JPS62286231A - Cleaning apparatus - Google Patents

Abstract

PURPOSE:To enable fine pollutants to be removed by a method wherein an oscillating plate made of high melting point metal in direct contact with cleaning polution is arranged on the bottom or the sidewalls of a cleaning vessel while high frequency oscillating elements are mounted on outer surface of the oscillating plate. CONSTITUTION:A cassette 17 containing multiple silicon wafers 16 as elements to be processed is immersed in a cleaning solution 14 in a cleaning vessel 3 and then when multiple hexagonal tantalum-made oscillating elements 10 are impressed with high frequency from an oscillator 13 through a cable 12 and a lead plate 11 while feeding fresh cleaning solution from a feeder pipe 15 to the cleaning vessel 3, a thin tantalum-oscillating plate 6 is resonantly oscillated to generate high frequency. Through these procedures, the acceleration in the cleaning solution 14 in contact with the oscillating plate 6 is proportional to a suare of frequency to scribe the surface of respective wafers in the cassette 17 at the acceleration two hundred fifth thousand times of gravity so that extremely fine pollutants adhering to the surface of respective wafers 16 may be removed.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a cleaning device, and is particularly suitable for cleaning semiconductor wafers, metal magnetic disks, etc. that require high cleanliness. [Background Art Related to Cleaning Apparatus] A cleaning process is one of the manufacturing processes of semiconductor devices.

This cleaning uses the etching action of the semiconductor wafer 1 by the cleaning solution to: 1) remove the contaminant layer on the wafer surface to create a clean surface, 2) finish the wafer surface smooth, and 2) etch the wafer to a predetermined thickness and shape. , etc. is carried out to achieve the following objectives.

By the way, conventionally, semiconductor wafers have been cleaned by using an apparatus containing a heated cleaning liquid in a cleaning tank, and by immersing a plurality of wafers housed in a cassette in the cleaning liquid. There is. However, when such a cleaning apparatus is used, it is difficult to obtain a highly clean wafer because many of the contaminants on the wafer surface are chemically insoluble in the cleaning liquid. Furthermore, the lifetime of the cleaning liquid is short, and the cleaning performance becomes unstable due to the generation of numerous bubbles. Furthermore, there is a problem in that cleaning liquid or the like stagnates on the contact surface between the cassette and the wafer, deteriorating the cleaning effect of the wafer near the contact surface.

For this reason, a stainless steel vibrating ring with a thickness of 2 to 3 mm is placed at the bottom of the cleaning tank containing the cleaning liquid so as to be in direct contact with the cleaning liquid, and a vibration frequency of 28kHz to 28kHz is placed on the vibrating plate.
A cleaning device having a structure equipped with a vibrator to which a frequency of 00 kHz is supplied has been developed. According to such a cleaning device, the above-mentioned problems can be solved. However, the cleaning apparatus described above can only remove contaminants of several micrometers or more, and it is difficult to remove even finer contaminants of about 0.3 micrometers. Further, when ultrasonic waves are applied to the cleaning liquid via a vibrator and a diaphragm that vibrate at the above-mentioned frequency, there is a problem in that cavitation causes damage to the wafer surface. Furthermore, there is a problem in that contaminants gather on the wafer surface due to the dispersion and aggregation effects that are characteristic of ultrasonic waves.

[Problems to be Solved by the Invention] The present invention has been made to solve the above-mentioned conventional problems.
The object of the present invention is to provide a cleaning device that can effectively remove even minute contaminants before and after the cleaning device and prevent damage to the object to be treated due to cavitation.

[Means and effects for solving the problem] The inventor
The high melting point metal has excellent chemical resistance, high tensile strength, and excellent mechanical strength, allowing it to be made thinner than the stainless steel used in conventional diaphragms.In addition, it has excellent vibration conversion efficiency in relation to the vibrator. By focusing on the high melting point metal and forming a diaphragm with the thickness of the diaphragm within a predetermined range, the vibration from the oscillator to which a high frequency of 600 to 1000 kHz is applied can be It is possible to apply ultrasonic waves of the same frequency to the cleaning liquid in the cleaning tank with good resonance, and it is possible to effectively remove fine contaminants (around 0.3 μm) attached to the surface of the workpiece in the cleaning liquid. discovered a cleaning device that can prevent damage to the surface of a processed object due to cavitation.

