JP2008239448A - Method and apparatus for producing crystalline particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing crystalline particles by which the crystalline particles can be highly efficiently produced in the form of fine particles having a stable and uniform shape and particle size. <P>SOLUTION: The method for producing the crystalline particles includes the steps of: (1) preparing a melt 4 of a crystal material by melting the crystal material in a crucible 1 where a nozzle part 3 having a nozzle hole 6 penetrating in an inclined direction with respect to the vertical direction is provided in the bottom part; (2) discharging the melt 4 from the nozzle hole 6 to make the melt 4 into a granular form; and (3) cooling the granulated melt 4a during falling to solidify the melt 4a. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method and apparatus for producing granular crystals suitable for producing crystal particles used in a photoelectric conversion device.

  In recent years, since sufficient photoelectric conversion is possible with a small amount of crystal, photoelectric conversion devices using crystal particles as photoelectric conversion elements instead of large crystal ingots have been developed. Crystals used in photoelectric conversion devices A method for producing particles is also being actively developed.

For example, Patent Document 1 discloses a crystalline metal particle having high crystallinity used as a photoelectric conversion element of a silicon solar battery, and a granular metal crystal for stably and efficiently producing other metal particles at low cost. As a manufacturing method, the metal melt is discharged and dropped from a nozzle hole attached to the lower part of a crucible for melting metal, and the drop is cooled and solidified while being dropped. There exists a manufacturing method of a granular metal crystal which manufactures a granular metal crystal by this (for example, refer to patent documents 1). In this method for producing a granular metal crystal, the crucible is composed of a cylindrical main body part and a disk-like nozzle part attached to the bottom part of the main body part, and the metal melt provided in the nozzle part is discharged in droplets. As the nozzle hole to be used, a nozzle portion that is horizontally attached to the bottom portion of the main body portion and penetrated perpendicularly to the surface was used.
JP 2003-128493 A

  However, in the method for producing crystal particles in Patent Document 1, since the discharged metal crucibles are different in size and dropping speed, even when discharged at different timings, before the metal melts solidify. The particle size of the obtained granular metal crystals was distributed, and the yield was reduced.

  The present invention has been devised in view of the problems in the prior art as described above, and an object thereof is to produce crystal particles with a stable and uniform shape and particle size with high efficiency. The object is to provide a method for producing crystal grains.

  The method for producing crystal grains according to the present invention includes: (1) melting a crystal material in a crucible having a nozzle portion having a nozzle hole penetrating in a direction inclined with respect to the vertical direction, and melting the crystal material. A step of producing a liquid, (2) a step of discharging the melt from the nozzle hole into a granular form, and (3) a step of cooling and solidifying the granular melt during the fall. .

  In the nozzle portion, a plurality of the nozzle holes are provided, and the plurality of the granular melts discharged from the plurality of nozzle holes are prevented from coming into contact with another granular melt before the solidification thereof. It is preferable that the inclination of each nozzle hole is set.

  The melt outlets of the plurality of nozzle holes include a first melt outlet and a second melt outlet different in distance from the bottom of the crucible from the first melt outlet. Is preferred.

  In the plan view of the crucible, it is preferable that the plurality of nozzle holes are positioned on a closed curve, and the discharge direction of the melt from the plurality of nozzle holes is aligned clockwise or counterclockwise.

  In step (2), it is preferable that vibration is applied in the vertical direction to the crucible.

  In the step (2), it is preferable to apply a horizontal vibration that draws a substantially circular locus in plan view to the crucible.

 The crystal particle production apparatus of the present invention is provided with a nozzle portion having a nozzle hole penetrating in a direction inclined with respect to the vertical direction, and a crucible for discharging the crystal material melt from the nozzle hole into a granular shape; And a tubular body that solidifies the granular melt discharged from the nozzle hole while dropping inside.

