Charged Particle Beam Writing Pressure Control for Focus Stability
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Solution Overview
Problem
Conventional charged particle beam writing apparatuses face issues with beam drift due to hydrocarbon contamination and high vacuum gauge deterioration from constant high pressure in the column, which is exacerbated by the gradual decrease in gas generated from components over time.
Innovation Solution
A multi-beam writing apparatus with a control system that adjusts the internal pressure of the vacuum chamber by dynamically changing the target pressure value based on measured values, reducing the high initial pressure to prevent focus deviation and extend the life of the pressure sensor, while maintaining a stable environment for beam adjustment and pattern writing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of ozone gas introduction is gradually increased to maintain column pressure, then the column pressure can be maintained constant, but the pressure sensor deteriorates quickly due to prolonged high pressure state
Solution Approach 1:
The patent applies dynamics by making the target pressure value changeable over time. The control device dynamically adjusts the target pressure value from an initial higher value to a lower value as the apparatus operates. This dynamic adjustment allows the system to maintain adequate pressure for cleaning gas effectiveness initially, then reduces pressure to extend pressure sensor lifespan as the contamination level decreases over time.
Solution Approach 2:
The patent changes the pressure parameter from a constant high value to a time-varying value. The control device modifies the target pressure value based on operational time or contamination accumulation, transitioning from a higher initial pressure (effective for cleaning) to a lower operational pressure (gentle on sensors). This parameter change resolves the contradiction between maintaining cleaning effectiveness and preserving sensor longevity.
2Reliability
If cleaning gas is continuously introduced to remove hydrocarbon contamination, then beam drift can be prevented, but focus deviation occurs due to pressure fluctuation
Solution Approach 1:
The patent implements feedback control where the control device continuously monitors column pressure and adjusts the ozone gas introduction amount accordingly. When pressure deviates from the target value, the system automatically modifies the cleaning gas flow rate to restore pressure stability. This feedback mechanism simultaneously achieves contamination removal and pressure stability, preventing both beam drift and focus deviation.
Solution Approach 2:
The system performs self-regulation by automatically adjusting cleaning gas introduction based on real-time pressure conditions. The control device monitors the column environment and autonomously modulates the ozone gas flow to maintain optimal pressure, eliminating the need for external intervention and ensuring continuous stable operation without manual pressure adjustments.
3Reliability
If the column pressure is maintained at a high state to compensate for gas generation from components, then pressure stability can be achieved, but the pressure sensor deteriorates quickly
Solution Approach 1:
The patent employs periodic action by implementing time-based or condition-based pressure adjustment cycles. The system operates in phases: initially maintaining higher pressure to account for significant gas generation from components, then transitioning to lower pressure as the system stabilizes and gas generation decreases. This periodic pressure adjustment pattern maintains stability when needed while reducing sensor stress over time.
Solution Approach 2:
The system applies preliminary action by establishing a higher initial target pressure value at the start of operation when component outgassing is most significant. As the apparatus operates and gas generation from components gradually decreases, the target pressure value is reduced. This preliminary high-pressure state ensures stability during the critical initial phase, then transitions to lower pressure to protect the sensor during steady-state operation.
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 reduces focus deviation and prolongs the lifespan of the pressure sensor by dynamically adjusting the target pressure, minimizing the high internal pressure state and optimizing cleaning gas supply, thereby ensuring precise beam control and apparatus longevity.
Implementation Method 1
The separated active oxygen and pollution materials are reacted to convert them to carbon monoxide gas which is exhausted, thereby reducing the pollution materials that adhere to electronic optical system components.
Implementation Method 2
the ozone introduced into the column and electron beams are brought into collision to separate the ozone into oxygen and active oxygen
Data Source
AI summary
In one embodiment, an apparatus is for writing a pattern by irradiating a substrate as a writing target in a chamber with a charged particle beam. The apparatus includes a supply device supplying a cleaning gas to the chamber, a vacuum pump discharging a gas from the chamber, a pressure sensor detecting a pressure in the chamber, and a control device obtaining a detection value of the pressure sensor and controlling the supply device so that the pressure in the chamber reaches a first target value. When adjusting the charged particle beam with which the substrate is irradiated, the control device further controls the supply device so that the pressure in the chamber reaches a second target value different from the first target value.