JP2007150164A - Substrate washing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate washing method which can be improved in washing capability while suppressing damage to a fine pattern. <P>SOLUTION: A substrate is washed in a processing solution with an ultrasonic wave while the temperature of the processing solution is ≤18°C. One or more kinds of gas selected from a group of N<SB>2</SB>, H<SB>2</SB>, O<SB>2</SB>, CO<SB>2</SB>, and Ar are dissolved in the processing solution. The temperature of the processing solution is ≤18°C during the ultrasonic washing, so particles sticking on the substrate are removed with a physical force resulting from a cavitation phenomenon of the gas dissolved in the processing solution. The physical force resulting from a cavitation phenomenon of vapor in the processing solution is relatively small, so damage is suppressed to the fine pattern. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for cleaning a substrate such as a semiconductor wafer.

  In the manufacturing process of a substrate such as a semiconductor wafer, contaminants such as particles, organic substances, and metals adhering to the surface of the substrate are removed, that is, washed. In the cleaning process of these pollutants, conventionally, chemical cleaning using a chemical reaction between a chemical solution and pure water and the pollutant, a two-fluid jet that jets a mixture of ultrasonic physical force or liquid and gas, etc. Physical cleaning that blows away contaminants by physical force and cleaning that is a combination of chemical cleaning and physical cleaning have been performed.

  Ultrasonic cleaning is effective physical cleaning for removing particles adhering to the surface of the substrate. In this cleaning method, it is considered that particles are removed by a physical force resulting from a cavitation phenomenon (Cavitation) generated in a processing solution by ultrasonic waves. The cavitation phenomenon is a phenomenon in which a part having an extremely low pressure is generated in a liquid, and the liquid in the part is vaporized, thereby generating a vapor cavity for a very short period. More specifically, in ultrasonic cleaning, it is considered that particles on a substrate are removed by an impact force when a vapor cavity disappears.

  In general, a substrate cleaning apparatus for a semiconductor wafer or the like includes a batch type cleaning apparatus (Batch Processing Cleaning Equipment) and a single wafer type cleaning apparatus (Single Wafer Processing Cleaning Equipment). Also in the ultrasonic cleaning equipment (Megasonic Cleaning Equipment), there are a batch type cleaning apparatus and a single wafer type cleaning apparatus.

  In a batch-type ultrasonic cleaning apparatus, one to several tens of wafers are immersed in the processing solution at a time with the ultrasonic wave introduced into the processing solution by the ultrasonic vibrator installed in the processing tank. And the wafer is cleaned.

  There are a number of systems such as a nozzle type (Nozzle Type), a proximity type (Proximity Type), and a bar type (Bar Type) in the system of the single wafer type ultrasonic cleaning apparatus. For example, when a nozzle type cleaning apparatus is used, a processing solution into which ultrasonic waves have been introduced is injected onto the wafer by an ultrasonic transducer attached to the nozzle, and the wafers are cleaned one by one. In the case of using a proximity type or bar type cleaning apparatus, a processing solution is filled between the wafer and the bar, and ultrasonic waves are introduced into the processing solution by an ultrasonic vibrator attached to the bar. The wafers are cleaned one by one.

What is common to these conventional ultrasonic cleaning methods is that either a batch type cleaning apparatus or a single wafer type cleaning apparatus is used at room temperature (about 20 ° C.) or at a high temperature. It means that is used.
Japanese Patent Laid-Open No. 11-154657 JP 2000-164552 A JP 2001-79504 A JP 2001-284306 A JP 2001-35824 A JP-A-9-1093

  In recent years, with the miniaturization of semiconductor devices, the miniaturization of patterns formed on the surface of a substrate has progressed. When ultrasonic cleaning is performed on the surface of a substrate on which a fine pattern is formed, the surface of the substrate is damaged by physical force due to cavitation.

  For example, in the cleaning of a wafer surface on which a fine pattern is formed, conventionally, a batch type cleaning apparatus is used to mix APM (ammonia / hydrogen peroxide solution / pure water) at a temperature of room temperature (20 ° C.) or higher. ) And other chemical cleaning using an alkaline chemical solution (Chemical) and physical cleaning using ultrasonic waves (Ultrasonic cleaning in APM) has been widely used.

  When this combination cleaning is used, as the semiconductor device is miniaturized, the damage of the fine pattern due to the ultrasonic wave becomes remarkable. The damage of a fine pattern becomes a fatal defect for a semiconductor device. On the other hand, in order to suppress the occurrence of damage to the fine pattern, if only the chemical cleaning is performed without performing the ultrasonic cleaning, the cleaning ability becomes extremely low. If the cleaning ability is low, the yield decreases due to contamination of particles and organic substances adhering to the wafer surface.

