Patent Application
20100084578
The present invention relates to an electron beam lithography apparatus and a stage mechanism thereof that can be used in a mastering process for a record disc master or the like.
In the mastering process for a master of optical discs, pits and grooves are formed usually by exposing a resist film to a laser beam. A laser beam recorder (LBR) used in this mastering process uses as its light source UV (ultraviolet), Deep-UV (far ultraviolet) with which the beam diameter can be further reduced, or the like. The exposure limit of a laser beam, that is, the record density of an optical disc is determined by the light diffraction limit determined by the light wavelength and the numerical aperture of an object lens. In recent years, an electron beam lithography method used in a semiconductor process has been investigated for the purpose of forming minute pits or grooves sized beyond the exposure limit of a laser beam to improve the record density of optical discs. By adopting this electron beam lithography method, the master production for discrete track media, patterned media, and the like that are promising as future technology for high density hard disks as well as for high density optical discs such as blue ray discs is expected to be dealt with.
In order to make the air spindle operate in the vacuum chamber, measures of some kind are needed which introduces high pressure air for an air bearing, electric signals for motor drive, and the like from outside of the vacuum chamber into the air spindle and which exhausts air used in the bearing out of the vacuum chamber. As this means, conventionally, a flexible pipe such as a bellows or a flexible tube has been used. Here, since the rotating stage is mounted on the X-stage, the pipe connecting to the air spindle deforms in response to the movement of the X-stage. The deformation of the pipe during the movement of the X-stage may hinder the feed operation of the X-stage, thus preventing highly accurate positioning control. Jpn. Appl. Phys. Vol. 40 (2001) PP. 1653-1660 (Non-patent reference 1) discloses a piping method where a metallic flexible tube 107 leading from the side of the rotating stage upper portion to a bulkhead of the vacuum chamber is laid to be shaped like a “U” turned on its side as shown in
Meanwhile, Jpn. Appl. Phys. Vol. 43 (2004) PP. 5068-5073 (Non-patent reference 2) and Japanese Patent Application Laid-Open Publication No. 2003-287146 (Reference 1) disclose an apparatus equipped with a bellows elastic in the X-direction. However, the spring force of the bellows and the sliding frictional resistance of a guiding mechanism provided to prevent the bellows from buckling cause a decrease in the movement accuracy of the X-stage.
The present invention was made in view of the above problem, and an object thereof is to provide a stage mechanism capable of more highly accurate positioning control by reducing the movement load on the X-stage due to the rotating stage piping, and an electron beam lithography apparatus equipped with this stage mechanism.
According to the present invention, there is provided a stage mechanism which comprises a positioning mechanism including a rotating stage having a turn table, and a linear movement stage to linearly move the rotating stage for positioning; a vacuum chamber housing the positioning mechanism; and at least one flexible pipe to make the outside of the vacuum chamber and the inside of the positioning mechanism communicate. The vacuum chamber has a lower space that spreads underneath the underside of the positioning mechanism, and the pipe leads from a surface of the positioning mechanism through the lower space to an inside wall of the vacuum chamber.
According to the present invention, there is provided an electron beam lithography apparatus which comprises a positioning mechanism including a rotating stage having a turn table, and a linear movement stage to linearly move the rotating stage for positioning; an electron beam irradiating means to irradiate an electron beam onto a disc master mounted on the rotating stage to form record marks; a vacuum chamber housing the positioning mechanism; and at least one flexible pipe to make the outside of the vacuum chamber and the inside of the positioning mechanism communicate. The vacuum chamber has a lower space that spreads underneath the underside of the positioning mechanism, and the pipe leads from a surface of the positioning mechanism through the lower space to an inside wall of the vacuum chamber.
Embodiments of the present invention will be described with reference to the drawings. The same reference numerals are used to denote substantially the same or equivalent constituents or parts throughout the figures cited below.
