JPH0568090B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spin coater for semiconductor wafers in which a wafer holder is attached to the end of a drive shaft of a drive motor.

[Prior Art] In conventional spin coaters, the casing of the motor is fixed to the spin coater body. Therefore, the only movement imparted to the wafer was rotation due to rotation of the motor drive shaft.

[Problems to be Solved by the Invention] However, as the wafer size increases, there is a problem in that the exposure agent cannot be uniformly applied to the wafer due to the difference in centrifugal force between the outer circumference and the center of the wafer.

An object of the present invention is to provide a spin coater that can uniformly apply an exposure agent to a wafer.

[Means for Solving the Problems] According to the present invention, in a spin coater for semiconductor wafers in which a wafer holder is attached to the end of a drive shaft of a drive motor, the casing of the motor is supported on the holder body by a support means, and a displacement sensor is provided. A control means is provided for controlling displacement based on a signal from. The support means includes a plurality of coil springs stretched between the outer circumference of the motor casing and the spin coater body, and the control means includes:
Preferably, the electromagnet and the control circuit are provided with a space between them in the casing.

Moreover, the support means and a part of the control means can be constructed from magnetic bearings according to known technology.

Preferably, the control circuit is also provided with a signal generator, a compensation circuit and a driver, and the driver is connected to an electromagnet or a magnetic bearing.

[Function] In the spin coater configured as described above, the displacement sensor detects the distance between the displacement sensor and the motor casing, and the compensation circuit performs control to follow the signal given from the signal generator. Outputs a signal to the driver to control the electromagnet in the magnetic bearing.
Therefore, the wafer is given a motion along a locus that is a mixture of rotation and revolution around the drive shaft, and uneven coating of the exposure agent due to the difference in centrifugal force between the center and the outer circumference is eliminated.

[Examples] Examples of the present invention will be described below with reference to the drawings.

In FIG. 1, the recess 2 of the spin coater main body 1
A drive motor 3 is housed in the drive motor 3, and its drive shaft 4
A wafer holder (not shown) is attached to the upper end of the holder. The motor 3 is supported within the recess 2 by a plurality of coil springs 6, which are supporting means stretched between the motor casing 5 and the main body 1. The main body 1 is provided with an electromagnet 7 having a gap A in the casing 5, and a displacement sensor 8 for detecting the gap A, and the electromagnet 7 and a control circuit 10 (FIG. 2) control the control means. It is configured. A total of four electromagnets 7 are provided in the X-Y direction.

In FIG. 2, the control circuit, generally designated by the reference numeral 10, consists of a signal generator 11, a compensation circuit 12, and a driver 13 arranged in series with an electric circuit L1. Next to the driver 13 of the circuit L1, an electromagnet 7
and dynamics 14 are provided in series.
Then, the signal of the displacement sensor 8 is the dynamics 14
The signal is fed back to the input side of the compensation circuit 12 via the circuit L2.

During operation, the displacement sensor 8 detects the distance A between the sensor 8 and the casing, and the compensation circuit 12
outputs a control signal to the driver 13 such that the interval A follows the signal given from the signal generator 11 to control the magnetic force of the electromagnet 7. Therefore, the wafer is given a controlled movement other than rotation, giving it the optimum movement for applying the exposure agent.

That is, in FIG. 3, the rotational speed of the drive shaft 4 is ω, and the coordinates of the drive shaft 4 from the absolute coordinate system are:
Let it be (X1, Y1). When the signal generator 11 gives signals such as X1 = Rcos (φt) and Y1 = Rsin (φt), the drive shaft 4 itself rotates at a radius R and a rotation speed φ, and the rotation speed around the drive shaft 4 increases. A motion along a locus C that is a mixture of ω and revolution φ is applied to the wafer via the wafer holder. The motion locus C synthesized in this manner makes it possible to eliminate uneven coating of the exposure agent due to the difference in centrifugal force between the center and the outer periphery of the wafer, which could not be corrected by rotation by the drive shaft 4 alone.

FIG. 4 shows another embodiment of the present invention, in which the supporting means and a part of the control means are constituted by a known thrust magnetic bearing 9a and a radial magnetic bearing 9b, and the other parts are substantially similar to those shown in FIG. This is an example configured in the same way as . In this embodiment, the motor 3 is supported by the main body 1 in a non-contact manner, and dust generation due to vibration can be prevented, contributing to a dust-free environment.

[Effects of the Invention] Since the present invention is configured as described above, the motor itself is given an actively controlled displacement, and the wafer is given a movement other than its rotation, so that the center and outer periphery of the wafer can be separated. It is possible to eliminate uneven coating of the exposure agent due to the difference in centrifugal force between the two.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing one embodiment of the present invention, FIG. 2 is a control circuit diagram, FIG. 3 is a motion locus diagram given to the wafer, and FIG. 4 is a side view showing another embodiment of the present invention. FIG. 1... Spin coater main body, 3... Drive motor, 4... Drive shaft, 5... Motor casing, 6
...Coil spring, 7...Electromagnet, 8...Displacement sensor, 9a...Magnetic bearing for thrust, 9b...
... Radial magnetic bearing, 10... Control circuit.

Claims (1)

[Claims] 1. A spin coater for semiconductor wafers in which a wafer holder is attached to the end of a drive shaft of a drive motor, in which the casing of the motor is supported by a support means on the holder body, and a control means is provided for controlling displacement based on a signal from a displacement sensor. A spin coater characterized by: