JP2012049472A - Amorphous carbon and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide amorphous carbon with low defect density, and a method of manufacturing the same.SOLUTION: The amorphous carbon is fluorinated amorphous carbon to which a small number of fluorine atoms are introduced, with fluorine concentration of 5×10to 3%(atm). Consequently, the number of defects in the amorphous carbon can be reduced, and the amorphous carbon with low defect density can be realized.

Description

  The present invention relates to amorphous carbon and a method for producing the same.

  Conventionally, as amorphous carbon, what is used for a photoelectric element as described, for example in Unexamined-Japanese-Patent No. 2003-209270 is known. This amorphous carbon is formed by changing the structure of the nanocarbon layer by irradiating the outermost surface of the nanocarbon molecular layer with laser light.

JP 2003-209270 A

  By the way, there are two types of carbon bonding forms, sp2 bonding and sp3 bonding, but amorphous carbon has a structure with a mixture of sp2 bonding and sp3 bonding, so the structure is complicated and defects such as dangling bonds are present. Density becomes high. The amorphous carbon layer of the photoelectric element described in Patent Document 1 above forms a p-type semiconductor layer. For this reason, since the defect density is high, the defect functions as a carrier recombination center. There is a tendency to recombine. When the carriers are recombined, there is a problem that, for example, it is difficult to take out current for use as a solar cell, and power generation efficiency is lowered.

  Accordingly, the present invention has been made to solve such technical problems, and an object thereof is to provide amorphous carbon having a low defect density and a method for producing the same.

  As a result of intensive studies to achieve the above object, the present inventors have found that amorphous carbon having a low defect density can be obtained by defining a fluorine concentration that satisfies a predetermined condition, and have reached the present invention.

That is, the amorphous carbon according to the present invention is characterized in that the fluorine concentration is 5 × 10 ^{−5 to} 3% (atm).

  According to the present invention, by containing highly reactive fluorine, fluorine selectively binds to dangling bonds that are defective portions of amorphous carbon, and as a result, dangling bonds are passivated (protected). Thereby, the number of defects can be reduced, and amorphous carbon with a low defect density can be realized.

In the amorphous carbon according to the present invention, the fluorine concentration is preferably 5 × 10 ^{−5 to} 0.66% (atm).

  According to the present invention, amorphous carbon having a lower defect density can be realized.

  In the amorphous carbon according to the present invention, the fluorine concentration is preferably 0.1 to 0.66% (atm).

  According to the present invention, it is possible to realize amorphous carbon having an even lower defect density.

  Moreover, it is preferable that the amorphous carbon which concerns on this invention is used as a photoelectric element of a solar cell.

  According to the present invention, amorphous carbon having a low defect density is used as a photoelectric element of a solar cell, so that the properties as a semiconductor (mobility, etc.) can be improved, current can be easily taken out in the solar cell, and power generation efficiency Is improved.

  An amorphous carbon manufacturing method according to the present invention includes a source gas supply step of supplying a source gas containing fluorine and argon into the chamber, a plasma generation step of generating plasma of the source gas in the chamber, and a substrate in the chamber by the plasma And a forming step of forming amorphous carbon thereon.

  According to the present invention, by supplying argon which is easy to generate plasma simultaneously with fluorine, the utilization rate of fluorine is improved, and amorphous carbon having a low defect density can be manufactured.

In the method for producing amorphous carbon according to the present invention, fluorine in the raw material gas is preferably supplied as fluorine (F ₂ ) gas.

According to the present invention, by supplying fluorine as fluorine (F ₂ ) gas having a low binding energy, the supply amount of atomic fluorine (F) is increased, and defects can be efficiently reduced.

Moreover, the amorphous carbon manufacturing method according to the present invention preferably includes a fluorine treatment step in which the amorphous carbon formed in the forming step is exposed to fluorine (F ₂ ) gas.

  According to the present invention, amorphous carbon having a lower defect density can be produced.

  According to the present invention, amorphous carbon having a low defect density and a method for producing the same can be provided.

