Variable Transmittance Photo Mask for 3D Semiconductor Integration
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Solution Overview
Problem
Three-dimensional semiconductor devices require complex fabrication processes due to the need for dense integration of functional units, which is not efficiently addressed by existing methods.
Innovation Solution
A method involving the use of multiple photo masks with varying transmission regions to form photoresist patterns with different heights, followed by anisotropic etching to create a staircase structure in the etch-target layer, simplifying the fabrication process and enabling dense integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple exposure processes with different photo masks are used to form photoresist patterns with different heights, then the integration density is enhanced and process complexity is reduced, but the manufacturing process becomes more complex in terms of exposure steps
Solution Approach 1:
The photo mask is segmented into multiple transmission regions with different optical transmittance values, allowing different portions of the photoresist layer to be exposed to different degrees of light. This segmentation enables the formation of photoresist patterns with different heights in a single exposure process, effectively reducing the number of required exposure steps while achieving high integration density.
Solution Approach 2:
The optical transmittance parameter of the photo mask is varied across different transmission regions to control the exposure dose received by different areas of the photoresist layer. By changing this parameter spatially, the method achieves differential etching depths and creates complex three-dimensional structures without requiring multiple sequential exposure processes.
2Loss of time
If a single photo mask with varying optical transmittance is used, then the number of exposure processes is reduced, but the photo mask design becomes more complex
Solution Approach 1:
The photo mask design transitions from a two-dimensional binary structure (transmissive vs. opaque) to a three-dimensional structure with varying thickness or material composition across different regions. This dimensional addition enables continuous variation of optical transmittance, allowing complex patterning in a single exposure step while the mask itself becomes a more sophisticated component.
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 allows for the efficient formation of complex structures with reduced process complexity, enhancing the integration density of semiconductor devices.
Implementation Method 1
The first photo mask includes a plurality of first transmission regions. Each first transmission region has different optical transmittance. A first exposure process is performed using a first photo mask to form a plurality of first-irradiated patterns in the photoresist layer.
Implementation Method 2
A second T-shaped pattern is formed in the insulating layer by performing a single anisotropic etching process using the photoresist layer having the first T-shape pattern.
Data Source
AI summary
A method of fabricating a semiconductor device is provided. An etch-target layer is formed on a substrate. A photoresist layer is formed on the etch-target layer. A first exposure process is performed using a first photo mask to form a plurality of first-irradiated patterns in the photoresist layer. The first photo mask includes a plurality of first transmission regions. Each first transmission region has different optical transmittance. A second exposure process is performed using a second photo mask to form a plurality of second-irradiated patterns in the photoresist layer. The second photo mask includes a plurality of second transmission regions. Each second transmission region has different optical transmittance. A photoresist pattern is formed from the photoresist layer by removing the plurality of first-irradiated and second-irradiated patterns from the photoresist layer. A lower structure is formed from the etch-target layer by etching the etch-target layer using the photoresist pattern.