handling and transport, necessitating an effective on-chip ESD detection solution.
Innovation Solution
Two on-chip ESD detection approaches are proposed: the variable dielectric width capacitor, which employs metal plates with sharp corners to enhance local electric field intensity for dielectric breakdown, and the vertical metal-oxide-semiconductor (MOS) capacitor (MOSCAP) array, both designed for integration in GlobalFoundries 22 nm fully depleted silicon-on-insulator technology, allowing for accurate detection of ESD events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ESD protection circuits are used in ICs, then device reliability is improved, but the protection circuits can be overwhelmed by static charge accumulation during transport and handling, resulting in ESD damage
Solution Approach 1:
The patent implements on-chip ESD sensors that detect electrostatic charge accumulation before it reaches dangerous levels. The sensor includes a capacitor that accumulates charge and a detection circuit that monitors the voltage, enabling preliminary detection of ESD events before they cause damage to the IC.
Solution Approach 2:
The ESD sensor provides feedback about the electrostatic environment to the system. The detection circuit generates signals indicating ESD events, allowing the system to respond appropriately, such as preventing operation or alerting handlers to ESD risks during transport and handling.
2Measurement precision
If conventional ESD detection methods are used, then ESD events can be detected, but accurate tracking of ESD events from manufacturing to end-of-life is not achieved
Solution Approach 1:
The on-chip ESD sensor is integrated into the IC during manufacturing, enabling continuous monitoring of ESD events from the manufacturing stage through transport, handling, and operation. This preliminary integration ensures no ESD events are missed and complete electrostatic history is captured.
Solution Approach 2:
The ESD sensor serves multiple functions: detecting ESD events during manufacturing, monitoring charge accumulation during transport and handling, and providing ongoing protection information during IC operation. This multi-functional approach enables comprehensive tracking of the IC's electrostatic history across all stages of its lifecycle.
3Reliability
If on-chip ESD sensors are integrated, then ESD event tracking is enabled, but device complexity increases
Solution Approach 1:
The ESD sensor is merged with the IC's existing structure and processes. The capacitor can be formed using existing interlayer dielectric layers and metal traces, and the detection circuit can share logic with existing IC functionality, reducing the incremental complexity of adding ESD monitoring capability.
Solution Approach 2:
The detection circuit is designed to perform multiple functions: monitoring capacitor voltage for ESD detection, generating appropriate output signals, and potentially interfacing with existing IC control logic. This multi-functionality reduces the need for separate dedicated ESD monitoring components, thereby limiting complexity increase.
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 proposed solutions enable precise tracking of ESD events from manufacturing to end-of-life, reducing IC failures by identifying compromised parts and preventing assembly of damaged components, with the variable dielectric width capacitor suitable for high ESD voltage detection and the MOSCAP array effective for low voltage detection, thereby minimizing ESD-induced losses.
Implementation Method 1
The variable dielectric width capacitor approach employs metal plates terminated with sharp corners to enhance local electric field and facilitate ready breakdown of a thin dielectric between the metal plates
Implementation Method 2
vertical metal-oxide-semiconductor (MOS) capacitor MOSCAP array... detect ESD events starting from about 6 V with about 6 V granularity
Data Source
AI summary
Two approaches for on-chip ESD detection include variable dielectric width capacitor, and vertical metal-oxide-semiconductor (MOS) capacitor MOSCAP array. The variable dielectric width capacitor approach employs metal plates terminated with sharp corners to enhance local electric field and facilitate ready breakdown of a thin dielectric between the metal plates. The vertical MOSCAP array is composed of a capacitor array connected in series. Both approaches are incorporated in an example 22 nm fully depleted silicon-on-insulator. Vertical MOSCAP arrays detect ESD events starting from about 6 V with about 6 V granularity, while the variable dielectric width capacitor is suitable for detection of high ESD voltage from about 40 V and above.