Electron beam exposure apparatus

An electron beam exposure apparatus is provided with a blanking section to which electron beams emitted from an electron gun whose directions are paralleled through condenser lens are projected. The blanking section includes a slit plate with a plurality of perforations equally spaced for dividing the parallel electron beams into a plurality of electron beam bundles, plural sets of deflection electrodes disposed along the path of the advancing bundles of electron beams passing through the perforations of the slit plate in such a way that each bundle of electron beams passes between each set of deflection electrodes, and a mask plate with a plurality of perforations permitting straight advancing of only the bundles of electron beams passed through the perforations of the slit plate. The blanking section selectively blocks or permits the advancing therethrough of the bundles of electron beams. The bundles of electron beams passed through the blanking section are reduced, or compressed by a projection lens and their directions are pralleled thereby. All of the bundles of parallel electron beams passed through the projection lens are deflected by a deflection apparatus and then projected onto a predetermined region of the photoresist of the wafer. As a result, on the predetermined area on the photoresist of the wafer, the bundles of electron beams are scanned slightly, so that a given pattern is exposed.

BACKGROUND OF THE INVENTION 
The present invention relates to an electron beam exposure apparatus. 
The electron beam exposure apparatus is used to expose a given pattern on 
the photoresist of the wafer in the manufacturing process of semiconductor 
integrated circuit device. The electron beam exposure apparatus is 
superior to the ultraviolet exposure apparatus when it is intended to 
integrate in high density semiconductor devices. In the ultraviolet 
exposure apparatus, the diffraction of ultraviolet restricts the 
resolution limit so that the minimum width of the exposure pattern is at 
most 2.mu.. Further narrower width thereof is almost impossible. To the 
contrary, in the case of the electron beam exposure apparatus, the minimum 
width of the exposure pattern is about 0.1.mu. for the reason that the 
wave length of the electron beam is very short as compared to that of the 
ultraviolet and thus the affect of diffraction is small, thereby enabling 
a very small resolution limit. 
Generally, the electron beam exposure apparatus is classified into electron 
beam scanning type exposure apparatus and electron beam projection type 
exposure apparatus. The electron beam scanning type exposure apparatus is 
such that a single electron beam is used to scan the photoresist on the 
wafer and projection and non-projection are repeated every scanning unit 
in accordance with the exposure pattern. The electron beam projection type 
exposure apparatus uses a foil mask of the so called self-supporting type 
consisting of a plurality of masks permitting electron beams configured in 
a predetermined pattern to pass therethrough. The parallel electron beams 
are irradiated onto the foil mask to form an image on the photoresist of 
the wafer. Both the exposure apparatuses of the electron beam scanning 
type and the electron beam projection type are suitable for the high 
density integration of semiconductor devices, as compared to the 
ultraviolet exposure apparatus. However, these apparatuses suffer from 
some disadvantages and present problems in practical use. 
As mentioned above, a single electron beam scans the wafer in the electron 
beam scanning apparatus. For this, various types of patterns may be easily 
and precisely exposed. But this type exposure apparatus takes a relatively 
long time for one time pattern exposure. In the manufacturing process of 
semiconductor devices, several time exposures of the pattern are 
necessary. Therefore, the electron beam scanning exposure apparatus is 
improper in application for the mass production of the semiconductor 
integrated circuit devices. 
On the other hand, the electron beam projection type exposure apparatus 
takes a very short time, for example, several seconds, for one time 
exposure of the pattern and has a very deep focal depth. With the deep 
focal depth, the pattern may be exposed precisely even if the wafer is 
deformed or the moving stage vertically moves a slight degree. However, it 
is very difficult to make precisely the foil mask. More adversely, such a 
precise foil mask must be made separately for individual circuit 
constructions of semiconductor devices. Thus, the electron beam projection 
type exposure apparatus is defective in this regard. 
SUMMARY OF THE INVENTION 
Accordingly, the primary object of the present invention is to provide an 
electron beam exposure apparatus in which a pattern may be exposed rapidly 
and precisely. 
Another object of the present invention is to provide an electron beam 
exposure apparatus in which the pattern exposure may be made easily and 
inexpensively, and versatilely for different circuit constructions of 
semiconductor devices. 