  According to the method for producing crystal particles of the present invention, (1) the crystal material is melted in a crucible provided with a nozzle portion having a nozzle hole penetrating in a direction inclined with respect to the vertical direction at the bottom. A step of producing the melt of (2), (2) a step of discharging the melt from the nozzle hole into a granular shape, and (3) a step of cooling and solidifying the granular melt during dropping, Therefore, when the melt is discharged from the nozzle hole in a direction inclined with respect to the vertical direction, the granular melt has a velocity component in the horizontal direction as well as in the vertical direction. Therefore, even if there is a difference in the dropping speed of the granular melt 4a discharged from the same nozzle hole, the dropping trajectory of the discharged melt can be shifted, and the melts discharged from the nozzle hole Thus, it is possible to efficiently and stably produce crystal particles having a uniform shape and particle size.

  Preferably, in the method for producing crystal particles of the present invention, a plurality of the nozzle holes are provided in the nozzle portion, and the granular melt discharged from the plurality of nozzle holes is prior to solidification thereof. Suppressing the contact between the melt discharged from the nozzle and the melt discharged from another nozzle by setting the inclination of the plurality of nozzle holes so as not to come into contact with different granular melts, respectively. In addition, a large number of crystal grains can be produced.

  Preferably, in the method for producing crystal particles of the present invention, the melt outlets of the plurality of nozzle holes are a first melt outlet, and a distance from the bottom of the crucible is the first melt outlet. By including the different second melt discharge ports, the melt discharge positions from the respective discharge ports are different, so that the probability that the melts come into contact with each other during the fall can be reduced.

  Preferably, in the method for producing crystal grains of the present invention, the plurality of nozzle holes are positioned on a closed curve in the plan view of the crucible, and the discharge direction of the melt from the plurality of nozzle holes is respectively right. By aligning around the counterclockwise or counterclockwise direction, the contact between the melt discharged from the nozzle and the melt discharged from another nozzle can be further suppressed.

  In the method for producing crystal particles of the present invention, preferably, in the step (2), the crucible is vibrated in the vertical direction so that the melt is broken into granular droplets of uniform diameter. Can be made.

  In the method for producing crystal grains of the present invention, preferably, in the step (2), the crucible is subjected to a horizontal vibration that draws a substantially circular locus in plan view, so that the crucible is discharged. The position of the melt and the initial discharge speed of the melt in the horizontal direction can be changed from moment to moment, and collision with each other before solidification can be prevented from increasing.

  According to the crystal grain manufacturing apparatus of the present invention, a crucible is provided with a nozzle portion having a nozzle hole penetrating in a direction inclined with respect to the vertical direction, and discharging a melt of the crystal material from the nozzle hole into a granular shape; A tubular body that solidifies while dropping the granular melt discharged from the nozzle hole, and discharging the melt from the nozzle hole of the crucible while shifting the dropping trajectory, The melt can be solidified in the tubular body, and crystal particles having a uniform shape and particle size can be produced efficiently and stably.

  As described above, according to the method and apparatus for producing crystal particles of the present invention, crystal particles having a uniform shape and particle size can be stabilized in the dropping process of the granular crystal material melt to obtain crystal particles. Therefore, it is possible to improve the production yield when producing granular crystal particles such as granular silicon, and it is possible to reduce the manufacturing cost by removing abnormally shaped particles and eliminating the classification process.

  Hereinafter, examples of embodiments of the method for producing crystal grains of the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited to these drawings.

  FIG. 1 is a cross-sectional view schematically showing an example of an embodiment of an apparatus for producing crystal particles used in the method for producing crystal grains of the present invention.

  In FIG. 1, 1 is a crucible, 1a is a crucible bottom surface, 2 is a crucible body part, 2a is a crucible body inner wall part, 2b is a crucible body outer wall part, 3 is a nozzle part, 4 is a crystal material melt, 4a is a granular material The melt, 5 is a tubular body, 6 is a nozzle hole, and 7 is a melt outlet.

  The manufacturing apparatus in FIG. 1 includes a crucible 1 and a tubular body 5 disposed below the crucible 1 in the vertical direction. The crucible 1 includes a nozzle portion 3 provided at the bottom thereof, and a main body of the crucible 1. And the crucible body 2 constituting the above. And the nozzle part 6 is provided with the nozzle hole 6 penetrated in the inclination direction with respect to the vertical direction.

  Below, each structure in FIG. 1 is demonstrated.

