JP5169264B2 - Cleaning device - Google Patents

Description

  The present invention relates to a cleaning apparatus, and more particularly, to an ultrasonic cleaning apparatus with high cleaning efficiency suitable for cleaning a thin plate substrate such as a semiconductor wafer or a glass substrate, which is performed in a manufacturing process of various electronic devices.

  In the manufacture of semiconductor elements, the wafer size is becoming larger. Along with this, in the wafer cleaning process, from the conventional dip method cleaning in which a plurality of wafers are immersed in a large cleaning tank and the cleaning liquid is vibrated ultrasonically, the wafers are single wafer type. Spin-type cleaning, which is performed while supplying itself, for example, a cleaning liquid with increased water pressure or a cleaning liquid that has been vibrated with ultrasonic waves, is becoming the mainstream. This single-wafer spin cleaning method is easier to perform uniform cleaning on the wafer surface than the dip cleaning method, and contaminants removed from the wafer surface are less likely to adhere to the wafer surface. There are many advantages such as the ability to further reduce the amount of pure water used for rinsing and the startup of the cleaning device in a shorter time. Among these, the single wafer spin cleaning apparatus to which ultrasonic cleaning is applied has been applied in many large-diameter wafer cleaning processes and the like.

  Such single-wafer ultrasonic spin cleaning apparatuses include a so-called ultrasonic nozzle type single-wafer ultrasonic spin cleaning apparatus that injects a cleaning liquid from an ultrasonic nozzle onto the surface of a rotating wafer. In this method, ultrasonic waves are generated by oscillating a vibrator inside the ultrasonic nozzle, and ultrasonic waves are propagated to the wafer surface using the jet cleaning liquid as a medium. Is what you do.

  FIG. 6 shows a schematic diagram of this ultrasonic nozzle type single wafer ultrasonic spin cleaning apparatus. As shown in FIG. 6, the cleaning liquid 103 is sprayed from the ultrasonic nozzle 101 having a built-in ultrasonic transducer (not shown) toward the surface of the wafer 102 that is the cleaning target. When the ultrasonic transducer in the ultrasonic nozzle 101 is operated, the generated ultrasonic wave propagates to the surface of the wafer 102 using the cleaning liquid 103 as a medium. In a situation where the wafer 102 is rotated by a wafer mounting means such as a wafer mounting table (not shown), the region where the cleaning liquid 103 hits the surface of the wafer 102, that is, the ultrasonic irradiation region 104 reciprocates between the central portion and the outer peripheral portion of the wafer 102. Thus, if the reciprocating motion is performed using an ultrasonic nozzle holder such as an ultrasonic nozzle holder (not shown), the ultrasonic irradiation region 104 scans the entire surface of the wafer 102, and the entire surface of the wafer 102 is cleaned. The Rukoto.

  By the way, in recent years, with the progress of miniaturization and high integration of semiconductor elements, the application of low dielectric constant insulating materials has been promoted due to the demand for thinning the interlayer insulating film of the elements and reducing the parasitic capacitance. As such an insulating material, for example, there is a porous silica (porous silica) material in which fine pores (pores) are uniformly distributed inside. This porous silica film is formed by reactive dry etching, and, for example, a wafer having a fine pattern of 100 nm or less formed on the surface is cleaned by the above-described ultrasonic nozzle type single wafer ultrasonic spin cleaning apparatus. Then, due to the relatively large ultrasonic damage caused by the jetted ultrasonic cleaning water, the fine pattern may be destroyed due to the brittleness of this material.

  A direct method for avoiding the destruction of such fragile fine patterns requires reducing the ultrasonic energy per unit area irradiated to the wafer surface according to the structural vulnerability of the pattern. Therefore, it is possible to adjust the drive output of the ultrasonic transmitter that drives the ultrasonic transducer built in the ultrasonic nozzle 101.