The present invention may be briefly summarized as involving an electron 
beam exposure apparatus comprising: an electron gun; condenser means for 
paralleling the electron beams emitted from the electron gun; blanking 
means in which the parallel electron beams passed through the condenser 
means are divided into a plurality of electron beam bundles and the 
plurality of electron beam bundles are selectively intercepted; deflection 
means for deflecting in a predetermined direction all the bundles of 
parallel electron beams passed through the blanking means; and stage means 
on which a wafer to be scanned by the bundles of electron beams deflected 
by the deflection means is placed and by which the wafer is moved by a 
predetermined distance. 
Other objects and features of the present invention will be apparent upon a 
careful consideration of the following description when taken in 
conjunction with the accompanying drawings, in which:

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Reference will be made to FIG. 1 illustrating a schematic diagram of an 
electron beam exposure apparatus according to the present invention. In 
the figure, the electron beam exposure apparatus comprises an electron gun 
2, a condenser generally indicated at 4 for paralleling the electron beams 
emitted from the electron gun 2, a blanking apparatus generally indicated 
at 6 in which the paralleled electron beams are divided into a plurality 
of bundles of electron beams paralleled in advancing direction and the 
passing and interception of the bundles of the parallel electron beams are 
controlled, and a lens means 8 condensing the bundles of parallel electron 
beams for irradiation. The electron beam exposure apparatus further 
includes a deflection means generally designated by reference numeral 10 
and a stage means generally designated by 14 on which a wafer 12 to be 
irradiated by electron beams is placed and movable with the stage means 
14. 
The electron gun 2 connected with a high voltage generating means (not 
shown) generates electron beams, for example, of 20KV for the acceleration 
voltage and 800 .mu.A for the beam current. 
The condenser 4 includes first, second and third condenser lens 16, 18 and 
20, in which the electron beams emitted from the electron gun 2 are 
diverged and condensed to form parallel electron beams in turn directed to 
a blanking plate 22. The coils of the respective condenser lenses 16 to 20 
are supplied with coil currents. The electron beams passing through the 
condenser lenses are controlled, more particularly by the magnetic field 
developed by the coil current. 
The blanking apparatus 6 includes a blanking section 22 and a blanking 
section control means 24. The detail of the blanking section 22 is shown 
in FIG. 2. As shown, the blanking section 22 includes a slit plate 26, a 
mask plate 28 disposed facing the slit plate 26, a plurality of pairs of 
electrodes 30 each pair having electrodes facing each other, a pair of 
substrates, such as sapphire substrate plates 32 and 34, disposed facing 
each other onto which the electrodes 30 are mounted, and a pair of spacers 
36 and 38 for spacing by a predetermined distance sapphire plates 32 and 
34. As shown, sapphire plates 32 and 34 and the spacers 36 and 38 are 
assembled into a frame 40 with a pair of openings. Both the openings are 
fixedly closed by the slit plate 26 and the mask plate 28, respectively. 
These plates are made, for example, of gold foil. A plurality of 
rectangular or circular perforations 42 and 44 are correspondingly formed 
on the respective plates 26 and 28. The perforations of one plate are 
aligned on a rectilinear line with corresponding peforations of the other 
plate. Moreover, these perforations formed in each plate are equally 
spaced in distance. The perforations 42 of the plate 26 are substantially 
equal in size and configuration to each other and the same thing is true 
with the perforations 44 of the plate 28. However, it is not necessary 
that both the perforations 42 and 44 for the plates 26 and 28 be 
substantially equal in size and configuration. The perforations 42 and 44 
of the respective plates are disposed such that the center of each 
perforation of one plate horizontally coincides with the corresponding one 
of the other plate. 
The slit plate 26 divides the parallel electron beams aligned in direction 
by the condenser lens 20 into the plurality bundles of electron beams 
through the perforations 42 of the slit plate 26. More precisely, some 
electron beams pass through the perforations and some electron beams 
bombard the surface of the slit plate 26, thereby being blocked or 
intercepted for further transmission. In this manner, the electron beams 
are divided into a plurality of electron beam bundles. The electrodes 30 
are disposed so that each bundle of electron beams passes between a pair 
of opposed electrodes 30. 
