JP2011204958A - Cleaning method and cleaning device - Google Patents

Abstract

The object to be cleaned having a fine structure such as a semiconductor wafer for LSI and a substrate for MEMS is effectively cleaned with gas-dissolved water without causing damage due to cleaning, and the object to be cleaned is highly purified. Turn into.
In a cleaning container, an object to be cleaned is brought into contact with a cleaning liquid (supersaturated gas solution) containing dissolved gas having a saturation solubility or higher at the liquid temperature of the cleaning liquid. Introduce a supersaturated gas solution in the cleaning container, or introduce a cleaning solution in the cleaning container and then introduce a pressurized gas to prepare a supersaturated gas solution in the cleaning container, and then clean the target in the cleaning container. The inside of the cleaning container is depressurized while the object is in contact with the supersaturated gas solution, and the object to be cleaned is cleaned with bubbles of supersaturated dissolved gas generated from the supersaturated gas solution.
[Selection] Figure 1

Description

  The present invention relates to a method and apparatus for effectively cleaning the surface of various objects to be cleaned. The cleaning method and the cleaning apparatus of the present invention are required to have a high degree of cleanliness such as a silicon wafer for semiconductors, a substrate for MEMS (Micro Electro Mechanical Systems), a glass substrate for flat panel displays, a quartz substrate for photomasks, and the like. It is suitable for cleaning electronic materials (electronic parts, electronic members, etc.).

  In order to remove fine particles, organic substances, metals, etc. from the surface of electronic materials such as LSI semiconductor wafers, MEMS substrates, glass substrates for flat panel displays, quartz substrates for photomasks, etc., this is conventionally called the so-called RCA cleaning method. Wet cleaning was performed at high temperature with a concentrated chemical solution based on hydrogen peroxide. The RCA cleaning method is an effective method for removing metal and the like on the surface of electronic materials, but these chemicals are discharged into the waste liquid because a large amount of high-concentration acid, alkali or hydrogen peroxide is used. In addition, a large burden is imposed on neutralization and precipitation in waste liquid treatment, and a large amount of sludge is generated.

  Therefore, gas-dissolved water prepared by dissolving a specific gas in pure water and adding a trace amount of chemicals as necessary has been used in place of high-concentration chemical solutions. Cleaning with gas-dissolved water can reduce the amount of cleaning water used because there are few problems of drug residue on the object to be cleaned and the cleaning effect is high.

  Conventionally, specific gases used for gas-dissolved water as cleaning water for electronic materials include hydrogen gas, oxygen gas, ozone gas, rare gas, and carbon dioxide gas.

  The cleaning effect of gas-dissolved water is higher than that of water that does not dissolve gas, but the cleaning effect of removing fine particles is not sufficiently high. It is necessary to combine ultrasonic cleaning in order to fully develop the expression. For example, Patent Document 1 proposes a cleaning method for cleaning an object to be cleaned while irradiating the cleaning liquid with ultrasonic waves using a cleaning liquid in which hydrogen gas is dissolved in ultrapure water and hydrogen peroxide is added. .

However, since the ultrasonic cleaning equipment is expensive, the cleaning cost increases.
In addition, recent electronic materials have a fine structure that has not been conventionally used, and there is a problem of damage caused to the structure by slight etching with a concentrated chemical solution or ultrasonic waves. In particular, a concentrated chemical solution or ultra-fine solution is used so as not to damage fine structures such as fine pattern grooves and contact holes of LSI semiconductor wafers and fine irregularities of MEMS substrates that have been rapidly developed and put into practical use in recent years. Development of a new cleaning technique that does not use sound waves is desired.

JP 2004-296463 A

  The present invention effectively cleans an object to be cleaned having a fine structure such as a semiconductor wafer for LSI or a substrate for MEMS without using ultrasonic waves, without causing damage due to cleaning, It is an object of the present invention to provide a cleaning method and a cleaning apparatus for highly cleaning these objects to be cleaned.

