Charged Particle Beam Writing Offset Time Correction
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Solution Overview
Problem
The existing electron beam writing apparatuses face challenges in maintaining writing accuracy due to changes in lens excitation, leading to variations in pattern size with multiplicity, which increases downtime and requires frequent evaluation pattern writing to determine optimal offset times.
Innovation Solution
A charged particle beam writing method that calculates an optimal offset time using a function based on the lens value, allowing for correction of irradiation time and efficient beam switching, thereby reducing pattern size variations and improving accuracy without increasing downtime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple writing is performed to reduce deflector contamination and improve pattern accuracy, then reliability is improved, but manufacturing precision deteriorates due to pattern size variation with multiplicity
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the offset time parameter based on the multiplicity of writing passes. The control unit calculates different offset times for different multiplicities (e.g., first multiplicity uses first offset time, second multiplicity uses second offset time), thereby compensating for pattern size variations and maintaining manufacturing precision across multiple writing operations.
2Manufacturing precision
If evaluation patterns are written repeatedly to determine optimal offset time for every beam adjustment, then manufacturing precision is improved, but productivity deteriorates due to increased downtime
Solution Approach 1:
The patent implements preliminary action by pre-storing multiple offset time values in the storage unit, each corresponding to different multiplicities. When beam adjustment is performed, the control unit directly retrieves the appropriate offset time from storage based on the adjustment parameters, eliminating the need to write evaluation patterns and perform repeated measurements. This preliminary preparation of offset time data significantly reduces downtime while maintaining writing accuracy.
3Manufacturing precision
If offset time is changed to compensate for pattern size variation, then manufacturing precision is improved, but device complexity increases due to additional control functions
Solution Approach 1:
The patent applies universality by designing the storage unit to serve multiple functions: it stores both the offset times corresponding to different multiplicities and the beam adjustment parameters. The control unit performs multiple functions by retrieving offset times based on beam adjustment parameters and applying them to compensate for pattern size variations. This multi-functional approach avoids adding separate dedicated components, thereby limiting the increase in device complexity while achieving improved pattern size consistency.
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 method enables precise determination of optimal offset times, reducing pattern size variations and improving writing accuracy by using a function that correlates lens values with optimal offset times, thus enhancing the efficiency and accuracy of the electron beam writing process.
Implementation Method 1
an electron lens 20a, 20b disposed between the current limiting aperture 16 and the blanking aperture 22
Implementation Method 2
a blanking deflector 18 that switches between beam ON and beam OFF so as to control an irradiation time by deflecting the charged particle beam
Data Source
AI summary
In one embodiment, a charged particle beam writing apparatus includes a current limiting aperture, a blanking deflector switching between beam ON and beam OFF so as to control an irradiation time by deflecting the charged particle beam having passed through the current limiting aperture, a blanking aperture blocking the charged particle beam deflected by the blanking deflector in such a manner that the beam OFF state is entered, and an electron lens disposed between the current limiting aperture and the blanking aperture. A lens value set for the electron lens is substituted into a given function to calculate an offset time. The offset time is added to an irradiation time for writing a pattern to correct the irradiation time. The blanking deflector switches between the beam ON and the beam OFF based on the corrected irradiation time.