Wavelength Selection for Substrate Alignment Mark Detection
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Solution Overview
Problem
In three-dimensional structure memories, the increasing number of stacked layers complicates the detection of alignment marks on lower layers, making it difficult to achieve high overlay accuracy during lithography processes, as the thickness of the layered body grows, affecting the contrast and diffraction light intensity measurements.
Innovation Solution
A substrate measurement system that includes a light exposure apparatus and a control device using wavelength selection reference information to optimize signal light intensity by selecting the appropriate wavelength for alignment, facilitating the detection of alignment marks on lower layers through a computer program product that measures film thickness and generates alignment instructions based on signal light intensity variations with respect to different wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of stacked layers is increased to achieve larger memory capacity, then the memory capacity is improved, but the detection of alignment marks on lower layers becomes more difficult
Solution Approach 1:
The patent applies parameter changes by adjusting the wavelength of light used for alignment mark detection. When the number of stacked layers increases, the patent selects a longer wavelength to penetrate through the thicker layered structure, maintaining detection capability despite increased complexity. This resolves the contradiction by changing the measurement parameter (wavelength) to adapt to the increased layer count.
2Length of stationary object
If the thickness of the layered body increases with more stacked layers, then the memory capacity is improved, but the contrast and diffraction light intensity for alignment measurement deteriorate
Solution Approach 1:
The patent changes the wavelength parameter to compensate for increased layered body thickness. By selecting an appropriate wavelength from multiple available wavelengths, the system optimizes light penetration and reflection characteristics, maintaining sufficient contrast and diffraction intensity for accurate alignment measurement even through thick multi-layer structures.
3Measurement precision
If the measurement conditions, mark design, and film structure are optimized to attain high contrast or diffraction light intensity, then the alignment measurement precision is improved, but the process complexity increases
Solution Approach 1:
The patent simplifies the overall process by implementing wavelength selection as the primary optimization parameter. Rather than requiring simultaneous optimization of mark design, film structure, and measurement conditions, the system achieves high measurement precision by selectively adjusting the wavelength parameter based on the number of stacked layers, reducing process complexity while maintaining accuracy.
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 allows for improved detection of alignment marks on lower layers by selecting the wavelength that provides the highest signal light intensity, enhancing overlay accuracy and simplifying the alignment process even with thick processing objects, thereby facilitating the production of three-dimensional structure memories.
Implementation Method 1
selecting a wavelength that provides a highest degree of intensity of signal light reflected when the signal light is incident onto the processing object
Implementation Method 2
obtain a value of a film thickness of a processing object disposed above a substrate
Implementation Method 3
The diffraction light measurement is a measuring method of performing evaluation based on a change in diffraction light intensity obtained by scanning a mark with laser light
Data Source
AI summary
According to one embodiment, a value of a film thickness of a processing object disposed above a substrate is obtained. Then, a wavelength that provides a highest degree of intensity of signal light reflected when the signal light is incident onto the processing object having the value of the film thickness, based on wavelength selection reference information is selected. Then, a first instruction performing an alignment process to the substrate by use of signal light having a wavelength thus selected is generated. The wavelength selection reference information is information that includes a correlation between values of the film thickness of the processing object and degrees of intensity of the signal light, with respect to a plurality of wavelengths.