JP4806296B2 - Cleaning device - Google Patents

Description

  The present invention relates to a cleaning device, and more particularly to, for example, a cleaning device that removes an oxide film formed on the surface of a solder material or a member to be soldered.

  Conventionally, for example, this type of cleaning device is disclosed in Patent Document 1. This prior art includes a vacuum chamber having an open end. And the opening end of this vacuum chamber is contact | abutted by the board | substrate which is a to-be-processed object through a sealing material. As a result, the inside of the vacuum chamber is sealed. Further, after the pressure in the vacuum chamber is reduced, a hydrogen plasma atmosphere is created. Then, the hydrogen plasma reacts with the oxide film formed on the surface of the solder bump on the substrate, whereby the oxide film is reduced and removed. According to this prior art, since it is not necessary to accommodate the entire substrate in the vacuum chamber, the vacuum chamber can be made extremely small.

Japanese Patent Laid-Open No. 2004-207577

  Thus, removing the oxide film with hydrogen plasma has been conventionally performed. Further, it is known that the oxide film can be removed not only by hydrogen plasma but also by hydrogen gas, for example. However, in the case of removal by hydrogen plasma, the charged particles contained in the hydrogen plasma collide with the surface of the object to be processed, so that the surface of the object to be processed is damaged. And this damage becomes so large that processing time is long. On the other hand, in the case of removal with hydrogen gas, it is necessary to heat the object to be processed to a high temperature of about 400 [° C.] in order to increase the reducing power by the hydrogen gas, and accordingly, there is a considerable thermal It takes stress. This thermal stress also increases as the processing time increases.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a cleaning device that can remove an oxide film more efficiently than before in order to reduce damage and thermal stress applied to an object to be processed.

  In order to achieve such an object, a cleaning device of the present invention includes a vacuum chamber in which the inside is evacuated, a support unit that is provided in the vacuum chamber and supports a workpiece, and a heating unit that heats the workpiece. And a reducing gas supply means for supplying a reducing gas for reducing the oxide film formed on the surface of the workpiece into the vacuum chamber, and a vibration applying means for applying vibration to the support means. Is.

  That is, in this invention, the support means is provided in the vacuum chamber, and the workpiece is supported by this support means. Then, after the inside of the vacuum chamber is evacuated, the object to be processed is heated by the heating unit, and the reducing gas is further supplied into the vacuum chamber by the reducing gas supply unit. Then, the reducing gas and the oxide film formed on the surface of the object to be processed react with each other, whereby the oxide film is reduced and removed. At this time, vibration is applied to the support means by the vibration applying means. And this vibration is transmitted to a to-be-processed object via a support means. As a result, the object to be processed vibrates with the supporting means, and the reaction between the oxide film formed on the surface of the object to be processed and the reducing gas is activated. In addition, when the object to be processed vibrates in this way, the reducing gas easily reaches every corner of the object to be processed.

  Note that hydrogen gas is suitable as the reducing gas in the present invention.

  Further, in the present invention, discharge means for discharging the reducing gas is further provided, and particles, that is, ions, electrons, and free radicals (hereinafter referred to as radicals) generated when the reducing gas is discharged. The oxide film may be reduced by a plasma containing. Thus, by reducing the reducing gas into plasma, the reduction action of the oxide film by the reducing gas is further activated.

  Further, in this case, an extraction means for extracting only radicals that are neutral particles having no charge from ions, electrons, and radicals contained in the plasma is provided, and the oxide film is reduced only by the radicals. Also good. That is, ions and electrons that are charged particles may be excluded. If it does in this way, the damage to the said to-be-processed object by these ions and electrons colliding with the surface of a to-be-processed object will be suppressed.

  And as a to-be-processed object in this invention, there exist a solder material and a to-be-soldered member, for example. In particular, as a solder material, there is a so-called solder ball, which is a spherical solder material used as a material for a solder bump.

  Further, a fall prevention means for preventing the workpiece from falling from the support means may be provided. In particular, when the object to be processed has a shape that easily rolls (moves easily) like the above-described solder ball, it is desirable to provide such a fall prevention means.

