Focused Beam Interference for Sample Thickness Variation Metrology
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Solution Overview
Problem
In substrate processing systems, maintaining uniformity and precision in sample thickness is challenging due to uncontrolled thickness variations, which can affect material properties and quality, especially in semiconductor manufacturing where small deviations can lead to defects and impurities.
Innovation Solution
A method and system utilizing focused beam interference patterns to detect and measure thickness variations by directing a focused beam to multiple locations on a sample, analyzing interference patterns formed by light reflected from both surfaces, and determining the magnitude and sign of thickness differences, enabling precise thickness metrology and quality control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical inspection methods are used to measure sample thickness, then the measurement process is simple, but the measurement precision is insufficient to detect small thickness variations
Solution Approach 1:
The patent applies optical vibration/oscillation by directing a focused beam that scans or oscillates across the sample surface, creating time-varying interference patterns that encode thickness information. This dynamic measurement approach enables detection of small thickness variations through phase modulation of the interference signal.
Solution Approach 2:
The patent utilizes phase transitions in the optical domain by analyzing phase changes in interference patterns. The phase difference between light waves reflected from different sample locations provides precise thickness measurements, leveraging optical phase information rather than just intensity measurements.
Solution Approach 3:
The patent introduces an intermediary reference beam that interferes with the beam reflected from the sample. This reference beam serves as a mediator, creating an interference pattern that encodes thickness information in a measurable form, enabling precision measurements through the interference of two coherent light waves.
2Reliability
If robotic techniques are used for sample manipulation and inspection, then chamber isolation is maintained, but the precision and reliability of measurements are compromised
Solution Approach 1:
The patent replaces mechanical contact-based thickness measurement methods with non-contact optical interferometry. By using light waves instead of mechanical probes, the system achieves higher reliability and precision while maintaining chamber isolation, eliminating the need for complex robotic manipulation of measurement instruments.
Solution Approach 2:
The patent uses light as an intermediary to transfer measurement information from the sample to the detector without physical contact. This optical intermediary enables reliable measurements through vacuum or atmospheric paths, maintaining chamber isolation while achieving high measurement precision through interference pattern analysis.
3Measurement precision
If focused beam interference is used to measure thickness variations, then measurement precision is improved, but the difficulty of detecting and measuring increases
Solution Approach 1:
The patent employs oscillating or scanning focused beams that create dynamic interference patterns. The time-varying nature of these patterns provides multiple measurement samples and enables frequency-based signal processing techniques that simplify extraction of thickness information from complex interference data.
Solution Approach 2:
The patent implements feedback mechanisms where the detected interference patterns are processed to generate thickness measurements, which can then be used to adjust measurement parameters or provide real-time quality control feedback. This closed-loop approach simplifies the measurement process by using the measured data to optimize subsequent measurements.
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 allows for accurate detection of thickness variations and uniformity, enabling real-time correction of processing errors and improving sample quality by identifying whether thickness is increasing or decreasing, thus enhancing the precision and reliability of semiconductor manufacturing.
Implementation Method 1
detecting a first interference pattern (IP) associated with a first light departing from the first location and generated upon interaction of the first focused beam with the sample
Implementation Method 2
light departing from the first location and generated upon interaction of the first focused beam with the sample
Data Source
AI summary
Disclosed systems and techniques are directed to interferometry-based sample thickness metrology in manufacturing systems. For example, the disclosed techniques include directing a focused beam to a plurality of locations of a sample and detecting an interference pattern (IP) associated with a light departing from the respective location and generated upon interaction of the focused beam with the sample. The techniques further include determining, based on a first IP associated with a first light departing from a first location and a second IP associated with a second light departing from a second location, a magnitude and a sign of a difference between a first thickness of the sample at the first location and a second thickness of the sample at the second location.