That is, the present invention includes a cleaning tank containing a cleaning liquid, and a diaphragm having a thickness of 0.1 to 0.5 mm made of a high-melting point metal and placed on the bottom or side wall of the cleaning tank so as to be in direct contact with the cleaning liquid. is attached to the outer surface of this diaphragm, and has a diameter of 600 to 10
This cleaning device is characterized by comprising a vibrator that vibrates at a high frequency of 00 kHz.

Examples of high melting point metals for forming the diaphragm include tantalum, molybdenum, titanium, tungsten, and the like. In particular, tantalum is effective because it has superior high tensile strength compared to other high-melting point metals and has high vibration conversion efficiency in relation to the vibrator.

The reason for limiting the thickness of the perturbation plate is that the thickness is 0.1
This is because if the thickness is less than 1.5 mm, the strength will not be maintained, whereas if the thickness exceeds 1.5 mm, the resonance efficiency with the vibrator that vibrates in the frequency range will decrease, and the vibration will be easily damped. A more preferable thickness of the diaphragm is 0.2-0.
It is 3M.

The reason for limiting the high frequency value given to the above vibrator is 8
If the frequency is less than 100kHz, it will not be possible to effectively remove minute contaminants attached to the surface of the workpiece;
This is because if the frequency exceeds 00 kHz, the resonance efficiency of the diaphragm decreases due to the thickness of the diaphragm, and vibrations become more likely to be damped.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 and 2.

1 in the figure is a base having a rectangular ring-shaped flange 2 on its upper part. A cleaning tank 3 made of polypropylene, for example, is installed on the flange 2 of the base 1. This cleaning tank 3 includes large and small rectangular cylinder portions 48 arranged symmetrically.
4b, and a rectangular ring plate 5 which is integrally provided at the lower part between these cylindrical parts 4a and 4b and comes into contact with the flange 2 of the base 1. Further, there is a thickness of, for example, 0.0 mm between the top surface of the base 1 and the bottom surface of the cleaning tank 3. Two rectangular tantalum diaphragms 6 are arranged. The cleaning tank 3 is fixed to the base 1 by a plurality of bolts 7 inserted into the ring plate 5, the diaphragm 6, and the flange 2, and nuts 8 screwed onto these bolts 7. , the peripheral edge of the diaphragm 6 is clamped and fixed by the ring plate 5 and the flange 2. Note that gaskets 9a and 9b are interposed between the diaphragm 6 and the flange 2 and between the diaphragm 6 and the ring plate 5, respectively, for liquid-tightly fixing the cleaning tank 3 to the base 1.

On the surface of the diaphragm 6 on the base 1 side, as shown in FIG. 2, for example, 14 hexagonal vibrators 10 are arranged and attached in close proximity to each other. These vibrators 10 are connected via a lead plate 11 and a cable 12 to an oscillator 13 that oscillates a high frequency of, for example, 1l100.

a small-diameter cylindrical portion 4 whose bottom is the vibration plate 6 of the cleaning tank 3;
A cleaning liquid 14 made of, for example, hydrogen peroxide, ammonia, and ultrapure water is contained in the chamber b. The small diameter cylindrical portion 4
A plurality of notches are formed at the upper end of b to allow the cleaning liquid to overflow. Further, the small diameter cylindrical portion 4b
A cleaning liquid supply pipe 15 inserted through the large-diameter cylindrical portion 4a is connected to the side wall of the cylindrical portion 4b. A discharge pipe (not shown) is connected to discharge the cleaning liquid to the outside through the annular space between each cylinder portion 4a, 4b.