1 is a schematic configuration diagram of an apparatus applied to an amorphous carbon production method according to an embodiment of the present invention. It is a table | surface which shows the manufacturing conditions of the amorphous carbon in the Example of this invention. It is a figure which shows the defect density of the amorphous carbon at the time of changing the temperature of a board | substrate on the conditions of Example 3 in FIG. It is a figure which shows the relationship between the fluorine density | concentration in amorphous carbon, and a defect density.

  Embodiments of amorphous carbon and a method for producing the same according to the present invention will be described below in detail with reference to the accompanying drawings.

The amorphous carbon according to the present embodiment is a carbon semiconductor that can be used as a photoelectric element of a solar cell. This amorphous carbon has a fluorine concentration of 5 × 10 ^{−5 to} 3% (atm). That is, this amorphous carbon is fluorinated amorphous carbon into which a small amount of fluorine atoms is introduced. The amorphous carbon has a hydrogen concentration of about 15 to 30% (atm) and contains a doping element. This amorphous carbon has, for example, carbon as a main component, and has a configuration in which two types of bond forms of sp2 bond and sp3 bond are mixed as carbon bond forms.

The content concentration of fluorine, which is a component of this amorphous carbon, is 5 × 10 ^{−5 to} 3% (atm). The fluorine concentration is more preferably 5 × 10 ⁻⁵ to 1% (atm), still more preferably 5 × 10 ^{−5 to} 0.66% (atm), and 0.1 to 0. It is still more preferable that it is 66% (atm), and it is especially preferable that it is 0.2 to 0.5% (atm). By setting such a fluorine concentration, fluorine is selectively bonded to dangling bonds that are defective portions of amorphous carbon, and as a result, dangling bonds are passivated (protected). That is, dangling bonds are terminated with fluorine. Thereby, the number of defects in the amorphous carbon can be reduced, and amorphous carbon with a low defect density can be realized. This fluorine passivation is more effective than hydrogen passivation.

  FIG. 1 is a side sectional view showing a configuration of a plasma CVD (Chemical Vapor Deposition) apparatus 10 which is an apparatus applied to the production of amorphous carbon according to the present embodiment. As shown in FIG. 1, the plasma CVD apparatus 10 includes a chamber 11, a source gas source 12, a waveguide 14, and a microwave generator 15.

  The chamber 11 is an airtight container for generating the plasma P of the source gas G. The chamber 11 is connected to the source gas source 12 via a pipe 22. A source gas source 12 supplies a source gas G to the chamber 11. The source gas source 12 and the pipe 22 function as a source gas supply unit.

  An exhaust unit 13 including an exhaust pump is provided at the discharge port 19 of the chamber 11. Prior to growing the amorphous carbon film, the exhaust means 13 depressurizes the inside of the chamber 11 by evacuation. A substrate B for growing amorphous carbon C is accommodated in the chamber 11. A substrate stage 18 for supporting the substrate B is provided in the chamber 11. For the substrate B, a substrate temperature control unit (not shown) for controlling the temperature of the substrate B is provided. The substrate B is controlled to have a predetermined temperature by the substrate temperature control unit. The temperature of the substrate B (hereinafter referred to as “substrate temperature”) is preferably 250 to 500 ° C., more preferably 300 to 400 ° C., and still more preferably 360 to 390 ° C.

When the substrate temperature is increased, so-called migration is promoted and defects are reduced. On the other hand, by increasing the temperature, defects increase due to hydrogen desorption in carbon. By controlling the substrate temperature by the substrate temperature control unit so as to be within the above range, the defect reduction due to migration and the defect increase due to hydrogen desorption are balanced, and as a result, the defect density can be reduced. Further, by increasing the substrate temperature, fluorine (F ₂ ) gas (details will be described later) as a fluorine-added gas can be converted into atomic fluorine (F) by thermal decomposition, and the substrate stage 18 and the substrate B The atomic fluorine (F) present in the vicinity can be used for etching removal of silicon oxide (SiO ₂ ) and silicon nitride on the silicon substrate B.

  The microwave generation unit 15 outputs the microwave W for converting the raw material gas G introduced into the chamber 11 into plasma through the waveguide 14 to the chamber 11 and irradiates the raw material gas G. The microwave generation unit 15 generates, for example, a microwave W having an output of 600 to 1400 [W] and a frequency of 2.45 GHz by a magnetron or the like. The microwave W generated by the microwave generator 15 has a pulsed frequency, and its output, frequency, and duty ratio are controlled to predetermined values. By controlling the frequency and duty ratio of the microwave, the state of the plasma P can be greatly changed, so that the physical properties of the amorphous carbon can be easily controlled.

