JP2011181339A - Electron gun and multi-column electron beam device - Google Patents

Abstract

【Task】
In order to apply an electron gun for current heating to several tens or more multi-columns, the total heat generation energy is large, and the high vacuum of the electron gun chamber cannot be maintained. The size of the electron gun power supply is large. Furthermore, since the vibration transmitted through the transmission cable is large, high-precision exposure cannot be performed. In the conventionally proposed method of heating with light, the electron gun cathode has a large surface area and a large heat conduction, so that the total energy of heating is large and the alignment of the light is not easy.
[Solution]
Light such as a semiconductor laser is incident from the end of an optical waveguide made of sapphire, and an electron gun cathode such as LaB6 is heated via a holder heated by light such as rhenium installed at the tip, An electron gun is formed that emits thermoelectrons or thermal field emission electrons into a vacuum. When this electron gun is used in a multi-column electron beam exposure apparatus, it is possible to reduce energy, increase the degree of vacuum, reduce the size and power of the high-voltage power supply circuit, and increase the accuracy of the exposure pattern.
[Selection] Figure 1

Description

  Enables the realization of a multi-column electron beam apparatus using a plurality of electron beams in the electron beam exposure technology utilized in the lithography field for exposing circuit patterns in semiconductor (LSI) manufacturing processes, The present invention relates to an electron gun having a simple structure, low power consumption, and easy mounting, and a multi-column electron beam apparatus including the electron gun.

  Conventionally, a photolithography technique (optical lithography) in which a mask to be an original drawing is prepared by an electron beam exposure apparatus and the mask image is transferred to a semiconductor substrate (wafer) by light has been mainly used as a semiconductor lithography technique. In the optical lithography technology, from the principle that resolution is improved by shortening the wavelength of light, the wavelength of light has been shortened with the progress of miniaturization, from g-line (wavelength 436 nm) to i-line (wavelength 365 nm). As a result, miniaturization, high integration, and cost reduction have been achieved. At present, excimer laser light having a wavelength of 193 nm is used. In the future, lithographic techniques using 13.4 nm ultrashort ultraviolet rays with shorter wavelengths will be energetically developed.

  An ultra-short ultraviolet exposure device (EUV) is a next-generation semiconductor lithography technology, and an experimental device with a processing capacity of about one wafer per hour has been prototyped. However, it is difficult to efficiently generate light with an ultra-short wavelength. Various issues have been reported. For example, a mask is necessary because it is a photoengraving technology, but because it is an extremely short wavelength, conventional transmission mask technology cannot be used, so a new reflective mask technology must be established quickly. There are many problems in peripheral technology, such as the need for large power that must be installed.

  On the other hand, the development cost of masks has been increasing with the progress of semiconductor miniaturization, and has reached several hundred million yen per type of LSI. An electron beam exposure apparatus has been used for mask development because of its feature of having a pattern generation function. However, the processing time has increased with the progress of optical lithography technology, such as the introduction of super-resolution technology that realizes transfer performance below the wavelength of light and the enlargement of mask data due to high integration. Ten hours have come to be taken.

  The electron beam exposure method began with a method called single-stroke writing with a finely focused electron beam, and developed an exposure method such as a variable rectangle method and a character projection (CP) method that collectively exposes several square microns using a micro mask. However, the exposure processing time of several tens of hours per mask layer and the direct exposure to a 300 mm wafer requires several tens of hours.

  Therefore, attention will be focused on maskless lithography technology, which aims to reduce the mask price explosion by shortening the mask exposure processing time, and to realize direct exposure to the wafer by the electron beam exposure apparatus without using an expensive mask. Therefore, a multi-beam type apparatus that performs exposure processing in parallel using a plurality of electron beams has been proposed, and it is expected to increase the processing capability by several tens of times.

In maskless lithography technology, an industrially useful processing capability is required to expose 10 or more 300 mm diameter wafers per hour. For this purpose, it is required to realize a multi-electron beam exposure apparatus with about 100 electron beams from the processing capability per electron beam. Therefore, in order to generate 100 (10 × 10) electron beams on a 300 mm wafer, a technique for simultaneously generating a plurality of electron beams at a pitch of 30 mm or less is required.
When electron beams are generated at a pitch of 30 mm or less at the same time, the electric fields of adjacent electron guns affect each other between the electron guns. Therefore, the size of the electron gun is preferably about 10 mm or less.

The processing capability of the electron beam exposure apparatus is proportional to the electron beam intensity and inversely proportional to the sensitivity of the dyst that is a photosensitive material. In the electron beam exposure apparatus, the beam is blurred by a large current due to the interaction between electrons, so there is a situation that the current value must be limited to about several microamperes per electron beam.
On the other hand, it is considered that an extremely fine (approximately 15 nm to approximately 10 nm line width) LSI pattern cannot achieve the intended exposure accuracy unless it is based on a resist with low sensitivity (around 100 μC / cm 2). Due to these restrictions, a 300 mm wafer having a size of about 600 square centimeters requires an exposure time of 60,000 seconds or more. With approximately 100 multi-columns, this can be reduced to approximately 600 seconds or less.

