JPH0548331U - Reduction projection exposure system - Google Patents

Abstract

(57) [Summary] [Structure] The vacuum source pressure measuring pressure sensor 1 is connected to a vacuum source and outputs an electric signal corresponding to the vacuum pressure. Similarly, the pressure sensor 2 for measuring the pressure of the measuring portion outputs an electric signal corresponding to the vacuum pressure to measure the pressure of the adsorbed portion. These are selected by the selector 3 and the A / D
It is taken into the CPU through the converter 4. The CPU arithmetically processes the measurement data at each point and determines whether or not an accurate suction operation is performed. [Effect] By knowing the vacuum source pressure and the accurate relative pressure between the vacuum source pressure and the measurement portion pressure, it is possible to prevent an accident of the device due to a disturbance such as a vacuum source pressure fluctuation or a vacuum leak.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a reduction projection exposure apparatus that manufactures VLSI, and more particularly to a reduction projection exposure apparatus that achieves high reliability by performing suction and fixation of a wafer and a reticle by vacuum and accurately determining the suction state.

[0002]

[Prior Art]

 The means for determining the adsorption state of the reticle and the wafer is determined by the ON / OFF output of the vacuum pressure sensor. Moreover, there was no pressure sensor for measuring the vacuum source pressure.

[0003]

[Problems to be solved by the device]

 The above-mentioned prior art malfunctions due to disturbances such as fluctuations in the vacuum source pressure, vacuum pressure reduction due to vacuum leakage from piping, etc., and temporary vacuum pressure reduction until adsorption of the object to be adsorbed caused by the adsorption operation. There was a possibility. For example, the vacuum pressure sensor outputs an OFF signal even though the reticle is actually adsorbed, so it is erroneously determined that there is no reticle, the reticle is double-transported, and the reticle is damaged. There was a problem that could lead to a serious accident.

In order to eliminate these drawbacks, the present invention has an object to provide a method for detecting a disturbance as described above and determining a suction state with a sufficient margin.

[0005]

[Means for Solving the Problems]

 In order to achieve the above object, a pressure sensor for measuring the vacuum source pressure is added.

In addition, from the conventional pressure sensor for measuring the pressure of the measuring unit, which is a fixed detection threshold value of ON / OFF, the analog value of the pressure sensor is digitized using an A / D converter, and the floating threshold value is detected. The judgment method is based on.

Further, software for detecting disturbance vacuum pressure fluctuations and performing appropriate correction is added.

[0008]

[Action]

 The operation will be described with reference to FIGS. 1 and 2.

The vacuum source pressure measuring pressure sensor 1 is connected to a vacuum source and outputs an electric signal according to the vacuum pressure. The pressure sensor 2 for measuring the pressure of the measuring section also outputs an electric signal corresponding to the vacuum pressure.

The desired sensor output is selected by the selector 3 and one selected signal is digitized by the A / D converter 4 and taken into the CPU. The valve 8 is a valve for transmitting or not transmitting the vacuum pressure of the vacuum source to the suction table of the wafer 6 and the reticle 7. The CPU5 determines the vacuum pressure state of each part based on the digitally converted vacuum source pressure, and the vacuum source pressure does not rise, whether it is in the adsorption state or the adsorption release state released to the atmosphere, and the device may malfunction. Judge whether there is a nature. If the vacuum source pressure drop is within the normal operation guarantee range of the device, an appropriate threshold value can be set by software, and it can be used to judge whether adsorption is in progress or desorption is in progress, thus preventing malfunctions. ..

[0011]

【Example】

 An embodiment of the present invention will be described below with reference to FIGS.

Vacuum source pressure measuring pressure sensor 1, measuring section pressure measuring pressure sensor 2, selector for switching the pressure sensor 3, A / D converter 4 for converting the selected analog signal to digital, CPU 5, It is composed of a wafer to be attracted 6, a reticle 7 of the same to be attracted, and a valve 8 for controlling adsorption ON / OFF.

Next, the operation will be described.

Objects to be adsorbed by vacuum adsorption in the reduction projection exposure apparatus are mainly the wafer 6 and the reticule 7. The wafer and reticle are appropriately transported in the reduction projection exposure apparatus and positioned with high precision and high speed. The vacuum fixing method is often used to fix the wafer after transfer and positioning, and the pressure sensor in each part confirms whether the wafer and reticle are in that position.

Of the pressure sensors 2 for measuring the pressure of a large number of measuring units, which are focused on the adsorption of the reticle, the pressure measuring sensor for measuring the pressure of the reticle will be focused on.

