JP4481811B2 - Cleaning device and cleaning method - Google Patents

Description

The present invention relates to a cleaning apparatus and a cleaning method suitable for cleaning a member such as a silicon substrate or a glass substrate in a process of manufacturing an ultraprecision electronic component such as a semiconductor element or a liquid crystal panel.

  In the manufacturing process of semiconductor elements and liquid crystal panels, the management of cleanliness is an important issue that affects the manufacturing yield. In particular, particle contamination on the surface of the member causes a short circuit between wirings, a pattern defect, an insulation failure of an interlayer insulating film, and the like, so that strict cleanliness management is required.

  In order to avoid deterioration of device characteristics and manufacturing yield due to particle contamination, a cleaning process is introduced between the processes, and the manufacturing process is advanced while keeping the surface of the member extremely clean.

  Taking the manufacturing process of a semiconductor element as an example, conventionally, the cleaning of the surface of a silicon substrate has been mainly performed by mixing a solution prepared by mixing concentrated ammonia water or concentrated hydrochloric acid, hydrogen peroxide water, and ultrapure water. A method based on the so-called RCA cleaning method (published by Radio Corporation of America, 1970), in which a silicon substrate is immersed in this solution for a certain period of time after being heated to a certain temperature and then rinsed with ultrapure water. Has been done.

  The RCA cleaning method is a cleaning method that exhibits an extremely excellent effect in removing organic substances, metals, and particles adhering to the surface of a silicon substrate, and has been widely used up to now with various improvements. In particular, an alkaline solution called SC1 (Standard Clean 1), which is a mixture of concentrated aqueous ammonia and hydrogen peroxide, dissolves the vicinity of the silicon substrate while oxidizing the surface of the silicon substrate, and desorbs adhering particles from the surface (lift-off). ) In addition, since the liquid is alkaline, it has a function to suppress re-adhesion due to electrostatic repulsion between the substrate surface and particles, effectively removing particle contamination on the silicon substrate surface. can do.

  As described above, the RCA cleaning method is an effective cleaning method. However, the RCA cleaning method requires a large amount of a chemical solution such as an acid, an alkali, or hydrogen peroxide having a high concentration and high purity (high quality), and a chemical treatment. A large amount of ultrapure water for rinsing the substrate later is also used. Moreover, since each said chemical | medical solution is discharged | emitted in the waste liquid after washing | cleaning, a big burden is imposed on neutralization, a precipitation process, etc. in waste water treatment, and a lot of sludge is also derived.

  Therefore, in order to carry out the RCA cleaning method, in order to ensure the cleanliness of the silicon substrate surface, a large amount of cost is required for chemicals, ultrapure water, and waste liquid treatment.

  In addition, not only the cleaning process in the manufacturing process of semiconductor elements, but as a general problem for the entire manufacturing industry, from the viewpoint of protecting the natural environment, from the manufacturing method using a large amount of chemical substances and energy, more environmental impact. The awareness of the issue that the switch to smaller alternatives should be promoted is rapidly increasing in industry.

  For this reason, compared with the RCA cleaning method, a new cleaning method that can reduce the amount of chemical solution used without reducing the cleaning power is being sought.

  Under such circumstances, as a cleaning method attracting attention in recent years, cleaning using water in which a specific gas is dissolved in ultrapure water (hereinafter referred to as “gas-dissolved water”) is used. The method is known. Since the gas-dissolved water exhibits a specific “function” depending on the type of dissolved gas, it is also called “gas-dissolved functional water” or simply “functional water”.

  The fact that some gas-dissolved water has an effect of cleaning the surface of an object, that is, a cleaning effect, has begun to attract attention from around 1990. Various studies have also been made on cleaning devices using dissolved water.

  For example, an ultrasonic cleaning apparatus is known that supplies gas-dissolved water to a cleaning tank containing an object to be cleaned, and applies ultrasonic waves to the cleaning tank to clean the object to be cleaned (see, for example, Patent Document 1). ).

  In addition, paying attention to hydrogen gas as a gas species with high particle removal effect, ultrapure water is vacuum degassed beforehand through a gas permeable membrane, and hydrogen gas is dissolved in this degassed water through the gas permeable membrane In addition, a method and an apparatus for cleaning an object to be cleaned by irradiating ultrasonic waves in the hydrogen-dissolved water are known (for example, see Patent Document 2).

  Furthermore, there is provided a method and apparatus for cleaning an object to be cleaned by irradiating ultrasonic waves in hydrogen-dissolved water in which alkali is dissolved in hydrogen-dissolved water generated by dissolving hydrogen gas in degassed water and pH is adjusted. It is known (for example, refer to Patent Document 3).

  These publicly known documents disclose the most basic technical elements for cleaning using gas-dissolved water, but various cleaning apparatuses or cleaning methods that have been developed by applying these techniques have been invented. Yes.

  Hydrogen-dissolved water obtained by dissolving hydrogen gas in ultrapure water is used as gas-dissolved water having the effect of removing particles from the surface of the object to be cleaned. Hereinafter, the hydrogen-dissolved water is referred to as “hydrogen water”.

  FIG. 7 is a principal block diagram showing an example of an ultrasonic cleaning apparatus using hydrogen water, and the mechanism of cleaning using hydrogen water will be described with reference to this figure.

