JP2001007067A - Rotary cleaning method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable removal of dust on a semiconductor device as an object to be cleaned at a low rotational speed, in cleaning the semiconductor device. SOLUTION: In the method, a cleaning solution is supplied onto an object 7 to be cleaned during the rotation of the object 7 to realize rotational cleaning in a noncontact manner. In this case, the method includes a process of lowering a redox potential of the cleaning solution and a process of applying ultrasonic waves to the cleaning solution, and the object is rotated at a rotational speed which is not smaller than 20 rpm and not larger than 50 rpm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rotary cleaning method and a cleaning apparatus. More specifically, the present invention relates to a rotary cleaning method and a cleaning apparatus used for removing dust from a wafer or the like in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art Cleaning apparatuses for cleaning semiconductor wafers are widely used for removing dust on wafers in each step of a semiconductor manufacturing process. In recent years, as a wafer processing method of a cleaning apparatus, a cleaning apparatus called a scrubber that mainly removes wafer dust based on a physical cleaning action is generally used.

The types of scrubber cleaning methods are broadly classified into two types: physical cleaning methods and chemical cleaning methods, and mainly include the following cleaning methods. Cleaning with high-pressure jet jet of pure water (method 1), cleaning with brush (method 2), cleaning by adding ultrasonic waves to pure water (method 3), cleaning with flowing acid or alkali solution (method 4), ozone water Flushing (method 5), and the like.

FIG. 11 is a schematic view of a cleaning apparatus using a high-pressure jet jet of pure water according to the above-described method 1. As shown, pure water flows into the high-pressure pure water generator 51 from A. The high-pressure pure water compressed by the high-pressure pure water generator 51 passes through a high-pressure resistant tube 52 and passes through a nozzle 53 having a diameter of 0.1 mm.
Spouting out like a thread as indicated by arrow C. A chuck 55 (vacuum chuck or mechanical chuck) rotatable by a motor 54 is provided below the nozzle 53, and a wafer 56 is chucked by the chuck 55. The high-pressure pure water indicated by the arrow C ejected from the nozzle 53 is ejected onto the wafer 56 rotating at a high speed, whereby dust adhering on the wafer 56 is removed. At the time of cleaning, high-pressure pure water scattered outside the system of the wafer 56 is dropped on the lower portion of the wafer 56 by a cover 57 covering the periphery of the wafer 56.

FIG. 12 is an explanatory view of a cleaning method using the cleaning apparatus of FIG. As shown in the drawing, the high-pressure pure water ejected from the nozzle 53 scans between both ends of the wafer 56 as shown by an arrow D so as to pass through the center 58 of the wafer 56 rotating at a high speed in the B direction. With such a method, high-pressure pure water is applied to the entire surface of the wafer 56, dust on the wafer is removed by the high-pressure pure water, and the high-pressure pure water is discharged out of the wafer system together with the high-pressure pure water.

[0006]

However, in the conventional cleaning method (method 1), dust on the wafer can be removed only to a certain amount, and a sufficient dust removal rate cannot be obtained. In order to further increase the removal rate, increase the wafer rotation speed, increase the pressure of pure water even further,
Even if the number of scans was increased, a 100% dust removal rate could not be obtained. Further, when such a high-pressure and high-rotation method is used, the wafer surface may be damaged, and the yield of the wafer in the manufacturing process may be reduced.

Another problem other than the removal rate is that a stainless steel material is often used for the high-pressure pure water generator, and when pure water is compressed under high pressure, such as Fe, Cr, Ni, etc. from the stainless steel material. The problem of metal elution is inevitable, and this metal material causes a decrease in the insulating property of the gate oxide film formed particularly on the wafer, causing a reduction in the breakdown voltage.

[0008] The problems with the above-described cleaning method are causing serious problems in today's semiconductor fine pattern process in which the wiring width is reduced. In addition, in addition to the problem of the yield, the problem of quality deterioration due to metals and the like will be more important in the future. Therefore, it is expected that a serious problem will be caused as a quality problem for a semiconductor product particularly when a large number of semiconductors are manufactured.