  In one of the electron beam exposure methods, CP (character projection) that collectively exposes an area of several square microns, an average fill rate can be described with a pattern of approximately 20% or less, and in terms of conversion, exposure can be performed in approximately 120 seconds or less. there is a possibility. This corresponds to a processing capacity of 20 sheets per hour.

  There are two main methods for generating a plurality of electron beams. One method uses only one electron gun, and the split shaping type in which electrons emitted from the electron gun are made into a plurality of electron beams through a structure called a splitter having many holes, and the other method is as follows: This is a multi-electron gun type having an electron gun for each electron beam to be exposed.

  In the split shaping type, since the spacing between the splitters is in micrometer units, it is difficult to control the uniformity of the intensity of the electron beam entering each hole, adjust the axis for each split electron beam, and determine the deflection position. An exposure system is used in which an electron lens optical column (column) is used for an electron beam, and only ON / OFF is individually controlled to obtain an exposure pattern. However, it is difficult to adjust the intensity of each divided beam with the accuracy required for exposure, and there is a disadvantage that exposure cannot be performed with high accuracy.

  Also, one electron beam has the same negative charge, and when the total amount of electrons is large, the electrons repel each other due to Coulomb repulsion, resulting in significant beam blur. There is an electron beam intensity limit. The multi-electron beam technology is attracting attention as a technology that overcomes the intensity limit per electron beam.

  On the other hand, in the multi-electron gun type, the size of one electron gun is in centimeters, and since it has an independent column for each electron beam, it is called a multi-column system and is a column element that is a single electron optical element It has a structure in which dozens are bundled.

  With this method, parameters that affect exposure accuracy such as beam intensity, radiation angle, and current density can be individually controlled, making it easy to obtain exposure accuracy. Since there are multiple independent columns, the electron beam against beam blur caused by Coulomb repulsion Although the electron beam intensity limit is not changed, the total amount of light is not changed, but by using a multi-electron gun type, exposure can be performed using an electron beam of several tens of microamperes or more as a whole, so the processing capability can be dramatically improved. This makes it possible to perform exposure processing on several tens of wafers per hour, which is beneficial for industrial use.

  Conventionally, in an electron beam exposure apparatus, a method for holding an electron gun cathode and a heating method, called a Vogel mount type, shown in Non-Patent Document 1 have been used. This electron gun has a structure in which an electron gun cathode serving as an electron generating source is sandwiched from both sides by PG (pyrogetic) graphite serving as a heating element and further pressed and held by metal springs from both sides. The heat generation state of PG graphite is controlled by the current passed through PG graphite, and thermionic emission conditions are obtained.

  Patent Document 1 and Patent Document 2 disclose a technique in which a laser beam is irradiated in a non-contact manner from the front side or the back side of the tip portion of the electron gun cathode material, efficiently heated, and many electron beams are extracted.

Electron / Ion Beam Handbook 3rd Edition, Japan Society for the Promotion of Science 132nd Committee Editor-in-Chief Chairman Katsumi Ura Nikkan Kogyo Shimbun October 28, 1998 P119 Figure 4.3 Method of Holding Compound Cathode

Japanese Patent Publication No. Hei 8-212952 Japanese Patent Publication No. 6-181029

  In order to realize a multi-electron beam exposure apparatus by simultaneously generating a large number (approximately 100) of electron beams on a 300 mm wafer, the electron gun for generating electron beams has the following problems.

  In the Vogel mount type electron gun technology that uses a current of the Vogel mount type shown in Non-Patent Document 1, not only the surface area of the electron gun heat generating part is large and the power lost by radiant heat is large, but also the heat conduction through PG graphite is large. Since the heating energy of the entire electron gun becomes large, the cooling mechanism of the electron gun and the electron gun container becomes complicated, and it becomes difficult to maintain a high vacuum that is essential for stable operation of the electron gun.

  In addition, the electron beam acceleration control power supply including the heating power supply becomes enormous, making it difficult to mount a large number of units, and the cables connecting the power supply and the electron gun also become enormous, so the mechanical vibrations of peripheral devices are transmitted to the column. There is a problem that the electron beam is shaken and pattern formation cannot be performed with high accuracy.

In the method disclosed in Patent Literature 1 and Patent Literature 2 in which the tip portion of the electron gun cathode by laser light is irradiated in a non-contact manner from the front surface side or the back surface side, the method for holding the electron gun cathode itself is conductive heat or Since there is no proposal to reduce the radiant heat, when applied to approximately 100 multi-column electron beam exposure apparatuses, there is a problem that causes an increase in heating energy due to a loss due to radiant heat and heat conduction from the heat generation part of the electron gun. .
In addition, since the irradiation of light is non-contact, it is difficult to ensure the accuracy of optical axis alignment, and there is a problem that it is difficult to construct an electron gun with a small diameter in which approximately 100 are aligned.

