JP2011001207A - Monosilane producing apparatus and monosilane forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a monosilane producing apparatus which can largely decrease the incidence of a secondary product of particles or the like and efficiently perform the SiHgasification of solid silicon when SiHis formed using the reaction of solid silicon and hydrogen plasma, and to provide a monosilane forming method.SOLUTION: The SiHproducing apparatus performs the catalytic reaction of hydrogen plasma formed under a hydrogen gas atmosphere and a solid silicon 2 to thereby form monosilane. The hydrogen plasma is generated by impressing an electric power between an electrode 1 and the solid silicon 2. In a flow direction of a hydrogen gas along the solid silicon 2, a control means which controls the hydrogen plasma region residence time of the hydrogen gas which passes through a hydrogen plasma region 3 where the hydrogen plasma is present to less than the time in which a formed monosilane starts a decomposition reaction in the hydrogen plasma region 3 is prepared.

Description

The present invention relates to a SiH ₄ generation apparatus and a SiH ₄ generation method capable of efficiently converting solid silicon into SiH ₄ gas by reaction between hydrogen plasma and solid silicon.

Monosilane (SiH ₄ ) gas is an indispensable gas for manufacturing electronic devices such as thin film transistors, super LSIs, and solar cells using silicon-based thin films, and is very useful.

SiH ₄ is generally produced by a disproportionation reaction of trichlorosilane (SiHCl ₃ ). For example, Patent Document 1 discloses a production method thereof. The SiH ₄ production reaction from SiHCl ₃ can be represented by the following chemical formula 1.

4SiHCl ₃ → SiH ₄ + 3SiCl ₄ (Chemical formula 1)
As can be seen from the above reaction formula, the yield of SiH ₄ with respect to the raw material SiHCl ₃ is as low as 25%, and three times as much silicon tetrachloride (SiCl ₄ ) as Si ₂ is produced as a by-product. End up. In order to increase the yield of SiH ₄ , a large-scale apparatus and process for recovering SiCl ₄ and reprocessing it into SiHCl ₃ , know-how, and the like are required, which requires a great deal of cost and labor. In addition, since the above-mentioned process is a process containing chlorine, it is necessary to take measures on equipment against chlorine corrosion, and there is also a problem that the environmental load is large.

On the other hand, as another method of obtaining SiH ₄ , a method of directly generating SiH ₄ by treating (etching) the solid raw material Si with atomic hydrogen generated by hydrogen plasma or the like can be considered. For example, in Non-Patent Document 1, generation of SiH _4, SiH ₃ , SiH ₂ , SiH, and the like has been confirmed by hydrogen plasma etching of solid silicon. According to this method, the only gas used is hydrogen, and it is not necessary to use chlorine. Therefore, it is possible to avoid the problems such as the countermeasures against corrosion and the environmental load described above.

Japanese Examined Patent Publication No. 64-3806 (published January 23, 1988)

Japan journal of Applied Physics Vol. 33 (1994) p. L1117-L1120

  However, the method for producing monosilane according to Non-Patent Document 1 has a problem that it is difficult to efficiently produce monosilane.

More specifically, when solid silicon is simply subjected to hydrogen plasma treatment, the generated SiH ₄ is decomposed when exposed to the plasma for a long time, and short-lived radicals such as SiH and SiH ₂ are formed. Due to this unstable short-lived radical, in addition to SiH ₄ gas, higher order silanes (Si _X H _{2X + 2} (X is an integer of 2 or more), that is, Si ₂ H ₆ , Si ₃ H ₈ ,...) And by-products in the form of fine particles (particles) in which they are polymerized, and it is difficult to efficiently produce monosilane gas.

The present invention has been made in view of the above-described conventional problems, and its purpose is to produce by-products such as particles when SiH ₄ is generated by utilizing a reaction between solid silicon and hydrogen plasma. An object of the present invention is to provide a SiH ₄ generation apparatus and a SiH ₄ generation method capable of significantly reducing the generation rate and efficiently converting solid silicon into SiH ₄ gas.

  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 contacting hydrogen plasma generated in a hydrogen gas atmosphere with solid silicon to generate hydrogen along solid silicon. Control means for controlling the hydrogen plasma region residence time of the hydrogen gas passing through the hydrogen plasma region where hydrogen plasma exists in the gas flow direction to be less than the time during which the generated monosilane undergoes a decomposition reaction in the hydrogen plasma region. It is characterized by being provided.

According to the above invention, SiH ₄ is generated by generating hydrogen plasma in a hydrogen atmosphere and bringing it into contact with solid silicon. SiH ₄ decomposes and forms radicals when exposed to plasma for a long time. By the reaction of these radicals, by-products such as particles can be generated. However, by controlling the residence time in the hydrogen plasma region to be less than the time during which SiH ₄ undergoes a decomposition reaction, the generation of the by-products can be suppressed and SiH ₄ can be produced with high efficiency.

  In the monosilane generation apparatus according to the present invention, the hydrogen plasma is generated by applying power between the electrode and the solid silicon, and the control means includes a hydrogen gas supply flow rate to the hydrogen plasma region, a hydrogen plasma. The hydrogen plasma is controlled by controlling at least one of a hydrogen gas suction flow rate from the region, a distance between the electrode and solid silicon, and a length of the hydrogen plasma region with respect to a flow direction of hydrogen gas along the solid silicon. It is preferable to control the region residence time.

  When the control unit performs the control, it is possible to easily control the residence time in the hydrogen plasma region.

  Moreover, in the monosilane production | generation apparatus which concerns on this invention, the said control means controls the high frequency electric power for hydrogen plasma generation to output to the said electrode in a pulse form, The hydrogen gas which passes a hydrogen plasma area | region is controlled. It is preferable to control the residence time of the hydrogen plasma region.