  Moreover, it is desirable that the heating means in the present invention can arbitrarily change the heating temperature of the object to be processed. The variable range of the heating temperature is, for example, normal temperature or higher and lower than the melting point of the object to be processed. As such a heating means, for example, a resistance heater is suitable.

  And it is desirable that the vibration applying means in the present invention can arbitrarily change the vibration frequency. Note that the variable range of the vibration frequency is, for example, about several tens [Hz] to several tens [kHz].

  Furthermore, it is desirable that the vibration applying means can arbitrarily change the amplitude of vibration. As such vibration applying means, for example, a high-frequency vibration device such as an ultrasonic vibrator can be employed.

  As described above, according to the present invention, the object to be processed is vibrated, so that the reaction between the oxide film formed on the object to be processed and the reducing gas for reducing the oxide film is activated. Is done. Further, when the object to be processed vibrates, the reducing gas easily reaches every corner of the object to be processed. For this reason, it is possible to remove the oxide film more efficiently than before, and accordingly, damage and thermal stress applied to the object to be processed during the removal process of the oxide film can be reduced.

  An embodiment of the present invention will be described with reference to FIGS. 1 and 2.

  As shown in FIG. 1, the cleaning device 10 according to this embodiment includes a box-shaped metal chamber 12 as a vacuum chamber. In the inside of the chamber 12, that is, in a vacuum chamber, a substantially flat support base 14 as a support means is arranged with its upper surface in the horizontal direction. Further, a wall 16 as a fall prevention means is provided on the upper surface of the support base 14 along its peripheral edge. A large number of solder balls 18, 18,... As processing objects are accommodated in a concave space surrounded by the inside of the wall 16 and the upper surface of the support base 14. The wall 16 extends straight upward from the upper surface of the support base 14, and its height dimension is larger than the overall height dimension (loading height) of the workpieces 18, 18,. It is said that.

  The support base 14 incorporates a resistance heater 20 as a heating means. The resistance heater 20 generates heat when a heater heating power is supplied from a heater heating power source (not shown) provided outside the chamber 12, and the object to be processed on the support base 14 is generated by the generated heat energy. 18, 18, ... are heated. The heating temperature of the workpieces 18, 18,... By the resistance heater 20 is in the range of the normal temperature or higher and less than the melting point of the workpieces 18, 18,. The temperature can be arbitrarily controlled within the range of [° C.] to about 180 [° C.].

  Further, although not shown in the drawing, the support base 14 is provided with a water-cooling type cooling device as a cooling means in addition to the resistance heater 20. This cooling device is in a non-contact state with respect to the support base 14 when the above-described heater heating power is supplied to the resistance heater 20, that is, when energized. When the energization of the resistance heater 20 is cut off and the workpieces 18, 18,... Need to be cooled, the cooling device comes into contact with the entire lower surface of the support base 12 and together with the support base 12. The workpieces 18, 18,... Are cooled. As described above, the resistance heater 20 as the heating means and the cooling device as the cooling means are provided side by side, thereby enabling more accurate and quick temperature control of the workpieces 18, 18,.

  Further, one end (upper end) of the connecting rod 22 as a vibration transmitting means is coupled to a substantially central portion of the lower surface of the support base 14. The other end (lower end) of the connecting rod 22 passes through a substantially central portion of the bottom wall of the chamber 12 and is coupled to an ultrasonic vibrator 24 as a vibration applying means provided outside the chamber 12. Has been.

  The ultrasonic transducer 24 applies vibrations along the vertical direction to the connecting rod 22 when the transducer driving power is supplied from a transducer power source (not shown). The vibration applied to the connecting rod 22 is transmitted to the support base 14 via the connecting rod 22. As a result, the support base 14 vibrates along the vertical direction as indicated by an arrow 26. In addition, as the support base 14 vibrates in this way, the objects 18 to be processed 18 on the support base 14 also vibrate together.

