BEOL On-Chip Sensor Detecting Interconnect Variations

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Solution Overview

Problem

Current on-chip sensors are not sensitive to back-end-of-line (BEOL) layer-to-layer interconnect variations, which affects the dynamic performance of complex CMOS system-on-chips (SoCs), leading to the need for additional voltage margins to compensate for undetected variations.

Innovation Solution

A BEOL on-chip sensor is integrated into the IC, featuring conductive and shield traces interdigitated in the BEOL layer, with logic to ground or float the shield traces, combining a variable wire-loaded ring oscillator with an unloaded ring oscillator to detect layer-to-layer interconnect variations by computing frequency ratios in different shield states.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If additional voltage margins are added to compensate for undetected BEOL variations, then reliability is improved, but device complexity and power consumption increase

Engineering Contradiction:

Improvedynamic performanceVSAvoidvoltage margin compensation

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The BEOL sensor enables the system to self-monitor and detect interconnect variations autonomously, eliminating the need for external compensation mechanisms and manual voltage margin adjustments

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The sensor provides real-time feedback on BEOL interconnect variations, allowing the system to dynamically adjust and optimize voltage margins based on actual conditions rather than using fixed conservative margins

Inventive Principle:

Principle #23Feedback

2Manufacturing precision

If BEOL layer-to-layer interconnect variations occur, then manufacturing precision is maintained, but measurement precision deteriorates

Engineering Contradiction:

Improvelayer-to-layer interconnectVSAvoidsensor detection

Core Design Contradiction:

Manufacturing precisionVSMeasurement precision

Solution Approach 1:

The sensor extends detection capability into the BEOL dimension by placing sensing elements directly within the BEOL layers, enabling measurement of variations that were previously undetectable by traditional sensing approaches

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The sensor acts as an intermediary element embedded in the BEOL structure that mediates between the physical interconnect variations and the measurement system, translating mechanical/electrical variations into detectable signals

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If more interconnect layers are added to support increased device complexity, then productivity is improved, but layer-to-layer interconnect variation increases

Engineering Contradiction:

Improvedevice interconnectionVSAvoidinterconnect variation

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The sensor is integrated into the BEOL structure during manufacturing, performing preliminary detection of interconnect variations before the device enters operation, allowing for early identification and compensation of precision issues

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11011459B1Back-end-of-line (BEOL) on-chip sensor

Publication Date: 2021.05.18 QUALCOMM INC

AI summary

An integrated circuit (IC), including a substrate and back-end-of-line (BEOL) layers on the substrate is described. The IC includes a sensor in a BEOL layer (Mx) of the BEOL layers. The BEOL sensor includes conductive traces and shield traces interdigitated with the conductive traces in the BEOL layer Mx. The BEOL sensor also includes a first ground shield in a BEOL layer Mx−1, and a second ground shield in a BEOL layer Mx+1. The BEOL sensor further includes logic configured to ground/float the shield traces.