  Accordingly, an object of the present invention is to provide an electron gun cathode and its heating source in a heated field emission type or thermionic emission type electron gun, in which the electron emission control part and the emission part are small and the vibrations of the surroundings are not easily transmitted to the column. Is to realize an electron gun having a minimum surface area.

  Therefore, a laser beam suitable for local heating and having a propagation means with low loss is used as the heating means, and the light source to the electron gun is guided by an optical fiber, and the electron gun cathode in vacuum is provided with an electron supply function, etc. A heat-resistant solid material optical waveguide, which protects the chemical reaction between the optical waveguide and the electron gun cathode, supports the electron gun cathode through a holder that absorbs the light and forms a heating element, An electron gun having an electron generation mechanism is used.

By using a laser beam having a high energy density, the above-mentioned light can heat only a finer region of the electron gun, and can minimize the surface area of the heat generating portion of the electron gun. This makes it possible to realize a small and lightweight electron gun cathode with minimal loss due to heat radiation and conduction. Also, changing the electron gun cathode heating means from conventional current to light can reduce the high voltage signal of the control power supply of the electron gun, and can suppress the increase in the number of cable cores and the enlargement of the circuit operating at high potential. .
This solves the above-described problem.

  As described above, according to the electron gun of the present invention, the electron gun cathode, the heating energy of the electron gun cathode, the high temperature portion of the electron gun, and the power source for accelerating and controlling the electron beam can be minimized. An electron gun suitable for a multi-electron beam exposure apparatus can be realized that suppresses an increase in the number of cores of the connection cable to the control power source, makes it difficult to provide a mechanical vibration to the column, and is easy to align.

It is a figure explaining the 1st Example of the electron gun of this invention. It is a figure which shows another Example of this invention, and shows an optical waveguide, a holder, and an electron gun cathode. It is a figure which shows the holding method of the conventional Vogel mount type electron gun cathode. It is a block diagram of a conventional Vogel mount type electron gun and its control power supply. It is a block diagram of the electron gun of the photoheating of this invention, and its control power supply. 1 is a diagram of a multi-column electron beam exposure apparatus using the present invention.

  Embodiments for carrying out the present invention will be described with reference to the drawings.

  In FIG. 1, an optical waveguide 102, a holder 103, and an electron gun cathode 104 are a first embodiment of an electron gun cathode portion of the present invention, and a suppressor electrode 105, an extraction electrode 106, an electron gun anode 107, an insulating base. 109 and others constitute an electron gun.

The light 100 is light having a high energy density, is incident from one end portion (terminal portion) of the optical waveguide 102, and is provided with a holder 103 and an electron gun cathode installed at opposite ends (tip portions) of the optical waveguide 102. By heating 104 to a high temperature and adjusting the light intensity, conditions for injecting electrons into the vacuum are obtained.
Here, the light 100 is, for example, light emitted from a semiconductor laser. Visible light is suitable for aligning the optical axis, but it is also possible to use ultraviolet rays to infrared rays.

The optical waveguide 102 is a propagation path of the light 100 and is also a support that mechanically supports the holder 103 and the electron gun cathode 104, and the electron gun cathode 104 is at a high temperature (approximately 1500 ° C.) at which electron emission conditions are obtained. It has the heat resistance to withstand and the function of the electron supply path to the electron gun cathode 104.
The function of the propagation path is to propagate the light incident from the end portion without being dissipated to the opposite end surface by totally reflecting the light from the side surface and guiding it forward.
The electron supply path of the optical waveguide is a function necessary for supplying electrons emitted into the vacuum through the holder 103 and the electron gun cathode 104.

Suitable materials for the optical waveguide 102 include sapphire, ruby, diamond, and quartz glass that transmit light and have a high melting point. Since these materials have high insulating properties, conductivity is added to provide an electron supply path for supplying electrons emitted from the electron gun cathode. For example, a metal thin film 101 having a thickness of about several hundred nm is deposited by vapor deposition or sputtering of a rhenium thin film. Alternatively, using an ion implantation technique on the surface layer of the optical waveguide, one kind of bromine, nitrogen, oxygen, fluorine selected from bromine, nitrogen, oxygen, fluorine, aluminum, phosphorus, sulfur, chlorine, gallium, arsenic, Conductivity may be imparted by irradiation with ions selected from aluminum, phosphorus, sulfur, chlorine, gallium, and arsenic.
Further, even if the optical waveguide 102 itself is an insulator, electrons may be supplied to the electron gun cathode 104 by another conducting wire. For this purpose, an electron supply terminal is provided on the electron gun cathode, and emitted electrons from the electron gun cathode are supplied from an electron gun power source by a thin electric wire.
In the following description, sapphire is selected as the material of the optical waveguide from the materials of sapphire, ruby, diamond, and quartz glass as the optical waveguide according to the transparency, heat resistance, and workability of the light.

  The shape of the optical waveguide 102 is preferably a cylindrical shape having a diameter that can be easily incident from an optical fiber propagating from the light source of the light 100 to the optical waveguide 102, or a tapered cone that becomes narrower toward the tip. Further, the structure may be such that the material and shape are changed, light is reflected by the inner surface of a hollow metal tube, and the light is propagated to the tip.