  Note that the vibration frequency of the ultrasonic vibrator 24 is, for example, in the range of several tens [Hz] to several tens [kHz], preferably 100 [Hz] to 10 [kHz], by adjusting the vibrator driving power described above. Can be arbitrarily controlled within the range, more preferably within the range of 1 [kHz] to 5 [kHz]. The vibration width (stroke) of the support base 14 by the ultrasonic vibrator 24 can be arbitrarily controlled by adjusting the vibrator driving power. Further, a bellows 28 is provided between the connecting rod 22 and the bottom wall of the chamber 12 (joining portion) as a buffering means for alleviating an impact caused by the vibration of the connecting rod 22.

  Further, an exhaust port 30 is provided at an appropriate position of the wall portion of the chamber 12, for example, a position slightly outside the center of the bottom wall. A vacuum pump 34 as an exhaust means provided outside the chamber 12 is coupled to the exhaust port 30 via an exhaust pipe 32. For example, a combination of a mechanical booster pump and a rotary pump is employed as the vacuum pump 34.

  Further, a shielding plate 36 as an extraction means is provided at a position above the support base 14 in the chamber 12. This shielding plate 36 is a so-called wire mesh, and is provided along the horizontal direction so as to divide the inside of the chamber 12 into two vertically. A space 38 above the shielding plate 36 in the chamber 12 is a plasma light emitting chamber, and a space 40 below is a processing chamber. In general, the plasma emission chamber 38 is formed smaller than the processing chamber 40, but the present invention is not limited to this. Although not shown in the drawing, the shielding plate 36 is connected to the ground potential as the reference potential together with the wall portion of the chamber 12.

Further, in order to introduce hydrogen (H ₂ ) gas as a reducing gas into the plasma emission chamber 38, a gas introduction pipe 42 is provided at an appropriate position on the side wall of the chamber 12 constituting the wall portion of the plasma emission chamber 38. Are combined. The gas introduction pipe 42 is coupled to a hydrogen gas source 44 constituting a reducing gas supply means together with the gas introduction pipe 42 outside the chamber 12. Although not shown in the drawing, the hydrogen gas source 44 includes a flow rate control device for controlling the supply amount (flow rate) of hydrogen gas into the plasma light emitting chamber 38.

  Furthermore, a quartz microwave introduction window 46 is provided in a specific portion of the upper wall of the chamber 12 constituting the wall of the plasma emission chamber 38, specifically, a portion facing the upper surface of the support base 14. . Above the microwave introduction window 46, a waveguide 48 having the microwave introduction window 46 as an output end is provided so as to extend along the horizontal direction. A micro generator 50 that constitutes a discharge means together with the waveguide 48 and the microwave introduction window 46 is coupled to the input end.

  According to the cleaning apparatus 10 configured as described above, the oxide film MO (M; metal = element of the objects to be processed 18, 18,..., O; oxygen, which is formed on the surface of the objects to be processed 18, 18,. ) Can be removed as follows.

  That is, with the workpieces 18, 18,... Installed on the support base 14 as described above, first, the inside of the chamber 12 is in a high vacuum state of about 1 [Pa] to 2 [Pa] by the vacuum pump 34. Exhausted.

  Subsequently, the microwave generator 50 is activated. Then, the microwave generator 50 generates a microwave having a frequency of 2.45 [GHz]. As indicated by an arrow 52, the microwave propagates toward the microwave introduction window 46 through the waveguide 48 and further propagates along the upper surface (surface) of the microwave introduction window 46. While passing through the microwave introduction window 46, it is introduced into the plasma emission chamber 38.

  At the same time, hydrogen gas is introduced into the plasma emission chamber 38 from the hydrogen gas source 44 through the gas introduction pipe 42 as indicated by an arrow 54. The hydrogen gas particles introduced into the plasma emission chamber 38 receive and discharge the energy of the microwave introduced into the plasma emission chamber 38 through the microwave introduction window 46 as described above. As a result, hydrogen plasma is generated in the plasma emission chamber 38.