  In addition, single-wafer ultrasonic cleaning using a nozzle, a bar, and the like has been developed. In these methods, as in batch ultrasonic cleaning, ultrasonic waves damage the surface of the substrate. Therefore, these methods cannot be used as a method for cleaning a substrate having a fine pattern.

  In recent years, methods for suppressing the occurrence of damage on the surface of a substrate by increasing the amount of dissolved gas in a processing solution for ultrasonic cleaning using nitrogen or the like have been studied. However, according to this method, if it is attempted to suppress the occurrence of damage on the surface of the substrate, the cleaning ability becomes insufficient.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a substrate cleaning method capable of improving the cleaning capability while suppressing the occurrence of damage to a fine pattern.

  The substrate cleaning method of the present invention is a substrate cleaning method using ultrasonic cleaning that removes particles adhering to a substrate using physical force resulting from a cavitation phenomenon of dissolved gas in a processing solution. Further, the temperature of the treatment solution when ultrasonically cleaning the substrate is 18 ° C. or lower. The dissolved gas is one of one or more kinds of gases not containing ozone and a plurality of kinds of gases containing ozone. In short, any gas other than ozone alone may be used as the dissolved gas.

  According to the present invention, it is possible to suppress the occurrence of substrate damage while obtaining a high cleaning ability. The cleaning apparatus used in the above-described substrate cleaning method may be either a batch type cleaning apparatus or a single wafer type cleaning apparatus. The single wafer cleaning device may be any of a nozzle type, a bar type, and an approach type.

First, the technical idea of the substrate cleaning method according to the embodiment of the present invention will be described.
It is considered that the physical force acting on the particles when the particles on the surface of the substrate are removed by ultrasonic waves is the physical force acting due to cavitation generated in the treatment solution. On the other hand, when the fine pattern formed on the surface of the substrate is damaged by the ultrasonic wave, the physical force acting on the fine pattern is also considered to be the physical force acting due to cavitation.

  However, the physical force that damages the fine pattern is considered to be greater than the physical force that removes the particles. Therefore, the physical force that damages the fine pattern is mainly due to the cavitation of water vapor with a large energy, while the physical force for removing particles is mainly due to the cavitation of a dissolved gas with low energy. It is thought that it is a physical force acting as a.

  Therefore, in the substrate cleaning method of the present invention, the temperature of the processing solution used for ultrasonic cleaning is set lower than the temperature of the conventional processing solution. Specifically, the temperature of the treatment solution used for ultrasonic cleaning is lowered to 18 ° C. or lower. Thereby, the generation of water vapor in the treatment solution is suppressed. As a result, the occurrence of cavitation of water vapor that generates physical energy with large energy is suppressed. On the other hand, cavitation of dissolved gas with low energy is promoted. Therefore, the occurrence of damage to the fine pattern is suppressed, and the ability to remove particles from the substrate is improved.

  In order to confirm whether the above technical idea is appropriate or not, the relationship between the temperature of the processing solution used for ultrasonic cleaning and the number of damages of the fine pattern on the substrate cleaned by ultrasonic is examined. It was. The result is shown in FIG.

  As can be seen from FIG. 1, when the temperature of the treatment solution used for ultrasonic cleaning is 18 ° C. or lower, the number of damages of the fine pattern is reduced regardless of whether low-power or high-power ultrasonic waves are used. . Further, by lowering the temperature of the ultrasonic treatment solution, it is possible to dissolve a larger amount of gas in the treatment solution than the amount of gas conventionally dissolved in the treatment solution. That is, when the temperature of the treatment solution is 18 ° C. or lower, the occurrence of cavitation of water vapor is suppressed and the generation of cavitation of dissolved gas is promoted. As a result, the cleaning ability can be improved while suppressing the occurrence of damage to the fine pattern.

Hereinafter, the substrate cleaning method implemented based on the above technical idea will be described in detail.
The substrate cleaning method of this embodiment is used for cleaning the surface of a substrate such as a semiconductor wafer. It is particularly effective that the substrate cleaning method of the present embodiment is used in the step of cleaning a substrate on which a fine pattern having an aspect ratio of 1.5 or more is formed. For example, the substrate cleaning method of the embodiment is desirably used for substrate cleaning after gate pattern formation in a semiconductor wafer manufacturing process and substrate cleaning after trench pattern formation in a Cu wiring formation process.

