Cleaning Methods for EB Lithography System
In a resin used for the electron-beam direct writing technology, organic matters are the major elements. When the electron beam hits a resin, the components composing the resin are scattered into the vacuum chamber and they adhere to the structures of the chamber again. The major element of the scattered components that adhere again then is carbon.
In a resin used for the electron-beam direct writing technology, organic matters are the major elements. When the electron beam hits a resin, the components composing the resin are scattered into the vacuum chamber and they adhere to the structures of the chamber again. The major element of the scattered components that adhere again then is carbon.
The scattered components adhered again are charged, or the electrical discharge might occur due to the uneven electric charge caused by the components. The electric field at the charged part or the electromagnetic field due to the electrical discharge might affect the direction of the beam. These incidents deteriorate the patterns drawn by EB Lithography System.
To prevent these phenomena, two cleaning methods are provided for EB Lithography System of ADVANTEST CORPORATION. One is the in-situ cleaning method in this moving picture. By this cleaning method, oxygen plasma is generated while keeping the vacuum. The oxygen plasma unites with the carbon adhered again and becomes carbon dioxide. The carbon dioxide is exhausted with the vacuum pump and exhausted outside the chamber. In the moving picture, the parts contaminated with the adhered carbon are shown with gold. The adhered carbon looks like the tar of the cigarette.
The other is the self-cleaning method that cleans the parts contaminated with the adhered carbon by introducing a small amount of ozone into the path of the electron beam (the amount by which the vacuum would not be deteriorated in the chamber), and oxidizing the carbon adhered on each parts in the chamber to carbon dioxide.
The self-cleaning method is used for "Prevention of Deterioration" (caused by the carbon adhered again) of the normal-state chamber and the in-situ cleaning method is used for "Recovery of Chamber" when the amount of adhered carbon on the chamber wall is larger. They are both useful methods with keeping the availability of the system higher and improving the reliability without bringing the chamber to atmospheric pressure.
The in-situ cleaning method is also used for the extreme ultraviolet lithography system (EUVL system).
These methods are key technologies to expose LSI patterns with electron beam direct writing stably.