  As a result of intensive investigations to solve the above problems, the present inventors have dissolved a gas having a saturation solubility or higher in the cleaning liquid used for cleaning, and when this pressure is lowered, the supersaturated dissolved gas is dissolved. When the bubbles become active bubbles and are generated from the cleaning liquid, the scrubbing effect, the impact force of the bubble collision, the adsorption force at the gas-liquid interface, etc., cause the physicochemical cleaning action such as fine particles on the surface of the object to be cleaned and the object to be cleaned. It has been found that the cleaning effect of the gas-dissolved water can be improved without using ultrasonic waves.

  The present invention has been achieved on the basis of such findings, and the gist thereof is as follows.

[1] In the cleaning container, the object to be cleaned is cleaned by bringing it into contact with a cleaning liquid containing dissolved gas having a solubility equal to or higher than the saturation solubility at the liquid temperature of the cleaning liquid (hereinafter, this cleaning liquid is referred to as “supersaturated gas solution”). In the method, the supersaturated gas solution is introduced into the cleaning container, or a pressurized gas is introduced after the cleaning liquid is introduced into the cleaning container, and the supersaturated gas solution is introduced into the cleaning container. A first step of preparing, and in a state where an object to be cleaned is in contact with the supersaturated gas solution in the cleaning container, a second step of reducing the pressure in the cleaning container to generate bubbles from the supersaturated gas solution A cleaning method comprising the steps of:

[2] A cleaning method according to [1], wherein the cleaning step including the first step and the second step is performed a plurality of times.

[3] The cleaning method according to [2], including a third step of replacing the cleaning liquid in the cleaning container between the cleaning step and the next cleaning step.

[4] In any one of [1] to [3], the dissolved gas is one or two selected from the group consisting of nitrogen gas, oxygen gas, carbon dioxide gas, hydrogen gas, ozone gas, clean air, and rare gas. A cleaning method characterized in that it is a seed or more.

[5] The cleaning method according to any one of [1] to [4], wherein the cleaning liquid is pure water or ultrapure water, or pure water or ultrapure water in which a chemical is dissolved.

[6] The cleaning method according to [5], wherein the agent is one or more selected from the group consisting of an alkali, an acid, a chelating agent, and a surfactant.

[7] The cleaning method according to [6], wherein the alkali is ammonia.

[8] In the cleaning container, the object to be cleaned is cleaned by bringing it into contact with a cleaning liquid containing dissolved gas having a solubility equal to or higher than the saturation solubility at the liquid temperature of the cleaning liquid (hereinafter, this cleaning liquid is referred to as “supersaturated gas solution”). A pressure-resistant cleaning container that can be sealed, means for introducing the supersaturated gas solution into the cleaning container, means for depressurizing the cleaning container, and means for discharging the cleaning liquid in the cleaning container The object to be cleaned by reducing the pressure in the cleaning container and generating bubbles from the supersaturated gas solution in a state where the object to be cleaned is in contact with the supersaturated gas solution in the cleaning container. Cleaning apparatus characterized by cleaning.

[9] In the cleaning container, the object to be cleaned is cleaned by bringing it into contact with a cleaning liquid containing dissolved gas having a solubility equal to or higher than the saturation solubility at the liquid temperature of the cleaning liquid (hereinafter, this cleaning liquid is referred to as “supersaturated gas solution”). A pressure-resistant cleaning container that can be sealed, a means for introducing the cleaning liquid into the cleaning container, a pressurized gas is introduced into the cleaning container, and the cleaning liquid is introduced into the cleaning liquid in the cleaning container. A means for containing a dissolved gas having a solubility equal to or higher than the saturation solubility at the liquid temperature; a means for reducing the pressure in the cleaning container; and a means for discharging the cleaning liquid in the cleaning container. A cleaning apparatus, wherein the object to be cleaned is cleaned by reducing the pressure in the cleaning container and generating bubbles from the supersaturated gas solution while being in contact with the supersaturated gas solution.

  According to the present invention, the object to be cleaned can be highly purified by cleaning using gas-dissolved water, efficiently performing resource-saving and low-cost cleaning (claims 1, 8, and 9). .

