JP2005352302A - Electron beam irradiating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an inexpensive feeding mechanism and a rotating mechanism (gas bearing) in vacuum with high accuracy in a simple configuration, to eliminate limitation for minimizing a work distance and to obtain high resolution. <P>SOLUTION: In an electron beam irradiating apparatus, a sliding mechanism has a static pressure floating function to allow a sliding shaft 3 to float by feeding compressed air to a gas bearing part 2 and a differential evacuating function in a plurality of stages to evacuate the compressed air for floating so as to stepwisely increase the vacuum degree. A spindle mechanism mounts an air spindle 4 controlling the rotating mechanism on the slide shaft 3 in a vacuum chamber 1, and has a static pressure floating function to allow an air spindle 4 to float by feeding compressed air to the gas bearing part and a differential evacuating function in a plurality of stages to evacuate the compressed air for floating so as to stepwisely increase the vacuum degree. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electron beam irradiation apparatus that irradiates an electron beam column onto an object to be rotated, for example.

  In general, a sliding (surface contact) or rolling (line or point contact) guide member is used for a feed mechanism or a rotation mechanism used in a mechanical device. Since these guide members are structurally subject to friction due to contact, it has been very difficult to perform sub-micron positioning, constant feed or rotation at an extremely low speed. The power loss due to this friction has led to a malfunction due to, for example, heat generation and the associated bearing temperature rise.

  Therefore, a gas bearing without friction has been conventionally used in a semiconductor drawing apparatus (a so-called stepper apparatus or the like) and a disk exposure apparatus. A gas bearing is a type of sliding bearing that uses gas as a lubricant. The principle of operation is the same as that of a general sliding bearing using oil. There is a gas film between the shaft and the bearing. The shaft is supported by the gas film and does not directly contact the bearing. For this reason, it has a feature of low friction (≈0), has a very good controllability, and has been adopted in an apparatus that requires high-accuracy positioning.

  For example, a master exposure apparatus that holds the key to increasing the capacity of a read-only optical disc has responded to the demand for miniaturization by shortening the wavelength of the exposure light source. Ar ion gas laser (wavelength: 458 nm) for CD (compact disc) with a capacity of 640 MB, and then krypton ion laser (wavelength: 351 nm) for a DVD (digital versatile disc) with a capacity of 4.7 GB. The latest Blu-Ray A semiconductor laser (wavelength: 266 nm) or the like is used for the disk (capacity: about 25 GB). These lasers can be irradiated in the atmosphere (inert gas). On the other hand, the exposure apparatus needs to form a spiral groove (pattern) on the disk master, and has a rotation mechanism and a uniaxial feed mechanism. A gas bearing capable of high-precision positioning is used for these feed mechanism and rotation mechanism.

  By the way, as an exposure apparatus that realizes a resolution of 100 nm or less that will be required in the future, a method using an electron beam (EB) as an exposure light source is prominent. However, it is difficult to apply gas bearings as they are in the vacuum atmosphere required for EB irradiation. Conventionally, rolling bearings such as LM (liner mortar) guides have to be used, and submicron high accuracy is achieved. It was difficult to secure.

As a means for solving this problem, the applicant of the present invention has proposed that a static vacuum levitation pad is used in a partial vacuum electron beam irradiation apparatus using a differential static pressure levitation pad such as an “electron beam irradiation apparatus” (see Patent Document 1). By sucking positive pressure into the pressure bearing part and sucking the exhaust vacuum part with negative pressure, the master (wafer) and the pad part are adsorbed in a non-contact manner while maintaining a gap of about several μm and go inside the pad. Therefore, a method that can increase the degree of vacuum is proposed. In this case, the pad center reachable until no problem about the vacuum degree in the irradiation of the electron beam (about 10- ⁴ Pa), placed in this way only a portion necessary under vacuum, a partial vacuum system, feed mechanism A gas bearing can be used, and an electron beam exposure apparatus capable of a highly accurate positioning and feeding mechanism was realized.

  By the way, the resolution of EB (= electron beam diameter) is closely related to the work distance (distance between the objective lens of the electron gun and the work: WD), as shown in the equation (1). Here, the amount of WD varies depending on the type of electron gun, but in general, it is often several mm to several tens of mm.

