Dual Photoresist Layer Photolithography for Sub-Micron Resolution
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Solution Overview
Problem
Conventional photolithography technologies face challenges in achieving high resolution and efficiency, with limitations in line width minimization and increased costs due to the use of expensive light sources and time-consuming writing processes.
Innovation Solution
A photolithography method that utilizes a combination of positive and negative photoresists, where the difference in their response to light and exposure energy is exploited to create pattern contour lines with smaller line widths than the original mask patterns, thereby achieving line width reduction and increased line density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional UV optical lithography is used, then the process is simple and low cost, but the resolution is limited to about one micro
Solution Approach 1:
The patent divides the photoresist into two separate layers: a lower negative photoresist layer and an upper positive photoresist layer. Each layer is exposed and developed separately, allowing the negative layer to define the core pattern while the positive layer refines the contours. This segmentation enables achieving sub-micron resolution without requiring expensive DUV or EUV equipment, thus improving manufacturing precision while avoiding increased device complexity.
Solution Approach 2:
The patent introduces a vertical dimension by stacking two photoresist layers at different heights. The lower negative photoresist layer (thickness: 50-200 nm) provides the base pattern, while the upper positive photoresist layer (thickness: 100-500 nm) adds contour refinement. This dimensional approach allows complex 3D pattern formation through 2D mask exposure, achieving high resolution without proportionally increasing process complexity.
2Manufacturing precision
If DUV or EUV light sources are used to achieve higher resolution, then the manufacturing precision improves, but the cost increases significantly
Solution Approach 1:
The patent uses conventional UV light (wavelength: 365-405 nm) to create optical copies of the mask pattern through two photoresist layers. The negative photoresist layer captures the main pattern features, while the positive photoresist layer copies and refines the contour details. This optical copying approach achieves sub-micron line widths using inexpensive UV sources, avoiding the need for costly DUV or EUV equipment while maintaining high manufacturing precision.
3Manufacturing precision
If particle beam lithography is used to increase resolution, then the manufacturing precision improves, but the productivity decreases due to time-consuming writing processes
Solution Approach 1:
The patent replaces the mechanical scanning writing process of particle beam lithography with a parallel optical exposure system. Conventional UV light sources illuminate the entire mask pattern simultaneously, and the two-photoresist layer system processes the full field in one exposure step. This substitution eliminates the sequential writing bottleneck while maintaining sub-micron resolution, thereby significantly improving productivity without sacrificing manufacturing precision.
4Manufacturing precision
If a single photoresist layer is used, then the process is simple, but the line width cannot be minimized below the mask pattern size
Solution Approach 1:
The patent segments the single photoresist layer into two functional layers: a lower negative photoresist layer that defines the core pattern with line width W1, and an upper positive photoresist layer that refines the contour to achieve narrower line width W2. This segmentation allows the final pattern line width to be smaller than the original mask pattern features, overcoming the single-layer limitation while keeping the overall process relatively simple.
Solution Approach 2:
The patent applies different photoresist materials and exposure conditions to different vertical positions within the photoresist structure. The lower negative photoresist layer uses one set of exposure and development parameters optimized for base pattern formation, while the upper positive photoresist layer uses different parameters optimized for contour refinement. This local quality differentiation enables precise line width control at different depths, achieving sub-micron features without proportionally increasing overall process complexity.
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 achieves high efficiency, low cost, and easy operation, enabling the miniaturization of mask pattern sizes and the multiplication of line density, while also avoiding the dissolution of photoresists during coating processes.
Implementation Method 1
ultraviolet rays travel through a mask and illuminates a surface of a substrate attached with a layer of photoresist film, which causes chemical reactions to occur in photoresists in the exposed region
Data Source
Figure 1A~1B
Figure 1C
Figure 1D
AI summary
The present invention relates to a photolithography method and a photolithography system. The method comprises: (1) forming a negative photoresist layer on a substrate using a negative photoresist, and forming a positive photoresist layer on the negative photoresist layer using a positive photoresist; (2) patterning the negative photoresist layer and the positive photoresist layer to form a positive pattern region on the positive photoresist layer and a negative pattern region on the negative photoresist layer, wherein s size of the positive pattern region is larger than a size of the negative pattern region; (3) developing the positive photoresist layer with developer for positive photoresist to remove the positive photoresist in the positive pattern region; and (4) developing the negative photoresist layer with developer for negative photoresist to remove the negative photoresist located near the negative pattern region, thereby providing an exposed region associated with a size of the positive pattern region and a size the negative pattern region, to expose the substrate. Compared with existing single-exposure photolithography technology, the method of the present invention is simple and a line width smaller than that of the conventional technology can be achieved by pattern contouring. The method can be widely used in semiconductor process and has extensive values of research and application.