Photolithography Exposure Method Alignment Accuracy Throughput
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Solution Overview
Problem
The photolithography process in semiconductor manufacturing faces challenges in alignment accuracy and throughput, particularly due to the limitations of conventional exposure apparatuses that cannot simultaneously conduct wafer alignment and photoresist exposure, leading to low alignment accuracy and reduced production efficiency as device integration increases.
Innovation Solution
An exposure method that involves a precise alignment step using an off-line alignment tool followed by a coarse alignment step using the exposure apparatus, with data comparison and feedback for calibration, allowing for independent operation of the alignment tool and exposure apparatus to enhance alignment accuracy and throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional exposure apparatus conducts wafer alignment and photoresist exposure sequentially, then alignment accuracy can be maintained, but throughput is significantly reduced
Solution Approach 1:
The patent divides the alignment function into two independent parts: a dedicated alignment tool for high-precision alignment and an exposure apparatus for photoresist exposure. This segmentation allows both functions to operate simultaneously on different wafers, resolving the contradiction between maintaining alignment accuracy and improving throughput.
Solution Approach 2:
The patent introduces an intermediary data comparison and calibration system that bridges the alignment tool and exposure apparatus. The alignment tool provides alignment data, which is compared and used to calibrate the exposure apparatus, ensuring accurate pattern transfer while enabling parallel operation and high throughput.
2Measurement precision
If multiple alignment marks are measured on the same wafer to improve alignment accuracy, then alignment precision increases, but the time required for alignment increases
Solution Approach 1:
The patent performs preliminary high-precision alignment measurements on a first batch of wafers using the alignment tool before exposing the second batch. This preliminary action establishes accurate calibration data that can be used for subsequent exposure operations, reducing the time needed for alignment on each individual wafer while maintaining high alignment accuracy.
Solution Approach 2:
The patent enables continuous operation by having the alignment tool work on one batch of wafers while the exposure apparatus simultaneously exposes another batch. This continuity eliminates idle time and ensures that alignment measurements are performed without interrupting the production flow, maintaining both accuracy and efficiency.
3Ease of manufacture
If alignment is conducted on a single wafer as a base for calibrating the exposure apparatus, then the calibration process is simplified, but alignment accuracy deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where alignment data from multiple wafers processed by the alignment tool is collected, compared, and used to calibrate the exposure apparatus. This feedback loop ensures that the calibration is based on comprehensive data from multiple samples rather than a single wafer, improving alignment accuracy while maintaining calibration simplicity through automated data processing.
Solution Approach 2:
The patent creates a copy of the alignment data from the alignment tool and uses it to calibrate the exposure apparatus. This copying approach allows the calibration process to utilize comprehensive alignment data from multiple wafers without requiring the exposure apparatus to directly measure each wafer, thereby improving accuracy while keeping the calibration process simple and efficient.
Data Source
AI summary
An exposure method suitable for a photolithography process is described. First, a wafer with a group of alignment marks formed thereon is provided. A first alignment step is conducted by using the group of the alignment marks on the wafer to obtain a first calibration data. Next, a second alignment step is conducted by using a portion of the group of alignment marks on the wafer to obtain a second calibration data. The first calibration data is then compared with the second calibration data to obtain a comparison result. Next, a photoresist exposure step is conducted on the wafer according to the comparison result.