The holder 103 is a heating element that receives and absorbs light 100 and is also a structure that supports the electron gun cathode 104. It consists of a substance that can provide a protective function that does not chemically react with LaB6 or CeB6, which is an electron gun cathode material, at an operating temperature (approximately 1500 ° C.) as an electron gun. As the holder, one material selected from rhenium, tantalum and carbon is used. In the following description, rhenium having good workability and heat resistance is mainly used.
The reason why the chemical reaction protection function is necessary is that electron gun cathode materials such as LaB6 and CeB6 can be easily combined with many substances excluding some substances such as rhenium, tantalum and graphite (carbon) at the operating temperature as an electron gun. This is due to the need to prevent chemical loss and alteration of the electron gun characteristics.

  The shape of the holder 103 is a cylinder having a diameter larger than that of the optical waveguide 102 and the electron gun cathode 104, and holes for inserting and fitting the optical waveguide 102 and the electron gun cathode 104 are processed at both ends. Therefore, the cross section is in the shape of the letter “H”. The length of the letter H in the vertical direction is set to several hundred μm or less. After the fitting, it is locally melted with a melting laser and poured into the groove 111 formed in the optical waveguide 102 and fixed. The main groove 111 is not necessarily required as long as the cylinder of the holder 103 can be fixed to the tip of the column of the optical waveguide 102. The upper part of the holder 103 is dissolved and fixed so as to confine a single crystal such as LaB6 or CeB6.

The electron gun cathode 104 is used by selecting one material from 6-boronated lanthanoid compounds such as LaB6 or CeB6, which are materials that emit thermoelectrons or thermal field emission electrons at a high temperature. The lanthanoid is a generic name of 15 elements from the third (3A) group of the 6th period of the periodic table, up to 71th ruthenium Lu having similar chemical properties as typified by the lanthanum La of atomic number 57.
The electron gun characteristics are preferably single crystals. The operating temperature of the electron gun cathode is high (approximately 1500 ° C.) means that the work function of LaB6 or CeB6 is 2.6 eV, and the temperature is such that thermionic emission is possible.

  There are also low-temperature or room-temperature field emission electron guns that do not raise the temperature by applying a strong electric field with a sharp tip, but the operation of the electron gun is not possible due to adsorption of water molecules and carbon atoms at the electron gun cathode. Since the electron beam is stable and the electron beam is not stable, an electron gun such as an electron beam exposure apparatus needs to be heated at a high temperature.

  The electron gun cathode 104 has a cylindrical shape with a convex cross section, and has a cylindrical shape with a bottom portion of several hundred μm (approximately 500 μm) and a tip portion of approximately 100 μm.

  The suppressor electrode 105 suppresses electron emission from the side surface of the optical waveguide 102 at zero potential with respect to the electron gun cathode 104.

    The extraction electrode 106 is applied with a potential of about +3 kV to about +5 kV with respect to the electron gun cathode 104, and is applied to the vicinity of the upper surface of the tip of the 100 μm diameter cylinder of the electron gun cathode 104 so that the thermal field emission electrons are emitted from the electron gun anode. It is injected toward 107.

  The electron gun anode 107 is normally at a ground potential (0 V), and a voltage for accelerating an electron beam of minus several tens of kV (eg, minus 50 kV) is applied to the electron gun cathode 104 to give a kinetic energy of several tens of keV (eg, 50 keV). An electron beam 108 is obtained by applying the thermal field emission electrons. As a result, the electron gun cathode 104 has a potential of approximately minus 50 kV, and the extraction electrode 106 has a potential of approximately minus 47 kV to approximately minus 45 kV. Thereby, the whole structure of FIG. 1 functions as an electron gun.

The insulating base 109 is an alumina ceramic disk, and the optical waveguide 102 is fixed to the center of the disk. The insulating base 109 can insulate the suppressor electrode 105 and the optical waveguide 102, but normally, the suppressor electrode 105 may have the same potential as the optical waveguide 102.
The insulating base 110 insulates the extraction electrode 106 and the optical waveguide 102.

  The conductive ring 112 is at the end of the optical waveguide 102, and an electron beam acceleration voltage is connected to the conductive ring 112 to supply electrons emitted through the metal film 101, the holder 103, and the electron gun cathode 104 of the optical waveguide 102.

  FIGS. 2A to 2J show another embodiment of the structure and holding method of the electron gun cathode portion in the electron gun of the present invention.

In FIG. 2A, a holder 103a is fitted into a hole 102a having a hole at the tip of the optical waveguide 102. A two-stage cylindrical electron gun cathode 104a made of a single crystal of LaB6 or CeB6 and having a lower diameter of 500 μm and an upper part of 100 μm is inserted into the lower part of the holder 103a with a hole in the lower cylinder. Yes.
In FIG. 2 (b), the holder 103a is fitted with a flange 103b so that rhenium and LaB6 or CeB6 are not in direct contact with each other.

