PCB Plasma Current Sensing for RF Station Uniformity

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Solution Overview

Problem

Existing semiconductor processing technologies face challenges in maintaining uniformity and repeatability across multiple stations due to variations in RF power distribution, leading to inconsistencies in deposition and etch rates, which affect the overall process and product quality.

Innovation Solution

A system that measures plasma current using an inductive element and capacitive element integrated on a printed circuit board, converts the measured voltage to current using a linear proportionality factor dependent on the RF power frequency, and adjusts the RF power frequency to reduce station-to-station variations, ensuring consistent plasma conditions across multiple stations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If RF power is distributed to multiple stations without frequency tuning, then processing throughput is maintained, but station-to-station variations in plasma conditions occur

Engineering Contradiction:

Improveprocessing throughputVSAvoidstation-to-station uniformity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The system dynamically tunes the RF power frequency at each station based on real-time plasma current measurements. Instead of using a fixed frequency across all stations, each station's RF frequency is adjusted to compensate for variations in plasma conditions, thereby maintaining uniform processing while preserving high throughput

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the RF power frequency parameter dynamically across different stations. By measuring plasma current and adjusting the frequency accordingly, the system optimizes plasma conditions at each station individually, resolving the uniformity issue without sacrificing productivity

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If RF frequency is tuned to reduce station variations, then manufacturing precision improves, but measurement and control complexity increases

Engineering Contradiction:

Improveplasma condition uniformityVSAvoidfrequency tuning system complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The system implements a feedback mechanism where plasma current is measured at each station and used to adjust the RF frequency. This closed-loop control automatically compensates for station variations without requiring complex manual calibration or intervention, managing system complexity through automated feedback control

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

Each station essentially self-adjusts its RF frequency based on its own plasma current measurements. The system autonomously optimizes plasma conditions at each station without requiring external intervention or complex centralized control, reducing operational complexity

Inventive Principle:

Principle #25Self-service

3Measurement precision

If plasma current is measured using traditional sensors, then measurement accuracy is achieved, but device complexity and cost increase

Engineering Contradiction:

Improveplasma current measurement accuracyVSAvoidcurrent sensor complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The invention introduces an intermediary measurement approach by measuring voltage across an inductive element rather than directly measuring plasma current. This voltage measurement serves as a proxy for current, simplifying the measurement system while maintaining the ability to adjust RF frequency for optimal plasma conditions

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system replaces direct electrical current measurement with voltage measurement across an inductive element. This substitution simplifies the measurement apparatus by using voltage sensing instead of complex current sensing, reducing device complexity while preserving measurement functionality

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 enhances within-wafer uniformity and wafer-to-wafer repeatability by dynamically adjusting RF power frequency, thereby improving the consistency and quality of semiconductor processing operations such as deposition, etching, and cleaning.

Implementation Method 1

measuring a voltage across an inductive element in a current sensor, the inductive element being electrically parallel to a capacitive element in the current sensor, the inductive element being electrically inline relative to plasma current flow

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

converting the measured voltage to current using a linear proportionality factor dependent on the RF power frequency

Methodology Applied

Scientific EffectResonance: Resonance

Implementation Method 3

distributing RF power to multiple stations to thereby generate a plasma in the stations

Methodology Applied

Scientific EffectPlasma generation: Plasma

Data Source

PatentUS20240347400A1RF current measurement in semiconductor processing tool

Publication Date: 2024.10.17 LAM RES CORP

AI summary

Methods and apparatus for measuring current are disclosed.