  Hereinafter, a substrate cleaning method according to an embodiment of the present invention will be described with reference to the drawings. In addition, in each figure, since it has the same structure and function regarding the site | part to which the same referential mark is attached | subjected, the description is not repeated if it is not necessary.

Embodiment 1 FIG.
FIG. 2 is a schematic diagram for explaining a substrate cleaning method using the batch type cleaning apparatus of the first embodiment. The batch type cleaning apparatus includes at least one processing tank 2, a processing tank 3, and a water cleaning tank (not shown) for cleaning the substrate 1. In the treatment tank 2, a chemical treatment is performed at a temperature of room temperature (20 ° C.) or higher. In the treatment tank 3, ultrasonic cleaning is performed in a treatment solution at a low temperature (18 ° C. or less). In the washing tank, cleaning using pure water is performed.

The processing tank 2 includes a temperature sensor 5 a and a heater 6, and is connected to the chemical mixing unit 8. The heater 6 can raise the temperature of the processing solution in the processing tank 2 to 100 ° C. The temperature of the processing solution in the processing tank 2 is detected by the temperature sensor 5a, and a signal indicating the temperature is transmitted from the temperature sensor 5a to the temperature monitor / control unit 7. The temperature monitor / control unit 7 controls the heater 6 based on the above-described signal to adjust the temperature of the processing solution in the processing tank 2. The chemical mixing unit 8 is supplied with chemical liquid and pure water from the factory, and supplies pure water and chemical liquid into the treatment tank 2. Note that at least one of H ₂ O ₂ , NH ₄ OH, HF, NH ₄ F, HCl, and H ₂ SO ₄ is used as the chemical solution.

  The treatment tank 3 includes an ultrasonic transducer 4 and a temperature sensor 5b, and is connected to a pure water cooling unit 9, a dissolved gas control unit 10, and an ultrasonic control unit 11. The ultrasonic transducer 4 introduces ultrasonic waves into the treatment tank 3. The ultrasonic frequency and output are controlled by the ultrasonic control unit 11. The pure water cooling unit 9 can cool the pure water supplied from the factory to a temperature of 18 ° C. or less, and sends the cooled pure water to the treatment tank 3. The temperature of the processing solution in the processing tank 3 is detected by the temperature sensor 5b, and a signal indicating the temperature is transmitted from the temperature sensor 5b to the temperature monitor / control unit 7. Based on the signal, the temperature monitor / control unit 7 controls the pure water cooling unit 9 to adjust the temperature of the processing solution in the processing tank 3. The dissolved gas control unit 10 dissolves the gas supplied from the factory at a desired concentration in the cooled pure water in the treatment tank 3.

Thereby, the pure water which is cooled and in which the gas is dissolved is supplied into the treatment tank 3. As the gas dissolved in pure water, one or more kinds of gases selected from the group consisting of N ₂ , H ₂ , O ₂ , CO ₂ , and Ar are used. Further, a plurality of types of gases such as the above-described mixed gas composed of dissolved gas and ozone (O ₃ ) may be dissolved in pure water. In the present embodiment, contaminants adhering to the substrate 1 are removed by physical force resulting from cavitation of these dissolved gases. Moreover, the processing tank 3 has a function to cope with overflow of pure water. In the treatment tank 3, the ultrasonic treatment and the water washing treatment are continuously performed. The chemical mixing unit 8 can also supply the chemical into the treatment tank 3 via the pure water cooling unit 9.

Hereinafter, the substrate cleaning method of the present embodiment will be specifically described.
First, the substrate 1 is immersed in the processing tank 2. Next, the substrate is cleaned using a chemical solution having a temperature equal to or higher than room temperature (20 ° C.). Thereby, the contaminants such as resist, organic matter, metal, and particles attached to the surface of the substrate 1 and the natural oxide film on the surface of the substrate 1 are removed.

The following are usually used as chemicals. SPM (H ₂ SO ₄ / H ₂ O ₂ / pure water mixture) is used to remove the resist and organic matter. Further, HPM (a mixed solution of HCl / H ₂ O ₂ / pure water) is used for removing the metal. Further, APM (mixture of NH ₄ OH / H ₂ O ₂ / pure water) is used for removing particles. Further, HF or BHF (HF / NH ₄ F mixed solution) is used for removing the natural oxide film.

