In-Situ Interferometric Etch Rate Measurement in Vacuum Chambers
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Solution Overview
Problem
Existing ion beam etch and deposition rate measurement systems require time-consuming processes due to the need for sample probes to be inserted and removed from vacuum chambers, have limited probe lifetimes, and necessitate large reference objects, which are costly and inefficient.
Innovation Solution
An in-situ measurement system using an interferometric device within the vacuum chamber to determine etch or deposition rates by directing light onto a sample surface and measuring thickness variations in real-time, eliminating the need for ex-situ measurements and large reference probes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ex-situ measurement with sample probe insertion and removal is used, then measurement can be performed, but processing time increases
Solution Approach 1:
The patent introduces an optical window as an intermediary element that allows optical measurement signals to pass through the vacuum chamber wall, enabling in-situ interferometric measurements without breaking vacuum or inserting/removing sample probes. This mediator resolves the contradiction by providing a transmission path for measurement light while maintaining the vacuum seal.
Solution Approach 2:
The patent replaces the mechanical insertion/removal of sample probes with an optical measurement system that transmits light through the vacuum chamber window. This substitution eliminates the mechanical operations that cause time loss while maintaining measurement capability.
2Measurement precision
If sample probe is used for etch rate measurement, then etch rate can be determined, but sample probe lifetime is limited
Solution Approach 1:
The optical window serves as a mediator that separates the measurement system from the sample, allowing measurements to be performed on the actual sample in-situ without requiring separate sample probes. This eliminates the wear and degradation issues associated with reusable sample probes.
Solution Approach 2:
The patent uses optical interference patterns as a copy or representation of the sample surface topography changes. Instead of physically contacting and potentially damaging the sample with a probe, the system creates an optical copy of the surface geometry through interferometry, enabling repeated measurements without sample degradation.
3Measurement precision
If large reference objects are used for interferometric measurements, then full ion beam profile can be determined, but device complexity and cost increase
Solution Approach 1:
The patent measures the back surface of the sample rather than the front surface exposed to the ion beam. This dimensional change allows measurement of the complementary surface that undergoes corresponding topography changes, enabling ion beam profile determination without requiring large reference objects to cover the entire beam footprint.
Solution Approach 2:
The patent changes the measurement parameter from direct front-surface topography to back-surface thickness variations. By measuring thickness changes through the sample rather than surface profile directly, the system can determine the ion beam profile with a smaller, more manageable sample size.
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
Reduces processing time, extends sample usage without replacement, and allows for cost savings by enabling in-situ measurements without the need for large reference objects, while supporting non-orthogonal impact angles and curved samples.
Implementation Method 1
an interferometric measurement device located at least partially within the vacuum chamber and configured to direct light onto a second surface of the sample and to determine the etch rate of the ion beam or the deposition rate of the deposited material in-situ based on light reflected from the sample
Implementation Method 2
determine the etch rate of the ion beam or the deposition rate of the deposited material in-situ based on light reflected from the sample
Implementation Method 3
an ion beam source configured to direct an ion beam onto a first surface of a sample located within the vacuum chamber and to etch the first surface of the sample with an etch rate
Implementation Method 4
The ion beam is directed onto a sample's surface where the impact of the ions erodes the sample's surface, abrading away (etching) a certain amount of material
Implementation Method 5
a material source configured to deposit material onto a first surface of a sample located within the vacuum chamber with a deposition rate
Implementation Method 6
The deposition technique may be any one of chemical vapor deposition, CVD, physical vapor deposition, PVD
Data Source
AI summary
A system is provided for in-situ ion beam etch rate or deposition rate measurement, including: a vacuum chamber; an ion beam source configured to direct an ion beam onto a first surface of a sample located within the vacuum chamber and to etch the first surface of the sample with an etch rate; or a material source configured to deposit material onto a first surface of a sample located within the vacuum chamber with a deposition rate; and an interferometric measurement device located at least partially within the vacuum chamber and configured to direct light onto a second surface of the sample and to determine the etch rate of the ion beam or the deposition rate of the deposited material in-situ based on light reflected from the sample.