[Equation 1]
L∝d d: electron beam diameter, L: work distance (WD)

  From this relationship, in order to increase the resolution of EB (small beam diameter), the work distance must be shortened. However, in the case of the partial vacuum type electron beam irradiation apparatus developed by the present applicant, a static pressure floating pad enters between the electron gun and the work due to its structure, so there is a limit to shortening the work distance. is there. Furthermore, since it is necessary to provide the vacuum seal valve proposed in the vacuum sealing method (see Patent Document 1) in the electron beam irradiation apparatus using the differential hydrostatic levitation pad in this pad, 8.5 mm WD is currently used. The beam diameter is 100 nm or less.

  By the way, looking at the development trend of the latest optical disc, it has been achieved by the applicant's partial vacuum electron beam exposure apparatus to record data for a capacity of 150 GB in terms of a disc having a radius of Φ120 mm. In this case, the width of the pit pattern is 95 nm and the track pitch is 130 nm, which cannot be achieved by a conventional racer light source, and is therefore exposed by an electron beam. As described above, regarding the optical disc, if the beam diameter (resolution) is 100 nm or less achieved by partial vacuum, it seems that there is no problem in the exposure process that is required for the time being.

  However, EB is used as an SEM (electron microscope) for observing the pattern shape after exposure and measuring the length. In this case, for example, when observing a pattern with a line width of 95 nm, the minimum required accuracy (resolution) is required to be one digit higher than that (resolution). Therefore, it is necessary to narrow the beam diameter to several nm, and it is very difficult to meet the demand for higher resolution of the EB in the partial vacuum method. As one solution to increase the resolution of EB, conventionally, in an electron beam exposure apparatus, an electron gun, a feed mechanism, and a rotation mechanism system, all vacuum methods in which all are placed in a vacuum chamber, can be considered. The mainstream of electron beam exposure apparatuses for semiconductors. The all-vacuum method allows the WD to be reduced without any restriction in order to reduce the electron beam diameter (resolution UP), while the gas bearing responsible for the precision feed mechanism and rotation mechanism can be used in vacuum. Technology is difficult, and every manufacturer is struggling to realize. The development of an electron beam exposure apparatus capable of a high-precision feed / rotation mechanism that solves the disadvantages of the all-vacuum method is awaited.

Further, as a vacuum slide device, a slide shaft that penetrates the vacuum chamber, an X stage substrate that is coupled to the slide shaft, an air slide bearing that guides the slide shaft outside the vacuum chamber, and a gas that enters the vacuum chamber A partition that prevents inflow, an actuator outside the vacuum chamber, and an air slide bearing has an air pad for floating the slide shaft and an exhaust groove for exhausting the gas, and the air slide bearing is a slide shaft. A technique is disclosed in which an X-stage substrate is driven by an actuator via a drive rod in a state in which the actuator is floated (see Patent Document 2).
JP 2002-257998 A JP 2001-44107 A

  As described above, the construction of a high-accuracy feed mechanism in vacuum (for example, using a gas bearing (air slide)) is very difficult due to its structure. For this reason, the present applicant has proposed an EB exposure apparatus using a partial vacuum method in which only necessary portions are placed in a vacuum. However, it is impossible to reduce the work distance in order to increase the resolution of EB. Had a fatal structural problem.

  On the other hand, in a conventional electron beam exposure apparatus, with the all-vacuum system in which all components such as an electron gun and a feed mechanism system are placed in a vacuum chamber, it is easy to increase the resolution of EB, but gas bearings are simple. It could not be used, and it was very expensive to use. For this reason, it is difficult to increase the accuracy of the feed mechanism and the rotation mechanism, and the apparatus itself is very large.

  For example, in an electron beam exposure apparatus for optical discs, a spindle motor that rotates the master and a moving stage are configured in a vacuum, the spindle motor is placed outside the vacuum chamber, and a magnetic fluid seal is used to maintain the vacuum state. When the rotation stage is transmitted to the ball screw in the vacuum chamber and the moving stage using the rolling bearing is driven, the magnetic fluid seal is used in part, so the friction is generated and the accuracy is lowered. In addition, it is difficult to provide a highly accurate feed rotation mechanism.

