JPH065499A - Aperture diaphragm, manufacturing method thereof, and charged beam drawing apparatus using the same - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] The purpose is to perform high-precision and high-speed electron beam drawing with an aperture diaphragm that can be easily exchanged and adjusted. [Structure] A charged beam drawing apparatus is provided with an aperture diaphragm in which a plurality of aperture diaphragms 4 and 8 are fixed to the same fixing jig 17, a preliminary exhaust chamber 51 for exchanging the aperture diaphragm, and a ground wire. [Effect] The replacement time and the adjustment time can be greatly shortened, high-accuracy voltage and high-current beam can be used for high-precision drawing, and high-speed processing can be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aperture stop for a charged beam drawing apparatus used for manufacturing semiconductor devices and the like.
In particular, the present invention relates to an aperture stop of a variable-shape drawing apparatus that controls a beam shape by a plurality of aperture stops and a collective-beam irradiation type charged beam drawing apparatus that internally includes a plurality of pattern shapes.

[0002]

2. Description of the Related Art A conventional aperture aperture control for controlling the shape of a charged beam in a drawing apparatus is disclosed in JP-A-59-158518 and JP-A-64-21852 even when it has a plurality of apertures. Aperture diaphragms each having a one-piece structure are individually fixed in the housing. Further, no particular consideration was given to the method of fixing these aperture diaphragms.

[0003]

In the prior art, even when the aperture aperture diaphragm for controlling the shape of the charged beam is composed of a plurality of aperture diaphragms, each aperture diaphragm is individually fixed in the housing. For this reason, when the aperture diaphragm was contaminated or damaged, it was necessary to break the vacuum of the housing and disassemble the apparatus housing.
Further, when assembling after replacing the aperture diaphragm, it was necessary to align the openings in the housing. Regarding the temperature rise of the aperture diaphragm due to beam irradiation, sufficient consideration has not been given to heat conduction from the aperture diaphragm to the outside, and even if the current applied to the aperture diaphragm is limited by the upper aperture diaphragm, The generated heat accumulates inside. Therefore, a position drift occurs due to thermal expansion accompanying the temperature rise until the temperature rises gradually and reaches a steady state. Further, the material of the aperture diaphragm provided in the upper portion that absorbs the most current is limited to the refractory metal. In addition, no consideration is given to scattered electrons from the aperture stop that are generated during beam irradiation. These scattered electrons collide with the side wall of the housing to charge the housing, cause contamination on the surface of the housing, and cause beam drift on the sample.

However, with the miniaturization of semiconductor elements, an aperture stop with high shape controllability is required, and at the same time, a beam with a high current density is required in order to improve productivity, so that it is possible to improve the thermal accuracy. A stable aperture stop is required.

It is an object of the present invention to provide an aperture diaphragm which is easy to replace and does not require adjustment after replacement, a manufacturing method thereof, and a drawing apparatus using the same. Similarly, it is to provide an aperture stop which has high beam shape control accuracy and is stable both in terms of heat and accuracy, a manufacturing method thereof, and a drawing apparatus using the same.

[0006]

The objects relating to the ease and accuracy of the above replacement can be solved by fixing a plurality of aperture diaphragms to the same fixing jig. In addition, similarly, the purpose regarding the characteristics that the beam shape control accuracy is high and that is stable both thermally and accurately is to bond the aperture diaphragm to the fixing jig with a conductive adhesive and To solve this problem by providing an aperture stop with a large opening size and a similar opening at the upper or lower part of the aperture stop, and by electrically fixing the fixing jig incorporating these aperture stops in the drawing device. To be done.

[0007]

In the present invention, a plurality of aperture diaphragms are fixed to the same fixing jig. The fixing to the fixing jig can be performed before being incorporated into the body, and can be accurately adjusted in advance by using an adjustment observation device such as an optical microscope or a scanning electron microscope. In the alignment using the above-mentioned device, since the distance between the aperture diaphragms in the fixing jig is within 1 cm, the adjustment can be performed within the same focus, so that the alignment can be performed with high accuracy. Therefore, when replacing the aperture, it is sufficient to take out the fixing jig together with the fixing jig and insert the fixing jig having a new aperture diaphragm therein. At the time of this replacement, by providing the drawing apparatus with a vacuum pre-evacuation chamber having a volume capable of accommodating the fixing jig, the replacement can be performed in a short time without breaking the vacuum of the housing.

