JP2015174800A - monosilane generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a monosilane generator comprising an efficient temperature keeping mechanism.SOLUTION: This invention provides a monosilane generator that generates monosilane by bringing hydrogen plasma and solid silicon into contact with each other, wherein a solid silicon installation table that is rotatable around a rotation axis in a plane substantially vertical to a cylindrical electrode is used.

Description

  The present invention relates to a monosilane generation apparatus, and in particular, monosilane generation having an efficient temperature maintenance mechanism capable of maintaining an optimum silicon surface temperature even when the plasma input power and pressure are increased. It relates to the device.

Conventionally, monosilane (SiH ₄ ) gas, which is important for forming a silicon-based thin film at low temperature, is a disproportionation reaction using trichlorosilane as a starting material, a reaction using magnesium silicide and liquid ammonia, and lithium hydride It was manufactured using either a reaction with aluminum and silicon tetrachloride. However, since all of the above conventional monosilane gas production methods use highly toxic chlorine, the environmental load due to the production of silicon is increasing year by year with the spread of crystalline silicon solar cells. In addition, the above production method using magnesium silicide or lithium / aluminum hydride requires the use of a metal that is more unstable than silicon, such as magnesium, lithium, or aluminum, as a reactant. Because of this, a lot of energy is consumed.

  The present inventors have developed a technique for producing monosilane by utilizing a direct reaction between atomic hydrogen generated in plasma and silicon as a technique that does not have the above-described problems (for example, Patent Document 1). According to this technology, no elements other than hydrogen and silicon necessary for monosilane production are required, so there is no significant environmental burden and the problem of energy consumption due to the use of unstable metals is solved. it can. Non-Patent Document 1 also describes a technique related to a monosilane production reaction by atomic hydrogen, and reports that the reaction proceeds most when the temperature of the silicon surface reaches about 50 ° C.

JP 2011-1207 A (published January 6, 2011)

S. Veprek, et al., J. Vac. Sci. Technol. 26, (2008), 313

  However, in the technology for producing monosilane by utilizing the reaction between atomic hydrogen generated in plasma and silicon, if the plasma input power or pressure is increased for the purpose of increasing the production rate of monosilane, it is a raw material. Since the temperature of the silicon surface rises, the energy consumption for maintaining the optimum silicon surface temperature for monosilane production is extremely increased. Therefore, even if the production amount of monosilane increases, there is a problem that the energy efficiency per unit amount of monosilane deteriorates.

  Specifically, as reported in Non-Patent Document 1, etc., as shown in FIG. 2 (in the figure, the silicon surface temperature is indicated as “Si temperature” and the etching rate is indicated as “Etch rate”), atomic hydrogen is used. It is known that the production reaction of monosilane due to has temperature dependence, and the reaction proceeds most when the temperature of the silicon surface reaches about 50 ° C.

  Here, in order to promote the hydrogenation and vaporization reaction of silicon, it is necessary to increase the density of atomic hydrogen that reaches the silicon surface. To that end, it is necessary to increase the pressure of the generated plasma and increase the power density. Become. However, in order to increase the density of atomic hydrogen, plasma generated using high pressure and high power tends to increase the gas temperature. For example, in FIG. 3 in which the plasma gas temperature (indicated as “Temperature” in the figure) is plotted against the input power (indicated as “Input power” in the figure) under an atmosphere of 18 Torr and a hydrogen flow rate of 5 slm. As shown, the plasma gas temperature rises depending on the power. With an input power of 350 W, the plasma gas temperature reaches 200 ° C. to 240 ° C. FIG. 4 shows the temperature change of the silicon surface after the plasma is turned on by bonding a thermocouple having a sheath diameter of 160 μm to the silicon surface in order to measure the temperature of the silicon surface exposed to the plasma generated with an input power of 350 W. It shows the results measured and recorded against the elapsed time (indicated as “Elapsed time” in the figure). The silicon wafer used for the plasma exposure had a thickness of 500 μm, and the back surface was placed in close contact with an aluminum installation table cooled by 15 ° C. cooling water. As shown in FIG. 4, even when the silicon is indirectly cooled from the back surface, the surface temperature rises to near 110 ° C. over time due to exposure to plasma generated with an input power of 350 W. I understand. In this way, even if the density of atomic hydrogen in the plasma is increased by increasing the input power, the temperature of the silicon surface rises above the optimum temperature accordingly, and the effect of increasing the density of atomic hydrogen is offset. Therefore, it does not lead to efficient production of monosilane.

  In the above case, in order to maintain the temperature of the silicon surface in the vicinity of 50 ° C., it is necessary to cool the installation table with a refrigerant of −25 ° C. Production of such a low-temperature refrigerant not only requires a large amount of energy for the operation of the compressor, but also requires a heavy piping system to prevent condensation and icing. In a general cooling system, the cooling capacity of the system decreases as the refrigerant temperature decreases. Therefore, the technique using an excessively low temperature refrigerant increases the total amount of energy required for the production of monosilane.

  The present invention has been made in view of the above-described problems, and its purpose is to provide an efficient temperature that can maintain the optimum silicon surface temperature even when the plasma input power and pressure are increased. An object of the present invention is to provide an apparatus for producing monosilane having a maintenance mechanism.