  The grooves 113 of the holders 103a and 103b are formed for the convenience of manufacturing in order to fix the optical waveguide 102a and the electron gun cathode 104a to the holder. After the holder 103 is engaged with the optical waveguide 102 and the electron gun cathode 104, a welding laser is irradiated from the outside of the optical waveguide 102 and the electron gun cathode 104 to the position where the groove 113 is located, and the material is melted into the groove 113. It is what is joined.

  In FIG. 2 (c), the upper part of the holder 103c is a cylinder having a diameter of 500 .mu.m, a hole having a diameter of about 100 .mu.m is formed in the center of the tip, and a 100 .mu.m diameter LaB6 or CeB6 single crystal electron gun is formed in this hole. The column of the cathode 104c is fitted.

In FIG. 2 (d), the upper part of the holder 103d is a 300 μm diameter cylinder, and a hole with a diameter of about 100 μm is formed in the center of the tip part, and this part is split to have a spring property. A 100 μm-diameter LaB6 single crystal cylinder is fitted into this hole.
In the embodiment in this section, the length is approximately 500 μm with respect to the 100 μm diameter of the upper portion of the LaB6 single crystal of the electron gun cathode 104c. Since the radiation area is sufficiently smaller than the area of the high temperature portion of the rhenium material of the holder 103d, it does not depart from the gist of the invention.

  In FIG. 2 (e), the holder 103e is a thin film, and the holding function is carried by the holder 103e made of a rhenium thin film attached to the inner surface of a hole formed at the tip of the optical waveguide 102a. An electron gun cathode 104e is fitted to the optical waveguide 102a. The rhenium thin film may be formed on the electron gun cathode 104e side.

  In FIG. 2 (f), the holder 103f is a thin film, and the holding function is carried by the holder 103f made of a rhenium thin film attached to the inner surface of a hole formed at the tip of the optical waveguide 102a. A hole is formed in the lower portion of the electron gun cathode 104f of the optical waveguide 102a. The rhenium thin film may be formed on the electron gun cathode 104f side.

In FIG. 2G, the holder 103g is solid rhenium, and is fitted into the hole on the tip surface of the optical waveguide 102a. Further, there is a hole in the tip surface of the holder 103g, and the electron gun cathode 104c is fitted into this hole.
FIG. 2H shows an embodiment in which the tip of the electron gun cathode 104h has a conical shape.

In FIG. 2 (i), a rhenium thin film is attached to an electron gun cathode 104i composed of a single crystal of LaB6 or CeB6, which is a combination of a cylinder and a cone, the tip of the cone portion is cut, and a single crystal of LaB6 or CeB6 is integrated. The part is exposed and fitted to the holder 103.
FIG. 2 (j) shows an embodiment in which a fusion fixing groove 114 is formed in the electron gun cathode 104i.

  A prior art Vogel mount type electron gun cathode part is shown in FIG. 3, and a holding method and a heating method will be described below.

The conventional general electron gun cathode introduced in Non-Patent Document 1 is an electron made of a single crystal of LaB6 or CeB6 having conductivity and a work function for generating electrons in the vicinity of 2.6 eV. The gun cathode 201 is sandwiched between two PG graphites 202a and 202b cut along a plane perpendicular to the C-axis direction. This is pressed by metal supports 203a and 203b, and the springs 204a and 204b are tightened from the supports 205a and 205b by screws 206a and 206b.
Rotate to adjust the protrusion amount. The ends of the screw support bases 205a and 205b are fixed to an insulating base 207 made of alumina ceramic, and 205a and 205b are electrically insulated from each other. The leg portions of the screw support bases 205a and 205b are in electrical contact with the current introduction terminals 208a and 208b, and the PG graphites 202a and 202b are heated by flowing a current of several amperes, whereby a single crystal chip of LaB6 or CeB6. The electron gun cathode 201 is kept at a high temperature around 1500 ° C. and operated as a thermionic gun cathode or a thermal field emission cathode.

  The PG graphite has anisotropy, functions as a resistor in the direction called the C axis, generates heat when current flows in this direction, and has low thermal conductivity. On the other hand, in the direction perpendicular to the C axis, there is a property as a metal, current heating is impossible, and thermal conductivity is large. Therefore, two pieces of PG graphite cut as C-axis crystals are used, and an electron gun cathode material such as LaB6 or CeB6 (each of which exhibits metallic properties) is sandwiched from both sides to heat and heat. The electron gun cathode material is held by utilizing the low conductivity so that the portion heated to the operating temperature (approximately 1500 ° C.) as the electron gun is made as small as possible.

  The reason for using graphite for heating is that the electron gun cathode material such as LaB6 or CeB6 is easily operated with almost all materials except for some materials such as rhenium, tantalum, graphite (carbon) at the operating temperature as an electron gun. By reacting and changing quality, the electron gun characteristics are lost.

  FIG. 4 is a configuration diagram of an electron gun control power source including a conventional Vogel mount type electron gun, an electron beam acceleration power source 403 for controlling the electron gun, a drawing electric field power source 402, and a current heating power source 401. .