As a result, it is possible to form a state in which hydrogen plasma is generated for a certain period and not generated for the next certain period. Therefore, the generated SiH ₄ is hardly decomposed by the influence of hydrogen plasma, and the generation of by-products can be further suppressed. Further, since the generated SiH ₄ is difficult to be decomposed, there is an advantage that the flow rate of hydrogen gas for escaping SiH ₄ from the hydrogen plasma region may be small.

  Moreover, in the monosilane production | generation apparatus which concerns on this invention, it is preferable that the said control means controls the said hydrogen plasma area residence time to become 20 microseconds or less.

If the upper limit of the hydrogen plasma region residence time is 20 μsec, decomposition of SiH ₄ can be efficiently suppressed and the yield of SiH ₄ can be improved.

  Moreover, in the monosilane production | generation apparatus which concerns on this invention, while the solid silicon installation part which installs the said solid silicon is provided, the cooling means for cooling solid silicon is provided in the said solid silicon installation part. preferable.

  By providing the cooling means, it is possible to keep the solid silicon at a low temperature when the solid silicon is etched in the presence of hydrogen gas. The lower the temperature of the solid silicon, the higher the etching processing speed, so that monosilane can be efficiently generated.

  Moreover, the monosilane production | generation apparatus which concerns on this invention is provided with the pressure holding means which maintains the pressure in the reaction container when producing | generating monosilane from the said solid silicon at 0.133 kPa or more and 26.66 kPa or less.

  If it is said pressure range, a solid silicon can be etched efficiently by hydrogen plasma, and the production | generation efficiency of monosilane can be improved.

  In order to solve the above-mentioned problem, the monosilane production method according to the present invention is a catalytic reaction between hydrogen plasma produced in a hydrogen gas atmosphere in the presence of hydrogen plasma and solid silicon in the flow direction of hydrogen gas along the solid silicon. In the monosilane production method for producing monosilane, the hydrogen plasma region residence time of hydrogen gas passing through the hydrogen plasma region is controlled to be less than the time for which the produced monosilane undergoes a decomposition reaction in the hydrogen plasma region. It is a feature.

According to the invention, SiH ₄ is generated by contacting the generated solid silicon hydrogen plasma under a hydrogen atmosphere. When SiH ₄ is exposed to plasma, it decomposes and radicals are formed. By the reaction of these radicals, by-products such as particles can be generated. However, by controlling the residence time in the hydrogen plasma region to be less than the time during which SiH ₄ undergoes a decomposition reaction, the generation of the by-products can be suppressed and SiH ₄ can be produced with high efficiency.

  The monosilane generation apparatus according to the present invention is configured so that in the hydrogen gas flow direction along the solid silicon, the hydrogen plasma region residence time of the hydrogen gas passing through the hydrogen plasma region where the hydrogen plasma is present is determined. Thus, a control means is provided for controlling so that the time is less than the time for causing the decomposition reaction.

  In addition, the monosilane production method according to the present invention is characterized in that, in the flow direction of hydrogen gas along solid silicon, the hydrogen plasma region residence time of hydrogen gas passing through the hydrogen plasma region in which hydrogen plasma is present is determined. This is a method of controlling so that it takes less than the time for causing the decomposition reaction in the region.

Therefore, when generating SiH ₄ by utilizing the reaction between solid silicon and hydrogen plasma, the generation rate of by-products such as particles is greatly reduced, and solid silicon is efficiently converted to SiH ₄ gas. It is possible to provide an SiH ₄ generation device and a SiH ₄ generation method that can be used.

It is a cross-sectional view showing an embodiment of the SiH ₄ generating apparatus of the present invention. The operation of changing the length of the hydrogen plasma region in SiH ₄ generating apparatus of the present invention is a cross-sectional view illustrating. (A) in the production reaction of SiH _4, a diagram showing a reaction process when SiH ₄ gas residence time in the hydrogen plasma region is long, (b) if the short SiH ₄ gas residence time in the hydrogen plasma region It is a figure which shows the reaction process of. It is a block diagram which shows the relationship between the control part which concerns on this Embodiment, and another member. It is a sectional view showing another SiH ₄ generating apparatus according to this embodiment. In the present embodiment, a diagram showing the infrared absorption spectrum of the generated SiH ₄ gas. It is the graph shown about the correlation with the hydrogen flow volume and etching amount in this Embodiment. In this embodiment, it is a graph showing the correlation between the hydrogen flow rate and the SiH ₄ ratio. In this embodiment, it is a graph showing the correlation between the hydrogen plasma region the residence time and the SiH ₄ ratio of hydrogen gas. 6 is a graph showing a correlation between an electrode-silicon distance and an etching amount in specific example 2. 6 is a graph showing the correlation between the electrode-silicon distance and the SiH ₄ conversion rate in Example 2. (A) is a cross-sectional view showing the vicinity of a pipe-type electrode and solid silicon without an exterior member when hydrogen plasma is generated, and (b) is a pipe-type electrode with an exterior member provided on the electrode. It is sectional drawing which showed solid silicon vicinity. 10 is a graph showing a change in etching amount depending on the presence / absence of a plasma limiting component in Example 3. 10 is a graph showing a change in SiH ₄ conversion rate depending on the presence or absence of a plasma limiting component in Example 3.

An embodiment of the present invention will be described with reference to FIGS. 1 to 14 as follows. In the drawings of the present application, the same reference numerals denote the same or corresponding parts. The description of the configuration and operation of the SiH ₄ generator in this specification also serves as the description of the monosilane generation method according to the present invention.

