JPH054155B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a steam cleaning method and a cleaning apparatus for semiconductor wafers, various optical components or electronic components, or jigs for manufacturing them, and particularly relates to a cleaning device. The present invention relates to a steam cleaning method, a steam cleaning drying method, and a steam cleaning/drying device that enable highly purified steam to be used for cleaning and have high cleaning effects. [Prior Art] In recent years, the degree of semiconductor integration has significantly improved, and as a result, the cleanliness required for the surface of semiconductor wafers has also become higher. March 19, 1985
Ultra-LSI Ultra Clean Technology Symposium No. 2 "Ultra-pure Water/High-Purity Chemical Supply System Proceedings" 399-419 sponsored by the Semiconductor Fundamental Technology Research Group held at the Tokyo Institute of Invention Hall from 21st to 21st
The page contains detailed information on wafer cleaning and drying technology. As is clear from the above-mentioned literature, semiconductor wafers are generally cleaned using solvents (triclene, acetone,
H ₂ O ₂ −NH ₄ OH mixture, etc.), and acids and alkalis (HF, H ₂ O ₂ −
Contaminants are sequentially washed away using NH ₄ OH, HCl-H ₂ O ₂ mixture, etc.), and finally washed with ultrapure water, and then the water droplets of the ultrapure water are removed (drying).
Then it is sent to the next process. The purity of the ultrapure water used here is high, with a specific resistance of 18MΩ・cm,
Maintains water quality with TOC of 50 ppb or less and 50 particles/ml of 0.1 μm or larger. However, even if the ultrapure water is used for cleaning, if the water droplets are not removed properly, a number of defective products will result. Therefore, methods for removing water droplets (drying) have also been devised. Conventional water droplet removal (drying) methods include using hot air, rotating the substrate after washing with water and mechanically scattering water droplets using the centrifugal force, and using organic solvent vapor (e.g. isopropyl alcohol) to remove water and the solvent. There are methods that dry the solvent after replacing it with the hot air drying method, spin drying method,
This method is called the IPA vapor drying method, and is used in the actual wafer cleaning process. The current method of cleaning a chemical solution using ultrapure water is to fill the wafer with ultrapure water and immerse the wafer while allowing it to overflow, thereby displacing the water and the chemical solution. In addition, recently, a method of cleaning using vaporized water by heating water has also been reported. Incidentally, known examples related to this type of method include:
In addition to the above-mentioned documents, JP-A-61-174982;
No. 61-138582, JP-A-61-138583, JP-A-61-
There are publications such as 200885. [Problems to be solved by the invention] When cleaning semiconductor wafers, etc., all of the above-mentioned cleaning and drying techniques end up with impurities, such as fine particles contained in the solution, on the surface of the object to be processed (object to be cleaned). It is desirable that no dissolved substances remain. However, the above-mentioned conventional techniques are insufficient in these respects, and there is a risk that impurities may remain. That is, in the hot air drying method, since water droplets adhering to the substrate surface are evaporated by hot air, there is a risk that fine particles and dissolved components contained in the water droplets will precipitate, ultimately leaving impurities on the wafer surface. Similarly, in the spin drying method, it is impossible to remove all water droplets, so when the water droplets on the wafer surface, especially in the fine grooves, dry,
Similar to the hot air drying method, there is a risk that impurities may remain on the surface of the object to be cleaned. In addition, in the IPA steam drying method, the water actually used for cleaning is replaced with IPA, so the effect of impurities in pure water is small, but it is also possible that impurities in IPA may adhere due to IPA mist scattering, and water and IPA may