  The ultrapure water with very few impurities produced by the ultrapure water production apparatus 101 is sent to the deaeration apparatus 102. In the deaeration device 102, the gas dissolved in the ultrapure water is removed by depressurizing the atmosphere in contact with the ultrapure water through the gas permeable membrane 103 using the vacuum pump 104. The deaerated ultrapure water is sent to the gas dissolving device 105.

  In the hydrogen gas generator 106, hydrogen gas is generated by electrolysis of pure water and supplied to the gas dissolving device 105. In the gas dissolution apparatus 105, the ultrapure water deaerated through the gas permeable membrane 107 is in contact with hydrogen gas, and the hydrogen gas is dissolved in the deaerated ultrapure water. By degassing ultrapure water in advance with the degassing device 102, hydrogen gas can be easily dissolved in the gas dissolving device 105. By adjusting the flow rate of ultra pure water and the supply amount of hydrogen gas, the concentration of dissolved hydrogen in the generated hydrogen water can be controlled. In the cleaning for the purpose of removing particles, the dissolved hydrogen concentration in the ultrapure water has a sufficient effect at around 1 ppm.

  Ammonia in the chemical tank 108 is sent to and mixed with the hydrogen water generated in this manner by the function of the pump 109. As will be described later, ammonia is added to adjust the pH of the hydrogen water to the alkali side in order to prevent particles from reattaching to the surface of the object to be cleaned 113. The alkali added to the hydrogen water is not necessarily ammonia, and other alkalis may be added in consideration of the influence on the object to be cleaned.

  The ammonia concentration in the hydrogen water can be grasped and controlled, for example, by measuring the electrical conductivity of the hydrogen water. The hydrogen water is fed into the cleaning tank 110 from the lower part of the cleaning tank 110 and overflows from the upper opening of the cleaning tank 110 to the outside of the cleaning tank 110 (overflow). Therefore, in the cleaning tank 110, the hydrogen water supplied one after another flows continuously from the bottom to the top and does not stay.

  An ultrasonic vibrator 111 is installed on the bottom surface of the cleaning tank 110. When the signal generated by the oscillator 112 is applied to the ultrasonic vibrator 111, the ultrasonic vibrator 111 vibrates and the ultrasonic wave propagates through the hydrogen water filled in the cleaning tank 110. The ultrapure water degassing method in the degassing device 102, the hydrogen gas dissolving method in the gas dissolving device 105, and the hydrogen gas generating method in the hydrogen gas generating device 106 are the methods described here. And may be different.

  When ultrasonic waves are applied to the hydrogen water filled in the cleaning tank 110, some water molecules are decomposed and split into H radicals and OH radicals. These radicals are very reactive, and it is considered that the reaction is most prevalent after they are generated and they are quickly combined to return to a stable water molecule.

  However, some OH radicals react with dissolved hydrogen in hydrogen water to form water molecules, so that H radicals remain relatively in hydrogen water. The excessively high H radicals generated in this way react with the object to be cleaned 113 soaked in hydrogen water or the most terminal portion of the surface of the particles adhering to the surface of the object to be cleaned 113. Arise. For example, it binds to an active outermost surface dangling bond to inactivate it, or causes substitution with a terminal atom. As a result, particle detachment from the surface of the object to be cleaned 113 is promoted.

  In addition to the effect of such excess H radicals, the physical peeling effect due to the generation of microbubbles at the interface between the object to be cleaned 113 and the particles, and the vibration acceleration effect inherent in ultrasonic cleaning are added. In hydrogen water, particles are removed from the surface of the object 113 to be cleaned very effectively. A detailed report has already been made about the mechanism of hydrogen water cleaning (see, for example, Non-Patent Document 1).

  By the way, the value of the zeta potential on the surface of various materials depends on the pH of the solution in contact with the surface. By adding a small amount of ammonia to the hydrogen water to change the pH of the hydrogen water to the alkali side, the zeta potentials of the surfaces of both materials 113 and particles have the same polarity in many combinations of materials to be cleaned 113 and particles. can do.

  As a result, an electrostatic repulsive force is generated between the two, and an effect of preventing reattachment of particles to the object to be cleaned 113 is obtained. Although the pH of hydrogen water changes to 9.4 by adding only 1 ppm of ammonia, this liquid property has the effect of preventing redeposition for many combinations of materials. Further, depending on the combination of materials, a sufficient cleaning effect may be obtained with only hydrogen water without adding ammonia.

  As described above, the hydrogen water cleaning exhibits an excellent particle removal effect by dissolving hydrogen gas having a concentration of about 1 ppm in ultrapure water and adding only about 1 ppm of ammonia if necessary. .

  When comparing the hydrogen water cleaning with the SC1 cleaning mixed with concentrated ammonia water and hydrogen peroxide water, the hydrogen water cleaning can reduce the amount of the high concentration chemical solution to almost zero and can be used for rinsing. The amount of ultrapure water used can be overwhelmingly reduced, and the burden of waste liquid treatment can be made extremely small. Therefore, this technology has a very high advantage in terms of cost and environmental impact. I can say that.

  Here, the mechanism of particle removal will be compared and described in more detail for chemical cleaning and hydrogen water cleaning represented by SC1.

  In chemical cleaning, particles are detached from the surface of the object to be cleaned (lift-off) by dissolving (etching) the surface of the object to be cleaned and, in some cases, the surface of the adhering particles with chemicals. ) For this reason, in chemical cleaning, it is possible to desorb particles regardless of how the particles adhere to the surface of the object to be cleaned.