The hydrogen plasma generated in the plasma light emitting chamber 38 includes hydrogen ions H ⁺ , electrons e ⁻ and hydrogen radicals H ^*. Among these, hydrogen ions H ⁺ and electrons e ⁻ which are charged particles pass through the shielding plate 36. Flows to the ground potential through, so to speak, is eliminated. Only the hydrogen radicals H ^* which are neutral particles having no electric charge pass through the shielding plate 36 and are guided from the plasma emission chamber 38 into the processing chamber 40. Note that the pressure in the chamber 12 including the plasma emission chamber 38 and the processing chamber 40 at this time is adjusted to, for example, about 10 [Pa] to 150 [Pa].

In the processing chamber 40, the resistance heater 20 causes the processing objects 18, 18,... On the support table 14 to have an appropriate temperature, for example, 180 [° C. slightly lower than the melting point of the processing objects 18, 18,. It is heated to about a temperature. Then, the oxide film MO formed on the surface of the workpieces 18, 18,... Reacts with the hydrogen radicals H ^* introduced into the processing chamber 40 through the shielding plate 36 as described above. Accordingly, the oxide film MO is reduced and removed. The reaction between the oxide film MO and the hydrogen radical H ^* is expressed by the following formula 1.

<< Formula 1 >>
MO + H ^* → M + H ₂ O

Further, at this time, vibration is applied to the workpieces 18, 18,... Via the connecting rod 22 and the support base 14 by the ultrasonic vibrator 24. Then, the reaction between the oxide film MO formed on the surface of the workpieces 18, 18,... And the above-described hydrogen radical H ^* is activated. Further, the hydrogen radicals H ^* are likely to reach all corners of the workpieces 18, 18,. As a result, the action of removing the oxide film MO by the hydrogen radical H ^* becomes more efficient.

  After the oxide film MO is sufficiently removed, the operations of the microwave generator 50, the hydrogen gas source 44, the resistance heater 20, and the ultrasonic vibrator 24 are stopped, and the vacuum pump 34 The pressure is gradually returned to atmospheric pressure. In addition, after the temperature of the workpieces 18, 18,... Is returned to room temperature by the cooling device described above, the workpieces 18, 18,... Are taken out from the chamber 12 after a certain stabilization period. It is. This completes a series of cleaning processes.

As described above, according to the cleaning apparatus 10 of this embodiment, the vibrations are applied to the workpieces 18, 18,... So that the oxide films formed on the surfaces of the workpieces 18, 18,. The reaction between MO and hydrogen radical H ^* is activated. In addition, the hydrogen radicals H ^* can easily reach every corner of the surface of the workpieces 18, 18. Therefore, the oxide film MO can be removed more efficiently than before, and damage and thermal stress applied to the workpieces 18, 18,... During the cleaning process of the oxide film MO are reduced.

In this embodiment, the oxide film MO is reduced only by the hydrogen radicals H ^* that are neutral particles, and the hydrogen ions H ⁺ and electrons e ⁻ that are charged particles are excluded. Therefore, they are charged particles hydrogen ions H ⁺ and electrons e ^- is the processing object 18, the object to be treated by impinging on ... the surface of 18, 18, ... is damage to be prevented.

  In this embodiment, the support base 14 including the workpieces 18, 18,... Is vibrated along the vertical direction, but the present invention is not limited to this. For example, the support base 14 may be vibrated along the horizontal direction, or, as indicated by arrows 100 and 100 in FIG.

Furthermore, a change (impact) may be given to the reduction reaction of the oxide film MO by the hydrogen radicals H ^* by changing the vibration direction, vibration frequency, vibration width, etc. of the support table 14 during one cleaning process. In addition, in order to make the cleaning process uniform for the workpieces 18, 18,..., For example, the support base 14 may be rotated about the connecting rod 22 as an axis.

  The ultrasonic transducer 24 is provided outside the chamber 12, but may be provided inside the chamber 12, or in the extreme, may be built in the support base 14. Further, a high-frequency vibration device other than the ultrasonic transducer 24 (particularly, a device including a piezoelectric element) may be employed as the vibration applying unit.