  The electron beam accelerating power source 403 is a high voltage generating unit that supplies a high voltage of minus several tens kV (for example, approximately −50 kV) to the electron gun cathode, and is connected to the suppressor electrode 105 and two resistors having the same value. Are connected to the current introduction terminals 208a and 208b. The reason for connecting through the resistor is to make the potential of the electron gun cathode substantially coincide with the output of the electron beam acceleration power source 403.

  The extraction electric field power supply 402 is a unit that generates a voltage for extracting electrons from the electron gun cathode 201, and generates a voltage of plus several kV (for example, approximately +3 kV to approximately +5 kV) at the potential of the electron gun cathode. Apply to.

  The current heating power source 401 is a unit that generates a current to be passed through the PG graphites 202a and 202b for heating the electron gun cathode 201, and operates at a high voltage potential generated by the electron beam acceleration power source 403. The heating current is transmitted through the high-voltage power cable to heat the PG graphite 202a and 202b. This heat heats the LaB6 or CeB6 single crystal chip and raises the temperature to 1500 ° C., which functions as an electron gun cathode.

  FIG. 5 is a configuration diagram of an electron gun using the photoheating electron gun cathode of the present invention and a control power source of the electron gun.

  The electron beam accelerating power source 403 is a high voltage generating unit that supplies a high voltage of minus several tens kV (for example, approximately −50 kV) to the electron gun cathode, and is a conductive material on the optical waveguide 102 that supports the electron gun cathode 104. Applied through ring 112. This voltage is finally applied to the electron gun cathode 104 of LaB6 or CeB6 single crystal through the metal thin film 101.

  The extraction electric field power source 402 generates a voltage of plus several kV (approximately +3 kV to +5 kV) with respect to the electron beam acceleration power source 403 and applies it to the extraction electrode 106.

  The light source unit 504 is a unit that generates light 100 and adjusts the intensity of light by the semiconductor laser and its control unit.

  The optical fiber 505 is a transport path for the light 100 from the light source unit 504 to the optical waveguide 102. The thickness of one optical fiber is about 250 microns, and even if a plurality of dozens or more are bundled, 2. The thickness is about 5 mm in diameter. An optical fiber is an insulator such as glass, and unlike an electric wire, it does not require any special electrical insulation. Therefore, it can be introduced into a high-voltage electron gun of minus tens of kV (for example, approximately -50 kV) as it is. Suppresses the enlarging of high-voltage cables that serve as the propagation path of vibrations. Therefore, it is possible to significantly reduce the factors that deteriorate the required accuracy of exposure patterns that are increasingly miniaturized.

  The energy of the light 100 input to the electron gun causes the holder 103 and the electron gun cathode 104 to have a high temperature around 1500 ° C., and radiates heat as radiant heat of these members and conduction heat through the optical waveguide 104. Therefore, the intensity of the light 100 is adjusted so that the temperature of the electron gun cathode 104 becomes a constant value at 1500 ° C. In practice, it is difficult to detect the temperature of individual electron guns with multi-columns of several tens or more, so that they are extracted as thermal field emission electron currents by the extraction electrode 106, accelerated by the electron gun anode 107, and accelerated by the wafer 303. The intensity of the electron beam flowing into the light source is measured, and the light source unit 504 is controlled so as to keep the measured value constant. Secondarily, since the light amount monitor is included in the semiconductor laser, the output of the semiconductor laser is controlled so as to keep it constant.

  As described above, the thermal electric field emission electron gun has been described. However, there is an apparatus for controlling current emission by applying a minus number kV to minus several hundreds V as viewed from the potential of the electron gun cathode to the electrode to which the extraction electric field is applied. It is a thermionic emission electron gun. In this case, the extraction electrode 106 is not called an extraction electrode but a grid. An electron gun using thermionic emission is also the same as the thermal field emission electron gun, and the heating method is exactly the same, so the explanation is omitted.

  In the electron gun having the electron generation mechanism in which the optical waveguide 102, the holder 103, and the electron gun cathode 104 are connected in series, the radiation heat when the electron gun cathode 104 is at a high temperature (approximately 1500 ° C.), and the optical waveguide 102 The conduction heat conducted through is shown below.

  Radiant heat energy radiated from the high temperature part is proportional to the fourth power of the temperature and the area of the high temperature part. Therefore, if the area of the high temperature part of the electron gun cathode 104 and the holder 103 is reduced, it can be reduced. Since the supporting method is simple in the present invention, the area of the high-temperature part is reduced to a fraction of that of the conventional electron gun by setting the area of the electron gun cathode 104 and the holder 103 to about several hundred square μm. The radiant heat can be reduced from a fraction to a few tens of one.

Conducted heat is proportional to thermal conductivity and cross-sectional area, and inversely proportional to length. Although the thermal conductivity of sapphire is larger than that of quartz glass, sapphire is desirable for the material of the optical waveguide 102 of the present invention because of its excellent heat resistance of 2200 ° C. Quartz glass is suitable for optical waveguides in terms of thermal conductivity, but has a softening temperature as low as 1200 ° C., so it is useful for applications in which the electron gun cathode temperature is lowered.
The optical waveguide 102 is a cylinder or a cone having a cross-sectional diameter of several hundred μm or less, and the length is set to several mm, so that the cross-sectional area can be reduced and the length can be increased. As a result, the electron gun of the present invention can reduce the heat of conduction from a fraction to a fraction of a tens compared to a conventional electron gun.