  The above-described slide shaft described in Patent Document 2 is a structure made of a square ceramic, which is strong against load rigidity, but has a disadvantage that it is very difficult to manufacture and expensive.

  Therefore, the present invention makes it possible to realize a nanometer-order high-precision feed mechanism and rotation mechanism (gas bearing) in vacuum with a simple structure and at a low cost, and further limit the shortening of the work distance. The purpose is to enable high resolution without the loss.

  In order to solve the above-mentioned problems and achieve the object of the present invention, in the electron beam irradiation apparatus of the present invention, the slide mechanism has a static pressure levitation function and a levitation function that levitates from the slide shaft by supplying compressed air to the gas bearing portion. It has a multi-stage differential exhaust function for exhausting the compressed air for use so that the degree of vacuum increases stepwise.

  In addition, the spindle mechanism is equipped with an air spindle that controls the rotation mechanism on the slide shaft in the vacuum chamber. Has a plurality of stages of differential exhaust functions for exhausting the air so that the degree of vacuum increases stepwise.

  As a result, in the slide mechanism, compressed air is supplied to the gas bearing portion by the static pressure levitation function and floats from the slide shaft, and the degree of vacuum of the levitation compressed air is increased stepwise by the differential exhaust function. By evacuating in a plurality of stages, the vacuum state of the gap between the slide shaft and the slide mechanism can be maintained.

  In the spindle mechanism, an air spindle that controls the rotation mechanism is mounted on the slide shaft in the vacuum chamber, and it is floated from the air spindle by the supply of compressed air to the gas bearing by the static pressure levitation function, and differential exhaust By evacuating a plurality of stages so that the degree of vacuum of the rising compressed air increases stepwise by function, the vacuum state of the gap between the air spindle and the spindle mechanism can be maintained. The air spindle can perform a highly accurate rotation mechanism (non-contact) and vacuum maintenance by a differential exhaust function.

Thereby, shortening of the work distance leading to high resolution of the electron gun can be realized.
In addition, by using a hollow shaft as the slide shaft, wiring and piping to the air spindle in the vacuum chamber can be performed through the inside, and the influence of wiring and piping stress on high-precision feeding can be eliminated.

Further, by driving the slide shaft end outside the vacuum chamber with an actuator, it is possible to eliminate the influence (heating, emission gas, enlargement of the vacuum chamber) when the actuator is placed in a vacuum.
Further, in order to realize high-precision feeding, the Abbe error can be eliminated by arranging the laser scale in the middle between the slide shafts.

  Thereby, it is possible to realize a compact exposure apparatus by electron beam irradiation that enables a high-precision feeding mechanism and a rotating mechanism by using an air slide and an air spindle in a vacuum.

  According to the present invention, in an exposure apparatus using electron beam irradiation for an all-vacuum type optical disk, a gas bearing for a slide shaft of a slide mechanism provided outside the vacuum chamber and a gas bearing for an air spindle of a spindle mechanism disposed inside the chamber By incorporating a differential pumping mechanism into the slab, it is possible to realize a highly accurate feeding mechanism and rotating mechanism (gas bearing) in the order of nanometers in a vacuum with a simple structure. In addition to this, by directly attaching the electron gun to all the vacuum chambers, there is no limit to shortening the work distance, and high resolution can be achieved.

  In addition, by connecting the gas bearing to the slide shaft of the slide mechanism and the vacuum chamber with a double bellows, the external force applied to the bearing is controlled by controlling the pressure between the inner and outer bellows by the pressure in the vacuum chamber (vacuum). Therefore, it is possible to always achieve a constant flying height of the gas bearing and to realize stable feeding.

  In addition, by installing an actuator or laser scale that slides the slide shaft outside the vacuum chamber, it is possible to use a minimum vacuum chamber that is approximately the size of the workpiece, and to realize a compact device. The installation area of the apparatus can be reduced, and the time required for evacuation can be shortened. In addition, special vacuum specifications (heat countermeasures, surface treatment, etc.) are not required outside the vacuum chamber. Therefore, conventional parts can be used, and the structure is simple and can be manufactured at low cost.

