JPH01297186A - Ultrasonic washing method and apparatus - Google Patents

Abstract

PURPOSE:To uniformly wash and remove foreign matter within a short time by setting the washing solution jet orifice of a ultrasonic washing head used in the washing of a substrate such as a semiconductor wafer to a position separated by 15mm or less from the surface of an object to be washed and inclining the emitting angle of a washing solution by 30-60 deg. with respect to the object to be washed. CONSTITUTION:When an object to be washed is washed with a washing solution carrying an ultrasonic wave, the washing solution jet orifice 1a of an ultrasonic washing head 1 is set to a position separated by 15mm or less from the surface of an object 5 to be washed to set a distance carrying ultrasonic energy sufficiently. The washing solution is emitted at an angle of 30-60 deg.. Further, by reciprocally moving the ultrasonic washing head 1 at a stroke equal to the radius of the object to be washed, the wedge effect of ultrasonic energy is generated in the contact interface of foreign matter and the surface of the object to be washed. Therefore, the adhered foreign matter can be released within a short time and washing irregularity is eliminated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ultrasonic cleaning method and apparatus for cleaning substrates such as semiconductor wafers and disks, and particularly relates to an ultrasonic cleaning method and apparatus for cleaning substrates such as semiconductor wafers and disks. The present invention relates to an ultrasonic cleaning method and apparatus.

[Prior Art] In a conventional ultrasonic cleaning device, an ultrasonic vibrator is attached to a nozzle-shaped cleaning liquid supply path, and from the tip of the nozzle,
By irradiating a cleaning liquid containing ultrasonic waves onto the surface of the object to be cleaned from a vertical direction, foreign matter adhering to the surface of the object to be cleaned is cleaned and removed. Incidentally, related devices of this type include, for example, Japanese Patent Application Laid-Open No. 48-3
5671 and JP-A-56-60677.

[Problems to be Solved by the Invention] The above-mentioned conventional technology does not take into consideration the point of efficiently removing foreign matter adhering to the object to be cleaned in a short time, resulting in long cleaning time and a low foreign matter removal rate. There was a problem that the value was low.

The present invention solves the above-mentioned problems, reduces cleaning time, and
The object of the present invention is to provide an ultrasonic cleaning method that has a high foreign matter removal rate, and an apparatus that can be directly used for its implementation.

[Means for Solving the Problems] The configuration of the ultrasonic cleaning method of the present invention for solving the above problems is such that a cleaning liquid carrying ultrasonic waves is applied to the object to be cleaned from a cleaning liquid spout of an ultrasonic cleaning head. In an ultrasonic cleaning method in which the surface of the object is cleaned by irradiation, the cleaning liquid spout of the ultrasonic cleaning head is spaced a certain distance of 15 mm or less from the surface of the object to be cleaned; , the cleaning liquid containing ultrasonic waves is irradiated onto the surface of the object to be cleaned at a constant irradiation angle within a range of 30° to 60°.

Furthermore, the configuration of the ultrasonic cleaning apparatus of the present invention is capable of irradiating a cleaning liquid containing ultrasonic waves onto a cleaning table on which an object to be cleaned can be placed and a surface of the object to be cleaned. In an ultrasonic cleaning apparatus having an ultrasonic cleaning head equipped with a cleaning liquid spout, the ultrasonic cleaning head is arranged such that the distance from the cleaning liquid spout to the surface of the object to be cleaned is a constant distance of 15 mm or less, and the cleaning liquid spout The ultrasonic cleaning head is capable of setting the irradiation angle of the cleaning liquid ejected from the ultrasonic waves to a fixed angle within the range of 30° to 60°.

More specifically, the above purpose is to irradiate the surface of the object to be cleaned with the cleaning liquid ejected from the cleaning liquid spout of the ultrasonic cleaning head at a distance that is sufficiently loaded with ultrasonic energy, and to effectively apply ultrasonic vibration to the surface of the object to be cleaned. In order to irradiate to
This is achieved by washing.

[Operation] The cleaning liquid containing ultrasonic waves ejected from the cleaning liquid spout of the ultrasonic cleaning head is irradiated onto the surface of the object to be cleaned without losing its ultrasonic energy, removing foreign matter (
In other words, the wedge effect of the ultrasonic energy causes foreign matter (such as dust) to be separated from the surface of the object to be cleaned, and by pushing it outward with the cleaning liquid, the foreign matter on the object to be cleaned can be reduced to 2 particles in a short period of time. Cleaned at removal rate.

[Example] Before entering into the explanation of the example, basic matters related to the present invention will be explained.
This will be explained using drawings.

3 to 7 are for explaining the basic matters related to the present invention, and FIGS. 3 and 4 are schematic diagrams showing the exposed state of the cleaning liquid jetted from the cleaning liquid spout of the ultrasonic cleaning head, 5 and 6, the irradiation angle of the cleaning liquid to the surface of the object to be cleaned is 90°, respectively.

