JPS6347258B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for cleaning articles, and more particularly to an apparatus for cleaning flaky articles.

In the manufacturing process of semiconductor devices, etc., high temperatures (400~
The heat treatment process (1200℃) is repeated many times. In this case, impurities and dirt adhering to the surface of the thin material that forms the semiconductor device (usually a disk-shaped thin piece with a diameter of 50 to 150 mm and a thickness of 0.3 to 1.0 mm: wafer) are removed from the wafer during heat treatment. It causes chemical reactions and also diffuses inside the wafer, resulting in the introduction of crystal defects, reduced carrier lifetime, abnormal diffusion, damage to device patterns, and other fatal adverse effects on device fabrication. . For this reason, a method is used in which the wafer is cleaned with a chemical solution, pure water, etc. immediately before the heat treatment process described above to remove contamination such as metals, organic substances, dust, and chemical residues adhering to the surface.

In recent years, as device patterns have become finer in areas such as LSIs, even if the aforementioned contaminated area is a microscopic area of several micrometers or less, a failure in one component can lead to failure of the entire chip (approximately several tens of mm ² ). Since then, it has come to have a major influence on product yield. For this reason, the problem of wafer contamination has become an important issue not only in the high-temperature heat treatment process mentioned above, but also in processes at room temperature or relatively low temperatures (400 to 1000°C) such as lithography processes and metal thin film formation processes. There is.

FIG. 1 shows a flowchart of a silicon wafer cleaning method in conventional heat treatment steps such as oxidation and diffusion. First, the wafer is immersed in hydrofluoric acid to remove the natural oxide film formed on the surface by etching, and also remove the attached dust. Next, after washing with water, it is immersed in nitric acid solution to dissolve and remove metal contamination. Finally, after washing with water, drain and dry using a rotary drying method.

The above operation is usually carried out by storing a certain number of wafers 1 in the wafer cartridge 2, as shown in FIG.
It is immersed in a hydrofluoric acid bath 3a. After completing the immersion for a predetermined time, the cartridge 2 is pulled up and transferred to a pure water tank 3b for washing. Similarly, after being immersed in a nitric acid tank 3c and washed in a pure water tank 3d, the wafer 1, together with the cartridge 2, is transferred to a rotary dryer 4 shown in FIG. 2b and spin-dried. In this case, in order to enhance the cleaning effect, an ultrasonic vibrator 5 may be attached to the washing tank to perform ultrasonic cleaning.

However, in the conventional cleaning method, the wafer is once removed from the cleaning solution and transferred to another cleaning solution, so the wafer is susceptible to contamination by foreign matter floating on the liquid surface or foreign matter in the atmosphere. Since a large number of wafers are held in a cartridge for cleaning, non-uniform cleaning tends to occur within or between wafers depending on the wafer position or due to stagnation of the liquid in the cleaning tank. Since the ultrasonic vibration is absorbed by the resin cartridge and weakened, the cleaning effect on the wafer is small. Since the operation is batch-type, it is difficult to make it continuous. Too much cleaning fluid is used. Cartridges are made of resin and are prone to electrostatic adhesion of dust, which can easily cause wafer contamination. Since a cartridge is used, there is a drawback that contamination due to damage to the wafer surface is likely to occur during transfer between processes.

Recently, as wafer diameters have increased to 100 to 150 mm, single-wafer processing in each process is being considered, and improving the conventional wafer cleaning method described above is becoming a more important issue.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the conventional cleaning methods described above and to provide a cleaning device that does not allow impurities, foreign matter, dirt, etc. to adhere to the surface of the object to be cleaned.

The cleaning device of the present invention is characterized in that the cleaning liquid is supplied from a jet hole provided at the bottom of the cleaning tank, and a portion of the cleaning liquid is discharged from a drain port provided at the center. According to such a method, the object to be cleaned can be maintained in a floating state in the liquid and can also be stopped, so there is no need to use a cleaning jig. That is, the feature of the cleaning device of the present invention is that the cleaning device of the present invention cleans flaky articles by
In a cleaning device having a cleaning tank that performs cleaning with cleaning liquid stored inside each tank, the cleaning tank is divided by a bottom part thereof and a gate watertightly surrounding the bottom part, and the bottom part of the divided cleaning tank is a drain for discharging the cleaning liquid that is provided approximately at the center of each of the washing tanks and sucks the cleaning liquid from the lower surface of the flaky article supplied in the divided cleaning tank; and a drain that surrounds the drain at the bottom of the cleaning tank. and a plurality of cleaning liquid spouting holes for spouting the cleaning liquid toward the lower surface of the flaky article.