  On the other hand, in hydrogen water cleaning, very active hydrogen radicals generated in hydrogen water by applying ultrasonic waves are combined with dangling bonds to inactivate, or are replaced with atoms at the end of the interface. A chemical reaction is caused, and the particles are detached together with the peeling effect due to the generation of microbubbles at the interface and the vibration acceleration effect inherent in ultrasonic cleaning.

  Therefore, hydrogen water cleaning is effective when particles are adsorbed on the surface of the object to be cleaned by electrostatic attraction such as van der Waals force, but between the particles and the object to be cleaned. In the case where chemical bonds are formed on the two or when both are mechanically fixed, it becomes difficult to separate the particles.

  For example, a process of cleaning a semiconductor wafer after completion of chemical mechanical polishing (CMP) for flattening the surface of the semiconductor wafer will be described.

  In general, in CMP, polishing is performed using a polishing composition (slurry). The slurry is composed of abrasive grains made of diamond, silica, or the like, and a liquid component that disperses them. A chemical solution such as an oxidizing agent, a reducing agent, an etching agent, or a corrosion inhibitor is added to the liquid component according to the purpose.

  In order to perform CMP, a polishing pad and a semiconductor wafer are brought into contact with each other, and a slurry is supplied to an interface between the polishing pad and the semiconductor wafer to cause frictional movement therebetween. Depending on the movement, the semiconductor wafer surface is mechanically polished depending on the abrasive grains in the slurry, and depending on the chemical contained in the liquid component in the slurry, the semiconductor wafer surface is chemically converted, or The surface is flattened by polishing.

  After the CMP process is completed, it is necessary to clean the wafer surface and remove the adhered slurry. However, the abrasive grains are pressed against the wafer surface at a constant pressure during polishing, and the chemicals contained in the slurry are present at the interface between the abrasive grains and the wafer surface. It adheres firmly. Therefore, even if the wafer after CMP is washed with hydrogen water as it is, the abrasive grains adhering to the wafer surface cannot be easily removed.

  However, by applying the physical force to the abrasive grains and separating the strong adhesion between the abrasive grains and the wafer surface, the cleaning function of hydrogen water reveals the inherent particle removal function, and a large cleaning. An effect can be obtained.

  An example of the method will be described with reference to FIG. 8 which is an explanatory view of brush cleaning using hydrogen water. The wafer 201 to be cleaned is supported and rotated by some method. Brushes 202 are brought into contact with both surfaces of the wafer 201. The brush 202 is a cylindrical roller made of, for example, a soft polyvinyl alcohol (PVA) sponge, and is rotatable about an axis. Furthermore, both front and back surfaces of the wafer 201 are jetted with hydrogen water from a nozzle 203 (the back surface is omitted). The nozzle 203 can apply an ultrasonic wave to the liquid to be jetted, and the ultrasonic wave propagates through the jetted liquid to reach the wafer 201.

  The hydrogen water used here may be produced by the method described with reference to FIG. 7, and ammonia may be added as necessary. Hydrogen water to which ultrasonic waves are applied is sprayed from the nozzle 203 while rotating the wafer 201 and the brush 202, respectively. Accordingly, a force generated by friction with the brush 202 acts on the abrasive grains firmly fixed on the surface of the wafer 201, and the abrasive grains are released from the surface of the wafer 201. The effect of the hydrogen water described above is sufficiently exerted on the abrasive grains that are no longer firmly fixed to the surface of the wafer 201, and the abrasive grains are efficiently removed from the surface of the wafer 201.

  The friction on the wafer surface due to the brush is also realized by the method described in FIG. 9, which is another explanatory view of the brush cleaning using hydrogen water. As in the example of FIG. 8, the brush 302 made of, for example, PVA sponge rotates around an axis while being in contact with the surface of the rotating wafer 301, and generates friction between the surface of the wafer 301. While maintaining this state, the brush 302 moves on the wafer 301 and rubs the entire surface of the wafer 301. As in the example of FIG. 8, hydrogen water is supplied to the surface of the wafer 301 from a nozzle 303 that can apply ultrasonic waves to the liquid to be ejected, and is assisted by the action of frictional force by the brush 302 from the surface of the wafer 301. Abrasive grains are removed.

  Such a cleaning method, that is, a method of cleaning a substrate using hydrogen water and a brush while applying an ultrasonic wave is known (see, for example, Patent Document 4).

  Now, when the method described with reference to FIG. 8 or FIG. 9 is used to remove abrasive grains using friction with the brush, depending on the combination of the abrasive grains, the wafer surface, and the material of the brush, There is a problem of generating scratch marks.

In addition, it is not limited to the cleaning of the slurry after CMP, and as a general problem, when removing the particles firmly fixed on the surface of the object to be cleaned by the hydrogen water cleaning, a dynamic contact with the brush as described above is required. When friction is used, not only scratches are generated on the surface of the object to be cleaned, but also when a fine structure such as a pattern is formed on the surface of the object to be cleaned, the structure is brushed. There is also a problem that it is damaged due to friction.
Japanese Patent No. 281887 Japanese Patent No. 3521393 Japanese Patent No. 3296405 JP 2004-96055 A H. Morita, et al, “Particle Removable Mechanism of Hydrogenated Ultrapure, Water with Meganestic Irradiation,” 5th International Symposium on Ultra.

  In the present invention, in cleaning with hydrogen water, it is possible to apply a physical force without damaging the surface of the object to be cleaned, and particles adhering to the surface of the object to be cleaned are removed. Easily release and try to improve the effect of hydrogen water cleaning.