First, a conventional technique will be described with reference to FIGS. (However, the pressure sensor 1 for measuring the vacuum source pressure is not included in the conventional technique.) FIG. 3 is a diagram during normal operation in the conventional ON / OFF determination method of the adsorption state determination. First, when the adsorption ON / OFF valve 8 is OFF, the reticle pressure measuring pressure sensor 2 is at the atmospheric level. When this valve is turned ON, the original pressure of the vacuum is connected to the adsorption table through the pipe. If there is a reticle 7, adsorption is performed and the vacuum pressure at the measurement point rises, so the reticle pressure measurement pressure sensor 2 Output becomes the vacuum level. If there is no reticle, the output of this pressure sensor will be atmospheric level. The output of this sensor is binarized by the binarization control circuit 9 to check whether it is in the adsorption state. The threshold value that determines this binarization is determined in advance by an electric circuit, and a1 in FIG. 3 indicates the margin of normal operation for confirmation of adsorption OFF. In addition, the normal operation margin of confirmation when the valve is ON and during adsorption is a2 in FIG.

Next, FIG. 3 will be used to explain a state in which the tolerance is reduced due to the vacuum source pressure fluctuation (vacuum source pressure drop) in the conventional adsorption state determination. When the original pressure is reduced and the degree of vacuum is lowered, turning on the valve 8 causes the output of the reticle pressure measuring pressure sensor, which measures the reticle pressure, to approach the threshold value. The degree a2 decreases. When the valve 8 is turned on in such a state and the value of the pressure sensor 2 for measuring the pressure of the measurement portion is read for confirmation, it may be a little unadsorbed, that is, the reticle is erroneously determined to be absent. , There is a possibility of causing a serious accident such as damage to the reticle due to double transportation of the reticle.

An embodiment of the present invention for preventing this will be described with reference to FIGS. 1, 2 and 4.

In the present invention, a pressure sensor 1 for measuring vacuum source pressure is added. Furthermore, an A / D converter 4 for highly accurately converting the analog signal of each vacuum pressure sensor into a digital signal was added. This makes it possible to detect the next accurate value.

1. Vacuum source pressure and its fluctuation, 2. 2. Pressure of the measured part and its fluctuation, Relative pressure between the vacuum source pressure and the measured part.

Thus, if the vacuum source pressure is abnormal, it can be directly determined to be abnormal, and the device does not malfunction.

Further, a floating threshold value setting system is adopted in which the adsorption ON / OFF determination threshold value can be sequentially set by software. As a result, the tolerances a3 and a4 are secured even if the vacuum source pressure changes. These a3 and a4 are set as current threshold values by constantly measuring the vacuum pressure of each part and performing arithmetic processing of threshold value = (a7 + a6) / 2 ... (Equation 1) by the CPU. However, the range of fluctuation of the source pressure is not infinite, and if it exceeds a certain allowable value, the source pressure becomes abnormal and the device is stopped and an error is displayed.

As described above, according to the present embodiment, the erroneous determination of the presence or absence of the reticle due to the fluctuation of the vacuum source pressure, the damage of the pipe, the disconnection of the pipe, etc. is eliminated, and the serious accident such as the damage of the reticle is prevented. The effect is to prevent.

[0024]

[Effect of the device]

 Since the present invention is configured as described above, it has the following effects.

Since the vacuum source pressure can be measured, the accurate relative pressure with the vacuum pressure of the measuring part can be known, and an accurate threshold value for determining whether adsorption or desorption is in progress can be set, and thereby the influence of disturbance The device does not malfunction because it can be judged with a margin that is not affected by it. Also, if the vacuum source pressure is abnormal, it can be directly judged as abnormal, and the device will not malfunction. In addition, the erroneous determination of the presence or absence of the reticle is eliminated, and a serious accident such as damage due to double transportation of the reticle can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of an embodiment of the present invention.

FIG. 3 is a diagram of a conventional ON / OFF determination method for determination of a suction state.

FIG. 4 is a diagram showing a state in which the judgment margin is improved in the floating threshold value setting method according to the embodiment of the present invention.

FIG. 5 is a block diagram of the prior art.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pressure sensor for measuring vacuum source pressure, 2 ... Pressure sensor for measuring measuring section pressure, 3 ... Selector, 4 ... A / D converter, 5 ...
CPU, 6 ... Wafer, 7 ... Reticle, 8 ... Vacuum valve, 9 ... Binary control circuit.

Claims (1)

[Scope of utility model registration request] 1. A rough alignment mark (pre-alignment mark) for a wafer, which has a function of reducing an original image pattern on a reticle through a reduction lens and baking it on a wafer with high accuracy, and which is baked on a wafer in a previous process. Function to accurately transfer the wafer to the exposure stage after completion of rough alignment, and to precisely detect the position of the wafer transferred to the exposure stage and to align the original pattern on the reticle with the on-wafer pattern. And has a function of fixing the reticle original image and the wafer by vacuum suction and performing suction confirmation by a vacuum pressure sensor, and is capable of measuring the vacuum source pressure, a vacuum pressure sensor capable of measuring the vacuum pressure of the measured portion, or With multiple vacuum pressure sensors and means for knowing the accurate relative pressure between the vacuum source pressure and the measurement section pressure, it is possible to A function that allows determination of the adsorption state with, CPU for controlling them, the controller, a reduction projection exposure apparatus, characterized in that resulting from the driver.