Maskless Lithography Taper Control via Dose Ladders
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Solution Overview
Problem
Mask-based lithography systems are inefficient for fine-tuning taper angles in photoresist layers, requiring complex and costly mask adjustments, which are time-consuming and difficult to produce, limiting the yield and increasing process complexity.
Innovation Solution
Implementing maskless-based lithography methods that use software-controlled dose changes to achieve precise taper control by dividing the geometric shape into sections with varying exposure doses, allowing for flexible adjustment of taper angles without additional mask costs or fabrication time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mask-based lithography systems are used to fine-tune taper angles, then taper control capability is improved, but mask complexity and production cost increase significantly
Solution Approach 1:
The patent extracts the taper control function from the mask itself and transfers it to the illumination system. By removing the need for complex multitone mask structures and focusing the taper control capability into the illumination optics, the mask becomes simpler while maintaining precise taper angle control through adjustable illumination parameters.
Solution Approach 2:
The patent replaces the mechanical/physical complexity of multitone masks with an optical control mechanism. Instead of manufacturing masks with varying transparency levels and grating structures, the system uses controllable illumination sources to achieve the same taper control effect, substituting a flexible optical system for a rigid mechanical mask structure.
2Manufacturing precision
If complex multitone masks are used to achieve desired taper angles, then taper precision is improved, but production time and cost increase
Solution Approach 1:
The patent performs preliminary action by pre-configuring the illumination system with the necessary control capabilities for taper adjustment. Instead of spending time manufacturing custom multitone masks for each taper requirement, the system is prepared in advance with adjustable illumination parameters that can be quickly modified to achieve different taper angles without additional mask fabrication time.
Solution Approach 2:
The patent achieves taper control by changing illumination parameters (such as numerical aperture, illumination angle, or intensity distribution) rather than changing the mask itself. This allows rapid adjustment of taper angles by modifying operational parameters of the illumination system, eliminating the time-consuming process of mask remanufacturing for different taper requirements.
3Manufacturing precision
If mask transparency is adjusted to control taper angle, then taper control is improved, but yield decreases due to mask production difficulties
Solution Approach 1:
The patent extracts the taper control function from the mask and relocates it to the illumination system. This removes the requirement for complex multitone mask manufacturing, which has low yield due to the difficulty of producing masks with precise transparency variations. The illumination system assumes the taper control role, allowing standard masks to be used while achieving the desired taper control through optical means.
4Adaptability or versatility
If mask-based methods are used for taper control, then taper angle adjustment is possible, but process complexity and verification time increase
Solution Approach 1:
The patent makes the illumination system universal by equipping it with multi-functionality to handle both standard lithography exposure and taper control operations. Instead of requiring separate specialized masks or processes for different taper angles, the unified illumination system can adjust its parameters to achieve various taper control requirements, simplifying the overall process while maintaining adaptability.
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
Enables precise control of taper angles and multi-layer taper control without additional steps, reducing process complexity and cost, while providing flexibility in achieving desired taper profiles for photoresist layers.
Implementation Method 1
a light-sensitive photoresist is typically applied to at least one surface of the substrate. Then, a pattern generator exposes selected areas of the light-sensitive photoresist as part of a pattern with light to cause chemical changes to the photoresist in the selective areas
Data Source
AI summary
Embodiments described herein relate to methods of forming layers using maskless based lithography. In these embodiments, the methods implement ladders of dose change such that a geometric shape can be divided into overlaying sections. The overlaying sections can include a different dose of each section such that taper control can be achieved. The taper can be achieved by manipulating the geometry “mask data” into overlaying sections that are exposed by various doses controlled by pixel blending (PB) exposure techniques. To perform the methods described herein, a maskless lithography tool is used. The maskless lithography tool includes a controller that performs software based “mask data” manipulation. As such, because the methods are performed by software with no mask, there is much more flexibility to tune the taper angles and/or photoresist thickness residuals for multi-tone/gray tone mask features without any additional mask cost and fabrication time, providing advantages over conventional lithography methods using masks.