Figure 1 shows a preferred example of SiH ₄ generating apparatus according to this embodiment is a sectional view showing a SiH ₄ generator (monosilane generator) 20. The SiH ₄ generation apparatus 20 is an apparatus that generates monosilane by causing a contact between hydrogen plasma generated in a hydrogen gas atmosphere and solid silicon. The SiH ₄ generator 20 has a reaction vessel 4 provided with an internal space serving as a reaction field for plasma processing the solid silicon 2. The electrode 1 is installed horizontally above the internal space of the reaction vessel 4. Below the electrode 1, the solid silicon 2 is arranged in parallel to face the electrode 1, and further, a substrate installation part (solid silicon installation part) 6 for installing the solid silicon 2 and a substrate installation part 6 are provided. A cooling mechanism (cooling means) 7 for cooling is provided.

A high frequency power source 5 for supplying power to the electrode 1 is provided on the upper surface of the reaction vessel 4, a gas introduction line 8 is provided on the left side, and a gas suction line 9 is provided on the right side. Although not shown, the SiH ₄ generation device 20 includes a control unit (control means) that controls various members.

  The electrode 1 operates by being supplied with electric power output from the high-frequency power source 5. The high frequency power supply 5 may be configured to apply pulsed high frequency power to the electrode 1. The electrode 1 is configured to be movable in the vertical direction. When the electrode 1 moves in the vertical direction, the distance from the lower solid silicon 2 can be appropriately changed.

  In addition, as shown in FIG. 2, the length of the electrode 1 at a portion facing the solid silicon 2 can be changed by moving the electrode 1. FIG. 2 is a cross-sectional view showing an operation for changing the length of the hydrogen plasma region 3. As shown on the left side of FIG. 2, the hydrogen plasma region 3 is a region where hydrogen plasma exists in (in contrast to) the flow direction of hydrogen gas along the solid silicon 2. As shown on the right side of FIG. 2, the length of the electrode facing the solid silicon 2 can be changed by sliding the electrode 1 in the lateral direction. Thereby, the length of the hydrogen plasma region 3 can be controlled. The operation of the electrode 1 and the amount of power of the high-frequency power source 5 are controlled by a control unit (not shown).

  The solid silicon 2 is placed on a substrate installation portion 6 provided horizontally with respect to the bottom surface of the reaction vessel 4. Further, a vacuum chuck (not shown) for adsorbing and fixing the solid silicon 2 placed on the substrate placement unit 6 is provided, and the movement of the substrate placement unit 6 places the solid silicon 2 being plasma processed. It is fixed so that it does not shift from the position. The board installation unit 6 is grounded.

  When etching the solid silicon 2 with hydrogen plasma, first, atomic hydrogen needs to be adsorbed on the surface of the solid silicon 2. Here, if the temperature of the solid silicon 2 becomes too high, the desorption of atomic hydrogen from the surface of the solid silicon 2 becomes remarkable. For this reason, from the viewpoint of increasing the etching efficiency, the temperature of the solid silicon 2 is preferably 300 ° C. or less.

  Furthermore, a cooling mechanism 7 for cooling the solid silicon 2 placed on the substrate installation unit 6 is provided inside the substrate installation unit 6. According to the cooling mechanism 7, when the solid silicon 2 is etched in the presence of hydrogen gas, the solid silicon 2 can be maintained at a low temperature. Since the etching rate increases as the temperature of the solid silicon 2 is lower, monosilane can be efficiently generated. It does not specifically limit as a refrigerant | coolant used with the cooling mechanism 7, Water, a well-known coolant, etc. can be used. When water is used as the refrigerant, the water temperature is preferably 5 ° C or higher and 20 ° C or lower.

  The gas introduction line 8 is connected to a gas supply source (not shown) so that hydrogen gas is supplied between the electrode 1 and the solid silicon 2 at an arbitrary flow rate. On the other hand, the gas suction line 9 is connected to a vacuum pump which is a pressure holding means (not shown), and is a region between the electrode 1 and the solid silicon 2, and in the flow direction of hydrogen gas along the solid silicon 2, It has a structure capable of sucking a gas such as silane and hydrogen gas that has passed through the hydrogen plasma region 3 where hydrogen plasma is present at an arbitrary suction flow rate. The vacuum pump also serves to adjust the pressure inside the reaction vessel 4 to a value suitable for the reaction conditions.

  In addition, the said pressure holding means should just be able to reduce and hold | maintain the internal pressure of the reaction container 4, and you may use apparatuses other than a vacuum pump. The gas supply source and vacuum pump (not shown) are connected to the control unit, and the hydrogen flow rate and the gas suction flow rate from the hydrogen plasma region are controlled by the control unit.

A particle filter 10 is provided in the gas suction line 9. The particle filter 10 has a structure capable of capturing particles, which are by-products generated as a by-product during the monosilane production process, and extracting only SiH ₄ . As the particle filter 10, a polymer filter or the like can be used. Although not shown, the line of the gas suction line 9 is further provided with a Fourier transform infrared spectrophotometer so that the generated monosilane can be analyzed.

An example of a method for generating SiH ₄ from solid silicon 2 and hydrogen gas using the SiH ₄ generator 20 will be described below. First, after the gas inside the reaction vessel 4 is sufficiently exhausted by a vacuum pump through the gas suction line 9, hydrogen gas is introduced into the reaction vessel 4 from the gas introduction line 8. Here, the supply of hydrogen gas and the suction of gas from the gas suction line 9 are performed simultaneously, thereby maintaining the pressure inside the reaction vessel 4 at a predetermined pressure.