  Although it is possible to reduce the output by adjusting the drive output like this, as a practical matter, it is stable when the drive output falls below a certain lower limit from the inherent ultrasonic vibration conditions determined by the shape and structure of the built-in ultrasonic transducer. The obtained ultrasonic vibration cannot be obtained. In addition, when driven at a high ultrasonic frequency, when the drive output of the ultrasonic transducer falls below a certain level, the attenuation of the ultrasonic wave in the cleaning liquid ejected from the ultrasonic nozzle increases rapidly, and the ultrasonic wave is generated. It may also happen that the wafer surface is not reached. For this reason, this ultrasonic nozzle type single wafer ultrasonic spin cleaning apparatus has many inconvenient points to clean the wafer surface by operating the vibrator with a very small driving output.

  Therefore, as a method for reducing the damage of ultrasonic waves given to the wafer surface, a method of irradiating the wafer surface with ultrasonic waves using an ultrasonic vibrating body (ultrasonic vibration transmission plate) is considered (for example, Patent Document 1). 2 etc.).

  FIG. 7 shows a typical example. FIG. 7A is a schematic view of an ultrasonic vibrator type single-wafer ultrasonic spin cleaning apparatus, and FIG. 7B is an enlarged cross-sectional view of a main part. As shown in FIG. 7A, an ultrasonic transducer 106 is attached to one of the flat surfaces of a vibrating body 105 (for example, a ceramic material) having a triangular prism shape, for example. Further, as shown in the figure, the vibrating body 105 is held by the vibrating body support means 107 so that one of the other flat surfaces of the vibrating body 105 is parallel to the surface to be cleaned of the wafer 102 and faces a small distance. The cleaning liquid 103 is supplied from the cleaning liquid nozzle 108 so that the distance between the vibrating body and the wafer surface is completely filled with the cleaning liquid 103.

  With reference to FIG. 7B of the cross-sectional view, when the ultrasonic vibrator 106 is driven in such a state that the distance between the vibrating body and the wafer surface is completely filled with the cleaning liquid 103, the generated ultrasonic wave is generated by the vibrating body 105. The entire surface facing the wafer 102 propagates to the cleaning liquid 103 and further propagates through the cleaning liquid 103 to reach the surface of the wafer 102 that is the surface to be cleaned for cleaning. Since the vibration state of the surface of the vibrating body 105 facing the wafer 102 is determined by the vibration method of the ultrasonic vibrator 106 and the shape and material of the vibrating body 105, it can be predicted in advance by simulation. Therefore, it is reflected in the design of the vibrating body 105 according to each purpose. In this drawing, an example of a triangular prism-shaped vibrating body is shown, but the vibrating body shape is not limited to this, and, for example, a cylinder, a rectangular column, or the like can be applied. Further, it is not always necessary to incline the vibrating body, and it may be arranged vertically according to the application situation. Various materials such as vibratory materials have been studied.

In the method of propagating ultrasonic waves through the vibrating body as described above, since the ultrasonic vibration generated by the ultrasonic vibrator vibrates over the entire large area of the vibrating body, the energy of vibration is dispersed and the surface to be cleaned is dispersed. The ultrasonic energy irradiated per unit area is significantly smaller than that of the ultrasonic nozzle method, and there is an effect of reducing ultrasonic damage to the wafer surface.
JP 2003-181394 A JP 2003-31540 A

  However, the ultrasonic vibrating body type single-wafer ultrasonic spin cleaning apparatus as described above generally has a problem that the removal efficiency of foreign matters adhering to the wafer is low. When cleaning wafers with foreign matter attached to the surface under the same conditions, the ultrasonic vibrator type single wafer type ultrasonic spin cleaning device is compared with that of the ultrasonic nozzle type, several times until the equivalent foreign matter removal rate is obtained. It may take time.

  Therefore, even if fragile and fine patterns are formed on the wafer surface, the object of the present invention is to enable efficient cleaning that removes foreign matters on the wafer surface in a short time without destroying those patterns. Another object of the present invention is to provide an ultrasonic vibrator type single wafer ultrasonic spin cleaning apparatus.