  In order to solve the above problems, a monosilane generation apparatus according to the present invention is a monosilane generation apparatus that generates monosilane by bringing hydrogen plasma generated in a hydrogen gas atmosphere into contact with solid silicon. A cylindrical electrode for generating hydrogen plasma in between, and a solid silicon installation table for installing the solid silicon, which is rotatable about a rotation axis in a plane substantially perpendicular to the cylindrical electrode. It is characterized by having.

  According to the above configuration, even if the input power and pressure of the plasma are increased in order to increase the production rate of monosilane, intermittent heating due to relative motion of solid silicon with respect to hydrogen plasma, and convective cooling due to rotation of solid silicon By utilizing this effect, the optimum temperature of the silicon surface can be maintained in an energy efficient manner as compared with a cooling method using a refrigerant produced by a refrigerator.

  In the monosilane production apparatus according to the present invention, by rotating the solid silicon installation table, the contact position between the solid silicon installed on the solid silicon installation table and the hydrogen plasma is within a plane substantially perpendicular to the cylindrical electrode. It is preferable to move on the circumference of a circle centered on the rotation axis.

  In the monosilane production | generation apparatus which concerns on this invention, it is preferable that the said cylindrical electrode is equipped so that the longitudinal direction may extend in a substantially perpendicular direction.

  With the above configuration, since the solid silicon can be placed horizontally, there is an effect that the installation of the solid silicon is easy.

  In the monosilane production | generation apparatus which concerns on this invention, it is preferable that the said solid silicon installation stand can fix solid silicon.

  With the above-described configuration, there is an effect that it is possible to reliably prevent the displacement of the solid silicon that may occur during the rotation of the solid silicon installation table.

  In the monosilane production | generation apparatus which concerns on this invention, the said solid silicon installation stand is formed in the surface facing the said cylindrical electrode the annular groove | channel centering on the said rotating shaft for accommodating solid silicon. It is preferable.

  Due to the above configuration, it is difficult to use as a raw material for monosilane production by plasma in the past, and further, it is possible to produce a solid production of abundant and inexpensive granular solid silicon in the groove as it is without forming into a plate shape. Can be used.

  In the monosilane production | generation apparatus which concerns on this invention, it is preferable that granular solid silicon is installed as said solid silicon.

  With the above configuration, since there is a gap between the particles, it is possible to effectively use granular silicon, which is a silicon raw material with extremely low thermal conductivity and poor cooling efficiency.

  In the monosilane production | generation apparatus which concerns on this invention, it is preferable that the cooling mechanism is provided in the said solid silicon installation stand.

  By combining the above cooling mechanism with intermittent heating by relative motion of solid silicon with respect to hydrogen plasma and convection cooling effect by rotation of solid silicon, it is possible to maintain the optimum silicon surface temperature more efficiently. There is an effect.

  As described above, the monosilane generation apparatus according to the present invention is a monosilane generation apparatus that generates monosilane by bringing hydrogen plasma generated in a hydrogen gas atmosphere into contact with solid silicon to generate hydrogen between the solid silicon. Since it includes a cylindrical electrode for generating plasma, and a solid silicon mounting base that can rotate around a rotation axis in a plane substantially perpendicular to the cylindrical electrode for installing the solid silicon. Because of the localization of the hydrogen plasma and the relative movement of the solid silicon, which is the raw material, with respect to the hydrogen plasma, the same location of the solid silicon is not always exposed to the hydrogen plasma, so the heating effect of the hydrogen plasma becomes intermittent. The temperature reached on the surface of solid silicon can be lowered.

  Also, by rotating the solid silicon, a gas flow is induced near the surface of the solid silicon due to friction between the solid silicon and the reactor atmosphere gas, and heat transfer by convection is promoted by this gas flow. Therefore, the cooling effect is further improved.

  Furthermore, by adopting a rotation mechanism as a mechanism for the relative movement of the raw material solid silicon with respect to hydrogen plasma, the only energy required to maintain the relative movement is the rolling friction caused by the bearing and the friction between the gas in the reaction vessel. Therefore, it is extremely energy efficient compared to a cooling method using a refrigerant produced by a refrigerator.

  That is, according to the present invention, even if the input power and pressure of the plasma are increased to increase the production rate of monosilane, intermittent heating due to relative motion of solid silicon with respect to hydrogen plasma, and convection due to rotation of solid silicon By utilizing the cooling effect, it is possible to maintain the optimum silicon surface temperature in an energy efficient manner as compared with a cooling method using a refrigerant produced by a refrigerator.

