Compensating Light Beam for Wafer Peripheral Dose Uniformity
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Solution Overview
Problem
The lithography process in semiconductor manufacturing faces challenges in achieving uniform after-etch-inspection critical dimension (AEICD) due to the loading effect, which causes variations in etching rates between the die regions near the wafer's center and periphery.
Innovation Solution
An exposure method involving a wafer covered with a photoresist layer, where a compensating light beam with a first dose is directed onto the peripheral region, and a patterned light beam with a second dose is projected in a step-and-scan manner, ensuring the total dose exceeds the exposure threshold, thereby compensating for the loading effect and achieving uniform AEICD.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional exposure method is used, then the lithography process can be completed, but the AEICD varies in die regions located in different positions of the wafer due to loading effect
Solution Approach 1:
The patent applies local quality by directing a compensating light beam specifically to the peripheral region of the wafer with a different dose than the center region. This creates a non-uniform dose distribution that compensates for the loading effect, ensuring that die regions in both the center and periphery achieve uniform AEICD after etching.
Solution Approach 2:
The patent changes the exposure dose parameter spatially across the wafer surface. By adjusting the light beam dose to be higher in the peripheral region compared to the center region, the method compensates for the loading effect and achieves consistent AEICD uniformity across different wafer positions.
2Manufacturing precision
If compensating light beam is directed onto peripheral region, then AEICD uniformity is improved, but the exposure process complexity increases
Solution Approach 1:
The patent segments the wafer surface into different regions (center region and peripheral region) and applies different exposure doses to each segment. The compensating light beam is directed specifically at the peripheral region, creating a segmented exposure approach that improves AEICD uniformity while managing process complexity through regional differentiation.
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
The method effectively corrects the variation in AEICD by ensuring uniform dose distribution across the wafer, reducing the impact of the loading effect and resulting in consistent critical dimensions after etching.
Implementation Method 1
a compensating light beam having a first dose is directed onto the photoresist layer within the peripheral region
Implementation Method 2
the photoresist layer in the die region is exposed
Data Source
AI summary
An exposure method is disclosed. A wafer coated with a photoresist layer having an exposure threshold dose is provided. The wafer has at least a central region and a peripheral region. Then, a compensating light beam having a first dose directs on the photoresist layer within the peripheral region. Next, a patterned light beam having a second dose is then projected, in a step-and-scan manner, onto the photoresist layer, thereby exposing the photoresist layer. The total dose of the first energy and the second energy is above than the exposure threshold dose.