On the other hand, as a problem of the other methods 2 to 5 described above, the brush cleaning of the method 2 may cause a scratch on the wafer surface, and the method of adding ultrasonic waves to the pure water of the method 3 is different from the wafer cleaning method. Without high rotation, dust removal cannot be obtained. The method of flowing a chemical solution such as an acid or an alkali in the method 4 uses a large amount of the chemical solution, and thus causes an environmental problem.
In the method of flowing ozone water, cleaning with ozone water itself cannot be expected, and there is an environmental problem as in method 4 because it requires a combination with a chemical solution.

Also, Japanese Patent Application Laid-Open Nos. 8-78647, 9-270412 and 10-256216
Japanese Patent Application Laid-Open No. 8-78647 discloses a method for removing dust from a wafer, and the contents described in Japanese Patent Application Laid-Open No. 8-78647 use the above methods 3 and 4. In the description of 270412, the above methods 4 and 5 are used, the wafer rotation speed during cleaning is 1500-3000 rpm, and in the description of JP-A-10-256216, the above methods 3, 4, and 5 are used. The wafer rotation speed at the time of cleaning was 300 rpm. Therefore, any of the contents described in the publications is a method of cleaning the wafer by rotating the wafer at a high speed, and the above problem remains.

An object of the present invention is to provide a rotary cleaning method and a cleaning apparatus capable of removing dust from an object to be cleaned at a low rotation speed when cleaning a semiconductor device.

[0012]

In order to achieve the above object, according to the present invention, there is provided a rotary cleaning method for supplying a cleaning liquid onto an object to be cleaned while rotating the object to be cleaned and performing non-contact cleaning. A rotary cleaning method comprising: a process for lowering the oxidation-reduction potential of the cleaning solution; and a process for adding ultrasonic waves to the cleaning solution, wherein the object to be cleaned is rotated at a rotation speed of 20 rpm or more and 50 rpm or less. provide.

[0013] According to this structure, the oxidation-reduction potential of the cleaning solution is reduced, so that the cleaning power is improved. Since it is not necessary to increase the pressure of the cleaning solution, no metal is eluted from the apparatus, and metal contamination on the object to be cleaned is prevented. Disappears. The number of rotations of the object to be cleaned at the time of cleaning is 20 to 50 rpm, which can be performed at a lower rotation than in the past, so that large substrates and the like can be cleaned.

In a preferred configuration example, the process for lowering the oxidation-reduction potential is a process of adding hydrogen.

According to this configuration, since the oxidation-reduction potential of the cleaning liquid is reduced by adding hydrogen, the cleaning power is improved.

According to the present invention, there is further provided a rotary cleaning table on which the object to be cleaned is mounted, a nozzle for supplying a cleaning liquid to the object to be cleaned on the rotary cleaning table, and a pipe connecting the nozzle to a pure water supply source. And a hydrogenation device provided on the pipe, wherein the rotary washing table is rotatable at 20 rpm or more and 50 rpm or less.

According to this configuration, the above-described method of the present invention can be properly performed, and as described above, since the pressure of the cleaning liquid does not need to be increased, no metal is eluted from the apparatus, and metal contamination on the object to be cleaned is achieved. And the number of rotations of the object to be cleaned during cleaning is 2
Since the rotation can be performed at a low rotation of 0 to 50 rpm as compared with the related art, cleaning of a large substrate or the like becomes possible.

In a preferred configuration example, an alkaline liquid injection device is provided on the pipe via a switching valve, and an alkaline liquid can be injected into the cleaning liquid when necessary.

According to this configuration, the oxidation-reduction potential can be further lowered by adding hydrogen to pure water to lower the oxidation-reduction potential and then further injecting an alkaline solution, so that the detergency is further improved. improves.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram illustrating a cleaning device and a cleaning method of the present invention, and FIG. 2 is an explanatory diagram of a cleaning method using the cleaning device of FIG. As shown in FIG. 1, pure water flows into the hydrogenation device 1 from D. This hydrogenation device, for example, filling a number of hollow fibers in a container,
Hydrogen is supplied through the hollow fiber, and pure water is passed through a container filled with the hollow fiber, whereby hydrogen is added from the hollow fiber to pure water. As a result, the oxidation-reduction potential (ORP) of pure water is reduced, and the cleaning power is improved.