It is a typical perspective view showing one embodiment of the monosilane generating device concerning the present invention. It is a figure which shows the temperature dependence of the production | generation reaction of monosilane by atomic hydrogen. It is a figure which shows the input electric power dependence of plasma gas temperature. It is a figure which shows the result of having measured the temperature change of the silicon surface after plasma lighting. In the Example of this invention, it is a figure which shows the result of having measured the raw material rotation speed dependence of the etching amount of solid silicon. In the Example of this invention, it is a figure which shows the result of having measured the surface temperature of the solid silicon exposed to hydrogen plasma, (a) is the surface of the solid silicon accompanying hydrogen plasma passage when rotating solid silicon It is a figure which shows the result of having measured the change of temperature, (b) pays attention to one temperature rising peak which shows the temperature rise observed by (a), and respond | corresponds to the position from the nozzle center of a cylindrical electrode. It is a figure which shows the change of the surface temperature of solid silicon. In the Example of this invention, it is a figure which shows the result of having measured the rotation speed dependence of the surface temperature of solid silicon. In the Example of this invention, it is a figure which shows the result of having measured the raw material silicon | silicone thickness dependence of the etching amount at the time of no rotation and rotation. It is sectional drawing which shows typically one Embodiment of the monosilane production | generation apparatus which concerns on this invention. It is a figure which shows typically one Embodiment of the monosilane production | generation apparatus which concerns on this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings and examples. In the drawings of the present application, the same reference numerals denote the same parts or parts having the same function. Unless otherwise specified in this specification, “A to B” indicating a numerical range means “A or more and B or less”.

[Embodiment 1]
FIG. 1 is a schematic perspective view showing a preferred example of a monosilane generation apparatus 100 according to the present embodiment. The monosilane generation apparatus 100 is an apparatus that generates monosilane by bringing the hydrogen plasma 3 generated in a hydrogen gas atmosphere into contact with the solid silicon 2. As shown in FIG. 1, the monosilane generation apparatus 100 is connected to the solid silicon 2 in a reaction vessel (not shown) provided with an internal space serving as a reaction field for generating the monosilane by bringing the solid silicon 2 into contact with the hydrogen plasma 3. A cylindrical electrode 1 for generating a hydrogen plasma 3 in between, and a solid silicon installation table 4 for installing a solid silicon 2 around a rotation axis A in a plane substantially perpendicular to the cylindrical electrode 1. And. The cylindrical electrode 1 is provided so as to face the solid silicon 2 so that its longitudinal direction extends in a substantially vertical direction, and brings the hydrogen plasma generated between the cylindrical electrode 1 and the surface of the solid silicon 2 into contact with the solid silicon 2. The cylindrical electrode 1 includes a hydrogen gas supply means (not shown) for supplying hydrogen to the tip outlet of the cylindrical electrode 1 through the cylinder, and a microwave generation means (not shown) for supplying microwave power to the cylindrical electrode 1. And are provided.

  The solid silicon installation base 4 is attached to the rotating shaft body 5 and is driven by a motor (not shown) connected to the rotating shaft body 5 so as to be attached to the cylindrical electrode 1 around the rotating shaft A extending in a substantially vertical direction. Rotates in a nearly vertical plane. In other words, the cylindrical electrode 1 is provided above the solid silicon installation table 4 so as to be substantially perpendicular to the solid silicon installation table 4. Further, the cylindrical electrode 1 is configured to be movable in the vertical direction. When the cylindrical electrode 1 moves in the vertical direction, the distance between the lower solid silicon 2 and the tip outlet of the cylindrical electrode 1 is appropriately changed. Can be done.

  In the present invention, by rotating the solid silicon installation table 4, the contact position between the solid silicon 2 installed on the solid silicon installation table 4 and the hydrogen plasma 3 is within the plane substantially perpendicular to the cylindrical electrode 1. It moves on the circumference of a circle centered on the rotation axis A. That is, in the present invention, the cylindrical electrode 1 is fixed, and the solid silicon 2 installed on the solid silicon installation table 4 is moved relative to the hydrogen plasma 3.

  In the present embodiment, a plate-like solid silicon 2 is placed on the solid silicon installation table 4. Then, by rotating the solid silicon installation table 4, the position where the plate-like solid silicon 2 installed on the solid silicon installation table 4 and the hydrogen plasma 3 are in contact with each other is a surface substantially perpendicular to the cylindrical electrode 1. On the surface of the plate-like solid silicon 2 facing the cylindrical electrode 1, on the circumference of a circle centered on the rotational axis A and having a radius between the rotational axis A and the central axis of the cylindrical electrode 1 To move.

  Further, the solid silicon installation table 4 is grounded, and the solid silicon installation table 4 is provided with a cooling mechanism for cooling the solid silicon 2 installed on the solid silicon installation table 4. Water of 15 ° C. is used as the refrigerant for the cooling mechanism.

  According to the configuration of this embodiment, the same location of the solid silicon is not always exposed to the hydrogen plasma due to the localization of the hydrogen plasma and the relative movement of the solid silicon as a raw material with respect to the hydrogen plasma. The heating effect by the plasma becomes intermittent, and the temperature reached on the surface of the solid silicon is also lowered.

  Also, by rotating the solid silicon, a gas flow is induced near the surface of the solid silicon due to friction between the solid silicon and the reactor atmosphere gas, and heat transfer by convection is promoted by this gas flow. Therefore, the cooling effect is further improved.

  Furthermore, by adopting a rotation mechanism as a mechanism for the relative movement of the raw material solid silicon with respect to hydrogen plasma, the only energy required to maintain the relative movement is the rolling friction caused by the bearing and the friction between the gas in the reaction vessel. Therefore, it is extremely energy efficient compared to a cooling method using a refrigerant produced by a refrigerator.

