JP2014146693A - Cleaning method and cleaning device using ozone water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning method using ozone water, capable of using ozone water at a small amount and a low concentration, causing no uneven cleaning and requiring no complex device configuration.SOLUTION: In a cleaning method for a wafer using ozone water, the wafer is placed in a horizontal orientation in an immersion tray having a waste liquid port, the ozone water is supplied through a supply pipe installed above the wafer, the wafer is cleaned by being immersed into the ozone water in the immersion tray, and the ozone water is discharged through the waste liquid port.

Description

  The present invention relates to a wafer cleaning method and apparatus using ozone water.

  There are two methods for cleaning semiconductor wafers (hereinafter referred to as wafers): a method in which a plurality of wafers are immersed vertically in a cleaning tank filled with a cleaning solution, and a method in which wafers are horizontally placed one by one. There are types.

  Here, an example of a general wafer cleaning flow is shown. The most common cleaning flow includes ammonia water / hydrogen peroxide solution → pure water rinse → hydrochloric acid / hydrogen peroxide solution → pure water rinse → drying. This cleaning method removes organic substances and particles on the surface with the first ammonia / hydrogen peroxide cleaning solution, rinses the cleaning solution with pure water rinse, and then removes metal impurities with the next hydrochloric acid / hydrogen peroxide solution cleaning solution. In this method, the chemicals are washed again with pure water rinse and then dried.

  In general, the cleaning liquid is often used by heating from 60 ° C. to 80 ° C. in order to enhance the cleaning effect. For this reason, a circulation filtration system is attached to the cleaning liquid tank, and the temperature of the cleaning liquid is adjusted by a heater simultaneously with the removal of particles. In some cases, the concentration of the cleaning liquid is controlled to be constant in order to prevent a decrease in the concentration of the cleaning liquid due to evaporation. Furthermore, ultrasonic cleaning may be used in combination in order to improve the ability to remove particles adhering to the wafer. Also, since the cleaning solution used here directly affects the cleanliness quality of the wafer, the concentration of particles and metal impurities in the cleaning solution is strictly controlled, and high-quality ones with extremely few particles and impurities are used. Yes.

  Further, in the above-described general wafer cleaning flow, ozone water may be used instead of rinsing water with pure water, and is introduced as appropriate. Ozone water has a strong oxidizing power, and is used to decompose organic substances adhering to the wafer surface and to oxidize the wafer surface using the strong oxidizing power.

However, ozone water is very unstable and easily decomposes. Since ozone water is obtained by dissolving ozone gas in pure water, if the stirring, bubbling, showering or the like is performed easily, the dissolved ozone gas is released and the concentration of ozone water is lowered.
In order to clean the wafer uniformly with ozone water that easily changes in concentration, it is necessary to bring ozone water with a uniform concentration into contact with the wafer surface.

  As a cleaning method using ozone water, a method in which a plurality of wafers are immersed in a cleaning tank filled with ozone water (Patent Document 1, etc.), ozone water is supplied from a nozzle to a horizontally placed wafer. And a method of performing as a shower (Patent Document 1, etc.) has been performed. However, the former method is not economical because a large amount and high concentration of ozone water is used, and both methods have a non-uniform concentration of ozone water and are difficult to clean evenly. Further, in order to prevent cleaning unevenness, a method of rotating a horizontally placed wafer (Patent Documents 2 and 3) has been studied, but a complicated apparatus configuration is required.

JP 2012-119491 A JP 2001-203182 A JP 2002-25971 A

  That is, in the case of a method in which a wafer is immersed vertically in a cleaning tank filled with ozone water, for example, a method of supplying ozone water from an ozone water supply pipe installed at the bottom of the cleaning tank is common. . A plurality of holes are formed in the supply pipe, and the direction of the holes is often different depending on the structure of the cleaning tank, the wafer holding method, and the like. Although the positions of the holes are various, the holes are generally arranged in the cleaning tank so that the ozone water is uniformly supplied to the wafer surface. However, in this case, a large amount of high-concentration ozone water is required, which is not economical. Further, since ozone water constantly decreases in concentration due to self-decomposition and reaction, a concentration distribution is generated in the cleaning tank. That is, the concentration of ozone water near the outlet of the supply pipe is high, the ozone water concentration decreases along with the liquid flow ejected from the supply pipe, and a gradient occurs in the ozone water concentration in the cleaning tank. Occurs.