A conductive adhesive is used to fix the aperture diaphragm to the fixing jig. Since the thermal contact between the aperture diaphragm and the jig is a point contact when the ordinary screw or the like is fixed, only the radiation of the aperture diaphragm itself can be released. On the other hand, when fixing with a conductive adhesive, the aperture diaphragm and the jig are in surface contact. Since the thermal resistance of the conductive adhesive is equal to 0, there is no difference in temperature between the aperture diaphragm and the jig. By making the fixing jig metallic and grounding it when fixing it to the drawing apparatus, the electric charge and heat accumulated in the aperture diaphragm can be released. Further, in order to increase the contact area between the aperture diaphragm and the fixing jig, a lattice-shaped heat radiation thick film portion is provided on the aperture diaphragm and fixed to the jig, so that the heat transfer effect is further obtained.

For the aperture diaphragm for beam shaping, an aperture diaphragm having an aperture size slightly larger than a desired beam size is prepared. The effect of setting this aperture diaphragm on the upper portion of the aperture diaphragm for forming a desired beam shape is as shown in the known example, and all the extra beam is absorbed by this aperture diaphragm by the upper aperture diaphragm. Therefore, the beam absorbed by the aperture stop is only the difference from the aperture size of the upper aperture stop. Therefore, the temperature rise due to the heat generated when the beam is shielded can be suppressed low. Further, unlike the known example, in the present invention,
Since these aperture diaphragms are integrated and heat dissipation of the upper aperture diaphragm can also be performed by heat conduction, it is not necessary to limit the material of the upper aperture diaphragm to high melting point metal, as shown in the known example. Higher semiconductor material can be used. Further, since the side wall between the aperture diaphragms is shielded by the surface of the fixing jig made of metal and this fixing jig is electrically grounded, the electrons scattered at the aperture edge are generated by the upper aperture diaphragm. Alternatively, it is absorbed by the side wall of the jig. For this reason, the scattered electrons in the housing can be significantly reduced, and thus the beam drift caused by the charging due to the insulator exposed in the housing can be eliminated. By installing a similar aperture diaphragm below the shaping aperture diaphragm, the same effect can be obtained for forward scattered electrons due to the aperture edge.

Further, according to the present invention, also in the case where the aperture shape is arbitrary or a large number such as in the collective figure irradiation method, similarly, all of the above are provided by providing an aperture stop having a similar shape and having the same numerical aperture and position. The effect can be obtained.

[0011]

EXAMPLES Examples of the present invention will be described below.

<First Embodiment> A case where the present invention is applied to a drawing apparatus of the collective figure irradiation method will be described as an example.

In the collective figure irradiation method, as shown in FIG. 4, first, an electron beam 16 emitted from an electron gun 1 which is an electron source.
After irradiating the desired aperture of the aperture diaphragm 4 with the deflector 2, the deflector 6 and the lenses 5 and 7 swing back and deflect the beam formed by the aperture of the arbitrary shape on the second shaping aperture diaphragm 8. Container 10, lens 11, 12, 14,
The deflector 13 reduces the size on the sample wafer 15 and draws a pattern. In the conventional drawing apparatus, each of the first rectangular shape control aperture 4 and the second arbitrary shape control aperture 8 is composed of one aperture stop. These aperture diaphragms are made of silicon single crystal in order to obtain a processing accuracy of 0.5 μm or less. When a beam is applied to these aperture diaphragms, all the beams other than the aperture used for shape control are absorbed by the aperture. This absorbed beam becomes heat. The beam diameter irradiated on the first aperture is 600
In the case of a beam with an acceleration voltage of 50 kV and a current amount of 15 μA at μmφ, the temperature of the aperture becomes a high temperature of 800 ° C. or higher.
At this time, thermal expansion occurs, so that the aperture position is 10
μm shifted. The reduction ratio of this drawing device onto the sample is 2
Since it is 1/5, the thermal drift on the sample is 0.4 μm.
Becomes In drawing with a minimum processing dimension of 1 μm or less, a positional accuracy of 0.25 μm or less is required, and thus a pattern connection failure occurs. On the other hand, in the second aperture diaphragm 8, the absorption current was 3.6 μA, and therefore the temperature rise was 200 ° C. at maximum. Further, when a current amount of 15 μA or more was increased on the first aperture 4, the temperature became 1400 ° C. or more and the aperture was melted. This beam current amount is a parameter that determines the drawing processing speed. The processing amount increases as the current amount increases, and therefore the current amount needs to be 15 μA or more.

