Imaging Reflectometry Sensitivity via Multi-Wavelength Pixel Integration
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Solution Overview
Problem
Imaging reflectometry systems face limitations in measurement sensitivity due to the full well capacity of image sensors, which restricts the number of electrons that can be held by each pixel, making it difficult to distinguish between similar features or characteristics in samples.
Innovation Solution
The method involves combining reflectometry measurements from pixels associated with a particular structure across multiple images, effectively increasing the number of electrons without exceeding the full well capacity, by using multiple input beams with different peak wavelengths and determining representative reflectance intensity values to enhance measurement sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of electrons in each pixel is increased to increase the signal, then the signal-to-noise ratio is improved, but the full well capacity of the pixel is exceeded causing saturation
Solution Approach 1:
The patent segments the measurement process into multiple separate images taken at different times. Instead of attempting to capture all necessary electrons in a single pixel exposure, the measurement is divided into multiple frames, each capturing a portion of the total signal. These segmented measurements are then combined computationally to achieve the desired total electron count while avoiding saturation in any individual pixel exposure.
2Measurement precision
If multiple images are combined to increase the number of electrons, then the signal-to-noise ratio is improved, but the measurement time is increased
Solution Approach 1:
The patent employs periodic action by capturing multiple images in rapid succession at a high frame rate. The illumination is applied periodically, and the sensor captures reflected light in discrete periodic intervals. By using periodic illumination and periodic capture, the system efficiently accumulates signal over multiple periods while minimizing the total measurement time through high-speed sequential imaging.
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 significantly improves the signal-to-noise ratio and measurement sensitivity, allowing for more accurate identification of features such as film thickness and critical dimensions by averaging reflectance intensity values across multiple images.
Implementation Method 1
receiving portions of the first input beam reflected from the sample at an imaging sensor
Implementation Method 2
obtaining multiple first images of the measurement area using the portions of the first input beam reflected from the sample and received at the imaging sensor
Data Source
AI summary
Methods for performing imaging reflectometry measurements include illuminating a measurement area on a sample using an input beam having a first peak wavelength, and obtaining multiple images of the measurement area using portions of the input beam reflected from the sample. A reflectance intensity value is determined for each of a plurality of pixels in each of the images. A parameter associated with the particular structure is determined using the reflectance intensity value.