  Next, the substrate 1 is transferred from the processing tank 2 to the processing tank 3 or the water washing tank, and the water washing process is performed using pure water in the processing tank 3 or the water washing tank (not shown). As a result, the resist, organic matter, metal, particles, and other contaminants removed from the surface of the substrate 1 by the chemical treatment and the natural oxide film dissolved and ionized are washed away together with the residual chemical solution on the surface of the substrate 1. It is.

  Next, ultrasonic cleaning is performed in the treatment tank 3. Thereby, residual particles on the surface of the substrate 1 are removed. At this time, the treatment solution (mainly pure water) is cooled by the pure water cooling unit 9 to a temperature lower than 18 ° C., preferably 10 ° C. or lower. According to this, since ultrasonic cleaning is performed in a processing solution at a low temperature, particles on the surface of the substrate 1 can be removed while suppressing the occurrence of damage to the fine pattern formed on the surface of the substrate 1. Can do.

  As described above, the combination of the chemical treatment using a chemical solution at room temperature or higher and the ultrasonic treatment in a low temperature treatment solution can improve the particle removal ability as compared with cleaning in which only ultrasonic treatment is performed. It becomes possible. In particular, when APM (a mixed solution of ammonia / hydrogen peroxide solution / pure water) is used as a chemical solution, a state where particles are lifted off by etching the surface of the substrate 1 with a small amount in advance using APM. Thus, since the physical force resulting from the ultrasonic waves acts on the particles, the particle removal capability is dramatically improved.

  Further, the dissolved gas control unit 10 dissolves the gas in the treatment tank 3. This further improves the particle removal capability and further reduces the number of occurrences of fine pattern damage. In the step of dissolving the gas in the treatment tank 3, a single gas may be used or a mixed gas composed of a plurality of types of gases may be used. When the dissolved gas concentration in the treatment tank 3 is in a saturated state, it is difficult to transmit ultrasonic waves in the treatment solution, so that the cleaning performance is deteriorated. On the other hand, when the amount of dissolved gas in the treatment tank 3 is too small, cavitation caused by water vapor is generated more than cavitation caused by dissolved gas, so that the fine pattern is damaged. Therefore, the range of the dissolved gas concentration is preferably 95% or less of the saturated state, and more preferably 50% to 90%.

Further, the higher the frequency of the ultrasonic wave, the smaller the number of damages of the fine pattern. However, the particle removal capability does not change even if the ultrasonic frequency is increased. Further, the lower the output of the ultrasonic wave, the smaller the number of damages of the fine pattern and the lower the particle removal ability. Therefore, in the substrate cleaning method of the present embodiment, the frequency of the ultrasonic wave is preferably 100 kHz or higher, and more preferably 800 kHz or higher. The output of the ultrasound is preferably ^{0.01W / cm 2 ~20W / cm 2} , more preferably if ^{0.1W / cm 2 ~10W / cm 2} .

  Furthermore, an additive may be added to the treatment solution for ultrasonic cleaning. Thereby, the freezing point of the treatment solution is lowered. For example, when the processing solution is pure water, the freezing point of the processing solution becomes lower than 0 ° C. when an additive such as ethylene glycol is added to the processing solution. According to this, the particle removal capability can be further improved, and the occurrence of damage to the fine pattern is suppressed. In addition, when the additive is added to the processing solution, the boiling point of the processing solution increases and the vapor pressure decreases. Thereby, the frequency of occurrence of water vapor cavitation is reduced. Therefore, occurrence of damage to the fine pattern on the surface of the substrate 1 is suppressed.

  Further, as a treatment solution used for ultrasonic cleaning, a liquid having a surface tension smaller than that of pure water, for example, acetic acid, aqueous acetic acid solution, aqueous ammonia, or aqueous alcohol solution may be used in addition to pure water that is usually used. If a liquid having a surface tension smaller than that of pure water is used, the occurrence of damage to the fine pattern on the surface of the substrate 1 is suppressed.

  Further, it is desirable to use a liquid having a melting point higher than the melting point of water (0 ° C.) and lower than the temperature of the processing solution at the time of ultrasonic cleaning as the processing solution used for ultrasonic cleaning. For example, acetic acid (16.6 ° C.) or formic acid (8.4 ° C.) may be used. The numbers in parentheses are melting points.