  The predetermined pressure is not particularly limited as long as Si atoms of the solid silicon 2 can be etched by hydrogen plasma. However, a pressure of 1 Torr or more and 200 Torr or less (0.133 kPa or more and 26.666 kPa or less) is preferable because etching can be performed efficiently.

Thereafter, electric power is applied to the electrode 1 from a high frequency power source 5 provided outside the reaction vessel 4. When this high frequency power is applied to the electrode 1, an electric field is generated between the electrode 1 and the substrate installation portion 6. The electric field decomposes and excites the hydrogen gas supplied between the electrode 1 and the surface of the solid silicon 2 to form a hydrogen plasma between the electrode 1 and the surface of the solid silicon 2. The atomic hydrogen generated by the hydrogen plasma contacting the surface of the solid silicon 2 acts on the surface of the solid silicon 2 to etch Si atoms, thereby generating SiH ₄ gas.

Thereafter, the generated SiH ₄ gas is sucked to the gas suction line 9 side, passes through the particle filter 10, the byproduct sucked together with the SiH ₄ gas is removed, and only the SiH ₄ gas is collected and taken out. .

A process of generating the by-products such as particles will be described with reference to FIG. FIG. 3 is a diagram illustrating a reaction process in the formation reaction of SiH ₄ . First, a case where the residence time of SiH ₄ corresponding to FIG. 3A in the hydrogen plasma region 3 is long will be described. The residence time of SiH _{4 in} the hydrogen plasma region 3 is referred to as a hydrogen plasma region residence time (hereinafter abbreviated as “region residence time” as appropriate).

As described above, the hydrogen molecules entering the hydrogen plasma region 3 are decomposed into atomic hydrogen, and the atomic hydrogen reacts with Si atoms, thereby generating SiH ₄ .

Here, since the residence time of the SiH ₄ gas in the hydrogen plasma region 3 is long, the generated SiH ₄ becomes SiH or SiH _{2 due to} contact with atomic hydrogen or electrons in the hydrogen plasma while traveling through the hydrogen plasma region 3. It will be broken down into unstable short-lived radicals. In general, the short-lived radicals such as SiH and SiH ₂ are said to cause generation of higher-order silane and particles. That is, due to the reaction between the short-lived radicals, short-lived radicals, and Si atoms, the generated SiH ₄ is converted into higher order silane or particles instead of SiH ₄ when escaped from the hydrogen plasma region 3. Will be.

On the other hand, a case where the residence time of the SiH ₄ gas in the hydrogen plasma region 3 corresponding to FIG. As in the case of FIG. 1A, SiH ₄ is generated by the reaction between atomic hydrogen generated in the hydrogen plasma region 3 and Si atoms, but the residence time of SiH ₄ is short. In such a case, the generated SiH ₄ can escape from the hydrogen plasma region 3 before being decomposed into radicals. That is, it is possible to suppress the decomposition of SiH ₄ by controlling the region residence time to be less than the time at which SiH ₄ causes a decomposition reaction. Thus, it is possible to escape to leave a hydrogen plasma region 3 outside of SiH _4, it is possible to generate an SiH ₄ with high efficiency.

Thus, according to the SiH ₄ production | generation apparatus 20 which concerns on this invention, it is possible to obtain SiH ₄ only by solid silicon and hydrogen gas, and a by-product like SiCl ₄ generated at the time of the conventional SiH ₄ production | generation Therefore, the yield of SiH ₄ with respect to the raw material can be increased. In addition, since a large-scale apparatus and process for collecting SiCl ₄ and reprocessing it into SiHCl ₃ , know-how, and the like are not required, a great deal of cost and labor can be reduced. In addition, since it is not necessary to use chlorine, there is no need for countermeasures on the equipment against chlorine corrosion, and the environmental load can be reduced.

In the SiH ₄ generation apparatus 20 according to the present invention, the region residence time can be controlled by the control unit. FIG. 4 is a block diagram showing the relationship between the control unit 30 and other members. The control unit 30 included in the SiH ₄ generation device 20 is an interface type, and the control unit 30 is connected to the interface unit 40. The interface unit 40 receives a user operation input and transmits an instruction signal to the control unit 30, and includes a display unit 41 and an input unit 42.

  The display unit 41 is connected to the input unit 42 and displays the contents of the instruction signal transmitted to the control unit 30 and can be configured by a known liquid crystal display or the like. The input unit 42 transmits input data input to an input unit (not shown) provided in the interface unit 40 to the control unit 30. As said input means, it can comprise with an input key or a touch panel, for example. Note that the control unit 30 and the interface unit may not be directly connected, and may be configured to transmit and receive signals wirelessly.

  Based on the instruction signal transmitted from the input unit 42, the control unit 30 transmits a control signal to the electrode 1, the high frequency power source 5, the gas supply source 31, and the vacuum pump 32. Based on the control signal, the electrode 1, the high frequency power source 5, the gas supply source 31, and the vacuum pump 32 are controlled. The operation for controlling each member will be described below.

First, the control unit 30 can transmit a control signal to the electrode 1 to adjust the distance between the electrode 1 and the solid silicon 2. That is, the electrode 1 can be moved in the vertical direction with respect to the solid silicon 2. By extending the distance between the electrode 1 and the solid silicon 2, the hydrogen plasma region 3 can be expanded. On the other hand, the hydrogen plasma region 3 is reduced by shortening the distance between the electrode 1 and the solid silicon 2. As a result, the amount of energy received by the generated SiH ₄ can be increased or decreased.

