JP5357690B2 - Film forming method, solar cell manufacturing method, and catalytic CVD apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of operating a catalytic CVD device, along with a film forming method by a catalytic CVD method using the device and a solar cell manufacturing method, capable of prolonging the service life of a catalyst wire. <P>SOLUTION: Concerning a method of energizing the catalyst wire in forming a film using the catalytic CVD device, energization control to the catalyst wire is executed by constant current control when temperature rise is started and by constant power control in deposition, thereby preventing deterioration of the catalyst wire due to overheating to prolong the service life. Further, abnormal temperature rise of a substrate due to overheating of the catalyst wire in the deposition is avoided to prevent abnormal conditions of film quality. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a film forming method by a catalytic CVD method, a solar cell manufacturing method, and a catalytic CVD apparatus.

  In general, a CVD method (chemical vapor deposition method) is conventionally known as a method for forming a predetermined deposited film on a substrate when manufacturing various semiconductor devices such as solar cells. As one type of such a CVD method, a catalytic CVD method using catalytic chemical vapor deposition (catalytic chemical vapor deposition) has recently been studied (for example, Patent Document 1).

  In the catalytic CVD method, a raw material gas is supplied to a catalyst wire heated by energization, and the generated decomposition species is deposited on a substrate to form a film. In putting such a catalytic CVD method into practical use, it is a problem to extend the life of the catalyst wire. To solve this problem, a catalyst wire having a boride layer formed on the surface of a tantalum wire is used. It has been proposed to use it (for example, Patent Document 2). According to this catalyst wire, the life of the catalyst wire can be drastically improved as compared with the case of using tungsten or tantalum.

JP 2005-327995 A JP 2008-300793 A

  As described above, various studies have been made to extend the life of the catalyst wire itself. On the other hand, in other respects, almost no attempt has been made to extend the life of the catalyst wire.

  Therefore, the present invention has been made in view of the above-described situation, and by paying attention to the method of energizing the catalyst wire, a method for forming a film that can extend the life of the catalyst wire, a method for manufacturing a solar cell, and An object is to provide a catalytic CVD apparatus.

  The film forming method according to the present invention is a film forming method using a catalytic CVD apparatus equipped with a catalyst wire, and at the start of the temperature rise of the catalyst wire, energization of the catalyst wire is performed by constant current control, and the film is formed. The gist of the invention is that constant current control is applied to the catalyst wire.

  Thus, by controlling the current supply to the catalyst line at a constant current at the start of the temperature rise, the inclination of the temperature rise of the catalyst line at the initial stage of the temperature rise can be made smaller than in the case of constant power control. Therefore, since the temperature rise of the base material at the initial stage of temperature rise can be reduced, it becomes easy to control the temperature of the base material within a preferable range during film formation. Moreover, it is possible to suppress overshooting of the current flowing through the catalyst wire by performing constant current control of energization to the catalyst wire at the start of temperature increase. As a result, the film quality of the film to be formed can be improved and the life of the catalyst wire can be extended.

  In addition, by controlling constant power during film formation, overheating of the catalyst wire can be suppressed even when used for a long time compared to when constant current control is performed, and the temperature of the substrate can be easily controlled within a preferable temperature range. . Therefore, the film quality can be improved and the life of the catalyst wire can be extended.

  In the film forming method according to the present invention, the power source is set to constant current control so that the power value applied to the catalyst line by constant current control is equal to or less than the power value applied to the catalyst line by constant power control. A current value and a set power value for constant power control may be set.

  A film forming method according to the present invention is a film forming method using a catalytic CVD apparatus including a reaction chamber, a catalyst wire installed in the reaction chamber, and a power source for energizing the catalyst wire, the constant current control and The gist of the invention is to include a step of selecting one of the constant power controls and controlling the power source so that the catalyst wire can be energized.

  A method for manufacturing a solar cell according to the present invention is a method for manufacturing a solar cell using a catalytic CVD apparatus provided with a catalyst wire for decomposing a raw material gas. The gist is that the current control is performed, and that the catalyst wire is energized by constant power control during film formation.

  The catalytic CVD apparatus according to the present invention includes a reaction chamber, a catalyst wire installed in the reaction chamber, and a power source for energizing the catalyst wire, and the power source controls the energization of the catalyst wire by constant current control or constant power control. The gist of the present invention is to provide a selection means for selecting one of constant current control and constant power control.