Specifically, the energy Q _bear (kW) necessary for maintaining the relative motion is expressed as the following formula (1) as the heat generation amount of the bearing:
Q _bear = 1.03 × 10 ⁻⁶ × M _b × R (1)
(In the formula (1), _{M b} is the friction moment represented by the following formula (2) (N · mm) , R is the rotational speed (rpm).) Represented by. Here, the friction moment M _b is expressed by the following formula (2):
M _b = μ × P × r _a (2)
(In the formula (2), mu is the coefficient of friction, P is the bearing load (N), _{r a} is the bearing radius (mm).) Because represented by energy _{Q bear} the solid silicon installation When the mass of the base and the solid silicon is small and the rotational speed is not extremely high, a very small value is sufficient as compared with the case where the refrigerator is operated.

Also, the incident energy per unit time from hydrogen plasma to solid silicon is W _surf-si , the outflow of energy from the back surface of solid silicon is W _col-si , and the mass and specific heat of solid silicon are m _si and C _vp , respectively. Then, the temperature _Tsi of the solid silicon after the elapse of time t can be expressed by the following formula (3).
_Tsi = ( _Wsurf-si- Wcol _-si ) * t / ( _msi * _Cvp ) (3)
Here, when the central axis of the cylindrical electrode is set at a distance r from the rotation axis of the solid silicon, the hydrogen plasma draws a circular orbit having a circumference of 2πr on the solid silicon. When the diameter of the cylindrical electrode is d, the residence time ratio r _t in the hydrogen plasma and outside the hydrogen plasma at a certain point of the solid silicon that circulates is r _t = d / (2πr−d). Further, assuming that the residence time in hydrogen plasma is t _p (s) and the rotation speed of solid silicon is R (rpm), t _p = d / v, peripheral speed v = 2πr × R / 60 (m / s) Therefore, t _p = 30d / πrR. Above residence time t _p in the hydrogen plasma obtained as the heating time of the solid silicon, the residence time t _out outside the hydrogen plasma is equivalent to the cooling time of the solid silicon. The energy used for heating the solid silicon is supplied only from the hydrogen plasma, and the cooling is based on heat conduction to the back stage and heat transfer from the solid silicon to the reaction atmosphere outside the hydrogen plasma, ie, convection.

When a solid silicon as the initial condition is placed in room temperature, the silicon surface is heated to a residence time in t _p in a hydrogen plasma, the time point in the solid silicon by the relative movement is staying outside the hydrogen plasma Within t _out , the silicon surface will be cooled. In other words, by controlling the residence time outside and inside the hydrogen plasma with respect to the plasma generation conditions such as the input power and hydrogen flow rate for generating the hydrogen plasma, the surface temperature of the solid silicon that is the raw material is changed to the monosilane production reaction. It is possible to maintain the temperature at which the temperature proceeds optimally.

  Silicon as a raw material for monosilane is not necessarily limited to a solid silicon bulk, and may take the form of a sintered body of silicon powder, a porous body, or granular silicon. Also, the thickness and shape of solid silicon, which is a raw material for monosilane, vary. Such a silicon powder sintered body, porous body, or granular silicon has a very poor thermal conductivity compared to a solid silicon bulk. In addition, the thermal conductivity deteriorates as the thickness of the solid silicon increases. In such a system using solid silicon with poor thermal conductivity as a raw material, when cooling is performed by heat absorption using the cooling mechanism provided on the solid silicon installation base from the back side of the solid silicon, the surface of the solid silicon is efficiently cooled. I can't do it. Therefore, when using a sintered body of silicon powder, granular silicon, or solid silicon having a large thickness, it is possible to actively remove heat from the surface side of heated solid silicon. Intermittent plasma exposure due to rotation and heat transfer due to convection have a significant effect on maintaining an optimum temperature on the surface of the solid silicon.

  On the other hand, in order to suppress overheating of the surface of solid silicon, there is a method of intermittently generating plasma by modulating the on / off of the plasma generation power source, but this method has a plasma off time that is a cooling time Therefore, the production of monosilane becomes impossible within this time, and the amount of monosilane obtained when the treatment is performed for the same time decreases depending on the plasma off time for cooling the silicon. In contrast, according to the relative motion method of the present invention, when viewed from a certain point on the silicon material, the plasma is repeatedly turned on and off, but the plasma itself exists continuously and the material silicon Since the reaction continues, monosilane can always be produced. That is, the yield of monosilane increases compared to intermittent plasma operation. For this reason, as compared with other methods, the method of moving the silicon material relative to the localized plasma enables very efficient monosilane production.

  In addition, although the solid silicon 2 used in this embodiment is a plate shape, the shape of the solid silicon 2 used is not necessarily limited to a plate shape, and may be a block shape, a granular shape, or the like as described above. Also, the effects of the present invention can be obtained. Further, the solid silicon 2 used in the present embodiment is not limited to the solid substance, and the effects of the present invention can be obtained even if it is a sintered body, porous body, or the like of silicon powder.

  Further, the solid silicon 2 used in the present embodiment is placed on the solid silicon installation table 4, but in order to prevent the solid silicon from dropping from the installation table which may occur when the solid silicon installation table rotates, the solid silicon 2 is used. The silicon installation base 4 may be capable of fixing the solid silicon 2. The means for fixing the solid silicon 2 is not particularly limited as long as it is a member or apparatus for fixing the solid silicon 2 to the solid silicon installation base 4. For example, a vacuum chuck for adsorbing and fixing the solid silicon 2 may be provided as an apparatus for fixing the solid silicon 2 to the solid silicon installation base 4.