  On the other hand, in the case where the wafer is placed horizontally, for example, the wafer is held in a container that can be sealed, and cleaning is performed by spraying ozone water onto the wafer from a shower nozzle attached to the upper and lower parts. (Shower method) is common. As an example of a method for cleaning a wafer having a diameter of 300 mm, a cleaning process is performed by laying out the wafer so as to be sprayed on the entire surface of the wafer from 19 nozzles on the upper and lower sides. However, in the case of this shower method, the ozone water is released from the ozone water as ozone gas due to release from the piping pressure before the ozone water reaches the wafer surface from the shower nozzle, resulting in a significant concentration drop. In order to perform stable cleaning, high-concentration ozone water is required. Furthermore, if ozone water shower is applied non-uniformly on the wafer surface, cleaning unevenness occurs at a large portion and a small portion.

  In order to solve the above-mentioned problem of cleaning unevenness, a method of rotating a horizontally placed wafer has been studied. In a cleaning apparatus using such a method, a chemical-resistant processing chamber, a mechanism for rotating the wafer, and rotation It is necessary to have a complicated apparatus configuration such as a wafer holding mechanism to be operated and an ozone water supply mechanism arranged so as not to obstruct the rotating mechanism, which is not economical.

  The present invention has been made in view of the above circumstances, and a cleaning method using ozone water that can use a small amount and a low concentration of ozone water, has no unevenness in cleaning, and does not require a complicated apparatus configuration, and An object is to provide a cleaning device.

In order to achieve the above object, the present invention provides:
A wafer cleaning method using ozone water,
The wafer is placed horizontally on a dipping tray having a drain outlet on the bottom, the ozone water is supplied from a supply pipe installed above the wafer, and the wafer is immersed in the ozone water with the dipping tray. And a cleaning method using ozone water that drains the ozone water from the drain port.

  With such a cleaning method, a small amount of low-concentration ozone water can be used, there is no cleaning unevenness, and a cleaning method that does not require the use of a complicated apparatus can be obtained.

  At this time, it is preferable to arrange the supply pipe above the center of the wafer.

  In this way, uneven cleaning can be eliminated more effectively.

Further, the present invention is a wafer cleaning apparatus using ozone water,
A holding means for horizontally placing the wafer, and an immersion tray having a drain of the ozone water on the bottom surface;
And a supply pipe for supplying the ozone water from above the wafer.

  With such a cleaning apparatus, it is not necessary to add a complicated apparatus configuration, a small amount of low-concentration ozone water can be used, and cleaning unevenness of the wafer after cleaning can be eliminated.

  At this time, it is preferable that the supply pipe is installed above the center of the wafer.

  Such a supply pipe can eliminate cleaning unevenness more effectively.

  The cleaning method and cleaning apparatus using ozone water of the present invention eliminates the need for an expensive large-flow / high-concentration ozone water production apparatus, and uses a small amount of low-concentration ozone water with an inexpensive and simple apparatus configuration. Therefore, it is possible to perform ozone water cleaning without causing uneven cleaning.

It is the schematic which shows an example of the washing | cleaning apparatus using the ozone water of this invention. 6 is a schematic diagram illustrating an example of a cleaning device used in Comparative Example 1. FIG. 10 is a schematic diagram illustrating another example of the cleaning device used in Comparative Example 2. FIG. FIG. 10 is a schematic diagram showing still another example of the cleaning device used in Comparative Example 3. It is a figure which shows the result of the comparative test of the wafer which cleaned using the cleaning apparatus shown in Example 1 and Comparative Examples 1-3.

  As a result of diligent investigation, the inventors of the present invention need a complicated apparatus configuration if the wafer is placed on a dipping tray and ozone water is supplied from above to immerse and clean the wafer. And the present invention was completed by finding that the wafer does not cause uneven cleaning.

That is, the present invention
A wafer cleaning method and apparatus using ozone water,
The wafer is placed horizontally on a dipping tray having a drain outlet on the bottom, the ozone water is supplied from a supply pipe installed above the wafer, and the wafer is immersed in the ozone water with the dipping tray. The cleaning method and the cleaning device using ozone water are used for discharging the ozone water from the drain port.

  As the cleaning apparatus of the present invention, for example, an apparatus equipped with an ozone water cleaning BOX sealed to prevent the diffusion of ozone gas can be used. Hereinafter, a cleaning apparatus provided with the ozone water cleaning BOX will be described with reference to the drawings.

FIG. 1 is a schematic view showing an example of a cleaning apparatus 10 using ozone water of the present invention installed in the ozone water cleaning BOX 7.
First, the wafer 3 is placed horizontally on a dipping tray 4 having a drain port 6 on the bottom surface, ozone water 2 is supplied from a supply pipe 1 installed above the wafer 3, and the wafer 3 is ozone water in the dipping tray 4. 2, the ozone water 2 is drained from the drainage port 6.