As a method of preventing this, there is a method of absorbing an excessive beam by providing an aperture diaphragm 311 having a wide opening angle on the aperture diaphragm as shown in a known example. In this method, the aperture diaphragm 311 is fixed in the housing, but the housing must be disassembled in order to align the lower aperture diaphragm 4 with the electron beam on the same axis. Further, as for the aperture diaphragm 4, it is necessary to adjust the positions of the aperture diaphragm 311 and the aperture diaphragm 4 each time when a plurality of different apertures are selected or when the aperture diaphragm 4 is replaced. The adjustment under the above-mentioned use conditions requires an accuracy of 50 μm or less, so that not only the skill of the operator is required but also the adjustment time takes about 1 hour. Further, if there is a portion where the insulating material such as electric wiring is exposed between the aperture diaphragm 311 and the aperture diaphragm 4, charging by electrons scattered between the two aperture diaphragms occurs and the beam position is 0.3 μm on the wafer 15. It has changed. Further, unless a heat dissipation path by heat conduction is provided outside all of the plurality of aperture diaphragms, the temperature of each aperture diaphragm becomes high, and the aperture diaphragm 311 having a particularly large absorption current has a high temperature of 1400 ° C. or higher, and only high melting point metal can be used. . Further, under such conditions, the aperture diaphragm deteriorates severely and it is necessary to replace the diaphragm every three months. Furthermore, if the aperture stop itself is not grounded, the whole body is charged, and the problem of beam drift also occurs.

Therefore, in the present invention, as shown in FIGS. 1 and 2, the first forming apertures 3 and 4 are composed of two sheets, and the silver paste 55 as a conductive adhesive is fixed to the same metal jig 17 as the aperture diaphragm and the fixing jig. The entire contact surface of the tool was coated and adhered.
The first aperture 3 is made of molybdenum, and the number and position of the opening holes are made of silicon. The aperture diaphragm 4 for controlling the beam shape is used.
Is the same as. The dimension of the opening is 150 μm square for the beam shape control opening 19 made of silicon, whereas it is 200 μm square for the opening 18 made of molybdenum. The processing precision of the molybdenum opening 18 was 10 μm, and the edge roughness was 0.5 μm. The positions of the openings of the aperture diaphragm 3 and the aperture diaphragm 4 were adjusted while observing and adjusting both openings with an optical microscope when adhering. When the distance between both aperture diaphragms is set to 1 cm or less, observation can be performed at the same focal position at 100 times, so that the positional deviation of the aperture hole can be suppressed to 10 μm or less.

