Radiant energy – Irradiation of objects or material – Irradiation of semiconductor devices
Reexamination Certificate
1999-11-17
2002-06-18
Lee, John R. (Department: 2881)
Radiant energy
Irradiation of objects or material
Irradiation of semiconductor devices
C250S491100
Reexamination Certificate
active
06407398
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electron beam exposure apparatus, more particularly to a technique for measurement of the height of a sample surface in an electron beam exposure apparatus.
2. Description of the Related Art
Advances in microprocessing technology have led to greater integration densities of semiconductor integrated circuits and have resulted in increasingly severe demands on the performance of microprocessing technology. In particular, in exposure, the limit is expected to be reached in the optical exposure technology used in the conventional steppers and the like. Electronic beam exposure is a technique which may well form the basis for the next generation of microprocessing in place of optical exposure.
Electron beam exposure apparatuses include ones of variable aperture (variable size rectangular aperture) exposure, block exposure, and multibeam exposure. Here, the explanation will be given taking as an example the block exposure system, but the present invention is not limited to this. The block exposure system is one in which a pattern of repeating unit graphics is given to a transmission mask, an electron beam is made to pass through it to generate the unit patterns all at once, then these are connected and the repeating unit graphics exposed.
FIG. 1
is a view of the configuration of a beam irradiating system in an electron beam exposure apparatus of the block exposure system. In
FIG. 1
, reference numeral
11
indicates an electron gun emitting the electron beam,
12
a first convergence lens for converging the electron beam from the electron gun
11
to a parallel beam,
13
an aperture for forming the parallel beam passing through it into a predetermined shape,
14
a second convergence lens for focusing the formed beam,
15
a shaping use deflector,
16
a first mask deflector,
17
a deflector for dynamically correcting astigmatism due to the mask,
18
a second mask deflector,
19
a mask use convergence coil,
20
a first shaping lens,
21
a block mask moved by a stage
21
A,
22
a second shaping lens,
23
a third mask deflector,
24
a blanking deflector for controlling the on/off state of the beam,
25
a fourth mask deflector,
26
a third lens,
27
a circular aperture,
28
a reduction lens,
29
a dynamic focus coil,
30
a projection lens,
31
an electromagnetic main deflector,
32
an electrostatic sub deflector, and
33
a reflected electron detector for detecting reflected electrons of the electron beam irradiated on a sample
1
and outputting a reflected electron signal. An electron beam
10
is converged by the projection lens
30
on to a sample (wafer)
1
placed on a stage
2
. The stage is made to move two-dimensionally in a plane vertical to the electron beam
10
. The above parts are housed in a housing called an electron optical mirror tube (column). The inside of the column is evacuated for the exposure. The electron beam exposure apparatus further has an exposure controller for controlling the parts of the column so as to expose a desired pattern, but the explanation of this will be omitted here.
FIG. 2
is a more detailed view of the configuration of the parts of the main deflector
31
and the sub deflector
32
. As shown in
FIG. 2
, the main deflector
31
is comprised of four electromagnetic deflectors
31
a
to
31
d
assembled together. Main deflection data output from a data management circuit
45
is multiplied with deflection efficiencies C
1
to C
4
at a main deflection first processing circuit
42
a
to main deflection fourth processing circuit
42
d
, then converted to analog signals and then amplified at the main deflection first D/A amplifier
41
a
to main deflection fourth D/A amplifier
41
d
and supplied to the electromagnetic deflectors
31
a
to
31
d
. The electromagnetic deflectors
31
a
to
31
d
are made to generate magnetic fields and deflect the electron beam
10
in accordance with the signals supplied to them. For example, as shown in
FIG. 3A
, one electromagnetic deflector is used to deflect the beam and change its position, then another electromagnetic deflector is used to return it to its original direction thereby enabling the position of emission of the electron beam to be changed, but keeping the direction of emission always vertical to the sample
1
. By doing this, even if the height of the sample
1
changes, the exposure position will substantially remain unchanged, so there is the advantage that deterioration of the exposed image can be reduced.
The sub deflector
32
for example is comprised of a ceramic tube on the inner surface of which are formed eight thin metal films extending in the axial direction and serving as electrodes. By supplying voltage to the facing electrodes, an electric field is formed. The incident electron beam is deflected by the electrostatic field. The sub deflection data output from the data management circuit
45
is multiplied with the deflection efficiency D at the sub deflection processing circuit
44
, then converted to an analog signal and amplified at the sub deflection D/A amplifier
43
and supplied to the electrodes. Note that for convenience in illustration, only one of each of the sub deflection processing circuit
44
and the sub deflection D/A amplifier
43
is shown, but there are eight electrodes and therefore in actuality eight sets of the sub deflection processing circuits
44
and sub deflection D/A amplifiers
43
are provided corresponding to the electrodes. Deflection efficiencies D
1
to D
8
are also individually set. As shown in
FIG. 3B
, the electron beam fired into the sub deflector
32
is gradually deflected and emitted at a certain emission angle.
The deflection efficiencies C
1
to C
4
and D
1
are set so as to give deflection positions proportional to the main deflection data and the sub deflection data given.
In general, the main deflector
31
has a larger deflection range, but a slower response speed compared with the sub deflector
32
. Therefore, in the electron beam exposure apparatus, to improve the exposure efficiency, the main deflector
31
and the sub deflector
32
are combined as shown in FIG.
1
and FIG.
2
. When performing exposure, as shown in
FIG. 4
, the deflection range (in actuality a somewhat smaller range)
50
of the main deflector
31
is divided into a plurality of sub regions
51
, the deflection position A of the main deflector
31
is made the center of the sub regions
51
, and the pattern inside a sub region
51
is exposed while changing the amount of deflection B of the sub deflector
32
. Note that the same applies in the case of successively exposing sub regions
51
of the same column while moving the stage.
In the case of an electron beam exposure apparatus used in the process of production of a semiconductor device a semiconductor wafer is used as the sample. A resist is coated on the semiconductor wafer and a pattern is drawn on it by an electron beam. The thickness of the semiconductor wafer is uneven and some warping etc. exists as well. Further, there are changes in height along with movement of the stage. Therefore, there is unevenness in the surface position of the semiconductor wafer placed on the stage
2
, that is, the height of the sample. Therefore, it is necessary to measure the height of the sample and adjust the electron beam so that it converges at that height, that is, to adjust the focus position. The focus position of the electron beam exposure apparatus is mainly determined by the projection lens
30
, but the focus position can be changed within a small range, but at a faster speed by the dynamic focus coil
29
. Therefore, the focus position can be adjusted in accordance with changes in height of the sample by using the dynamic focus coil
29
. Note that in an electron beam exposure apparatus, there is the phenomenon called coulomb interaction in which the electrons of the electron beam react with each other resulting in loss of focus of the beam. The focus position changes according to the amount of th
Kurokawa Masaki
Ohkawa Tatsuro
Ooae Yoshihisa
Advantest Corporation
Christie Parker & Hale LLP
Lee John R.
Quash Anthony
LandOfFree
Electron beam exposure apparatus and exposure method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electron beam exposure apparatus and exposure method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electron beam exposure apparatus and exposure method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2979329