The problem arises of replacement with . In addition, in the chemical cleaning process of wafers with ultrapure water before the drying process, a large amount of ultrapure water overflows and is replaced with the chemical solution using the immersion method. The cleaning effect is not easily achieved in the grooves, and as the degree of integration increases, the problem arises that impurities tend to remain. The steam cleaning method also has a problem in that impurities in the steam adhere and remain on the surface of the object to be treated. An object of the present invention is to provide a steam cleaning method using a highly purified steam condensate that can reduce the amount of impurities remaining on the surface of a workpiece compared to conventional methods of immersing the workpiece in ultrapure water and steam cleaning methods. and to provide a steam cleaning and drying method and a steam cleaning and drying apparatus. [Means for Solving the Problems] The gist of the steam cleaning method, steam cleaning drying method, and steam cleaning drying apparatus according to the present invention is described in claims 1, 7, and 11. The common feature of these inventions is that the cleaning liquid is heated and vaporized, and the mist that accompanies the vapor is removed by passing through a microporous chamber membrane to produce highly purified vapor. After that, it is condensed, and the condensed liquid is brought into contact with the object to be treated to clean the surface of the object to be treated. The steam that comes into contact with the object to be processed is deprived of latent heat by the object and condenses, thereby serving to clean the object. As the cleaning liquid, water or an organic solvent insoluble in water can be used. Objects to be processed to which the cleaning method of the present invention can be applied include semiconductor wafers, various optical parts and electronic parts including optical disks and magnetic disks, and jigs for manufacturing them. It is desirable to use ultrapure water as the water used for steam cleaning of semiconductor wafers. When the present invention is applied to cleaning semiconductor wafers, it is desirable to apply the present invention to semiconductor wafers that have just been treated with a chemical solution, or to semiconductor wafers that have been treated with a chemical solution and then immersed in ultrapure water to wash off the chemical solution. When a semiconductor wafer is immersed in ultrapure water for cleaning, there is a risk that the fine particles contained in the ultrapure water may enter the grooves of the semiconductor wafer and remain. However, by performing the steam cleaning of the present invention afterwards, the remaining impurities can be washed off. In the steam cleaning method of the present invention, when water is used as the cleaning liquid, it is desirable to use a hydrophobic porous membrane as the porous chamber membrane. When using a water-insoluble organic solvent as the cleaning liquid, it is desirable to use a hydrophilic porous membrane as the porous membrane. The present invention vaporizes the cleaning liquid and removes the mist that accompanies the vaporized vapor, and the vapor no longer contains non-volatile fine particles, or even if it does, it contains very few non-volatile particles. Therefore, the idea is that cleaning using this steam can significantly reduce the amount of impurities remaining. The mist accompanying the steam can be removed by using a hydrophobic porous membrane if the steam is water vapor, and can be removed by using a hydrophilic porous membrane if the steam is an organic solvent insoluble in water. Although it is possible to use the condensed water of the steam that has passed through the porous membrane for cleaning, it is possible that components may be leached from the container etc. when condensed. It is best to bring it into contact with. Conventional cleaning methods in which a workpiece is brought into contact with ultrapure water are not intended to and cannot remove fine particles contained in ultrapure water. Conventional steam cleaning methods are also not intended to remove impurities in the mist that accompanies the steam. [Function] In the present invention, for example, a chemical adhering to the surface of a semiconductor wafer after chemical cleaning is replaced and cleaned by water vapor passing through a hydrophobic porous membrane. By using a hydrophobic porous membrane, it is possible to completely remove the mist that accompanies water vapor.
ammonia, CO ₂ gas, etc.). Therefore, when water vapor condenses on the semiconductor wafer surface, all nonvolatile components are removed, so no impurities remain on the wafer surface after drying.