  However, when acetic acid is used as the treatment solution, the temperature of the treatment solution is adjusted to a temperature higher than 16.6 ° C and lower than 18 ° C. When formic acid is used as the treatment solution, the temperature of the treatment solution is adjusted to a temperature higher than 8.4 ° C. and 18 ° C. or lower. The reason is that if the temperature of the processing solution is lower than the melting point of the processing solution, the processing solution changes from liquid to solid. Further, as described above, when the melting point of the treatment solution is higher than the melting point (0 ° C.) of pure water, the vapor pressure of the treatment solution is lowered. As a result, the generation of bubbles in the treatment solution is suppressed, so that the occurrence of cavitation is suppressed. That is, the same effect as that obtained by lowering the temperature of the treatment solution can be obtained.

Further, as a treatment solution used for ultrasonic cleaning, in addition to the pure water usually used, a chemical solution such as H ₂ O ₂ , NH ₄ OH, HF, NH ₄ F, HCl, H ₂ SO ₄ , or the like, or these May be used. For example, it is known that the aforementioned chemical solution such as APM suppresses the occurrence of fine pattern damage due to ultrasonic cleaning, as compared with pure water. Therefore, the ultrasonic cleaning using the cooled chemical solution further suppresses the occurrence of damage to the fine pattern.

  Next, in the treatment tank 3 or a water washing tank (not shown), a water washing process is performed again using pure water. As a result, the particles removed by the ultrasonic cleaning are washed away and are prevented from adhering again to the surface of the substrate 1. Finally, the substrate 1 is dried in a drying tank (not shown).

Next, a substrate cleaning method according to a modification of the present embodiment will be described.
FIG. 3 is a schematic diagram showing a first modification of the cleaning apparatus of the present embodiment. The cleaning device of the first modification is the same as the cleaning device of the present embodiment described above, except that the treatment tank 3 exists in the sealed chamber 12. Gas is supplied from the factory into the sealed chamber 12. In the ultrasonic cleaning in the processing tank 3, the gas in the sealed chamber 12 is supplied, so that the space in the sealed chamber 12 is in a high pressure state, so that the processing solution is in a pressurized state. Thereby, since generation | occurrence | production of the cavitation of the water vapor | steam in a process solution is suppressed, generation | occurrence | production of the damage of the fine pattern resulting from an ultrasonic wave is suppressed.

  FIG. 4 is a schematic diagram showing a second modification of the cleaning apparatus of the present embodiment. In the cleaning device of the second modified example, both the ultrasonic transducer 4 and the heater 6 are provided in at least one treatment tank 2. The ultrasonic transducer 4 is controlled by the ultrasonic control unit 11. In addition, a temperature sensor 5 for measuring the temperature of the processing solution in the processing tank 2 is provided, and temperature information acquired by the temperature sensor 5 is transmitted to the temperature monitor / control unit 7. Thereby, the temperature monitor / control unit 7 controls the heater 6 based on the temperature information and adjusts the temperature of the processing solution. Further, the temperature monitor / control unit 7 controls the pure water cooling unit 9 based on the temperature information to adjust the temperature of the pure water. The pure water whose temperature is adjusted in the pure water cooling unit 9 is sent to the dissolved gas control unit 10. In the dissolved gas control unit 10, the aforementioned gas and pure water are mixed. Thereafter, mixed water in which gas and pure water are mixed is fed into the treatment tank 2. In the chemical mixing unit 8, the chemical and pure water are mixed. A mixed liquid of the chemical liquid and pure water is fed into the treatment tank 2. Moreover, the processing tank 2 has a function of processing overflow of pure water.

  According to the second modification of the cleaning device of the present embodiment, chemical processing, ultrasonic cleaning at low temperature, and water cleaning processing using a chemical at a temperature of room temperature (20 ° C.) or higher in one processing tank 2 are performed. It is done continuously.

Next, a substrate cleaning method according to a second modification using the cleaning apparatus shown in FIG. 4 will be described.
First, the substrate 1 is immersed in the processing tank 2. Thereafter, chemical cleaning is performed using a chemical at a temperature equal to or higher than room temperature (20 ° C.). As a result, the resist, organic substances, contaminants such as metal particles attached to the surface of the substrate 1 and the natural oxide film on the surface of the substrate 1 are removed in advance.

  Next, the pure water in the processing tank 2 is continuously overflowed to the outside, and the substrate 1 is washed with water. Next, the treatment tank 2 is filled with pure water having a dissolved gas having a temperature of 18 ° C. or less, preferably 10 ° C. or less, and ultrasonic treatment is continuously performed. Thereby, particles on the surface of the substrate 1 are removed. Next, the pure water in the treatment tank 2 overflows to the outside again, and the substrate 1 is washed with water. Finally, the substrate 1 is dried in a drying tank (not shown).