  The waveguide 14 guides the microwave W output from the microwave generator 15 and provides it to the interior of the chamber 11. The waveguide 14 is provided on the chamber 11 via a quartz window 16. A slot antenna 17 is provided on the surface of the waveguide 14 facing the chamber 11, and the microwave W is irradiated to the source gas G inside the chamber 11 through the slot antenna 17. A cooling fan 20 for cooling the waveguide 14 is installed on the waveguide 14. The quartz window 16 forms a surface on which the plasma P is generated, and corresponds to a plasma P generation unit.

  The source gas source 12 supplies a source gas G for growing amorphous carbon C to the chamber 11. The source gas G includes a material gas containing carbon atoms, a dopant gas containing a doping element (dopant) as an impurity element, a carrier gas, and a fluorine-added gas.

More specifically, the source gas source 12 includes at least one of ethylene (C ₂ H ₄ ) and acetylene (C ₂ H ₂ ) as a material gas source. As the material gas source, acetylene (C ₂ H ₂ ) is preferably used rather than ethylene (C ₂ H ₄ ). By using a hydrocarbon having a low hydrogen content, such as acetylene, as the carbon source of amorphous carbon, the etching action by hydrogen radicals is suppressed, so that the defect density of amorphous carbon can be reduced. The etching action by the hydrogen radical means a defect generating action due to collision of high energy particles.

The source gas source 12 includes, for example, trimethylboron (B (CH ₃ ) ₃ ) or nitrogen (N ₂ ) as a dopant gas source. In FIG. 1, illustration of these dopant gas sources is omitted.

  Trimethylboron is a dopant gas for allowing amorphous carbon to contain boron as a doping element. By adding trimethylboron, amorphous carbon containing boron can be produced. According to amorphous carbon containing boron, p-type amorphous carbon exhibiting physical properties of a p-type semiconductor can be realized on condition that a predetermined hydrogen concentration is satisfied.

Nitrogen (N ₂ ) is a dopant gas for causing amorphous carbon to contain nitrogen (N) as a doping element. By adding nitrogen (N ₂ ), amorphous carbon containing nitrogen (N) can be produced. According to amorphous carbon containing nitrogen (N), n-type amorphous carbon exhibiting physical properties of an n-type semiconductor can be realized on condition that a predetermined hydrogen concentration is satisfied.

The source gas source 12 includes an inert gas source such as argon (Ar) as a carrier gas source. Further, the source gas source 12 includes a mixed gas of fluorine (F ₂ ) and argon (Ar) as a fluorine-added gas source. This mixed gas is, for example, a gas obtained by diluting fluorine (F ₂ ) with argon (Ar) so that the volume ratio of fluorine (F ₂ ): argon (Ar) is 5:95. This volume ratio is preferably in the range of 0.1: 99.9 to 10:90. In the following description, a mixed gas of fluorine (F ₂ ) and argon (Ar) is referred to as diluted fluorine.

The fluorine-added gas (diluted fluorine) is also used as a fluorine treatment gas source for exposing amorphous carbon after film formation to fluorine (F ₂ ). The source gas source 12 includes a mixed gas of fluorine (F ₂ ) and argon (Ar), which has a different volume ratio of fluorine (F ₂ ): argon (Ar) from diluted fluorine, as a fluorine processing gas source. Alternatively, argon (Ar) as a carrier gas and diluted fluorine may be simultaneously supplied to be used as a fluorine processing gas source.

  This source gas source 12 is connected to the chamber 11 via a mass flow controller (MFC: Mass Flow Controller) (not shown) that adjusts each gas flow rate, and each source gas is mixed after passing through the mass flow controller. The gas G (or fluorine processing gas) is supplied to the chamber 11.

  In the plasma CVD apparatus 10 having the above-described configuration, the substrate B in the chamber 11 is provided at a predetermined distance d from the quartz window 16 that is a plasma P generation unit. In other words, the distance from the plasma P generator 16 to the substrate B is the distance d. The distance d is configured to be variably set by changing the arrangement position of the substrate B. In the following description, the distance d from the plasma P generator 16 to the substrate B is referred to as a substrate distance.

