Radiant energy – Irradiation of objects or material – Irradiation of semiconductor devices
Reexamination Certificate
2000-08-11
2001-04-24
Arroyo, Teresa M. (Department: 2881)
Radiant energy
Irradiation of objects or material
Irradiation of semiconductor devices
C250S491100, C250S492220, C430S005000, C430S296000
Reexamination Certificate
active
06222195
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to charged-particle-beam exposure devices and charged-particle-beam exposure methods, and particularly relates to a charged-particle-beam exposure device and a charged-particle-beam exposure method which expose a wafer to a charged-particle beam to form a pattern on the wafer.
2. Description of the Related Art
In recent development of increased circuit density of integrated circuits, an exposure technique using a charged-particle beam such as an electron beam has been gradually replacing a conventional photolithography technique as a method of forming a pattern on a semiconductor wafer. An exposure technique using an electron beam includes a variable-rectangle exposure technique and a block exposure technique.
The block exposure technique uses an aperture mask having a plurality of apertures of various pattern shapes. An electron beam is directed to a selected pattern of one or more apertures, and passes through the apertures to form an exposure pattern the same as the selected pattern on the wafer. The aperture mask is provided with aperture patterns repeatedly used during an exposure process. The block exposure technique is particularly effective when most exposure patterns are comprised of a repetition of basic patterns such as in 1G-DRAM chips or 4G-DRAM chips. In this case, patterns which are not repeated on the wafer are formed by using an electron beam having a variable-rectangle shape.
FIG. 1
is a block diagram of an example of an electron-beam-exposure device of the block-exposure type of the related art.
In
FIG.1
, an electron-beam exposure device
100
includes an exposure-column unit
110
and a control unit
150
. The exposure-column unit
110
includes an electron-beam generator
114
having a cathode
111
, a grid
112
, and an anode
113
. The exposure-column unit
110
further includes a first slit
115
shaping the electron beam rectangular, a first lens
116
converging the shaped beam, and a slit deflector
117
deflecting a position of the shaped beam on a block mask
120
based on a deflection signal S
1
. The exposure-column unit
110
further includes second and third lenses
118
and
119
opposing each other, the block mask
120
mounted movably in a horizontal direction between the second and third lenses
118
and
119
, and first-to-fourth deflectors
121
through
124
deflecting the beam between the second and third lenses
118
and
119
based on position information P
1
through P
4
to select one of a plurality of apertures provided through the block mask
120
. The exposure-column unit
110
further includes a blanking
125
cutting off or passing the beam according to a blanking signal, a fourth lens
126
converging the beam, an aperture
127
, a refocus coil
128
, and a fifth lens
129
. The exposure-column unit
110
further includes a dynamic focus coil
130
, a dynamic stigmator coil
131
, an objective lens
132
projecting the beam onto a wafer W, and a main deflector
133
and a sub-deflector
134
positioning the beam on the wafer according to exposure-position signals S
2
and S
3
. The exposure-column unit
110
further includes a stage
135
carrying the wafer to move it in X-Y directions, and first-to-fourth alignment coils
136
through
139
.
The control unit
150
includes memory media
151
comprising a disk or MT recorder for storing design data of integrated circuits, and a CPU
152
controlling the electron-beam exposure device. The control unit
150
further includes a data-management unit
153
, an exposure-management unit
159
, a mask-stage controlling unit
160
, a main-deflector-deflection setting unit
161
, and a stage controlling unit
162
, all of which are connected via a data bus (i.e., VME bus). Exposure data includes main-deflector data and sub-deflector data, and is stored in a buffer memory
154
via the data-management unit
153
prior to the exposure process. The buffer memory
154
is used as a high-speed buffer for reading the exposure data, thereby negating an influence of low-speed data reading from the memory media
151
.
The main-deflector data is set in the main-deflector-deflection setting unit
161
via the exposure-management unit
159
. The exposure-position signal S
2
is output after the deflection amount is calculated, and is provided to the main deflector
133
via a DAC/AMP
170
. Then, the sub-deflection data for exposing a selected field is read from the data-management unit
153
, and is sent to a sub-deflector-deflection setting unit
155
. In the sub-deflector-deflection setting unit
155
, the sub-deflection data is broken down into shot data by a pattern generating unit
156
, and is corrected by a pattern-correction unit
157
. These circuits operate in a pipeline according to a clock signal generated by a clock setting unit
158
.
After the processing of the pattern-correction unit
157
, the signal S
1
for setting a slit size, mask-deflection signals P
1
through P
4
for determining a deflected position on the block mask
120
of the beam deflected according to the signal S
1
after passing through the first slit
115
, the signal S
3
for determining a position on the wafer of the beam shaped by the block mask
120
, and a signal S
4
for correcting distortion and blurring of the beam are obtained. The signal S
1
, the mask-deflection signals P
1
through P
4
, the signal S
3
, and the signal S
4
are supplied to the exposure-column unit
110
via a DAC(digital-to-analog converter)/AMP(amplifier)
166
, a DAC/AMP
167
, a DAC/AMP
171
, and a DAC/AMP
169
. Also, the clock setting unit
158
provides a blanking controlling unit
165
with a B signal. A BLK signal for controlling the blanking operation from the blanking controlling unit
165
is supplied to the blanking
125
via an AMP
168
.
An exposure position on the wafer is controlled by the stage controlling unit
162
. In doing so, a coordinate position detected by a laser interferometer
163
is supplied to the stage controlling unit
162
. Referring to the coordinate position, the stage controlling unit
162
moves the stage
135
by driving a motor
164
.
In this manner, the control unit
150
controls the exposure-column unit
110
such that the electron beam emitted from the electron-beam generator
114
is shaped rectangular by the first slit
115
, converged by the lenses
116
and
118
, deflected by the mask deflectors
121
and
122
, and directed to the block mask
120
. The beam having passed through the block mask
120
passes through the blanking
125
, is converged by the fourth lens
126
, deflected to a center of a sub-field of about a 100-&mgr;m square by the main deflector
133
, and deflected within this sub-field by the sub deflector
134
.
A portion of the block mask
120
for forming aperture patterns are made into a thin layer, and the aperture patterns are formed by etching. As a base for the block mask
120
, a semiconductor plate such as a Si plate or a metal plate is used.
A mask (block mask) used in the block exposure is provided with a rectangle aperture used by the variable-rectangle exposure and with aperture patterns of various complex shapes. In order to achieve a reliable and accurate exposure by using such a mask, the mask must be accurate and free of defections. In particular, when the block exposure technique is applied to mass manufacturing, a reliability of the mask must be guaranteed, so that an inspection technique for the block mask should be established.
For a thorough inspection of the block mask, three different inspections should be conducted in the same manner as for a conventional photo mask, including inspection of a pattern scale, inspection of a pattern position, and inspection of a pattern surface. Minimum scales of block-mask patterns are 10 to 20 times as large as those of photo-mask patterns. Thus, a conventional photo-mask inspection device can be used for pattern-scale inspection and pattern-position inspection of the block masks. As for the pattern-surface inspecti
Kawakami Ken-ichi
Kobayashi Katsuhiko
Ohno Manabu
Sagou Satoru
Sakamoto Kiichi
Arroyo Teresa M.
Fujitsu Limited
Staas & Halsey , LLP
Wells Nikita
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