Of the above constituents of the air spindle, the ones other than the turn table 5 are housed in an airtight way in a housing 13. Vacuum bulkheads 14 are walls separating the inside and outside of a vacuum chamber in an airtight way, and the rotating stage 1 is placed inward of the vacuum bulkheads 14, that is, in the vacuum atmosphere inside the vacuum chamber. Note that there is atmospheric pressure outward of the vacuum bulkheads 14 and inside the housing 13.
Feedthroughs A1 to A5 are provided on the vacuum bulkheads 14, and feedthroughs B1 to B5 are provided on the bottom of the housing 13 of the rotating stage 1. The feedthrough forms a linkage of pipes or wires inward and outward of a bulkhead, and its airtightness is secured so that air does not leak into the vacuum chamber through the linkage. Piping and wiring over inward and outward of the vacuum bulkheads 14 are implemented via these feedthroughs. Namely, the supply of compressed air to the air spindle, the exhaust of air from the air spindle, and the supply of drive electric power to the AC servo motor 11 are implemented via the feedthroughs. An air supply pipe 15 is connected between the bearing inlet 8 and the feedthrough B1. A small-diameter flexible tube 16 of, e.g., ½ inch or less in outer diameter that is made of metal such as stainless is connected between the feedthrough B1 and the feedthrough A1. By this piping, compressed air can be supplied to the air spindle from outward of the vacuum bulkheads 14 with maintaining the degree of vacuum in the vacuum chamber. Further, feeder lines 25 are connected respectively between the AC servo motor 11 and the feedthrough B2 and between the feedthrough B2 and the feedthrough A2. By this means, drive electric power is supplied to the AC servo motor 11 from outward of the vacuum bulkheads 14 with maintaining the degree of vacuum in the vacuum chamber. Moreover, a small-diameter flexible tube 17 of, e.g., ½ inch or less is connected between the feedthrough B3 and the feedthrough A3. By this means, part of the compressed air supplied to the vacuum bearings 5, 6 is exhausted outward of the vacuum bulkheads 14 via the flexible tube 17. Yet further, exhaust pipes 23, 24 are connected respectively between bearing outlets 21, 22 and the feedthrough B4, B5, and small-diameter flexible tubes 18, 19 of, e.g., ½ inch or less are connected respectively between the feedthrough B4, B5 and the feedthrough A4, A5. By this piping, air which has flowed into the noncontact seal portions 20 can be differentially exhausted outward of the vacuum bulkheads 14.
Each of the flexible tubes 16 to 19 and the feeder line 25 connecting the feedthroughs B1 to B5 provided on the bottom of the housing 13 and the feedthroughs A1 to A5 provided on the vacuum bulkheads 14, is laid hanging down in the middle part to be shaped substantially like a “U” as shown in
A vacuum chamber 50 housing an X-stage 40 and the rotating stage 1 in an airtight way is provided with a trench-like space that spreads underneath the bottom of the X-stage 40. The upper portion of the rotating stage including the X-stage 40 and the turn table 5 is housed in a space 50a (hereinafter called a first region) above the trench-like space. Meanwhile, the lower portion of the rotating stage and the pipes for air supply to and exhaust from the air spindle and for power feeding thereto are placed in the trench-like space 50b (hereinafter called a second region). As shown in
The X-stage comprises a feed screw 41 extending in a direction of arrow A (X-direction) in the figure, a shaft 42 linked to an end of the feed screw 41, a motor 43 provided outside the vacuum chamber 50 to drive the shaft 42 to rotate, a female screw 45 that mates with the feed screw 41, a stage portion 44 fixed to the female screw 45, and a base 46 fixed to the bottom of the first region 50a and connected to the other end of the feed screw 41. When the motor 43 is driven, the feed screw 41 is rotated at the same position via the shaft 42, and thereby the female screw 45 and the stage portion 44 move in the X-direction. A through hole is made in the stage portion 44, and the rotating stage 1 is inserted into the through hole. The rotating stage 1 is fixed at its flange 80 to and supported by the stage 40, the flange 80 being formed protruding from the periphery of the rotating stage 1. By this means, the rotating stage 1 can move in the X-direction as the X-stage 40 moves. A disc master 200 is mounted on the turn table 5 on the rotating stage, and at the same time that the rotating stage 1 rotates, the X-stage 40 moves in a disc radial direction (a direction of arrow A in
The rotating stage 1 is mounted such that the lower portion thereof passed through the X-stage 40 is in the second region 50b. Thus, the flexible tubes 16 to 19 and the feeder line 25 attached to the housing bottom of the rotating stage 1 are laid in the second region. The feedthroughs A1 to A5 described above are provided on the side walls of the second region 50b, and between these and the feedthroughs B1 to B5 provided on the housing bottom of the rotating stage, the flexible tubes 16 to 19 and the feeder line 25 are connected to be shaped substantially like a “U”. These pipes and wires hang down in midair in such a way as not to touch a side or bottom on the inside of the vacuum chamber during the movement of the X-stage 40.