  The substrate distance d is preferably 0.7 to 5 cm, and more preferably 1 to 3 cm. In other words, the substrate B is preferably provided in the vicinity of or in the existence region of the plasma P. When the substrate distance is shortened, the effect of etching defects caused by plasma P is enhanced and the etching of carbon (carbon) itself is also increased. By disposing the substrate B so that the substrate distance d is within the above range, the etching of carbon itself can be suppressed while enhancing the etching effect of defects.

  Next, the operation of the amorphous carbon production apparatus and the amorphous carbon production method according to this embodiment will be described.

  In FIG. 1, first, after the substrate B is set on the substrate stage 18 of the chamber 11, the inside of the chamber 11 is decompressed. A source gas G containing a source gas such as acetylene, a dopant gas such as trimethylboron or nitrogen, a carrier gas such as argon, and a fluorine-added gas such as diluted fluorine is supplied into the chamber 11 from the source gas source 12. Supply (raw material gas supply process). At this time, the supply flow rate of each source gas to the chamber 11 is precisely controlled by the mass flow controller. Here, argon and fluorine are supplied simultaneously. In addition, while supplying the source gas G into the chamber 11, the microwave W is output from the microwave generator 15, and the source gas G in the chamber 11 is irradiated with the microwave W.

Inside the chamber 11, surface wave plasma P is generated by the microwave W irradiated from the microwave generation unit 15 through the waveguide 14 (plasma generation step). As a result, the source gas G changes to radicals containing carbon, moves to the surface of the substrate B, and is deposited. Here, argon (Ar) supplied simultaneously with fluorine (F ₂ ) is turned into plasma and becomes argon plasma, and atomic fluorine (F) is efficiently generated. At this time, the temperature of the substrate B is controlled to be a predetermined temperature by the substrate temperature control unit.

  Then, plasma P is deposited on the substrate B to form amorphous carbon C (film formation), and amorphous carbon C can be generated (forming process).

Further, after the amorphous carbon C is formed, the supply of the raw material gas G and the output of the microwave W are stopped, and diluted fluorine as a fluorine processing gas is supplied into the chamber 11 for a predetermined time (fluorine processing step). As a result, the amorphous carbon C is exposed to F ₂ gas, and fluorine treatment is performed.

  According to the amorphous carbon C according to the present embodiment described above, amorphous carbon having a low defect density can be realized.

  Further, by using amorphous carbon C having a low defect density as a photoelectric element of a solar cell, it is possible to improve the properties (mobility, etc.) as a semiconductor, and it is easy to take out current in the solar cell, thereby improving the power generation efficiency. Figured.

  In addition, according to the amorphous carbon manufacturing method according to the present embodiment, by supplying argon that easily generates plasma P together with fluorine, the utilization rate of fluorine is improved, and amorphous carbon C having a low defect density can be manufactured. Become.

Further, by supplying fluorine as F ₂ gas having low binding energy, the supply amount of atomic fluorine (F) increases, and defects can be efficiently reduced.

  Furthermore, since it becomes easy to generate atomic fluorine (F) by increasing the substrate temperature, defects can be reduced by thermal decomposition at a low temperature. In this case, a plasma generation device such as a microwave can be dispensed with.

The amorphous carbon manufacturing apparatus and manufacturing method according to the present invention have been described above. However, the amorphous carbon manufacturing apparatus and manufacturing method according to the present invention are not limited to the above-described embodiments, and the gist described in each claim. The above embodiment may be modified as long as it is not changed. For example, although the case where fluorine (F ₂ ) gas is used as the fluorine-added gas has been described in the above embodiment, other gas containing fluorine may be used. In that case, a gas having a low binding energy, that is, a gas having a binding energy equivalent to or lower than that of other raw material gases is preferable. When carbon tetrafluoride (CF ₄ ) gas having a high binding energy is used, a preferable defect reduction effect cannot be obtained. Further, the plasma CVD apparatus 10 may be provided with a bias power supply for applying a voltage between the plasma P and the substrate B.

