JP3495121B2 - Cleaning method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning method and apparatus, for example, from general cleaning represented by degreasing of machine oil to wet processing in a semiconductor manufacturing process which requires ultra-precision and high cleanliness. It is suitable for wet cleaning.

[0002]

2. Description of the Related Art Conventionally, for example, in a wet process of semiconductor manufacturing, when a semiconductor substrate is subjected to chemical cleaning or subsequent ultrapure water rinsing cleaning, the ultrasonic vibration element is disposed at the bottom of the processing tank in the chemical cleaning tank, and the top lid is Was installed solely to prevent the escape of chemical vapors and mists.
Moreover, in the rinse tank, the washing process is usually performed without using the upper lid.

However, in the process of reviewing the cleaning method by the present inventors to develop a higher performance semiconductor device, oxygen gas mixed in the cleaning liquid from the atmosphere causes cleaning failure or forms an oxide film. It has been found that the characteristics of the device are degraded. That is, for the first time, we learned that the cleaning liquid must be completely shielded from the atmosphere. In addition, if you try to irradiate ultrasonic waves from the liquid surface side using the overflow type processing tank that has been used in the conventional wet processing system, a straight flow (flow from top to bottom) and overflow generated from the ultrasonic waves will occur. It was also found that the in-liquid flow (flow from the bottom to the top) in the mold treatment tank interferes with each other and a sufficient effect cannot be obtained. Further, in order to avoid this, irradiation of ultrasonic waves from the side surface can be considered, but in addition to obstructing the flow in the liquid, there is a drawback that the ultrasonic waves are blocked by a cleaning jig such as a carrier. The present invention is
It was completed based on these findings.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a cleaning method and apparatus which requires a very short cleaning time and has a high cleaning effect.

[0005]

The first gist of the present invention is as follows.
A uniform flow of the cleaning liquid is formed from the top to the bottom of the cleaning tank, and ultrasonic waves are irradiated from the upper part of the cleaning tank toward the object to be cleaned installed in the cleaning tank for cleaning. Exists in the cleaning method. A second gist of the present invention is a drawing-type cleaning tank for forming a uniform cleaning liquid flow from the top to the bottom of the tank,
The ultrasonic cleaning device has an upper lid for shutting off the cleaning liquid from the atmosphere, and an ultrasonic vibrating element arranged on the upper lid. While the cleaning liquid is allowed to flow downward toward an object to be cleaned installed in the cleaning tank, ultrasonic waves are applied. Is present in the downward direction to wash the article to be washed.

[0006]

According to the present invention, the ultrasonic wave oscillating section is installed on the upper part of the cleaning tank to irradiate the ultrasonic wave downward, and the downward flow of the cleaning liquid is formed by the extracting method, so that the ultrasonic wave has a straight flow effect. The synergistic effect with and promotes a uniform downward flow of the cleaning liquid in the cleaning tank, and at the same time ultrasonic waves break the hydrogen bonds of water molecules, reducing the size and viscosity of the water clusters. Is expected to improve significantly. As a result, it is possible to shorten the chemical cleaning or ultrapure water rinsing time and reduce the amount of ultrapure water used.

Further, in the present invention, since the upper lid is installed in the cleaning tank, it becomes possible to perform the chemical cleaning and the rinsing of the substrate in an environment in which the mixing of oxygen from the atmosphere is eliminated. For this reason, the formation of an oxide film during the chemical cleaning and rinsing steps can be completely suppressed, and uneven cleaning can be eliminated. Especially in the case of a semiconductor substrate, the ultrasonic frequency is set to 0.8.
It is preferably set to 10 MHz. At frequencies in this range, hydrogen radicals are generated by breaking hydrogen bonds in water, which attack the substrate and can reduce TOC. Moreover, since the water clusters also become smaller, physical properties such as viscosity also change. Further, since the removal of the ultrafine particles by the acceleration of vibration is promoted, the liquid permeation into the ultrafine patterns such as holes and trenches in the manufacturing process of the semiconductor device is promoted, so that the cleaning and the chemical treatment can be performed more completely. Therefore, the device characteristics, pattern accuracy, and the like are improved, and it becomes possible to realize a device with higher performance.

However, in the normal cleaning without a very fine pattern, the frequency of ultrasonic waves is from 10 KHz to
800 KHz is preferably used. In the present invention, as a method for removing the dissolved gas in the cleaning liquid, for example, a method in which one of the UF (ultrafiltration) membranes is evacuated to extract the dissolved gas in the other cleaning liquid is simple and preferably used. . The method is not limited to this, and a method of ejecting the dissolved gas by spraying the cleaning liquid under reduced pressure may be used.