Another feature is that the items to be cleaned after cleaning are dried without exposing them to the outside air until immediately before drying.

The present invention will be explained below with reference to FIGS. 3 to 5.

FIG. 3 is an explanatory diagram of the configuration of the cleaning device of the present invention. 1 is a silicon wafer as a flaky article; 6
3 is a wafer transfer device, and 3 is a cleaning tank. Cleaning tank 3
There are three tanks 3-1, 3- with a gate 7 that can be opened and closed.
It is divided into 2, 3-3. An ultrasonic horn 5 is installed in the cleaning tank 3-3. FIG. 4 is an enlarged cross-sectional view of the cleaning tank, and FIG. 6 is a perspective view. Reference numeral 8 represents a cleaning liquid jet hole, and 9 represents a cleaning liquid drain. Piping 10 is connected to the jet hole 8 and the drain 9, respectively, as shown in FIG. 4, and the cleaning liquid is supplied and discharged in the direction of the arrow. Further, each amount is regulated by a flow meter 11 and a needle valve 12.
13 and 14 are supply side and drain side switching valves, respectively. 15 and 16 are storage tanks for chemical solutions and pure water, 1
7 indicates a feed pump. 18 is each cleaning tank 3-1,
This is an overflow receiver corresponding to 3-2 and 3-3. The liquid received in the receiving tank 18 joins the drain 9. 19 is a rotary dryer, 20 is a dryer water tank,
21 is a pure water supply valve, 22 is a drain valve, 23
is the overflow drain. 24 is a wafer transport belt, and 25 is a wafer unloader arm. Further, 26 in FIG. 5 is a wafer transfer device guide groove.

Next, a specific wafer cleaning method will be explained. First, the wafer 1 is transported by the conveyor belt 24.
First, it was thrown in at 3-1. Pump 1 is installed in tank 3-1.
7 supplies the chemical liquid from the storage tank 15 through the spout hole 8, and this cleaning liquid still overflows from the upper part of the cleaning tank through the drain 9 and returns to the storage tank 15 through the receiving tank 18. At this time, the state of the wafer 1 in the cleaning tank 3-1 and the flow state of the chemical solution are shown in FIGS. 4 and 5. By adjusting and optimally selecting the amount of ejection from the ejection hole 8 and the amount of drain from the drain 9 using the needle valve 12 and the flow meter 11, buoyancy can be given to the wafer 1, and the amount of liquid flowing toward the drain 9 can be optimally selected. By this flow, the wafer 1 can be stopped at a position where the center of the wafer 1 and the center of the drain 9 coincide. Therefore, there is no need to use a cleaning jig.

Wafer 1 cleaned for a predetermined time in tank 3-1 is 3-1
Open the gate 7 between the tank 3-2 and the wafer transfer device 6.
is transferred to the intermediate tank 3-2. Transfer device 6
Since the wafer moves along the guide groove 26 at the bottom of the cleaning tank, no wafer transfer errors occur. Similarly to tank 3-1, tank 3-2 is connected to storage tank 1 by switching valve 13.
5 chemical solution is being circulated. As described above, the wafer 1 is transferred to the tank 3-2, and at the same time the gate 7 between the tanks 3-1 and 3-2 is closed, and then the valve 13 is closed.
The switching tank 3-2 is supplied with pure water from the storage tank 16 to replace the chemical solution. In this case, it goes without saying that the supply of liquid from the ejection holes is not interrupted and the wafer 1 is kept floating in the liquid. Also,
Since the drain side switching valve 14 is closed on the chemical liquid storage tank 15 side at the same time as pure water is supplied, pure water does not get mixed into the chemical liquid tank 15.

After the wafer 1 has been replaced with pure water for a predetermined period of time, it is transferred to the tank 3.
The gate 7 between the tank 2 and the tank 3-3 is opened, and the water is transferred by the transfer device 6 to the tank 3-3, which is always supplied with pure water.

By the method described above, the wafer 1 is transferred from the chemical bath to the pure water bath without coming into contact with the outside air and without using a cleaning jig.

On the other hand, after the pure water in the tank 3-2 is drained by switching the valves 13 and 14, the chemical solution in the chemical solution tank 15 is supplied again in order to wait for the transfer of the next wafer 1.

