Refractive Mask for Tunable Lithography
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Solution Overview
Problem
The high cost and complexity of masks in lithographic processes for integrated circuit fabrication, due to the need for multiple masks with fine patterns, lead to significant expenses in producing multi-layer electronic ICs.
Innovation Solution
The use of refractive masks with regular or irregular arrays of micro-lenses and through-holes allows a single mask to pattern photoresist layers differently, reducing the number of masks required by varying the distance between the mask and the photoresist layer and controlling light doses to produce adjustable light patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple masks with fine patterns are used for lithographic processes, then manufacturing precision of integrated circuits is improved, but device complexity and manufacturing cost increase significantly
Solution Approach 1:
The patent applies universality by designing a single mask that can serve multiple functions for different lithographic layers. The mask includes both opaque regions for blocking light and transparent regions with microlens arrays for focusing light, enabling it to pattern multiple photoresist layers with different feature sizes without requiring separate masks for each layer.
Solution Approach 2:
The mask is segmented into distinct functional regions: opaque regions that block light to create certain patterns, and transparent regions containing microlens arrays that focus light to create different patterns. This segmentation allows different portions of the mask to serve different patterning functions simultaneously.
2Manufacturing precision
If multiple masks are used for different layers of integrated circuits, then manufacturing precision is improved, but loss of substance and manufacturing cost increase
Solution Approach 1:
The patent merges the functionality of multiple masks into a single mask structure. By combining opaque regions and transparent microlens regions in one mask, the invention eliminates the need to fabricate and consume multiple separate masks, thereby reducing material consumption and associated costs.
3Device complexity
If a single mask is used for multiple layers, then device complexity and cost are reduced, but manufacturing precision may be compromised
Solution Approach 1:
The mask implements local quality by providing different optical properties in different regions: opaque regions for light blocking and transparent regions with microlens arrays for light focusing. Each region is optimized for its specific function, allowing the single mask to achieve high precision patterning for different layers with different feature size requirements.
Solution Approach 2:
The microlens arrays in the transparent regions enable parameter changes in the light pattern. By adjusting the microlens focal lengths and arrangements, the mask can produce different feature sizes and patterns on different photoresist layers, maintaining manufacturing precision across multiple layers.
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 enables the fabrication of integrated circuits with multiple levels using a single refractive mask, reducing mask costs and complexity while maintaining precise control over feature sizes and patterns, thereby improving the efficiency of the lithographic process.
Implementation Method 1
refractive masks have a regular or an irregular array of micro-lenses
Implementation Method 2
The refractive mask has a plurality of lenses. Various embodiments can use a single refractive mask to pattern photoresist layers differently thereby offering the possibility of reducing the number of masks in IC fabrication.
Data Source
AI summary
A method includes exposing a first photoresist layer through a refractive mask to form a first pattern of above-threshold exposure spots in the first layer and exposing a second photoresist layer through the same mask to form a second pattern of above-threshold exposure spots in the second layer. Coordination numbers of exposure spots are larger in the first pattern than in the second pattern, nearest-neighbor pairs of the exposure spots have larger spacings in the first pattern than in the second pattern or largest ones of the exposure spots have larger diameters in the first pattern than in the second pattern.