That is, as described above, when the pressure of the cleaning container containing the supersaturated gas solution is lowered, the supersaturated dissolved gas in the supersaturated gas solution is generated as bubbles according to Henry's law and separated from the cleaning solution. This supersaturated dissolved gas bubble is generated throughout the cleaning container, and becomes an active bubble that effectively acts on the surface of the object in the minute recess of the object to be cleaned.
The amount of bubbles generated and the degree of activity depend on the dissolved gas amount of the supersaturated gas solution (related to the pressurized gas pressure and water pressure at the time of gas injection into the cleaning solution) and the degree of subsequent decompression, Bubbles generated by the decompression gradually increase in volume due to further vaporization of the dissolved gas, coalescence of the bubbles, etc., and rise to the surface of the cleaning liquid and disappear. In the process of bubble generation, growth and levitation associated with this decompression, the physicochemical cleaning action such as bubble scrubbing effect, bubble collision impact force, gas-liquid interface adsorption force, etc. It is affected by sludge substances such as fine particles, and a high cleaning effect can be obtained. Thus, the cleaning action by the bubbles does not cause great damage to the object to be cleaned, and can effectively clean the fine structures such as the LSI semiconductor wafer and the MEMS base.

In the present invention, in the cleaning container, a first step of bringing the object to be cleaned into contact with the supersaturated gas solution, and a second step of reducing the pressure in the cleaning container to generate bubbles from the supersaturated gas solution. A higher cleaning effect can be obtained by repeatedly performing the cleaning step consisting of the steps a plurality of times (claim 2).
Further, in the case where the cleaning process is repeated as described above, the cleaning effect is further improved by replacing the cleaning liquid between the cleaning processes.

  In the present invention, the dissolved gas is preferably one or more selected from the group consisting of nitrogen gas, oxygen gas, carbon dioxide gas, hydrogen gas, ozone gas, clean air, and argon gas (Claim 4).

  Moreover, it is preferable to use pure water or ultrapure water, or a solution in which a drug is dissolved in this as a liquid for dissolving a gas (Claim 5), and as this drug, an alkali, an acid, a chelating agent, and a surface activity One or more selected from the group consisting of agents, particularly ammonia is preferable, and by including such agents, even better cleaning effects can be obtained (claims 6 and 7).

It is a block diagram which shows an example of embodiment of the washing | cleaning apparatus of this invention.

  Hereinafter, embodiments of the cleaning method of the present invention will be described in detail.

[To be cleaned]
Although there is no particular limitation on the object to be cleaned in the cleaning method of the present invention, the present invention has a silicon substrate for semiconductors, a glass substrate for flat panel displays, and a quartz substrate for photomasks because of its excellent cleaning effect. It is suitable for cleaning electronic materials (electronic parts, electronic members, etc.) that require a high degree of cleanliness, such as MEMS substrates. Especially, it has fine patterns and fine irregularities like LSI semiconductor wafers and MEMS substrates. It is effective for an object to be cleaned in which damage during cleaning of the fine structure is a problem.

[First step]
In the present invention, first, a supersaturated gas solution is introduced into a cleaning container containing an object to be cleaned, or after introducing a cleaning liquid into the cleaning container, a pressurized gas is introduced to dissolve the supersaturated gas in the cleaning container. Prepare the solution.
Here, the supersaturated gas solution includes a dissolved gas having a saturation solubility or higher at the liquid temperature of the cleaning solution.

  If the dissolved gas amount of the cleaning liquid is less than the saturation solubility, active bubbles cannot be generated from the cleaning liquid in the subsequent second step, and the excellent cleaning effect according to the present invention cannot be obtained.

If the amount of dissolved gas in the cleaning liquid is higher than the saturation solubility, the cleaning effect tends to be higher. However, if the amount of dissolved gas is excessively increased, the pressure equipment for that purpose and the pressure-resistant structure of the cleaning container will become excessive, which is practical. It ’s not right. Therefore, the dissolved gas amount of the cleaning liquid is preferably 1 to 5 times, particularly 1 to 3 times, particularly 1.5 to 3 times the saturation solubility.
In the following, the multiple of the dissolved gas amount with respect to the saturation solubility is referred to as saturation, for example, “saturation degree 1” if it is equal to the saturation solubility, “saturation degree 2” if it is twice the saturation solubility, If the amount is 3 times the saturation solubility, it is referred to as “saturation degree 3”.