In this example, a tank 3-3 was added to improve the cleaning effect.

The wafer floating and suspended in the pure water tank 3-3 is further ultrasonically cleaned in the tank 3-3. Since the ultrasonic vibrator 5 is installed near the liquid surface of the tank 3-3, the wafer is ultrasonically cleaned between the bottom of the tank and the vibrator. In this case, the vibrator 5 is not limited to being placed near the liquid surface if structurally permitted. As a result, the ultrasonic vibrations are directly transmitted to the wafer, and foreign matter firmly attached to the surface of the wafer 1 can be removed.

After ultrasonic cleaning, the wafer 1 is further washed with water in the tank 3-3, and then the gate 7 is opened and the spin dryer 19
The wafers are transferred to the wafer storage section. At this time, the spin dryer 19 is filled with pure water from the pure water supply port 21 to a level greater than the height of the wafer storage portion, and is drained from the overflow drain port 23, so that the wafer 1 does not come into contact with the outside air. When the wafer 1 is stored in the wafer storage section of the spin dryer 19, the gate 7 is closed, the water supply valve 21 is closed, and the drain valve 22 is opened to drain the pure water in the water tank 20 of the spin dryer 19 all at once. At the same time, the drying device 19 is rotated to spin dry the wafer 1. In this case, since the wafer 1 is housed in the gap between the rotating parts and spin-dried as shown in FIG. 3, re-contamination of the wafer 1 due to splashing of water droplets can be reduced.

The wafer 1 that has finished spin drying is transferred to the unloader 25.
It is taken out from the rotary dryer 19 by the vacuum chuck at the end of the arm and sent to the next process.

Of course, in order to minimize outside air contamination, the part of this cleaning equipment shown in broken line in Figure 3 is isolated in an atmosphere of dedusted air or an inert gas such as nitrogen, and furthermore, the gas generated from the chemical solution is separated into a dedicated duct. Needless to say, the air is being exhausted.

According to the semiconductor wafer cleaning apparatus described above, wafers can be transferred between different types of cleaning liquid tanks without coming into contact with the outside air, wafers can be uniformly cleaned by single-wafer processing, and wafers can be chipped without the need for cleaning cartridges. etc. does not occur,
Because the effectiveness of ultrasonic cleaning is enhanced, the number of foreign particles adhering to the wafer surface after cleaning can be significantly reduced compared to conventional cleaning equipment.

Further, according to the present invention, since a single wafer processing method is used, cleaning of large-diameter wafers and continuity between processes are facilitated. Furthermore, since the volume of the cleaning tank can be reduced, other advantages such as the ability to reduce the amount of chemical solution used can be obtained.

In the above explanation, the case where two types of cleaning liquids are used is explained. If two or more types of cleaning liquid are used, tank 3-3 should be used as a different chemical liquid, and tank 3-2 should be structured so that three types of cleaning liquid can be supplied by a switching valve (chemical liquid A → pure water → chemical liquid B). It can be easily expanded. Of course, after the added washing tank, it is necessary to connect two tanks and a drying device. However, if sufficient water washing is performed in the intermediate tank and ultrasonic cleaning is performed in the intermediate tank, the cleaning tank immediately before the drying device can be omitted.

Although the present invention has been described using cleaning of semiconductor wafers as an example, it can be applied to thin pieces of any other material.

[Brief explanation of the drawing]

FIG. 1 is a flowchart of the conventional cleaning method, FIG. 2 is a schematic explanatory diagram of the conventional cleaning method, and FIGS. 3, 4, and 5 are schematic diagrams for explaining the cleaning apparatus of the present invention. 3-1, 3-2, 3-3...Cleaning tank, 7...Gate.

Claims (1)

[Claims] 1. A cleaning device having a cleaning tank for cleaning flaky articles one by one with a cleaning liquid stored inside the cleaning tank, the cleaning tank having a bottom and a gate that watertightly surrounds the bottom. a drain for discharging cleaning liquid, which is provided approximately at the center of each of the divided cleaning tank bottoms and sucks the cleaning liquid from the lower surface of the flaky article supplied into the divided cleaning tank; , a plurality of cleaning liquid ejection holes provided at the bottom of the cleaning tank so as to surround the drain and spouting the cleaning liquid toward the lower surface of the flaky article; cleaning of a flaky article; Device.