Focus Error Sensors in Lithography Metrology
Solution Overview
Problem
Conventional photolithography methods face challenges in accurately measuring focus errors during production due to interference from existing circuit patterns and topography, leading to potential device defects and decreased yield.
Innovation Solution
A method involving the formation of photoresist patterns with blocking scheme patterns to create sensor windows for focus error sensors, allowing for precise measurement of focus errors using phase-shift focus monitors and overlay metrology techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional photolithography imaging is performed, then device patterns are transferred to photoresist with high throughput, but focus errors cannot be accurately measured due to interference from existing circuit patterns and topography
Solution Approach 1:
The substrate is divided into device regions and sensor regions. Focus error sensors are placed in specific sensor windows that are separated from the device patterns, allowing independent measurement of focus errors without interference from circuit patterns. This spatial segmentation enables accurate focus metrology while maintaining device production.
Solution Approach 2:
Focus error sensors act as intermediary elements between the imaging system and the measurement system. These sensors are formed in sensor windows and provide a dedicated structure for measuring focus errors without being part of the actual device patterns, thereby mediating between the photolithography process and the metrology process.
2Measurement precision
If focus error sensors are integrated into device regions, then focus errors can be measured, but device functionality is compromised
Solution Approach 1:
The substrate is divided into device regions and sensor regions. Focus error sensors are placed in specific sensor windows that are separated from the device patterns, allowing independent measurement of focus errors without interference from circuit patterns. This spatial segmentation enables accurate focus metrology while maintaining device production.
3Measurement precision
If traditional metrology techniques are used, then focus errors can be measured, but they cannot be incorporated into production flow due to interference from existing patterns
Solution Approach 1:
The focus error sensing capability is merged with the device fabrication process. Focus error sensors are formed in the same photolithography steps that create device patterns, using the same photoresist and processing conditions. This integration allows focus metrology to be incorporated into the production flow without requiring separate metrology tools or additional processing steps.
Solution Approach 2:
The photolithography process is given multiple functions: it simultaneously creates device patterns and forms focus error sensors in sensor windows. This multi-functionality allows the same imaging equipment and process conditions to be used for both device fabrication and focus metrology, enabling production flow integration.
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
Enables accurate determination and mapping of focus errors across the substrate, improving focus control and reducing defects by integrating focus error sensing into the production flow without rendering devices inoperable.
Implementation Method 1
Such PSFM techniques employ phase shift technology to translate focus errors into easily measurable overlay shifts in the PSFM patterns
Data Source
AI summary
The present application is directed to a method for determining photolithography focus errors during production of a device. The method comprises providing a substrate and forming a photoresist pattern on the substrate. The photoresist pattern comprises a device pattern and one or more blocking scheme patterns. The process further comprises performing a device manufacturing process using the photoresist pattern as a mask to form sensor windows on the substrate. One or more focus error sensors are formed in the sensor windows. Focus errors are determined using the focus error sensors. Other embodiments of the present application are directed to wafers comprising one or more focus error sensors positioned in sensor windows.