According to the control unit 30, when a by-product is generated when generating SiH ₄ , the distance between the electrode 1 and the solid silicon 2 is shortened, thereby shortening the region residence time by increasing the flow rate of hydrogen gas. , The decomposition rate of SiH ₄ is suppressed, and the production rate of by-products is reduced. That is, the amount of energy received by the generated SiH ₄ can be controlled to be less than the amount by which SiH ₄ is decomposed. In other words, it can be expressed that the region residence time can be controlled to be less than the time during which SiH ₄ undergoes a decomposition reaction.

  Furthermore, the control unit 30 can transmit a control signal to the electrode 1 to adjust the electrode length of the electrode 1. By extending the electrode length of the electrode 1, the length of the hydrogen plasma region 3 with respect to the flow direction of the hydrogen gas along the solid silicon 2 can be extended. That is, the hydrogen plasma region 3 can be expanded. On the other hand, by shortening the electrode length of the electrode 1, the length of the hydrogen plasma region 3 with respect to the flow direction of the hydrogen gas along the solid silicon 2 can be shortened. That is, the hydrogen plasma region 3 can be reduced.

According to the control unit 30, when a by-product is generated when generating SiH ₄ , by shortening the electrode length of the electrode 1, the region residence time is shortened, and decomposition of SiH ₄ is suppressed. The production rate of by-products can be reduced. Thereby, similarly to the case where the distance between the electrode 1 and the solid silicon 2 is adjusted, the region residence time can be controlled to be less than the time during which the SiH ₄ undergoes the decomposition reaction.

  In addition, the control unit 30 can control (adjust) the high-frequency power for generating hydrogen plasma applied to the electrode 1 from the high-frequency power source 5 by transmitting a control signal to the high-frequency power source 5. When the power is increased or decreased, the power density in the hydrogen plasma region can be increased or decreased.

Therefore, according to the control unit 30, when a by-product is generated when generating SiH ₄ , the power density in the hydrogen plasma region 3 is reduced by reducing the power, and the decomposition rate of hydrogen molecules is reduced. As a result, the decomposition rate of SiH ₄ can be suppressed and the production rate of by-products can be reduced. That is, the region residence time can be controlled to be less than the time during which SiH ₄ undergoes a decomposition reaction. If the power density is excessively high, the decomposition reaction of SiH ₄ in the hydrogen plasma region 3 is promoted.

Furthermore, it is preferable to control the high frequency power supply 5 by the control unit 30 so that the power becomes pulsed high frequency power. By applying pulsed high-frequency power instead of continuously output normal power, it is possible to form a state in which hydrogen plasma is generated for a certain period and not generated for the next certain period. As a result, the generated SiH ₄ is hardly decomposed by the influence of hydrogen plasma, and the generation of by-products can be suppressed. Further, since the generated SiH ₄ is difficult to be decomposed, there is an advantage that the flow rate of hydrogen gas for escaping SiH ₄ from the hydrogen plasma region may be small.

  Further, the control unit 30 can send a control signal to the gas supply source 31 to increase or decrease the supply flow rate of the hydrogen gas supplied from the gas supply source 31. Thereby, the density | concentration of the hydrogen gas supplied via the gas introduction line 8 can be increased / decreased. When the concentration of the hydrogen gas that is converted into plasma in the hydrogen plasma region 3 is increased or decreased, the hydrogen plasma concentration is increased or decreased.

According to the control unit 30, when a by-product is generated when generating SiH ₄ , the flow rate of hydrogen gas passing through the hydrogen plasma region 3 can be increased by increasing the supply flow rate of hydrogen gas. it can. Thus, it is possible to reduce the area staying time, SiH ₄ is under conditions less likely to be degraded by the influence of hydrogen plasma, can be generated for SiH _4. In other words, the region residence time can be controlled to be less than the time at which SiH ₄ undergoes a decomposition reaction by reducing the generation rate of by-products by suppressing the decomposition of SiH ₄ and reducing the decomposition rate of SiH _4. .

Further, the control unit 30 can send a control signal to the vacuum pump (pressure holding means) 32 to adjust the suction flow rate of hydrogen gas by the vacuum pump 32. Thereby, the density | concentration of the hydrogen gas plasmified in the hydrogen plasma area | region 3 can be increased / decreased. Therefore, similarly to the case where the supply flow rate of hydrogen gas is adjusted by the gas supply source 31, the region residence time can be controlled to be less than the time during which the SiH ₄ undergoes a decomposition reaction.

As described above, the control unit 30 can control the electrode 1, the high-frequency power source 5, the gas supply source 31, and the vacuum pump 32, but among the electrode 1, the high-frequency power source 5, the gas supply source 31, and the vacuum pump 32. By controlling at least one, the region residence time can be controlled to be less than the time during which SiH ₄ undergoes a decomposition reaction. In other words, the distance between the electrode 1 and the solid silicon 2, the length of the hydrogen plasma region 3 with respect to the flow direction of hydrogen gas along the solid silicon, the hydrogen gas supply flow rate to the hydrogen plasma region 3, and the hydrogen from the hydrogen plasma region 3 By controlling at least one of the gas suction flow rates, the region residence time can be controlled to be less than the time during which SiH ₄ undergoes a decomposition reaction.

In the SiH ₄ generation device 20, the control unit 30 can easily control the residence time in the hydrogen plasma region by performing the above control. Of course, the control unit 30 may control all of the electrode 1, the high-frequency power source 5, the gas supply source 31, and the vacuum pump 32 so that the region residence time is less than the time during which the SiH ₄ undergoes a decomposition reaction.