The electron beam drawing apparatus according to the present invention is
As shown in FIG. 1, when the preliminary exhaust chamber 51 is provided and the aperture diaphragm is replaced, the fixing jig 17 is evacuated to vacuum in the preliminary exhaust chamber, and then the opening / closing valve 52 of the housing is opened.
It is mounted on a metal holder 54 by a moving motor 53. This holder 54 is grounded through a ground wire 55. For this reason, replacement of the aperture stop is completed in a few minutes and no position adjustment between apertures is required. First, the electron beam emitted from the electron gun 1 is irradiated by the deflector 2 onto the opening of the first formed molybdenum aperture stop 3 at a desired position. The beam diameter at this time is 600 μmφ. Next, 200 μ is placed on the first molding silicon aperture 4.
A m-square beam is emitted and this aperture diaphragm makes 1
It is molded into a 50 μm square. At this time, since the beam shape is entirely formed in the opening 19 formed by the silicon aperture, the beam can be formed with good linearity. The amount of current absorbed by the silicon aperture is 200 μm square and 150 μm.
The difference in m angle is 1 μA, and the heat is dissipated by conduction through the fixing jig and the ground wire, so the temperature rise is 20.
It fell below ℃. At this time, most of the current is absorbed in the molybdenum aperture 3, but the heat generated here is also radiated by heat conduction through the fixing jig and the ground wire 56, so that the temperature rise is suppressed to a low temperature of 100 ° C. Further, the electrons scattered at the aperture edge are absorbed by the side surface of the aperture diaphragm and the fixing jig, which are conductive, so that the drift is 0.
A stable beam of 5 μm or less was realized. This good characteristic did not change for more than 6 months, and when deterioration occurred, it was possible to use it without replacing the aperture diaphragm for at least 1 year by selecting another opening in the same aperture diaphragm. When fixing the silicon aperture 4 and the molybdenum aperture 3 to the fixing jig 17, the thick film portion 43 of the silicon aperture stop is set in a lattice shape as shown in FIGS. The gradient can be relaxed, and the fixing jig surface 17 is also formed in a lattice shape to increase the contact area with the aperture diaphragm surface, thereby suppressing the temperature rise without affecting the beam shape. As for the adhesion of the aperture stop, as in the above example, the silver paste 55 was used to coat the contact surface on the grid to improve the adhesion, and as a result, the temperature rise could be reduced to about 10 ° C.

<Embodiment 2> In addition to the previous embodiment, FIG.
Regarding the second shaping aperture stop 8 as shown in FIGS. 6 and 7, similarly, a case will be described in which the aperture stop 9 for blocking an extra beam is set on the silicon aperture stop. In this case, similar to the above-described embodiments, the openings 21, 23, 25, 27, and 29 of the silicon aperture are similar to each other, and a certain amount of increment is provided in size, but the opening shape is an arbitrary figure other than a rectangle and has a minimum size. Also becomes 10 μm or less. For this reason, a silicon single crystal having good workability is used as the material of the aperture, but in order to increase the heat capacity, the thickness is set to 40 μm, which is double the usual thickness. Two silicon apertures are shown in FIGS. The aperture pattern is the cell pattern 2 of the wiring layer of the 64-megabit random access memory.
Contains 1. The minimum dimension of the wiring portion is 7.5 μm. On the other hand, the silicon apertures 9 provided above are openings 20, 22, 24, 26, 2 having similar shapes.
Although 8 is inherent, the minimum aperture size is 8.5 μm, which is set to be 1 μm larger than the desired beam size. The processing accuracy of this aperture opening is 1 μm,
The minimum processing size of the opening actually formed was 9 μm. In addition, the alignment of the upper and lower openings requires an accuracy within 1 μm. The alignment was performed using a scanning microscope or an optical microscope with a magnified image of 10 to 1000 times. The distance between the two aperture diaphragms must be set within 1 cm in order to obtain two aperture images in the visual field.

The aperture diaphragm 8 thus created,
9 makes it possible to reduce the amount of current applied to the beam shape control aperture. That is, in the conventional collective figure irradiation method apparatus, the second shaping aperture diaphragm 8 is irradiated with a beam of 125 μm square, whereas in the present invention, the current can be reduced to about 1/10 of that. For this reason, since it is possible to perform drawing with an acceleration voltage of 50 kV and a current density of 10 A / cm ² or more, the number of images drawn per hour can be 20 wafers or more for a 64-megabit random access memory.

Further, the case of applying to high precision drawing will be described. In this case, the scattered electron beam 16 at the silicon aperture 4 must be reduced as shown in FIG. In this case, the sample is irradiated with an electron beam in a region other than the original pattern, and the electron beam hits the inner wall of the electron optical mirror body to be charged, which affects the drawing accuracy. Therefore, as shown in FIG. 10, the scattered electrons 166 could be removed by providing an aperture 33 made of molybdenum under the silicon aperture 4. As the aperture 33 made of molybdenum, the same aperture as the aperture 3 made of molybdenum was used. These openings 18,1
Regarding the alignment of 9, 181, after fixing to separate fixing jigs 17, 171, 172 with a conductive adhesive, first, the openings 18, 19 are set by an optical microscope.
Finely adjust and fix 7,171. Next, the opening 181 is adjusted to these openings by finely moving the jig 172. These aperture diaphragms 3, 4, 33 are each 1c
Since the intervals are set within m, the above adjustment can be performed on the same focus of the optical microscope. After these adjustments, the scanning electron microscope was used after confirming that the openings 18, 19, 181 were aligned. When replacing the aperture diaphragm, replace the integrated fixing jig.

