Multi-Angle Ellipsometry Optics for Small-Feature Metrology
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Spectroscopic ellipsometry systems face challenges in decoupling target characteristics due to correlated data, limited spot sizes, and inadequate angle ranges, which hinder accurate measurement of small features and sensitivity in semiconductor metrology.
Innovation Solution
The system employs configurable optics for simultaneous measurement at multiple angles of incidence and azimuth angles, using bright light sources and polarization state generating/analyzing components, along with apodizers and adjustable apertures to improve measurement repeatability and stability, allowing for small spot sizes and high sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional single-angle ellipsometry is used, then the system is simple, but measurement precision and sensitivity are insufficient for small features
Solution Approach 1:
The patent segments the measurement process by performing ellipsometry at multiple discrete angles of incidence (e.g., 45°, 55°, 65°, 75°) rather than a single angle. This segmentation of the angular space allows extraction of more independent target characteristics, improving measurement precision for small features while maintaining manageable system complexity through modular optical design
Solution Approach 2:
The patent adds the angular dimension to the measurement space by varying the angle of incidence across multiple discrete values. This dimensional expansion transforms the measurement from a single-point sampling to a multi-point angular sweep, enabling decoupling of correlated target parameters and enhancing sensitivity to small feature dimensions
2Reliability
If multiple angles of incidence are measured simultaneously, then sensitivity and data decoupling improve, but device complexity increases
Solution Approach 1:
The patent employs periodic action by sequentially measuring at multiple discrete angles of incidence in a repeating cycle. The system acquires ellipsometry data at each angle, processes it, then moves to the next angle in the sequence. This periodic angular sampling provides sufficient data decoupling over time while avoiding the complexity of simultaneous multi-angle detection systems
Solution Approach 2:
The patent introduces dynamic angular adjustment capability, allowing the system to change the angle of incidence between measurements. This dynamic reconfiguration of the optical path enables the system to adapt to different measurement requirements and achieve data decoupling through temporal separation of angular measurements rather than spatial complexity
3Measurement precision
If spot size is reduced for small feature measurement, then measurement accuracy improves, but signal intensity decreases
Solution Approach 1:
The patent maintains continuity of useful action by performing multiple measurements at different angles at the same small spot location. Rather than spreading the measurement over a larger area, the system accumulates angular-dependent signal information at the confined spot, thereby maintaining measurement accuracy for small features while building sufficient signal intensity through multi-angle data accumulation
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 configuration enables improved measurement accuracy and stability, particularly for small features, by breaking correlations in data and enhancing sensitivity through simultaneous multi-angle and multi-wavelength analysis.
Implementation Method 1
a polarization state generating component (110) configured to provide different polarization states for the illumination beam
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
An apparatus includes (i) a bright light source for providing an illumination beam at multiple wavelengths selectable with a range from a deep ultraviolet wavelength to an infrared wavelength, (ii) illumination optics for directing the illumination beam towards a sample at selectable sets of angles of incidence (AOI's) or azimuth angles (AZ's) and polarization states to provide spectroscopic ellipsometry, wherein the illumination optics include an apodizer for controlling a spot size of the illumination beam on the sample at each of the selectable AOI/AZ sets, (iii) collection optics for directing an output beam from the sample in response to the illumination beam at each of the selectable AOI/AZ sets and polarization states towards a detector that generates an output signal or image based on the output beam, and (v) a controller for characterizing a feature of the sample based on the output signal or image.