In the cleaning apparatus and a cleaning method according to the present invention, the cleaning apparatus and a cleaning method the cleaning object cleaning liquid is supplied to the cleaning bath contained is by applying ultrasonic waves to the cleaning liquid cleaned object to be cleaned However, it is fundamental to use a brush that vibrates in contact with the object to be cleaned.

  By adopting the above means, by applying a physical force to the surface of the object to be cleaned, the firmly fixed particles can be easily released from the surface. Can be easily removed by cleaning, and the physical force is not a dynamic frictional force but a static stress, which can damage the surface of the object to be cleaned There is nothing.

  The hydrogen water cleaning technology is an excellent cleaning technology in terms of cost and environmental load. By integrating such a hydrogen water cleaning technology and the technology of the present invention, the original hydrogen water cleaning technology is It is recognized that the effect can be further enhanced and the applicable fields will be broader.

  FIG. 1 is a cutaway side view for explaining the principle of a cleaning apparatus according to the present invention. In the figure, 401 is a semiconductor wafer, 402 is a cleaning tank, 403 is a water supply pipe, 404 is an ultrasonic transducer, 405 Denotes a brush, 406 denotes a vibration generator, and 407 denotes a diaphragm.

  Here, a case where a semiconductor wafer 401 is picked up as an example of a plate-like object to be cleaned and cleaned with hydrogen water will be described.

  A water supply pipe 403 is connected to the lower part of the cleaning tank 402 whose upper part is open, and hydrogen water is supplied from the water supply pipe 403 to fill the inside of the cleaning tank 402. An ultrasonic vibrator 404 is installed on the bottom surface of the cleaning tank 402, and the vibration propagates through the hydrogen water as ultrasonic waves.

  Inside the cleaning tank 402 filled with hydrogen water, a wafer 401 as an object to be cleaned and a brush 405 having a flat portion capable of contacting the entire surface of the wafer 401 are arranged in parallel to face each other. . The brush 405 is made of a very soft material such as PVA sponge, and is fixed on the vibration plate 407 of the vibration generator 406. When the vibration generator 406 operates, the vibration plate 407 vibrates, and the vibration is the brush 405. Will be conveyed to the whole.

  Further, the wafer 401 and the brush 405 are supported by a mechanism capable of changing the relative distance while keeping the directions of both in parallel, and the two can be periodically approached and separated. is there. When they are closest to each other, the planar portion of the brush 405 uniformly contacts the entire surface of the wafer 401.

  Therefore, the vibration of the brush 405 is well transmitted to the surface of the wafer 401, and a stress that varies periodically and finely is applied to the particles fixed on the surface of the wafer 401, so that the particles and the wafer 401 are firmly fixed. And the particles can be easily detached from the surface of the wafer 401 by the effect of washing with hydrogen water.

  Friction motion due to this vibration does not occur, and only the stress other than the frictional force that periodically changes is applied to the particles. That is, at the contact interface where the brush 405 and the wafer 401 are in contact with each other, any vibration in the brush 405 causes any deviation in the relative positional relationship between the brush 405 and the wafer 401. The vibration is controlled so that it does not occur and does not occur. Therefore, the surface of the wafer 401 is not damaged such as a friction mark.

  Further, when the brush 405 is separated from the wafer 401, a hydrogen water cleaning function appears. That is, the ultrasonic wave generated by the ultrasonic transducer 404 propagates in the hydrogen water to generate active hydrogen radicals in the hydrogen water, and the particles are desorbed and removed from the surface of the wafer 401 by its action.

  FIG. 2 is a cutaway side view of a main part of a wafer cleaning apparatus for explaining an embodiment of the present invention, and will be described below with reference to the drawings. Here, hydrogen water whose dissolved hydrogen concentration is controlled is shown. It shall be manufactured by existing means and supplied to the cleaning device. In addition, it is assumed that an alkali such as ammonia is added to this hydrogen water for the purpose of adjusting pH, and the concentration thereof is appropriately controlled. For a specific configuration in the case where hydrogen water or hydrogen water to which ammonia is added is manufactured and supplied to the cleaning device, the configuration described with reference to FIG. 7 will be helpful.

  The essential elements of the present invention are the action of a physical force in which the effect of cleaning with hydrogen water and the surface of the object to be cleaned are almost only tangential stress or shear stress, and therefore normal stress is extremely fine. It can be divided into parts to give. First, a mechanism for producing the effect of hydrogen water cleaning will be described.

  The wafer 501 that is the object to be cleaned is cleaned by immersing it in the hydrogen water 503 filling the inside of the quartz cleaning tank 502. Hydrogen water 503 produced by the hydrogen water production apparatus is introduced into the bottom of the quartz cleaning tank 502 through the water supply pipe 504, and is ejected into the quartz cleaning tank 502 from a plurality of holes 505 formed in the water supply pipe 504. To do.

  The hydrogen water 503 flows from the lower part to the upper part of the quartz cleaning tank 502 and overflows from the opening on the upper surface of the quartz cleaning tank 502 (overflow). By doing in this way, the hydrogen water 503 in the quartz cleaning tank 502 is continuously replaced with a newly supplied one and does not stay in the quartz cleaning tank 502.

  The quartz cleaning tank 502 is supported by a support column 507 provided in a stainless steel outer tank 506. An ultrasonic transducer 508 is installed on the bottom surface of the outer tank 506, and an ultrasonic wave is generated by applying a high frequency signal generated by an external oscillator 509 and vibrating.