The region residence time, flow rate of the hydrogen gas to be used (density), it is difficult to define unambiguously to be appropriately changed depending on the amount of power applied to the electrode 1, to suppress the decomposition of SiH _4, sub From the viewpoint of suppressing the generation of secondary products and improving the yield of SiH ₄ , it is generally preferably 20 μsec or less. Further, the region residence time is preferably 10 μsec or longer so that the amount of SiH ₄ produced does not decrease too much.

<Specific Example 1. Correlation between SiH ₄ conversion rate and plasma residence time of hydrogen gas>
Hereinafter, in the case where SiH ₄ is generated by the SiH ₄ generation device 21 of the present invention, an experiment for suppressing the generation of higher order silanes and particles polymerized by them and setting optimum conditions for generating SiH ₄ with high efficiency Therefore, the result will be described.

For the production confirmation SiH _4, and to find the optimal conditions for generating SiH ₄ at a high efficiency were SiH ₄ production experiments by hydrogen plasma etching of solid silicon 2 by SiH ₄ generating apparatus 21 shown in FIG. 5 .

As shown in FIG. 5, the SiH ₄ generation device 21 is provided with a high-frequency power source 5 that is a microwave power source, a waveguide 11, a microwave matching unit 12, and a movable short-circuited end 13. A pipe-type electrode (pipe electrode) 1 is provided so as to be orthogonal (perpendicular) to the solid silicon 2, and microwave power is supplied to the pipe-type electrode 1 via a waveguide 11 and a dielectric 14. Is supplied. According to the SiH ₄ generation device 21, SiH ₄ is generated by generating hydrogen plasma between the pipe-type electrode 1 and the solid silicon 2. A microwave with a frequency of 2.45 GHz was used for generating hydrogen plasma.

  The experimental conditions are as shown in Table 1. Note that 60 Torr is 7.998 kPa. During the experiment, hydrogen gas is continuously supplied from the pipe-type electrode 1 to the hydrogen plasma region 3 at the hydrogen supply flow rate shown in Table 1. Further, the atmospheric pressure is kept constant within the range shown in Table 1 by changing the exhaust speed of the hydrogen gas. Further, as shown in Table 1, the experiment was performed by changing the electrode outer diameter of the electrode 1 to 3.2 mm, 6.4 mm, and 12.7 mm. Moreover, electric power is set according to the electrode area so that the plasma state becomes equal, and it is set to 100 W (electrode outer diameter 3.2 mm), 200 W (electrode outer diameter 6.4 mm), and 400 W (electrode outer diameter 12.7 mm), respectively. Set. During the experiment, cooling water at 20 ° C. was continuously supplied to the cooling mechanism 7 to cool the solid silicon 2. In each case of an electrode outer diameter of 3.2 mm, an electrode outer diameter of 6.4 mm, and an electrode outer diameter of 12.7 mm, the hydrogen flow rate was set at 5 to 27.5 L / min.

For the measurement of the generation confirmation and SiH ₄ generated amount of SiH _4, using Fourier transform infrared spectroscopy (FTIR) 15. When SiH ₄ is analyzed by FTIR analysis, it is known that remarkable peaks are obtained in the vicinity of wave numbers 2189 cm ⁻¹ and 913 cm ⁻¹ , so generation of SiH ₄ is confirmed by FTIR analysis of the gas generated after etching. can do. Further, by preparing a calibration curve in advance using a mixed gas of SiH ₄ and H ₂ with known concentrations, it is possible to quantify the SiH ₄ concentration of the gas generated by etching, and the amount of SiH ₄ generated (in mol) ) Can also be calculated. Here, the ratio of the SiH ₄ generation amount (mol number) and the etching amount (mol number) obtained by FTIR analysis is defined as “SiH ₄ conversion rate (%)”. This value shows the ratio of the Si atoms converted into SiH ₄ out of the etched Si atoms.
SiH ₄ conversion rate (%) = SiH ₄ generation amount (mol number) / etching amount (mol number) × 100
An example of the FTIR spectrum of the gas generated by the etching is shown in FIG. FIG. 6 is a diagram showing an infrared absorption spectrum of the generated SiH ₄ gas in the present embodiment. As shown in the figure, since significant peaks are obtained in the vicinity of wave numbers 2189 cm ⁻¹ and 913 cm ⁻¹ , it can be seen that SiH ₄ is generated by etching. _{If Si} 2 _{H 6} is present also, but the significant peak is observed at the position of the wave number 843cm ^-1 is known, since the position of the wave number 843cm ^-1 is not observed a peak approximately SiH It can be seen that it is generated in the form of ₄ .

  Next, the graph of FIG. 7 shows the dependency of the etching amount on the hydrogen flow rate. FIG. 7 is a graph showing the correlation between each hydrogen flow rate (5 to 27.5 L / min.) And the etching amount under the conditions shown in Table 1. As can be seen from the figure, the etching amount tends to increase as the hydrogen flow rate increases. This is presumably because the absolute amount of hydrogen molecules increases as the hydrogen flow rate increases, and the number of atomic hydrogen contributing to etching increases. However, as can be seen from FIG. 7, the hydrogen flow rate has an optimum value with respect to a constant input power, and when the flow rate exceeds a certain flow rate, the power is insufficient and the etching amount is reduced.

The graph of FIG. 8 shows the hydrogen flow rate dependency of the SiH ₄ conversion rate. FIG. 8 is a graph showing the correlation between the hydrogen flow rate and the SiH ₄ conversion rate in the present embodiment. As can be seen from the figure, the result is that the SiH ₄ conversion rate increases as the hydrogen flow rate increases. For example, when the electrode outer diameter is 12.6 mm, the SiH ₄ conversion rate is as low as 20% at a flow rate of 5 L / min. This indicates that the ratio of the etched Si atoms that can be obtained as SiH ₄ is about 20%, and the remaining 80% is made into higher order silane or particles. On the other hand, at a flow rate of 25 L / min, the SiH ₄ conversion rate was as high as 90%, indicating that SiH ₄ could be generated with high efficiency.

