Local Clock Buffer Antenna Diode Layout for Lower Capacitance

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Solution Overview

Problem

Integrated circuits (ICs) face antenna violations in local clock buffers (LCBs) due to gate oxide sensitivity, leading to potential damage and performance issues, which existing solutions exacerbate with external antenna diodes causing metal congestion and capacitance.

Innovation Solution

Placing antenna diodes within LCB blocks and connecting them to LCB pins only when violations occur, reducing the need for long connections and minimizing metal usage, thereby alleviating antenna violations and signal issues.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If external antenna diodes are used to address antenna violations in LCBs, then antenna violations are alleviated, but metal congestion and capacitance increase

Engineering Contradiction:

Improveantenna violation mitigationVSAvoidmetal congestion and capacitance

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The antenna diode is merged with the LCB block by placing it within the same block and sharing the diffusion structure. The diode shares the n-well and p-substrate with the LCB transistors, eliminating the need for separate external diode structures and their associated metal connections.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The antenna diode function is extracted from external separate structures and integrated into the LCB block itself. The diode is formed using the existing diffusion layers (n-well and p-substrate) already present in the LCB, removing the need for external antenna diode components.

Inventive Principle:

Principle #2Taking out (Extraction)

2Device complexity

If antenna diodes are placed within LCB blocks and connected only when violations occur, then metal usage is reduced, but manufacturing complexity increases

Engineering Contradiction:

Improvemetal usageVSAvoidmanufacturing complexity

Core Design Contradiction:

Device complexityVSEase of manufacture

Solution Approach 1:

The antenna diode structure is prepared in advance during the standard LCB fabrication process. The n-well and p-substrate diffusion layers are formed as part of the normal LCB manufacturing sequence, so the diode structure exists beforehand and only requires selective connection later.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The connection between the antenna diode and LCB pin is made dynamic and conditional. The diode connection to the LCB pin is established only when an antenna violation is detected, allowing the structure to adapt based on actual needs rather than being permanently connected.

Inventive Principle:

Principle #15Dynamics

3Device complexity

If antenna diodes are disconnected from LCBs, then capacitance is reduced, but antenna violations are not addressed

Engineering Contradiction:

ImprovecapacitanceVSAvoidantenna violation protection

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The antenna diode connection state is made dynamic rather than static. The diode can be disconnected (reducing capacitance) or connected (providing protection) based on whether an antenna violation is present, allowing the system to optimize between these two states.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The LCB block itself provides the antenna diode structure using its own diffusion layers. The n-well and p-substrate form the diode automatically as part of the LCB fabrication, eliminating the need for separate external diode components and their associated capacitance.

Inventive Principle:

Principle #25Self-service

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 approach reduces metal congestion and capacitance while effectively addressing antenna violations in LCBs, improving IC performance and reducing manufacturing complexity.

Implementation Method 1

antenna violations in local clock buffers (LCBs) due to gate oxide sensitivity

Methodology Applied

Scientific EffectAntenna effect: Electrostatic Induction

Implementation Method 2

diodes produced by drain and source diffusion layers can conduct a significant amount of current

Methodology Applied

Scientific EffectDiode conduction: Diode

Data Source

PatentUS20250363279A1Local clock buffer with antenna diode feature

Publication Date: 2025.11.27 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

Techniques relating to identifying an antenna violation for a first local clock buffer (LCB) for an integrated circuit (IC). The IC includes a first LCB block containing the first LCB and a first antenna diode disconnected from the first LCB, and a second LCB block containing a second LCB and a second antenna diode, different from the first antenna diode, disconnected from the second LCB. The techniques include determining, based on the identifying the antenna violation, to connect the first antenna diode to the first LCB, and connecting the first antenna diode to the first LCB in the first LCB block. The second antenna diode remains disconnected from the second LCB after the connecting.