Electrostatic Lens Inside Magnetic Object Lens for Beam Accuracy
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Solution Overview
Problem
In electron beam writing apparatuses, applying a plus bias voltage to the electrostatic lens to suppress fogging electrons can lead to secondary electrons remaining in the beam orbit, degrading beam position accuracy due to their high density and altered orbit.
Innovation Solution
A charged particle beam writing apparatus is designed with an electrostatic focus correction lens inside a magnetic object lens, where a positive voltage is applied to specific electrodes, and the magnetic field strength at the upper end of the electrode is kept at a predetermined value or less to manage secondary electron velocity and density, preventing beam position accuracy degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a plus bias voltage is applied to the electrostatic lens to suppress fogging electrons, then fogging electron influence is reduced, but secondary electrons remain in high density on the beam orbit and degrade beam position accuracy
Solution Approach 1:
The invention changes the magnetic field strength parameter of the object lens to a specific range (0.005 T to 0.05 T at the upper end of the electrostatic lens electrode). This parameter adjustment allows secondary electrons to have larger orbital radii and lower densities, enabling the use of plus bias voltage on the electrostatic lens without degrading beam position accuracy, thus resolving the contradiction between suppressing fogging electrons and maintaining beam precision
Solution Approach 2:
The invention applies different magnetic field strength conditions to different regions: the object lens creates a controlled weak magnetic field region specifically at the electrostatic lens location, while other regions maintain their normal magnetic field characteristics. This localized magnetic field adjustment enables selective control of secondary electron behavior at the critical electrostatic lens region without affecting the overall beam system
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 configuration effectively reduces secondary electron density and orbital radius, maintaining beam position accuracy and suppressing fogging electron influence, ensuring precise pattern writing with minimal position displacement.
Implementation Method 1
an electrostatic lens performing focus correction of the charged particle beam in accordance with a surface height of a substrate that is a writing target
Implementation Method 2
an object lens focusing the charged particle beam transmitted through the second aperture, the object lens being a magnetic field-type lens
Data Source
AI summary
In one embodiment, a charged particle beam writing apparatus includes an emitter emitting a charged particle beam, a first aperture shaping the charged particle beam, a second aperture shaping the charged particle beam transmitted through the first aperture, a projection lens projecting the charged particle beam transmitted through the first aperture on the second aperture, an object lens focusing the charged particle beam transmitted through the second aperture, the object lens being a magnetic field-type lens, and an electrostatic lens performing focus correction of the charged particle beam in accordance with a surface height of a substrate that is a writing target. The electrostatic lens is disposed inside the object lens, a positive voltage is applied to an electrode of the electrostatic lens. A strength of a magnetic field of the object lens at an upper end of the electrode has a predetermined value or less.