  Moreover, in this embodiment, although the material which comprises the solid silicon installation stand 4 is not specifically limited, For example, aluminum, copper, silicon, graphite etc. can be used suitably.

  Further, in the present embodiment, 15 ° C. water is used as a coolant of the cooling mechanism for cooling the solid silicon 2 installed on the solid silicon installation table 4, but the coolant is not necessarily limited to this. Instead, other refrigerants such as ethylene glycol, fluorinate, and silicone oil may be used. Moreover, the temperature of water as a refrigerant | coolant is also not specifically limited, Preferably it is -5 degreeC-40 degreeC.

  In this embodiment, if the cylindrical electrode 1 is cylindrical, the shape will not be specifically limited, For example, a cylindrical electrode can be used suitably. However, the cylindrical electrode 1 is not limited to this, and the cross-sectional shape perpendicular to the longitudinal direction may be any shape. The shape of the cross section perpendicular to the longitudinal direction is, for example, a polygon such as a triangle, a quadrangle, or a pentagon, or an ellipse.

  In the present embodiment, the cylindrical electrode 1 is provided such that its longitudinal direction extends in a substantially vertical direction. However, the direction is not limited to this, and the rotation surface of the solid silicon installation table 4 is not limited thereto. As long as they are perpendicular to each other, they may extend in any direction. When the cylindrical electrode 1 is provided such that its longitudinal direction extends in a substantially vertical direction, the solid silicon 2 can be placed horizontally, so that the installation of the solid silicon is easy.

  In addition, if the cylindrical electrode 1 is perpendicular to the rotation surface of the solid silicon installation table 4, the plasma is localized only between the solid silicon placed on the solid silicon installation table 4 and the tip outlet of the cylindrical electrode. This is very preferable. However, the cylindrical electrode 1 and the rotating surface of the solid silicon mounting base 4 are not necessarily perpendicular as long as plasma can be generated between the solid silicon and the tip outlet of the cylindrical electrode. May be. Preferably, it may be substantially vertical. For example, the central axis of the cylindrical electrode and the perpendicular to the rotation surface of the solid silicon mounting table 4 may be at an angle of 15 degrees or less, more preferably 5 degrees or less. Good.

  An example of a method for producing monosilane using the monosilane production apparatus 100 according to the present embodiment will be described below.

  First, after sufficiently exhausting the gas inside the reaction vessel, hydrogen gas is introduced into the reaction vessel through the inside of the cylindrical electrode 1 from the hydrogen gas supply means. Here, the pressure inside the reaction vessel is maintained at a predetermined pressure by simultaneously supplying the hydrogen gas and exhausting the gas.

  Next, microwave power is applied to the cylindrical electrode 1 from microwave generation means provided outside the reaction vessel. When this microwave power is applied to the cylindrical electrode 1, an electric field is generated between the cylindrical electrode 1 and the solid silicon mounting table 4.

  The electric field formed between the cylindrical electrode 1 and the solid silicon mounting table 4 decomposes and excites the hydrogen gas supplied between the cylindrical electrode 1 and the surface of the solid silicon 2, and thereby the cylindrical electrode 1. And a hydrogen plasma 3 is formed between the surface of the solid silicon 2. The hydrogen plasma 3 comes into contact with the surface of the solid silicon 2, and atomic hydrogen generated by the hydrogen plasma 3 acts on the surface of the solid silicon 2 to generate monosilane gas.

  At this time, by rotating the solid silicon installation table 4, the contact position between the solid silicon 2 installed on the solid silicon installation table 4 and the hydrogen plasma 3 is rotated in the plane substantially perpendicular to the cylindrical electrode 1. A circle on the axis A is moved on the circumference. Thereby, the solid silicon surface is heated when a certain point of the solid silicon 2 stays in the hydrogen plasma and the monosilane production reaction occurs, and when the point stays outside the hydrogen plasma, Will be cooled.

  In the monosilane production apparatus 100 according to the present embodiment, the pressure in the reaction vessel may be 10 Torr (1.33 kPa) to atmospheric pressure.

[Embodiment 2]
FIG. 9 is a schematic cross-sectional view showing a preferred example of a monosilane generation apparatus 20 according to another embodiment of the present invention. The monosilane production | generation apparatus 20 which concerns on this embodiment differs in the structure of the solid silicon installation stand 4 from the monosilane production | generation apparatus 100 which concerns on Embodiment 1. FIG.

  In the monosilane production | generation apparatus 20 which concerns on this embodiment, as shown in FIG. 9, the rotation axis A for accommodating solid silicon in the surface facing the cylindrical electrode 1 in the solid silicon installation stand 4 and 4 '. An annular groove 15 is formed around the center. The groove 15 contains granular solid silicon 2 as the solid silicon 2. Granular solid silicon is solid silicon that is very inexpensive and abundantly produced compared to solid silicon processed into a plate shape.