  There is no restriction | limiting in particular as dissolved gas seed | species of a supersaturated gas solution, For example, noble gases, such as nitrogen gas, oxygen gas, a carbon dioxide gas, hydrogen gas, ozone gas, clean air, and argon gas, are mentioned. Only one of these may be dissolved in the cleaning liquid, or two or more of these may be dissolved in the cleaning liquid. When two or more kinds of gases are dissolved in the cleaning liquid, the total degree of saturation may be 1 or more.

When introducing a pre-saturated supersaturated gas solution into a cleaning vessel, there is no particular limitation on the method for dissolving the gas as described above in the liquid to a saturation solubility or higher, but a gas-dissolved membrane module is used. There is a method in which gas is pressurized and supplied to the gas phase chamber and dissolved in the liquid in the liquid phase chamber.
In addition, when preparing a supersaturated gas solution in the cleaning container, as described later, after introducing the cleaning liquid into the cleaning container, the pressurized gas may be introduced into the container.

  As a liquid for dissolving a gas as described above to prepare a supersaturated gas solution (hereinafter sometimes referred to as “raw water”), it is generally possible to clean an object to be cleaned to a required cleanliness level. Pure water or ultrapure water treated to the extent possible is used.

The raw water is preferably degassed water in order to prepare a cleaning solution containing only a specific dissolved gas, and if it is degassed water, the gas is efficiently dissolved to a saturation solubility or higher. This is also preferable in that
The degree of deaeration is preferably 80% or more, desirably 90% or more.
However, raw water degassing is not an essential requirement.
For the deaeration treatment of raw water, a deaeration membrane module can usually be used.

The raw water includes alkaline agents such as ammonia, sodium hydroxide, potassium hydroxide and tetramethylammonium hydroxide, acids such as hydrogen fluoride, hydrogen chloride and sulfuric acid, chelating agents and surfactants. It is also possible to increase the cleaning functionality by adding seeds or two or more. In particular, by adding an alkaline agent such as ammonia and adjusting the pH of the cleaning liquid to 7 or more, preferably 9-14, the object to be cleaned of contaminants such as fine particles separated from the object to be cleaned by cleaning The cleaning effect can be enhanced by an effect such as preventing re-adhesion. The pH adjustment may be performed using an alkaline agent or an alkaline gas. However, it is preferable to use ammonia that is easy to handle and allows easy concentration control. In particular, a good cleaning effect can be obtained by using a cleaning liquid adjusted to pH 7 to 11 by adding ammonia at 1 mg / L or more, for example, about 1 to 200 mg / L. In addition, when the pH of this cleaning liquid is excessively high or the amount of ammonia added is excessively large, there is a risk of damage to the object to be cleaned, which is not preferable.
Addition of a chemical such as ammonia to the raw water may be after the gas is dissolved or before the gas is dissolved.
Moreover, it is preferable to use the high purity goods which do not contain an impurity for these chemicals.

[Second step]
In the present invention, after the first step, the object to be cleaned is in contact with the supersaturated gas solution in the cleaning container, preferably, the entire object to be cleaned is immersed in the supersaturated gas solution, The object to be cleaned is cleaned by reducing the pressure in the cleaning container and generating bubbles from the supersaturated gas solution.
Although there is no restriction | limiting in particular as the grade of this pressure reduction, Generally it is easy to set it as atmospheric pressure.
Thereby, bubbles are generated from the supersaturated gas solution, and the object to be cleaned can be effectively cleaned by the excellent cleaning action.
This second step is usually performed until the generation of bubbles from the cleaning liquid by reducing the pressure in the cleaning container is completed.

