Radiant energy – Inspection of solids or liquids by charged particles – Electron probe type
Reexamination Certificate
2003-07-30
2004-10-26
Wells, Nikita (Department: 2881)
Radiant energy
Inspection of solids or liquids by charged particles
Electron probe type
C250S311000, C250S3960ML, C250S3960ML, C250S397000
Reexamination Certificate
active
06809319
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an electron beam writing technique for use in a manufacturing process of a semiconductor integrated circuit. More specifically, the present invention relates to high-precision electron beam writing equipment and writing method.
In prior art electron beam writing equipment, the size of the fastest deflection field on a sample is about 50 &mgr;m square (for example, Sakitani et al.: Journal of Vacuum and Technology, B12, 1992, pp. 2759-2763).
To deflect the 50 &mgr;m square precisely, deflection is corrected. Specifically, an electron beam is deflected to near the corner of the deflection field to detect a mark for beam correction near it, thereby measuring and correcting a difference between a desired deflection distance and an actually measured deflection distance.
Electron beam writing equipment having a micro deflection field of about 2 &mgr;m square is proposed (for example, see Iwadate et al.: Journal of Vacuum and Technology, B5, 1987, pp. 75-78).
As a reliable method for making electron beam writing equipment faster, there is a multi beam method. In this method, plural electron beams arrayed at a predetermined pitch in a two-dimensional manner are used. The distance between the electron beams is short so that the fastest deflection field is about 2 &mgr;m square.
In the above prior art deflection correction method of 50 &mgr;m square, scanning above 2 &mgr;m is performed for mark detection itself. The prior art method cannot be applied to a 2 &mgr;m-square field. In the above prior art, a deflection correction method of such micro deflection field is not described.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an electron beam writing technique which can correct deflection for a micro field in electron beam writing equipment with high precision.
To achieve the above object, the present invention has a function deflecting an electron beam at at least two different deflection speeds for scanning on a sample; a function repeating formation of a patterned beam in the electron beam by high speed scanning; a function moving the electron beam on a mark for beam correction by low speed scanning in synchronization with its one process; and a function detecting a backscattered electron or a secondary electron from the scanned mark for beam correction and near it or a transmission electron therethrough to correct the position or the deflection distance of the electron beam or blanking time from the detected result.
The method according to the present invention is particularly suitable for multi-beam electron beam writing equipment. Correction using plural electron beams is effective. For example, the electron beam writing equipment has a function moving adjacent electron beams in parallel to form a patterned beam; and a function comparing the detected results of the plural electron beams.
In addition, the patterned beam is separately provided plural areas to perform higher-precision measurement. Further, as solving means, low speed scanning is performed in plural directions to change an on/off pattern of an electron beam at high speed scanning by the scanning direction.
Representative construction examples of the present invention will be listed.
(1) Electron beam writing equipment of the present invention has: an electron source; an electron optics system irradiating for scanning an electron beam emitted from the electron source on a sample via deflection means having at least two different deflection speeds and an objective lens to form a desired pattern on the sample; a stage mounting the sample; a mark for beam correction provided on the stage; an electron detector detecting a backscattered electron, a secondary electron or a transmission electron obtained by irradiation of the electron beam; a function moving the electron beam by high speed scanning with the deflection means to repeat formation of a patterned beam; a function moving the electron beam on the mark for beam correction by low speed scanning with the deflection means in synchronization with one cycle of the repetition; and a function detecting a backscattered electron or a secondary electron emitted from the mark for beam correction and near it by the low speed scanning or a transmission electron transmitted through the mark for beam correction to correct the position or the deflection distance of the electron beam or blanking time from the detected result.
(2) Electron beam writing equipment of the present invention has: an electron optics system irradiating for scanning plural electron beams arrayed at a predetermined pitch on a sample via deflection means having plural deflectors having at least two different deflection speeds and an objective lens to form a desired pattern on the sample; a stage mounting the sample; a mark for beam correction provided on the stage; and an electron detector detecting a backscattered electron, a secondary electron or a transmission electron obtained by irradiation of the electron beam, wherein the deflection means has a first deflector for high speed scanning and a second deflector for low speed scanning, the plural electron beams are moved in parallel by high speed scanning with the first deflector to form a patterned beam, the plural electron beams are moved in parallel on the mark for beam correction by low speed scanning with the second deflector in synchronization with formation of the patterned beam, and a backscattered electron or a secondary electron emitted from the mark for beam correction and near it by the low speed scanning or a transmission electron transmitted through the mark for beam correction is detected to correct the position or the deflection distance of the electron beam or blanking time from the detected result.
(3) An electron beam writing method of the present invention has the steps of: irradiating an electron beam emitted from an electron source on a sample via an electron optics system having deflection means having at least two different deflection speeds and an objective lens to form a desired pattern on the sample; high speed scanning the electron beam using the deflection means to repeat formation of a patterned beam; low speed scanning the electron beam on a mark for beam correction provided on a stage mounting the sample with the deflection means in synchronization with one cycle of the repetition; detecting a backscattered electron or a secondary electron emitted from the mark for beam correction and near it by the low speed scanning or a transmission electron transmitted through the mark for beam correction; and correcting the position or the deflection distance of the electron beam or blanking time from the detected result.
REFERENCES:
patent: 5578821 (1996-11-01), Meisberger et al.
patent: 6566885 (2003-05-01), Pinto et al.
patent: 2002/0148961 (2002-10-01), Nakasuji et al.
Journal of Vacuum and Technology, B12, 1992, Sakitani et al, pp. 2759-2763.
Journal of Vacuum and Technology, B5, 1987, Iwadate et al, pp. 75-78.
Gotoh Susumu
Kamimura Osamu
Ohta Hiroya
Sohda Yasunari
Hitachi High-Technologies Corporation
Mattingly Stanger & Malur, P.C.
Wells Nikita
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