In this case, the oxidation-reduction potential can be controlled by adjusting the pressure and flow rate of hydrogen or the flow rate of pure water. The oxidation-reduction potential of pure water is about 200 mV, and the addition of hydrogen lowers the oxidation-reduction potential of pure water to about -500 mV at the maximum. By adding a further small amount of alkaline solution to this as described below,
The oxidation-reduction potential drops to about -700 mV.

The pure water to which hydrogen has been added by the hydrogenator 1 becomes hydrogen water having a low oxidation-reduction potential, and flows from the tube 10 through the tube 12 via the valve 9 to the nozzle 3. Ultrasonic waves are applied to the hydrogen water flowing into the nozzle 3 by an ultrasonic generator 4 provided in the nozzle 3 to complete a cleaning liquid.

Instead of adding hydrogen to pure water, pure water may be electrolyzed to lower the oxidation-reduction potential. In this case, an electrolyzer is provided in place of the hydrogenator 1, and water whose potential has become (−) by electrolysis is used as washing water.

The above-mentioned hydrogen water can flow into the alkaline liquid injection unit 2 without passing through the tube 12 by switching the valve 9. A small amount of alkaline solution is injected into hydrogen water by the alkaline solution injection unit 2, and then the nozzle 3 passes through a tube 11 connected to the nozzle 3.
Ultrasonic waves are applied by an ultrasonic generator 4 provided therein. Thus, the cleaning liquid is completed. As described above, by injecting the alkaline solution, the oxidation-reduction potential is further lowered, and the detergency is further improved. In this case, since the redox potential can be sufficiently reduced by using a small amount of the alkaline solution to be controlled by the pH, there is no problem with respect to the environment due to the alkaline solution.

A chuck 6 (vacuum chuck or mechanical chuck) rotatable by a motor 5 is provided below the nozzle 3, and a wafer 7 is chucked on the chuck 6. The cleaning liquid flowing out of the nozzle 3 is supplied onto the wafer 7 rotating at a low rotation as described later, and cleans and removes dust and the like on the wafer 7. At the time of cleaning, cleaning water (hydrogen water) scattered from the wafer 7 to the outside of the system is prevented from scattering to the surroundings by the cover 8 and is dropped on the inner surface of the cover under the wafer 7.

As shown in FIG. 2, 20 to 50r in the R direction.
The cleaning liquid flowing out of the nozzle 3 with respect to the low-rotation wafer 7 in the pm rotation range scans between both ends of the wafer 7 as shown by an arrow E so as to pass through the center 13 of the wafer 7. This scan is performed at least once. With this method, the entire surface of the wafer 7 is scanned, and dust on the wafer 7 is discharged out of the wafer system together with the cleaning liquid.

FIG. 3 is a schematic diagram when a stick type is used for the nozzle portion of the cleaning apparatus of FIG. As shown in the drawing, a plurality of cleaning liquid outlets 14 are arranged in a row at the tip of the nozzle. The use of the stick type nozzle 15 allows the cleaning liquid to flow over the entire surface of the wafer 7 without scanning between both ends of the wafer 7. In this case, the method of manufacturing the cleaning liquid is the same as in the example of FIG.

FIG. 4 is a graph showing the relationship between the wafer rotation speed and the dust removal rate when the cleaning apparatus and the cleaning method of FIG. 1 are used. The dust removal rate increases with the rotation of the wafer, and decreases as the rotation rate decreases. However, the dust removal rate increases in the wafer rotation range of 20 to 50 rpm indicated by a. The present invention utilizes the fact that the dust removal rate increases at a low rotation. Based on this characteristic, when the number of scans at both ends of the wafer is increased at 30 rpm in this rotation range (1 to 5 times in the figure, once scan, twice scan,...)
(The symbol indicates five scans.) The larger the number of scans, the higher the dust removal rate.

Table 1 shows the results of comparing the dust removal rates when using the present invention and when using the conventional cleaning method.

