EUV Droplet Trajectory Control via Shutter-Isolated Imaging
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Solution Overview
Problem
Current EUV light generation systems face challenges in accurately controlling the trajectory of droplets during plasma generation, as image capturing near the plasma generation region often results in plasma light interference, making it difficult to calculate the actual trajectory position of the droplet.
Innovation Solution
A target image-capture device with a droplet detector, illumination light source, image capturing element, shutter device, and controller is used to capture images of droplets before they reach the plasma generation region, allowing for multiple exposure and trajectory control without capturing plasma light, thereby improving accuracy and stability during EUV light generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If image capturing is performed near the plasma generation region to measure droplet trajectory, then trajectory measurement capability is improved, but plasma light interference increases making accurate trajectory calculation difficult
Solution Approach 1:
The harmful plasma light is extracted and removed from the optical path by positioning the image capturing element to capture images before the droplet reaches the plasma generation region. The shutter device is used to block plasma light during plasma generation, effectively separating the measurement function from the harmful plasma radiation.
Solution Approach 2:
The image capturing element captures images of the droplet before it reaches the plasma generation region, performing the measurement action in advance before the harmful plasma light is generated. This preliminary capturing allows trajectory measurement without interference from subsequent plasma light emission.
2Measurement precision
If multiple exposure is performed to improve trajectory control accuracy, then measurement precision is improved, but the complexity of the image capturing system increases
Solution Approach 1:
Multiple exposure images are acquired at different time points as the droplet moves through the measurement region. The controller periodically captures images at optimized intervals, and the trajectory is calculated by analyzing the sequence of droplet positions across these periodic exposures, improving accuracy without requiring complex hardware modifications.
Solution Approach 2:
The controller acts as an intermediary that coordinates the shutter device and image capturing element to manage multiple exposure sequences. It processes the captured images to calculate droplet trajectory, serving as a software-based mediator that reduces the need for additional complex hardware components.
3Productivity
If the shutter remains open during plasma generation to capture real-time images, then image capturing capability is improved, but plasma light damages the image capturing element
Solution Approach 1:
The image capturing element captures images in advance before plasma generation occurs. The shutter device is closed during plasma generation to block harmful plasma light, protecting the image capturing element while maintaining the ability to acquire trajectory data through preliminary imaging.
Solution Approach 2:
The plasma light, which would normally damage the image capturing element, is converted into a protective signal by using the shutter device to block it. This allows the system to maintain real-time monitoring capability while using the plasma generation event itself as a trigger to close the shutter and protect the sensor.
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 enables precise trajectory control of droplets, ensuring stable plasma generation at the desired position, even during burst light emission periods, thereby enhancing the operational stability of the EUV light generation device.
Implementation Method 1
The image capturing element is configured to receive reflected light from the droplet, the reflected light being caused by the droplet being irradiated with the illumination light
Implementation Method 2
The illumination light source is configured to radiate illumination light to the droplet detected by the droplet detector
Implementation Method 3
a target supplied to a plasma generation region is made into plasma by being irradiated with laser light
Implementation Method 4
a target supplied to a plasma generation region is made into plasma by being irradiated with laser light, and extreme-ultraviolet-light is generated
Implementation Method 5
extreme-ultraviolet-light is generated
Implementation Method 6
The shutter may be configured to switch between propagation and cutoff of light including the reflected light to the image capturing element
Data Source
AI summary
A target image-capture device may be configured to capture an image of a target that is made into plasma when irradiated with laser light and generates extreme-ultraviolet-light. The target image-capture device may include a droplet detector configured to detect passage of a droplet output as the target, and output a detection signal, an illumination light source, an image capturing element, a shutter device, and a controller configured to output, to the image capturing element, an exposure signal allowing the image capturing element to perform image capturing, and output, to the shutter device, a shutter open/close signal allowing a shutter to perform an open and close operation upon input of the detection signal. The controller may output the shutter open/close signal to the shutter device to make the shutter closed during when the droplet is irradiated with the laser light so that the plasma is generated.