  The outer tank 506 is always filled with water 510, and the ultrasonic waves generated by the ultrasonic vibrator 508 propagate through the water 510 and further pass through the bottom surface of the quartz cleaning tank 502, Propagates to the internal hydrogen water 503.

  The purpose of applying ultrasonic waves to the hydrogen water 503 with the ultrasonic vibrator 508 is to generate surplus hydrogen radicals inside the hydrogen water 503 together with the normal ultrasonic cleaning effect, and to obtain the hydrogen water cleaning effect described above. It is in. And if the frequency of an ultrasonic wave is 20 kHz-30 kHz or more, it is supposed that it has the effect of generating a surplus hydrogen radical.

  However, when the frequency of the ultrasonic wave is in the range of about 20 kHz to 30 kHz to 100 kHz, the influence of the shock wave locally generated by the generation and disappearance of cavitation (cavity) caused by the ultrasonic wave is strong, and damage to the wafer 501 is caused. large. For this reason, the frequency of the ultrasonic wave generated by the ultrasonic vibrator 508 is preferably in the range of 500 kHz to 2 MHz to 3 MHz called megasonic that reduces damage to the wafer 501.

  Next, a mechanism for applying a physical force to the surface of the wafer 501 that is the object to be cleaned in this embodiment will be described.

  In this embodiment, the surface of the wafer 501 is subjected to a physical force by bringing the brush 511 into contact with the wafer 501 and the entire surface of the wafer 501 with a plane portion having a width that can be contacted at a time, and vibrating the brush 511. Gives action. The brush 511 is fixed on the vibration plate 513 of the vibration generating device 512. When the vibration generating device 512 is operated, the vibration plate 513 vibrates, and accordingly, the entire brush 511 vibrates.

  The vibration of the vibration plate 513 in the vibration generator 512 is controlled by, for example, amplifying an arbitrary waveform signal generated by the signal generator 514 by the amplifier 515 and then transmitting it to the vibration generator 512. The wafer 501 is held by a wafer holder 516 provided with a claw 517 for holding the wafer 501.

  Wafer holder 516 and vibration generator 512 are fixed to reciprocating mechanism 519 by arm 518 so that wafer 501 and brush 511 face each other in parallel. The reciprocating mechanism 519 can freely move the arm 518 so that the relative distance between the wafer 501 and the brush 511 is changed while maintaining the directions of the wafer 501 and the brush 511 in parallel.

  The movement of the arm 518 is controlled by a control device 520 having a computer. For example, the reciprocating mechanism 519 can periodically approach and separate both the wafer 501 and the brush 511 so that the planar portion of the brush 511 uniformly contacts the entire surface of the wafer 501 when both approach each other.

  If the operation of the signal generator 514 or the amplifier 515 that drives the vibration generator 512 is also controlled by the control device 520, the operation of the diaphragm 513 can be linked with the operation of the arm 518. For example, an operation that vibrates the diaphragm 513 is possible only when the brush 511 is in contact with the wafer 501.

  As a material of the brush 511, PVA sponge is used in the present embodiment, but is not limited to PVA sponge, and may be a porous sponge-like material. In short, since the surface of the wafer 501 is not damaged, a soft material made of resin is preferable. For example, polyurethane foam may be used.

  FIG. 3 is an explanatory view of a main part showing the detailed structure of the vibration generator 512 shown in FIG. In the figure, a brush 601 that contacts the wafer is fixed to a diaphragm 602. A support rod 603 is attached to the diaphragm 602 to support the diaphragm 602 when the brush 601 comes into contact with the wafer and prevent the diaphragm 602 from sinking into the housing 604. The tip of the support bar 603 can move freely along the wall surface without being fixed to the inner wall surface of the housing 604, and thus does not interfere with the vibration of the diaphragm 602.

  The vibration power of the diaphragm 602 is generated by the magnetic force acting between the coil 605 and the magnetic circuit 606. The coil 605 is fixed to the diaphragm 602, and the magnetic circuit 606 is fixed to the housing 604. A magnetic circuit 606 that is a permanent magnet is inserted into a cavity of a coil 605 wound in a cylindrical shape. The coil 605 is connected to an external signal source (for example, the signal generator 514 and the amplifier 515 shown in FIG. 2) via the cable 607. When a time-varying signal current is sent from an external signal source to the coil 605, a time-varying magnetic field is generated in the coil 605, and this magnetic field and the magnetic field generated by the magnetic circuit 606 interact with each other. The coil 605 vibrates, and the vibration plate 602 vibrates with the vibration.

  In this embodiment, it is necessary for the brush 601 to vibrate with a lateral movement component in FIG. 3, so the coil 605 and magnetic circuit 606 are installed in the orientation shown in FIG. Yes. Further, by installing a plurality of sets of the coil 605 and the magnetic circuit 606 in different directions, the vibration of the diaphragm 602 is not a simple vibration in only one direction but a vibration having components in a plurality of directions. This is preferable.

  In this embodiment, the vibration generator (see FIGS. 2 and 3) is operated in a submerged state. For this reason, a support sheet 608 is attached to a gap generated between the diaphragm 602 and the housing 604 to fix the positional relationship between the housing 604 and the diaphragm 602 and prevent water from entering from the outside. The support sheet 608 has a structure in which the diaphragm 602 can vibrate in the lateral direction of FIG. 3 using a fluororesin sheet or the like molded into a corrugated plate.

