JPH02115844A - Washing device for photomask - Google Patents

Abstract

PURPOSE:To maintain the constant washing state of masks and to save the volume of the ultra-pure water to be used by measuring the specific resistance of the ultra-pure water overflowing from a rinsing tank and washing the masks until a prescribed specific resistance value is attained. CONSTITUTION:The masks 2 to be washed are set in a cassette 1 and the cassette is put into the rinsing tank 3 filled with the ultra-pure water. The ultra- pure water is supplied from a water feed pipe 5 into the tank and the masks are rinsed. The specific resistance of the water overflowing from the tank 3 is then measured by a sensor 6 and is displayed on a specific resistance meter 7. A control section 8 transmits the end of the rinsing and transmits the same to a cassette 1 moving mechanism so as to move the cassette into the next tank when the resistance value above the set value is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a photomask cleaning apparatus used in the field of semiconductor manufacturing.

(Prior Art) In a conventional cleaning apparatus of this kind, a photomask (hereinafter abbreviated as mask) is cleaned with a cleaning liquid, for example, a mixture of sulfuric acid and hydrogen peroxide, and then rinsed with water. The cleaning method is a rapid water supply and drainage tank (hereinafter referred to as a QDR tank).

Repeat the shower, water supply, and drain operations a predetermined number of times.

After the washing was completed, the mask was moved to the next washing tank and left to stand for an appropriate period of time to dry.

(Problems to be Solved by the Invention) However, in the configuration of the rinsing tank of the conventional cleaning device, the final rinsing state is set only by time.

Therefore, regardless of the number of masks to be washed, the washing time remains constant, resulting in insufficient washing or wasteful use of ultrapure water.

The present invention solves the above-mentioned conventional problems.

It is an object of the present invention to provide a mask cleaning device that can keep the water washing condition constant and save the amount of ultrapure water used.

(Means for Solving the Problems) In order to achieve the above object, the cleaning device of the present invention includes a sensor for measuring the specific resistance of ultrapure water overflowing from a washing tank, and a sensor based on a detection signal of the sensor. It is characterized by having a control function to continue cleaning until the ultrapure water reaches a predetermined resistivity value.

(Function) With this configuration, it is possible to know the end point of water washing, so that the cleaning state of one surface can always be kept constant regardless of the number of masks to be cleaned. Also, there is no need to use ultrapure water unnecessarily.

(Example) An example of the present invention will be described below with reference to one drawing. FIG. 1 is a schematic diagram of a rinsing tank of a mask cleaning device according to the present invention. In FIG.

1 is a cassette, 2 is a mask, 3 is a washing tank, 4 is a bottom plate, 5
is a water supply pipe, 6 is a resistivity measurement sensor, 7 is a resistivity meter,
8 is a control section, and 9 is a wiring from the control section to the sample moving mechanism. The operation of the washing tank of this embodiment configured as described above will be described below. A mask 2 to be washed is set in a dedicated cassette 1 and placed on a bottom plate 4 in a washing tank 3, which is always filled with ultrapure water. Also, the bottom plate 4
has numerous holes so that water can be supplied from the bottom.

By placing the cassette 1 in the water washing tank 3, the water supply pipe 5
A larger amount of ultrapure water is supplied into the tank to perform water washing.

As shown in FIG. 1, ultrapure water overflows from the washing tank 3. The resistivity of this overflowing water is detected by a sensor 6 and displayed on a resistivity meter 7. A specific resistance value is set in the control unit 8 in advance.

When the specific resistance value exceeds the set value, the completion of water washing is transmitted to the sample moving mechanism via the wiring 9, and a signal for the next operation is sent. In the case of a non-automatic device, an alarm etc. will be used to notify the end of washing.

Fig. 2 shows an enlarged view of the washing tank.The sensor 6 is the sensing part 1.
0 is covered with a mesh-like cover to prevent damage to the sensor, and the sensor is horizontally moved so that water comes into sufficient contact with the detection part inside and is constantly replaced during measurements. The sensor is installed at the top of the washing tank 3, as shown in Figure 2, so that only the sensing part is always in contact with the overflowing pure water. Furthermore, it should be placed a little further away from the tank wall so that water can pass through the sensing part sufficiently.

According to our experiments, only one mask was immersed in the cleaning solution, and then the QDR operation was repeated five times.

After that, when washing is performed by leaving it still, the resistivity has already increased to such an extent that washing with water is not necessary, and it can be immediately moved to the next tank. However, if the number of masks is large (1, for example 5), the specific resistance of the pure water in the washing tank will be 1.
It takes 15 to 20 minutes of water washing to achieve the same level as with a sheet. In the conventional apparatus, the washing time is determined to be 20 minutes or more, but in the washing apparatus configured as in the present invention, the standing washing time is automatically determined according to the number of masks.

In the cleaning device described above, the QDR tank and the washing tank according to the present invention are separate, but in another embodiment, a resistivity measuring sensor is attached to the QDR tank. The installation location may be similar to that shown in Figure 2 in the QDR tank. When attached to a QDR tank, the number of QDRs is automatically determined according to the number of masks, and the same effect as when attached to a stationary rinsing tank can be obtained.

(Effects of the Invention) As described above, according to the present invention, by measuring the specific resistance of ultrapure water in the QDR tank or the washing tank, the number of QDRs is controlled by the counter and the standing time in the washing tank is controlled by the timer. be able to. In addition, water washing conditions can be automatically obtained depending on the number of masks to be washed, and insufficient washing or wasteful use of ultrapure water can be suppressed, thereby improving throughput and reducing costs in the washing process. Furthermore, even when used for cleaning before resist coating, a plate with a uniform mask surface condition can be stably obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic view of the rinsing tank and its surroundings in an embodiment of the present invention, and FIG. 2 is an enlarged view of the rinsing tank. 1...Cassette, 2...Mask, 3...
・Washing tank, 4...bottom plate, 5...water supply pipe, 6...
...Sensor 7...Resistivity meter, 8...Control unit,
9...Wiring from the control section, IO...sensing section of the sensor. Patent applicant: Matsushita Electronics Co., Ltd.

Claims (1)

[Claims] A photo sensor having a sensor for measuring the resistivity of ultrapure water overflowing from a washing tank, and a control function for continuing washing until the ultrapure water reaches a predetermined resistivity value based on the detection signal of the sensor. Mask cleaning equipment.