<Crucible body 2>
The crucible body 2 is made of a material having excellent heat resistance and low reactivity with respect to the crystal material. The crucible body 2 is preferably composed of a crucible body outer wall 2b located outside the crucible body and a crucible body inner wall 2a located inside the crucible body. Since the crucible body inner wall portion 2a is in contact with the crystal material, it must be made of a material such as aluminum oxide, silicon carbide, graphite, silicon oxide and the like because it requires better heat resistance and low reactivity with the crystal material. It is preferable that Furthermore, the crucible body inner wall 2a is preferably produced by densifying them by a casting method such as casting or hot pressing. When the crucible body inner wall portion 2a is made of graphite, a purification treatment is performed with an acid or the like after the formation in order to improve the purity of the graphite.

  A gas supply mechanism for supplying a mixed gas of argon and helium or the like is provided inside the crucible body inner wall 2a, whereby the melt 4 can be pressurized from above.

  Here, in FIG. 1, the inner surface of the crucible 1 becomes thinner as it approaches the bottom, thereby obtaining the effect that the granular melt 4 a without any disturbance can be discharged vigorously.

  The crucible body outer wall 2b is provided to ensure the strength of the crucible 1, and is a sintered body or the like (for example, aluminum oxide, silicon carbide, (Graphite, silicon nitride). The crucible body 2 is composed of a crucible body inner wall 2a and a crucible body outer wall 2b. For example, the outside of the crucible body inner wall 2a and the inside of the crucible body outer wall 2b are assembled using screws or the like. May be.

<Nozzle part 3>
A nozzle part 3 is provided at the bottom part which is the front end side of the crucible 1. Here, the nozzle portion 3 refers to one provided with a hole (nozzle hole 6) penetrating in a tilt direction with respect to the vertical direction. The nozzle hole 6 is provided to discharge the crystal material melt 4 to form a granular melt 4a.

The nozzle portion 3 is made of silicon nitride, silicon carbide, boron nitride, diamond, aluminum oxide, cubic boron nitride, or the like. Further, the nozzle part 3 may be formed by setting the density of the constituent material. For example, in order to prevent the nozzle hole 6 from being worn and to form a stable granular crystal, the nozzle part 3 has a true specific gravity. Is made of silicon carbide of 3.0 g / cm ³ or more, cubic boron nitride of 3.30 g / cm ³ or more, diamond of 3.35 g / cm ³ or more, etc. It may be composed of silicon carbide, single crystal aluminum oxide (sapphire), single crystal cubic boron nitride, single crystal diamond, or the like.

  The inclination angle of the nozzle hole 6 with respect to the vertical direction is preferably 5 to 60 °. If the inclination angle is less than 5 °, it becomes difficult to sufficiently shift the respective falling trajectories of the granular melt 4a discharged from the same nozzle hole 6, and the granular melts 4a are combined before solidifying, There is a tendency that the particle size of the obtained granular metal crystal is distributed. Further, when the inclination angle exceeds 60 °, the discharged granular melt 4 a tends to collide with the inner wall of the tubular body 5.

  As for the diameter of the nozzle hole 6 of the nozzle part 3, 50-500 micrometers is preferable. If the diameter of the nozzle hole 6 is less than 50 μm, it is difficult to form the nozzle hole 6 with excellent accuracy, and it is necessary to apply a large pressure to discharge the granular melt 4, so that the apparatus is large. There is a tendency to become. Furthermore, when the diameter of the nozzle hole 6 is less than 50 μm, the particle size of the granular melt 4 tends to be small. Therefore, for example, when the crystal particles are crystalline silicon, adverse effects due to the diameter being too small, such as the efficiency of absorbing sunlight by a photoelectric conversion device using the crystalline silicon, are caused. On the other hand, if the diameter of the nozzle hole 6 exceeds 500 μm, the particle size of the melt 4 becomes large, the time until solidification becomes longer, and the apparatus becomes larger, and the degree of supercooling to obtain a good granular metal crystal is increased. There is a tendency that adverse effects such as a narrow margin occur.

  The nozzle hole 6 can be obtained by performing machining, laser processing, electric discharge processing, ultrasonic processing, or the like on the nozzle portion 3 and then performing wire polishing finishing so as to have the same hole diameter as necessary. .