Further, in the present invention, the ultrasonic vibrating element is attached to the upper lid for shutting off the cleaning liquid from the atmosphere. However, as long as the ultrasonic wave can be irradiated from the upper side to the lower side, for example, the upper part of the cleaning tank main body can be provided. You may arrange. Since the cleaning liquid comes into contact with the atmosphere when opening and closing the upper lid, it is preferable not to contact the atmosphere even for a short time. For this purpose, an inert gas ejection port can be provided in the upper part of the cleaning tank to form and seal an inert gas air curtain. As the inert gas, N ₂ gas or Ar gas having impurities of 1 ppb or less is preferably used.

The present invention is most suitable for dilute hydrofluoric acid cleaning or ultrapure water rinse cleaning after dilute hydrofluoric acid cleaning of a semiconductor substrate such as a silicon wafer or a thin film semiconductor substrate such as a thin film transistor substrate.

[0011]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. (Examples 1 and 2) FIG. 1 shows an example of the cleaning tank of the present invention.

FIG. 1 shows a rinse cleaning tank used for rinse cleaning after hydrofluoric acid cleaning, and unlike a conventional overflow, it has a drawing-out type tank structure in which a cleaning solution is flown downward, and is used as a cleaning material is put in and taken out. , It has an upper lid that opens and closes by an automatic vertical slide system. This is a cleaning tank in which an ultrasonic vibration element is arranged under the upper lid and ultrasonic waves can be emitted from above the cleaning tank.

In FIG. 1, reference numeral 100 denotes a cleaning tank main body and 10
1 is a top lid with an automatic opening and closing mechanism that has a built-in ultrasonic vibration element,
102 is an ultrasonic vibration element, 103 is a pressure dispersion control plate, 1
04 is a silicon wafer, 105 is a wafer carrier, 10
Reference numeral 6 is a pipe for N ₂ gas sealing for covering the liquid surface with N ₂ gas when the upper lid is opened to shut off from the atmosphere, 107 is a water supply amount control valve, 108 is a drainage amount control valve, and 109 is a UF degassing device.

When the flow control valves 107 and 108 control the amounts of water supply and drainage to be the same, the liquid level is kept constant. This constant liquid surface, the N ₂ gas ejected from the N ₂ gas seal pipe 106 disposed around the vessel,
Since the liquid surface is covered with N ₂ gas, mixing of O ₂ gas in the atmosphere is prevented even when the upper lid is open. The pressure dispersion control plate 103 is arranged for the purpose of making the flow in the liquid a laminar flow.

An upper lid 10 having a built-in ultrasonic vibration element 102
Immediately before 1 is closed, the ejection of N ₂ gas from the N ₂ gas sealing pipe 106 is stopped, the upper lid 101 directly contacts the liquid surface, and then the ultrasonic vibration element 102 is operated to irradiate ultrasonic waves. The upper lid 101 is automatically opened and closed as the wafer carrier is taken in and out. When ultrapure water is supplied, an inert gas such as N ₂ is usually mixed in the ultrapure water up to near saturation in order to prevent dissolved oxygen. When megasonic is irradiated to such ultrapure water, the inert gas such as N _{2 in} the liquid is degassed to form bubbles in the water, and there is an adverse effect such as adhesion to the wafer and uneven cleaning. An inert gas such as N ₂ is removed by a deaerator 109 for preventing the above.
This deaeration device is a combination of a UF module and a vacuum pump, and has a particle removal effect in addition to a deaeration effect.

The ultrasonic vibrating element 102 of this embodiment is
The vibration element has a frequency of 950 kHz and a maximum output of 300 W. After the treatment with 0.5% hydrofluoric acid, the wafer was subjected to a spray shower treatment, and then rinsed with ultrapure water in the cleaning tank shown in FIG. At this time, Table 1 shows the results obtained by examining the relationship between the time required for the resistivity of the rinse waste liquid to return to the original resistivity of ultrapure water (18.2 MΩ · cm) and the flow rate of ultrapure water. .

For comparison, when ultrapure water that has not been degassed by the UF degassing apparatus 109 in FIG. 1 is used (Example 2), and when megasonic is not irradiated in FIG. Comparative Example 1), when the conventional overflow type shown in FIG. 2 is used for cleaning using a cleaning device in which an ultrasonic transducer is arranged at the bottom of the cleaning tank (Comparative Example 2), and no megasonic irradiation is performed in FIG. The same experiment was performed for the case (Comparative Example 3). The results of these comparative examples are also summarized in Table 1.