  Moreover, in the said embodiment, although the amorphous carbon manufactured by plasma CVD method and its manufacturing method were demonstrated, the amorphous carbon which concerns on this invention may be manufactured by PVD (Physical Vapor Deposition) method. .

EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all. FIG. 2 is a table showing the production conditions of amorphous carbon in this example. The flow rate shown in the “F ₂ ” column in FIG. 2 is a flow rate of diluted fluorine, that is, a flow rate containing argon for dilution.

  As shown in FIG. 2, amorphous carbon was manufactured with the manufacturing apparatus and manufacturing method which concern on the said embodiment. However, unless otherwise specified, the fluorine treatment after the amorphous carbon C film formation in the above manufacturing method is not performed.

Example 1
In Example 1, the supply flow rates of the source gases were 180 sccm, 50 sccm, and 20 sccm for argon, acetylene, and diluted fluorine, respectively. As microwave conditions, the output was 800 W, the operating frequency was 500 Hz, and the duty ratio was 30% (on). Furthermore, the pressure in the chamber 11 was 50 Pa, the substrate temperature was 25 ° C., the substrate distance was 10 cm, and the deposition time was 30 min. Here, the dopant gas is not added, and the reason why the substrate temperature and the substrate distance are not within the ranges preferred in the above embodiment is to investigate the influence of the presence or absence of diluted fluorine on the defect density of amorphous carbon. .

As a result of producing amorphous carbon under the above conditions, as shown in Table 1, amorphous carbon having a defect density of 9.38 × 10 ¹⁹ cm ⁻³ was obtained.

(Comparative Example 1)
On the other hand, as Comparative Example 1, in the amorphous carbon produced without supplying diluted fluorine under the conditions of Example 1, the defect density was 2.16 × 10 ²⁰ cm ⁻³ as shown in Table 1.

From this Example and Comparative Example, it was confirmed that when diluted fluorine was added, amorphous carbon having a lower defect density was obtained than when not added. From the results of molecular simulation, it was confirmed that the defect density could be further reduced to 1 × 10 ¹⁶ cm ⁻³ by optimizing the fluorine concentration. From this result, it is considered that a defect density comparable to amorphous silicon (a-Si) can be realized even in amorphous carbon.

(Example 1 ')
Further, in addition to the raw material gas of Example 1, each of the amorphous carbon films formed by supplying trimethylboron at a flow rate of 30 sccm or nitrogen at a flow rate of 10 sccm was subjected to fluorine treatment. In the amorphous carbon film formation, the supply flow rate of argon was set to 200 sccm, and other conditions were the same as those in Example 1. In the subsequent fluorine treatment, argon is supplied at 200 sccm, diluted fluorine with a volume ratio of fluorine (F ₂ ): argon (Ar) of 0.5: 95.5 is supplied at 20 sccm, and the exposure time is 180 Second or 10 seconds. The substrate temperature was 25 ° C.

As a result of fluorine treatment of amorphous carbon under the above conditions, when trimethylboron (boron) was added, the defect density was 1.8 × by fluorine treatment with an exposure time of 180 seconds and 10 seconds, as shown in Table 2. An amorphous carbon of 10 ¹⁸ cm ⁻³ and 1.4 × 10 ¹⁸ cm ⁻³ was obtained. In addition, when nitrogen is added, amorphous carbon having a defect density of 1.5 × 10 ¹⁸ cm ⁻³ and 8.0 × 10 ¹⁷ cm ⁻³ is obtained by fluorine treatment with an exposure time of 180 seconds and 10 seconds, respectively. It was.

(Comparative Example 1 ')
On the other hand, when the fluorine treatment was not performed in Example 1 ′, as shown in Table 2, the amorphous carbon to which trimethylboron (boron) was added had a defect density of 2.6 × 10 ¹⁸ cm ⁻³ and nitrogen. The defect density of the amorphous carbon added with 1.9 was 1.9 × 10 ¹⁸ cm ⁻³ .

From this example and the comparative example, it was confirmed that the defect density can be reduced by exposing the deposited amorphous carbon to F ₂ gas. It was also confirmed that the defect density can be reduced by optimizing the exposure time.

