JP2007057021A - Linear guide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a linear guide capable of keeping atmosphere in a chamber without substantially increasing costs. <P>SOLUTION: Uplift force FL, FR of a slider 4 generated by a left static pressure pad 3a and a right static pressure pad 3a are made to be different from each other (FL<FR) by changing a pressure distribution of a gas, and a relationship of moments obtained by multiplying a distance LL from a center of gravity G of a slider 4 and a table 4 to a center of the left static pressure pad 3a, and a distance LR from the center of gravity G to a center of the right static pressure pad 3a by the uplift force satisfies FL×LL<FR×LR, thus the slider 4 can be horizontally placed by utilizing momental difference, and minimal supervision of a clearance to a fixed base 2 can be performed. Accordingly, a gas overflown from a recessed portion 2b through between the fixed base 2 and the slider 4 is captured, and high vacuum atmosphere in the chamber 1 can be kept. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a linear guide that guides a slider in a chamber that is used in, for example, a semiconductor manufacturing apparatus and is maintained in a special atmosphere different from atmospheric pressure.

  In a semiconductor manufacturing apparatus or the like, a workpiece is placed on a stage connected to a slider and moved to perform processing in a process chamber maintained in a vacuum or special gas atmosphere. Here, when the slider is supported in a vacuum atmosphere, if a rolling bearing or the like is provided, the lubricant used for the slider may contaminate the vacuum atmosphere. Therefore, it is necessary to use a special lubricant. On the other hand, the slider is also supported by a hydrostatic bearing that does not require the use of a lubricant that contaminates the vacuum atmosphere.

However, since the hydrostatic bearing is supported in a non-contact state by discharging gas to the slider, if left unattended, the atmospheric pressure in the vacuum atmosphere rises, and there is a risk that appropriate processing cannot be performed. is there. Therefore, it has been considered to arrange a differential exhaust seal or the like as a gas recovery means around the hydrostatic bearing to recover the discharged gas.
WO99 / 66221 pamphlet JP 2002-57206 A

  Here, the differential exhaust seal generally has a space sealed with a minute gap (labyrinth seal), and the space disposed in the middle is forcibly exhausted to improve the sealing performance, such as atmospheric pressure. Seals high pressure and high vacuum. Therefore, the efficiency greatly depends on the size of the minute gap in the seal.

  However, when the slider moves relative to the hydrostatic bearing, the center of gravity of the slider moves relative to the support point, and the slider may be tilted. When the slider is tilted, a minute gap in the differential exhaust seal is widened, and the gas recovery capability is accordingly reduced. In order to suppress the inclination of the slider, it is conceivable to increase the number and area of the hydrostatic bearings, but there arises a problem that the apparatus becomes larger and the cost increases. On the other hand, in order to maintain sufficient gas recovery capability even when a minute gap is widened, the suction force of the differential exhaust seal can be increased, but a high exhaust capacity pump is used or the air tightness of the piping system is increased. It is necessary to take measures such as this, which also causes high costs.

  The present invention has been made in view of the problems of the prior art, and an object thereof is to provide a linear guide capable of maintaining the atmosphere in the chamber without significantly increasing the cost.

The linear guide of the present invention is a linear guide used in a chamber that separates the atmospheric environment from the atmospheric environment.
A fixed base;
A slider arranged to be movable with respect to the fixed base;
A hydrostatic bearing that is provided on one of the fixed base and the slider and that discharges gas to the other;
A gas recovery means disposed so as to surround the hydrostatic bearing and recovering the gas discharged from the slider;
The pressure of the gas discharged from the hydrostatic bearing is controlled according to the inclination of the slider.

  When the center of gravity moves with respect to the hydrostatic bearing in accordance with the movement of the slider, and the tilt of the slider occurs, the distance between the gas recovery means and the slider is partially separated. In this case, the gas recovery capability decreases. On the other hand, according to the linear guide of the present invention, the pressure of the gas discharged from the hydrostatic bearing is controlled in accordance with the inclination of the slider. Alternatively, the inclination of the slider can be reduced by relatively lowering the gas discharge pressure that is farther from the slider and relatively increasing the gas discharge pressure that is closer to the fixed base or the slider. It correct | amends and, thereby, can maintain the gas recovery capability of the said gas recovery means, and can suppress that the atmosphere in the said chamber is impaired.

  It is preferable that the gas recovery means includes a differential exhaust seal because foreign substances can be prevented from entering the chamber.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 is a side view of a linear guide according to the present embodiment, FIG. 2 is a view of the configuration of FIG. 1 taken along line II-II and viewed in the direction of the arrow, and FIG. It is the figure which cut | disconnected this structure by the III-III line | wire and looked at the arrow direction.

