JPS63140529A - Gap controller - Google Patents

Abstract

PURPOSE:To enable a distance between a mask and a wafer to be controlled either sufficiently long or minute by a method wherein, before the mask or the wafer is replaced, the shifting mechanism of a holding table is operated in accordance with the output of 1st sensor and, at the time of alignment, the mask and the wafer are aligned with each other with a predetermined gap in accordance with the outputs of the 1st sensor and 2nd sensor. CONSTITUTION:Before a wafer 4 and a mask 3 is replaced, a wafer table 10 is retreated with a certain speed by a shifting mechanism composed of a linear guide 8, a ball screw 7 and a DC motor 6. The stop position of the retreat is detected by putting the output of a limit sensor 21 into a CPU 18 through a parallel I/O 22. In the same way, the wafer table 10 is moved forward by a certain rotation of the DC motor 6. When the wafer table 10 comes close to a mask table 9 and enters the measurement range of a sensor 23 which detects the position of the wafer table 10, entry of the table 10 into the range is detected by the CPU 18 through a converter 24. After that, the alignment of the wafer table 10 is controlled in accordance with the output of the sensor 23.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a gap control device for setting a gap between a mask and a wafer 1 in an X-ray exposure apparatus that uses, for example, SOR as a light source.

(Prior art) In an X-ray exposure device that uses SOR as a light source,
During alignment, set the gap between the mask and wafer to several tens of
It must be kept as small as μm. On the other hand, when replacing a mask or a wafer, it is necessary to oxidize a sufficiently long distance for a gap of 10 μm. After replacing the mask or wafer, it is necessary to perform alignment again with high precision within a gap of several tens of micrometers.

In order to satisfy such requirements, it has been considered to use a plurality of elements having high resolution, such as piezoelectric elements, to control the gap between the mask and the wafer with high precision. However, when gap control is performed using a piezoelectric element or the like, although the resolution is high, the drive stroke is short, so there is a problem that it is difficult to replace the mass or wafer.

Although such a problem does not occur in a reduction projection exposure apparatus in which an optical system is interposed between a mask and a wafer, it becomes particularly important in an X-ray exposure apparatus in which a mask and a wafer are opposed to each other with a minute gap of several tens of micrometers.

(Problems to be Solved by the Invention) As described above, in X-ray exposure apparatuses and the like, there has been a problem in that when replacing masks or wafers, a sufficient distance cannot be maintained, making it difficult to replace them.

The present invention has been made in view of the above circumstances, and its purpose is to be able to keep the mask and wafer a sufficiently long distance apart even when exchanging the mask and wafer, and to control the alignment using minute gears. The purpose of this invention is to provide a gap control device that can perform the following steps.

[Structure of the Invention] (Means for Solving the Problems) In the gap control device of the present invention, a holding table that holds a mask or a wafer is driven with a long stroke, and when exchanging the mask or wafer, the holding table is movable. A first sensor detects the position of the holding table in the gap direction, a second sensor detects the gap between the mask and the wafer with high precision, and the gap between the mask and the wafer is controlled by the outputs of at least the first and second sensors. It is equipped with a holding table moving mechanism and a gap control circuit.

(Function) In the device configured as described above, when exchanging the mask or the wafer, the moving mechanism of the holding table is operated based on the output of the first sensor to separate the mask and the wafer by a sufficient distance. This allows easy replacement of masks or wafers. Furthermore, during alignment, the mask and wafer are aligned several tens of μm based on the outputs of the first and second sensors.
Positioning can be controlled at high speed and with high accuracy in the gap.

(Example) An example of the gap control device of the present invention will be described below with reference to the drawings.

Since the X-rays emitted from the SOR are emitted in the horizontal direction, it is advantageous for the X-ray exposure apparatus to have a vertical XY stage that moves the wafer up and down and left and right in a vertical plane. Also, when exchanging masks or wafers, the entire wafer side where the wafer is attached, or the entire mask side where the mask is attached, must be sufficiently long in the direction perpendicular to the vertical plane (Z direction) where the XY stage moves. It is necessary to move the distance (approximately 300 mm). At this time, the SOR on the mask side
The method of moving the wafer side is advantageous because the ports from the wafer side are connected.