When replacing the aperture in the above case,
As in the case of the first embodiment, since the replacement is performed through the preliminary exhaust chamber shown in FIG. 1, the replacement time is only a few minutes and the position adjustment between the aperture diaphragms is not necessary inside the housing.

<Third Embodiment> A case where the present invention is applied to a drawing apparatus of a variable molding method will be described as an example.

FIG. 9 shows a conventional variable molding apparatus, and FIGS. 1 and 10 show a variable molding apparatus according to the present invention.

The variable molding method is based on the electron gun 1 as shown in FIG.
The electron beam 16 generated from the first rectangular aperture 4
After being shaped into a rectangle by 1, the shaped lenses 5 and 7 and the deflector 6 form an image on the second rectangular aperture 291 to form a rectangular beam of arbitrary shape on the sample 15 by the shaped lenses 12 and 14 and the deflector 13. Draw at the position.

The conventional aperture stop 41 is made of molybdenum and has a thickness of 50 μm and an opening size of 2 mm square. Similarly, the second shaping aperture stop 291 has a thickness of 50 μm and an opening size of 200 μm square. 50k for these apertures
When irradiated with an electron beam of V, 10 A / cm ² , the temperature rise is 1000 ° C. or less, which is below the melting point of molybdenum, so there is no practical problem in terms of thermal stability. However, the processing accuracy of molybdenum is about 10 μm, and the edge roughness is about 0.3 μm. Therefore, 0.3 μm
The following precision drawing is not accurate. On the other hand, if a silicon single crystal that can be processed with an accuracy of edge roughness of 0.03 μm or less is used, melting and drift due to temperature rise have become problems.

In the present invention, the first and second apertures 42, 2
92 is made of silicon, and molybdenum apertures 31 and 281 are placed on the aperture diaphragms made of silicon.
Is set and fixed to the same fixing jig. The opening dimension of the first shaping aperture is 2.1 mm square for molybdenum and 2.0 mm square for silicon. The second shaping aperture is also composed of two aperture diaphragms 281 and 292. The first aperture stop 281 is made of molybdenum and has a thickness of 50 μm and an opening size of 210 μm square. An aperture stop 292 made of silicon is set below this and is fixed to the same fixing jig. This opening size is 200m
It is m square. In any case, the distance between the pair of aperture stops is set within 1 cm. Even when these apertures are irradiated with an electron beam of 50 kV and 10 A / cm ² , the temperature rise of the aperture diaphragm made of silicon is 20.
It can be kept within ℃, and because it is grounded by the ground wire 56, there is no effect of charging during use.
It was possible to draw with an accuracy of less than μm. As described above, according to the present invention, not only convenience in use but also basic accuracy can be improved.

[0026]

According to the present invention, since the compound aperture stop can be used without any adjustment in the housing, it is possible to realize the characteristics more than the conventional one in terms of stability and accuracy in addition to high convenience. As a result, drawing with high fineness can be performed at high speed. Further, the upper limits of the accelerating voltage and the current value can be determined without depending on the material of the beam shape control aperture. Further, in the present embodiment, the electron beam is taken as an example, but the same effect can be obtained with a charged beam drawing apparatus such as an ion beam.

[Brief description of drawings]

FIG. 1 is a block diagram drawing apparatus according to the present invention.

FIG. 2 is a sectional view of an aperture stop according to the present invention.

FIG. 3 is a top view of an aperture stop according to the present invention.

FIG. 4 is a conventional collective figure drawing device.

FIG. 5 is a block diagram drawing device according to the present invention.

FIG. 6 is a sectional view of an aperture stop according to the present invention.

