Photolithography Alignment Mark Grating Structures for Overlay Shift Compensation
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Solution Overview
Problem
Current photolithography alignment techniques in semiconductor manufacturing face challenges with increasing feature sizes, leading to alignment errors and reduced registration accuracy due to overlay shifts during double exposure type double patterning processes, affecting the precision and performance of semiconductor structures.
Innovation Solution
A photolithography alignment mark structure is formed with multiple gratings on a semiconductor substrate, using grating diffraction to determine alignment centers, and adjusting the alignment centers for subsequent exposures to compensate for overlay shifts, thereby improving alignment accuracy and registration precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If grating diffraction is used to determine alignment centers in double exposure type double patterning process, then alignment centers can be obtained for mask plate positioning, but overlay shifts occur leading to alignment errors and reduced registration accuracy
Solution Approach 1:
The invention divides the alignment mark structure into multiple gratings (first grating, second grating, third grating, fourth grating) with different orientations and positions. Each grating serves a specific alignment function, allowing separate measurement and compensation of overlay shifts in different directions, thereby improving overall registration accuracy while maintaining alignment center detection capability
Solution Approach 2:
The invention changes the physical parameters of the alignment mark structure by creating gratings with different grating constants and orientations. The first and second gratings have different grating constants along the first direction, while the third and fourth gratings have different grating constants along the second direction. This parameter variation enables differential measurement of overlay shifts and improves registration precision
2Manufacturing precision
If multiple gratings with different grating constants are used, then overlay shifts can be compensated to improve registration accuracy, but the alignment mark structure becomes more complex
Solution Approach 1:
The invention makes the alignment mark structure multi-functional by designing it to simultaneously perform alignment center determination and overlay shift compensation. The multiple gratings serve dual purposes: establishing reference alignment centers and measuring overlay errors, thereby improving registration accuracy without requiring separate alignment and measurement systems
Solution Approach 2:
The invention embeds multiple gratings within a single alignment mark structure on the substrate. The first, second, third, and fourth gratings are nested together in a compact arrangement, allowing the complex multi-grating structure to be integrated into the existing photolithography process without requiring additional separate components or steps
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 significantly reduces alignment errors and improves registration accuracy between device patterns, enhancing the performance of semiconductor structures by compensating for overlay shifts during the double exposure process, achieving about 40% improvement in registration accuracy.
Implementation Method 1
Grating diffraction refers to that, when a light beam is illuminated on a grating type alignment mark on a wafer, the beam is then diffracted and the diffracted light carries all the information about the alignment mark
Implementation Method 2
the interference image of the ±n levels of the diffracted light on the reference plane is collected
Data Source
AI summary
A method is provided for fabricating a photolithography alignment mark structure. The method includes providing a substrate; forming a first grating, a second grating, a third grating and a fourth grating in the substrate; forming a photoresist layer on a surface of the substrate; obtaining a first alignment center along a first direction and a second alignment center alone a second direction based on the first grating and the fourth grating, respectively; providing a mask plate having a fifth grating pattern and a sixth grating pattern; aligning the mask plate with the substrate by using the first alignment center as an alignment center along the first direction and the second alignment center as an alignment center along the second direction; reproducing the fifth grating pattern and the sixth grating pattern in the photoresist layer; and forming a fifth grating and a sixth grating on the substrate by removing a portion of photoresist layer.