Charged Particle Beam Lithography Thermal Dose Modulation
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Solution Overview
Problem
In charged particle beam lithography, the increasing dose and shot number required for miniaturization lead to resist heating, causing temperature variations and edge roughness, which complicates pattern writing and increases computational complexity.
Innovation Solution
A charged particle beam lithography apparatus and method that includes data storage and processing circuits for dividing pattern writing data into shot data, calculating temperature rise from previous shots, determining a representative temperature, and modulating the dose to manage heat transfers and optimize pattern writing schedules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the dose and shot number are increased to reduce shot noise and edge roughness, then the pattern writing precision is improved, but the resist heating increases causing temperature variations and edge roughness
Solution Approach 1:
The system calculates the temperature rise in advance for each shot based on the writing schedule and heat transfer from previous shots. This preliminary temperature calculation allows the dose to be adjusted before irradiation, preventing resist heating while maintaining pattern writing precision.
Solution Approach 2:
The system implements a feedback mechanism where the calculated temperature rise from previous shots is used to modulate the dose of subsequent shots. This feedback loop ensures that the dose is dynamically adjusted to compensate for heat accumulation, maintaining both precision and temperature control.
2Manufacturing precision
If the number of shots is increased to achieve desired pattern precision, then the pattern writing precision is improved, but the pattern writing time increases
Solution Approach 1:
The writing schedule and temperature rise calculations are performed in advance before actual pattern writing. This preliminary planning allows for optimized shot sequencing that minimizes total writing time while maintaining the required number of shots for precision.
Solution Approach 2:
The system dynamically adjusts the writing schedule based on calculated temperature rises and heat transfer characteristics. By optimizing the sequence and timing of shots, the system achieves the desired pattern precision with minimal writing time.
3Productivity
If the current density is increased to reduce pattern writing time, then the productivity is improved, but the resist heating increases causing pattern size variation
Solution Approach 1:
The system changes the dose parameter dynamically for each shot based on calculated temperature rises. By modulating the dose in response to temperature conditions, the system maintains pattern size precision even when writing at higher speeds with increased current density.
Solution Approach 2:
The dose modulation based on calculated temperature feedback allows the system to maintain precision while operating at higher productivities. The feedback mechanism compensates for heat effects that would otherwise cause pattern size variation.
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 effectively reduces pattern size variations due to resist heating while optimizing computational complexity, enabling faster and more precise pattern writing by adjusting the dose based on calculated temperature rises.
Implementation Method 1
when a further high-density electron beam irradiates an amount of irradiation energy that has increased, in a short time, the temperature of a substrate increases and the sensitivity of the resist varies. That is, there is a problem that a phenomenon referred to resist heating occurs.
Implementation Method 2
calculating a temperature rise amount caused by heat transfers from other shots written before a shot to be written
Data Source
AI summary
A charged particle beam lithography apparatus according to an embodiment includes: a pattern-writing-data data storage processing circuitry configured to store pattern writing data in association with pattern attribute information; a shot dividing processing circuitry configured to divide the pattern writing data into shot data in association with the pattern attribute information; an indicator data storage processing circuitry configured to store an indicator for determining correction section regions to be merged on calculation in an approximation calculation of heat transfers, the indicator being associated with the pattern attribute information; a pattern writing schedule creator configured to create a pattern writing schedule based on the shot data; an approximation-calculation-method determining processing circuitry configured to determine an approximation calculation method of the heat transfers from other shots written before a shot to be written, the shot being associated with the shot data to be written, based on the pattern writing schedule and the indicator; a thermal diffusion calculator configured to calculate a temperature rise amount caused by the heat transfers from the other shots written before the shot to be written, the shot being associated with the shot data to be written, based on the approximation calculation method; a shot temperature calculator configured to calculate a representative temperature of the shot to be written with the shot data, based on the temperature rise amount; a dose modulator configured to modulate a dose of the shot to be written with the shot data, based on the representative temperature; and a lithography mechanism including a charged particle beam source, a deflector, and a stage on which the target object is placed, and to perform writing based on a modulated dose and the pattern writing schedule.