JPH0975874A - Single crystal block cleaning method and cleaning apparatus therefor - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To perform cleaning processing of a wafer cut by a wire saw in a short time. Wire saw cutting Abrasive particles and oil are reliably removed from the wafer surface. A single crystal block 13 is cut by a wire saw cutting machine. The single crystal block 13 is suspended in the cleaning liquid tank 16. The single crystal block 13 is moved up and down by 100 mm in a cleaning solution using an organic solvent-based cleaning agent containing a surfactant and water. At the same time, the ultrasonic wave applying mechanisms 17 and 18 apply low-frequency ultrasonic waves and high-frequency ultrasonic waves in directions parallel to the front and back surfaces of the silicon wafer 14 and orthogonal to each other. As a result, oil and abrasive grains are desorbed and removed from the front and back surfaces of each wafer 14 of the single crystal block 13. The cleaning liquid can flow in and out of the gaps between these wafers 14 to efficiently remove the desorbed components and the like, and prevent re-adsorption.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a single crystal block immediately after being cut with a wire saw and a cleaning apparatus therefor.

[0002]

2. Description of the Related Art Conventionally, when a silicon wafer is manufactured from a CZ single crystal rod, the single crystal rod is cut into a plurality of blocks, and a large number of wafers are sliced from each single crystal block (ingot block). A wire saw was used for slicing the wafer from this single crystal block. That is, after the outer diameter of the block was ground, OF processing was performed and cutting was performed with a wire saw cutting machine. Then, the single crystal block cut by this wire saw is produced in a state where a part of each wafer is continuous to the plate-shaped carbon bed. Then, each wafer is peeled off from the carbon bed, stored in a cassette, and sent to the next chamfering step.

[0003]

In such a conventional wire saw cut wafer, once housed in a cassette, it is taken out one by one and subjected to a cleaning treatment. However, it is difficult to remove the abrasive grains and cutting oil adhering to the wafer surface, and it takes a long time to clean them. This is because, for example, it is necessary to remove cutting oil and remove abrasive grains by different cleaning processes. As a result, the single-wafer processing in the following steps is extremely difficult.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to perform a cleaning process on a wire saw cut wafer in a short time. Another object of the present invention is to provide a cleaning method capable of reliably removing abrasive grains and oil from the surface of a wire saw cut wafer. Another object of the present invention is to provide a device that can perform short-time cleaning.

[0005]

According to a first aspect of the present invention, there is provided a method for cleaning a single crystal block cut by a wire saw, wherein the single crystal block is put into a cleaning liquid, and the axis line of the single crystal block. It is a method for cleaning a single crystal block in which low-frequency ultrasonic waves and high-frequency ultrasonic waves are applied from two different directions orthogonal to each other.

The invention according to claim 2 is the method for cleaning a single crystal block according to claim 1, wherein ultrasonic waves are applied while the single crystal block is vertically swung in a cleaning liquid.

According to a third aspect of the present invention, there is provided a cleaning liquid tank into which the single crystal block can be charged, and a bottom wall of the cleaning liquid tank.
A first ultrasonic wave applying mechanism for applying ultrasonic waves to the cleaning liquid; and a second ultrasonic wave applying mechanism provided on the side wall of the cleaning liquid tank for applying ultrasonic waves having a frequency different from the ultrasonic waves to the cleaning liquid.
The single crystal block cleaning device includes a swing mechanism for moving the single crystal block up and down in the cleaning liquid tank.

[0008]

According to the first aspect of the invention, the single crystal block is inserted into the cleaning liquid tank while being cut with the wire saw, and cleaning is performed. As the cleaning liquid, for example, an organic solvent-based cleaning liquid containing a surfactant and water is used. As a result, the cleaning process can be performed in a short time. Further, the ultrasonic waves applied during cleaning apply a low frequency component and a high frequency component simultaneously and in a direction parallel to the wafer surface. Mainly, the former can efficiently remove abrasive grains and the latter can efficiently remove oil.

According to the second aspect of the present invention, the entire single crystal block is washed in the washing liquid while rocking vertically.
As a result, the slurry or the like remaining in the narrow gap between the adjacent wafers flows out, and moreover, re-adsorption of oil and abrasive grains on the wafer surface can be prevented. The single crystal block may be moved up and down by a distance equal to or more than ¼ of the wafer diameter.

Since the cleaning apparatus according to the third aspect has two ultrasonic wave applying mechanisms for applying ultrasonic waves of different frequencies to the bottom wall and the side wall of the cleaning solution tank, the single crystal block is put into the cleaning solution. In this state, low-frequency and high-frequency ultrasonic waves can be simultaneously applied from two directions orthogonal to the wafer surface. Therefore, oil, abrasive grains, etc. between each wafer can be efficiently removed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 and 2 are views showing a cleaning apparatus according to an embodiment of the present invention. Also, FIG.
FIG. 4 is a conceptual diagram showing a cleaning process according to an example.

As shown in these figures, the single crystal block 13 fixed to the supporting member 12 via the carbon bed 11 is cut by a wire saw cutting machine and formed by connecting a part of a plurality of silicon wafers 14. Has been done. A predetermined gap is formed between the silicon wafers 14 by a wire saw. The cleaning liquid tank 16 into which the single crystal block 13 is charged or charged is a rectangular casing whose upper surface is open, and is formed of, for example, vinyl chloride / SUS. The bottom wall 16A and the side wall 16B of the cleaning liquid tank 16 have first and second ultrasonic wave applying mechanisms 17 and 18, respectively.
Is fixed. These ultrasonic wave applying mechanisms 17, 18
Are ultrasonic waves of different frequencies, for example, low frequency ultrasonic waves (5 to 30 kHz) and high frequency ultrasonic waves (100 to 8 kHz).
00 kHz) is applied to the cleaning liquid.