As described above, it was obtained that the SiH ₄ conversion rate increased as the hydrogen flow rate increased in any of the electrodes. The present inventors considered that “flow rate” and “gas plasma residence time” that change with the hydrogen flow rate are important, not “hydrogen flow rate”. Therefore, the flow rate of hydrogen, the pressure, and the flow rate of the gas passing through the hydrogen plasma region 3 were calculated from the gap between the electrode 1 and the solid silicon 2. Then, the plasma residence time of the hydrogen gas is calculated from the calculated hydrogen flow velocity and the length (plasma length) of the hydrogen plasma region 3 that is the distance that the hydrogen gas passes along the solid silicon 2 in the hydrogen plasma region 3. Then, the horizontal axis of the graph of FIG. 8 was converted into the hydrogen plasma region residence time (region residence time).

As a result, it was found that there is a correlation as shown in FIG. 9 between the plasma residence time and the SiH ₄ conversion rate. FIG. 9 is a graph showing the correlation between the hydrogen gas region residence time and the SiH ₄ conversion rate in the present embodiment. From the figure, when the organizing SiH ₄ ratio in the region dwell time, even when the electrode shape is different, it can be seen that SiH ₄ ratio rides on the same line. From this result, it can be considered that the parameter for determining the SiH ₄ conversion rate is not “hydrogen flow rate” but “plasma residence time”.

As described above, when the plasma residence time is long, SiH ₄ generated by etching reacts again in the gas phase while passing through the hydrogen plasma, and higher silane and particles are formed. However, by shortening the region residence time, SiH ₄ was generated by escape to leave the plasma outside of the SiH ₄ before re reaction makes it possible to achieve high SiH ₄ ratio.

As can be seen from FIG. 9, the SiH ₄ conversion rate can be drastically increased by shortening the region residence time. Further, by setting the plasma residence time to about 20 μsec or less, the SiH ₄ conversion rate becomes 80% to 90%, and SiH ₄ can be generated with high efficiency. However, in this correlation study, changing the power according to the electrode area, approximately equal (power density 240 W / cm ² or more, 280 W / cm ² or less) power density to that, but if the power density is different, The plasma residence time required for high-efficiency generation of SiH ₄ is considered to shift, and it is considered that the plasma residence time needs to be shortened as the power density increases.

<Specific example 2. Improvement of SiH ₄ conversion rate by narrowing gap between electrode and Si>
As described above, it was shown that the SiH ₄ conversion rate can be increased by increasing the hydrogen flow rate and shortening the plasma residence time. However, the hydrogen gas passage cross-sectional area can be reduced by reducing the electrode-Si distance. Even if it is made smaller, the hydrogen gas flow rate rises and the region residence time becomes shorter. Thereby, it is considered that the SiH ₄ conversion rate is increased. Thus, it was confirmed whether the SiH ₄ conversion rate was increased even at the same hydrogen flow rate by reducing the electrode-Si distance.

Table 2 shows the experimental conditions. The hydrogen supply flow rate flow rate was fixed at 5 L / min, and the experiment was conducted in two cases where the distance between the electrode and Si was 0.6 mm and 0.2 mm, and the etching amount and SiH ₄ conversion rate were measured. FTIR was used for the SiH ₄ conversion rate measurement in the same manner as in Example 1 above.

10 and 11 show the dependency of the etching amount and SiH ₄ conversion rate on the distance between the electrode and Si. As can be seen from the figure, as the distance between the electrode and Si decreases, the etching amount itself hardly changes, but the SiH ₄ conversion rate increases. This is considered to be because the gas flow velocity increased due to the small gas passage cross-sectional area, and the region residence time was shortened.

From the above results, it can be said that the electrode-Si distance is important as one parameter for controlling the SiH ₄ conversion rate.

<Specific example 3. SiH ₄ ratio improvement by limiting the hydrogen plasma region 3>
Specific Example 3 describes an exterior member that limits the range of hydrogen plasma. FIG. 1 is a cross-sectional view showing the vicinity of a pipe-type electrode 1 and solid silicon 2 when hydrogen plasma is generated. FIG. 1A shows a state in which there is no exterior member, and FIG. It is in the state.

The SiH ₄ generator 21 includes a pipe-type electrode 1 as shown in FIG. In the case of the pipe-type electrode 1, the plasma is generated in a form having a spread above the electrode 1 as shown in FIG. 12A, and the hydrogen plasma region 3 is in the hydrogen gas flow direction along the solid silicon 2. In addition to the range, it extends to the outer periphery of the electrode 1.

Since the hydrogen gas flow velocity is large and the plasma residence time is short in the portion immediately below the electrode 1 where the surface of the electrode 1 and the solid silicon 2 are close to each other, the gas flow velocity is lowered in the portion where the plasma around the electrode spreads upward. It is considered that the plasma residence time becomes longer and the SiH ₄ conversion rate decreases. Therefore, the inventors have intensively studied and found a configuration in which an exterior member 16 for restricting the hydrogen plasma region 3 is provided around the electrode 1 as shown in FIG.

The exterior member 16 is provided on the outer periphery of the pipe-type electrode 1, and has a surface that is flush with the solid silicon 2 side end surface of the electrode 1 and parallel to the surface of the solid silicon 2. Since the SiH ₄ generation device 21 includes the exterior member 16, the inventor may be able to maintain a large flow rate until the hydrogen gas passes through the hydrogen plasma region 3 and improve the SiH ₄ conversion rate. Thought. Moreover, it is considered that the provision of the exterior member 16 restricts the space, thereby restricting the spread of hydrogen plasma, and further adds the effect of shortening the distance until the gas escapes the plasma.

