Microbalance Sensor for Atomic Layer Deposition
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current atomic layer deposition (ALD) techniques face challenges in accurately measuring film thickness and mass during the process due to temperature fluctuations and the limitations of existing microbalance systems, which are not suitable for in situ monitoring at high temperatures and can introduce measurement errors.
Innovation Solution
A microbalance system integrated within the ALD reactor chamber, featuring a piezoelectric element with pressure equalization and thermal communication, allowing for real-time deposition rate monitoring with minimal disruption to the process and capable of operating over a wide temperature range, enabling rapid thermal equilibration and accurate mass measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a microbalance is integrated within the ALD reactor chamber for in situ monitoring, then real-time deposition rate monitoring is achieved, but temperature fluctuations cause measurement errors
Solution Approach 1:
A reference crystal is introduced as an intermediary element that experiences the same temperature fluctuations as the measurement crystal but is shielded from deposition. By comparing the frequency changes of both crystals, the system separates temperature-induced errors from actual mass deposition, enabling accurate thickness measurements despite temperature instability.
Solution Approach 2:
The system continuously monitors the frequency difference between the measurement crystal and reference crystal, using this feedback to compensate for temperature effects. The differential measurement approach allows real-time correction of temperature drift, maintaining measurement precision throughout the ALD process.
2Measurement precision
If tight temperature control is implemented to reduce temperature-induced variations, then measurement accuracy improves, but system complexity and cost increase
Solution Approach 1:
Instead of implementing complex temperature control systems, the patent uses a reference crystal as a mediator to sense temperature fluctuations. This passive approach eliminates the need for active temperature stabilization while achieving the same measurement accuracy through differential comparison.
Solution Approach 2:
The patent replaces the mechanical/thermal control system (PID controllers, heating elements, insulation) with a sensor-based differential measurement system. By substituting physical temperature stabilization with a comparative sensing approach, the system achieves temperature compensation without the associated complexity.
3Measurement precision
If the microbalance is positioned to monitor deposition on the substrate, then real-time thickness monitoring is achieved, but deposition on unintended surfaces causes measurement errors
Solution Approach 1:
The reference crystal is positioned and shielded such that only the measurement crystal is exposed to the deposition flux from the source. This localized exposure ensures that the reference crystal experiences identical temperature conditions while remaining free from contamination, maintaining its utility as a temperature reference.
Solution Approach 2:
The harmful effect of unintended deposition is eliminated by extracting the reference crystal from the deposition zone while keeping it in the thermal environment. This separation allows the reference crystal to serve its temperature sensing function without being contaminated by deposited material.
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
The system provides accurate, real-time monitoring of film deposition rates with reduced temperature fluctuations and minimal disruption to the ALD process, enabling precise control and characterization of film thickness during fabrication.
Implementation Method 1
a piezoelectric element within the aperture, whereby a first region of the piezoelectric element is in fluid communication with the chamber and the second region is isolated from the chemical reactants in the reaction chamber
Implementation Method 2
a means to induce oscillation of the piezoelectric element at a first frequency wherein a change in the oscillation of the piezoelectric element is proportional to the deposition of the substance on the first region of the piezoelectric element
Implementation Method 3
Vapor deposition, in particular physical vapor deposition (PVD) and chemical vapor deposition (CVD), comprises low pressure processes to condense and deposit vaporized material onto workpiece surfaces
Implementation Method 4
CVD employs chemical reactions to produce high-purity, high-performance solid materials. The process is used in semiconductor manufacturing to form thin films
Implementation Method 5
comprises low pressure processes to condense and deposit vaporized material onto workpiece surfaces
Data Source
AI summary
The invention is directed to QCM measurements in monitoring ALD processes. Previously, significant barriers remain in the ALD processes and accurate execution. To turn this exclusively dedicated in situ technique into a routine characterization method, an integral QCM fixture was developed. This new design is easily implemented on a variety of ALD tools, allows rapid sample exchange, prevents backside deposition, and minimizes both the footprint and flow disturbance. Unlike previous QCM designs, the fast thermal equilibration enables tasks such as temperature-dependent studies and ex situ sample exchange, further highlighting the feasibility of this QCM design for day-to-day use. Finally, the in situ mapping of thin film growth rates across the ALD reactor was demonstrated in a popular commercial tool operating in both continuous and quasi-static ALD modes.