  In addition, by using a hollow shaft as the slide shaft, piping and wiring to the air spindle in the vacuum chamber can be performed, and stress of piping and wiring can be improved, and workability during assembly can be improved.

Specific embodiments of the present invention will be described below with reference to the drawings as appropriate.
First, FIG. 1 shows an overall view of a schematic differential exhaust type spindle mechanism and slide mechanism.
In FIG. 1, two gas bearings 2 arranged as a pair at a position outside the vacuum chamber 1 are connected to the vacuum chamber 1 by a double bellows 9. The double bellows 9 is configured to evacuate the inside and supply compressed air to the outside.

  The slide shaft 3 employed in the present embodiment is a metal round hollow shaft, and there are general standard products. In addition, since the gas bearing 2 to be fitted to the slide shaft 3 is also round, high precision machining is possible with a lathe or an inexpensive machine tool. Production is possible.

  The hollow slide shaft 3 is combined with a gas bearing 2 processed with high precision while maintaining a very small gap of several μm. Normally, two or more pairs of slide shafts and bearings are used, and a rotating air spindle 4 is arranged between the shafts, so that the load is evenly shared by the plurality of shafts. Since the slide shaft 3 has a hollow structure and is connected to the outside of the vacuum chamber 1, the air spindle arranged inside the vacuum chamber 1 can be easily supplied and differentially evacuated to the air spindle 4 by using the floating compressed air. In addition, a tube for connecting the air spindle 4 and a power cable to the spindle motor for rotation of the air spindle 4 are supplied to supply the compressed air for floating and the power voltage for rotation, and differential exhaust can be performed.

  In the case of a conventional vacuum apparatus, a metal flexible material is used for piping in the vacuum chamber in order to clear the problem of emitted gas. This piping requires a vacuum seal by welding at the joint and a special seal joint. In addition, since the pipe resistance at the time of slide feed is large and the control parameter varies depending on the bending radius of the pipe, it is difficult to perform stable control over the entire stroke at the time of slide feed. On the other hand, for the wiring, a hermetic seal having both an insulating function and a vacuum sealing function is required.

  Therefore, by passing the power cable and the tube of the tube through the shaft of the slide shaft 3 as in the present embodiment, the complicated piping and wiring work in the vacuum chamber 1 and the feeding accuracy due to the piping tension at the time of slide feeding can be achieved. Deterioration can be prevented and feed accuracy can be improved.

  Further, the gas bearing 2 is formed by the position adjusting mechanism 10 with respect to the vacuum chamber 1 in the height direction of the gas bearing 2 and the air formed by the gas bearing 2 with respect to the upper end surface of the vacuum chamber 1 via the slide shaft 3. The tilt angle indicating the angle of the upper end surface of the spindle 4 is adjusted.

FIG. 2 shows an enlarged view of the differential exhaust type air slide portion.
The basic operation of the gas bearing 2 constituting the differential exhaust type air slide part is exactly the same principle as the static pressure floating pad proposed by the present applicant in the partial vacuum electron beam exposure apparatus described in Patent Document 1. . The difference is that the static pressure levitation pad is formed in a circular plane shape, and the gap between the static pressure levitation pad and the disk master is maintained in a high vacuum state as it goes to the center of the circle, whereas the gas bearing 2 has a hollow cylindrical shape. The gap between the gas bearing 2 and the slide shaft 3 is maintained at a high vacuum state as it goes to the vacuum chamber 1 side.

  In FIG. 2, by supplying compressed air having a pressure of about 0.5 MPa from a compressed air pump (not shown) to the porous portion 5 of the gas bearing 2, the gas bearing 2 and the slide shaft 3 maintain a gap of about several μm. Ascend without contact. Inside the porous portion 5 (in the vacuum chamber 1 side), a plurality of grooves 6, 7 and 8 (shown in three steps in FIG. 2) are provided, each of which is not shown outside the gas bearing 2 independently. Connected to an exhaust vacuum pump.