[Repeat cleaning process]
The cleaning step comprising the first step and the second step described above can be performed repeatedly to obtain a further excellent cleaning effect.
In this case, the number of repetitions of the cleaning process is not particularly limited, but it is effective to perform the cleaning process 2 to 50 times, particularly about 2 to 10 times. If the number of repetitions is too small, the effect of improving the cleaning effect by repeatedly performing the cleaning step cannot be sufficiently obtained, and if too large, the cleaning cost and the cleaning time are excessive with respect to the cleaning effect.

[Third step]
As described above, when the cleaning process is repeated, it may be performed without replacing the cleaning liquid in the cleaning container, but by replacing the cleaning liquid in the cleaning container, cleaning can be performed with a highly clean cleaning liquid each time. Further, an excellent cleaning effect can be obtained.

The third step of replacing the cleaning liquid is particularly effective in an embodiment in which a supersaturated gas solution is prepared in the cleaning container. In this case, it is preferable to perform the following operation.
(1) After introducing raw water into the cleaning container, a pressurized gas is injected to prepare a supersaturated gas solution in the cleaning container (first step).
(2) Thereafter, the inside of the cleaning container is depressurized to generate bubbles to clean the object to be cleaned (second step).
(3) Next, the cleaning liquid in the cleaning container is discharged out of the cleaning container (third step).
(4) The above steps (1) to (3) are repeated as many times as necessary.

  When replacing the cleaning liquid in the cleaning container, the cleaning liquid introduced into the cleaning container may be the same as the cleaning liquid used in the previous cleaning process, the type of raw water (presence of chemicals), the type of dissolved gas Or the degree of saturation thereof may be different. Further, the third step of replacing the cleaning liquid may be provided only between some cleaning steps, not between all the cleaning steps.

[Finishing cleaning]
In the cleaning method of the present invention, after the second step, after the cleaning liquid in the cleaning container is discharged, raw water not containing dissolved gas, preferably pure water or ultrapure water, is introduced into the cleaning container and discharged again. Finish cleaning (rinse cleaning) may be performed. Further, this rinse cleaning may be performed a plurality of times.

[Dry]
After the cleaning, the object to be cleaned is taken out from the cleaning container and dried. The drying method is not particularly limited, and can be performed by spin drying, IPA drying, IPA paper drying, Marangoni drying, blow drying with nitrogen gas, or the like.

[Cleaning equipment]
Hereinafter, the cleaning apparatus of the present invention and the cleaning method of the present invention using this cleaning apparatus will be described more specifically with reference to FIG. 1 showing an example of the cleaning apparatus of the present invention.

In FIG. 1, reference numeral 10 denotes a pressure-resistant cleaning container, which can be divided into a lid portion 10A and a container portion 10B, and has a structure that can be sealed by contacting these flange portions.
11 and 12 are pipes for introducing a cleaning liquid or rinsing water into the cleaning container 10 from the bottom of the cleaning container 10, and have an open / close valve V ₁ .
Reference numeral 13 denotes a degassing pipe for decompression in the cleaning container 10 that also serves as an overflow pipe for overflowing the cleaning liquid or rinsing water from the top of the cleaning container 10, and has an open / close valve V ₂ .
14 is a gas introduction pipe for introducing pressurized gas into the cleaning vessel 10 has an opening and closing valve V _3.
15 is a discharge pipe for discharging the cleaning liquid draining the wash container via a pipe 12, having an opening and closing valve V _4.

With this cleaning container 10, the object to be cleaned can be cleaned according to the present invention in the following procedure.

