US-12626886-B2 - Multi charged particle beam writing apparatus

US12626886B2US 12626886 B2US12626886 B2US 12626886B2US-12626886-B2

Abstract

A multi charged particle beam writing apparatus includes two or more-stage objective lenses each comprised of a magnetic lens, and configured to focus the beam on a substrate, n (n≥3) correction lenses correcting an imaging state of the multi charged particle beam, and an electric field control electrode to which a positive constant voltage with respect to the substrate is applied. The electric field control electrode generates an electric field between the substrate and the electrode. The objective lenses include a first objective lens, and a second objective lens placed most downstream in a travel direction of the beam. m (n≥m≥1) correction lenses of the n correction lenses are magnetic correction lenses placed in a lens magnetic field of the second objective lens. (n−m) correction lenses are placed upstream of the lens magnetic field of the second objective lens in the travel direction.

Inventors

Hirofumi Morita
Haruyuki NOMURA

Assignees

NUFLARE TECHNOLOGY, INC.

Dates

Publication Date: 20260512
Application Date: 20231115

Claims (10)

1 . A multi charged particle beam writing apparatus comprising: a plurality of blankers performing blanking deflection on each of beams in a multi charged particle beam; a limiting aperture member blocking a beam in the multi charged particle beam, the beam being deflected by the blanker to achieve a beam-off state; two or more-stage objective lenses each comprised of a magnetic lens, and configured to focus the multi charged particle beam on a substrate, which has passed through the limiting aperture member; n (n is an integer greater than or equal to three) correction lenses correcting an imaging state of the multi charged particle beam on the substrate; and an electric field control electrode to which a positive constant voltage with respect to the substrate is applied, the electric field control electrode generating an electric field between the substrate and the electric field control electrode, wherein the two or more-stage objective lenses include a first objective lens, and a second objective lens placed most downstream in a travel direction of the multi charged particle beam, m (m is an integer such that n≥m≥1) correction lenses of the n correction lenses are magnetic correction lenses placed in a lens magnetic field of the second objective lens, and (n−m) correction lenses that are the n correction lenses other than the magnetic correction lenses are placed upstream of the lens magnetic field of the second objective lens in the travel direction of the multi charged particle beam.
2 . The multi charged particle beam writing apparatus according to claim 1 , wherein the electric field control electrode is disposed in the lens magnetic field of the second objective lens or downstream of the lens magnetic field of the second objective lens in the travel direction of the multi charged particle beam.
3 . The multi charged particle beam writing apparatus according to claim 1 , further comprising an acceleration lens including an electrostatic lens having a plurality of electrodes, the acceleration lens accelerating the multi charged particle beam, wherein the (n−m) correction lenses include an electrostatic correction lens that also serves as the electrode of the acceleration lens.
4 . The multi charged particle beam writing apparatus according to claim 1 , wherein the (n−m) correction lenses include an electrostatic correction lens or a magnetic correction lens which is placed in a lens magnetic field of the first objective lens.
5 . The multi charged particle beam writing apparatus according to claim 1 , wherein the (n−m) correction lenses include a magnetic correction lens placed outside a lens magnetic field of the two or more-stage objective lenses.
6 . The multi charged particle beam writing apparatus according to claim 5 , wherein the magnetic correction lens placed outside the lens magnetic field is placed upstream of the lens magnetic field of the two or more-stage objective lenses in the travel direction of the multi charged particle beam or between the lens magnetic field of the two or more-stage objective lenses.
7 . The multi charged particle beam writing apparatus according to claim 1 , wherein a mutual relationship between amounts of excitation of the n correction lenses is set, and the imaging state of the multi charged particle beam is corrected.
8 . The multi charged particle beam writing apparatus according to claim 7 , wherein the correction of the imaging state is such that an imaging height is changed with a magnification unchanged and no rotation.
9 . The multi charged particle beam writing apparatus according to claim 7 , wherein the correction of the imaging state is such that magnification is changed with no rotation and an imaging height unchanged.
10 . The multi charged particle beam writing apparatus according to claim 7 , wherein the correction of the imaging state is such that rotation is changed with an imaging height unchanged and a magnification unchanged.

