Radiant energy – With charged particle beam deflection or focussing – Magnetic lens
Reexamination Certificate
1999-11-01
2003-01-21
Lee, John R. (Department: 2881)
Radiant energy
With charged particle beam deflection or focussing
Magnetic lens
Reexamination Certificate
active
06509568
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an electrostatic deflector used for deflecting an electron beam in an electron beam radiation apparatus such as an electron beam exposure apparatus or an electron microscope.
An electron beam can be reduced to several tens of nm in diameter, and apparatuses for radiating an electron beam such as an electron microscope or an electron beam exposure apparatus are used. These electron beam radiation apparatuses use a deflector for changing the exposure position of the electron beam converged on a sample. The deflector used for this purpose includes an electromagnetic deflector having a large deflection range but a comparatively low response rate or an electrostatic deflector having a narrow deflection range but a high response rate or a combination thereof. The present invention relates to an electrostatic deflector. Although the description that follows refers to the electrostatic deflector of the electron beam exposure apparatus, as an example, the present invention is not limited to such an deflector but is applicable to any electrostatic deflector used with an electron beam radiation apparatus.
In recent years, the ever-increasing miniaturization and density of integrated circuits has developed to such an extent that a further miniaturization is difficult to achieve by the photolithography which has long been a main stay of techniques for forming a fine pattern. In view of this, an exposure method using a charged particle beam such as an electron beam or an ion beam or a new exposure method using X rays have been studied and realized as a technique replacing the photolithography. Of all these methods, electron beam exposure, which can form a pattern as fine as not more than 0.1 &mgr;m using an electron beam is in the spotlight. At the same time, the electron beam exposure apparatus is required to have an operating stability, a high throughput and a finer micromachinability as a part of a semiconductor mass production system.
A typical conventional electron beam exposure apparatus employs deflection means configured with a combination of an electromagnetic deflector and an electrostatic deflector. The electromagnetic deflector is called a main deflector, and the electrostatic deflector an auxiliary deflector. Generally, the deflection range (main deflection range) of the electromagnetic deflector is divided into several areas (subdeflection range) each smaller than the deflection range of the electrostatic deflector, the deflection position of the electromagnetic deflector is located at the center of each subdeflection range, and each subdeflection range is deflected by the electrostatic deflector. A projection lens for radiating an electron beam of an appropriate section on a wafer is built into the column of the electron beam exposure apparatus. The electromagnetic deflector and the electrostatic deflector are arranged substantially integrally with the projection lens, or specifically, the electrostatic deflector is housed in the electromagnetic deflector.
The use of a metal of a superior machinability and high precision but of a high conductivity for the electrostatic deflector (auxiliary deflector) or the surrounding parts leads to the inconvenience of a lower response rate of the electromagnetic deflector (main deflector) due to an eddy current. This poses a serious problem for the electron beam exposure apparatus requiring a high throughput.
In an attempt to reduce the eddy current, an electrostatic deflector has been formed by plating (for example, with Ni and Au as a base and a surface, respectively) the interior of a cylindrical insulating material (such as alumina). To avoid the problems of the machining precision and the difficulty of the plating process, however, the current practice is to make an electrostatic deflection electrode by grinding an AlTiC (compound of alumina and titanium carbide) ceramic having an almost ideal resistivity and plating it with platinum, which electrode is fixed in a hollow cylinder of an insulative alumina ceramic to make an electrostatic deflector.
FIGS. 1A
to
1
C show a conventional electrostatic deflector of an electron beam exposure apparatus.
FIG. 1A
shows an outer configuration of the electrostatic deflector,
FIG. 1B
a top plan view as taken in line
1
B-
1
B′ in
FIG. 1A
, and
FIG. 1C
a sectional view taken in line
1
C-
1
C′ in FIG.
1
B.
The electrostatic deflector
10
shown in the diagrams is arranged in an electromagnetic deflector constituting a main deflector (not shown) and used as an auxiliary deflector of an electron beam exposure apparatus. As shown, the electrostatic deflector
10
includes a group of electrodes
11
, and a hollow cylindrical holding member
12
with the electrodes
11
fixed therein.
The electrodes
11
are composed of eight AlTiC ceramic electrode members E
1
to E
8
. The electrode members E
1
(i: 1 to 8) are fixedly arranged symmetrically about an axis in the holding member
12
(FIG.
1
B). Each electrode members E
1
is ground into the same shape with the surface formed of a metal film. This metal film is made of a metal of platinum group such as ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir) or platinum (Pt) and formed directly on each surface of the conductive ceramics by electroplating.
The electron beam is a flow of electrons, which when impinged on an insulating material, accumulates the electric charge on the surface of the insulating material. The electric charge thus accumulated has an effect on the surrounding electric field. The electrostatic deflector is for generating an electric field in the electrodes
11
by applying a voltage to each electrode member E
1
and deflecting the incident electron beam with the force of the electric field. The problem is that in the case where the electric field is disturbed by the charge accumulated on the surface of the surrounding holding member
12
, the desired deflection amount cannot be obtained. In view of this, the conventional electrostatic deflector shown in
FIGS. 1A
to
1
C has a structure in which each electrode member Ei has a crank-shaped section so that the inner surface of the holding member
12
is not directly visible from the center axis of the cylinder. With this shape, even when the electron beam is disturbed as it passes through the cylinder, the electrons disturbed impinge on one of the electrode members Ei and are prevented from reaching the inner surface of the holding member
12
.
On the other hand, the holding member
12
is required to insulate the electrode members E
i
from each other and is made of a ceramic insulating material such as alumina. This holding member
12
is formed with wedge-shaped fixing holes
31
having a larger diameter on the outer peripheral surface than on the inner peripheral surface of the holding member
12
. These fixing holes are used for fixing the electrodes
11
(eight electrode members E
1
to E
8
) inside, and two fixing holes (for a total of 16) are formed for each electrode member E
i
. The inner wall portion of each fixing hole
31
is formed with joining metal pads
16
,
17
made of Ti or molybdenum-manganese (Mo—Mn), as a main component, by metallization.
FIG. 2A
shows an electrode member E
i
making up the electrodes, and
FIG. 2B
a sectional view of the electrode member E
i
and the holding member on which the electrode member E
i
is fixed.
Eight electrode members Ei of the same shape are used for constituting the electrodes
11
of the electrostatic deflector and are made by grinding the AlTiC ceramics and plating the surface with platinum. For fabricating the electrode members E
i
, the first step is to grind them into the same shape. Each electrode member E
i
, after the surface thereof is cleaned, is formed with a conductive metal pad
13
by metallization with titanium (Ti), as a main component, constituting a part impressed with a voltage from the driver. Further, joining metal pads
14
,
15
of Ti, as a main component, are formed by metallization at two arbitrary
Abe Tomohiko
Ashiwara Kazuto
Haraguchi Takeshi
Kato Ryoji
Ooae Yoshihisa
Advantest Corporation
Christie Parker & Hale LLP
Lee John R.
Quash Anthony
LandOfFree
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