  In the catalytic CVD apparatus according to the present invention, the power supply may control the power value supplied to the catalyst wire in accordance with the decomposition temperature of the supplied source gas in the constant power control.

  In the catalytic CVD apparatus according to the present invention, the power source has a constant current control setting current so that a power value applied to the catalyst line by the constant current control is equal to or less than a power value supplied to the catalyst line by the constant power control. A value and a set power value for constant power control may be set.

  The catalytic CVD apparatus according to the present invention determines whether or not the value of the current flowing through the catalyst line has reached a set current value, and whether or not the value of the power supplied to the catalyst line has reached the set power value. And the selecting means has a constant current when the determining means determines that the current value flowing through the catalyst line has reached the set current value or that the power value energized through the catalyst line has reached the set power value. Either one of control and constant power control may be selected.

  ADVANTAGE OF THE INVENTION According to this invention, while providing the lifetime of a catalyst wire, the formation method of a film | membrane and the manufacturing method of a solar cell which enable manufacture of the deposited film with favorable film quality, and the manufacture of a solar cell with the favorable characteristic are provided. be able to. In addition, it is possible to provide a catalytic CVD apparatus capable of extending the life of the catalyst wire and producing a deposited film with good film quality.

1 is a diagram illustrating a configuration of a catalytic CVD apparatus 100 according to an embodiment. It is a functional block diagram which shows the structure of the power supply 13 which concerns on embodiment. It is a graph which shows the relationship between the estimated electric power with which electricity is supplied to a catalyst line, and time. 4 is a graph showing a temperature transition of catalyst wires according to Example 1 and Comparative Example 1. 6 is a graph showing temperature transition of substrates according to Example 1 and Comparative Example 1. 6 is a diagram for explaining a film formation flow according to Example 2 and Comparative Example 2. FIG. It is a graph which shows transition of the resistance increase rate of the catalyst wire which concerns on Example 2 and Comparative Example 2. FIG.

  Hereinafter, a catalytic CVD apparatus according to an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

  However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Therefore, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

[Relationship between energization of catalyst wire and life of catalyst wire]
2. Description of the Related Art Conventionally, there are two known energization methods for controlling a power source for energizing a catalyst wire, constant current control using a constant current power source and constant power control using a constant voltage power source. However, as a result of extensive studies by the present inventors, it has become clear that these methods have the following problems.

  That is, the catalyst wire is elongated due to heating by energization, and the thickness gradually decreases as the energization time increases, and the resistance of the catalyst wire increases accordingly. Further, depending on the conditions such as the type of source gas, the resistance of the catalyst wire is increased due to silicidation. For this reason, if energization is continued with constant current control, the amount of heat generation increases with an increase in the integration time of the energization time, and the extension of the catalyst wire is accelerated, resulting in a decrease in the life of the catalyst wire. Moreover, since the temperature of the base material on which the film is to be deposited increases as the amount of generated heat increases in this way, the temperature of the base material at the time of film formation exceeds the preferred temperature range, and the film quality of the film deposited on the base material Reduce.

  On the other hand, when constant power control is used, control is performed so that the current decreases as the resistance increases, so that a problem such as constant current control does not occur. However, since the temperature of the catalyst wire is lower than that at the time of film formation and the resistance is low at the start of temperature increase for film formation, a larger current flows than at the time of film formation. Therefore, in the case of constant power control, since the current flowing through the catalyst line becomes large at the beginning of temperature rise, the inclination of the temperature rise of the catalyst line becomes larger than that in constant current control. Therefore, the temperature of the base material is likely to rise, and the film quality may be deteriorated. In addition, the current flowing through the catalyst wire may overshoot and excessive current may flow. In this case, the life of the catalyst wire may be reduced.

  The present invention aims at extending the life of the catalyst wire by focusing on the method of energizing the catalyst wire. Further, it is intended to improve the quality of the deposited film. Hereinafter, the description will be made with a focus on the method of energizing the catalyst wire.

[Configuration of catalytic CVD equipment]
Below, the structure of the catalytic CVD apparatus used for this embodiment is demonstrated, referring drawings. FIG. 1 is a diagram illustrating a configuration of the catalytic CVD apparatus 100.

  As shown in FIG. 1, the catalytic CVD apparatus 100 supplies a source gas to the catalyst wire 11 heated in the reaction chamber 10 by the catalytic CVD method, and deposits the generated decomposition species on the substrate 200. An apparatus for forming a film. The substrate 200 is a substrate on which the deposited film is formed by being held on the substrate tray 300.

