Capacitance Bridge Demodulation for Leakage-Insensitive Measurement

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Solution Overview

Problem

Existing capacitance-measurement techniques suffer from limited sensitivity, particularly in measuring small capacitances due to transistor leakage currents, which complicates accurate capacitance modeling and alignment in high-performance integrated circuits and proximity communication systems.

Innovation Solution

A method involving time-varying signals with a predetermined phase relationship are used to demodulate signals across capacitors, isolating and amplifying received signals to determine relative capacitance, which is insensitive to transistor leakage and allows for high measurement sensitivity and accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If existing capacitance-measurement techniques are used, then measurement capability is available, but measurement precision deteriorates due to transistor leakage currents

Engineering Contradiction:

Improvecapacitance measurement precisionVSAvoidtransistor leakage current

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent replaces direct current measurement with signal demodulation. Instead of measuring small leakage currents directly, the system uses time-varying signals that are demodulated to extract capacitance information, substituting a mechanical/electrical measurement approach with a signal processing approach that is insensitive to leakage currents.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent employs periodic time-varying signals with predetermined phase relationships to drive the capacitors. By using periodic excitation signals and demodulating the responses, the system can extract capacitance information while rejecting DC leakage currents, as the leakage appears as a DC component that is filtered out during demodulation.

Inventive Principle:

Principle #19Periodic action

2Manufacturing precision

If capacitance measurements are performed in submicron integrated circuit processes, then circuit performance is improved, but measurement precision deteriorates due to extremely small capacitance values

Engineering Contradiction:

Improvewire dimension precisionVSAvoidcapacitance measurement precision

Core Design Contradiction:

Manufacturing precisionVSMeasurement precision

Solution Approach 1:

The patent changes the measurement parameter from direct capacitance measurement to measurement of time-varying signal responses. By measuring the phase and amplitude of demodulated signals rather than direct capacitance values, the system achieves high precision for extremely small capacitances (sub-femtoFarad range) that are difficult to measure with conventional techniques.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent substitutes direct capacitance measurement with signal demodulation measurement. The system measures the response of time-varying signals driven on the capacitors and demodulates these signals to extract capacitance information, replacing a direct measurement approach with an indirect signal processing approach that provides attoFarad resolution.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If alignment between transmitter pads and receiver pads is made more stringent, then communication performance is improved, but device complexity increases due to alignment requirements

Engineering Contradiction:

Improvecommunication performanceVSAvoidalignment requirement complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent uses capacitance measurements obtained through signal demodulation as feedback to determine and correct misalignment between chips. By measuring coupling capacitances with high precision and using this information to adjust pad positions or orientations, the system achieves effective alignment correction without requiring extremely stringent initial alignment tolerances.

Inventive Principle:

Principle #23Feedback

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 enables precise capacitance measurements, improving alignment and communication performance between semiconductor chips by reducing the impact of transistor leakage and enhancing the accuracy of capacitance modeling.

Implementation Method 1

capacitive coupling between the first proximity connector and a second proximity connector on the other semiconductor die

Methodology Applied

Scientific EffectCapacitive coupling: Capacitance

Data Source

PatentUS7425836B2Measuring chip-to-chip capacitance differentials by demodulating signals over a capacitance bridge

Publication Date: 2008.09.16 ORACLE AMERICAN INC

AI summary

In a method for determining capacitance, a first time-varying signal is driven on a first terminal of a first capacitor and a second time-varying signal is driven on a first terminal of a second capacitor, where the first time-varying signal and the second time-varying signal have a pre-determined phase relationship with each other.These signals are received on second terminals of the first capacitor and the second capacitor and demodulated using a periodic signal to produce demodulated signals. This periodic signal has the same fundamental frequency as the first time-varying signal and the second time-varying signal. A DC component in the demodulated signals is then determined by filtering the demodulated signals, and the sign of the DC component is used to determine a relative capacitance of the first capacitor and the second capacitor.