Hard Mask Patterning for Semiconductor Opening Formation
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Solution Overview
Problem
In semiconductor manufacturing, the miniaturization of devices leads to reduced line width and space, causing diffraction issues and deformation of transfer patterns due to optical characteristics, resulting in un-identical patterns and quality defects when using conventional double-exposure techniques.
Innovation Solution
A method is developed where a substrate is divided into two regions with different pattern densities, and hard masks are formed and patterned to create an opening only in the overlapping area, with the etching process for the larger region performed first to avoid corner loss effects and ensure precise, identical patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional double-exposure technique is used to form fine-sized devices, then the line width and space can be reduced, but diffraction occurs and transfer pattern deformation happens resulting in un-identical patterns
Solution Approach 1:
The patent divides the pattern formation into two separate lithography processes: a first lithography process forms a first pattern, and a second lithography process forms a second pattern. By segmenting the pattern formation into distinct steps with different exposure conditions, the patent avoids the diffraction and deformation issues that occur when attempting to form fine patterns in a single exposure step.
Solution Approach 2:
The first pattern is formed in advance before the second pattern formation. The first pattern serves as a preliminary structure that guides the subsequent second lithography process. This preliminary action allows the second exposure to be optimized specifically for forming the fine-sized devices without suffering from the diffraction limitations of attempting to form all patterns simultaneously.
2Ease of manufacture
If two separated lithography processes are used to form patterns, then the pitch can be increased for current exposure systems, but the two sets of patterns may not be identical due to process variations
Solution Approach 1:
The patent applies different exposure conditions to different regions: the first lithography process uses first exposure conditions to form the first pattern, while the second lithography process uses second exposure conditions (different from the first) to form the second pattern. This local quality approach allows each lithography process to be optimized for its specific purpose, ensuring that both patterns are formed with high precision under their respective optimal conditions.
Solution Approach 2:
The patent introduces dynamic adjustment of exposure conditions between the two lithography processes. By varying exposure parameters such as wavelength, numerical aperture, or focus between the first and second exposures, the system adapts to the specific requirements of forming different pattern types, thereby maintaining pattern identity despite process variations.
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
This approach prevents corner loss effects and ensures precise, identical patterns by performing the etching process for the larger region first, enhancing the quality of semiconductor structures and avoiding the issues of un-identical patterns and unequal spacing.
Implementation Method 1
the integrated circuit layout is first designed and formed as a photo-mask pattern. The photo-mask pattern is then proportionally transferred to a photoresist layer positioned on the semiconductor wafer
Implementation Method 2
When the light passes through the mask, diffraction occurs, which reduces the resolution. Moreover, when light passes through the transparent regions of a mask having different interval sizes, the light through the regions having small interval sizes is influenced by the transparent regions having large interval sizes, which results in a deformation of the transfer pattern
Data Source
AI summary
A method for forming a semiconductor structure having an opening is provided. First, a substrate is provided, wherein a first region and a second region are defined on the substrate and an overlapping area of the first region and the second region is defined as a third region. A pattern density of the first region is substantially greater than that of the second region. Then, a material layer is formed on the substrate. A first hard mask and a second hard mask are formed on the material layer. The first hard mask in the first region is removed to form a patterned first hard mask. The second hard mask in the third region is removed to form a patterned second hard mask. Lastly, the material layer is patterned by using the patterned second hard mask layer as a mask to form at least an opening in the third region only.