FIG. 7 is a top view of a second shaping aperture stop.

FIG. 8 is a variable-shape drawing apparatus according to the present invention.

FIG. 9 is a conventional variable shaping drawing device.

FIG. 10 is a top view of the aperture diaphragm of the present invention.

FIG. 11 is a sectional view of an aperture stop and a fixing jig of the present invention.

FIG. 12 is a top view of the aperture diaphragm and the fixing jig of the present invention.

[Explanation of symbols]

1 ... Electron gun, 2, 6, 10, 13, ... Deflector, 5, 7,
11, 12, 14 ... Molded lens, 3, 31, 33 ... Molybdenum aperture, 4, 41, 42 ... First molding aperture diaphragm, 43 ... Silicon aperture diaphragm thick film portion, 44
... Silicon aperture diaphragm thin film part, 51 ... Preliminary exhaust chamber,
53 ... Moving motor, 54 ... Holder, 55 ... Conductive adhesive, 56 ... Ground wire, 8, 291, 292 ... Second shaping aperture diaphragm, 9 ... Beam blocking aperture diaphragm, 15 ... Sample, 16 ... Electron beam, 166 ... Scattered electrons, 17, 17
1,172 ... Fixing jig, 18, 19, 21, 22, 2
3, 24, 25, 26, 27, 28, 29 ... Opening

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Ito, 882 Ichimo, Katsuta-shi, Ibaraki Hitachi, Ltd. Measuring Instruments Division (72) Inventor Yasunari Hayata 1-280, Higashi Koikeku, Kokubunji, Tokyo Hitachi, Ltd. Central Research Center

Claims (10)

[Claims] 1. An aperture diaphragm of a charged beam drawing apparatus for controlling the shape of a charged beam using a plurality of aperture diaphragms, wherein at least two or more aperture diaphragms are fixed and integrated in the same fixing jig at intervals. The aperture stop is characterized by 2. A method of manufacturing an aperture diaphragm, characterized in that a conductive adhesive is used to fix the aperture diaphragm to a jig in the aperture diaphragm of a charged beam drawing apparatus for controlling the shape of the charged beam. 3. The aperture diaphragm according to claim 1, wherein a conductive adhesive is used for fixing the aperture to the fixing jig. 4. The aperture diaphragm of the aperture diaphragm is made of a semiconductor material or a metal material, and the fixing jig is made of a metal material.
Item 2. An aperture diaphragm according to item 2 and a method for manufacturing the same. 5. The aperture diaphragm according to claim 1, wherein the distance between the aperture diaphragms is within 1 cm. 6. An aperture diaphragm having a plurality of apertures of arbitrary shape and an aperture diaphragm having a larger aperture size than the aperture hole size and having a similar shape and including the same number of apertures at the same position. The aperture stop according to claim 1 or 2, and a method for manufacturing the aperture stop. 7. An aperture diaphragm in which the shape of the charged beam is controlled by its aperture, wherein the aperture is formed in a thin film region and the periphery thereof is an aperture diaphragm separated by a lattice-like thick film portion. And claim 1 and claim 2
Aperture diaphragm according to the item 1 and a manufacturing method thereof. 8. The aperture diaphragm is formed in the thin film region and the periphery thereof is separated by a lattice-like thick film portion, and the aperture diaphragm is fixed to a fixing jig having the same lattice-like openings. Aperture diaphragm according to claim 1 and claim 2 and a method of manufacturing the same. 9. A charged beam drawing for irradiating a charged beam emitted from a charged beam radiation source onto a plurality of aperture diaphragms having openings and controlling the shape of the charged beams with the apertures to form a pattern on a sample. In the apparatus, at least two or more aperture diaphragms are fixedly integrated with the same fixing jig with a gap, and the fixing jig is fixed in a state of being electrically grounded, and a moving mechanism capable of moving the fixing jig in a plane is provided. A charged beam drawing apparatus characterized in that 10. The charged particle beam drawing apparatus according to claim 9, wherein the charged particle beam drawing apparatus is provided with a mechanism capable of exchanging the fixing jig together through a vacuum pre-evacuation chamber.