  As for the frequency of the vibration of the brush 601, as a result of experiments, for example, vibration with a small amplitude and high frequency such as vibration generated by an ultrasonic vibrator is absorbed by a soft material such as PVA sponge, and particles on the wafer surface. As a result, it was found that a sufficient effect can be obtained with vibrations at frequencies up to about 100 Hz in order to achieve the object of the present invention. . Thus, for example, when a vibration is generated by adopting a structure including a voice coil, a diaphragm, and a magnetic circuit in a speaker used as an acoustic device, the removal of particles can be realized extremely well. However, the present invention is not limited to the illustrated and described means as long as an appropriate magnitude of vibration can be applied to the brush 601.

  FIG. 4 is an explanatory view of the main part showing the detailed structure of the reciprocating mechanism 519 shown in FIG. 2. Two frames 701 are connected by two parallel shafts 702, and male screws are attached to the shaft 702. Cut screw rods 703 are installed in parallel. The screw rod 703 is supported by a frame 701 via a bearing and can be freely rotated. One end of the screw rod 703 is connected to the motor 704, and the motor 704 rotates the screw rod 703.

  A movable pedestal 705 is installed between the two frames 701, two guide holes 706 are formed in the movable pedestal 705, and the shaft 702 passes therethrough. The movable base 705 has a screw hole 707 in which a female screw is cut, and a screw rod 703 is inserted therein. When the motor 704 is rotated, the movable pedestal 705 moves freely along the shaft 702. The motor 704 is connected to an external control device (eg, the control device 520 seen in FIG. 2) via a cable 708. The position and moving speed of the movable base 705 can be precisely controlled by controlling the rotation amount and rotation speed of the motor 704 according to the control device.

  For example, by fixing one of the arms 518 shown in FIG. 2 to the frame 701 shown in FIG. 4 and the other to the movable base 705, the wafer described with reference to FIG. The approach and separation between the 501 and the brush 511 can be realized.

  With reference to FIG. 2 again, the actual cleaning operation according to the present invention will be described while explaining the cleaning experiment performed in the present embodiment.

  A silicon wafer having a diameter of about 20 cm (8 inches) is used as a substrate, and a Cu film having a thickness of 2 μm is formed on the outermost surface by electroplating. The surface of the Cu film is polished by applying a CMP method using slurry containing abrasive grains made of fused quartz and having an average particle size of 0.15 μm. Note that conventional techniques may be applied to electroplating and CMP.

  An experiment was conducted to clean and remove the abrasive grains adhering to the surface of the Cu film immediately after the CMP.

  The apparatus configuration and setting in this case will be described. First, hydrogen water 503 having a dissolved hydrogen concentration of 1.5 ppm was supplied to a quartz cleaning tank 502 having a volume of 15 liters at a flow rate of 10 liters / minute. Hydrogen water 503 was allowed to overflow from the upper opening of the quartz cleaning tank 502 to the outside of the tank. The ultrasonic vibrator 508 installed below the quartz cleaning tank 502 was vibrated, and megasonic was applied to the hydrogen water 503. The frequency was 750 kHz and the output was 600 W.

  The vibration generator 512 includes a combination of a coil and a magnetic circuit that generate vibration components in two directions. A sine wave current that fluctuates at 50 Hz is generated by the signal generator 514, the amplitude is appropriately amplified by the amplifier 515, and the coil of the vibration generator 512 is energized. A disc-shaped PVA sponge having a thickness of 15 mm and a diameter of about 22 cm (8.5 inches) when softened in water was fixed as a brush 511 on the vibration plate 513 of the vibration generator 512.

  The wafer 501 to be cleaned is placed in the wafer holder 516, and the reciprocating mechanism 519 causes the brush 511 to vibrate while approaching the wafer 501 and bringing it into contact with the wafer 501. I did it. The center of the wafer 501 and the center of the brush 511 are placed on the same straight line, and the brush 511 is in uniform contact with the entire surface of the wafer 501.

  FIG. 5 is a main part explanatory view for explaining the relative positional relationship between the wafer 501 and the brush 511. In this embodiment, the position of the wafer 801 is fixed, and only the diaphragm 803 reciprocates. (A) shows the state in which the surface of the wafer 801 and the vibration plate 803 are farthest apart, and the distance L1 is set to 33 mm. At this time, the distance L2 between the surface of the wafer 801 and the surface of the PVA sponge is 18 mm, and the space between the two is filled with hydrogen water. (B) shows a state in which the vibration plate 803 is closest to the surface of the wafer 801, and the distance L3 is set to 13 mm. In this state, the surface of the PVA sponge 802 comes into contact with the surface of the wafer 801 and is further pushed in by the amount that the thickness of the PVA sponge 802 is reduced by 2 mm. The diaphragm 803 reciprocates with an amplitude of 20 mm depending on the operation of the reciprocating mechanism, and reciprocates between the states shown in FIGS.

  FIG. 6 is a diagram showing the state of reciprocating motion of the reciprocating mechanism. The horizontal axis represents time (seconds), and the vertical axis represents the relative distance value (mm) between the surface of the wafer 801 and the diaphragm 803. Each is taken. The diaphragm 803 is set to move at a speed of 20 mm / second. Further, in the states of FIGS. 5A and 5B, the diaphragm 803 is set to be stationary for 1 second.