Therefore, as shown in FIG. 12B, an experiment was performed by installing an exterior member 16 made of quartz around the electrode 1 to examine how the etching amount and the SiH ₄ conversion rate change. The material of the exterior member 16 is not particularly limited as long as the movement of the hydrogen plasma can be suppressed and deterioration due to the hydrogen plasma does not occur. When the exterior member 16 is a conductor such as a metal, an electric field is generated between the exterior member 16 and the solid silicon 2 and the plasma spreads. Therefore, the hydrogen plasma region 3 is the same as that in FIG. It becomes a state. For this reason, it is preferable that the material of the exterior member 16 is an insulator (dielectric). Specifically, quartz (SiO ₂ ), alumina (Al ₂ O ₃ ) used as a general ceramic, aluminum nitride (AlN), boron nitride (BN), and the like can be exemplified. Moreover, the thickness of the exterior member is not particularly limited, but may be, for example, 5 mm or more and 10 mm or less.

  The experimental conditions are as shown in Table 3.

FIGS. 13 and 14 show changes in the etching amount and SiH ₄ conversion rate depending on the presence or absence of the exterior member 16. The thickness of the exterior member 16 is 6 mm. As shown in FIG. 13, the etching amount hardly changes depending on the presence or absence of the exterior member 16 made of quartz. However, as shown in FIG. 14, it can be seen that the SiH ₄ conversion rate is greatly increased. This is because the space in which the hydrogen gas can move is limited by the exterior member 16, the gas flow rate until SiH ₄ escapes from the plasma increases, and the hydrogen plasma region 3 is limited. it is conceivable that.

From the above results, it can be said that “the electrode-Si distance in the plasma region”, “the gas flow rate in the plasma region”, and “the plasma length” are important as parameters for controlling SiH ₄ .

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the technical means disclosed in different embodiments can be appropriately combined. Such embodiments are also included in the technical scope of the present invention.

  According to the present invention, since monosilane gas can be efficiently produced, it is suitably used in the manufacturing process of electronic devices using silicon-based thin films using monosilane gas as a raw material, such as thin film transistors, LSIs, and solar cells.

DESCRIPTION OF SYMBOLS 1 Electrode 2 Solid silicon 3 Hydrogen plasma area | region 4 Reaction container 5 High frequency power supply 6 Board | substrate installation part (solid silicon installation part)
7 Cooling mechanism (cooling means)
8 Gas Introduction Line 9 Gas Suction Line 10 Particle Filter 11 Waveguide 12 Microwave Matching Device 13 Movable Short-Circuit End 14 Dielectric 15 Fourier Transform Infrared Spectrophotometer (FTIR)
16 exterior member 20.21 SiH ₄ generator (monosilane generator)
30 Control unit (control means)
32 Vacuum pump (pressure holding means)

Claims (8)

In a monosilane production apparatus that produces monosilane by contact reaction between hydrogen plasma produced in a hydrogen gas atmosphere and solid silicon,
In the hydrogen gas flow direction along the solid silicon, the hydrogen plasma region residence time of the hydrogen gas passing through the hydrogen plasma region where the hydrogen plasma exists is
A monosilane production apparatus characterized in that a control means is provided for controlling the produced monosilane so that it is less than a time for causing a decomposition reaction in the hydrogen plasma region. The hydrogen plasma is generated by applying power between the electrode and solid silicon,
The control means includes
Of the hydrogen gas supply flow rate to the hydrogen plasma region, the hydrogen gas suction flow rate from the hydrogen plasma region, the distance between the electrode and solid silicon, and the length of the hydrogen plasma region with respect to the flow direction of hydrogen gas along the solid silicon 2. The monosilane generation apparatus according to claim 1, wherein the residence time in the hydrogen plasma region is controlled by controlling at least one of the two. The control means includes
3. The hydrogen plasma region residence time of hydrogen gas passing through the hydrogen plasma region is controlled by controlling the high-frequency power for generating hydrogen plasma to be output to the electrode in a pulse form. The monosilane production | generation apparatus of description. The control means includes
The monosilane generation apparatus according to any one of claims 1 to 3, wherein the residence time in the hydrogen plasma region is controlled to be 20 µsec or less. A solid silicon installation part for installing the solid silicon is provided,
The monosilane production | generation apparatus of any one of Claims 1-4 with which the solid-silicon installation part is provided with the cooling means which cools solid silicon.   The monosilane according to any one of claims 1 to 5, further comprising pressure holding means for maintaining a pressure in a reaction vessel when producing monosilane from the solid silicon at 1 Torr or more and 200 Torr or less. Generator. The hydrogen plasma is generated by introducing hydrogen gas and applying power between a pipe electrode orthogonal to solid silicon and solid silicon,
The outer periphery of the said pipe electrode is provided with the exterior member which has the surface which is the same surface as the solid silicon side end surface of a pipe electrode, and is parallel to the surface of a solid silicon. The monosilane production | generation apparatus of Claim 1. In a monosilane production method for producing monosilane by contact reaction between hydrogen plasma produced in a hydrogen gas atmosphere and solid silicon,
In the hydrogen gas flow direction along the solid silicon, the hydrogen plasma region residence time of the hydrogen gas passing through the hydrogen plasma region where the hydrogen plasma is present is less than the time during which the generated monosilane undergoes a decomposition reaction in the hydrogen plasma region. The monosilane production method characterized by controlling as follows.

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