These grooves 6, 7, 8 are intended to exhaust gas from the floating compressed air leaking from the porous portion 5, and the exhaust grooves 6, 7, 8 are provided on the vacuum chamber 1 side. The high vacuum (5 × 10 ⁻³ Pa) inside the vacuum chamber 1 evacuated by a turbo pump (not shown) is set by increasing the degree of vacuum by the effect of differential pumping in the order of the grooves 6, 7, and 8. Can be maintained.

  On the other hand, a position adjusting mechanism 10 shown in FIG. 1 is provided below the gas bearing 2 so that the gas bearing 2 and the slide shaft 3 always have a uniform flying height. Therefore, the gas bearing 2 and the vacuum chamber 1 are connected and vacuum-sealed by a metal-made flexible double bellows 9. However, when the inside of the vacuum chamber 1 is in a vacuum state, a force that the bellows having an effective cross-sectional area of the double bellows 9 minus minus 1 atm is contracted is generated in the gas bearing 2, so that the flying height is uneven, and the gas bearing 2 And the slide shaft 3 may come into contact with each other. Therefore, in order to cancel this contraction force, the structure of the double bellows 9 is adopted, and the position of the gas bearing 2 is controlled to be always the same by evacuating the inside and supplying the compressed air to the outside. ing.

  Since the inside of the slide shaft 3 has a hollow structure, as shown in FIG. 11, a tube for supplying and differentially exhausting the compressed air for levitation to the air spindle 4 from the inside of the vacuum chamber 1 is provided inside the pipe. Further, wiring materials such as a power cable and an encoder output to the spindle motor for rotation of the air spindle 4 can be passed to supply the compressed air for floating and the power voltage for rotation, and differential exhaust can be performed.

FIG. 3 shows an enlarged view of the differential exhaust type air spindle unit.
The gas bearing 12 constituting the differential exhaust type air spindle unit is basically configured similarly to the gas bearing 2 of the air slide unit shown in FIG.
In FIG. 3, by supplying compressed air from the air supply port 13 to the porous portion 15 of the gas bearing 12, the air spindle 4 floats in a non-contact manner with a gap of about several μm. Above the porous portion 15 of the gas bearing 12 (on the vacuum chamber 1 side), a plurality of grooves 17, 18, 19 are provided (in the drawing, three stages are shown), and each is independently outside the air spindle 4. The hollow slide shaft 3 is connected to an exhaust vacuum pump (not shown) through the hollow slide shaft 3.

  These grooves 17, 18, 19 are intended to exhaust the floating gas leaking from the porous portion 15 of the gas bearing 12, and these exhaust grooves 17, 18, 19 are located on the vacuum chamber 1 side. As it goes, the degree of vacuum can be increased by the effect of differential pumping in the order of the grooves 17, 19, and 18, whereby a high vacuum (5 × 10 −3 Pa inside the vacuum chamber 1 exhausted by a turbo pump (not shown) Can be maintained.

  In order not to leak the magnetic field of the coil of the spindle motor 14 to the outside, the entire differential exhaust air spindle unit including the encoder 14-1 is housed in a dedicated box 20 made of a high permeability material and slide The shaft 3 is vacuum-sealed with an O-ring 16 for example. For this reason, the box 20 dedicated for storage can be placed in an air atmosphere, and the conventionally used air spindle can be used as it is.

FIG. 4 shows a configuration diagram of an electron beam irradiation apparatus to which the present embodiment is applied.
The basic configurations of the differential exhaust type air slide unit 25 and the differential exhaust type air spindle unit 26 are the same as those shown in FIGS. 1, 2 and 3, but the actual apparatus configuration includes a vacuum chamber. 1 is provided with an electron gun 23.

  Due to the action of the differential exhaust 27 of the differential exhaust type air slide part 25 and the differential exhaust type air spindle part 26, a high degree of vacuum (5 × 10 −3 Pa or more) inside the vacuum chamber 1 exhausted by a turbo pump (not shown). ) 28 and the differential exhaust type air spindle unit 26 can be placed in an atmospheric atmosphere 29. Also, as shown at 30, the differential exhaust type air slide unit 25, the drive system, and the vacuum piping are all in the atmosphere. It can be installed in the atmosphere.