  In the first embodiment of FIG. 1, the optical waveguide 102 is specifically a sapphire cylindrical object having a diameter of about 500 μm and has a length of about 10 mm. When the diameter of the holder 103 is about 600 μm or less and the length is about 500 μm or less, when the electron gun cathode 104 is about 1500 ° C. and the portion held by the insulating base 109 is about 500 ° C., The amount of heat transferred by conduction is several hundred mW or less, and the amount of heat radiated by thermal radiation is several hundred mW or less.

  The heating energy with which the electron gun obtains the electron emission condition is the sum of the radiation heat and conduction heat of the electron gun cathode 104 described above. In the present invention, the heating energy of one electron gun is about 1 W or less, and it is a fraction of the conventional number W. Therefore, the temperature of the electron gun chamber of a multi-column electron beam exposure apparatus equipped with several tens of electron guns can be kept low (approximately 100 ° C. or lower), and the degree of vacuum is 10 minus 7th power Pascal or higher. Can be maintained.

When the Vogel mount type electron gun control power source shown in FIG. 4 is applied to several tens or more multi-column exposure apparatuses, the electron beam acceleration power source 403 is common to the multi-columns, and only one power source is required. The power supply 402 and the current heating power supply 401 are required by the number of electron guns.
Since the current flowing through the extraction electrode 106 does not exceed 1 mA (milliampere) at the maximum, even if there are several tens of extraction electric field power supplies, it does not become a heavy burden, but the current heating power supply 401 is several per electron gun. It is necessary to generate a large current of several tens of amperes to several hundreds of amperes at a potential of minus several tens of kV and transmit it to the electron gun, resulting in the following problems.

  First, the electron gun heating energy increases according to the number of electron guns, and the circuit configuration of the high-voltage part becomes large, so that the size of the power source becomes huge by securing a space for protecting the discharge. .

Secondly, a cable that transmits a heating current of several amperes and a high voltage control signal for each electron gun requires four or five times the number of cores of the electron gun, and the high voltage cable has a huge diameter.
In particular, a current path for carrying several amperes requires a wire with a diameter of several millimeters from the viewpoint of suppressing DC loss, and makes the cable diameter larger. The mechanical vibration of the surrounding environment is transmitted to the column section via this cable and deteriorates the exposure accuracy because the fact that the exposure accuracy of the single electron beam exposure system is deteriorated is various vibrations. Imagine.

Third, the electron gun cathode structure is complicated from the structure shown and described in FIG. 3, the electron emission position of the electron gun cathode 201 is changed by the tightening of the screws 206a and 206b, and the center axis alignment of the trajectory of the electron beam 108 is adjusted. Therefore, it is difficult to manufacture with a diameter of 20 mm or less. Even if it is possible, it is difficult to produce a large number of electron gun cathodes with fine diameters while keeping the axis alignment with high accuracy.
Further, when the mounting interval of the electron gun is 20 mm or less, the magnetic field generated by the heating current of one electron gun affects the trajectory of electrons emitted from the electron gun itself or the cathode of the adjacent electron gun, and the beam position is changed. It becomes a factor which causes axis deviation.

When applied to a multi-column exposure apparatus, the electron gun of the present invention has the following features that overcome the problems of the Vogel mount type.
First, it is not necessary to mount a large number of heating current sources in the high voltage power source of the electron gun, and the scale and power capacity of the electron gun power source can be reduced to less than half.
Second, an increase in the diameter of the high-voltage signal transmission cable is suppressed, an increase in the propagation path of the ambient vibration is suppressed, and the deterioration factor of the exposure accuracy is reduced.
Thirdly, since the support structure of the electron gun cathode can be simplified, it is easy to manufacture, can achieve a significant downsizing, and is excellent in the intended position setting from the tip of the electron gun.
From the above, since the power source and the electron gun body can be reduced to about a fraction of the conventional ones, a small electron gun that is optimal for the multi-column system having several tens or more can be configured.

FIG. 6 shows an outline of a multi-column electron beam exposure apparatus using the electron gun of the present invention.
In the multi-column electron beam exposure apparatus, a plurality of single column elements 301 having a thickness of about 15 mm to about 70 mm, for example, are arranged two-dimensionally in a number of several tens or more (for example, 30 to 250 or more), A multi-column group 302 that irradiates a plurality of electron beams 108 onto one wafer 303 is configured. Therefore, high-speed exposure processing can be performed.

The single column element 301 is composed of the following parts.
The electron beam emitted from the electron gun 304 is shaped into a rectangle by the first rectangular aperture 305 and imaged on the second rectangular aperture or CP mask 308 by the lens / deflection optical system 306 in the previous stage. The position of the electron beam on the second rectangular aperture or CP mask 308 is reshaped into a beam of the intended size or shape by a beam deflector. Further, the lens / deflection optical system 309 in the subsequent stage deflects the light to an appropriate position on the wafer 303 and forms an image. When further disassembled, the lens / deflection optical systems 306 and 309 are configured by a magnetic lens 307.