<Tubular body 5>
The tubular body 5 arranged vertically from the nozzle portion 3 of the crucible 1 is a container that cools and solidifies the granular melt 4a discharged from the nozzle portion 6 during the fall. The inside of the tubular body 5 is controlled in a desired atmosphere. As this desired atmosphere, helium or argon is preferable. Helium or argon is an inert gas and can prevent impurities from entering the granular melt 4 from the atmosphere.

  The tubular body 5 can adjust an atmosphere such as internal pressure and gas concentration using a pump, a mass flow controller, or the like. As this tubular body 5, an O-ring, a gasket, or the like is used so that a portion where different tubular portions come into contact with each other is kept airtight. For example, a quartz tube, an alumina ceramic tube, or a stainless tube is used. be able to. The method for adjusting the atmosphere inside the tubular body 5 is not particularly limited as long as the pressure and gas concentration in the tubular body 5 can be adjusted.

<Production of crystal particles by the manufacturing apparatus of FIG. 1>
A procedure for producing crystal particles by the production apparatus of FIG. 1 will be described.

  First, a crystal material is melted in a crucible 1 having one nozzle hole 6 to produce a melt 4 of crystal material. For melting the crystal material, for example, an induction heater (not shown) or a resistance heater (not shown) is used, and the crystal material is melted by raising the temperature of the crucible above the melting point of the crystal material. Thus, the melt 4 is produced. For example, when the crystal material is silicon, the temperature of the crucible 1 is increased to 1400 ° C. or higher, which is the melting point of silicon. At this time, the internal pressure of the crucible is controlled, and the silicon melt is not yet discharged.

  Next, the melt 4 is discharged from the nozzle hole 6 to continuously produce a granular melt 4a. The melt 4 is discharged by pressurizing the melt 4 with an inert gas such as argon gas (pressure of 0.01 to 1 MPa) from the top of the melt 4. And the melt 4a is discharged | emitted in the inclination direction with respect to a perpendicular direction from the melt outlet 7 below the nozzle hole 6 inclined with respect to a perpendicular direction. When the melt 4a is discharged from the melt outlet 7 in a direction inclined with respect to the vertical direction, the granular melt 4a has a velocity component in the horizontal direction as well as in the vertical direction. Therefore, even if there is a difference in the speed of the granular melt 4a discharged from the same nozzle hole 6, it can be dropped along different drop trajectories.

  The discharged granular melt 4a is cooled and solidified during the fall to obtain granular crystal particles.

  As described above, by using the manufacturing apparatus of FIG. 1, the contact between the granular melts 4a before solidification is reduced, and crystal particles having a uniform shape and granularity are obtained.

  In the step of discharging the melt 4 from the nozzle hole 6, it is preferable to vibrate the crucible 1 in the vertical direction. By applying vertical vibration to the crucible 1, the melt 4 can be divided and dropped into a granular melt 4 a having a uniform diameter.

  Further, in the step of discharging the melt 4 from the nozzle hole 6, a horizontal vibration that draws a substantially circular trajectory (preferably the trajectory radius of the approximate circle is 0.05 to 1 mm) with respect to the crucible 1 in plan view. (The vibration frequency is preferably 10 to 1000 Hz). By applying such vibration to the crucible 1, the position at which the melt 4 is discharged and the initial horizontal velocity can be changed from moment to moment, so that the granular melt split to a uniform diameter can be obtained. , The increase of the particle diameter due to the collision with each other before the solidification can be suppressed.

<Preparation of crystal particles by the manufacturing apparatus of FIGS. 2 and 3>
2 and 3 show an apparatus for producing crystal particles having a plurality of nozzle holes. The manufacturing apparatus in FIGS. 2 and 3 is the same as the manufacturing apparatus in FIG. 1 except that the nozzle holes in the nozzle portion 3 are different.

  FIG. 2A and FIG. 3A show a manufacturing apparatus cut along the central axis of the crucible 2. 2 (b) and 3 (b) are a bottom view of the nozzle portion 3 when viewed from below the manufacturing apparatus of FIGS. 2 (a) and 3 (a), and nozzle holes 61 to 64. Sectional drawing of the nozzle hole cut | disconnected along each discharge direction (arrow in a figure) of the crystal particle discharged | emitted from the melt discharge holes 71-74 is shown.

