Lithography Substrate Imaging With Diffractive Pupil Focus Capture
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Solution Overview
Problem
Existing methods for measuring substrates in semiconductor lithography, such as photomasks, are inefficient in determining defocusing information and require multiple image captures to achieve sharp focus, leading to reduced throughput.
Innovation Solution
A device and method utilizing a diffractive element in the imaging optical unit to create multiple partial imagings of the substrate, allowing a single capture to provide defocusing information equivalent to multiple captures, with features like amplitude and phase gratings, locally varying periods, and aberration correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a focus stack is produced by moving the measuring table to capture multiple images at different z positions, then defocusing information and focus determination are improved, but measurement time and throughput are worsened
Solution Approach 1:
The patent applies segmentation by dividing the imaging process into multiple partial imagings within a single capture. The diffractive element creates multiple diffracted beams that form separate partial imagings of the substrate at different focal planes simultaneously, replacing the need to move the measuring table through multiple z positions and capture separate images.
Solution Approach 2:
The patent transitions from temporal/movement-based focus stacking (capturing images sequentially at different z positions) to spatial-based focus stacking (capturing multiple imagings simultaneously at different focal planes). The diffractive element maps different focal planes to different spatial positions in the image plane, enabling parallel measurement of multiple focus positions in a single capture.
2Measurement precision
If multiple individual images are recorded for different z positions, then focus determination is improved, but the number of test measurements and time required increase
Solution Approach 1:
The patent merges multiple focus position measurements into a single capture operation. The diffractive element causes the imaging optical unit to simultaneously record multiple partial imagings at different focal planes in one test measurement, eliminating the need for sequential measurements and reducing total test time while maintaining comprehensive focus determination capability.
Solution Approach 2:
The diffractive element is pre-configured in the imaging optical unit to automatically generate multiple focal plane imagings before the measurement process begins. This preliminary setup enables the system to capture focus information across multiple z positions without requiring subsequent mechanical movement or additional testing steps.
3Productivity
If a diffractive element is used to create multiple partial imagings, then throughput is improved, but device complexity increases
Solution Approach 1:
The diffractive element creates multiple copies (partial imagings) of the substrate in a single capture operation. By diffracting the incident light into multiple beams, the element generates replicated images at different focal planes simultaneously, enabling parallel measurement without requiring multiple separate measurement systems or complex mechanical positioning mechanisms.
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 imaging quality and throughput by reducing the need for mechanical movement of the substrate, minimizing image crosstalk, and enabling rapid focus determination with improved accuracy.
Implementation Method 1
a diffractive element being arranged in the pupil of the imaging optical unit. The arrangement of a diffractive element causes the imaging of the substrate to be multiplied and transformed into a number of partial imagings because of diffractive effects
Data Source
AI summary
The invention relates to a device for measuring a substrate for semiconductor lithography, comprising an illumination optical unit, an imaging optical unit and a recording device arranged in the image plane of the imaging optical unit, a diffractive element being arranged in the pupil of the imaging optical unit.The invention also relates to a method for measuring a substrate for semiconductor lithography with a measuring device, the measuring device comprising an imaging optical unit with a pupil, with the following method steps: arranging a diffractive element in the pupil of the imaging optical unit for producing a multifocal imaging, capturing the imaging of a partial region of the substrate, and evaluating the imaging.