The respective pairs of the electrodes 30 are connected to the blanking 
section control unit 24 and are properly controlled according to the 
commands from a computer 46. As shown in FIG. 3, when the blanking section 
control unit 24 does not apply a voltage to a particular pair of 
electrodes 30, the bundles of electron beam passed through the respective 
perforation 42 of the plate 26 travel through these electrodes 30 and the 
respective perforation 44, straightforwardly. Conversely, when a voltage 
from the blanking section control unit 24 is applied to a particular pair 
of electrodes 30, the electric field developed between the electrodes 
bends the direction of the advancing bundles of electron beams so that the 
bundles of electron beams deviate from the respective perforation 44 to 
hit the plate 28 surface, as shown in FIG. 4. In response to the commands 
fed from the computer 46, the blanking section control unit 24 controls 
the respective pairs of electrodes as mentioned above so that only 
selected bundles of electron beams are permitted to continue to be 
transmitted. In other words, the mask plate 28 serves as a mask and, 
through the control of the blanking section control unit 24, a 
predetermined number of electron beams bundles are permitted to pass 
through the mask plate 28. 
The lens means 8 includes a first projection lens 48 for focussing the 
bundles of electron beams passing through the perforations 44 of the mask 
plate 28, a positioning coil 50 disposed close to the focal point of the 
first projection lens 48, a collimeter 52 positioned at the same place, a 
positioning control unit 54 for controlling the positioning coil 50, and a 
second projection lens 60 for paralleling the bundles of electron beams 
focussed by the first projection lens 48 for irradiating the wafer 12. The 
bundles of electron beams from the mask plate 28 are compressed to 1/10 
the diameter of the electron beam bundles and irradiate the wafer 12. The 
positioning coil 50 is controlled by the coil current fed from the 
positioning control unit 54 in order to slightly shift the position of the 
focal point of the electron beam bundles passed through the first 
projection lens 48 on the focal point surface of the first projection lens 
48 to change the irradiation region of the beam bundles. The positioning 
control unit 54 controls the positioning coil 50 in response to the 
command from the computer 46. 
The deflection means 10 comprises a pair of X-deflection electrodes 62 and 
a deflection control unit 64 for controlling the X-deflection electrodes 
62. The deflection control unit 64, upon receipt of a command from the 
computer 46, applies a voltage to the deflection electrodes 62 to develope 
an X-directional electric field between the deflection electrodes 62. The 
X-directional electric field deflects all the bundles of electron beams in 
parallel travelling through the second projection lens 66 in the direction 
of X as indicated by the arrow, in FIG. 1 with the result that the total 
of the parallel electron beam bundles swings in a given direction for a 
given period of time. The deflection means 10 may be further provided with 
a pair of Y deflection electrodes indicated at 63, in addition to the 
X-deflection electrodes 62. The Y-deflection electrodes 63 keep in the 
Y-direction by a predetermined value deflection of the parallel electron 
beam bundles for the time that the X-deflection electrodes 62 deflect in 
the X-direction the electron beam bundles. If after the X-deflection 
electrodes 62 are operated one time, the Y-deflection electrodes 63 are 
operated and then the X-deflection electrodes 62 are again operated, the 
irradiation region of the parallel electron beam bundles is enlarged. 
The stage means 14 is comprised of a stage 66 on which the wafer 12 is 
placed, a stage moving unit 68 for moving the stage 66, a stage moving 
control unit 70 for controlling the stage movement and a monitor means 72 
for measuring the movement of the wafer 12 moved by means of the stage 
moving unit 68, e.g. a laser interferometer. The stage moving control unit 
70 is operated in response to the command of the computer 46. After the 
electron beam bundles are deflected in the X-direction by the X-deflection 
electrodes 62, the table 12 is moved in the Y-direction substantially 
normal to the X-directon and when the exposure on the given region of the 
wafer 12 is completed, the table 12 is again moved in the X-direction. 
The computer 46 includes a memory device (not shown) storing therein the 
information coded of the given pattern of the photoresist on the wafer to 
be exposed. More precisely, the memory device stores the information code 
of the patterns, for example, to be exposed defined by the given rows and 
columns, e.g. columns 191 to 200 and rows 1 to 19 as shown in FIG. 5. The 
contents of the memory device is fed to the blanking section control means 
24. 
Incidentally, although not shown in the figure, a position detector for 
detecting the position of the pattern is installed in the electron beam 
exposure apparatus. The pattern position detector detects the reference 
position of the pattern depicted on the wafer. Generally, in the 
manufacturing process of semiconductors, a plurality of patterns are 
subsequently formed; however, if the position of the pattern is improper, 
the semiconductor apparatus will not operate properly. It is for this 
reason that the reference position of the pattern formed on the wafer 12 
must be detected. The results of the measurement by the pattern position 
detector are transferred to the computer 46 and then compared with the 
pattern to be exposed. On the basis of this comparison, the computer 46 
issues the corresponding commands relating to the positioning to the stage 
moving control unit 70 and the positioning control unit 54. 
