JPH0779543B2 - Drive mechanism - Google Patents

Description

FIELD OF THE INVENTION The present invention relates to an ultra-precision drive mechanism for semiconductor manufacturing, for example.

(Prior Art) Conventionally, in this type of mechanism, there have been problems such as instability of the operation of the drive system and the bearing system, low accuracy, and heat generation of the drive coil.

(Purpose) In addition to solving the above problems, the present invention can be expected to be downsized.

(Example) Hereinafter, it demonstrates according to a figure. FIG. 1 is a sectional view of an example of the present invention, in which a movable portion 1 is movable in the axial direction with respect to a guide shaft 2 having a circular cross section. A plurality of coils 5a, 5b, 5c are attached to the bearing housing 7 of the movable portion 1 so as to wind the shaft 2, and an air intake port 6 is formed. The air taken in exits the outlet 8 through the surface of the shaft 2. This mechanism can be operated in the vacuum chamber by the vacuum shield portion 8a. The shaft 2 is made of a conductive ferromagnetic material such as iron or steel, and the shaft 7 is made of a non-magnetic material such as ceramic. Reference numeral 9 is a pole piece made of soft iron or the like, which is formed in an annular shape so as to be axially symmetrical with respect to the shaft 2, and the housing 7 is also formed in an annular shape so as to be axially symmetrical.

This is preferable because the yawing of the air bearing is offset by the axisymmetric arrangement. Now, when compressed air is injected from the air intake port 6, a pressure is generated between the housing 7 and the shaft 2, and the entire movable portion 1 becomes free from the shaft 2.
Next, the coils 5a, 5b, and 5c are in phase with each other as shown in FIG.
When a sinusoidal current shifted by 60 ° is applied, a moving magnetic field is generated,
Due to Fleming's right-hand rule, an induced current flows through axis 2,
Next, the movable part 1 moves in the axial direction according to Fleming's left-hand rule. By reversing the relationship of the applied current, it is possible to move in the opposite direction. The heat generated in the coil during this movement is cooled by the air flow in the air bearing, so that the coil is prevented from being damaged.

On the upper surface of the ceramic housing 7, there is mounted a stage 10 which can rotate (θ) and can move in a rotation axis direction (longitudinal direction Z), and an electrostatic chuck 11 for attracting a wafer 12 is mounted thereon. Reference numeral 13 denotes a light flux for exposure of the wafer 12 or an illumination light for alignment. Since the permanent magnet is not used as a drive source in this way, the electrostatic chuck 11 is not adversely affected, and even when an electron beam is used for the alignment light, the coil is not energized during irradiation of the electron beam 13. If it is cut, the electron beam 13 is not adversely affected. Further, it is preferable that the shaft 2 is tightened by the piezoelectric element 15 while the coil is not energized so that the position shift does not occur. FIG. 2 shows another example of the shaft 2 shown in FIG.
The surface layer 3 is a non-magnetic conductor such as aluminum or copper, and the inner shaft 4 is a ferromagnetic material such as iron or steel. As a result, the resistance value of the conductor can be lowered and the current can be increased. It can also be applied to a voice coil type with an electromagnetic scale. FIG. 4 shows the entire top surface and cross section of the exposure stage assembled using FIG. In this way, the circular round shafts 2 are paired to operate stably, and since the axially symmetrical thrust generating portions and the housing portions are provided on each axis, yawing does not occur, and the structure is small. Reference numeral 15 is an air intake, and 16 is a frame.

As described above, in the exposure stage drive mechanism such as the optical stepper, the X-ray, the electron beam ion beam exposure machine, etc., by incorporating the axially symmetric thrust generation unit in the air bearing,
This has the effect of minimizing the yawing moment or the twist of the bearing, increasing the rigidity of the mechanical system, and improving the accuracy during position control.

Further, by disposing the electromagnetic actuator in the air circulation path of the air bearing, the heat generated by the juule heat of the actuator is suppressed, and this also has the effect of minimizing the deterioration of the positional accuracy due to thermal deformation.

Further, there is an effect that the entire device is made small and lightweight.

In addition, since this drive mechanism does not have a permanent magnet, the magnetic field generated by the actuator has the effect of minimizing the error signal given to the position detection.

As described above, according to the drive mechanism of the present invention, the drive coil is arranged in the vicinity of the gap between the gas intake port and the gas outlet port of the gas bearing, so that the drive coil is cooled by the air passing through the gap. As a result, it is possible to minimize the decrease in accuracy caused by thermal deformation due to heat generation of the coil.

[Brief description of drawings]

FIG. 1 is a sectional view of an example of the present invention, FIG. 2 is another example diagram, FIG. 3 is a drive current waveform diagram, and FIG. 4 is an upper surface and a sectional view of the entire exposure stage assembled using FIG. It is a figure. 1 ... Movable part, 2 ... Shaft, 6,8 ... Air inlet / outlet, 5a, 5
b, 5c …… Coil, 7 …… Housing part.

Claims (2)

[Claims] 1. A guide shaft including a conductor, a movable member movable along the guide shaft, and a movable member integrally provided with the movable member.
A drive coil for moving the movable body by generating a moving magnetic field and flowing an induced current in the guide shaft, and a gas bearing for holding the movable body in a non-contact state with the guide shaft with a gap. And an inlet provided on the movable body for introducing gas into the gas bearing, and an outlet for discharging the gas introduced from the inlet and passing through the gap, The drive mechanism is characterized in that the drive coil is provided in the vicinity of the gap between the intake port and the outflow port and is cooled by the gas passing through the gap. 2. The drive mechanism according to claim 1, wherein a wafer is mounted on the movable body.