EUV Mask Inspection Using TDI Sensor Scanning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing mask inspection methods struggle to accurately predict the imaging result of EUV masks due to deviations in wavelength and the challenge of managing large image fields with EUV radiation, leading to defects being misidentified or overlooked, and reduced resolution.
Innovation Solution
A method and device for mask inspection using a sensor arrangement with TDI sensors, where sensor images are combined in a scanning operation to form an image, optimizing geometric arrangements to maximize active sensor area coverage and ensure accurate imaging results, even at EUV wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If DUV wavelength inspection is used, then mask inspection can be performed with available technology, but the imaging result prediction accuracy deteriorates due to significant wavelength deviation from actual EUV operation
Solution Approach 1:
The patent changes the wavelength parameter from DUV (248nm or 193nm) to EUV (13.5nm) to match the actual lithography process conditions. This parameter change enables accurate prediction of imaging results while maintaining mask inspection capability through specialized EUV optical systems and sensors
2Measurement precision
If EUV wavelength inspection is used, then imaging result prediction accuracy is improved, but the image field size becomes excessively large and cannot be concentrated onto available sensors
Solution Approach 1:
The patent segments the large EUV image field into multiple smaller sub-fields that can be captured by available sensors. This is achieved through a scanning system that sequentially images different regions of the mask and combines them to form a complete inspection image, making the large image field manageable while maintaining EUV wavelength inspection accuracy
3Use of energy by moving object
If plasma light source is used for EUV generation, then EUV radiation can be produced, but the radiation cannot be concentrated onto small image field without light loss due to etendue conservation
Solution Approach 1:
The patent employs a dynamic scanning system where the illumination field and sensor position are coordinated to sequentially scan across the mask. This dynamic approach allows the use of a larger illumination field with plasma source while maintaining efficient light utilization, as the field is swept across the mask area rather than requiring simultaneous concentration onto a small static sensor area
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 accurate and reliable mask inspection by aligning inspection conditions with actual lithography processes, overcoming issues of large image fields and wavelength deviations, ensuring defects are correctly identified and resolution is maintained.
Implementation Method 1
sensor images captured by TDI sensors are combined in a scanning operation to form an image
Implementation Method 2
sensor arrangement with TDI sensors... sensor images captured by each of the individual sensors
Implementation Method 3
an object field situated in an object plane and illuminated with EUV radiation... is imaged by a projection lens onto an image field situated in an image plane
Implementation Method 4
the EUV radiation then typically generated by way of a plasma light source in the device for mask inspection
Data Source
AI summary
A method and a device for mask inspection, wherein the mask is designed for operation in reflection at an operating wavelength of less than 30 nm and is intended to be illuminated in a lithography process in a projection exposure apparatus for exposing a wafer. In an exemplary method, an object field situated in an object plane (OP) and illuminated with EUV radiation having a wavelength of less than 30 nm by way of an illumination system is imaged by a projection lens onto an image field situated in an image plane (IP), wherein a sensor arrangement (having a plurality of sensors is situated in the image plane, wherein the mask is guided over the object field in the object plane in a scanning operation, and wherein an image of the mask is formed by combining sensor images captured by each of the individual sensors in the scanning operation.