[0030]

[Table 1]

The results shown in this table show that the values on the wafer are equal to 0.
This figure intentionally contaminates the Si fragments of 2 μm or more, and shows their removal rates before and after cleaning. A mega frequency ultrasonic wave is applied to the oxidation-reduction potential, and the wafer rotation speed is 30 r.
pm. As is clear from the results, a higher removal rate can be obtained when hydrogen is added, which is the cleaning method of the present invention, as compared with the conventional high-pressure pure water jet cleaning method, and when the alkaline solution is injected. Can obtain a higher dust removal rate.

The detailed processing method of the present invention is as follows. Rotate the wafer at 30 rpm, onto the wafer,
The oxidation-reduction potential is lowered to -500 mV or less, and a cleaning liquid (pure water only added with hydrogen or an alkali liquid added after hydrogenation) with an ultrasonic wave of 1 MHz is supplied. At this time, if there is only one cleaning liquid outlet, both ends of the wafer are scanned one or more times (no scanning is required for the stick nozzle type), and after the cleaning liquid has been flown, pure water or alkali is not added to the wafer. Rinsing water (hydrogen water) with a reduced oxidation-reduction potential is flowed to rinse the wafer. The rotation speed at this time is 300 rpm, and the rinsing time is 20 seconds or more. After this, rinse water is stopped and 300
After spinning for 1 second or more at rpm to drain water (liquid), 300
Rotate at 0 rpm to shake off the liquid on the wafer and dry. Do this for at least 20 seconds.

In the present invention, since cleaning is performed at a low rotation speed, the present invention can be applied to a rectangular substrate such as a liquid crystal substrate or a large rectangular substrate such as a plasma display. At present, the mainstream size of a semiconductor wafer is 200 mm (8 inches), but it can be easily applied to a 300 mm wafer. In these cases, in the method of the present invention, the number of revolutions is reduced even during rinsing, and the processing time is increased to rinse the entire object to be cleaned. In addition, the number of rotations during the drying process is set to 3000 rpm or less, and the processing time is lengthened. At this time, if water (liquid) can not be drained due to the reduced number of rotations, N2 blow or the like is performed on the rotating substrate to make it easy to dry.

In order to confirm the validity of the region of the number of rotations of the wafer of the present invention, three processing conditions (scan time, rinsing liquid amount, wafer amount) The following describes an example in which cleaning is actually performed while changing the distance between the nozzle and the nozzle).

FIG. 5 is a graph showing the relationship between the number of rotations of the wafer and the removal rate when the scan time of the wafer is changed, and FIG. 6 is an explanatory diagram of the cleaning method of FIG. In FIG. 5, ◆ indicates a scan time of 8 seconds, and ■ indicates a scan time of 30 seconds. As shown in FIG. 6, scanning is performed on the wafer as indicated by arrow Z from the center 7a of the wafer rotating in the R direction toward the end. Or center 7 between both ends of wafer rotating in R direction
The nozzle moves through a to scan across the wafer. When the scan time is changed, the longer the scan time is, the higher the removal rate is. Also, at any scan time, the removal rate is within the range of the wafer rotation speed 20 to 50 rpm shown in a of FIG. Are shown.

FIG. 7 is a graph showing the relationship between the wafer rotation speed and the removal rate when the flow rate of the rinsing water is changed, and FIG. 8 is an explanatory diagram of the cleaning method of FIG. In FIG.
Indicates a rinse water flow rate of 0.5 l / min, and ■ indicates a rinse water flow rate of 1.0 l / min. As shown in FIG. 8, the wafer 7 is scanned with the cleaning liquid C from the nozzle 3 as shown by the arrow Z, and the rinsing liquid is supplied from the rinsing liquid supply pipe 16 as shown by the arrow F to perform rinsing at the same time. In this case, in any case where the flow rate of the rinsing water is changed, a peak of the removal rate is shown between the wafer rotation speeds of 20 to 50 rpm in the range indicated by a in FIG.