  In FIG. 2, four nozzle holes 61 to 64 are provided concentrically on the disc-like nozzle portion 3, and the discharge direction of the granular melt is inclined with respect to the tangential direction of the concentric circles. Thus, by providing a plurality of nozzle holes 61 to 64 and tilting the discharge direction in the tangential direction of concentric circles, mutual contact by the granular melt 4a can be suppressed, and it has a uniform shape and particle size. A large amount of crystal particles can be produced at one time.

  In FIG. 2, the discharge direction of the granular melt is provided in the tangential direction of the concentric circles of the nozzle holes 61 to 64, but for example, in FIG. 3, the discharge direction of the melt from the nozzle hole 71 to the nozzle hole 72 is set. Directing the discharge direction of the melt from the nozzle hole 72 to the nozzle hole 73, or the like, by directing the discharge direction of the melt from the nozzle hole to the nozzle hole adjacent to the nozzle hole, respectively. And the collision of the granular melt with the inner wall of the tubular body 5 can also be suppressed.

  In this way, the inclination of the plurality of nozzle holes can be set so that the granular melt discharged from the plurality of nozzle holes does not come into contact with another granular melt before the solidification thereof. .

  Preferably, in the method for producing crystal particles of the present invention, the plurality of nozzle holes are positioned on a closed curve (on a circle in FIGS. 2 and 3) in a plan view of the crucible, and granular particles from the plurality of nozzle holes are formed. Since the discharge direction of the melt is aligned clockwise or counterclockwise (clockwise in FIGS. 2 and 3), the contact between the melt discharged from the nozzle and the melt discharged from another nozzle Can be further suppressed.

  Further, in the method for producing crystal particles of the present invention, preferably, as shown in FIGS. 2 (b) and 3 (b), the melt discharge ports 71 to 74 of the plurality of nozzle holes are provided with the first melt discharge. It is preferable to include outlets 71 and 73, and second melt outlets 72 and 74 that are different from the first melt outlet in the distance from crucible bottom surface 1a. In the case of FIG. 2B and FIG. 3B, the second melt discharge ports 72 and 74 protrude below the crucible 1 from the first melt discharge ports 71 and 73. The granular melt discharge position differs between the first melt discharge port and the second melt discharge port, and the adjacent nozzles are different from each other between the first melt discharge port and the second melt discharge port. By having the relationship, the contact probability between the discharged granular melts can be lowered. In particular, the length to the second melt outlets 72 and 74 and the length to the first melt outlets 71 and 73 are preferably different by 1 mm or more, and the contact probability between the melts is further reduced. be able to.

  A specific example of the method and apparatus for producing crystal particles of the present invention will be described below with reference to FIG. 2, but the present invention is not limited to this example.

<Example>
Using a drill, four holes are formed in a concentric circle having a diameter of 6 mm of a disk-shaped nozzle portion 3 (disc-shaped silicon carbide having an outer diameter of 13 mm and a thickness of 1 mm). Nozzle holes 71 to 74 (diameter 350 μm) were formed. These nozzle holes 71 to 74 are all inclined by 45 ° from a direction perpendicular to the surface of the nozzle portion 3 (a direction that is vertical when the manufactured manufacturing method is used). The difference between the distance from the crucible bottom 1a to the first melt outlets 71 and 73 and the distance from the crucible bottom 1a to the second melt outlet 72 was 0.2 mm. The discharge direction of the silicon raw material melt discharged from the four nozzle holes 61 to 64 was set so as to indicate the tangential direction of each nozzle hole in a concentric circle having a diameter of 6 mm in the nozzle portion 3 in plan view. .

  Next, the crucible 1 was produced by attaching the nozzle part 3 to the bottom of the crucible body part 2 (inner diameter 19 mm, outer diameter 25 mm, length 143 mm, made of graphite). And the silicon raw material was thrown into the crucible 1 as a melt, and the silicon raw material was melted by induction heating.