In particular, when drying using superheated steam of the same steam after steam cleaning according to the present invention, the TOC component is re-evaporated at a temperature higher than the evaporation temperature, so even if the TOC component is liquefied, it will evaporate, resulting in nothing remains. Furthermore, since water vapor is used, it is effective for cleaning small parts that can easily get into the grooves of the object to be treated. The steam cleaning method of the present invention is a method in which steam from which mist has been removed is condensed on the surface of the object to be treated, and contaminants adhering to the object to be treated are washed away with condensed water. When the steam condenses, the object to be treated absorbs the latent heat of the steam and its temperature increases. If the temperature of the object to be treated rises too much during the cleaning process, the steam will no longer condense and the cleaning process will be interrupted. Therefore, during the cleaning process, it is desirable to perform forced cooling so that the surface of the workpiece is always maintained at the steam condensation temperature. As an example of this forced cooling method, it is desirable to form a circulation path for a refrigerant, such as water, in the substrate on which the object to be processed is mounted, and to flow the refrigerant through this path. In the cleaning method of the present invention, the water vapor after removing the mist may contain volatile components such as organic substances, ammonia, CO ₂ gas, and the like. Although it is thought that there is almost no possibility that volatile components will remain on the surface of the object to be treated after cleaning, it is unlikely that such volatile components will be present in water vapor. For this reason, it is desirable to remove volatile components in advance, and as a means to do this, the cleaning solution is heated to boiling to remove volatile components before it is vaporized and passed through the porous membrane. It is desirable to perform a process of volatilizing and removing it.
By performing pre-treatment to remove volatile components in this way, it becomes possible to clean the object to be treated using high-purity steam that is substantially free of volatile components and non-volatile particulates. Note that during steam cleaning, it is desirable to maintain the atmosphere around the object to be treated in a steam-saturated state. Therefore, the object to be treated should be stored in a closed chamber, and during the steam cleaning process, it is desirable to keep the atmosphere around the object to be steam saturated. It is desirable to bleed the condensable gas. In addition, when cleaning semiconductor wafers, as the degree of integration of LSI increases and pattern dimensions become smaller, water that has entered the grooves of the wafer and condensed may not come out due to surface tension. However, in that case, it is desirable to remove the water droplets in the groove to the outside of the groove by repeating the cleaning process several times or by processing the wafer under reduced pressure during the cleaning process. Once the steam cleaning of the present invention has been completed, the next drying step is normally carried out. For semiconductor wafers, etc.
As described in the literature ``Ultrapure Water/High Pure Water Chemical Supply System Proceedings'' page 411, the drying process is essential. In the present invention, it is possible to significantly reduce residual impurities in the steam cleaning process, so conventional hot air drying methods, spin drying methods, and IPA steam drying methods can be applied. As a drying method after steam cleaning of the present invention,
We propose a method using superheated steam that has passed through a hydrophobic porous membrane. Superheated steam, that is, steam heated to a temperature higher than the boiling point, has the effect of drying the condensate on the surface of the object to be treated. Such superheated steam can be easily produced by heating the liquid and providing a heater on one or both sides of the porous membrane before and after the vapor permeates the porous membrane to superheat the vapor. Therefore,
Using superheated steam allows both cleaning and drying steps to be carried out using the same cleaning liquid. Furthermore, it is also possible to carry out both the washing and drying steps using only superheated steam. This will be explained separately using FIG. 2. Note that when drying using superheated steam, the water is difficult to drain, so the chamber containing the object to be treated is evacuated with a vacuum pump to reduce the pressure around the object, or the chamber containing the object to be processed is evacuated using a vacuum pump, or the chamber containing the object to be It is desirable to rotate the treated material and use centrifugal force to drain the water easily. [Example] Hereinafter, drawings showing examples of the present invention will be described in detail. The present invention is not limited to these examples. Embodiment 1 FIG. 1 shows a basic embodiment of a cleaning device according to the present invention. Here, a case will be explained in which water is used as the cleaning liquid. Steam cleaning device 10 according to the present invention
0 is composed of a steam generating section 111, a condensing cleaning section 112, and a hydrophobic porous membrane 101 existing therebetween. The raw water is sent from the raw water inlet 105 to the steam generating section 111, heated by the heater 102, and evaporated. The generated water vapor 103 passes through the hydrophobic porous membrane 101, and the accompanying mist is separated at that time. The water vapor that has passed through the membrane condenses on the object to be cleaned (object to be treated) 107, and the object to be cleaned 107 is washed with the condensed water. If the object to be cleaned 107 is left as it is, the temperature will rise and there is a risk that it will not be able to condense. Therefore, the back side is cooled with cooling water 108, and the surface of the object to be cleaned is heated 100 times so that the steam condenses.
