Phase Change Material Lithography for Sub-32 nm Patterning
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Solution Overview
Problem
Current lithographic techniques face challenges in achieving finer resolution due to limitations in minimum feature pitch, particularly with 193 nm wavelength radiation, and existing double exposure methods suffer from resist 'memory' effects that affect patterning accuracy.
Innovation Solution
A method employing a phase change material layer that is selectively heated and cooled to convert regions to an amorphous state using two doses of radiation, allowing for precise pattern formation without 'memory' effects, enabling higher resolution patterns through double exposure lithography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional single exposure lithography is used, then the process is simple and fast, but the minimum feature pitch is limited by the radiation wavelength and numerical aperture
Solution Approach 1:
The patterning process is segmented into multiple exposure steps. The first exposure creates a preliminary pattern, and the second exposure creates additional features at different positions. By combining these segmented exposure steps, the method achieves feature pitches below the single-exposure minimum pitch limit, effectively dividing the complex high-resolution patterning task into manageable sequential steps.
Solution Approach 2:
The first exposure performs a preliminary patterning action that prepares the resist for the second exposure. This preliminary pattern formation establishes a foundation that, when combined with the second exposure pattern, achieves the final high-resolution result. The preliminary action enables subsequent features to be placed at positions that would be impossible to resolve in a single exposure.
2Manufacturing precision
If double exposure techniques are used to increase structure density, then features can be spaced below minimum feature pitch, but resist memory effects from the first exposure degrade patterning accuracy in the second exposure
Solution Approach 1:
The method changes the physical-chemical parameters of the resist between exposures by selecting specific development conditions that erase the memory effect from the first exposure. By controlling development parameters such as solvent composition, temperature, and development time, the resist is reset to a state that accepts the second exposure pattern with high fidelity, eliminating the degradation caused by memory effects.
Solution Approach 2:
The second exposure creates a copy of the desired final pattern that is independent of the first exposure pattern. By using a second reticle or programmable patterning device to imprint the second pattern, the method effectively copies the intended geometry onto the resist, overriding any memory effects from the first exposure and achieving the precise final pattern.
3Manufacturing precision
If shorter wavelength radiation is used to achieve finer resolution, then pattern resolution improves, but the equipment complexity and cost increase significantly
Solution Approach 1:
Instead of changing the radiation wavelength parameter to achieve finer resolution, the method changes the patterning process parameters by using multiple exposures at the same wavelength. This approach maintains compatibility with existing 193 nm lithography equipment while achieving sub-32 nm resolution through process innovation rather than hardware upgrade, avoiding the complexity and cost of shorter wavelength systems.
Solution Approach 2:
The method introduces an intermediary patterning layer (such as a mandrel or sacrificial layer) that enables the formation of sub-resolution features. This intermediary structure acts as a mediator that allows conventional lithography to indirectly create patterns at resolutions below its diffraction limit, avoiding the need to directly improve the resolution of the main lithography system.
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 creation of high-resolution patterns with improved accuracy and contrast, effectively doubling the patterning resolution while minimizing proximity effects, enabling feature sizes such as 16 nm on a 64 nm pitch, and transferring these patterns into the substrate with enhanced precision.
Implementation Method 1
exposing a first portion of a phase change material layer provided on a substrate to a first dose of radiation from a patterned radiation beam, the first dose of radiation being sufficient to change the phase of the first portion to an amorphous state
Implementation Method 2
A patterning technique that has been developed to try to afford etching of smaller features employs the use of a hard mask provided in between a substrate layer that is to be patterned and a layer of resist
Data Source
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Figure 3a~3b
AI summary
A multiple patterning process employs a phase change material, portions of which can be converted to an amorphous state and then a remaining portion is selectively removed to provide high resolution pattern features with a feature spacing smaller than, for example, a minimum spacing available in a conventional patterning layer employing a single exposure. A lithographic apparatus for use in the process may comprise an exposure tool having a single illuminator and single patterning device that is imaged through a single exposure slit onto a scanning substrate. Alternatively, the exposure tool may have multiple illuminators and/or multiple scanning complementary patterning devices optionally used with multiple exposure slits on the scanning substrate to facilitate double patterning in a single substrate pass.