  With this structure, the objective lens at the tip of the electron gun 23 can be brought close to the workpiece 24 without limitation (shortening of the WD), and the beam diameter of the electron beam can be reduced (higher resolution). Thereby, refinement | miniaturization of an exposure pattern can be achieved.

  In addition, as an actuator for driving the slide shaft 3, for example, a driving voice coil motor: VCM 21 and a laser scale 22 for performing high-precision positioning can be installed in the air atmosphere outside the vacuum chamber 1. Like the air spindle, the conventional technology and parts can be diverted, no special vacuum measures (heat generation, emission gas) are required, and it can be manufactured easily and inexpensively.

  In the present embodiment, the apparatus is configured to move in the horizontal direction shown in FIG. 4 and place the electron gun 23 on the upper side of the vacuum chamber 1. Alternatively, the electron gun 23 may be installed in the horizontal direction of the vacuum chamber 1 and the slide shaft 3 may be installed in the vertical direction. Further, for example, in the case of a configuration using two slide shafts 3, by placing the laser scale 22 at an intermediate position between the shafts, it is possible to eliminate the influence of errors resulting from Abbe's principle, and further controllability. Improvement and high precision positioning on the order of nm are possible.

It is a general view which shows a differential exhaust type spindle mechanism and a slide mechanism. It is an enlarged view which shows a differential exhaust type air slide part. It is an enlarged view which shows a differential exhaust type air spindle part. It is a figure which shows the structure of an electron beam irradiation apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Vacuum chamber, 2 ... Gas bearing, 3 ... Slide shaft, 4 ... Air spindle, 5 ... Porous part, 6, 7, 8 ... Groove, 9 ... Double bellows, 10 ... Position adjustment mechanism, 11 ... Inside pipe 12 ... Gas bearing, 13 ... Air supply port, 14 ... Spindle motor, 14-1 ... Encoder, 15 ... Porous part, 16 ... O-ring, 17, 18, 19 ... Groove, 20 ... Special box, 21 ... VCM for driving, 22 ... Laser scale, 23 ... Electron gun, 24 ... Workpiece, 25 ... Differential exhaust air slide part, 26 ... Differential exhaust air spindle part, 27 ... Differential exhaust, 28 ... High vacuum (5 × 10-3Pa or more), 29 ... Air atmosphere, 30 ... Drive system and vacuum piping can all be installed in air atmosphere

Claims (2)

A slide shaft is slidable by a slide mechanism with respect to a vacuum chamber in which an electron beam column is built, and the irradiated object rotated by a spindle mechanism connected to the slide shaft in the vacuum chamber is moved from the electron beam column to the irradiated object. In an electron beam irradiation apparatus irradiated with an electron beam,
The slide mechanism has a static pressure levitation function for levitating from the slide shaft by supplying compressed air to the gas bearing portion and a multi-stage differential for exhausting the levitation compressed air in stages to increase the degree of vacuum. Has an exhaust function,
The spindle mechanism is equipped with an air spindle that controls the rotation mechanism on the slide shaft in the vacuum chamber, and the static pressure levitation function for levitation from the air spindle by supplying compressed air to the gas bearing and the levitation An electron beam irradiation apparatus characterized by having a multi-stage differential exhaust function for exhausting the compressed air in a stepwise manner so that the degree of vacuum increases. In the electron beam irradiation apparatus with which the electron beam of Claim 1 is irradiated,
The slide shaft is a metal round hollow shaft, and the slide shaft has a hollow portion capable of supplying and exhausting compressed air in the spindle mechanism and allowing electric wiring to the air spindle, An actuator that slide-drives the slide shaft at the end of the slide shaft opposite to the vacuum chamber;
The gas bearing portion and the vacuum chamber are coupled by a double bellows that evacuates inward and supplies compressed air to the outside, and the double bellows are axial and radial directions of the slide mechanism with respect to the vacuum chamber. An electron beam irradiation apparatus characterized in that it is provided so as to absorb the force of.

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