The cleaning device of the present invention comprises:
A columnar vibrator arranged on the object to be cleaned;
The cleaning liquid discharged on the object to be cleaned has a cylindrical shape surrounding a side surface of the vibrating body, and a first flow that flows in a direction of a central axis of the vibrating body, and a direction opposite to the first flow A flow path through which the cleaning liquid passes so as to be diverted into a flowing second flow;
A passage formed in a region including the central axis of the vibrating body in the vibrating body and collecting the cleaning liquid forming the first flow ;
A cleaning apparatus comprising:

Also,
A support for supporting the object to be cleaned;
The apparatus further comprises a moving means for positioning the flow path and the object to be cleaned so as to face each other with a first interval.

Also,
The passage and the object to be cleaned are opposed to each other with a second interval larger than the first interval.

Also,
The passage is connected to suction means.

  By using the cleaning apparatus of the present invention, foreign matter such as fine particles adhering to the surface can be efficiently removed even in the case of a wafer or the like having a fine pattern that is fragile on the surface. The cleaning time can be shortened.

  As a result of the inventor's investigation, the reason for the low foreign substance removal efficiency in the ultrasonic vibrator method is not mainly due to the fact that the energy per unit area of the ultrasonic wave irradiated on the wafer surface is reduced. It has been clarified that the cause is that the foreign matter that is detached from the wafer surface and floats in the cleaning liquid easily adheres to the wafer surface due to the action of ultrasonic waves.

  First of all, the reason for the reattachment of foreign matters is the restriction imposed on the number of wafer rotations. In the cleaning method using the vibrating body, it is necessary to form a stable layer of the cleaning liquid 103 at a very small interval between the vibrating body 105 and the wafer 102 in FIG. 7, and for this purpose, the rotation speed of the wafer is constant. The rotation speed cannot be increased. For this reason, it is considered that the foreign matter is likely to be reattached while the cleaning liquid 103 containing the foreign matter stays on the wafer surface.

  The second reason is the problem of the flow of the cleaning liquid 103 at a minute interval between the vibrating body 105 and the wafer 102. In this minute interval, since it is necessary to propagate the weak ultrasonic vibration generated on the surface of the vibrating body 105 to the surface of the wafer 102 without being attenuated as much as possible, it is usually set to a very minute interval. For example, it is often set to an interval of several mm to 1 mm or less. For this reason, the flowing water resistance received by the cleaning liquid 103 in the interval between the vibrating body 105 and the wafer 102 is high, and the efficiency of replacing the cleaning liquid 104 inside and outside the gap is not good. For this reason, it is conceivable that the vibrating body 105 moves before the foreign matter released in the cleaning liquid 103 directly under the vibrating body 105 flows out of the gap together with the cleaning liquid 103, and the foreign matter reattaches to the surface of the wafer 102. It is done.

  Such a re-adhesion phenomenon naturally occurs even in the ultrasonic nozzle type cleaning method. However, it can be considered that the probability of reattachment in the method using the vibrating body is extremely high, and as a result, the removal efficiency of the foreign matter in the entire wafer is low. As a result, it takes a long time to process each sheet, and this low cleaning efficiency is a very serious problem in a single wafer processing apparatus.

  As described above, in a conventional wafer cleaning apparatus using a vibrating body, the cleaning liquid filling a minute gap sandwiched between the vibrating body and the wafer is detached from the wafer surface by the action of ultrasonic waves. As a result, the floating foreign matter is contained at a high concentration. If the cleaning liquid in this state is allowed to stay in this gap for a long time, the probability that the foreign matter will reattach to the wafer surface increases, and as a result, the cleaning time of the wafer surface becomes longer. Accordingly, it is necessary to discharge the cleaning liquid portion containing the foreign matter in a high concentration from the minute gap as quickly as possible while allowing the clean cleaning liquid to flow into the gap continuously. In other words, by continuously discharging and replacing the cleaning liquid filled in the minute gap where this ultrasonic vibration is activated, the foreign matter detached from the wafer surface by ultrasonic operation moves to other parts of the wafer. Thus, it is possible to prevent reattachment to the surface of the wafer.