FIG. 9 is a graph showing the relationship between the number of rotations of the wafer and the removal rate when the distance between the wafer and the nozzle is changed, and FIG. 10 is an explanatory diagram of the cleaning method of FIG. FIG.
◆ is 20 mm, ■ is 10 mm, △ is 15 mm
3 shows the distance between the wafer and the nozzle. As shown in FIG. 10, the change in the distance between the wafer and the nozzle is obtained by changing the distance Y between the nozzle at the tip of the nozzle and the center of the wafer. However, the wafer rotation speed 20 to 50r shown in a of FIG.
The peak removal rate is shown in the range between pm.

[0038]

As described above, in the present invention, since the wafer can be cleaned at a low rotation speed, it can be used for cleaning a large substrate or the like. It is possible to clean a large substrate such as a mold substrate or a plasma display. Since there is no need to increase the pressure of the pure water of the cleaning liquid, there is no risk of metal contamination of the metal of the pure water high-pressure apparatus eluted into the pure water. Therefore, the process quality is improved, and the yield is improved.

Further, since the object to be cleaned is non-contact cleaning, the object to be cleaned is not damaged, and the brush is not replaced as in the brush cleaning method. Uptime increases. In addition, it is possible to perform cleaning with a reduced amount of chemical solution, which is suitable for environmental problems. Since cleaning can be performed without using a chemical solution, waste liquid treatment can be extremely reduced, the purchase cost of the chemical solution can be reduced, the device can be easily designed, and the equipment for acid / alkali drainage in the secondary work is not required.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a cleaning apparatus and a cleaning method according to the present invention.

FIG. 2 is an explanatory view of a cleaning method using the cleaning device of FIG. 1;

FIG. 3 is a schematic diagram when a stick type is used for a nozzle portion of the cleaning device of FIG. 1;

FIG. 4 is a graph showing the relationship between the number of rotations of a wafer and the dust removal rate when the cleaning apparatus and the cleaning method of FIG. 1 are used.

FIG. 5 is a graph showing a relationship between a wafer rotation speed and a removal rate when a scan time of a wafer is changed.

FIG. 6 is an explanatory view of the cleaning method of FIG. 5;

FIG. 7 is a graph showing the relationship between the wafer rotation speed and the removal rate when the flow rate of the rinse water is changed.

FIG. 8 is an explanatory view of the cleaning method of FIG. 7;

FIG. 9 is a graph showing a relationship between a wafer rotation speed and a removal rate when a distance between a wafer and a nozzle is changed.

FIG. 10 is an explanatory diagram of the cleaning method of FIG. 9;

FIG. 11 is a schematic view of a conventional cleaning apparatus using a high-pressure jet jet of pure water.

FIG. 12 is an explanatory diagram of a cleaning method using the cleaning device of FIG. 11;

[Explanation of symbols]

1: hydrogenation device, 2: alkaline liquid injection unit, 3:
Nozzle, 4: Ultrasonic generator, 5: Motor, 6: Chuck, 7: Wafer, 8: Cover, 9: Valve, 10, 1
1, 12: tube, 13: center, 14: washing liquid outlet, 15: stick type nozzle, 16: rinse liquid supply pipe.

Claims (4)

[Claims] 1. A rotary cleaning method for supplying a cleaning liquid onto an object to be cleaned while rotating the object to be cleaned and performing non-contact cleaning, comprising: a process for lowering an oxidation-reduction potential of the cleaning liquid; A process of adding ultrasonic waves to the object, wherein the object to be cleaned is rotated at a rotation speed of not less than 20 rpm and not more than 50 rpm. 2. The rotary cleaning method according to claim 1, wherein the process for lowering the oxidation-reduction potential is a process of adding hydrogen. A rotary washing table on which the object to be cleaned is mounted; a nozzle for supplying a cleaning liquid to the object to be cleaned on the rotary washing table; a pipe connecting the nozzle to a pure water supply source; A rotary cleaning device, comprising: a hydrogenation device provided on a pipe; wherein the rotary cleaning table is rotatable at 20 rpm or more and 50 rpm or less. 4. The rotary cleaning apparatus according to claim 3, wherein an alkaline liquid injection device is provided on the pipe via a switching valve, and an alkaline liquid can be injected into the cleaning liquid when necessary.