  Next, on the side of the crucible body outer wall 2b, a mechanism (not shown) for applying a horizontal vibration that draws a substantially circular locus in plan view is provided on the crucible 1, and the nozzle 3 is moved in the horizontal direction. The silicon raw material melt was discharged (discharge speed 1.5 m / s). As vibration conditions, the radius of the orbit of the nozzle hole of the crucible was about 0.5 mm, and the horizontal vibration frequency of the opening of the nozzle hole was about 11 Hz. These vibration conditions are set so that the crystalline silicon particles do not reach the tubular body and do not overlap with the dropping trajectory of the raw material melt discharged from the adjacent nozzle holes.

<Comparative example>
Example 1 except that the nozzle hole provided in the nozzle part is provided so as to penetrate perpendicularly to the surface of the nozzle part and that a mechanism for circular movement with respect to the outer wall member of the crucible is not provided. Then, a crucible was formed, and the silicon raw material melt was discharged.

<Experimental result>
In the examples, the obtained crystalline silicon particles had a uniform shape and particle size, and it was not confirmed that the crystalline silicon particles adhered to each other. Thus, in the Example, the crystalline silicon particle of uniform shape and particle size was able to be obtained stably and efficiently.

  On the other hand, in the comparative example, crystalline silicon particles having a particle size of 1 mm are continuously discharged from the same nozzle hole, and the distance between the crystalline silicon particles is short (about 0.4 mm), and the crystalline silicon particles in the front are Since the relative velocity of the rear crystalline silicon particles with respect to is high (about 70 mm / s), the time required for the two droplets to merge when following the same trajectory was as short as about 0.006 s. Thus, in the comparative example, a plurality of crystalline silicon particles adhere to each other and can be distributed in the size of the produced crystalline silicon particles, so that the crystalline silicon particles having a uniform shape and particle size can be stably produced. I couldn't.

It is sectional drawing which shows an example of embodiment of the manufacturing apparatus used for the manufacturing method of the granular metal crystal of this invention. (A) is sectional drawing which shows an example of embodiment of the manufacturing apparatus used for the manufacturing method of the granular metal crystal of this invention, (b) is the top view and sectional drawing of the nozzle part in the manufacturing apparatus. (A) is sectional drawing which shows an example of embodiment of the manufacturing apparatus used for the manufacturing method of the granular metal crystal of this invention, (b) is the top view and sectional drawing of the nozzle part in the manufacturing apparatus.

Explanation of symbols

1 crucible 2 crucible body 2a crucible body inner wall 2b crucible body outer wall 3 nozzle part 4 crystal material melt 4a granular melt 5 tubular body 6 61 62 63 64 nozzle hole 7 71 72 73 74 melt outlet

Claims (7)

(1) In a crucible provided with a nozzle portion having a nozzle hole penetrating in a direction inclined with respect to the vertical direction, a step of melting the crystal material to produce a melt of the crystal material;
(2) discharging the melt from the nozzle hole into a granular shape;
(3) a step of cooling and solidifying the granular melt during dropping;
The manufacturing method of the crystal grain containing this. In the nozzle part, a plurality of the nozzle holes are provided,
The inclination of the plurality of nozzle holes is set so that the granular melt discharged from the plurality of nozzle holes does not come into contact with another granular melt before solidification thereof. The manufacturing method of the crystal grain of description. The melt outlets of the plurality of nozzle holes are
A first melt outlet;
A second melt outlet having a distance from the bottom of the crucible different from the first melt outlet;
The manufacturing method of the crystal grain of Claim 2 containing this. In the plan view of the crucible, the plurality of nozzle holes are located on a closed curve,
The method for producing crystal grains according to claim 2 or 3, wherein the discharge direction of the melt from the plurality of nozzle holes is aligned clockwise or counterclockwise.   The method for producing crystal grains according to any one of claims 1 to 4, wherein in the step (2), the crucible is vibrated in a vertical direction.   The method for producing crystal grains according to any one of claims 1 to 5, wherein in the step (2), a horizontal vibration that draws a substantially circular locus in a plan view is applied to the crucible. A crucible provided with a nozzle portion having a nozzle hole penetrating in a direction inclined with respect to the vertical direction, and discharging a melt of the crystal material from the nozzle hole into a granular shape;
A tubular body for solidifying the granular melt discharged from the nozzle hole while dropping inside;
A crystal grain manufacturing apparatus comprising:

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