Isolation Well Charge Detection Circuit for Gate Oxide Monitoring

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Solution Overview

Problem

Current process charge detection circuits in IC fabrication cannot effectively monitor and detect damage caused by static electrical charge discharges between isolation wells during the BEOL processing, which can lead to gate oxide damage in field effect transistors.

Innovation Solution

A process charge detection circuit is designed with asymmetric RC time constants between aggressor and victim isolation wells, allowing for the detection and measurement of static electrical charge discharges through a gate oxide, incorporating a metal antenna connected to each isolation well to monitor voltage changes and prevent damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a process charge detection circuit is added to monitor static electrical charge between isolation wells, then damage to gate oxide can be detected, but device complexity increases

Engineering Contradiction:

Improvedetection of gate oxide damageVSAvoidcircuit structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The detection circuit is nested within the existing isolation well structure by utilizing the gate oxide of a transistor as the detection element. The aggressor isolation well and victim isolation well are integrated into the circuit layout without requiring separate external monitoring equipment, thus detecting charge discharge while minimizing additional complexity.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The circuit uses its own internal components (gate oxide, isolation wells, antennas) to perform the detection function. The victim isolation well's gate oxide naturally responds to charge discharge from the aggressor well, eliminating the need for external sensors or complex monitoring systems.

Inventive Principle:

Principle #25Self-service

2Measurement precision

If asymmetric RC time constants are implemented between aggressor and victim isolation wells, then static charge discharge can be measured, but manufacturing precision requirements increase

Engineering Contradiction:

Improvestatic charge discharge measurementVSAvoidRC time constant asymmetry

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

Different RC time constants are created by locally modifying the aggressor and victim isolation wells with different antenna configurations. The aggressor well is equipped with a first antenna having a first area, while the victim well has a second antenna with a second area, creating intentional local asymmetry that enables charge discharge measurement without requiring uniform precision across the entire circuit.

Inventive Principle:

Principle #3Local quality

3Measurement precision

If metal antennas with different areas are connected to isolation wells, then voltage changes can be monitored, but ease of manufacture decreases

Engineering Contradiction:

Improvevoltage change monitoringVSAvoidantenna fabrication

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The differentiation between aggressor and victim antennas is achieved through area variation in the same metal layer rather than requiring additional layers or complex three-dimensional structures. This two-dimensional approach to creating asymmetric RC time constants simplifies fabrication compared to vertical stacking or multi-layer configurations.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 circuit effectively detects and quantifies static electrical charge discharges between isolation wells, preventing damage to sensitive circuit components by enabling gradual release of process charge, thus enhancing the reliability of IC fabrication.

Implementation Method 1

detect damage caused by static electrical charge discharges between isolation wells during the BEOL processing

Methodology Applied

Scientific EffectElectrical charge discharge: Electrostatic Discharge

Implementation Method 2

asymmetric RC time constants between aggressor and victim isolation wells

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 3

Methodology Applied

Scientific EffectRC time constant:

Data Source

PatentUS20240387298A1Structure for detecting/monitoring process charging damage due to metal and isolation well charging

Publication Date: 2024.11.21 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method of detecting or monitoring process electrical charge produced during fabrication of an integrated circuit (IC) on a semiconductor wafer includes fabricating a process charge detection circuit on or in the semiconductor wafer, including: a victim isolation well, a gate oxide disposed on or in the victim isolation well, an aggressor isolation well electrically connected with the victim isolation well via the gate oxide, a victim antenna electrically connected with the victim isolation well and together with the victim isolation well defining a victim RC time constant, and an aggressor antenna electrically connected with the aggressor isolation well and together with the aggressor isolation well defining an aggressor RC time constant that is different from the victim RC time constant. Process charge is detected using the process charge detection circuit. The detecting comprises measuring an electrical parameter of the gate oxide.