Description

TECHNICAL FIELD The present invention relates to a multi charged particle beam writing apparatus. BACKGROUND ART As LSI circuits are increasing in density, the line width of circuits of semiconductor devices is becoming finer. To form a desired circuit pattern onto a semiconductor device, a method of reducing and transferring, by using a reduction-projection exposure apparatus, onto a wafer a highly precise original image pattern formed on a quartz is employed. A so-called electron beam lithography technique, in which a pattern is formed by exposing a resist using an electron beam writing apparatus, is used to produce a highly precise original image pattern. As an electron beam writing apparatus, a writing apparatus using a multi-beam is under active development, which substitutes for a conventional single beam writing apparatus that deflects a single beam and radiates the beam to a desired position on a sample. Use of a multi-beam allows many beams to be radiated as compared to when writing is performed with a single electron beam, thus the throughput can be significantly improved. In a writing apparatus using a multi-beam method, for example, an electron beam emitted from an electron source is passed through a shaping aperture array member having a plurality of openings to form a multi-beam, blanking control is performed on beams by a blanking aperture array substrate, and unblocked beams are reduced by an optical system, and radiated to a sample placed on a movable stage. In the electron beam writing apparatus, beams in each shot are focused on a sample by an objective lens, dynamic focus correction (dynamic focus) is performed during writing using, for example, an electrostatic lens so as to correspond to the irregularities of the sample surface, and the position (imaging height) in the optical axis direction of the multi-beam array image is corrected. Here, the optical axis refers to the central axis of an optical system in the course from emission of an electron beam to irradiation of the sample. However, when dynamic focus is performed, rotation and magnification change occur in the beam array image on the sample, and the writing positional accuracy deteriorates. Thus, the rotation and magnification change of the beam array image due to the dynamic focus is required to be reduced as much as possible. In order to reduce the rotation and magnification change of the beam array image due to the dynamic focus, a multi beam writing apparatus has been proposed, in which three electrostatic lenses are provided, and at least one electrostatic lens is placed in the lens magnetic field of each of two-stage objective lenses (see, for example, PTL 1). When a sample is irradiated with an electron beam, secondary electrons are generated from the sample. The secondary electrons return to the sample surface, and a wide area of the resist on the sample surface is charged, thus a position displaced from a target position may be irradiated with the electron beam. A technique has been proposed (see, for example, PTL 2) in which an electric field to move secondary electrons back to a lower position (in the sample surface direction) is generated, and a charge area is restricted by returning the secondary electrons to the vicinity of the secondary electron generation position (beam irradiation position) so as to improve the accuracy of correction to beam position change due to resist charging. However, with this technique, improvement of the accuracy of beam irradiation position is limited because the amount of charge on the resist surface increases. In general, for a finer pattern, the sensitivity of a corresponding resist tends to decrease. Therefore, when a pattern is made finer, the amount of beam irradiation to the resist increases, and the amount of charge of the resist increases, thus it gets more difficult to achieve a required positional accuracy. It is practiced that an electrostatic lens is operated in a positive voltage range with respect to a sample surface (see, for example, PTL 3). Using this technique, a lifting electric field is generated, by which secondary electrons are guided upward from the sample surface, thus the amount of charge of the resist can be reduced. However, there is a problem in that the voltage applied to the electrostatic lens changes corresponding to a sample surface height during writing, thus the lifting electric field is not constant, and the amount of charge of the resist changes, which prevents the improvement of the accuracy of beam irradiation position on the entire writing region. CITATION LIST Patent Literature PTL 1: JP 2013-197289 APTL 2: JP 2021-180224 APTL 3: JP 2013-191841 A SUMMARY OF INVENTION It is an object of the present invention to provide a multi charged particle beam writing apparatus that can generate a constant electric field to lift secondary electrons and improve the writing accuracy. According to one aspect of the present invention, a multi charged particle be