JPS59111610A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To improve the reproducibility of the scale of a needle bulb and to improve operativity by providing a bias adjusting device at the output of a differential pressure transformer, adding both outputs, and operating a servomechanism so that the addition output is ceased. CONSTITUTION:The adder 13 is connected to the differential pressure transformer 8 and bias adjusting device 12. A motor 6 is connected to the output terminal of this adder 13 through an amplifier 7. The adder 13 adds the outputs of the differential pressure transformer 8 and adjusting device 12 together to operate the servomechanism so that the output of the adder is ceased. Therefore, the adjusting device 12 is adjusted to perform through focusing. This is carried out electrically, so automation by computer control is extremely easy to obtain good reproducibility and also to improve the reliability and operativity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an automatic focusing device that electrically adjusts the distance between an objective lens and an objective lens, and particularly to an automatic focusing device suitable for finding a positive focus position. Regarding.

[Prior art]

A conventional automatic focusing device has a configuration as shown in FIG. FIG. 1 shows an autofocus configuration in a reduction projection exposure apparatus. That is, the air supplied from the pressure source 11 is branched into three directions, and the differential pressure converter 8
is supplied to one input of the needle valve 19 and the other is supplied to one input of the needle valve 19.
The air is supplied to the air micro 2 via the air micro 2, and is released into the atmosphere from the gap between the air micro 2 and the wafer 3. Therefore, the pressure within the air micro is the other input to the differential pressure converter.

At this time, if there is a pressure difference between the two inputs of the differential pressure converter, an electrical output commensurate with the magnitude of the difference can be extracted from the differential pressure converter.

The output is amplified by the amplifier 7 to drive the motor 6,
By moving the wedge 5 in the direction of arrow A, the wafer support 4 is moved in the direction of arrow B to change the distance between the air micro 2 and the wafer 3. At this time, the position servo mechanism is used in which the direction of change in the pressure changes in the direction that eliminates the input difference of the differential pressure converter, so even if the thickness of the wafer changes or there are irregularities, the gap between the wafer 3 and the lens 1 Immediate separation can be kept constant.

In such an apparatus, the position of the wafer 3 is usually fixed so that the immediate separation between the reticle 14 and the lens 1 is fixed as shown in FIG. It is necessary to find a suitable position so that it can be seen.

As a means of achieving this, as shown in Fig. 4, the wafer is changed stepwise in the optical axis direction, and the exposure is repeated from 1 to 25 as shown in Fig. 5, and the position with the highest resolution is placed at the positive focal point by developing. As a result, a method is used to adjust the height of the ueno. Further, as a means for changing the height of the wafer in the optical axis direction, a method is used in which the height of the wafer is changed while recording the scale of the needle valve 9 or 10 shown in FIG.

This conventional method changes the wafer position by changing air pressure, which requires a large apparatus, and is mechanically performed, making automation difficult.

Also, even if you adjust to the scale with the highest resolution, the reproducibility is poor due to backlash due to the nature of the needle valve.
There were other drawbacks.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic focusing device that has good reproducibility of the distance to the scale of a needle valve and can improve productivity.

[Summary of the invention]

The present invention provides a bias regulator at the output of the differential pressure converter,
The purpose is to improve reproducibility and operability by adding the two using an adder and using a servo mechanism so that the output of the adder becomes zero.

[Embodiments of the invention]

Examples of the present invention will be described below.

FIG. 2 shows an embodiment of the invention.

In the figure, the differential pressure converter 8 and bias regulator 12 include:
An adder 13 is connected. A motor 6 is connected to the output end of the adder 13 via an amplifier 7.

In the conventional example shown in FIG. 1, the servo mechanism operates so that the output of the differential pressure converter is always zero, so the height of the wafer can be changed by adjusting the needle valve 9 or 10. can. In the embodiment shown in FIG. 2, a bias adjuster 12 is provided at the output of the differential pressure converter 8, and an adder 13 adds the two, thereby causing a servo mechanism so that the output of the adder becomes 0. It is.

Therefore, according to the present embodiment, the bias adjuster 12
Full through focus can be achieved by adjusting the . That is, since it can be carried out electrically, automation by computer control is extremely easy, and since it is carried out electrically, the reproducibility is good and it is possible to improve reliability and operability.

〔Effect of the invention〕

As described above, according to the present invention, the reproducibility of instant release with respect to the scale of the needle valve is good, and the operability can be improved.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a conventional autofocus device, Fig. 2 is a circuit diagram showing an embodiment of the present invention, Fig. 3 is a diagram showing the relative positional relationship between a reticle original image, a lens, and a wafer, and Fig. 4 is a conventional autofocus device. A diagram showing the scale of the needle valve and the position of the wafer in the device,
FIG. 5 is a diagram showing the state of chips exposed on a wafer. 7...Amplifier, 8...Differential pressure converter, 12...Bias adjustment TJMI 4th m ÷5m 43-

Claims (1)

[Claims] 1. The back pressure and reference pressure of the air micro in the air micro mechanism configured between the Ueno lens and the objective lens of the reduction projection fog light device are respectively supplied to the two inputs of the differential pressure converter, and the differential pressure between the two is In an automatic focusing device that controls the distance between the wafer and the objective lens by using the output of the differential pressure converter generated by the wafer as a drive signal for the vertical mechanism of the wafer support stand that supports the wafer, the differential pressure converter An automatic focusing device characterized in that the distance between the lens and the objective lens is controlled by adding a bias voltage to the output voltage from the device and changing the bias voltage from the outside.