  The catalytic CVD apparatus 100 includes a reaction chamber 10, a catalyst wire 11, a mounting portion 12, a power supply 13, a gas supply pipe 20, and a gas discharge pipe 30.

  The reaction chamber 10 is a vacuum container that accommodates the substrate tray 300.

  The catalyst wire 11 decomposes the source gas supplied into the reaction chamber 10 by being heated. Both ends of the catalyst wire 11 are attached to the attachment portion 12 and are arranged perpendicular to the bottom surface of the reaction chamber 10. The catalyst wire 11 is heated to a temperature at which the source gas can be decomposed (hereinafter referred to as “decomposition temperature”, for example, 1600 ° C. to 2000 ° C.) by energization. The source gas is decomposed by the catalyst wire 11, and when a decomposition species reaches the base material 200, a deposited film (for example, a semiconductor film or an SiN film) is formed on the base material 200.

  As a material of the catalyst wire 11, Ta, Mo, W, or the like can be used. Moreover, the catalyst wire 11 may have a heterogeneous layer on the surface. An example of this is a tantalum wire having a boride layer formed on the surface. The catalyst wire 11 has a diameter of 0.3 mm to 2.0 mm, preferably 0.5 mm to 1.0 mm.

  The attachment portion 12 is made of a conductive material. The attachment portion 12 is electrically connected to a power source 13 disposed outside the reaction chamber 10.

  The power source 13 energizes the catalyst wire 11 via the attachment portion 12. As the power source 13, a constant current / constant voltage power source capable of selecting constant current control and constant power control can be used. In the constant current control, the energization to the catalyst wire 11 is controlled with the set current value, and in the constant power control, the energization to the catalyst wire 11 is controlled with the set power value. Therefore, the power supply 13 includes a current setting unit that inputs a set current value for constant current control and a power setting unit that inputs a set power value for constant power control. The set current value functions as a current limiter value, and the set power value functions as a power limiter value. The configuration of the power supply 13 will be described later.

The gas supply pipe 20 is a flow path for supplying a source gas (for example, a mixture of SiH ₄ and H ₂ or SiH ₄ ) into the reaction chamber 10.

  The gas discharge pipe 30 is a flow path for discharging the source gas from the reaction chamber 10. The gas discharge pipe 30 can evacuate the reaction chamber 10 by discharging gas from the reaction chamber 10.

[Power supply configuration]
FIG. 2 is a functional block diagram showing the configuration of the power supply 13. As shown in FIG. 2, the power supply 13 includes a current sensor 131, a power sensor 132, and a control unit 133.

  The current sensor 131 detects the current flowing through the catalyst wire 11. The power sensor 132 detects the power supplied to the catalyst wire 11.

  The controller 133 has a predetermined temperature (hereinafter referred to as “standby temperature”) at which the temperature of the catalyst wire 11 is lower than the decomposition temperature of the source gas when no film is formed on the substrate 200. Thus, the current supply to the catalyst wire 11 is controlled. The control method at this time may be either constant current control or constant power control.

  When the temperature of the catalyst wire 11 is started for film formation on the substrate 200, the control unit 133 controls the energization of the catalyst wire 11 by constant current control to raise the temperature of the catalyst wire 11.

  Further, at the time of film formation on the substrate 200, the control unit 133 controls energization to the catalyst wire 11 by constant power control, and controls the temperature of the catalyst wire 11 to a predetermined reaction temperature.

  Specifically, when starting temperature rise, a set current value for constant current control is input using a current setting unit, and a set power value for constant power control is input using a power setting unit. .

  At this time, when it is assumed that the energization to the catalyst wire 11 is controlled only by the constant power control, the set current value is applied to the catalyst wire 11 at a predetermined temperature (standby temperature) immediately before the temperature rise starts. The current value is smaller than the current value assumed to flow. As described above, since the set current value also functions as a current limiter value, the catalyst wire 11 is controlled at a constant current with the set current value at the start of temperature rise. Note that the set current value is larger than the current value flowing through the catalyst wire 11 at the standby temperature during non-film formation.