Figure 7 is a schematic diagram showing the foreign matter removal state at 0°.
FIG. 4 is a schematic diagram showing the state of foreign matter removal when the irradiation angle is 30'' to 60°.

In the figure, 1 indicates a cleaning liquid supply port 1b and a cleaning liquid spout 1.
an ultrasonic cleaning head comprising: a, and a vibrator 2 housed therein in a direction perpendicular to the cleaning liquid spout 1a;
After the cleaning liquid supplied from the cleaning liquid supply port is vibrated by a vibrator 2 to generate ultrasonic waves, it can be ejected from the cleaning liquid spout 1a. Reference numeral 5 denotes an object to be cleaned (for example, a Si wafer) to which foreign matter has adhered, and this object to be cleaned 5 is placed and fixed on a cleaning table 9 that rotates in the direction of the arrow.

When the cleaning liquid is supplied to the cleaning liquid supply port 1b of the ultrasonic cleaning head 1 configured as described above, as shown by the arrow in FIG. 3, the cleaning liquid carrying ultrasonic waves is ejected from the cleaning liquid spout 1a.

However, according to the research conducted by the present inventors, as shown in FIG. 4, if the distance is 15 mm or more from the cleaning liquid spout 1a, part of the ultrasonic energy of the cleaning liquid is lost due to exposure. In addition, when we examined the irradiation angle at which the cleaning liquid is spouted, we found that when irradiation is perpendicular to the surface of the object to be cleaned 5 (i.e., at an irradiation angle of 90°), the cleaning liquid ejects as shown in Figure 5. The ultrasonic waves riding on the object give micro vibrations in the vertical direction to the foreign matter on the surface of the object to be cleaned 5. However, since the cleaning liquid is perpendicular to the surface of the object to be cleaned 5, it is difficult for the foreign matter to flow outward.

On the other hand, when the surface of the object to be cleaned 5 is irradiated horizontally (i.e., at an irradiation angle of 0'), as shown in FIG. However, the ultrasonic energy attenuates as the distance from the area increases, resulting in uneven cleaning.

Taking the above points into consideration, we have experimentally investigated a method that can efficiently irradiate attached foreign matter with ultrasonic energy and effectively clean it.

The irradiation angle of the cleaning liquid is set at 30' to 6' with respect to the surface of the object to be cleaned.
0', and it was also found that by setting the distance between the cleaning liquid spout 1a and the surface of the object to be cleaned 5 within 15 mm, it is possible to perform cleaning in a short time, evenly, and with a high rate of foreign matter removal. To explain the cleaning principle using FIG. 7, when a cleaning liquid containing ultrasonic energy is irradiated onto a foreign object from the cleaning liquid jet port 1a of the ultrasonic cleaning head 1, the foreign object and the surface of the object to be cleaned are first irradiated. At the contact interface, a wedge effect occurs due to the ultrasonic energy, and the cleaning liquid penetrates into the contact interface. Then, the foreign matter leaves the surface of the object to be cleaned. This distant foreign object.

The object to be cleaned 5 is cleaned by being swept away by the cleaning liquid.

The present invention has been made based on the above-mentioned basic matters, and will be described below with reference to the drawings and examples.

FIG. 1 is a schematic configuration diagram showing one embodiment of the ultrasonic cleaning device of the present invention, and FIG. 2 is a case in which a Si wafer contaminated with model foreign matter is cleaned by the ultrasonic cleaning device according to FIG. 1. FIG. 2 is a foreign matter removal rate diagram.

In each figure, the parts with the same numbers as those in FIGS. 3 to 7 are the same parts.

The configuration of the ultrasonic cleaning device shown in FIG. 1 will be explained.

A cleaning supply section 6 is connected to the cleaning liquid supply port 1b of the ultrasonic cleaning head 1 via a flexible tube 7, and an ultrasonic power source 3 is connected to the vibrator 2. This ultrasonic cleaning head 1 connects the object to be cleaned 5 from its cleaning liquid spout 1a.
It is fixed to the drive unit 4 in such a position that the distance to the surface is 15 mm and the irradiation angle of the cleaning liquid jetted from the cleaning liquid spout 1a is 30', and the drive unit 4 itself is
While the ultrasonic head 1 to be cleaned is held in the above posture, it can reciprocate in the direction of the arrow in parallel with the object 5 to be cleaned. 8 is a rotation mechanism unit capable of rotating the washing table 9 around its central axis; 10;
1. A discharge port 1 for preventing the cleaning liquid from scattering and discharging the used cleaning liquid. This is an equipment frame that is equipped with an Oa and can house the main parts of the equipment inside.

An embodiment of the ultrasonic cleaning method of the present invention will be described using the ultrasonic cleaning apparatus configured as described above.

The object to be cleaned 5 is placed and fixed on the cleaning table 9.