After taking the above into consideration, the inventors adopted a vertical XY stage, and the entire wafer side, that is, the vertical
The entire stage was configured to move approximately 300 mm in the Z direction. Furthermore, the stage is very heavy, so
Consideration has been taken to prevent accidents such as contact occurring when the mask and wafer are brought close to each other by several tens of micrometers.

FIG. 1 is a schematic configuration diagram showing a first embodiment of a gap control device according to the present invention.

In FIG. 1, a movable base 2 on which an XY stage 5 is placed is moved by a DC motor 6, a ball screw 7, and a linear guide 8 provided on a fixed base 1, in the direction of the gap between a mask 3 and a wafer 4, which are disposed facing each other. will be moved to The linear guide 8 uses a ball-type rolling bearing with relatively low friction, and is of a preload type so that it can withstand the loads of the XY stage 5 and moving base 2. In addition, two rails were used, arranged on the left and right, and three linear guide bearings were arranged for each rail, so that the amount of deflection of the moving base was minimized.

Further, stoppers are provided at both ends of the stroke of the ball screw 7 for emergency protection.

The wafer 4 is attached to an XY stage 5 and moved in two vertical axes, and the mask 3 is attached to a mask stand 9, which is equipped with a piezo element (not shown) for slightly moving the mask 3 in the gap direction. (omitted) is provided.

Furthermore, three sensors 13a, 13b, and 13C are fixed to the mask stand 9 to measure the distance between the mask stand 9 and the wafer 4. Furthermore, three sensors 15a, 15b, and 15c are fixed to the pedestal 14 that fixes the mask stand 9 to the fixed base 1, for directly detecting the gap between the wafer 4 and the mask 3.

When replacing the wafer 4 or mask 3, the wafer stand 10 is connected to the linear guide 8, ball screw 7, and DC motor 6.
It moves backwards using a feed mechanism consisting of:

In that case, the DC motor 6 is controlled at a constant speed via the A/D converter 17, the CPU 1g, the D/A converter 19, and the servo circuit 20 based on the output of the tacho generator 16 attached to the motor shaft. .

The stop position during reverse movement is detected by inputting the output of the limit sensor 21 into the CPU 1g via the parallel 1022.

When the wafer table 10 is moved forward, the DC motor 6 is rotated at a constant speed in the same manner as when moving backward.

When the wafer stand 10 approaches the mask stand 9 and enters the measurement range of the sensor 23 that detects the position of the wafer stand 10, the CPUI 8 detects the entry via the A/D converter 24. Thereafter, the output of the sensor 23 is used to control the positioning of the wafer table 10. Positioning control is performed by sensor 23
The output of is inputted to the CPU 18, and the D/A converter 19,
The DC motor 6 is controlled via the servo circuit 20.

The measurement ranges of sensors 13 a, 13 b, and 13 c are narrower than the measurement range of sensor 23, and sensor 15
The measurement range of an 15b + 15c is sensor 13a
.

It is narrower than the measurement range of 13b and 13C.

Therefore, during positioning control, the sensors 13a, 13b, 13
The outputs of the C% sensors 15a, 15b, and 15c are all A/
D: l inverter 25a, 25b, 25C% 26a, 2
6b, 26c, to the CPU 18, and its sensors 13a, 13b, 13cs sensors 15a, 15b,
The wafer table 10 is controlled to the optimum position based on the output of the wafer 15c.

Next, FIG. 2 shows a schematic diagram showing a second embodiment of the gap control device according to the present invention. Components that are the same as or correspond to those in FIG. 1 are given the same reference numerals, and their explanations will be omitted.

The position of the stage 30 is detected by a gap sensor 23 and a photoelectric sensor 5.
Perform with W32. The measurement range of the gap sensor 23 is 2.5
It is short, about mm, and the stroke of stage 30 is 300 mm.
Since the wafer 4 is long (mm), when the wafer 4 approaches the mask 3, the position is determined by the gap sensor 23, and in the range that cannot be measured by the gap sensor 23, a plurality of photoelectric SWs 32 are installed to detect the position of the stage 30.