  In this embodiment, by rotating the solid silicon installation table 4, the contact position between the granular solid silicon 2 installed on the solid silicon installation table 4 and the hydrogen plasma 3 is a surface substantially perpendicular to the cylindrical electrode 1. On the surface of the granular solid silicon 2 facing the cylindrical electrode 1, on the circumference of a circle centered on the rotational axis A and having a radius between the rotational axis A and the central axis of the cylindrical electrode 1. To move. Thereby, in the normal solid silicon installation stand in which the groove 15 is not formed, the granular solid silicon 2 which is difficult to install can be brought into good contact with the hydrogen plasma 3. Therefore, granular solid silicon, which has been difficult to use as a raw material for monosilane generation by plasma, can be used as it is. Furthermore, compared with bulk or plate-like solid silicon, granular solid silicon has extremely low thermal conductivity and poor cooling efficiency because there are gaps between the particles. Therefore, according to the monosilane generation apparatus 20 according to the present embodiment, heat can be actively taken from the surface side of the heated solid silicon, and heat caused by intermittent plasma exposure and convection due to rotation of the solid silicon. The transmission has a great effect on maintaining the optimum temperature of the surface of the solid silicon.

  In the present invention, the granular silicon means granular silicon having an average particle diameter of 5 mm or less, more preferably 1 mm to 2 mm. Here, the average particle size of the solid silicon to be used is defined as the particle size of the particles obtained by screening by a screening method using a standard sieve having a nominal opening defined in JIS Z8801 or the like corresponding to the above particle size. .

  In the present embodiment, the solid silicon installation base 4, 4 ′ is composed of two members, a lower member 4 and an upper member 4 ′. However, the solid silicon installation base is such that the lower member 4 and the upper member 4 ′ are integrated. It may consist of a single member. Since the solid silicon installation base 4, 4 ′ is composed of two members, both the configuration as in the first embodiment and the configuration as in this embodiment can be achieved by simply attaching and detaching the upper member 4 ′. Can be used.

  In this embodiment, the cross-sectional shape of the groove 15 when cut along the plane including the rotation axis A is a rectangle, but the cross-sectional shape of the groove 15 is not limited to this, and the corner portion of the rectangle is rounded. It may be a shaped shape, a semicircular shape, a triangle having the bottom of the groove 15 as a vertex, a trapezoid, or the like. Further, the depth and width of the groove 15 are not particularly limited.

  The solid silicon 2 used in the present embodiment is preferably in the form of particles, but is not necessarily in the form of particles, and may be in the form of a plate or a lump as long as it can be accommodated in the groove 15.

  Further, the solid silicon 2 used in the present embodiment is installed by being accommodated in the groove 15 formed in the solid silicon installation table 4, but the solid silicon installation table 4 fixes the solid silicon 2 to the groove 15. It may be possible. Further, the means for fixing the solid silicon 2 is not particularly limited.

  Since the configuration other than the solid silicon installation base 4 of the monosilane generation apparatus 20 according to the present embodiment and the method for generating monosilane are the same as those in the first embodiment, the description thereof is omitted here.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and can be obtained by appropriately combining technical means disclosed in different embodiments. Embodiments are also included in the technical scope of the present invention.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by an Example.

  In this example, the etching amount of solid silicon was determined by the following method.

[Etching amount of solid silicon]
The weight of the solid silicon before the exposure of the hydrogen plasma to the solid silicon and the weight of the hydrogen plasma after the exposure to the solid silicon are measured by an electronic balance, and the difference between the weight before the start of the exposure and the end of the exposure is determined by the solid silicon. It was set as the etching amount.

[Example 1]
A hydrogen introduction line 8 as a hydrogen gas supply means for supplying hydrogen to the tip outlet of the cylindrical electrode 1 through the inside of the cylindrical electrode 1 and a mass flow controller for adjusting the supply amount of hydrogen to the outlet of the cylindrical electrode 1 14 and a cylindrical electrode 1 provided with a microwave oscillator 7 for supplying microwave power to the cylindrical electrode 1, and solid silicon that rotates about a rotation axis A in a plane substantially perpendicular to the cylindrical electrode 1 A monosilane was produced by bringing the hydrogen plasma 3 produced in a hydrogen gas atmosphere into contact with the solid silicon 2 using the monosilane production apparatus 30 shown in FIG. In the monosilane generation apparatus 30, the microwave oscillator 7 applies microwave power to the cylindrical electrode 1 through the waveguide 10 provided with the microwave matching unit 11 and the movable short-circuited end 12 and the dielectric 13. It is configured to supply.

  A solid attached to the rotating shaft 5 and driven by a motor (not shown) connected to the rotating shaft 5 so as to rotate in a plane substantially perpendicular to the cylindrical electrode 1 about a rotating shaft A extending in a substantially vertical direction. The plate-shaped solid silicon 2 was installed on the silicon installation table 4. The solid silicon 2 was cooled by a cooling mechanism using 15 ° C. water provided on the solid silicon installation table 4 as a refrigerant.

  First, after the gas inside the reaction vessel 6 was sufficiently exhausted by the gas exhaust line 9, hydrogen gas was introduced into the reaction vessel 6 from the hydrogen introduction line 8 through the inside of the cylindrical electrode 1.