(1) Remove the lid 10 </ b> A of the cleaning container 10 and put an object to be cleaned into the cleaning container 10. It is preferable to install the object to be cleaned so that the surface to be cleaned is perpendicular to the liquid surface so that bubbles generated in the cleaning container 10 effectively contact the object to be cleaned.
After putting an object to be cleaned in the cleaning container 10, a lid 10A is attached and the cleaning container 10 is sealed.
(2) With the on-off valves V ₃ and V ₄ closed and the on-off valves V ₁ and V ₂ opened, the raw water of the cleaning liquid is introduced into the cleaning container 10 through the pipes 11 and 12 until it overflows from the pipe 13, and then The on-off valves V ₁ and V ₂ are closed.
(3) as an opening and closing valve V ₃ opened, the pressurized gas is pressed into the cleaning vessel 10 through the pipe 14, by dissolving a gas to prepare a supersaturated gas solution to the saturation solubility or more in the raw water in the cleaning vessel 10, It is referred to as closed then opening and closing valve V _3. The pressure of the pressurized gas at the time of the gas injection is proportional to the degree of saturation of the supersaturated gas solution to be prepared. Usually, the pressurized gas pressure is 0.01 to 2.0 MPa, particularly 0.01. It is preferable to set it to -1.0MPa. If the pressurized gas pressure is too low, the degree of saturation of the supersaturated gas solution is low, so that the cleaning effect is not sufficient. If it is too high, the pressure-resistant structure of the pressurization equipment and the cleaning container becomes excessive.
As (4) off valve V ₂ opened, the washing vessel 10 and vacuum, bubbles are generated from the supersaturated gas solution, washing the object to be cleaned in the cleaning vessel 10.
(5) When the generation of bubbles is completed, the opening / closing valves V ₁ and V ₄ are opened while the opening / closing valve V ₂ is open, and the cleaning liquid in the cleaning container 10 is discharged.
(6) Repeat (2) to (5) as necessary. Alternatively, (5) is performed after repeating (3) and (4).
(7) The on-off valves V ₃ and V ₄ are closed, the on-off valves V ₁ and V ₂ are opened, and rinse water is introduced into the cleaning container 10 through the pipes 11 and 12 until it overflows from the pipe 13. after stopping the supply of the rinse water, by opening the on-off valve V _4, to discharge the rinse water in the washing vessel 10.
This rinse cleaning may also be performed a plurality of times as necessary.

  After the above series of steps is completed, the object to be cleaned is taken out from the cleaning container 10 and dried as described above.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

[Example 1]
With the cleaning apparatus shown in FIG. 1, cleaning experiments were conducted using the following contaminated wafers as objects to be cleaned.

<To be cleaned>
A silicon wafer that has been contaminated with a silica abrasive used for chemical mechanical polishing, which is a part of the semiconductor manufacturing process, and then dried (hereinafter referred to as “contaminated wafer”).

The cleaning procedure is as follows.
(1) The lid 10A of the cleaning container 10 was removed, and the contaminated wafer was put in the cleaning container 10 and fixed so that the surface of the contaminated wafer was vertical, and then the lid 10A was attached and the cleaning container 10 was sealed.
The washing container is a 5 MPa pressure vessel, and its volume is 5L.

(2) Open / close valves V ₃ , V ₄ are closed, open / close valves V ₁ , V ₂ are opened, and ultrapure water is introduced into the cleaning container 10 through the pipes 11, 12 until the pipe 13 overflows, and then The on-off valves V ₁ and V ₂ were closed.
(3) Open / close valve V ₃ is opened, and pressurized nitrogen gas (gas pressure 0.5 MPa) is pressed into the cleaning container 10 through the pipe 14 so that the degree of saturation is 5 in the ultrapure water in the cleaning container 10. dissolved nitrogen gas supersaturated gas solution prepared is then off valve V ₃ and closed in.
(4) as an opening and closing valve V ₂ opened, the washing vessel 10 and vacuum so that the atmospheric pressure, bubbles are generated from the supersaturated gas solution was washed contaminated wafer cleaning vessel 10.
(5) When the generation of bubbles was completed, the on-off valves V ₁ and V ₄ were opened while the on-off valve V ₂ was open, and the cleaning liquid in the cleaning container 10 was discharged.
(6) Close the on-off valves V ₃ and V ₄ , open the on-off valves V ₁ and V ₂ , and introduce ultrapure water as rinse water into the cleaning container 10 through the pipes 11 and 12 until the pipe 13 overflows. and, then, after stopping the supply of the rinse water, the on-off valve V ₄ is opened, and discharge the rinse water in the washing vessel 10.
(7) The cleaned wafer was taken out from the cleaning container 10 and dried by removing water by centrifugal force.
The number of fine particles on the wafer before and after the cleaning was measured using a “WM-1500 defect inspection apparatus” manufactured by Topcon, and the removal rate (number of fine particles before washing−number of fine particles after washing) / number of fine particles before washing × 100) And the results are shown in Table 1.