  Furthermore, the above-described wall 16 is provided as the fall prevention means in order to prevent the workpieces 18, 18,... From dropping from the support base 14. However, the present invention is not limited to this. For example, the fall prevention means may be configured by providing a concave depression on the upper surface of the support base 14 or fixing a concave container on the upper surface of the support base 14.

  The resistance heater 20 is used as the heating means, but another means such as a heat radiation lamp may be used instead. In addition, the cooling device described above may be omitted if it is not necessary.

  Furthermore, in this embodiment, the hydrogen gas as the reducing gas is converted into plasma by the microwave, but the present invention is not limited to this. For example, the hydrogen gas may be turned into plasma with a high frequency of 13.56 [MHz].

  Furthermore, although solder balls have been exemplified as the workpieces 18, 18,..., They are not limited thereto. For example, solder materials other than solder balls can also be applied as the workpieces 18, 18,. Further, members other than solder materials, for example, members to be soldered such as electrode parts and other metal members can also be applied as the objects to be processed 18, 18. However, it is important to appropriately adjust the heating temperature by the heating means or the vibration frequency and amplitude by the vibration applying means in accordance with the shape, size, type, characteristics, and the like of the workpieces 18, 18.

  Moreover, although hydrogen gas was employ | adopted as reducing gas, it is not restricted to this. For example, a mixed gas of hydrogen gas and an inert gas such as argon (Ar) gas or a mixed gas of the hydrogen gas and nitrogen gas may be employed. Further, an organic acid gas such as formic acid may be employed. Further, a carbon-based gas such as carbon monoxide (CO) may be employed. However, in this case, care must be taken not to generate unnecessary compounds that affect the cleaning process.

  Further, the reducing gas need not be converted to plasma. However, in this case, it is necessary to heat the objects 18, 18,... To a higher temperature in order to improve the reducing power by the reducing gas.

  As described above, the content described in this embodiment is an example for realizing the present invention until it is tired, and does not limit the present invention.

It is a figure which shows schematic structure of one Embodiment of this invention. It is a figure which shows another example of the same embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Cleaning apparatus 12 Chamber 14 Support stand 18 To-be-processed object 20 Resistance heating heater 24 Ultrasonic vibrator 34 Vacuum pump 44 Hydrogen gas source

Claims (8)

A vacuum chamber where the interior is evacuated,
A support means for supporting an object to be processed provided in the vacuum chamber;
Heating means for heating the workpiece;
A reducing gas supply means for supplying a reducing gas for reducing an oxide film formed on the surface of the object to be processed into the vacuum chamber;
Vibration applying means for applying vibration to the support means;
Equipped with,
The object to be processed is a solder material or a member to be soldered,
Cleaning device. A vacuum chamber where the interior is evacuated,
A support means for supporting an object to be processed provided in the vacuum chamber;
Heating means for heating the workpiece;
A reducing gas supply means for supplying a reducing gas for reducing an oxide film formed on the surface of the object to be processed into the vacuum chamber;
Vibration applying means for applying vibration to the support means;
Fall prevention means for preventing the workpiece from falling from the support means;
A cleaning device comprising: The reducing gas is hydrogen gas, a cleaning device according to claim 1 or 2. It further comprises discharge means for discharging the reducing gas,
The oxide film is reduced by particles generated by discharging the reducing gas.
The cleaning device according to claim 1. It further comprises an extraction means for extracting free radicals from the particles,
The oxide film is reduced by the free radicals extracted by the extraction means.
The cleaning device according to claim 4 . The heating means can be arbitrarily changed the heating temperature of the object to be processed, the cleaning apparatus according to any one of claims 1 to 5. Is the vibrating means can be arbitrarily changing the frequency of the vibration, the cleaning apparatus according to any one of claims 1 to 6. Is the vibrating means can be arbitrarily changed the amplitude of the vibration, the cleaning apparatus according to any one of claims 1 to 7.

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