  On the other hand, it is necessary that the entire surface of the wafer is always covered with a liquid such as a cleaning liquid so that the entire surface of the wafer is not dried until the cleaning process is completed. This is because, in spin cleaning in which the entire surface area is scanned while rotating (spinning) the wafer, one point on the wafer is usually cleaned repeatedly by the action of ultrasonic waves each time the vibrating body passes. Is done. At that time, if the surface of the wafer is dried between the cleaning and the next cleaning, the foreign matters in the cleaning liquid once removed are reattached to the surface of the wafer and fixed, and the effect of the cumulative cleaning performed repeatedly is obtained. This results in a loss of cleaning efficiency.

  In particular, in order to realize efficient cleaning for removing foreign substances by the ultrasonic vibrator type single-wafer ultrasonic spin cleaning apparatus, it is desirable to configure an apparatus that satisfies these two requirements simultaneously.

  Embodiments of the present invention that satisfy the above requirements will be described below with reference to the accompanying drawings.

(First embodiment)
FIG. 1 illustrates a basic configuration of a vibrating body for transmitting ultrasonic vibration through a cleaning liquid in contact with a wafer surface, its surrounding material, and a cleaning liquid flow path according to an embodiment of the present invention. The cross-sectional schematic diagram of is shown.

  Referring to FIG. 1, there is a vibrating body 2 and an outer casing 3 provided around the surface of the wafer 1. The vibrating body 2 is, for example, a cylinder with a diameter L facing one circular end surface portion to the wafer 1, and a passage 5 having a diameter P1 penetrating the center in the vertical direction. For example, the outer envelope 3 has a cylindrical shape that surrounds the outer circumference of the column of the vibrating body 2 with a gap 6 having a uniform width P2. The outer circumference of the cylinder has a diameter W and the thickness of the cylinder plate is T. In this case, the surfaces of the vibrating body 2 and the outer enclosure 2 facing the wafer 1 are arranged with a minute gap 4 having a gap distance S from the surface of the wafer 1.

  For example, an ultrasonic transducer (not shown) is attached in the vicinity of the circular end surface of the vibrating body 2 on the side not facing the wafer 1, and the ultrasonic wave oscillated by the ultrasonic transducer passes through the vibrating body 2. Then, the ultrasonic wave is transmitted from the ultrasonic radiation surface, which is the circular end surface portion of the vibrating body 2 facing the wafer 1, to the cleaning liquid 7 in the gap 4, and the surface of the wafer 1 is irradiated with ultrasonic waves. The foreign matter adhering to the surface of the wafer 1 is detached from the surface by the action of this ultrasonic irradiation and flows out into the cleaning liquid 7 flowing in the vicinity. The foreign matter usually flows out so as to float in the cleaning liquid 7 because of its light weight.

  As described above, the separation (removal) of the foreign matter is an action between the surface area of the wafer 1 to which the ultrasonic waves are effectively irradiated, that is, between the ultrasonic radiation surface of the vibrating body 2 and the surface area of the wafer 1 that is almost directly opposed thereto. Done.

  The direction indicated by the arrows in the gap 4, the passage 5, and the gap 6 in FIG. For example, a cleaning liquid that is cleaned toward the surface of the wafer 1 by using a gap 6 formed by an outer side surface of the columnar vibrator 2 and an inner side surface of the cylindrical envelope 3 by a pressure pump (not shown) or the like. 7 is fed continuously. The entire flow of the cleaning liquid 7 flowing through the gap 6 has a cylindrical shape due to the shape of the gap 5, and the flow rate of the cleaning liquid 7 reaching the surface of the wafer 1 in a ring shape is uniform everywhere.

  On the other hand, the passage 5 provided so as to pass through the center of the cylinder of the vibrating body 2 is connected to a suction pump (not shown) or the like in the upper part of the figure, and in the passage 5 is opposite to the cleaning liquid 7 flowing through the gap 6. The cleaning liquid 7 is sucked up in a direction away from the surface of the wafer 2.