  The set power value is smaller than the power value assumed to be energized to the catalyst wire 11 at the decomposition temperature of the raw material gas when it is assumed that the energization to the catalyst wire 11 is controlled only by constant current control. is there. As described above, the set power value also functions as a power limiter value. Therefore, when the temperature of the catalyst wire 11 is a predetermined reaction temperature, the catalyst wire 11 is controlled at a constant power with the set power value. The set power value is set to a power value that can raise the temperature of the catalyst wire 11 to the decomposition temperature of the source gas.

  Hereinafter, the relationship between the set current value and the set power value will be described using the power supplied to the catalyst wire 11 as an example.

FIG. 3 is a graph schematically showing the relationship between the power supplied to the catalyst wire 11 and time after the temperature rise start time (t = t ₀ ).

In FIG. 3, a solid line A is a transition of electric power expected to be energized to the catalyst line 11 when it is assumed that energization control to the catalyst line 11 is performed only by constant power control with a set power value. . In the figure, E _A is the set power value, the energization of the catalytic wire 11 is controlled by the set power value E _A.

A broken line B represents a transition of electric power expected to be energized to the catalyst line 11 when it is assumed that the energization control to the catalyst line 11 is performed only by the constant current control at the set current value. As shown in the figure, the set current value, the power that is expected to be energized in the catalyst line 11 at time t ₁ later, is set to be larger than the set power value E _A.

(1) Between time t _{0 and} t _{1 As} shown in FIG. 3, between time t ₀ (temperature rise start time) and t ₁ , as described above, the temperature of the catalyst wire 11 is low and the resistance is small. power is expected to be energized in the catalyst line 11 by the constant current control is less than the power that is expected to be energized in the catalyst line 11 at the set power value E _a for the constant power control. Thus, between times t ₀ ~t _1, energization of the catalytic wire 11 is constant-current controlled by the set current value. Therefore, at the start of the temperature increase, the energization to the catalyst wire 11 is controlled with a constant current.

(2) the time t ₁ after the time t ₁ after a setting power value E _A for the constant power control, the power is less than that expected to be energized in the catalyst line 11 by the constant current control. Therefore, after time t _1, power supply to the catalytic wire 11 is constant power control by setting the power value. Therefore, at the time of film formation, the energization to the catalyst wire 11 is controlled at a constant power.

  As described above, according to the present invention, the control unit 133 switches between constant current control and constant power control. That is, the control unit 133 can control the energization of the catalyst wire 11 by constant current control or constant power control, and functions as a “selection unit” that selects one of constant current control and constant power control.

Note that the time t ₁ at which switching between the constant current control and the constant power control is performed can be changed according to the set current value and the set power value, and the temperature of the catalyst wire 11 at the time t ₁ is decomposed at which decomposition of the raw material gas starts. The set current value and the set power value may be set so that the temperature is close to the start temperature. For example, switching between constant current control and constant power control may be performed immediately before the temperature of the catalyst wire 11 reaches the decomposition temperature of the raw material gas, or the temperature of the catalyst wire 11 reaches the decomposition temperature of the raw material gas. Immediately after that, switching between constant current control and constant power control may be performed. Therefore, energization to the catalyst wire 11 may be performed by constant current control in a part of the initial stage during film formation, or energization to the catalyst wire 11 may be performed by constant power control in a part immediately before the film formation. Also good. As described above, the power source is controlled by constant current control at the start of temperature rise and by constant power control at the time of film formation.

[Method of forming film]
Next, an example of a film forming method using the catalytic CVD apparatus 100 will be described with reference to the drawings.

In the following description, it is assumed that a preparation chamber and a take-out chamber (not shown) are connected to the catalytic CVD apparatus 100 via gate valves. The preparation chamber is a vacuum container for taking the substrate 200 from the atmosphere into the vacuum atmosphere. The take-out chamber is a vacuum container for taking out the substrate 200 from the vacuum atmosphere to the atmosphere. The charging chamber, the reaction chamber 10 and the take-out chamber are evacuated to a pressure of about 1 × 10 ⁻⁴ Pa or less except during film formation in a steady operation state.

(1) Loading of substrate First, the base material 200 is carried into the preparation chamber, and the pressure in the preparation chamber is exhausted to about 1 × 10 ⁻⁴ Pa or less.

  Next, the substrate 200 and the substrate tray 300 are heated using a heating mechanism such as a lamp heater or a sheath heater to remove moisture adsorbed on the substrate 200 and the substrate tray 300.

