Position Detection Method for Semiconductor Alignment Marks
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Solution Overview
Problem
The semiconductor industry faces challenges in achieving high alignment accuracy and throughput due to scattering alignment marks caused by processes like chemical mechanical polishing, leading to reduced signal strength and increased errors from wafer-induced shifts and tool-induced shifts, which conventional signal processing methods struggle to fully address.
Innovation Solution
A position detecting method that selects and uses positional information with predetermined precision from multiple mark elements to calculate the object's position, eliminating inaccurate information and preventing measurement errors caused by wafer-induced shifts, thereby improving alignment accuracy without compromising throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional signal processing methods are used to detect alignment mark positions, then the measurement process is simple, but alignment accuracy deteriorates due to scattering alignment marks and wafer-induced shifts
Solution Approach 1:
The alignment mark is divided into multiple mark elements (e.g., four rectangular marks), and positional information is obtained for each element separately. This segmentation allows selective use of precise positional information while eliminating inaccurate data from scattered or distorted elements, thereby improving alignment accuracy without requiring complex processing of the entire alignment mark
Solution Approach 2:
Different mark elements are evaluated individually for their positional information quality. The method selectively uses positional information from mark elements that meet predetermined precision criteria, while discarding or correcting information from elements affected by scattering or wafer-induced shifts. This local quality assessment approach maintains high alignment accuracy without requiring complex global processing
2Measurement precision
If all positional information from multiple mark elements is used to calculate object position, then measurement throughput is high, but measurement precision deteriorates due to inclusion of inaccurate information from scattered alignment marks
Solution Approach 1:
The method extracts and selects only the precise positional information from mark elements that meet predetermined accuracy criteria. Inaccurate positional information from scattered or distorted mark elements is eliminated through selection based on precision thresholds, ensuring that only reliable data contributes to the final position calculation, thereby maintaining both accuracy and throughput
Solution Approach 2:
The method changes the parameter selection criterion from using all positional information to using only positional information that satisfies predetermined precision requirements. This parameter-based filtering approach dynamically selects reliable measurements while excluding inaccurate ones, resolving the contradiction between measurement precision and productivity
3Manufacturing precision
If alignment mark CD is reduced to match fine circuit patterns, then resolution improves, but signal strength decreases and alignment accuracy deteriorates
Solution Approach 1:
The alignment mark is segmented into multiple distinct mark elements arranged in a specific pattern. This segmentation allows the use of larger overall alignment mark dimensions (maintaining signal strength) while creating multiple measurable elements that can be processed to achieve high alignment precision, thus resolving the contradiction between resolution requirements and signal strength
Data Source
AI summary
There is provided a position detecting method for detecting a position of an object, on which an alignment mark including plural mark elements is formed. The method includes the steps of obtaining positional information indicative of each position of the plural mark elements, selecting positional information that has predetermined precision among plural pieces of positional information obtained by the obtaining step, and calculating the position of the object using the positional information that has the predetermined precision selected by the selecting step.