Maskless Lithography Alignment via Mirror Array Illumination
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Solution Overview
Problem
Current microlithography techniques face challenges in achieving accurate alignment of layers due to measurement errors in identifying the location of alignment marks on substrates, which affects the precision of electrical feature placement.
Innovation Solution
A method and system utilizing a mirror array with non-adjacent mirrors in a maskless lithography system, where light is directed from specific mirror configurations to capture images of the substrate, allowing for accurate determination of alignment mark locations by using different wavelengths and image processing to reduce measurement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional illumination methods are used to capture images of alignment marks, then the imaging process is simple and fast, but measurement precision of alignment mark location deteriorates due to illumination incoherence causing errors
Solution Approach 1:
The illumination system is segmented into multiple independent light sources, each providing coherent illumination from a different angle. Instead of using a single complex coherent light source, the system divides the illumination task across multiple simpler light sources (LEDs or lasers) positioned at different locations, thereby achieving coherent illumination effects while maintaining system simplicity
Solution Approach 2:
A beam combining optics system acts as an intermediary to combine the light from multiple independent light sources into a single coherent illumination pattern on the substrate. This intermediary component enables the system to achieve coherent illumination without requiring a single complex coherent light source, thus improving measurement precision while managing device complexity
2Measurement precision
If coherent illumination is used to improve alignment mark location accuracy, then measurement precision improves, but device complexity increases due to requirements for coherent light sources and beam combining optics
Solution Approach 1:
The coherent illumination requirement is segmented into multiple incoherent light sources that individually provide partial illumination. Each light source (LED or laser) is simpler than a single coherent source would be, and their combined effect through beam combining optics achieves the desired coherent illumination pattern for high-precision alignment mark location measurement
Solution Approach 2:
The system changes the parameter of light coherence by using multiple incoherent light sources positioned at specific angles rather than requiring a single coherent source. This parameter change approach, combined with beam combining optics, achieves coherent illumination effects while using simpler, more manageable light source components
3Measurement precision
If multiple light sources are used to provide coherent illumination, then alignment accuracy improves, but energy consumption increases
Solution Approach 1:
The multiple light sources operate in a periodic or sequential manner rather than continuously simultaneously. The system can activate different light sources in sequence or use them periodically to provide the necessary coherent illumination for alignment measurements, reducing overall energy consumption while maintaining measurement precision when needed
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 enhances the accuracy of layer alignment by reducing measurement errors, ensuring precise placement of electrical features and improving the quality of electrical interconnections.
Implementation Method 1
a mirror array that is adapted to have a configuration of non-adjacent mirrors, to receive light from the light source and is adapted to reflect light towards a substrate layer
Implementation Method 2
A beam splitter is adapted to receive the light reflected from the mirror array and light reflected from the substrate layer
Implementation Method 3
A camera is coupled to the beam splitter and is adapted to capture and accumulate images on the substrate layer that is visible due to the light reflected from the substrate layer
Data Source
AI summary
Methods and apparatuses are provided that determine an offset between actual feature/mark locations and the designed feature/mark locations in a maskless lithography system. For example, in one embodiment, a method is provided that includes opening a camera shutter in a maskless lithography system. Light is directed from a configuration of non-adjacent mirrors in a mirror array towards a first substrate layer. An image of the first substrate layer on a camera is captured and accumulated. Light is directed and images are captured repeatedly using different configurations of non-adjacent mirrors to cover an entire field-of-view (FOV) of the camera on the first substrate layer. Thereafter, the camera shutter is closed and the accumulated image is stored in memory.