Guard Ring Capacitor Biasing for High-Density IC Decoupling

Solution Overview

Problem

Integrated circuits (ICs) face challenges in addressing potential latch-up behavior due to parasitic bipolar transistors and require efficient capacitive devices to reduce noise, while existing guard ring structures occupy significant area without providing adequate capacitance.

Innovation Solution

Configuring guard ring structures as capacitive devices within ICs, such as decoupling capacitors, to enhance capacitance density by integrating them with transistor gates and heavily doped regions, allowing for biasing with voltage levels to operate in inversion or depletion modes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional non-capacitive guard ring structures are used, then latch-up protection is provided, but capacitance density is insufficient and area consumption is high

Engineering Contradiction:

Improvelatch-up protectionVSAvoidarea consumption

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The guard ring structure is configured to perform dual functions: maintaining its traditional latch-up protection capability while simultaneously operating as a capacitive device (decoupling capacitor). This is achieved by biasing the gate of the guard ring transistor to a voltage level that creates a depletion region, enabling capacitance without sacrificing the guard ring's protective function.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The operating state of the guard ring transistor is changed by applying specific bias voltages to its gate. By biasing the gate to a voltage level different from the substrate potential, the transistor is placed in a state that generates a depletion region, thereby transforming the guard ring from a purely protective structure into a functional capacitive element with useful capacitance.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If traditional non-capacitive guard ring structures are used, then latch-up protection is provided, but capacitance density is insufficient

Engineering Contradiction:

Improvelatch-up protectionVSAvoidcapacitance density

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The guard ring structure is configured to perform dual functions: maintaining its traditional latch-up protection capability while simultaneously operating as a capacitive device (decoupling capacitor). This is achieved by biasing the gate of the guard ring transistor to a voltage level that creates a depletion region, enabling capacitance without sacrificing the guard ring's protective function.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The operating state of the guard ring transistor is changed by applying specific bias voltages to its gate. By biasing the gate to a voltage level different from the substrate potential, the transistor is placed in a state that generates a depletion region, thereby transforming the guard ring from a purely protective structure into a functional capacitive element with useful capacitance.

Inventive Principle:

Principle #35Parameter changes

3Quantity of substance

If guard ring structures are configured as capacitive devices, then capacitance density increases by up to five times, but additional biasing circuitry is required

Engineering Contradiction:

Improvecapacitance densityVSAvoidbiasing circuitry

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The biasing functionality is merged with the existing guard ring structure itself. The gate of the guard ring transistor, which already exists as part of the protective structure, is repurposed as the control electrode for the capacitor. This eliminates the need for separate biasing circuitry while achieving the desired capacitance density improvement.

Inventive Principle:

Principle #5Merging (Combining)

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 configuration reduces the required area for achieving a given capacitance level and increases overall capacitance density by up to five times compared to traditional non-capacitive guard ring structures.

Implementation Method 1

configuring guard ring structures as capacitive devices within ICs, such as decoupling capacitors, to enhance capacitance density

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

allowing for biasing with voltage levels to operate in inversion or depletion modes

Methodology Applied

Scientific EffectDepletion mode operation:

Data Source

PatentUS20250366192A1Guard ring capacitor operating method

Publication Date: 2025.11.27 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method of biasing a guard ring structure includes biasing a gate of a MOS transistor to a first bias voltage level, biasing first and second source/drain (S/D) regions of the MOS transistor to a power domain voltage level, biasing a gate of the guard ring structure to a second bias voltage level, and biasing first and second heavily doped regions of the guard ring structure to the power domain voltage level. Each of the first and second S/D regions has a first doping type, each of the first and second heavily doped regions has a second doping type different from the first doping type, and each of the first and second S/D regions and the first and second heavily doped regions is positioned in a substrate region having the second doping type.