It is desirable to keep the temperature below °C. The washed and dirty water is discharged from the drain port 109 to the outside of the washing device. Note that since it is desirable that the inside of the condensing cleaning section be saturated with water vapor, it is desirable to bleed the non-condensable gas through the bleed port 110. According to this example, since cleaning can be performed using water vapor that has passed through the hydrophobic porous membrane, it is possible to effectively clean with a small amount of water, and there is no possibility that impurities will remain on the surface of the object to be cleaned after drying. Very little amount and high cleaning effect can be achieved. Note that the reference numeral 104 indicates the liquid level of the washing water, and the reference numeral 109 indicates the outlet for the washing water. Example 2 FIG. 2 shows an example in which drying using superheated steam is also included. Steam cleaning device 2 of this embodiment
00 is a steam generating section 111, a steam superheating section 20
2. The hydrophobic porous membrane 101 is arranged between the steam superheating section 202 and the washing/drying section 203. Raw water in the steam generating section 111 is heated by the heater 102 to generate steam. The generated water vapor 103 is further turned into superheated water vapor by the superheating heater 207 in the water vapor superheating section 202, and is sent to the cleaning/drying section 203 through the hydrophobic porous membrane 101. Inside the cleaning/drying section 203, the object to be cleaned 107 is installed in a movable washer 208. Washing/drying section 203
The superheated steam sent inside becomes saturated steam while drying water droplets adhering to the surface of the object to be cleaned 107 attached to the mobile washer 208, and the latter half of the cleaning is performed with steam. The movable washer 208 gradually moves toward the hydrophobic porous membrane 101 during cleaning, first passing through a cleaning process, then a drying process, and then exiting the apparatus. The remaining steam passes through the steam circulation system 209 and is sent to the steam superheating section again. The condensed water used for cleaning is drained from the drain outlet 109.
is released outside the device. According to this embodiment, since the object to be cleaned can be washed and dried at the same time in a clean steam atmosphere, the amount of water used can be reduced and effective cleaning can be performed. Embodiment 3 FIG. 3 shows the embodiment shown in FIG. 1 with the addition of a spin cleaning method. Steam cleaning device 300 of this embodiment
consists of a steam generating section 111 and a cleaning/drying section 308, between which a hydrophobic porous membrane 101 is installed. In this example, washing and drying are repeated in batch operations. First, in the cleaning process, raw water is evaporated with a heater 102, and the generated steam 10
3 is filtered through a hydrophobic porous membrane 101 and sent to a washing/drying section 308. A spinner 311 is arranged in the cleaning/drying section 308, and the object to be cleaned 10 is placed on the surface of the spinner 311.
7 is attached and rotated in the direction of the arrow by a rotation motor 307. Water vapor is the object to be cleaned 107
It condenses on top, is removed from the surface by centrifugal force along with surface impurities, and is washed again by fresh water vapor. After being sufficiently washed using the above method, the drying process is started. In the drying process, the steam 103 generated in the steam generating section 111 is further heated by the superheating heater 207 to become superheated steam, and then sent to the cleaning/drying section 308 . In this step as well, by rotating the spinner 311, superheated steam is used to dry the steam, and the steam that has become saturated steam is transferred to the circulation system 31.