  According to the substrate cleaning method of the second modification as described above, the chemical cleaning and the ultrasonic cleaning using the low temperature processing solution are performed in one processing tank 2 without exposing the substrate 1 to the atmosphere. Is performed continuously. For this reason, the particles are prevented from adhering to the substrate 1 again. In addition, it is possible to reduce the size of the cleaning device.

  According to each of the above-described cleaning methods, it is possible to perform ultrasonic cleaning that provides high particle removal capability while suppressing the occurrence of damage to the fine pattern. Thereby, the yield of products such as semiconductor devices is improved.

Embodiment 2. FIG.
Next, the substrate cleaning method according to the second embodiment of the present invention will be described with reference to FIG. FIG. 5 is a schematic diagram illustrating a single wafer cleaning apparatus according to the second embodiment.

  The cleaning apparatus according to the present embodiment is a nozzle type, and one or a plurality of chemical liquid nozzles 108 capable of performing chemical liquid cleaning using a chemical liquid having a temperature equal to or higher than room temperature (20 ° C.) and ultrasonic waves are introduced. One or a plurality of ultrasonic nozzles 105 capable of discharging a low-temperature treatment solution, and one or a plurality of nozzles (not shown) capable of discharging pure water and washing with water are provided. Yes.

  In the cleaning apparatus shown in FIG. 5, the substrate 101 is held by chuck pins 102, and the chuck pins 102 are fixed on the plate 103. The plate 103 is rotated at a desired number of rotations by the motor 104. As a result, the plate 103 and the chuck pin 102 rotate. Therefore, the substrate 101 rotates.

  The chemical nozzle 108 is supplied with pure water and chemical from the factory. The pure water is heated by the heater 112, and the temperature rises to 100 ° C. The pure water heated in the chemical liquid mixing unit 111 and the chemical liquid are mixed, and the mixed chemical liquid is discharged onto the surface of the substrate 101 from the chemical liquid nozzle 108.

  The ultrasonic nozzle 105 is supplied with pure water and gas from the factory. Pure water is cooled to a temperature of 18 ° C. or less by the pure water cooling unit 109. In addition, gas is mixed in the dissolved pure water in the dissolved gas control unit 110. The cooling water mixed with gas is supplied to the ultrasonic nozzle 105. The ultrasonic nozzle 105 includes an ultrasonic transducer 106, and the ultrasonic transducer 106 is controlled by the ultrasonic control unit 107. Therefore, pure water in which ultrasonic waves are introduced, cooled, and dissolved in gas is discharged from the ultrasonic nozzle 105 onto the surface of the substrate 101.

Next, a substrate cleaning method using the cleaning apparatus shown in FIG. 5 will be specifically described.
First, the substrate 1 is placed on the plate 103 and held by the chuck pins 102. Next, the motor 104 rotates, and the substrate 1 rotates at a desired number of rotations together with the plate 103 and the chuck pins 102.

Next, a chemical solution having a temperature of room temperature (20 ° C.) or more is discharged from the chemical solution nozzle 108 toward the substrate 1. As a result, the resist, organic matter, metal, contaminants such as particles adhering to the surface of the substrate 101, and the natural oxide film on the surface of the substrate 101 are removed in advance. As the chemical solution, H ₂ O ₂ , NH ₄ OH, HF, NH ₄ F, HCl, H ₂ SO ₄ , or a mixture thereof can be used, and in particular, the chemical solution such as the aforementioned APM is used. Is desirable. That is, the type and use of the chemical solution are the same as the type and use of the chemical solution used in the substrate cleaning method in the first embodiment.

  Next, while the substrate 1 is rotating, pure water is discharged from a water washing nozzle (not shown), and the substrate 1 is washed with water. Thereby, the contaminants removed from the surface of the substrate 1 by the chemical treatment and the natural oxide film dissolved into ions are washed away together with the residual chemical solution on the surface of the substrate 1.

  Next, while the substrate 101 is rotating, a processing solution, that is, an ultrasonic wave is introduced from the ultrasonic nozzle 105, cooled, and pure water dissolved in gas is discharged. Thereby, residual particles on the surface of the substrate 1 are removed. At this time, pure water into which ultrasonic waves are introduced and gas is dissolved is cooled to a temperature of 18 ° C. or less, preferably 10 ° C. or less by the pure water cooling unit 109.