The description to follow is the operation of the electron beam exposure 
apparatus thus constructed. 
Assume now that exposure will be made of a pattern on the wafer 12, as 
shown in FIG. 6. In this case, the wafer is about 8 cm in its diameter, 
and the region to be exposed is a square of 4 cm .times. 4 cm. A part of 
the pattern is illustrated in FIG. 5. In other words, the photoresist on 
the wafer is exposed with such the pattern. Further, 200 perforations 42 
and 44 are formed to each plate 26 and 28, respectively. The blanking 
section 22 irradiates 200 bundles of parallel electron beams. More, the 
perforations 44 are squares of 2.mu. .times. 2.mu., and the 
center-to-center distance of adjacent perforations is 100.mu.. The mask 
plate 28 is a rectangular plate of 10.mu. in width and 21 mm in length. 
The reduction magnification of the lens means 8 is 1/10. .+-.5.mu. is the 
deflection distance on the wafer 12 of the bundles of electron beams by 
the X-deflection electrodes 62. A single bundle of electron beams scans an 
area of 10.mu. .times. 0.2.mu. on the wafer 12. 
When the wafer 12 is placed on the stage 66, the electron beam exposure 
apparatus starts to operate. When the pattern is already formed on the 
wafer 12, the pattern position detector (not shown) detects the reference 
position of the pattern. The detection result is fed to the computer 46, 
and then is compared with the pattern to be exposed. On the basis of the 
comparision result, the computer transfers the stage moving command to the 
stage moving control unit 70 and the positioning command to the 
positioning control unit 54. In response to the command, the stage moving 
control unit 70 moves the stage moving unit 68 to position or align the 
wafer 12 on the stage 66 at a predetermined position. The positioning 
control unit 54 controls the positioning coil 50 and the positioning 
collimeter 52 to slightly change the focal position of the first 
projection lense 48. The slight change of the focal position of the first 
projection lens 48 ensures a precise irradiation of the pattern onto the 
wafer 12. 
After completion of the positioning of the wafer 12, the electron gun 2 
emitts electrons which in turn travel to the blanking section 22 through 
the condenser means 4. The electrons are divided into 200 bundles of 
electron beams in the blanking section 22. The blanking section 22 is 
controlled by the blanking section control unit 24, depending on the 
blanking command from the computer 46. The blanking section 22 controls 
the respective 200 sets of electrodes 30 mounted on sapphire plates 26 and 
28 corresponding to the 200 perforations 42 and 44. For example, when the 
pattern to be exposed exists at the position defined by the column 194 and 
the row 6, no voltage is applied to the 194th electrodes 30. As a result, 
the electron beams advance straight forwardly, as shown in FIG. 3, and 
pass through the 194th perforation of the mask plate 28 to irradiate the 
photoresist on the wafer 12. When the pattern does not exist at the 
position of the 195th column and the 6th row, the voltage is applied to 
the 195th electrodes 30. Therefore, the bundles of electron beams are 
bent, as shown in FIG. 4, to hit the mask plate wall 28. The result is 
that no electron beam bundle is emitted from the 195th perforation and 
thus the photoresist on the corresponding position on the wafer 12 is not 
irradiated by electrons. The same controls are made simultaneously to the 
electrodes 1st to 200th, and thus the pattern corresponding to one line is 
exposed on the photoresist on the wafer 12. 
As described above, each of the perforations 44 of the mask plate 28 has a 
size of 2.mu. .times. 2.mu. so that the bundle of electron beams passed 
therethrough has a cross section of 2.mu. .times. 2.mu.. Further, the 
center-to-center distance of adjacent perforations 44 disposed linearly on 
the mask plate 28 is 100.mu.. Accordingly, the center-to-center distance 
of adjacent bundles of electron beams must be integral multiples of 
100.mu.. These bundles of electron beams are totally reduced by 1/10th of 
the cross section of the electron beams bundle to expose the photoresist 
on the wafer 12. Each of the bundles of electron beams passed through the 
lens means 10 have the cross section of 0.2.mu. .times. 0.2.mu. and the 
distance between adjacent bundles of electron beams is integral multiples 
of 10.mu.. Therefore, if the bundles of electron beams are irradiated onto 
the wafer 12 without any modification, the exposure onto the photoresist 
of the wafer 12 is made merely with a plurality of scattered square dots 
of 0.2.mu. .times. 0.2.mu. whose center-to-center distance is spaced by 
integral multiples of 10.mu.. However, the deflection electrodes 62 
deflect .+-.5.mu., i.e. 10.mu., all the bundles of electron beams on the 
wafer 12, as previously mentioned, with the result that the rectangular 
region of 0.2.mu. in width .times. 10.mu. in length is exposed on the 
wafer and thus the 200 rectangular regions 0.2.mu. .times. 10.mu. may all 
be exposed. Therefore, if the region defined by the column and row is 
0.2.mu. in width and 10.mu. in length, one time irradiation of the 
electron beams enables the exposure to be made over the entire area of 200 
regions, i.e. of 0.2.mu. .times. 2 mm (10.mu. .times. 200.mu.). 
