Low Thermal Expansion Correcting Substrate for Charged Particle Beam Lithography
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Solution Overview
Problem
Conventional correcting substrates for charged particle beam lithography apparatuses face issues with electron charging, contrast deterioration, and thermal expansion errors, which hinder accurate position correction during micropatterning.
Innovation Solution
A correcting substrate with a low thermal expansion material, featuring two conductive films with different reflectances to avoid electronic charging and enhance contrast, and a rear surface exposing the low thermal expansion material to minimize thermal expansion errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a glass substrate with silicon oxide is used as the correcting substrate, then the substrate provides a stable base structure, but the substrate thermally expands during electron beam irradiation causing position errors
Solution Approach 1:
The patent changes the thermal expansion parameter of the substrate by selecting materials with different thermal expansion coefficients. Specifically, it uses substrates made from ceramics or glass-ceramics with controlled thermal expansion properties to minimize dimensional changes during electron beam irradiation, thereby maintaining position accuracy while preserving structural stability.
2Measurement precision
If the metal film is completely removed from the pattern portion, then the glass surface is exposed allowing electron beam scanning, but electronic charging occurs causing measurement errors
Solution Approach 1:
The patent applies local quality by creating regions with different metal film thicknesses. The pattern portions retain thin metal film layers that prevent electronic charging, while non-pattern portions have thicker or complete metal film coverage. This localized differentiation allows electron beam scanning to proceed without charging effects in the measurement areas.
Solution Approach 2:
The correcting substrate employs a composite structure combining glass substrate with multi-layer metal film configurations. The composite nature allows different regions to serve different functions: some areas provide charging prevention through residual metal films, while other areas provide measurement contrast through varying reflectances.
3Object-generated harmful factors
If the metal film is slightly left on the pattern portion, then electronic charging is avoided, but the contrast between pattern and non-pattern portions deteriorates reducing measurement accuracy
Solution Approach 1:
The patent implements local quality by creating distinct metal film thickness zones: pattern portions have thin residual films for charging prevention, while non-pattern portions maintain thicker films for contrast. This spatial differentiation of film properties simultaneously achieves charging prevention and maintains measurement contrast.
Solution Approach 2:
The correcting substrate uses a composite metal film structure with varying thicknesses and compositions. By combining different metal film configurations in different regions, the substrate simultaneously prevents electronic charging in measurement areas while maintaining sufficient contrast for accurate pattern recognition.
4Device complexity
If a single metal film is used on the substrate, then the structure is simple, but the reflectance contrast between different regions is insufficient for accurate measurement
Solution Approach 1:
The patent employs composite material structures with multiple metal film layers having different thicknesses and compositions. This composite approach creates distinct reflectance characteristics in different regions, providing sufficient contrast for accurate measurement while maintaining a relatively simple overall substrate design.
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 solution enables accurate position correction by preventing electronic charging and thermal expansion errors, improving the precision of pattern writing in charged particle beam lithography.
Implementation Method 1
a substrate body using a low thermal expansion material having a thermal expansion lower than that of a silicon oxide (SiO2) material
Implementation Method 2
a first conductive film arranged above the substrate; and a second conductive film selectively arranged on the first conductive film and having a reflectance higher than the first conductive film
Data Source
AI summary
A correcting substrate for a charged particle beam lithography apparatus includes a substrate body using a low thermal expansion material having a thermal expansion lower than that of a silicon oxide (SiO2) material; a first conductive film arranged above the substrate; and a second conductive film selectively arranged on the first conductive film and having a reflectance higher than the first conductive film, wherein the low thermal expansion material is exposed on a rear surface of the correcting substrate.