Although not shown, the single crystal block 13 is suspended by a swinging mechanism and placed in a cleaning liquid tank 16, and is vertically movable in the cleaning liquid. The vertical movement distance of the swing mechanism is, for example, 100 to 200 mm. As the cleaning liquid, for example, an organic solvent-based cleaning agent containing a surfactant and water is used. As the surfactant, "Clean Through (trade name)" manufactured by Kao Corporation can be used. Further, rinsing tanks 19 and 20 are arranged adjacent to the cleaning liquid tank 16. It is assumed that pure water is injected into these rinse tanks 19 and 20.

Therefore, the single crystal block 13 cut by the wire saw is put into the cleaning liquid tank 16 by the swinging mechanism. In this cleaning solution, the single crystal block 13 has, for example, 1
It can be moved up and down by a height of 00 mm. Further, the ultrasonic wave applying mechanisms 17 and 18 simultaneously apply a low frequency ultrasonic wave and a high frequency ultrasonic wave in a direction parallel to the front and back surfaces of the silicon wafer 14 and in a direction orthogonal to each other. As a result, oil and abrasive grains are desorbed and removed from the front and back surfaces of each wafer 14 of the single crystal block 13. At the same time, the cleaning liquid can flow in and out of the gaps between the wafers 14 to efficiently remove the desorbed components and the like, and prevent their re-adsorption.

The following Table 1 shows the relationship between the frequency of the applied ultrasonic waves and the stain components remaining on the front and back surfaces of the silicon wafer after the applied cleaning. As shown in Table 1, application of low-frequency ultrasonic waves is suitable for removing oil components. Further, the application of high frequency ultrasonic waves is effective in removing the abrasive grain component.

[0016]

[Table 1]

Table 2 below shows the relationship between the swing distance of the single crystal block 13 by the swing mechanism and the stain after cleaning. As is clear from Table 2, if the swing distance is ¼ or more of the diameter of the silicon wafer, the stain after cleaning can be sufficiently removed. The swing distance in the table is shown with respect to the diameter of the silicon wafer. The applied ultrasonic waves are 28 kHz and 200 kHz. The cleaning liquid contains the surfactant and the organic solvent.

[0018]

[Table 2] In the table, ◯ indicates a state where stains are completely removed, X indicates an insufficient removal state, and Δ indicates an intermediate state between them. Further, the swing distance is a ratio to the diameter of the wafer, and 1/4 in the table means that the swing distance is 2 inches when the wafer diameter is 8 inches.

Next, Table 3 summarizes the above results. That is, by combining a high frequency ultrasonic wave and a low frequency ultrasonic wave, it is possible to completely remove the oil and the abrasive grains, which are the main components of the dirt remaining on the front and back surfaces of the silicon wafer by wire saw cutting. Shows.

[0020]

[Table 3]

[0021]

According to the present invention, the dirt after cutting the wire saw can be efficiently removed in a short time. For example, compared to the conventional cassette cleaning after single-wafering, about 1 /
The same degree of surface cleaning could be obtained in about 2 hours.
Therefore, according to the cleaning method of the present invention, the wafer can be smoothly processed in the subsequent processes.

[Brief description of drawings]

FIG. 1 is a schematic view showing a single crystal block cleaning device according to an embodiment of the present invention.

FIG. 2 is a schematic view showing a single crystal block cleaning device according to an embodiment of the present invention.

FIG. 3 is a schematic diagram for explaining a cleaning method for a single crystal block according to an embodiment of the present invention.

[Explanation of symbols]

 13 single crystal block, 14 silicon wafer, 16 cleaning liquid tank, 16A bottom wall of cleaning liquid tank, 16B side wall of cleaning liquid tank, 17 first ultrasonic wave applying mechanism, 18 second ultrasonic wave applying mechanism.

Front page continuation (72) Inventor Yoshiki Kitamura 1-5-1, Otemachi, Chiyoda-ku, Tokyo Within Sanryo Material Silicon Co., Ltd. (72) Inventor Kazushige Takaishi 1-1-5, Otemachi, Chiyoda-ku, Tokyo Sanryo Material Silicon Co., Ltd.

Claims (3)

[Claims] 1. A method for cleaning a single crystal block cut with a wire saw, wherein the single crystal block is placed in a cleaning liquid, and a supersonic wave having a low frequency from two directions different in a direction orthogonal to an axis of the single crystal block is used. A method for cleaning a single crystal block in which a sound wave and a high frequency ultrasonic wave are applied. 2. The method for cleaning a single crystal block according to claim 1, wherein ultrasonic waves are applied while the single crystal block is rocked vertically in a cleaning liquid. 3. A cleaning liquid tank into which a single crystal block can be loaded, a first ultrasonic wave applying mechanism provided on the bottom wall of the cleaning liquid tank and applying ultrasonic waves to the cleaning liquid, and provided on a side wall of the cleaning liquid tank, An apparatus for cleaning a single crystal block, comprising a second ultrasonic wave applying mechanism for applying an ultrasonic wave having a frequency different from that of the ultrasonic wave to the cleaning liquid, and a swinging mechanism for vertically moving the single crystal block in the cleaning liquid tank.