  As described above, under the apparatus configuration described above, an experiment was conducted to clean and remove the abrasive grains adhering to the surface of the Cu film immediately after CMP. The evaluation in this case is performed by measuring and comparing the number of abrasive grains adhering to the surface of the Cu film before and after cleaning, and the number of abrasive grains is measured by a wafer surface inspection apparatus. It was.

  First, hydrogen water cleaning was performed for 1 minute using only the megasonic applied by the ultrasonic vibrator 508 without bringing the vibrating brush 511 into contact with the wafer 501. As a result, only about 20% of the abrasive grains could be removed. It was estimated that the abrasive grains were firmly fixed on the Cu film surface.

  Next, the vibration plate 513 is closest to the wafer 501 and the brush 511 is in contact with the wafer 501, that is, the state shown in FIG. 5B, and the vibration generator 512 applies vibrations of 50 Hz for 1 minute. Hydrogen water washing was performed. As a result, only about 8% of the abrasive grains were removed. Even if the amplitude of the diaphragm 513 was changed by changing the amplification factor in the amplifier 515, and the frequency of the sine wave generated by the signal generator 514 was raised or lowered from 50 Hz, the removal rate hardly changed. . It was found that no cleaning effect could be obtained if the brush 511 remained in contact.

  Therefore, hydrogen water cleaning was performed for 1 minute using the reciprocating mechanism 519 while reciprocating as seen in the diagram of FIG. 6 while the brush 511 was vibrated at 50 Hz. As a result, 95% of the abrasive grains could be removed. This is because the adhesion between the surface of the Cu film and the abrasive grains is released by the vibration of the brush 511, and further, the effect of removing the abrasive grains from the surface of the Cu film by the effect of washing with hydrogen water. It is recognized that it was demonstrated.

  However, as a result of cleaning under these conditions, it has been found that many fine scratch marks are generated on the surface of the Cu film after cleaning. When a detailed analysis was performed, intense dynamic friction occurred between the surface of the brush 511 contacting the surface of the wafer 501 and the moment of separation, and scratches were generated due to this friction. It was found to occur. Further, in a state where the brush 511 is sufficiently in contact with the surface of the wafer 501, even if the vibration plate 513 is vibrated, the brush 511 and the surface of the wafer 501 remain in close contact, and friction is not generated at the contact interface between them. It has also been found that only static stress that changes with time is acting on the surface of the wafer 501.

  Therefore, when the computer of the control device 520 is used, the vibration plate 513 is closest to the wafer 501 and the brush 511 is sufficiently in contact with the surface of the wafer 501, that is, in the state shown in FIG. 5B. Only the vibration generator was operated to vibrate the brush 511, and control was performed to stop the vibration of the brush 511 at other times. That is, in FIG. 6, the brush 511 is vibrated only in the section indicated by the thick line on the horizontal axis. Under this setting, cleaning with hydrogen water for 1 minute was performed, and there was no scratch mark while recording an abrasive removal rate of approximately 96%.

  Further, the frequency of the sine wave signal generated by the signal generator 514 was fixed to 50 Hz, the amplification factor of the amplifier 515 was changed, and the amplitude of the brush 511 was changed to perform the hydrogen water cleaning. As a result, in the region where the amplitude is small, the abrasive grains can hardly be removed. On the other hand, when the amplitude exceeds a certain size, the removal rate of the abrasive grains rapidly increases and reaches 96% under the above conditions. The removal rate rose to near%. However, when the amplitude was further increased, dynamic friction began to occur at the interface between the brush 511 and the wafer 501, and minute scratch marks were generated on the surface of the Cu film after cleaning. As described above, in this embodiment, dynamic friction is generated at the interface between the brush 511 and the wafer 501 by optimizing the amplitude and frequency of vibration of the brush 511. And a removal rate of nearly 100% abrasive grains was obtained.

  Further, as a result of examining the frequency of the sine wave signal generated by the signal generator 514, the frequency increases and the vibration of the diaphragm 513 is more likely to be absorbed inside the brush 511, and sufficient stress is applied to the wafer 501. It was also found that it was not added to the surface, and the cleaning effect by hydrogen water could not be obtained. The material of the brush 511, that is, the PVA sponge here varies depending on the properties as an elastic body and the outer dimensions and particularly the thickness of the brush 511, but the upper limit of the vibration frequency of the diaphragm 513 is high. 1 kHz is the limit. Of course, in each frequency setting, it is necessary to optimize the amplitude of vibration so as to efficiently obtain the cleaning effect by the hydrogen water as described above.

  In this embodiment, as described above, using the computer of the control device 520, the vibration generator 512 is operated to vibrate the brush 511 only when the brush 511 is sufficiently in contact with the surface of the wafer 501. Was controlled so that the brush 511 was not vibrated. This control may be performed by issuing an on / off command to the vibration generator 512 in accordance with the relative positional relationship between the brush 511 and the wafer 501. In addition, a sensor that senses the stress (pressure) generated between the brush 511 and the wafer 501 when the brush 511 and the wafer 501 are in contact with the reciprocating mechanism 519 or the like is provided. A control method may be performed such that the vibration generator 512 is operated only for a time exceeding a certain value.

  The cleaning apparatus and the cleaning method described here can sufficiently exhibit the cleaning effect not only when cleaning with hydrogen water but also when using a cleaning liquid such as a conventional chemical solution.

  In the present invention, the present invention can be implemented in many forms including the above-described embodiment, which will be exemplified below as supplementary notes.

