Charged Particle Beam Dose Modulation for Resist Heating
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Solution Overview
Problem
Existing charged particle beam writing technologies face challenges in efficiently suppressing dimensional variations due to resist heating and correction residuals from the proximity effect, especially during multiple pattern writing operations, which complicates the correction process and reduces efficiency.
Innovation Solution
A charged particle beam writing apparatus and method that virtually divides the pattern writing region into multiple mesh regions, using a dose model to correct for proximity effects and temperature-induced variations, with a polynomial operation to modulate the dose based on representative temperatures and area densities, ensuring the difference between the dose threshold and the operated dose remains within a tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple pattern writing operations are performed to suppress resist heating, then dimensional variations due to resist heating are reduced, but correction residuals from the proximity effect increase and the correction process becomes more complex
Solution Approach 1:
The pattern writing region is divided into multiple mesh regions, and the correction process is segmented into distinct stages: proximity effect correction applied first to determine base dose, then temperature correction applied separately based on accumulated dose. This segmentation allows each correction to be calculated and applied independently, reducing the complexity of their interaction while achieving both proximity effect suppression and resist heating compensation.
Solution Approach 2:
The proximity effect correction is performed in advance before the actual pattern writing operation. By calculating and applying the proximity effect correction dose modulation beforehand, the system establishes a corrected dose distribution that accounts for backscattering effects. This preliminary correction simplifies the subsequent temperature correction process, as the base dose is already optimized for proximity effects.
2Manufacturing precision
If dose modulation is applied to correct proximity effects, then dimensional variations from backscattering are suppressed, but correction residuals remain when temperature corrections are subsequently applied
Solution Approach 1:
The system uses a feedback mechanism where the dose distribution calculated from proximity effect correction becomes the input for temperature correction calculation. The accumulated dose from proximity-corrected writing operations is fed into the temperature correction algorithm, which then calculates additional dose modulation to compensate for resist heating. This feedback loop ensures that both corrections work together rather than conflict, maintaining correction accuracy.
Solution Approach 2:
The system changes the dose parameter dynamically through a two-stage process: first applying proximity effect correction that modifies dose based on pattern density and backscattering, then applying temperature correction that further modulates dose based on accumulated thermal effects. By changing dose parameters in sequence based on different physical conditions, the system achieves accurate dimensional control despite the complexity of interacting effects.
3Productivity
If higher current density is used to reduce pattern writing time, then productivity increases, but resist heating occurs causing worse line width precision
Solution Approach 1:
The system employs multiple passes of pattern writing operations, where each pass writes a portion of the total pattern. By dividing the writing process into periodic passes, the system can use higher current density in each pass to maintain productivity, while the intermittent nature of multiple passes allows heat to dissipate between passes, preventing excessive resist heating and maintaining line width precision.
Solution Approach 2:
The system dynamically adjusts the dose parameter based on temperature calculations. By monitoring the accumulated dose and calculated temperature rise, the system modifies the dose applied in subsequent passes to compensate for resist heating effects. This parameter change allows the system to maintain high current density for productivity while correcting for temperature-induced precision degradation.
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 suppresses dimensional variations caused by resist heating while minimizing correction residuals, thereby enhancing the efficiency and precision of pattern writing, even during multiple passes, by optimizing the dose modulation and temperature correction processes.
Implementation Method 1
a problem of phenomenon called resist heating is caused in which the substrate temperature is heated
Implementation Method 2
calculating a representative temperature for each minimum deflection region of deflection regions based on heat transfer from other minimum deflection regions written before
Data Source
AI summary
A apparatus includes a unit to operate a first dose of a beam corrected for a proximity effect for each of second mesh regions of a second mesh size obtained by dividing the first mesh size by a product of a natural number and a number of passes, by using a dose model using a dose threshold; a unit to operate a representative temperature rising due to heat transfer originating from irradiation of the beam by using a dose for an applicable pass of the first dose and a unit to operate a polynomial having a term obtained by multiplying a dose modulation coefficient based on the representative temperature by a pattern area density as an element, and a dose that makes a difference between a value obtained by operating the polynomial and the dose threshold within a tolerance is used.