When the exposure of the pattern on the region designated by the 6th row is 
completed, none of the electron beam bundles are projected temporarily 
from the blanking section 22, as shown in FIG. 4, through the control of 
the blanking section controlling unit 24. Thus, in such a case, the 
bundles of electron beams are all deflected temporarily and none of the 
electron beams are emitted from the blanking section 22. Alternately, the 
bundles of electron beams may be discontinuously, i.e. intermittently, 
projected into the blanking section 22. For realizing such an intermittent 
projection, a shutter mechanism (not shown) may be provided in the 
electron beam irradiation direction of the electron gun, as an example. 
Continuing now with the description of the operation of the electron beam 
exposure apparatus according to the present invention, when the bundles of 
electron beams are not irradiated onto the photoresist of the wafer 12, 
the stage moving unit moves and thus the wafer 12 placed thereon moves by 
0.2.mu. in the Y-direction, i.e. in the counter direction indicated by 
arrow 78 (FIG. 6) so that the wafer 12 is positioned ready for exposure of 
the pattern onto the region designated by the 7th row (FIG. 6). Then, the 
exposure of the pattern is made onto the region of the photoresist of the 
wafer 12 defined by the 7th row, in the above-mentioned manner. The stage 
moving control unit 70 drives the stage moving unit 68, upon receipt of 
the command from the computer 46 when the first irradiation of the bundles 
of electron beams onto the photoresist of the wafer 12 is completed. The 
monitor 72 such as, for example, a laser interferometer, measures the 
movement of the wafer 12 moved by the stage moving unit 66 and transfers 
the measurement results to the computer 16. On the basis of the 
measurement results, the computer 46 issues a command to the stage moving 
control unit 70 which in turn controls the stage moving unit 68. In this 
way, the wafer 12 on the stage 66 is displaced properly in the Y-direction 
designated by arrow 78 in FIG. 6, for example, by 0.2.mu.. 
After 200,000 of the above-mentioned exposures, the exposure over the area 
having the length of 4 cm (0.2.mu. .times. 200,000) is completed, as 
shaded in FIG. 6. When such exposure over the shaded area is completed, 
the movement command from the computer 46 drives the stage moving control 
means 70 which in turn moves the stage moving unit 68. Thus, the stage 66 
moves by 2 mm in the X-direction. This movement of the stage 66 places the 
wafer 12 in position for another exposure over the area 0.2.mu. in width 
.times. 2 mm in length. With progression of the exposure over such an area 
by electron beams, the wafer 12 moves stepwise in the Y-direction 
designated by arrow 80 (FIG. 6) with an interval 0.2.mu.. 
After 20 of the 4 cm .times. 2 mm area exposures, the exposure of the 
entire desired pattern onto the wafer 12 is complete. At this time, the 
electron beam exposure apparatus stops its operation. 
In the thus far described example, the electron beam exposure apparatus 
does not use the Y-deflection electrodes 63. It is to be noted, however, 
that if the Y-deflection electrodes 63 are used, the irradiation area of 
the bundles of electron beams may be enlarged, thereby increasing the 
movement distance of the stage 66. For example, for .+-.0.2.mu. of the 
deflection range of the bundles of parallel electron beams by the 
Y-deflection electrodes 63, the area of 0.6.mu. .times. 2 mm is exposured 
before the stage 66 is moved. As shown in FIGS. 7 and 8, the bundles of 
parallel electron beams deflected by (K), or +0.2.mu. in the Y-direction, 
are deflected in the + X-direction so that the area 82 of 0.2.mu. .times. 