(Appendix 1)
In a cleaning device that supplies cleaning liquid into a cleaning tank containing the object to be cleaned and applies ultrasonic waves to the cleaning liquid to clean the object to be cleaned, a brush that vibrates in contact with the object to be cleaned is provided. A cleaning apparatus characterized by that.

(Appendix 2)
The cleaning apparatus according to (Appendix 1), wherein the brush is made of an elastic body.

(Appendix 3)
The cleaning device according to (Appendix 2), wherein the elastic body is made of a resin and has a porous sponge shape.

(Appendix 4)
The cleaning apparatus according to any one of (Appendix 1) to (Appendix 3), wherein the vibration frequency of the brush is 1 kHz or less.

(Appendix 5)
The cleaning liquid supplied to the cleaning tank is gas-dissolved water that is ultrapure water in which a specific type of gas is dissolved or gas-dissolved water in which pH is adjusted by dissolving a specific alkali (Appendix 1) to The cleaning apparatus according to any one of (Appendix 4).

(Appendix 6)
A mechanism is provided for alternately repeating a process in which the object to be cleaned and the brush are in contact with each other for a certain period of time and the brush vibrates and a process in which the brush is not in contact with each other for a certain period of time (Appendix 1). The cleaning apparatus according to any one of (Appendix 5).

(Appendix 7)
The time for which the brush vibrates is provided with a mechanism that limits the time so that the brush starts immediately after the start of the process of contacting the object to be cleaned and ends immediately before the end of the process (Appendix 6). Cleaning device.

(Appendix 8)
In a cleaning method in which cleaning liquid is supplied into a cleaning tank in which the object to be cleaned is stored and ultrasonic waves are applied to the cleaning liquid to clean the object to be cleaned, cleaning is performed with the vibrating brush in contact with the object to be cleaned. Cleaning method characterized by performing.

(Appendix 9)
The cleaning liquid supplied to the cleaning tank is gas-dissolved water that is ultrapure water in which a specific type of gas is dissolved or gas-dissolved water in which pH is adjusted by dissolving a specific alkali (Appendix 8) Cleaning method.

(Appendix 10)
(Appendix 8) or (Appendix 9), wherein the object to be cleaned and the brush are in contact with each other for a predetermined time and the brush vibrates and the process in which the brush is not in contact for a predetermined time are alternately repeated. Cleaning method.

(Appendix 11)
The cleaning method according to (Appendix 10), characterized in that the time during which the brush vibrates starts immediately after the start of the step in which the brush contacts the object to be cleaned and ends immediately before the end of the step.

(Appendix 12)
The cleaning is performed without generating dynamic friction at the contact interface between the brush and the object to be cleaned while the brush is in contact with the object to be cleaned and is vibrating (Appendix 11) Cleaning method.

(Appendix 13)
The cleaning method according to any one of (Appendix 8) to (Appendix 12), wherein the gas-dissolved water that is a cleaning liquid supplied into the cleaning tank is obtained by dissolving hydrogen gas in ultrapure water.

It is a principal part cutting side view explaining the principle of the washing | cleaning apparatus by this invention. It is a principal part cutting side view of the wafer cleaning apparatus for demonstrating one Example of this invention. FIG. 3 is a main part explanatory view showing a detailed structure of the vibration generating device seen in FIG. 2. It is principal part explanatory drawing showing the detailed structure of the reciprocation mechanism seen in FIG. It is principal part explanatory drawing for demonstrating the relative positional relationship of a wafer and a brush. It is a diagram showing the state of the reciprocating motion of a reciprocating motion mechanism. It is a principal part block diagram showing an example of the ultrasonic cleaning apparatus using hydrogen water. It is explanatory drawing of the brush washing | cleaning using hydrogen water. It is explanatory drawing of the brush washing | cleaning using hydrogen water.

Explanation of symbols

401 Wafer 402 Cleaning tank 403 Water supply pipe 404 Ultrasonic vibrator 405 Brush 406 Vibration generator 407 Vibration plate

Claims (4)

In a cleaning apparatus for supplying a cleaning liquid into a cleaning tank containing an object to be cleaned, and applying ultrasonic waves to the cleaning liquid to clean the object to be cleaned.
A brush that vibrates in contact with an object to be cleaned after CMP ;
After contacting the brush and the object to be cleaned, the brush is vibrated for a certain period of time, and after the certain period of time has elapsed, the vibration of the brush is stopped, and the vibration of the brush is stopped. And a mechanism for alternately repeating the step of separating the brush and the object to be cleaned and not contacting each other for a certain period of time . The cleaning apparatus according to claim 1, wherein the brush is an elastic body. The cleaning liquid supplied to the cleaning tank is gas-dissolved water that is ultrapure water in which a specific type of gas is dissolved or gas-dissolved water in which a specific alkali is dissolved to adjust the pH. Item 3. A cleaning device according to Item 2. Supplying a cleaning liquid into the cleaning tank and applying ultrasonic waves to the cleaning liquid;
Soaking the object to be cleaned subjected to CMP in the cleaning liquid to which the ultrasonic wave is applied;
A step of bringing a brush into contact with the object to be cleaned after soaking the object to be cleaned;
After contacting the brush, vibrating the brush for a certain period of time;
Stopping the vibration of the brush after the predetermined time has elapsed;
After stopping the vibration of the brush, separating the brush and the object to be cleaned,
A cleaning method comprising repeating the step of bringing the brush into contact, the step of vibrating the brush, the step of stopping the vibration of the brush, and the step of separating the brush from the object to be cleaned.

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