  1 and 2, a fixed base 2 is arranged so that four legs 2a are fixed to the bottom surface of the chamber 1 whose interior is maintained in a high vacuum atmosphere. The fixed base 2 has a concave section 2b having a rectangular cross section at the center, and two rows of vertical static pressure blocks 3 and 3 are arranged in parallel inside the concave section 2b. Each static pressure block 3 has a prismatic shape extending in the horizontal direction as a whole, and three static pressure pads 3a (6 in total) are provided on the upper surface in the vicinity of both ends. The static pressure pad 3a is connected to a pressure control device 10 including a positive pressure pump via a pipe H0 (not shown) (see FIG. 4).

  In FIG. 2, four first passages H <b> 1 are provided so as to extend from the bottom surface of the recess 2 b to the outside through the fixed base 2 and the chamber 1. The first passage H1 is connected to the first exhaust pump P1. On the upper surface of the fixed base 2b, two track grooves 2c and 2d are formed so as to surround the recess 2b (see FIG. 3). Four second passages H2 and third passages H3 are provided so as to extend from the bottom surfaces of the track grooves 2c and 2d to the outside through the fixed base 2 and the chamber 1, respectively. The second passage H2 is connected to the second exhaust pump P2, and the third passage H3 is connected to the third exhaust pump P3. The recess 2b, the track grooves 2c and 2d, the passages H1 to H3, and the pumps P1 to P3 constitute gas recovery means.

  A flat slider 4 is disposed above the fixed base 2, and a table 5 on which a wafer W is placed is fixedly disposed above the slider 4. The slider 4 is connected to a driving device (not shown). A horizontal bearing block 6 is attached to the lower surface of the slider 5. The horizontal bearing block 6 is disposed between the vertical hydrostatic blocks 3 and 3 that also serve as guide rails, and the hydrostatic pads 6a are disposed on both side surfaces so as to face the horizontal hydrostatic blocks. The static pressure pad 6a is connected to a positive pressure pump via a pipe (not shown). The reason why the static pressure pad 6a is on the slider 4 side (bearing moving type) is to avoid an increase in the size of the groove when it is provided on the fixed base 2 side (guide surface moving type). A differential exhaust seal is constituted by the track grooves 2c and 2d and the clearance between the fixed base 2 and the slider 3 around the track grooves 2c and 2d.

  The operation of this embodiment will be described. FIG. 4 is a diagram illustrating a state in which the slider 5 has moved to the stroke end with respect to the fixed base 2. The table 4 floats with respect to the fixed base 2 by the pressure of gas (for example, air) discharged from the static pressure pads 3 a and 3 a of the vertical bearing blocks 3 and 3, and the static pressure pads 6 a and 6 a of the horizontal bearing block 6. It is positioned in the horizontal direction with the pressure of the gas discharged from.

  When a driving device (not shown) operates in this state, the slider 4 together with the table 5 moves in the horizontal direction with respect to the fixed base 2. The gas discharged from the static pressure pads 3a and 3a and the static pressure pads 6a and 6a is stored in the recess 2b and is discharged from here to the exhaust pump P1 via the first passage H1. Further, the gas overflowing from the inside of the recess 2b through the space between the slider 5 is captured by the track grooves 2c and 2d, and from there to the exhaust pumps P2 and P3 via the second passage H2 and the third passage H3. Will be discharged.

  By the way, when the slider 4 moves to the right stroke end with respect to the fixed base 2, the slider 4 protrudes from the right end of the fixed base 2 as shown in FIG. 4. Then, the slider 4 tilts to the right due to the unbalance due to the weight of the overhanging portion of the slider 4. This is called a pitching error.

  Here, as a comparative example, as shown in FIG. 4B, a case where the pressure of the gas blown from the left static pressure pad 3a is equal to the pressure of the gas blown from the right static pressure pad 3a. Think. In this case, the gas pressure is such that there is no contact between the fixed base 2 and the slider 4, but if the inclination angle is small, the flying force FL of the slider 4 generated by the left and right static pressure pads 3a, Since the FRs are substantially equal, a distance LL from the center of gravity G of the slider 4 and the table 4 to the center of the left static pressure pad 3a and a distance LR from the center of gravity G to the center of the right static pressure pad 3a are respectively determined. The relationship of the moments multiplied is such that FL × LL> FR × LR is satisfied, and the slider 4 is further tilted to the right.

  In this case, as shown in FIG. 4B, the gap between the upper surface on the left end side of the fixed base 2 and the lower surface of the slider 4 increases, and the gas overflows from the inside of the recess 2 b through the space between the slider 4. May not be captured by the track grooves 2c and 2d having a reduced gas recovery performance, and may leak into the chamber 1.