  By the way, in the figure, the clean cleaning liquid 7 which has gone to the surface of the wafer 1 (direction A) using the gap 6 as a passage (direction A) reaches the surface of the wafer 1 around the vibrating body 2 in a ring shape, and then passes through the gap 4. The flow is divided into a flow toward the center direction (direction B) of the outer envelope 3 and a flow toward the outer peripheral direction (direction C). The flow of the cleaning liquid toward the central direction (direction B) flows through the gap 4 between the ultrasonic radiation surface of the vibrating body 2 and the surface of the wafer 1 so as to be sucked up from the passage 5 (direction D). Effluent from the washing system at the end. As described above, the flow in the direction B in the gap 4 is a flow in which a large amount of foreign matter detached from the surface of the wafer 1 floats in the cleaning liquid, and this is continuously sucked through the passage 5 in the vibrator 2. (Direction D) is discharged from the upper part of the vibrator 2 to the outside of the cleaning system.

  By constructing such a flow of the cleaning liquid, the cleaning liquid 7 in the flow directions B and D containing a high concentration of foreign matters does not spread over the region of the wafer 1 where the ultrasonic waves are not irradiated, and is irradiated with ultrasonic waves. Foreign matter including the wafer area does not adhere again. On the other hand, the cleaning liquid 7 that is separated from the gap 6 and flows out to the outer periphery of the cylinder in the direction C substantially does not participate in the ultrasonic cleaning, and remains in a clean state from the ring-shaped cleaning liquid outlet and passes through the gap 4. It spreads over the entire surface of the wafer 1 and contributes to keeping the entire surface of the wafer 1 wet.

  FIG. 2 is a schematic diagram of an embodiment that embodies the basic configuration of the vibrating body portion and the envelope portion. 2A is a cross-sectional view taken along the central axis of the vibrating body 2 and the outer enclosure 3, and FIGS. 2B and 2C are a top view and a bottom view, respectively.

  Referring to each drawing of FIG. 2, the vibrating body 2 has a cylindrical shape, and the material thereof is, for example, synthetic quartz glass. The material of the vibrating body is not necessarily limited to this, and may be, for example, stainless steel (SUS) as long as it is a stable material that propagates ultrasonic waves without attenuation and that does not elute even when contacted with the cleaning liquid to be used. -Materials such as sapphire, ceramic, SiC, and alumina can be arbitrarily selected. A passage 5 which is a hole penetrating the vibrating body 2 is provided along the central axis of the columnar vibrating body 2.

  A cylindrical outer body 3 is provided outside the vibrating body 2 so as to surround the periphery of the vibrating body 2. The material of the envelope 3 is, for example, a fluororesin. However, the material is not limited to this. For example, stainless steel (SUS) may be used as long as it is a stable material that does not elute even when it comes into contact with the cleaning liquid to be used. The material can be applied freely. A uniform gap (gap 6) is provided between the outer peripheral side surface of the vibrating body 2 and the inner side surface of the outer enclosure 3.

  The vibrating body 2 and the envelope 3 each form a common flat end face HH ′ on the end face side facing the wafer, and are placed so as to face each other in parallel with a certain minute distance from the wafer surface. . The upper end portion of the outer enclosure 3 is connected to the outer peripheral side surface of the vibrating body 2 so as to close the gap 6.

  An ultrasonic vibrator 8 is installed on the end of the cylindrical vibrator 2 that does not face the wafer. For example, an RF power source is connected to the ultrasonic vibrator 8 via a power line (not shown), and by controlling this, the oscillation and intensity of the ultrasonic vibration are controlled. The ultrasonic vibrator 7 is made of a material similar to that of the vibrator 2 such as flat plate quartz, stainless steel (SUS), sapphire, ceramic, SiC, and alumina.

  A plurality of supply pipes 9 are connected from the outside of the outer enclosure 3 so as to penetrate the outer enclosure 3 in the vicinity of the upper end of the gap 6. In the present embodiment, a total of eight supply pipes 9 are connected around the outer envelope 3 at equal intervals. A supply pump (not shown) is connected to each supply pipe 9, and the cleaning liquid is sent out at a flow rate equal to all of the supply pipes 9 by operating this supply pump, so that the cleaning liquid flows downward (from the wafer surface direction) to above the gap 6. ) Toward the wafer surface in a uniform cylindrical flow. The number and arrangement of the supply pipes 9 are not limited to the above example, and the flow of the cylindrical cleaning liquid in the gap 6 serving as the cleaning liquid supply passage is configured to be as uniform and stable as possible. Is desirable.