  The ozone water cleaning BOX 7 is preferably connected to an exhaust mechanism capable of processing ozone gas, and further provided with an openable / closable shutter for taking in and out the wafer.

  The immersion tray 4 can be provided with a cradle 5 as shown in FIG. 1 as a holding means for placing the wafer 3 horizontally. Such a cradle 5 is preferably one that can move up and down to immerse the wafer reliably.

  Further, the drainage port 6 included in the immersion tray 4 is not particularly limited, and examples thereof include a drainage port 6 formed at a position immediately below the center of the wafer.

  Furthermore, the supply pipe installed above the wafer may be above the wafer, but is installed above the center of the wafer in order to efficiently flow ozone water over the entire surface of the wafer. It is preferable. Of course, the supply pipe may be fixed in the center or may be swung in the radial direction of the wafer. Furthermore, a plurality of supply pipes can be installed.

  In the mechanism as described above, the ozone water supplied from the supply pipe above the wafer flows from the center of the wafer surface toward the outer periphery, and further toward the drainage port at the center of the lower part of the immersion tray. The structure flows through the immersion tray on the back side of the wafer. Further, the ozone water may be drained by overflowing from the edge of the immersion tray.

  As ozone water used here, 5-20 ppm is preferable. If it is 5 ppm or more, a sufficient cleaning effect can be obtained, and if it is 20 ppm or less, an economical disadvantage does not occur, which is preferable.

  The supply amount of ozone water supplied to the wafer surface is preferably 3 to 5 liters per minute. If it is 3 liters or more, a sufficient cleaning effect can be obtained, and if it is 5 liters or less, it is preferable because there is little economic loss.

Below, an example of a series of ozone water washing | cleaning flows of the washing | cleaning method using the ozone water of this invention using the above washing | cleaning apparatuses 10 is shown.
1. The wafer 3 is loaded by the robot arm.
2. Open the ozone water cleaning BOX7 shutter.
3. The wafer 3 is inserted on the immersion tray 4.
4). The wafer 3 is placed on the cradle 5 and the robot arm is retracted.
5. Close the shutter of the ozone water cleaning BOX7.
6). Supply of ozone water is started from the supply pipe 1.
7). The cradle 5 is lowered and held by the cradle 5, and the cradle 5 is lowered and immersed in the ozone water in the immersion tray 4.
8). Hold the immersed state while supplying ozone water for the specified time.
9. Stop supplying ozone water.
10. Start supplying pure water.
11. The wafer 3 is immersed in pure water, and the ozone water is washed away.
12 Raise the cradle 5.
13. Stop supplying pure water.
14 Open the ozone water cleaning BOX7 shutter.
15. The wafer 3 that has been cleaned with ozone water is collected by a robot arm.
16. Returning to the first step, a new wafer is cleaned, or the ozone water cleaning BOX shutter is closed to end the process.

  If it is the cleaning method illustrated above, a small amount and low concentration ozone water can be used, and it can be set as the cleaning method which does not have a cleaning nonuniformity and does not require a complicated apparatus structure.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.

The Examples and Comparative Examples were evaluated by performing the following comparative test flow.
1. 1. Wafer polishing 2. Ozone water cleaning Rinse 4. SC1 (ammonia / hydrogen peroxide solution)
5. Rinse 6. Drying 7. Measurement by surface defect inspection apparatus SP2 (manufactured by KLA-Tencor) In the comparative test, the surface of the wafer was measured by a surface defect inspection apparatus SP2 manufactured by KLA-Tencor, and a method for comparing the Haze maps of SP2. .
The cleaning methods shown in the following examples and comparative examples correspond to the ozone water cleaning in the above step 2.

[Example 1]
A silicon wafer having a diameter of 300 mm was cleaned using a cleaning apparatus as shown in FIG. That is, the silicon wafer 3 is placed horizontally on a cradle 5 in a dipping tray 4 having a drainage port 6 on the bottom, and 10 ppm of ozone water 2 is supplied from a supply pipe 1 installed above the silicon wafer 3, and silicon The wafer 3 was cleaned by immersing it in the ozone water 2 with the immersion tray 4, and the ozone water 2 was drained from the drain port 6 for cleaning.

[Comparative Example 1]
A silicon wafer having a diameter of 300 mm was cleaned using an apparatus for cleaning by immersing a plurality of wafers vertically in a cleaning tank filled with ozone water as shown in FIG. That is, cleaning was performed by supplying ozone water 102 from the supply pipe 101 installed at the bottom of the cleaning tank so as to uniformly touch the surface of the silicon wafer 103 and draining it from the upper part of the cleaning tank by overflow. . In order to maintain the concentration, 20 ppm of ozone water 102 was constantly supplied from the ozone water production apparatus toward the supply pipe 101. Further, as the silicon wafer 103, a wafer whose orientation, number and size were adjusted in accordance with the structure and holding method of the cleaning tank was used.