2 mm is exposed. Then, the advancing bundles of electron beams without any 
deflection in the Y-direction are deflected in the -X direction so that 
the area 0.2.mu. .times. 2 mm indicated as 84 is exposed. Further, the 
bundles of parallel electron beams deflected by (-K), i.e. -0.2.mu. in the 
Y-direction, are deflected in the + X-direction to expose an area 0.2.mu. 
.times. 2 mm designated by reference numeral 86. As a result, the pattern 
0.6.mu. .times. 2 mm is exposed without any movement of the stage 66. The 
similar exposure operation will be repeated after 0.6.mu. movement of the 
stage 66. Consequently, in the case of use of the Y-deflection electrodes 
63, a large area may be exposed with a small number of stage movement 
times and thus the number of detection times of the movement distance of 
the wafer may be reduced. 
It is to be noted that, in the above-mentioned embodiment, a single bundle 
of electron beams passed through the blanking section irradiates the area 
0.2.mu. .times. 10.mu.; however, only 0.2.mu. .times. 0.2.mu. of the 
minimum area may be exposed. The single area 0.2.mu. .times. 10.mu. is 
designated by the row and column as shown in FIG. 5. However, when 
transmission of the bundles of electron beams therefor temporarily ceased 
in response to action of the blanking section 52, only the 0.2.mu. .times. 
0.2.mu. area in the 0.2.mu. .times. 10.mu. area defined by the row and 
column may be irradiated. Let us consider this with a particular case of 
the single bundle of electron beams 88, referring to FIG. 9. It is assumed 
that the single bundle of electron beams 88 may irradiate the area 0.2.mu. 
.times. 10.mu. indicated as 90, on the wafer 12, through the operation of 
the X-deflection plate 62. As previously described, during the time period 
that the bundle of electron beams 88 passes between a pair of blanking 
electrodes 30, no electric field is developed therebetween. When a voltage 
is temporarily applied to the electrodes, the bundle of electron beams is 
shut off by the blanking section 22. Therefore, only the shadowed area 92, 
for example 0.2.mu. .times. 0.3.mu., in the area 90 is exposed. Thus, if 
this fact is used, the exposure area on the wafer 12 may be exposed not 
only by defining it by the row and column but also by changing the voltage 
impression time to the blanking electrodes 30, although the exposure area 
in the later case is a part of that defined by the row and column. The 
exposure area in this case corresponds to the projection area of the 
bundle of electron beams 88, 0.2.mu. .times. 0.2.mu., as the minimum one. 
According to the electron beam exposure apparatus thus far mentioned of the 
present invention, the exposure time may be shortened by 1/200th as 
compared with that of the conventional exposure apparatus of the electron 
beam scanning type. The reason for this is that a number of electron beam 
bundles, for example, 200 bundles, formed by the blanking section 
irradiate simultaneously the wafer 12, while a single bundle of electron 
beams irradiates the wafer 12 in the conventional exposure apparatus. 
Further, the deflection of the bundles of electron beams is small compared 
with the conventional exposure apparatus so that compensation of the 
deflection of electron beams is not needed, ensuring a precise electron 
beam control. 
Moreover, the pattern exposure may be made more precise compared with the 
conventional exposure apparatus of the electron beam projection type. In 
the conventional one, a pattern mask is used and a high precision is 
always required for the pattern mask. Therefore, if the pattern is 
complex, it is very difficult to prepare such a complex pattern mask. On 
the other hand, although the pattern precision in the case of the present 
invention depends to some degree on the precision of the perforations 44 
of the mask plate 28 of the blanking section 22, these perforations 44 are 
rectilinearly arranged and the configuration of the perforation 44 is 
circular or square. For this, the perforations may be formed easily and 
precisely. 
Moreover, the bundles of electron beams irradiated onto the photoresist of 
the wafer 12 are substantially parallel and their deflection angle is very 
small. Therefore, the depth of focus is deep. In other words, even if the 
photoresist on the wafer is uneven, the pattern is precisely formed on the 
wafer. 
Additionally, since the desired pattern is stored in the memory device of 
the computer, any desired pattern may easily be obtained by changing the 
contents of the memory. 
As seen from the foregoing description, according to the electron beam 
exposure apparatus of the present invention, any desired pattern may be 
exposed remarkably precisely and rapidly on the photoresist of the wafer. 
Therefore, the exposure apparatus of the present invention is suitable for 
mass production of semiconductor devices. 
Various other modifications of the disclosed embodiment will become 
apparent to the person skilled in the art without departing from the 
spirit and scope of the present invention as defined by the appended 
claims.