[Example 2]
In Example 1, the steps (3) and (4) were repeated and performed 5 times in total, and then the contaminated wafer was washed in the same manner except that the step (5) was performed, and the particulate removal rate was similarly examined. The results are shown in Table 1.

[Example 3]
In Example 1, the steps (3) and (4) were repeated, and after 10 times in total, the contaminated wafer was cleaned in the same manner except that the step (5) was performed, and the particulate removal rate was similarly examined. The results are shown in Table 1.

[Example 4]
In Example 1, in the step (2), the contaminated wafer was cleaned in the same manner except that 1 mg / L ammonia water (pH 9.4) in which ammonia was dissolved in ultrapure water was used. The particle removal rate was examined and the results are shown in Table 1.

[Example 5]
In Example 4, the steps (3) and (4) were repeated, and after 5 times in total, the contaminated wafer was cleaned in the same manner except that the step (5) was performed, and the particulate removal rate was similarly examined. The results are shown in Table 1.

[Example 6]
In Example 4, the steps (3) and (4) were repeated, and after 10 times in total, the contaminated wafer was washed in the same manner except that the step (5) was performed, and the particulate removal rate was similarly examined. The results are shown in Table 1.

[Example 7]
In Example 5, the contaminated wafer was cleaned in the same manner except that the nitrogen gas pressure in step (3) was 1.0 MPa, and a supersaturated gas solution having a saturation degree of 10 was used, and the particulate removal rate was similarly examined, The results are shown in Table 1.

[Example 8]
In Example 5, the contaminated wafer was washed in the same manner except that the nitrogen gas pressure in step (3) was 1.5 MPa, and a supersaturated gas solution with a saturation level of 15 was obtained, and the particulate removal rate was similarly examined, The results are shown in Table 1.

[Comparative Example 1]
In Example 1, the contaminated wafer was cleaned in the same manner except that steps (3) and (4) were omitted, and the particle removal rate was similarly examined. The results are shown in Table 1.

  From Table 1, it can be seen that by repeating the gas injection and pressure reduction, the fine particles on the contaminated wafer can be efficiently washed and removed without using ultrasonic waves. It can also be seen that when ammonia is added to the cleaning liquid, the re-adhesion of the fine particles once peeled off from the contaminated wafer is prevented, and the cleaning effect is further improved.

[Example 9]
A contaminated wafer similar to that cleaned in Example 1 was cleaned using the cleaning apparatus shown in FIG. 1 according to the following procedure. Similarly, the particle removal rate was examined, and the results are shown in Table 2.

(1) In the same manner as in Example 1, a contaminated wafer was placed in the cleaning container 10 and fixed.
(2) Open / close valves V ₃ , V ₄ are closed, open / close valves V ₁ , V ₂ are opened, and 1 mg / L ammonia water (pH 9.4) passes through pipes 11, 12 and overflows from pipe 13 After introducing into the cleaning container 10, the on-off valves V ₁ and V ₂ were closed.
(3) Open / close valve V ₃ is opened, and pressurized nitrogen gas (gas pressure 1.0 MPa) is pressed into the cleaning container 10 through the pipe 14 so that the ammonia water in the cleaning container 10 has a saturation level of 10. dissolved nitrogen gas supersaturated gas solution prepared, then, the opening and closing valve V ₃ was closed.
(4) as an opening and closing valve V ₂ opened, the washing vessel 10 and vacuum so that the atmospheric pressure, bubbles are generated from the supersaturated gas solution was washed contaminated wafer cleaning vessel 10.
(5) When the generation of bubbles was completed, the on-off valves V ₁ and V ₄ were opened while the on-off valve V ₂ was open, and the cleaning liquid in the cleaning container 10 was discharged.
(6) Close the on-off valves V ₃ and V ₄ , open the on-off valves V ₁ and V ₂ , and introduce ultrapure water as rinse water into the cleaning container 10 through the pipes 11 and 12 until the pipe 13 overflows. and, then, after stopping the supply of the rinse water, the on-off valve V ₄ is opened, and discharge the rinse water in the washing vessel 10.
(7) The cleaned wafer was taken out of the cleaning container 10 and dried in the same manner as in Example 1.