  On the other hand, a suction pipe 10 is connected to the passage 5 of the vibrating body 2. A suction pump (not shown) is connected to the suction pipe 10, and the suction pump can be operated to suck up the cleaning liquid through the passage 5.

  Due to the flow path configuration of the cleaning liquid as described above, the flow rate of the cleaning liquid fed from the supply pipe 9 into the gap 6, the flow volume of the cleaning liquid sucked up from the passage 5 by the suction pipe 10, and the relationship between the gap between the common plane end face and the wafer surface. By adjusting, as described above with reference to FIG. 1, the cleaning liquid 7 in the direction A supplied to the surface of the wafer 1 in a ring shape (see FIG. 1) is applied between the vibrating body 2 and the wafer 1. The flow of the cleaning liquid flowing in the direction B toward the center direction through the gap 4 having the width S and flowing in the direction D in which the gap is sucked through the passage 5, and the gap 4 having the width S between the vibrating body 2 and the wafer 1. Can be divided into a flow in the direction C and spreading toward the outer edge.

  When the ultrasonic vibrator 8 is operated under such circumstances, the cleaning liquid in which the foreign matter separated from the surface of the wafer 1 is separated by the action of ultrasonic waves applied to the surface of the wafer 2 from the end face of the vibrator 2 is obtained. Floating in the flow in the direction B, and almost all foreign matter is discharged from the suction tube 10 by the flow in the direction D in the passage 5 and is removed from the vicinity of the surface of the wafer 1. At the same time, the surface region of the wafer 1 that is not irradiated with ultrasonic waves is in a state where a clean cleaning liquid in which foreign matter is not floating always flows due to the flow of the cleaning solution 7 in the direction C. It is possible to eliminate adhesion to the region.

  FIG. 3 is a schematic diagram for explaining a state in which the integral configuration of the vibrating body 2 and the outer enclosure 3 is attached to the ultrasonic cleaning apparatus in relation to the wafer to be cleaned. In FIG. 3, a cleaning arm 12 extends in the horizontal direction from the tip of the arm support shaft 11 standing in the vertical direction in the cleaning device. A clamp 13 is provided at the distal end of the cleaning arm 12, and the integral configuration of the vibrating body 2 and the outer enclosure 3 is fixed by tightening the outer peripheral side surface of the outer enclosure 3 at the distal end. By this tightening method, the influence of the clamp 13 does not affect the vibration of the vibrating body 2. With the outer envelope 3 held in this manner, the common plane end surface of the vibrating body 2 and the outer envelope 3 is made parallel to the wafer 1, and the clamp 13 or the connecting portion between the cleaning arm 12 and the clamp 13 is arranged. It is desirable to provide a fine adjustment mechanism for realizing this.

  The arm support shaft 11 can perform vertical movement and rotational movement in the vertical direction on the spot. The wafer 1 is placed on a wafer support table 15 on a rotatable wafer rotation support shaft 14.

  The wafer cleaning operation can be generally performed by the following procedure. First, the ultrasonic vibration generation related component composed of the ultrasonic vibrator, the vibration body, the outer body, the cleaning liquid supply / discharge system, etc. fixed to the clamp 12 is retracted to a position away from the wafer support table 15. deep. After the wafer 1 that is the object to be cleaned is placed on the wafer support table 15, the ultrasonic vibration generation related components are moved onto the wafer 1 using the vertical and rotational motion functions of the arm support shaft 11. The parallel gap between the common plane end surface of the vibrating body 2 and the outer envelope 3 and the surface of the wafer 1 is set to a predetermined distance. Here, ultrasonic cleaning is performed by generating ultrasonic waves along with supply / discharge of the cleaning liquid. At this time, since it is necessary to perform cleaning on the entire wafer surface, the arm support shaft 11 performs a reciprocating rotational motion at a predetermined speed around the support shaft, so that the ultrasonic vibration generation related components are on the surface of the wafer 1. Are swung in a circular arc shape, and the wafer rotation support shaft 14 is rotated about the center of the wafer 1 as a rotation center. By the movement of both, the entire surface of the wafer 1 is swept by ultrasonic vibration. When the sweep of the ultrasonic cleaning is completed, the arm support shaft 11 is operated again to retract the ultrasonic vibration generation related component to another position, and the wafer 1 is removed from the wafer support table 15. The wafer cleaning operation in such a procedure is performed by automatic control by a control device (not shown) provided in the cleaning device according to a predetermined recipe.