Here, when the ultrasonic cleaning device is turned on, the rotation mechanism section 8
As a result, the cleaning table 9 rotates at a predetermined number of rotations, and the driving unit 4 causes the ultrasonic cleaning head 1 to reciprocate with a stroke equal to the radius of the object 5 to be cleaned. Electric signals from an ultrasonic power source 3 are converted into ultrasonic vibrations by a vibrator 2. Cleaning liquid supply port 1 from cleaning liquid supply section 6 via flexible pipe 7
The energy of the ultrasonic vibration is transmitted to the cleaning liquid supplied to the cleaning liquid, and the cleaning liquid is irradiated onto the surface of the object to be cleaned 5 from the cleaning liquid spout 1a. Then, the foreign matter on the surface of the object to be cleaned 5 is detached from the surface by the wedge effect of the ultrasonic energy, and the detached foreign matter is pushed outward by the cleaning liquid, falls together with the cleaning liquid, and is discharged from the discharge port 10a. .

In this way, the entire surface of the object to be cleaned 5 is successively cleaned, and after a predetermined period of time, the ultrasonic cleaning device is turned off. When removed from the washing stand 9, a cleaned object 5 can be obtained.

A specific example will be shown.

The object to be cleaned 5 is a Si wafer whose surface is contaminated with model foreign matter of 0.5 μm.

The cleaning conditions were as follows: the cleaning liquid was water, the distance between the Si wafer and the cleaning liquid spout 1a was 15 mm, the rotation speed of the Si wafer was 300 ppm, and the flow rate of the cleaning water was 3 Q/m i
n, ultrasonic frequency is I MHz, ultrasonic output is 10
This was done at 0W. The cleaning liquid spouted from the cleaning liquid spout 1a is irradiated with sufficient ultrasonic energy at a distance of 15 mm, and in order to effectively irradiate ultrasonic vibrations, the cleaning liquid is irradiated at an angle θ = 30° with respect to the surface of the object to be cleaned. By cleaning with a high throughput, we were able to obtain a high cleaning effect in removing foreign substances.

The foreign matter removal rate in this case is as shown by the solid line connecting the 0 marks in Figure 2, and the foreign matter removal rate rises faster than when θ = 90°, O'', and the foreign matter removal rate reaches saturation in 90 seconds. I know what you're doing.

According to the embodiment described above, since the ultrasonic energy sufficiently reaches the object to be cleaned 5, the wedge effect against the foreign matter is large, and the spray of the cleaning liquid also has the effect of pushing away the foreign matter, and the synergistic effect of these two , it is possible to perform high-throughput cleaning with a high foreign material removal rate. This is particularly effective for removing foreign matter adhering to the grooves when cleaning an object to be cleaned that has grooves formed on its surface.

[Effects of the Invention] As described above in detail, according to the present invention, it is possible to provide an ultrasonic cleaning method that requires a short cleaning time and has a high foreign matter removal rate, and an apparatus that is directly used for carrying out the ultrasonic cleaning method.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of the ultrasonic cleaning device of the present invention, and FIG. 2 is a diagram showing the case where a Si wafer contaminated with model foreign matter is cleaned by the ultrasonic cleaning device according to FIG. 1. The foreign matter removal rate diagrams in Figures 3 to 7 are for explaining the basic matters related to the present invention. A schematic diagram showing the atomization state; FIGS. 5 and 6 are schematic diagrams showing the foreign matter removal state when the irradiation angle of the cleaning liquid to the surface of the object to be cleaned is 90° and Oo, respectively; FIG. It is a schematic diagram showing the removal state of foreign matter when the irradiation angle is 30° to 60''. 1... Ultrasonic cleaning head, 1a... Cleaning liquid spout,
5...Object to be cleaned, 9...Cleaning table.

Claims (1)

[Claims] 1. An ultrasonic cleaning method in which a cleaning liquid carrying ultrasonic waves is irradiated onto the surface of the object to be cleaned from a cleaning liquid spout of an ultrasonic cleaning head to clean the object to be cleaned. , the cleaning liquid injection port of the ultrasonic cleaning head should be 15 mm from the surface of the object to be cleaned.
The cleaning liquid containing ultrasonic waves is irradiated from the cleaning liquid spout to the surface of the object to be cleaned at a constant irradiation angle within a range of 30° to 60° with the cleaning liquid spout being spaced apart by a certain distance as shown below. Characteristic ultrasonic cleaning method. 2. It has a cleaning table on which the object to be cleaned can be placed, and an ultrasonic cleaning head equipped with a cleaning liquid spout that can irradiate the surface of the object to be cleaned with a cleaning liquid carrying ultrasonic waves. In an ultrasonic cleaning device, the distance between the ultrasonic cleaning head and the cleaning liquid spout to the surface of the object to be cleaned is 15 mm.
The irradiation angle of the cleaning liquid containing ultrasonic waves is ejected from the cleaning liquid spout at a certain distance of 30° to 60 mm.
An ultrasonic cleaning device characterized by having an ultrasonic cleaning head that can be set at a certain angle within a range of degrees.