  Next, the substrate tray 300 holding the substrate 200 is carried into the reaction chamber 10 from the preparation chamber, and the substrate 200 is opposed to the catalyst wire 11.

  Note that the catalyst wire 11 in the reaction chamber 10 is energized in advance and is maintained at a predetermined temperature (standby temperature: for example, 500 ° C. to 700 ° C.). The control at this time may be constant current control or constant power control.

(2) Temperature rise start of catalyst wire Next, a set current value for constant current control (for example, 3.3 × 10 ⁷ A / m ^{2 to} 4.3 × 10 ⁷ A / m ² ) is supplied to the power source 13. In addition to setting, a set power value (for example, 1.8 kW / cm ^{3 to} 3.0 kW / cm ³ ) for constant power control is set. As described above, the set current value is a current value smaller than the current value assumed to flow through the catalyst wire 11 by constant power control when the temperature of the catalyst wire 11 is the standby temperature.

  The set power value is a power value smaller than the power value assumed to be energized to the catalyst wire 11 by constant current control when the temperature of the catalyst wire 11 is a predetermined reaction temperature.

  It should be noted that the set current value and the set power value are appropriately changed depending on the type of catalyst wire 11 and the type of source gas.

  By setting in this way, the control unit 133 allows the catalyst until the temperature of the catalyst wire 11 reaches a predetermined temperature near the decomposition start temperature of the raw material gas after a predetermined time has elapsed since the start of the temperature increase. The energization to the wire 11 is controlled by constant current control, and after reaching the predetermined temperature, the energization to the catalyst wire 11 is controlled by constant power control.

(3) Film formation After the temperature rise of the catalyst wire 11 is started, source gas is supplied into the reaction chamber 10 from the gas supply pipe 20, and the pressure in the reaction chamber 10 is set to a predetermined reaction pressure (for example, about 0.5 Pa to 10 Pa). ). The timing of supplying the source gas is not particularly limited, but when a source gas that causes deterioration (for example, silicidation) in the catalyst wire 11 is used, the temperature of the catalyst wire 11 is deteriorated by the source gas. It is preferable to start the supply of the raw material gas after reaching a temperature that is not performed. By continuing the supply of the source gas to the reaction chamber 10, film formation on the substrate 200 proceeds.

(4) Lowering the temperature of the catalyst wire and carrying out the base material Next, the supply of the raw material gas is stopped, the current supplied to the catalyst wire 11 is reduced, and the temperature of the catalyst wire 11 is lowered to the standby temperature. The energization control to the catalyst wire 11 at this time may be constant current control or constant power control.

  Next, the substrate 200 is taken out into the take-out chamber and taken out into the atmosphere.

[Action and effect]
As described above, in the film forming method according to the present embodiment, focusing on the method of energizing the catalyst wire 11, the energization control of the catalyst wire 11 is performed by constant current control at the start of temperature rise, and is constant during film formation. It is done with power control.

  Thus, by controlling the constant current of the catalyst wire 11 at the start of temperature increase, the inclination of the temperature increase of the catalyst wire 11 at the initial temperature increase can be reduced compared to the case of constant power control. Therefore, since the temperature rise of the base material 200 can be reduced, the film quality can be improved. Moreover, since it can suppress that the electric current which flows into the catalyst wire 11 overshoots, a catalyst wire can be extended in life.

  In addition, by controlling constant power during film formation, overheating of the catalyst wire 11 can be suppressed and the temperature of the substrate 200 can be easily controlled within a preferable temperature range as compared with the case where constant current control is continued. Therefore, the film quality can be improved and the life of the catalyst wire can be extended.

  Thus, according to the film forming method of the present embodiment, the life of the catalyst wire 11 can be extended, and a deposited film with good film quality can be manufactured.

  In addition, according to the catalytic CVD apparatus that enables control as in the forming method according to the present embodiment, it is possible to extend the life of the catalyst wire and to manufacture a deposited film with good film quality.

[Other embodiments]
Although the present invention has been described with reference to the above-described embodiments, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, although not specifically mentioned in the above-described embodiment, the catalytic CVD apparatus 100 can be used to form a semiconductor film such as an amorphous Si film or a film other than a semiconductor film such as a SiN film. Furthermore, the catalytic CVD apparatus 100 can also be used in a method for manufacturing a semiconductor device such as a solar cell including at least one of a semiconductor film and a film other than a semiconductor.