Where a vibration-free deck is used to remove vibrations occurring in the apparatus, a through hole is formed in the vibration-free deck 90, and the second region 50b is passed through this through hole, and the bottom of the first region 50a is mounted on the vibration-free deck 90, thereby securing stability.
The movement of the flexible tubes 16 to 19 when the X-stage 40 moves in the X-direction will be described with reference to
As to the flexural rigidity of the flexible tube, complex computation is needed because actually the shape of corrugation needs to be taken into account, but if simply modeled on the assumption that conditions do not change, it can be regarded as the flexural rigidity of a circular pipe. That is, since being proportional to the second moment of area, the flexural rigidity is proportional to the inner diameter cubed for circular pipes of the same wall thickness. In contrast, in the case where multiple pipes of the same inner diameter are arranged in parallel, the second moment of area is proportional to the number of the pipes. Therefore, instead of using a flexible tube of a large inner diameter so that multiple pipes can extend through it as in conventional apparatuses, according to the present embodiment the pipes for air supply and exhaust and for power feeding are individually provided so that each pipe is of a small inner diameter, thereby reducing the flexural rigidity of the pipe. By this means, the movement load on the X-stage can be reduced, achieving highly accurate positioning control.
Depending on the lengths and installation intervals of the pipes, the flexible tubes bunging down in the middle part to be shaped like a “U” may be in contact with each other, which causes frictional resistance, resulting in a decrease in the movement accuracy of the X-stage 40. In order to prevent this, it is desirable that clampers 91 to clamp tubes so as to be apart from each other be provided at appropriate places as shown in
Although in the above embodiment, the feedthroughs are provided on the bottom of the housing 13 of the rotating stage 1, not being limited to this, the feedthroughs B1 to B5 may be provided on the lower portion of the side of the rotating stage located in the second region 50b of the vacuum chamber, and between these and the feedthroughs A1 to A5 provided on the vacuum bulkheads 14, the flexible tubes 16 to 19 and the feeder line 25 may be connected hanging down in the middle part to be shaped substantially like a “U”. Also in this case, each of the U-shaped pipes is laid so as not to touch a side or bottom on the inside of the vacuum chamber 50 during the movement of the X-stage 40.
As obvious from the above description, in the stage mechanism and the electron beam lithography apparatus according to the present invention, the vacuum chamber has the trench-like space that spreads underneath the X-stage, and the pipes and wires connected between the rotating stage and the vacuum bulkheads are laid in this space. These pipes and wires are laid so as to deform in response to the movement of the X-stage without touching an inside wall of the vacuum chamber in this space, and hence frictional resistance and vibration during the movement of the X-stage can be greatly reduced. Therefore, the positioning control of a disc master can be executed more highly accurately, and thus minute pits suitable for high density recording can be formed. By providing flexible tubes of a small inner diameter as these pipes respectively individually, the movement load on the X-stage can be further reduced. Further, because the apparatus can be configured without parts such as bellows or guiding tubes used in conventional apparatuses, both low cost and high reliability can be achieved.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2007/056705 | 3/28/2007 | WO | 00 | 9/25/2009 |