  Next, while rotating the solid silicon mounting table 4, microwave power is applied from the microwave oscillator 7 to the cylindrical electrode 1 through the waveguide 10, so that the cylindrical electrode 1 and the surface of the solid silicon 2 are A hydrogen plasma 3 was formed between them and reacted with the solid silicon 2. The dielectric 13 is installed for blocking the atmosphere of the waveguide 10 and the reaction vessel 6, and also the reaction vessel 6 and the outside air, and transmitting microwave power via the cylindrical electrode 1.

  In this embodiment, since the distance between the rotation axis A of the solid silicon 2 and the central axis of the cylindrical electrode 1 is 30 mm, the reaction is performed by bringing the hydrogen plasma 3 into contact with the solid silicon 2 while rotating the solid silicon mounting table 4. As a result, etching marks were generated on the solid silicon 2 in an annular shape with a diameter of 60 mm due to reaction with hydrogen plasma. The shape of the etching mark was evaluated with a stylus type roughness meter.

  In this embodiment, the mass flow controller 14 sets the hydrogen flow rate to 5 slm, the etching time, that is, the time from the start of exposure of the hydrogen plasma 3 to the solid silicon 2 to the end of exposure, and the plasma gap, that is, the cylinder The basic condition was that the distance between the tip outlet of the electrode 1 and the surface of the solid silicon 2 was 0.5 mm, and the hydrogen pressure in the reaction vessel was 18 Torr. The input power was fixed at 350 W, the solid silicon mounting table 4 on which the solid silicon 2 was placed was rotated at various rotational speeds, and the dependency of the etching amount of the solid silicon 2 on the rotational speed was investigated. Note that the etching amount of the solid silicon 2 under the basic conditions described above corresponds to the amount of solid silicon that reacts within a certain period of time under a certain amount of hydrogen, and is therefore an index of the production rate of monosilane.

<Depending on the rotational speed of the etching amount of the solid silicon 2>
FIG. 5 shows the result of investigating the rotational speed dependency of the etching amount of the solid silicon 2. In the figure, the vertical axis represents the etching amount of solid silicon (indicated as “Etching”), and the horizontal axis represents the number of rotations (indicated as “Rotation”). From FIG. 5, when hydrogen plasma is reacted with solid silicon while rotating solid silicon, the rotational speed of solid silicon, which is a raw material, is rotated, so that the etching rate of silicon is compared to when solid silicon is not rotated. In other words, it was revealed that the production rate of monosilane increases.

  Further, it was confirmed that when the power of 350 W was turned on, the etching amount was maximized when the rotation speed was set near 30 rpm. When the input power is 350 W, the reason why such an optimum value of the rotational speed exists is that when the rotational speed is slow, the solid silicon stays longer in the hydrogen plasma and the surface temperature of the solid silicon is optimal. This is because the temperature has risen too much, and when the number of revolutions is high, it is considered that the time during which the solid silicon stays in the hydrogen plasma is too short and the surface temperature of the solid silicon has not reached the optimum temperature.

[Example 2]
Under the same basic conditions as in Example 1, the input power is fixed at 350 W, the solid silicon mounting table 4 on which the solid silicon 2 is placed is rotated at various rotational speeds, and the surface temperature of the solid silicon 2 depends on the rotational speeds. I examined the sex.

  In order to measure the change in the surface temperature of the solid silicon 2 at the time of rotation, a sheath thermocouple having a diameter of 80 μm was bonded to the surface of the solid silicon 2 and the surface temperature was measured while rotating the solid silicon mounting table 4.

  First, FIG. 6A shows the result of measuring the change in the surface temperature of the solid silicon accompanying the passage of hydrogen plasma when the solid silicon 2 is rotated at 5 rpm. In the figure, the vertical axis indicates the surface temperature of the solid silicon 2 (indicated as “Temperature”), and the horizontal axis indicates the time elapsed (indicated as “Elapsed time”). As shown in FIG. 6A, it can be seen that the temperature rises when a thermocouple enters the hydrogen plasma 3 as the solid silicon 2 rotates. In FIG. 6B, focusing on one temperature rise peak indicating the temperature rise observed in FIG. 6A, the horizontal axis indicating the time passage of FIG. FIG. 3 is a diagram showing a state converted from a nozzle center (indicated as “Position”) located on the central axis of the cylindrical electrode 1 by utilizing the fact that is known. As shown in FIG. 6B, when the solid silicon enters the hydrogen plasma, the surface temperature of the solid silicon rises rapidly. However, because of the configuration of this apparatus, fresh hydrogen gas is supplied from around the electrode center axis. It was observed that the temperature once decreased in the vicinity. The rotation speed dependence of the surface temperature of the solid silicon was examined using an average value obtained by measuring the maximum value of the ultimate temperature obtained by performing such dynamic measurement 10 times as the surface temperature of the solid silicon.

<Rotational speed dependence of surface temperature of solid silicon>
FIG. 7 shows the result. In the figure, the vertical axis represents the surface temperature of solid silicon determined as described above (indicated as “Average peak temperature”), and the horizontal axis represents the number of rotations (indicated as “Rotation”). 3 and 7, when hydrogen plasma is reacted with solid silicon while solid silicon is rotated, the solid silicon as a raw material is rotated, so that the solid silicon is not rotated. It can be seen that the surface temperature of the solid silicon is lowered. Therefore, it was confirmed that the surface temperature of the solid silicon exposed to the hydrogen plasma decreases because the exposure time of the solid silicon to the hydrogen plasma decreases as the rotational speed increases. Here, in FIG. 7, it can be seen that when the rotational speed is 30 rpm at which the etching amount is maximized, the temperature of the silicon surface is maintained at an optimum level.