According to such a configuration, the cassette 17 containing a plurality of silicon wafers 16 as objects to be processed is transferred to the cleaning tank 3.
After being immersed in the cleaning liquid 14 in the tank, while supplying fresh cleaning liquid from the supply pipe 15 to the cleaning tank 3, an 800 kHz signal is transmitted from the oscillator 13 to a plurality of hexagonal tantalum vibrators 10 through the cable 12 and lead plate 11. When a high frequency wave is applied, the thin tantalum vibration ring 6 to which each diaphragm 10 is attached resonates and vibrates, generating a high frequency wave of 800 kHz similar to that described above. As a result, the acceleration within the cleaning liquid 14 that comes into contact with the diaphragm 6 is proportional to the square of the frequency.
The surface of each wafer 16 in the cassette 17 is scribed at an acceleration of approximately 2.5×10 5 G, which is 250,000 times the gravity. As a result, even very fine contaminants of around 0.3 μm attached to the surface of each wafer 16 can be removed, so that the surface of each wafer 16 can be highly cleaned. Furthermore, since scribing on each wafer 16 by the acceleration is performed over the entire area including the vicinity of the contact portion with the cassette 17, the entire wafer 16 can be uniformly cleaned.

Furthermore, since the frequency of 800 kHz generated by the diaphragm 10 does not cause cavitation in the cleaning liquid 14, damage to the nine surfaces of each wafer housed in the cassette 17 can be prevented.

Furthermore, if the vibrators 10 have a hexagonal shape and are arranged and attached close to each other on the tantalum diaphragm 6, the efficiency of vibration conversion from each vibrator 10 to the diaphragm 6 can be increased. This makes it possible to further effectively remove contaminants from the surface of the wafer 16.

In the above embodiment, the cleaning tank has a double cylindrical shape, but for example, a ring-shaped flange is attached to the lower end of the cylindrical part, which is the main body of the cleaning tank, and a dish-shaped container is attached to the upper part to receive the overflowing cleaning liquid. It is also possible to have a structure in which

In the above embodiments, the cleaning tank is made of polypropylene, but it is not limited thereto. For example, it may be formed of stainless steel lined with fluororesin or ceramics such as alumina.

In the above embodiment, the diaphragm was provided at the bottom of the cleaning tank, but the diaphragm may be provided at the side wall of the cleaning tank.

In the above embodiment, a hexagonal vibrator is used, but the vibrator is not limited to this, and other shapes such as a square or a triangle may also be used. Of course, the number of sheets is not limited to 14 either.

In the above example, a cleaning solution consisting of hydrogen peroxide, ammonia and ultrapure water was used.
Other cleaning solutions may be used, such as those consisting of ultrapure water.

In the above embodiments, an example was explained in which the present invention was applied to cleaning at the wafer stage, but the present invention can be similarly applied to the process of forming elements on the wafer surface. In addition to silicon wafers, we also offer ■-■ group compound semiconductor wafers, A, f? This product can also be applied to cleaning metal magnetic disks such as the following.

[Effects of the Invention] As detailed above, the cleaning apparatus of the present invention can effectively remove even minute contaminants of around 0.3 μm attached to the surface of a workpiece such as a wafer, and moreover, It has remarkable effects such as being able to prevent damage caused by cavitation to the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the material.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a cleaning device showing an embodiment of the present invention, and FIG. 2 is a plan view showing the shape and arrangement of vibrators in the cleaning device of FIG. DESCRIPTION OF SYMBOLS 1... Base, 3... Cleaning tank, 6... Tantalum diaphragm, 10... Vibrator, 13... Oscillator, 14...
-Cleaning liquid, 16... silicon wafer, 17... cassette. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2

Claims (1)

[Claims] A cleaning tank containing a cleaning solution, a diaphragm with a thickness of 0.1 to 0.5 mm made of a high-melting point metal and placed on the bottom or side wall of the cleaning tank so as to be in direct contact with the cleaning solution, and this diaphragm. A cleaning device comprising a vibrator attached to the outer surface of the cleaning device and vibrated at a high frequency of 600 to 1000 kHz.