Multi-Spot Hyper-Spectral Reflectometry for Wafer Feature Resolution
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Solution Overview
Problem
Conventional in-situ optical reflectometers face challenges in focusing beams on substrates due to large beam sizes, making it difficult to identify and filter target features, especially in high-density semiconductor devices with small pitch sizes and deep features, which affects signal-to-noise ratio (SNR).
Innovation Solution
An optical reflectometry system with a transparent window and an optical fiber bundle that includes a lens assembly and an optical splitter to transmit and receive light, allowing for improved signal-to-noise ratio (SNR) and analysis of the full spectrum of reflected light, focusing on specific areas of the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a conventional fiber optic cable is used to transmit light from the reflectometer, then the light can be transmitted to the substrate, but the large beam size at the substrate (ranging from a few millimeters to over 10 millimeters) makes it difficult to focus the beam on the wafer and identify target features
Solution Approach 1:
The patent segments the optical fiber bundle into multiple individual optical fibers, each capable of transmitting light to a specific location on the substrate. This segmentation allows the beam to be divided into multiple smaller spots, improving spatial resolution and enabling precise targeting of specific features on the substrate surface.
Solution Approach 2:
The patent transitions from a single large beam to multiple discrete beam spots arranged in a two-dimensional array. This dimensional change from a single-point to multi-point configuration enables simultaneous measurement of multiple locations while maintaining focused, small spot sizes at each location.
2Measurement precision
If the beam size is reduced to improve spatial resolution, then target features can be better identified, but the signal-to-noise ratio (SNR) is reduced due to smaller percentage of light containing information about features
Solution Approach 1:
The patent combines the signals from multiple optical fibers that each capture light from different locations on the substrate. By merging these individual signals, the system accumulates more information about the substrate features while maintaining the spatial resolution benefits of small beam spots. This combination improves the overall signal-to-noise ratio.
Solution Approach 2:
The patent uses multiple optical fibers to create multiple copies of the measurement process at different locations on the substrate. Each fiber captures a copy of the light signal from its specific location, and these copies are then processed and combined to achieve both high spatial resolution and improved signal-to-noise ratio through statistical accumulation.
3Quantity of substance
If a large beam size is used, then more light is collected, but the reflected beam contains information from many features on the substrate that are not of interest, making target features hard to identify and filter
Solution Approach 1:
The patent segments the optical fiber bundle into multiple individual fibers, each corresponding to a specific location on the substrate. This segmentation allows the system to maintain adequate light intensity in each fiber while spatially separating the information from different regions, making it easier to identify and filter signals from target features versus non-target features.
Solution Approach 2:
The patent applies local quality by assigning different spatial regions of the substrate to different optical fibers. Each fiber is optimized to capture light from its specific local area, allowing the system to maintain high light intensity locally while improving the ability to identify and analyze specific target features by their spatial location.
4Device complexity
If conventional optical reflectometry is used with a single large beam, then the system is simpler, but it cannot provide hyper-spectral analysis with improved spatial resolution for deep, narrow features
Solution Approach 1:
The patent segments the optical measurement system into multiple optical fibers, each independently capturing light from a specific location. This segmentation enables hyper-spectral analysis with improved spatial resolution for deep, narrow features while keeping each individual fiber channel relatively simple, balancing device complexity with measurement precision.
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
Enhances the ability to determine substrate characteristics with improved spatial resolution and sensitivity, reducing the impact of non-targeted area information, thus improving the accuracy of endpoint detection in etching processes.
Implementation Method 1
an optical fiber bundle located outside of the internal volume may include at least a first optical fiber coupled to the light source and optically coupled to a lens assembly
Implementation Method 2
the lens assembly is disposed above the transparent window, and optically coupled to at least a first optical fiber, and configured to: transmit to at least one area of the substrate through the transparent window
Implementation Method 3
analyze a full spectrum of the reflected light beam, and determine at least one characteristic of the at least one area of the substrate based upon the analysis of the full spectrum
Implementation Method 4
an optical splitter disposed within the optical fiber bundle
Data Source
AI summary
An optical reflectometry system, including a processing chamber, a substrate support wherein the substrate support is configured to accept a substrate, a light source configured to transmit an incident light beam, an optical fiber bundle coupled to the light source and optically coupled to a lens assembly, wherein the lens assembly optically coupled to at least a first optical fiber, and configured to transmit to, and receive from, at least one area of the substrate through the transparent window, an optical splitter disposed within the optical fiber bundle; a return fiber bundle coupled to the optical splitter, and coupled to a detection system, wherein the detection system is configured to reference a reference light beam to a reflected light beam to improve a signal-to-noise ratio, analyze a full spectrum of the reflected light beam, and determine at least one characteristic of the at least one area of the substrate.