  In the ultrasonic cleaning apparatus of the present embodiment, the vibration frequency of the ultrasonic ground vibrator 8 is 3 MHz, but is not limited thereto and can be selected as appropriate. However, considering the influence of damage on the wafer surface by the ultrasonic wave, the vibration frequency is preferably 1 MHz or more, and more preferably 3 MHz or more.

  Further, although the distance S (see FIG. 1) of the gap 4 between the wafer-side end surface of the vibrating body 2 (= the wafer-side end surface of the envelope 3) and the surface of the wafer 1 is 1 mm, an ultrasonic wave having a relatively small vibration amplitude. From the viewpoint of irradiating the surface of the wafer 1 with as much attenuation as possible, the gap distance S is preferably about 3 mm or less, and more preferably 1 mm or less.

  The circular diameter of the columnar vibrator 2 is 20 mm, but this diameter reduces the flowing water resistance in the gap between the vibrator 2 and the wafer 1 and contains a high concentration of foreign matter from the passage 5 as a suction passage. From the viewpoint of smoothly sucking up the cleaning liquid (also flowing in the direction D; see FIG. 1), it is desirable that the cleaning liquid is about 30 mm or less.

  Further, the flow rate of the cleaning liquid was 2 L / min, and the rotation of the wafer rotation support shaft 14 was performed at 100 rpm.

  The ultrasonic cleaning apparatus according to the present invention having various dimensions as described above, and a simple cylindrical vibrator that does not have a suction path formed at the center, and a structure that simply allows the cleaning liquid to flow into the gap with the wafer In other words, a performance comparison experiment was performed with a conventional ultrasonic cleaning apparatus. In both apparatuses, the diameter of the circular surface of the vibrating body (equivalent to the ultrasonic irradiation area) is 20 mm, the vibration frequency, the input power, the distance between the vibrating body and the wafer, the flow rate of the cleaning liquid, the vibrating body sweeping method, etc. Other conditions were the same. As the cleaning liquid, hydrogen-dissolved water in which hydrogen gas was dissolved in pure water at a concentration of 1.5 mg / L was used.

As a sample to be cleaned, a thermal oxide film having a thickness of 100 μm is formed on an Si wafer having a diameter of 8 inches, and silica (SiO ₂ ) particles having an average particle size of 0.15 μm are adhered to the surface almost uniformly. Was used. The total number of adhered silica particles was adjusted to be approximately 30,000 per wafer. This evaluation sample was cleaned with the apparatus of the present invention and the comparison apparatus, and the number of silica particles adhering to the wafer surface before and after cleaning was measured using a wafer surface inspection apparatus.

  When the time required to remove 95% of the fine particle silica adhering to the wafer surface of the evaluation sample was measured, an average of 180 seconds or more was required for the conventional ultrasonic cleaning device using the vibrator shape in this case. On the other hand, the ultrasonic cleaning apparatus according to the example of the present invention was able to be performed in an average of about 60 seconds. This result is considered to clearly show the effectiveness of the apparatus of the present invention in which the foreign matter (particulate silica) detached from the sample to be cleaned avoids reattachment to the wafer surface during cleaning. .

(Second embodiment)
FIG. 4 shows the basics of the vibrator 2 and its surrounding material 3 for propagating ultrasonic vibrations through the cleaning liquid in contact with the surface of the wafer 1 and the flow path of the cleaning liquid according to the second embodiment of the present invention. The cross-sectional schematic diagram for demonstrating a typical structure is shown. The difference between the present embodiment and the first embodiment (see FIG. 1) is that the gap between the lower circular surface of the columnar vibrator 2 having the passage 5 and the wafer 2, that is, the gap of the vibrator gap 4-1. The distance S1 is different from the gap between the lower surface of the outer enclosure 3 and the wafer 2, that is, the gap distance S2 of the outer enclosure gap 4-2, and S2 is smaller than S1. In other words, by doing this, among the flows in the direction A from the gap 6 which is the supply path of the cleaning liquid, the flow rate of the cleaning liquid flowing out in the direction C from the lower surface of the outer enclosure is reduced, and a larger part is obtained. The flow is in the direction B, and the flow is in the direction D through the passage 5 that is the absorption path. As a result, it becomes more difficult for the cleaning liquid containing floating foreign substances generated immediately below the vibrating body 2 to flow out in the direction C, and the suction flow rate from the passage 5 is increased to facilitate the suction. You can expect the effect.