Example 3
Under the same basic conditions as in Example 1, the dependence of the etching amount on the raw material silicon thickness was compared between a rotation speed of 30 rpm and a rotation speed of 0 rpm (no rotation).

  In order to change the heat transfer of solid silicon as solid silicon 2 with the input power fixed at 450 W, various numbers of silicon wafers (one, two, four, six) with a thickness of about 500 μm. ), The variation in the etching amount when rotating and when not rotating when the heat conduction to the solid silicon mounting table 4 serving as a heat sink was suppressed by stacking on the solid silicon mounting table 4 was investigated. .

<Depending on the silicon thickness of the material during the non-rotating and rotating etching amount>
FIG. 8 shows the result. In the figure, the vertical axis indicates the etching amount (displayed as “Etching”), the horizontal axis indicates the thickness of the raw silicon, and the number of stacked silicon wafers each having a thickness of about 500 μm (displayed as “Si wafers”). In addition, the total thickness (indicated as “Si thickness”) when a single silicon wafer having a thickness of about 500 μm is stacked is shown. In this embodiment, since the raw material silicon is not a continuous bulk body formed by simply stacking silicon wafers, the thermal contact between the silicon wafer and the silicon wafer is not good, and each time the number of the stacked silicon wafers is increased, there is a large transfer of heat conduction. Thermal resistance will be generated. From FIG. 8, a decrease in the etching amount of the raw silicon is observed with an increase in the number of silicon wafers, both during rotation and without rotation. However, when the number of silicon wafers is the same, the raw silicon is rotated. It can be seen that a larger etching amount can be obtained than when no rotation is performed. Then, the silicon etching amount when the six silicon wafers are stacked and rotated under the condition of greatly reducing the heat conduction characteristic, and the heat conduction characteristic to the solid silicon installation table 4 with the single silicon wafer installed is the most. Comparing the amount of silicon etching under non-rotating conditions under good conditions, the amount of etching when rotating the silicon wafers under the condition of drastically lowering the heat conduction characteristics by stacking six silicon wafers is only one silicon wafer. The heat conduction characteristics to the solid silicon mounting table 4 are larger than the etching amount when there is no rotation under the best conditions. This suggests that the cooling effect due to the rotation of the raw material silicon is not dependent on the heat conduction of the silicon, and that the heat radiation by the convection from the silicon surface plays a major role.

  According to the present invention, even if the plasma input power and pressure are increased in order to increase the production rate of monosilane, intermittent heating due to relative movement of solid silicon with respect to hydrogen plasma, and convective cooling effect due to rotation of solid silicon By using this, it is possible to maintain the optimum silicon surface temperature in an energy efficient manner as compared with a cooling method using a refrigerant produced by a refrigerator. Therefore, monosilane gas can be produced extremely efficiently.

  Therefore, without using a large amount of dangerous and difficult-to-handle monosilane gas as a cylinder, a silicon-based thin film that uses monosilane gas as a raw material, such as thin film transistors, LSIs, and solar cells, is used by using a compact device based on the present invention when necessary. It can be used for the manufacture of electronic devices and the synthesis of chemicals using monosilane.

DESCRIPTION OF SYMBOLS 1 Cylindrical electrode 2 Solid silicon 3 Hydrogen plasma 4 Solid silicon installation stand 4 'Solid silicon installation stand 5 Rotating shaft body 6 Reaction vessel 7 Microwave oscillator 8 Hydrogen introduction line 9 Gas exhaust line 10 Waveguide 11 Microwave matching device 12 Movable short-circuit end 13 Dielectric 14 Mass flow controller A Rotating shaft

Claims (7)

In a monosilane generation apparatus that generates monosilane by contacting hydrogen plasma generated in a hydrogen gas atmosphere with solid silicon,
A cylindrical electrode for generating hydrogen plasma with the solid silicon;
A monosilane production apparatus comprising: a solid silicon installation table that is rotatable about a rotation axis in a plane substantially perpendicular to the cylindrical electrode for installing the solid silicon.   By rotating the solid silicon installation table, a contact position between the solid silicon and hydrogen plasma installed on the solid silicon installation table is a circle centered on the rotation axis in a plane substantially perpendicular to the cylindrical electrode. The monosilane production | generation apparatus of Claim 1 characterized by the above-mentioned.   The monosilane production apparatus according to claim 1 or 2, wherein the cylindrical electrode is provided such that a longitudinal direction thereof extends in a substantially vertical direction.   The monosilane production apparatus according to any one of claims 1 to 3, wherein the solid silicon installation base is capable of fixing solid silicon.   The annular solid groove centering on the rotating shaft for housing the solid silicon is formed on the surface of the solid silicon mounting table facing the cylindrical electrode. The monosilane production | generation apparatus of any one of 4.   6. The monosilane production apparatus according to claim 5, wherein granular solid silicon is installed as the solid silicon.   The monosilane production | generation apparatus of any one of Claims 1-6 by which the cooling mechanism is provided in the said solid silicon installation stand.

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