Electron Beam Exposure Apparatus Contamination Control
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Solution Overview
Problem
Existing electron beam exposure apparatuses face issues with beam drift due to contamination, which is not effectively addressed by previous cleaning methods, as ozone injection can form insulators like SiO2, leading to continued beam drift problems.
Innovation Solution
An electron beam exposure apparatus with a supplying device for injecting reducing gases like ammonia, hydrogen, or hydrazine, and ozone into the column, controlled to maintain a predetermined injection time, which reacts with contamination to prevent adhesion and oxidation, thereby stabilizing the beam position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If ozone is injected into the chamber to clean contamination, then contamination is removed, but insulators like SiO2 are formed on the mask surface causing beam drift
Solution Approach 1:
A metal layer with oxidation resistance (such as titanium, platinum, or palladium) is introduced as an intermediary protective barrier between the silicon mask surface and the oxidative environment. This metal layer prevents oxygen from reaching and oxidizing the silicon, thereby avoiding the formation of insulating SiO2 films that cause beam drift, while still allowing the ozone cleaning process to remove contamination from the mask surface
Solution Approach 2:
The mask is constructed as a composite structure combining silicon (for pattern formation) with a metal coating layer (for oxidation resistance). This composite structure leverages the complementary properties of both materials: silicon provides the necessary optical and structural characteristics for electron beam exposure, while the metal layer provides protection against oxidative damage during cleaning processes
2Stability of the object's composition
If a metal layer is attached to the mask surface to prevent oxidation, then oxidation is prevented, but mask deformation occurs affecting exposure accuracy
Solution Approach 1:
The thickness of the metal protective layer is precisely controlled within a specific range (0.1-10 nm) to optimize the balance between oxidation protection and mask deformation. By adjusting this critical parameter, the layer provides sufficient oxidation resistance while maintaining the mask's structural integrity and optical properties for accurate exposure
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
The method effectively suppresses contamination and beam drift by using reducing gases to prevent oxidation and adhesion, ensuring accurate exposure processing by maintaining the cleanliness of the apparatus and preventing charge-up from insulators.
Implementation Method 1
the injection of the reducing gas into the column is continued for a predetermined period of time
Implementation Method 2
supplying device for injecting a reducing gas into a column
Implementation Method 3
ozone is caused to collide with an electron beam inside the apparatus to be decomposed into oxygen and active oxygen
Implementation Method 4
the active oxygen generated through the decomposition reacts with the contamination
Data Source
AI summary
Provided is an electron beam exposure apparatus for forming a desired pattern on a sample mounted on a wafer stage by exposure with an electron beam generated form an electron gun. The electron beam exposure apparatus includes: supplying device of injecting a reducing gas into a column in which the electron gun and the wafer stage are housed; and control unit of performing control so that the injection of the reducing gas into the column is continued for a predetermined period of time. Organic contamination is combined with H generated from the reducing gas by irradiation of an electron beam, and then evaporates. Further included is supplying device of injecting an ozone gas into the column. The control unit may perform control so that the injection of the ozone gas into the column in addition to the injection of the reducing gas is continued for a predetermined period of time.