  Thus, in the present embodiment, the pressure control device 10 causes the pressure of the gas blown from the right static pressure pad 3a to be higher than the pressure of the gas blown from the left static pressure pad 3a. Control is in progress. Such gas pressure control preferably gives a larger pressure difference as the overhang of the slider 4 increases, that is, the pressure difference is changed in accordance with the relative position between the slider 4 and the fixed base.

  By changing the gas pressure distribution in this way, as shown in FIG. 4A, the flying force FL, FR of the slider 4 generated by the left static pressure pad 3a and the right static pressure pad 3a is increased. The distance LL from the center of gravity G of the slider 4 and the table 4 to the center of the left static pressure pad 3a and the distance LR from the center of gravity G to the center of the right static pressure pad 3a are different (FL <FR). The relationship between the moments obtained by multiplying each of the above is established by FL × LL <FR × LR. Therefore, by utilizing this moment difference, the slider 4 can be positioned horizontally, and the minimum gap with respect to the fixed base 2 can be minimized. Can be managed. Accordingly, since the gap between the upper surface on the left end side of the fixed base 2 and the lower surface of the slider 4 becomes narrow and uniform, the gas recovery performance by the track grooves 2c and 2d is exhibited, so that the space between the slider 4 and the slider 4 is interposed. The gas overflowing from the inside of the recess 2b can be captured, and the high vacuum atmosphere in the chamber 1 can be maintained.

  Furthermore, as in the comparative example shown in FIG. 4B, when the gas pressure distribution is uniform, the minimum static pressure rigidity must be ensured even when the slider 4 is tilted. It is necessary to increase the gas discharge pressure, which requires an increase in the capacity of the positive pressure pump and an increase in the area of the static pressure pad 3a. On the other hand, according to the present embodiment, the gap between the slider 4 and the fixed base 2 is minimized to increase the capacity of the positive pressure pump and the area of the static pressure pad 3a. Therefore, the required bearing rigidity can be ensured, and the size and cost of the apparatus can be reduced.

  In the above-described embodiment, the hydrostatic bearing is arranged on the fixed base side, which is a countermeasure against the occurrence of a pitching error due to the movement of the center of gravity of the slider. The present invention can also be applied to the arranged examples. In particular, when the hydrostatic guide to which the present invention is applied is equipped with another one-axis moving table, the posture of the lower shaft may change depending on the position of the center of gravity of the upper table. The pressure control is effective.

  Furthermore, the present invention can also be used in the case of suppressing a gap that is widened due to an attitude error caused by the center of gravity of the slider, the arrangement of the guide rail, and the arrangement of the drive system. In the four-surface constraining type or journal bearing, since the gap change tends to be opposite to the gap change of one side, the effect of the present invention is small. However, downsizing the hydrostatic bearing by attitude control by changing the gas pressure distribution enables downsizing of the overall configuration.

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be modified or improved as appropriate. The inside of the chamber may be filled with a special gas different from the atmosphere instead of a vacuum. As a driving mode of the slider, it is possible to use a ball screw mechanism, a linear motor, an ultrasonic motor, a pneumatic cylinder, or the like.

It is a side view of the linear guide concerning this Embodiment. It is the figure which cut | disconnected the structure of FIG. 1 by the II-II line | wire, and looked at the arrow direction. It is the figure which cut | disconnected the structure of FIG. 1 by the III-III line | wire, and looked at the arrow direction. It is a figure which shows the state which the slider 5 moved to the stroke end with respect to the fixed base 2, (a) shows embodiment, (b) shows a comparative example, but the inclination of a slider is exaggerated.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chamber 2 Fixed base 2a Leg part 2b Recessed part 2c, 2d Track groove 3 Vertical bearing block 3a Static pressure pad 4 Slider 5 Table 6 Horizontal bearing block 6a Static pressure pad 10 Pressure control device H0 Piping H1 1st path H2 2nd path H3 Third passage P1 First exhaust pump P2 Second exhaust pump P3 Third exhaust pump

Claims (2)

In the linear guide used in the chamber separating the atmospheric environment from the atmospheric environment,
A fixed base;
A slider arranged to be movable with respect to the fixed base;
A hydrostatic bearing that is provided on one of the fixed base and the slider and that discharges gas to the other;
A gas recovery means disposed so as to surround the hydrostatic bearing and recovering the gas discharged from the slider;
A linear guide characterized in that the pressure of the gas discharged from the hydrostatic bearing is controlled in accordance with the inclination of the slider. The linear guide according to claim 1, wherein the gas recovery means includes a differential exhaust seal.

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