The photoelectric SW32 is installed on the fixed base 1, and the movable base 2
The position of the stage 30 is detected by detecting the end of a light shielding plate (not shown) attached to the side surface. The detection method is an absolute value method. In the absolute value method, for example, it is OFF in the FWD direction from the FWD detection position, and OFF at the FWD detection position.
It changes from FF to ON, and becomes ON in the BWD direction from the FWD detection position.

Three sets of photoelectric SW32 and light shielding plates are provided, FWD position, BWD position
Detect positions and intermediate positions.

The light shielding plate is made of aluminum to facilitate adjustment through processing.

The photoelectric SW32 has a built-in amplifier and can be easily adjusted using the built-in LED. In addition, the signal line of the photoelectric switch is not an optical fiber, but a normal electric wire (cable), which facilitates assembly and adjustment.

A micro 5W33 (mechanical) is provided to operate outside the photoelectric 5W32. Micro SW33 is FW
Two are used on both the D side and the BWD side so that even if one fails, the other will operate. Micro SW33 is CP
The SW of the power amplifier of the DC motor 6 is directly turned OFF without being managed in U18. This is a safety measure in case something goes wrong with software management.

The positioning of the stage 30 is performed using the output of the gap sensor 23 that detects the position of the tip of the stage 30. However, what is really required is the positional accuracy in the Z direction (gap direction) of the XY stage 5 portion on which the wafer 4 is placed. Therefore, the Z-direction position of the XY stage 5 is measured by three gap sensors 13, and the three gap sensors 13
Positioning control is performed using the output of the gap sensor 23 of the stage 30 so that all three outputs fall within the allowable value. Finally, the process is performed while also observing the signal output of the Z sensor of the alignment optical system. In order to perform flexible control as described above, all outputs of each sensor are connected to the D/A converter 34, A/D converter 35, P P I 36 (P
rograa+able PeripheralInt
erf'ace Adapter) to the CPU 1g and control it using software.

The driving sequence of the stage 30 is as follows.

■Make sure you are at the initial setting stage 30 or BWD side photoelectric 5W32a position. If it is not at the position of the BWD side photoelectric 5W32a, advance to that position. The drive is performed under constant speed control and stopped by a signal from the BWD side photoelectric 5W32a.

■Move forward at a constant speed.

Consider trapezoidal speed drive, etc.

■The center photoelectric SW32b detects the deceleration start position and starts deceleration.

■Switch from speed control to positioning control using FWD side photoelectric 5W32c.

■Using the output of the gap sensor 23 of the stage 30,
Performs positioning control.

(3) The three gap sensors of the XY stage 5 detect the position of the XY stage in the Z direction, and positioning control is performed using the output of the gap sensor of the Z stage so that the position is within 30 μm±10 μm.

■Retreat to the BWD side photoelectric switch.

By repeating the above sequence, the gap between the mask and wafer during mask or wafer exchange and exposure can be managed with high precision.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to perform a long stroke drive when replacing a mask or a wafer, and it is also possible to accurately manage the gap between the mask and the wafer during alignment.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing a first embodiment of a gap control device of the present invention, and FIG. 2 is a schematic block diagram showing a second embodiment of the gap control device of the present invention. 1... Fixed base 2... Moving base 3... Mask 4... Wafer 5... XY stage 6... DC motor 7...Ball screw 8...Linear guide 9...Mask stand 10...Wafer stand 13a, 13b, 13c------ -Sensors 15a, 15b, 15c------
- Center 18... CPU 21... Lit sensor 23... Sensor 30... Stage 32... Photoelectric switch

Claims (1)

[Scope of Claim] A gap control device for controlling a gap between a mask and a wafer, comprising: a first holding table for holding and fixing the mask; a second holding table for holding and fixing the wafer; a moving mechanism that moves at least one of the two holding stands in the gap direction; a first sensor that detects a position in the gap direction of at least the first or second holding stand movable by the moving mechanism; and the mask. and a second sensor that detects the gap between the wafers, and a gap control circuit that operates the moving mechanism based on the outputs of the first and second sensors to maintain the gap at a predetermined value. Features a gap control device.