  As described above, the electron gun technique of the present invention overcomes various problems and is indispensable for the realization of a multi-column electron beam exposure apparatus. The multi-column electron beam exposure apparatus is the core of next-generation microlithography technology. It is considered that the technology that contributes to the electronics industry is significant.

The multi-column electron beam exposure apparatus based on the electron gun technology of the present invention has an LSI pattern with a line width of 15 nm to 10 nm, which is required for the next generation semiconductor lithography technology, from approximately 10 to approximately 20 per hour on a 300 mm wafer. It is an exposure apparatus that has a high possibility as a technique capable of performing exposure with a processing capacity of one or more sheets.
The multi-column structure realized by the electron gun of the present invention can also be applied to an electron beam inspection apparatus that inspects a semiconductor substrate.
Furthermore, the electron gun technology of the present invention can be applied to all uses using an electron beam, and is not limited to a multi-column structure.

100 Light: Heats the electron gun cathode.
101 Metal thin film 102 Optical waveguide
103 Holder 104 Electron Gun Cathode 105 Suppressor Electrode 106 Extraction Electrode 107 Electron Gun Anode 108 Electron Beam 109 Insulating Base 110 Insulating Base 111 Groove 112 Conducting Ring 113 Groove 114 Groove 201 Electron Gun Cathode 202a, 202b PG Graphite 203a, 203b Support 204a 204b Spring 205a, 205b Screw support 206a, 206b Adjustment screw 207 Insulation base 208a, 208b Current introduction terminal 301 Single column element 302 Multi-column group 303 Wafer

Claims (16)

In an electron gun using light as a means for heating an electron gun cathode in a vacuum of a heating type field emission electron gun or a thermionic emission electron gun, the light is incident from one end and is unidirectional without being dissipated. A high melting point optical waveguide propagating to
A holder coupled to the optical waveguide, held at the other end by the optical waveguide, and heated by the light;
An electron gun cathode that is held by the holder and heated through the holder,
An electron gun characterized in that the optical waveguide, the holder, and the electron gun cathode are arranged close to each other in a linear order.   2. The electron gun according to claim 1, wherein the optical waveguide is provided with electric conductivity.   2. The electron gun according to claim 1, wherein an electron supply terminal is provided on the cathode of the electron gun.   3. The electron gun according to claim 2, wherein a metal thin film is attached to the surface of a cylindrical optical medium.   2. The electron gun according to claim 1, wherein the optical waveguide is formed on a surface of a conical optical medium having a tapered shape that narrows toward the holder for the purpose of collecting the light toward the holder. 3. An electron gun having a metal thin film attached thereto.   2. The electron gun according to claim 1, wherein the optical waveguide is formed of one material selected from sapphire, ruby, diamond, and quartz glass having a high melting point. An electron gun characterized in that a metal thin film is attached to the surface.   The optical waveguide according to claim 2, wherein the surface layer of the material includes ions that add electrical conductivity selected from bromine, nitrogen, oxygen, fluorine, aluminum, phosphorus, sulfur, chlorine, gallium, and arsenic. An electron gun characterized by being irradiated.   3. The electron gun according to claim 2, wherein the optical waveguide has a hollow cylinder made of a metal thin film plate or a part of a tapered cone.   2. The electron gun according to claim 1, wherein the electron gun cathode is made of a material selected from one of hexaboronated lanthanoid compounds containing LaB6 or CeB6.   10. An electron gun according to claim 9, wherein the electron gun cathode is a single crystal of a hexaboronated lanthanoid compound.   2. The electron gun according to claim 1, wherein the holder heated by light is a substance that does not chemically react with a hexaborated lanthanoid compound containing LaB6 or CeB6 at a high temperature that is an operating temperature as an electron gun cathode. An electron gun comprising a material selected from one of rhenium, tantalum, and carbon.   2. The electron gun according to claim 1, wherein the holder heated by light has a thin film made of a material selected from rhenium, tantalum, and carbon attached to a tip surface of the optical waveguide. Features an electron gun.   2. The electron gun according to claim 1, wherein the holder heated by light includes a thin film made of a material selected from rhenium, tantalum, and carbon in a hole on a tip surface of the optical waveguide. An electron gun characterized by being attached.   13. The holder heated by light according to claim 12, wherein a thin film made of a material selected from rhenium, tantalum, and carbon is attached to the bottom surface of the electron gun cathode. Electron gun.   2. The electron gun according to claim 1, wherein the light irradiated from one end of the optical waveguide is light emitted from a semiconductor laser, and is incident on the optical waveguide using an optical fiber. Electron gun. A multi-column electron beam apparatus for performing exposure or inspection of a semiconductor circuit pattern using an electron beam, wherein a plurality of electron guns according to any one of claims 1 to 15 are mounted.

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