(Third embodiment)
FIG. 5 is a schematic bottom view of the structural body of the vibrating body 2 and the outer enclosure 3 according to the third embodiment of the present invention. The difference from the first embodiment (refer to FIG. 2) is that a plurality of radially extending from the opening of the passage 5 that passes through the center of the cylinder as an absorption path, at a position facing the wafer on the lower circular surface of the vibrator 2 ( In this example, eight grooves), that is, the vibrator groove 16 is provided. By doing so, as in the second embodiment, the flow rate of the cleaning liquid in the direction B immediately below the vibrating body 2 containing a large amount of foreign matter is increased as the flow in the direction D through the passage 5. Therefore, it is possible to facilitate the flow out to the outside. The cleaning liquid in which foreign matter floats (the cleaning liquid in the direction B in FIG. 1) stays and does not reattach to the wafer surface, and can be expected to effectively work for shortening the cleaning time. Of course, the second embodiment and the third embodiment may be used in combination.

  As described above, by applying the cleaning apparatus according to the present invention, foreign matter such as fine particles adhering to the surface can be efficiently removed even in the case of a wafer having a fine pattern that is fragile on the surface. The cleaning time can be greatly shortened compared to the previous equipment.

The figure explaining the fundamental composition of the vibrating body concerning the 1st example of the present invention, an enclosure, and the channel of cleaning fluid. The figure explaining the specific structure of the vibrating body, the outer enclosure, and the flow path of the cleaning liquid according to the first embodiment of the present invention. The figure explaining the structure of the arm part of the washing | cleaning apparatus of this invention The figure explaining the basic composition of the vibrating body concerning the 2nd example of the present invention, an enclosure, and the channel of cleaning fluid. The figure explaining the specific structure of the vibrating body, enclosure, and flow path of the cleaning liquid according to the third embodiment of the present invention. The figure explaining the conventional nozzle type ultrasonic cleaning device The figure explaining the conventional vibratory body type ultrasonic cleaning device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wafer 2 Vibrating body 3 Outer body 4 Gap 5 Passage 6 Gap 7 Cleaning liquid 8 Ultrasonic vibrator 9 Supply pipe 10 Suction pipe 11 Arm support shaft 12 Cleaning arm 13 Clamp 14 Wafer rotation support shaft 15 Wafer support table 16 Vibration body groove DESCRIPTION OF SYMBOLS 101 Ultrasonic nozzle 102 Wafer 103 Cleaning liquid 104 Ultrasonic irradiation area 105 Vibrating body 106 Ultrasonic vibrator 107 Vibrating body support means 108 Cleaning liquid nozzle

Claims (4)

A columnar vibrator arranged on the object to be cleaned;
The cleaning liquid discharged on the object to be cleaned has a cylindrical shape surrounding a side surface of the vibrating body, and a first flow that flows in a direction of a central axis of the vibrating body, and a direction opposite to the first flow A flow path through which the cleaning liquid passes so as to be diverted into a flowing second flow;
A passage formed in a region including the central axis of the vibrating body in the vibrating body and collecting the cleaning liquid forming the first flow ;
A cleaning apparatus comprising: A support for supporting the object to be cleaned;
The cleaning apparatus according to claim 1, further comprising a moving unit that positions the flow path and the object to be cleaned so as to face each other with a first interval.   The cleaning apparatus according to claim 1, wherein the passage and the object to be cleaned are opposed to each other with a second interval larger than the first interval.   4. The cleaning apparatus according to claim 1, wherein the passage is connected to suction means.

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