0 and is sent to the steam generating section 111 again. If a hydrophobic membrane is installed at the inlet of the circulation system, the mist generated from the spinner can be removed, making it even more effective. According to this embodiment, by using a spinner, water droplets in fine grooves on the surface of the object to be cleaned can be removed, so that the cleaning effect can be further improved. In addition, in FIG. 3, the overheating heater 207 may be provided on the cleaning/drying section side. Embodiment 4 FIG. 4 is a modification of the embodiment shown in FIG. The steam cleaning device of this embodiment has a steam generating section 1
A condensing cleaning section 112 is located above the cleaning section 11, and a partition wall made of a hydrophobic porous membrane 101 partitions the two. When the steam 103 heated and vaporized by the heater 102 passes through the hydrophobic porous membrane 101, accompanying mist is removed, and the steam becomes highly pure steam, which comes into contact with the object to be cleaned 107 and condenses. Cleaning is then performed with condensed water. Condensed water 104a that has fallen from the object to be cleaned collects in a saucer 115. According to this embodiment, the apparatus can be made more compact than the structure shown in FIG. Example 5 An example in which means for removing volatile components in the wash water is provided upstream of the steam generating section will be described. FIG. 5 shows the cleaning device shown in FIG. 1 with a volatile component removal section 500 added thereto. Raw water 501 to be sent to the steam generating section is heated by a heater 502 to boil it to volatilize and remove volatile components contained in the raw water, and then introduced into the steam generating section 111 through the raw water inlet 105. . Although the removal of volatile components depends on the amount of raw water, it is usually sufficient to boil the raw water and then hold it for ten to several tens of minutes. According to this embodiment, cleaning can be performed using very little steam for both volatile and non-volatile components, and the reliability of cleaning can be improved. Embodiment 6 FIG. 6 shows an embodiment of a steam cleaning apparatus in which a vacuum exhaust port is provided in the cleaning/drying section. During steam cleaning, raw water is heated by the heater 102 to generate steam 103, which is passed through the hydrophobic porous membrane 101 and then brought into contact with the object to be cleaned 107, condensed and cleaned with the condensed water. When the cleaning is completed, in addition to the heater 102, the overheating heater 207 is operated to raise the temperature of the steam that has passed through the hydrophobic porous membrane 101 to a temperature higher than the boiling point. In this embodiment, the overheating heater 207 is provided on the washing/drying section 610 side, but it may be provided on the steam generating section side as shown in FIG. The superheated steam 250 has the effect of vaporizing and drying the condensed water on the surface of the object to be cleaned. however,
Drying only with superheated steam at 250°C does not drain water well. Therefore, during the drying process, the cleaning/drying section 610 is depressurized by the vacuum pump 620. This makes it easier for water droplets to scatter on the surface of the object to be cleaned, allowing for better water drainage. Although Examples 1 to 5 above have all been described using water as the cleaning liquid, it goes without saying that they can be similarly applied to cleaning with effective solvents or other chemical solutions. [Effects of the Invention] According to the present invention, highly purified vapor is condensed by completely removing accompanying mist by passing through a porous membrane, and the object to be cleaned is cleaned with the condensed liquid. Therefore, the amount of impurity residue after washing can be significantly reduced. Furthermore, by using the drying process in superheated steam in combination, cleaning and drying can be carried out in the same atmosphere, so there is no external contamination and a high cleaning effect can be obtained. Furthermore, since non-volatile impurities are almost completely removed through membrane distillation, no impurities remain after cleaning and drying, making effective cleaning possible.

[Brief explanation of drawings]

1 to 6 are schematic configuration diagrams showing embodiments of the present invention. 101...Hydrophobic porous membrane, 102...Heater, 103...Water vapor, 107...Object to be cleaned, 1
11... Steam generation section, 112... Condensation cleaning section,
207...Heater for superheating, 250...Superheated steam, 500...Volatile component removal section.