[0018]

[Table 1] As is apparent from Table 1, it is understood that the treatment time of ultrapure water rinsing can be greatly shortened by using the cleaning apparatus of the present embodiment in which megasonic is irradiated during the rinse cleaning and the cleaning liquid is flown from top to bottom. . Further, the treatment time can be further shortened by removing the dissolved gas in the ultrapure water. That is, the amount of ultrapure water used can be reduced, and the running cost for cleaning can be reduced.

Next, using the cleaning apparatus of FIG. 1, the effect of cleaning the fine particles of the UF type deaerator and megasonic was examined. The results are shown in Table 2. Here, the cleaning effect was confirmed by intentionally adhering fine particles of city water, fine particles of SiO ₂ latex, and fine particles of polystyrene latex to prepare a sample.

[0020]

[Table 2] As shown in Table 2, it was found that the effect of megasonic particle removal is large, and that the effect is further improved by using the UF deaerator together.

(Example 3) Using the cleaning apparatus of Example 1,
Example 1 except that the oscillation frequency of the ultrasonic transducer was changed.
The silicon wafer is rinsed and rinsed in the same manner as the above.
The relationship between the time required to return to (cm) and the flow rate of ultrapure water was investigated. The results are shown in Table 3.

[0022]

[Table 3] As shown in Table 3, in the case of a silicon wafer, 0.8M
It can be seen that the cleaning effect is higher in the range of Hz to 10 MHz.

[0023]

According to the present invention, impurities can be removed more completely in a short time without uneven cleaning. That is,
It becomes possible to achieve a higher degree of cleaning with a smaller cleaning liquid or a rinse amount of ultrapure water. According to the present invention, for example, holes in the manufacturing process of a semiconductor device, liquid penetration into ultrafine patterns such as trenches is promoted and cleaning and chemical solution treatment can be performed more completely, so the device characteristics and pattern accuracy are improved, It is possible to realize a device with higher performance.

Further, various effects such as improvement of various treatments and cleaning effects and reduction of the amount of chemicals / rinse solutions used can be obtained.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a rinse tank according to a first embodiment.

FIG. 2 is a conceptual diagram showing a conventional rinse tank.

[Explanation of symbols]

100, 200 Cleaning tank body, 101 Ultrasonic vibrating element built-in lid, 102, 202 Ultrasonic vibrating element, 103 Pressure dispersion control plate, 104, 204 Silicon wafer, 105, 205 Wafer carrier, 106 N ₂ gas sealing pipe, 107 Water supply control valve, 108 Drainage control valve, 109 UF deaerator.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-2-34923 (JP, A) JP-A-1-304088 (JP, A) Actually open 4-41781 (JP, U) Actually open 6- 52980 (JP, U) Actually open 2-96726 (JP, U) Actually open 63-173389 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B08B 3/12 B08B 3 / 10 H01L 21/304 642

Claims (11)

(57) [Claims] 1. A uniform cleaning liquid flow is formed from the top to the bottom of a cleaning tank, and ultrasonic cleaning is performed from the upper part of the cleaning tank toward an object to be cleaned installed in the cleaning tank. A cleaning method characterized by the above. 2. The frequency of the ultrasonic wave is 10 KHz to 1
The cleaning method according to claim 1, wherein the cleaning frequency is 0 MHz. 3. The cleaning method according to claim 1, wherein the cleaning liquid is one from which dissolved gas has been removed. 4. The cleaning method according to claim 1, wherein the cleaning liquid is shielded from the atmosphere. 5. The cleaning liquid is diluted hydrofluoric acid or ultrapure water rinse liquid after cleaning with diluted hydrofluoric acid, and the cleaning target is a semiconductor or a thin film semiconductor substrate. The cleaning method according to any one of items 1 to 4. 6. A pull-out type cleaning tank for forming a uniform cleaning liquid flow from the top to the bottom of the tank, an upper lid for shutting off the cleaning fluid from the atmosphere, and an ultrasonic vibration element arranged on the upper lid. The cleaning apparatus cleans the object to be cleaned by irradiating ultrasonic waves downward while flowing the cleaning liquid downward toward the object to be cleaned installed in the cleaning tank. 7. The frequency of the ultrasonic vibration element is 0.8.
The cleaning device according to claim 6, which has a frequency of 10 MHz. 8. The cleaning apparatus according to claim 7, wherein the object to be cleaned is a semiconductor substrate or a thin film semiconductor substrate. 9. The ultrasonic transducer element has a frequency of 10 to 10.
The cleaning device according to claim 6, wherein the cleaning device has a frequency of 800 KHz. 10. A degassing device for removing dissolved gas in the cleaning liquid is provided.
9. The cleaning device according to any one of 9 above. 11. The inert gas jetting port for sealing is arranged above the cleaning tank so that the cleaning liquid does not come into contact with the atmosphere when the top lid is opened and closed.
The cleaning device according to any one of 1.