  As described above, since ultrasonic cleaning is performed using a low-temperature treatment solution, it is possible to suppress damage to a fine pattern formed on the surface of the substrate 1 and to remove particles on the surface of the substrate 1. Will improve. As in the first embodiment, acetic acid, an acetic acid aqueous solution, ammonia water, or alcohol water whose surface tension is smaller than that of pure water can be used as the treatment solution. Similarly to Embodiment 1, ethylene glycol may be mixed into the treatment solution as an additive for lowering the freezing point of pure water below 0 ° C. As in the first embodiment, acetic acid or formic acid having a melting point higher than that of water and a melting point lower than that of the processing solution when ultrasonic cleaning is performed may be used as the processing solution.

  At this time, pure water cooled to 18 ° C. or less may be discharged from a nozzle (not shown) toward the back surface of the substrate 1. Thereby, since the back surface of the substrate 1 is cooled, the same effect as that obtained by lowering the ultrasonic treatment solution can be obtained.

  Further, the back surface of the substrate 1 may be heated by means (not shown) for heating the substrate 1 such as a heater or an infrared lamp. By heating the back surface of the substrate 1, the chemical reaction in the processing solution near the surface of the substrate 1 is promoted, so that the particle removal capability is improved.

The dissolved gas control unit 110 dissolves gas in pure water. Thereby, the further particle removal capability is improved and the occurrence of damage to the fine pattern is suppressed. As the gas dissolved in the pure water, one or more kinds of gases selected from the group consisting of N ₂ , H ₂ , O ₂ , CO ₂ , and Ar are used. Further, a plurality of types of gases such as the above-described mixed gas composed of dissolved gas and O ₃ may be dissolved in pure water. The range of the dissolved gas concentration is preferably 95% or less of the saturated state, more preferably 50% to 90%. That is, the kind of dissolved gas and the amount of dissolved gas are the same as the kind of dissolved gas and the amount of dissolved gas in the substrate cleaning method of the first embodiment.

Moreover, the frequency of an ultrasonic wave is 1 MHz or more, Preferably, it is 1.5 MHz or more. Further, the output of the ultrasonic ^{wave, 0.01W / cm 2 ~20W / cm} 2, ^{preferably, 0.1W / cm 2 ~10W / cm} 2.

  Next, in a state where the substrate 1 is rotating, pure water is again discharged from the water washing nozzle, and the substrate 101 is washed with water. Thereby, the particles removed by the ultrasonic cleaning are washed away. As a result, it is possible to prevent particles from adhering to the surface of the substrate 1 again. Finally, the substrate 101 is dried by rotating the substrate 101 at a high speed.

  FIG. 6 is a schematic diagram showing a modification of the cleaning apparatus used in the substrate cleaning method of the present embodiment. The cleaning apparatus shown in FIG. 6 is a proximity type or bar type cleaning apparatus, except that an ultrasonic transducer 150 is provided in place of the ultrasonic nozzle 105 shown in FIG. It is the same as the cleaning apparatus shown in FIG. Further, the cleaning method using the cleaning apparatus shown in FIG. 6 is the same as the cleaning method using the cleaning apparatus shown in FIG. In the cleaning apparatus shown in FIG. 6, the processing solution is filled between the substrate 101 and the ultrasonic transducer 150, and ultrasonic waves are introduced into the processing solution by the ultrasonic transducer 150 to ultrasonically clean the surface of the substrate 101. Is done. At this time, as in the ultrasonic cleaning method described above, pure water having a low temperature of 18 ° C. or lower is used as the treatment solution, so that the fine pattern formed on the surface of the substrate 1 is not damaged and the substrate 1 Particles on the surface can be removed.

Moreover, the frequency of the ultrasonic wave is 500 kHz or more, preferably 1 MHz or more. Further, the output of the ultrasonic ^{wave, 0.01W / cm 2 ~20W / cm} 2, ^{preferably, 0.1W / cm 2 ~10W / cm} 2.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a graph which shows the relationship between the temperature of the process solution used for ultrasonic cleaning, and the number of pattern damages. 2 is a schematic view of a cleaning apparatus used in the substrate cleaning method of Embodiment 1. FIG. 6 is a schematic diagram of a first modification of the cleaning apparatus used in the substrate cleaning method of Embodiment 1. FIG. It is the schematic of the 2nd modification of the washing | cleaning apparatus used for the board | substrate washing | cleaning method of Embodiment 1. FIG. 6 is a schematic diagram of a cleaning apparatus used in the substrate cleaning method of Embodiment 2. FIG. 10 is a schematic diagram of a modification of the cleaning apparatus used in the substrate cleaning method of Embodiment 2. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Substrate, 2, 3 Processing tank, 4 Ultrasonic vibrator, 5, 5a, 5b Temperature sensor, 6 Heater, 7 Temperature monitor / control part, 8 Chemical liquid mixing part, 9 Pure water cooling part, 10 Dissolved gas control part, 11 Ultrasonic Control Unit, 12 Sealed Chamber, 101 Substrate, 102 Chuck Pin, 103 Plate, 104 Motor, 105 Ultrasonic Nozzle, 106 Ultrasonic Vibrator, 107 Ultrasonic Control Unit, 108 Chemical Liquid Nozzle, 110 Dissolved Gas Control Unit, 111 Chemical liquid mixing unit, 112 heater, 150 ultrasonic vibrator.