Claims (1)

[Claims] 1. Using a steam cleaning device comprising a cleaning liquid vapor generation chamber partitioned by a microporous membrane and a steam cleaning chamber containing a workpiece to be cleaned, in the cleaning liquid vapor generation chamber. The generated cleaning liquid vapor is transferred to the steam cleaning chamber through a microporous membrane, and at this time, the mist accompanying the cleaning liquid vapor is removed by the microporous membrane, and the cleaning liquid vapor from which the entrained mist has been removed is condensed in the steam cleaning chamber. A steam cleaning method characterized in that the vapor is allowed to adhere to the surface of a workpiece as a condensate, and the surface of the workpiece is cleaned with the condensate. 2. The steam cleaning method according to claim 1, wherein volatile components in the cleaning liquid are removed by pretreatment. 3. In the case where the cleaning liquid vapor is water vapor obtained by evaporating pure water, the microporous membrane is a hydrophobic microporous membrane, according to claim 1 or 2. steam cleaning method. 4. The steam cleaning method according to claim 3, wherein the object to be processed is one of a semiconductor wafer, a magnetic disk, and an optical disk that has been treated with a chemical solution as a pretreatment for the steam cleaning process. 5. Claim 1, wherein the cleaning liquid vapor is vapor obtained by evaporating a water-insoluble organic solvent, and the microporous membrane is a hydrophilic microporous membrane. term or second
Steam cleaning method described in section. 6. Claim 3 or 5, characterized in that the condensate that adheres to the surface of the object to be treated is obtained by forcibly cooling the surface of the object to a temperature at which the vapor condenses. Steam cleaning method described in. 7 Using a steam cleaning/drying device comprising a cleaning liquid vapor generation chamber partitioned by a microporous membrane and a steam cleaning/drying chamber containing the workpiece to be cleaned and dried, the cleaning liquid generated in the cleaning liquid vapor generation chamber is The steam is transferred to the steam cleaning drying material through a microporous membrane, the mist accompanying the cleaning liquid vapor is removed by the microporous membrane, and the cleaning liquid vapor from which the entrained mist has been removed is condensed in the steam cleaning drying chamber. A steam cleaning/drying method characterized in that a condensate is deposited on the surface of a workpiece, the surface of the workpiece is cleaned with the condensate, and then dried using a drying means. 8. The steam cleaning and drying method according to claim 7, wherein the drying means is a heating means for converting cleaning liquid vapor into superheated steam, and the drying is performed using the superheated steam. 9. The drying means is a spinner consisting of a rotating body on which the object to be treated is mounted, and the spinner rotates at high speed to scatter the condensate adhering to the surface of the object to be treated using centrifugal force to perform drying. A steam cleaning and drying method according to claim 7, characterized in that: 10 The drying means is a combination of a heating means for converting the cleaning liquid vapor into superheated steam and a spinner consisting of a rotating body to which the object to be treated is attached. 8. The steam cleaning and drying method according to claim 7, further comprising drying in which adhering condensate is scattered using centrifugal force. 11 A cleaning liquid tank containing a cleaning liquid, a cleaning vapor generation chamber having a heating means for heating the liquid in the tank to generate cleaning liquid vapor, and a cleaning vapor generation chamber disposed adjacent to the cleaning vapor generation chamber, A cleaning steam generation chamber is provided between the cleaning steam generation chamber and the steam cleaning drying chamber, and a steam cleaning and drying chamber that accommodates the object to be treated and cleans the surface of the object with condensed liquid of the cleaning steam. In addition to partitioning the chamber with a microporous membrane that does not allow the mist accompanying the cleaning liquid vapor generated in the chamber to pass through, the steam cleaning and drying chamber is equipped with a drying means to dry and remove the condensate of the cleaning liquid vapor that adheres to the surface of the workpiece. A steam cleaning drying device characterized by: 12. Steam cleaning according to claim 11, characterized in that means for forcibly cooling the surface of the workpiece to a temperature at which steam condenses is provided as means for obtaining a condensate for cleaning the surface of the workpiece. drying equipment. 13. The steam cleaning and drying apparatus according to claim 11, wherein the drying means converts the cleaning liquid vapor into superheated steam using a heating means, and performs drying using the superheated steam. 14 The drying means is a spinner consisting of a rotating body on which the object to be processed is mounted, and the high speed rotation of the spinner scatters the condensate adhering to the surface of the object to be processed using centrifugal force to perform drying. 12. The steam cleaning and drying apparatus according to claim 11, which is a steam cleaning/drying apparatus. 15. The steam cleaning according to claim 11, wherein the steam cleaning drying chamber is provided with non-condensable gas extraction means for keeping the chamber saturated with steam during the cleaning process. drying equipment.