[Comparative Example 2]
A silicon wafer having a diameter of 300 mm was cleaned using an apparatus for horizontally cleaning the wafers one by one as shown in FIG. That is, the silicon wafer 203 is placed horizontally in a sealed ozone water cleaning BOX (not shown) in order to prevent the diffusion of ozone gas, and 20 ppm ozone from a shower nozzle type supply pipe 201 attached to the upper part and the lower part. Cleaning was performed by spraying water 202 onto the silicon wafer 203. At this time, a cleaning process was performed with a layout so that ozone water could be sprayed on the entire wafer surface from the upper and lower 19 shower nozzles.

[Comparative Example 3]
A silicon wafer having a diameter of 300 mm was cleaned using an apparatus for cleaning while rotating the wafers one by one as shown in FIG. That is, in a chamber (not shown) in which exhaust gas and drainage can be performed to prevent the diffusion of ozone gas, the silicon wafer 303 is held on a cradle 305 that can be rotated, and the upper portion of the chamber is rotated while the silicon wafer 303 is rotated. Then, 10 ppm of ozone water 302 was supplied to the silicon wafer 303 from the supply pipe 301 attached to the lower part and cleaned. At this time, the wafer rotation was performed at 100 rpm to 1500 rpm. The cleaning liquid shaken off from the wafer by the rotation is received by the partition wall 306 so as not to be scattered.

実施例１と比較例３においては、ＳＰ２のＨａｚｅマップにオゾン洗浄によるムラが発生しなかったが、比較例１は洗浄槽内のオゾン水濃度分布に起因するＨａｚｅムラが発生し、比較例２においてはシャワーによるＨａｚｅムラが発生した。 The comparative test results of Example 1 and Comparative Examples 1 to 3 are shown in Table 1 and FIG.

In Example 1 and Comparative Example 3, unevenness due to ozone cleaning did not occur in the Haze map of SP2, but in Comparative Example 1, Haze unevenness due to ozone water concentration distribution in the cleaning tank occurred, and Comparative Example 2 In Haze, Haze unevenness due to shower occurred.

  In Comparative Example 1, since ozone water itself constantly decreases in concentration due to autolysis and reaction, it is unavoidable that concentration distribution occurs in the washing tank, and the concentration of ozone water near the outlet of the supply pipe is high. It is conceivable that the place away from the supply pipe or the place where it is difficult to be replaced by the supplied ozone water has a decrease in the ozone water concentration, causing a gradient in the ozone water concentration in the cleaning tank.

  In Comparative Example 2, the ozone water is released from the ozone water as ozone gas due to the release from the piping pressure until the ozone water reaches the wafer surface from the shower nozzle, leading to a significant decrease in concentration. It is conceivable that the ozone water shower was applied unevenly, and cleaning unevenness occurred in a large portion and a small portion.

  In Comparative Example 3, the wafer was not unevenly cleaned with ozone water, but the wafer rotation mechanism, the wafer chuck mechanism that moved up and down, the ozone water supply mechanism, the spin chamber structure, and the like became complicated and expensive. The cost of the equipment has been greatly increased.

  From the above, if the cleaning method using the ozone water of the present invention, a small amount and low concentration of ozone water can be used, there is no cleaning unevenness, and cleaning that does not require a complicated apparatus configuration is required. It became clear that it could be done.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

DESCRIPTION OF SYMBOLS 1 ... Supply pipe, 2 ... Ozone water, 3 ... Wafer, 4 ... Dipping tray, 5 ... Receiving base,
6 ... Drainage port, 7 ... Cleaning BOX, 10 ... Cleaning device.

Claims (4)

A wafer cleaning method using ozone water,
The wafer is placed horizontally on a dipping tray having a drain outlet on the bottom, the ozone water is supplied from a supply pipe installed above the wafer, and the wafer is immersed in the ozone water with the dipping tray. The cleaning method using ozone water, wherein the ozone water is drained from the drain port.   The cleaning method using ozone water according to claim 1, wherein the supply pipe is disposed above a center portion of the wafer. A wafer cleaning apparatus using ozone water,
A holding means for horizontally placing the wafer, and an immersion tray having a drain of the ozone water on the bottom surface;
A cleaning apparatus comprising: a supply pipe for supplying the ozone water from above the wafer.   The cleaning apparatus according to claim 3, wherein the supply pipe is installed above a central portion of the wafer.

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