  In the above-described embodiment, the catalytic CVD apparatus 100 includes only one reaction chamber 10, but is not limited thereto. The catalytic CVD apparatus 100 may include a plurality of reaction chambers. As a result, the same kind of film or a different kind of film can be formed on the substrate 200 in an overlapping manner.

  In the above-described embodiment, the power source 13 uses a constant current / constant voltage power source capable of both constant current control and constant power control. However, the present invention is not limited to this. For example, as the power source 13, two power sources, that is, a constant current power source capable of constant current control and a constant voltage power source capable of constant power control may be used.

  Hereinafter, examples of the film forming method according to the present invention will be specifically described. However, the present invention is not limited to those shown in the following examples. It can be changed and implemented.

[Example 1]
First, a tantalum wire whose surface was borated was prepared as a catalyst wire.

  Next, the substrate was placed in the reaction chamber. Note that the catalyst wire in the reaction chamber is set to a standby temperature (500 ° C. to 700 ° C.) in advance.

Then, set the power of the set current value ^{3.3 × 10 7 A / m 2} ~4.3 × 10 7 A / m 2, a set power value 1.8kW ^/ cm ³ ~3.0kW ^/ cm 3 Then, the heating of the catalyst wire was started. At the start of the temperature increase, as described above, the energization control of the catalyst wire was performed by constant current control.

Next, supply of a raw material gas in which SiH ₄ (flow rate: 100 sccm to 1000 sccm) and H ₂ (flow rate: 100 sccm to 1000 sccm) were mixed as the raw material gas was started.

  Next, when the temperature of the catalyst line reached the decomposition temperature of the source gas (1600 ° C. to 2000 ° C.), the source gas was decomposed and the formation of an amorphous silicon film on the substrate was started. In addition, at the time of film-forming, as above-mentioned, the electricity supply control to a catalyst wire was performed by constant power control.

[Comparative Example 1]
In Comparative Example 1, the temperature of the catalyst wire was raised from the standby temperature to the decomposition temperature of the raw material gas only by constant power control. Other steps were the same as those in Example 1.

[Catalyst wire temperature transition and substrate temperature transition]
FIG. 4 is a graph showing the temperature transition of the catalyst wire. FIG. 5 is a graph showing the temperature transition of the substrate.

  As shown in FIGS. 4 and 5, in Comparative Example 1, the inclination of the temperature rise of the catalyst wire at the initial stage of temperature rise was larger than that in Example 1. In Comparative Example 1, the temperature increase of the substrate was larger than that in Example 1. This is because in Comparative Example 1, the energization control of the catalyst wire was performed only by constant power control, and thus the temperature of the catalyst wire was increased with a larger slope than in Example 1.

  From this result, when energizing the catalyst wire with constant power control, the inclination of the temperature rise of the catalyst wire is larger and the temperature rise of the substrate tends to be larger than when energizing the catalyst wire with constant current control. Was confirmed.

  Further, in Comparative Example 1, since the inclination of the temperature rise of the catalyst wire is large and the catalyst wire is easily overheated, it is considered that the life of the catalyst wire is shortened compared to Example 1.

  Further, in Example 1, it was confirmed that the temperature rise of the substrate was small and it was easy to control the substrate temperature within a preferable temperature range. For this reason, according to the present invention, it is considered that the quality of the film formed on the substrate can be improved.

[Example 2]
First, a tantalum wire having a borated surface as a catalyst wire was placed in the reaction chamber.

  Next, according to the flow shown in FIG. 6, the catalyst wire was repeatedly raised and lowered.

  Specifically, first, in the step of evacuating the reaction chamber in advance, the temperature of the catalyst wire was kept at the standby temperature by energizing the catalyst wire.

Then, set the power of the set current value ^{3.3 × 10 7 A / m 2} ~4.3 × 10 7 A / m 2, a set power value 1.8kW ^/ cm ³ ~3.0kW ^/ cm 3 Then, the heating of the catalyst wire was started. At the start of the temperature increase, as described above, the energization control of the catalyst wire was performed by constant current control.

  Next, supply of source gas was started. When the temperature of the catalyst wire reached the decomposition temperature of the source gas (1600 ° C. to 2000 ° C.), decomposition of the source gas was started. The energization control of the catalyst wire at this time was performed by constant power control.