Claims (20)

A substrate cleaning method using ultrasonic cleaning that removes particles adhering to a substrate using physical force resulting from cavitation of dissolved gas in a processing solution,
The temperature of the treatment solution when performing ultrasonic cleaning of the substrate is 18 ° C. or less,
The substrate cleaning method, wherein the dissolved gas is one or more kinds of gases not containing ozone and a plurality of kinds of gases containing ozone. The substrate cleaning method according to claim 1, wherein the dissolved gas contains one or more kinds of gases selected from the group consisting of N ₂ , H ₂ , O ₂ , CO ₂ , and Ar.   The substrate cleaning method according to claim 1, wherein the temperature of the treatment solution is 10 ° C. or less.   The substrate cleaning method according to claim 1, wherein a chemical solution treatment for cleaning the substrate with a chemical solution is further performed. The substrate cleaning according to claim 4, wherein the chemical solution includes one or more substances selected from the group consisting of H ₂ O ₂ , NH ₄ OH, HF, NH ₄ F, HCl, and H ₂ SO _4. Method.   The substrate cleaning method according to claim 4, wherein the chemical solution treatment and the ultrasonic cleaning are continuously performed in the processing solution without exposing the substrate to the atmosphere.   The substrate cleaning method according to claim 1, wherein a ratio of the dissolved gas in the processing solution is 95% or less of a saturated state.   The substrate cleaning method according to claim 7, wherein a ratio of the dissolved gas in the processing solution is 50% to 90% of a saturated state.   The substrate cleaning method according to claim 1, wherein a liquid having a surface tension smaller than pure water is used as the treatment solution.   The substrate cleaning method according to claim 9, wherein acetic acid, an acetic acid aqueous solution, ammonia water, or alcohol water is used as the liquid having a surface tension smaller than that of pure water.   The substrate cleaning method according to claim 1, wherein a liquid having a melting point higher than the melting point of water and lower than the temperature of the processing solution when the ultrasonic cleaning is performed is used as the processing solution.   The substrate cleaning method according to claim 11, wherein acetic acid or formic acid is used as the liquid.   When a batch type cleaning device is used, the ultrasonic frequency is 100 kHz or more, and when a nozzle type single-type cleaning device is used, the ultrasonic frequency is 1 MHz or more, 2. The substrate cleaning method according to claim 1, wherein, when a single-type or bar-type cleaning apparatus is used, the frequency of the ultrasonic wave is 500 kHz or more.   When a batch type cleaning device is used, the ultrasonic frequency is 800 kHz or more, and when a nozzle-type single-type cleaning device is used, the ultrasonic frequency is 1.5 MHz or more. The substrate cleaning method according to claim 13, wherein when a proximity type or bar type single-mode cleaning apparatus is used, the frequency of the ultrasonic wave is 1 MHz or more. The output of the ultrasonic wave is ^{0.01W / cm 2 ~20W / cm 2} , a substrate cleaning method according to claim 1. The output of the ultrasonic wave is ^{0.1W / cm 2 ~10W / cm 2} , a substrate cleaning method according to claim 15.   2. The ultrasonic cleaning according to claim 1, wherein a treatment tank containing the substrate and the treatment solution is installed in a chamber, and the ultrasonic cleaning is performed in a state where the treatment solution is pressurized by a gas in the chamber. Substrate cleaning method.   The substrate cleaning method according to claim 1, wherein the substrate is cooled when a sheet-type cleaning apparatus is used.   The substrate cleaning method according to claim 1, wherein the substrate is heated when a sheet-type cleaning apparatus is used. An additive is included in the treatment solution;
The substrate cleaning method according to claim 1, wherein a freezing point of the processing solution is lowered by the additive.

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