[Example 10]
In Example 9, the steps (2) to (5) were repeated a total of two times, and then the contaminated wafer was cleaned in the same manner except that the step (6) was performed, and the particulate removal rate was similarly examined. The results are shown in Table 2.

[Example 11]
In Example 9, the steps (2) to (5) were repeated, and after 5 times in total, the contaminated wafer was washed in the same manner except that the step (6) was performed, and the particulate removal rate was similarly examined. The results are shown in Table 2.

  From Table 2, it can be seen that the cleaning effect is further improved by not only repeating the gas injection and pressure reduction but also exchanging the cleaning liquid.

10 Washing container 10A Lid 10B Container

Claims (9)

In the cleaning container, the object to be cleaned is cleaned by bringing it into contact with a cleaning liquid containing dissolved gas having a saturation solubility or higher at the liquid temperature of the cleaning liquid (hereinafter, this cleaning liquid is referred to as “supersaturated gas solution”). And
The supersaturated gas solution is introduced into the cleaning container, or the cleaning liquid is introduced into the cleaning container and then pressurized gas is introduced to prepare the supersaturated gas solution in the cleaning container. Process,
And a second step of generating bubbles from the supersaturated gas solution by reducing the pressure in the cleaning vessel in a state where an object to be cleaned is in contact with the supersaturated gas solution in the cleaning container. How to wash.   2. The cleaning method according to claim 1, wherein the cleaning step including the first step and the second step is performed a plurality of times.   3. The cleaning method according to claim 2, further comprising a third step of replacing the cleaning liquid in the cleaning container between the cleaning step and the next cleaning step.   4. The dissolved gas according to claim 1, wherein the dissolved gas is one or more selected from the group consisting of nitrogen gas, oxygen gas, carbon dioxide gas, hydrogen gas, ozone gas, clean air, and rare gas. A cleaning method characterized by comprising:   5. The cleaning method according to claim 1, wherein the cleaning liquid is pure water or ultrapure water, or pure water or ultrapure water in which a chemical is dissolved.   6. The cleaning method according to claim 5, wherein the drug is one or more selected from the group consisting of an alkali, an acid, a chelating agent, and a surfactant.   The cleaning method according to claim 6, wherein the alkali is ammonia. An apparatus for cleaning an object to be cleaned by bringing it into contact with a cleaning liquid containing dissolved gas having a solubility equal to or higher than the saturation solubility at the liquid temperature of the cleaning liquid (hereinafter referred to as “supersaturated gas solution”). And
A pressure-resistant cleaning container that can be sealed;
Means for introducing the supersaturated gas solution into the cleaning vessel;
Means for depressurizing the inside of the cleaning container;
Means for discharging the cleaning liquid in the cleaning container,
In a state where the object to be cleaned is in contact with the supersaturated gas solution in the cleaning container, the object to be cleaned is cleaned by reducing the pressure in the cleaning container and generating bubbles from the supersaturated gas solution. Characteristic cleaning device. An apparatus for cleaning an object to be cleaned by bringing it into contact with a cleaning liquid containing dissolved gas having a solubility equal to or higher than the saturation solubility at the liquid temperature of the cleaning liquid (hereinafter referred to as “supersaturated gas solution”). And
A pressure-resistant cleaning container that can be sealed;
Means for introducing the cleaning liquid into the cleaning container;
Means for introducing a pressurized gas into the cleaning container and causing the cleaning liquid in the cleaning container to contain a dissolved gas having a saturation solubility or higher at the liquid temperature of the cleaning liquid;
Means for depressurizing the inside of the cleaning container;
Means for discharging the cleaning liquid in the cleaning container,
In a state where the object to be cleaned is in contact with the supersaturated gas solution in the cleaning container, the object to be cleaned is cleaned by reducing the pressure in the cleaning container and generating bubbles from the supersaturated gas solution. Characteristic cleaning device.

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