  Next, after the raw material gas was decomposed for a predetermined time, the supply of the raw material gas was stopped, the exhaust of the reaction chamber was started, and the temperature of the catalyst wire was started to be lowered. The current control of the catalyst wire during the temperature drop was performed by constant current control. As a result, the temperature of the catalyst wire was lowered to the standby temperature.

  The above steps were repeated until the resistance increase rate of the catalyst wire reached 7.0%.

  The resistance increase rate of the catalyst wire substantially corresponds to the extension of the catalyst wire or silicidation, and can be used as a guide for evaluating the life of the catalyst wire.

[Comparative Example 2]
In Comparative Example 2, energization control to the catalyst wire was performed only by constant current control. And it carried out repeatedly until the resistance increase rate of the catalyst line reached 7.0% similarly to Example 2.

[Changes in resistance increase rate of catalyst wires]
FIG. 7 is a graph showing changes in the resistance increase rate of the catalyst wires according to Example 2 and Comparative Example 2. The resistance increase rate in FIG. 7 was calculated based on the resistance value of the catalyst wire obtained from the monitor value of the power and current supplied to the catalyst wire. Moreover, the high-temperature energization integration time in FIG. 7 is the sum of the time during which the catalyst wire is held at the decomposition temperature (1600 ° C. to 2000 ° C.) of the raw material gas.

  As shown in FIG. 7, in Comparative Example 2, the rate of increase in the resistance of the catalyst wire increased in a shorter time than in Example 2. This is because in Comparative Example 2, since the catalyst wire was held at a high temperature by constant current control, the temperature of the catalyst wire was excessively increased as the thickness of the catalyst wire was reduced.

  On the other hand, in Example 2, since the catalyst wire was kept at a high temperature by constant power control, it was possible to prevent the catalyst wire from being excessively heated even when the thickness of the catalyst wire was reduced.

DESCRIPTION OF SYMBOLS 10 ... Reaction chamber 11 ... Catalyst wire 12 ... Attachment part 13 ... Power supply 20 ... Gas supply pipe 30 ... Gas discharge pipe 100 ... Catalytic CVD apparatus 131 ... Current sensor 132 ... Electric power sensor 133 ... Control part 200 ... Base material 300 ... Base material tray

Claims (8)

A method of forming a film using a catalytic CVD apparatus provided with a catalyst wire,
At the start of raising the temperature of the catalyst wire, energization of the catalyst wire is performed with constant current control,
A method for forming a film, characterized in that energization of the catalyst wire is performed with constant power control during film formation. The power source for energizing the catalyst line is configured to control the constant current control so that the power value energized to the catalyst line by the constant current control is equal to or less than the power value energized to the catalyst line by the constant power control. The film forming method according to claim 1, wherein a set current value and a set power value for the constant power control are set. A method for forming a film using a catalytic CVD apparatus comprising a reaction chamber, a catalyst wire installed in the reaction chamber, and a power source for energizing the catalyst wire,
A method of forming a film, comprising: selecting either constant current control or constant power control and controlling the power source so that the catalyst wire can be energized. A method for producing a solar cell using a catalytic CVD apparatus comprising a catalyst wire for decomposing a raw material gas,
At the start of raising the temperature of the catalyst wire, energization of the catalyst wire is performed with constant current control,
A method for manufacturing a solar cell, wherein energization of the catalyst wire is performed by constant power control during film formation. A reaction chamber;
A catalyst wire installed in the reaction chamber;
A power source for energizing the catalyst wire,
The power source is capable of controlling energization of the catalyst wire by constant current control or constant power control, and includes a selection unit that selects either the constant current control or the constant power control. Catalytic CVD equipment. 6. The catalytic CVD apparatus according to claim 5, wherein the power source controls a power value supplied to the catalyst wire in accordance with a decomposition temperature of the supplied raw material gas in the constant power control. The power source has a set current value in the constant current control and the power value that is applied to the catalyst line by the constant current control is equal to or less than a power value that is supplied to the catalyst line by the constant power control. The catalytic CVD apparatus according to claim 5 or 6, wherein a set power value for constant power control is set. A judgment means for judging whether or not a current value flowing through the catalyst line has reached the set current value, and whether or not a power value energized through the catalyst line has reached the set power value;
The selection means, when it is determined by the determination means that the current value flowing through the catalyst line has reached the set current value, or the power value energized to the catalyst line has reached the set power value, The catalytic CVD apparatus according to claim 7, wherein one of the constant current control and the constant power control is selected.

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