(Example 2)
In Example 2, nitrogen (N ₂ ) as a dopant gas is supplied at a flow rate of 10 sccm instead of the diluted fluorine of Example 1 above, the supply flow rate of argon is 200 sccm, the microwave output is 1000 W, the substrate temperature is 400 ° C., The substrate distance was 1 cm, and other conditions were the same as those in Example 1. In the following examples, fluorine is not added in order to investigate the influence of the substrate distance, the substrate temperature, and the material gas conditions on the defect density of amorphous carbon.

As a result of producing amorphous carbon under the above conditions, amorphous carbon having a defect density of 8.46 × 10 ¹⁸ cm ⁻³ was obtained as shown in Table 3.

(Comparative Example 2)
On the other hand, as Comparative Example 2, when the substrate distance was 0.5 cm under the conditions of Example 2, the amorphous carbon was not formed. In addition, in the amorphous carbon manufactured with the substrate distance of 5.0 cm, as shown in Table 3, the defect density was 3.38 × 10 ¹⁹ cm ⁻³ .

  From this example and the comparative example, it was confirmed that the defect density can be reduced by optimizing the substrate distance.

(Example 3)
In Example 3, the substrate temperature was 380 ° C., and other conditions were the same as in Example 2 above. As a result of producing amorphous carbon under these conditions, amorphous carbon having a defect density of 2.10 × 10 ¹⁸ cm ⁻³ was obtained.

(Comparative Example 3)
On the other hand, as Comparative Example 3, in the amorphous carbon manufactured with the substrate temperatures of 350 ° C. and 400 ° C. under the conditions of Example 2, the defect densities are 3.60 × 10 ¹⁹ cm ⁻³ and 9.69 × 10 ^{18, respectively.} cm ⁻³ .

  The results of this example and comparative example are shown in FIG. As shown in FIG. 3, it was confirmed that the defect density can be reduced by optimizing the substrate temperature.

Example 4
In Example 4, the microwave output was 800 W, the substrate temperature was 25 ° C., and other conditions were the same as in Example 2 above. Here, the reason why the substrate temperature is not within the range preferred in the above embodiment is to investigate the influence of the material gas condition on the defect density of the amorphous carbon.

As a result of producing amorphous carbon under the above conditions, amorphous carbon having a defect density of 1.19 × 10 ¹⁹ cm ⁻³ and 4.45 × 10 ¹⁸ cm ⁻³ was obtained.

(Comparative Example 4)
On the other hand, as Comparative Example 4, amorphous carbon produced as ethylene (C ₂ H ₄ ) at the same flow rate instead of acetylene (C ₂ H ₂ ) under the conditions of Example 4 above has a defect density of 9.08 × 10 ^19. cm ⁻³ and 6.53 × 10 ¹⁹ cm ⁻³ . In addition, when the same flow rate of methane (CH4) was used, amorphous carbon was not formed.

  From this Example and Comparative Example, it was confirmed that the defect density can be reduced by using acetylene as the material gas.

FIG. 4 is a diagram showing the relationship between the fluorine concentration in the amorphous carbon and the defect density. Each plot shown in FIG. 4 is expressed as (0, 2.62 × 10 ¹⁸ ) when (x, y) = (fluorine concentration (% (atm)), defect density (cm ⁻³ )), respectively. (0.3, 8.00 × 10 ¹⁷ ), (0.5, 1.41 × 10 ¹⁸ ), (0.66, 1.76 × 10 ¹⁸ ), and (4.42, 3.21 × 10 ¹⁸ ).

These are the results obtained by supplying argon and diluted fluorine to the amorphous carbon after film formation, and performing the fluorine treatment by changing the exposure time and substrate temperature conditions as follows. . That is, (0.3, 8.00 × 10 ¹⁷ ) is a result obtained under conditions of an exposure time of 10 seconds and a substrate temperature of 25 ° C. in amorphous carbon to which nitrogen is added. Further, (0.5, 1.41 × 10 ¹⁸ ) is a result obtained under the conditions of an exposure time of 10 seconds and a substrate temperature of 25 ° C. in amorphous carbon to which trimethylboron (boron) is added. Further, (0.66, 1.76 × 10 ¹⁸ ) is a result obtained under the conditions of an exposure time of 180 seconds and a substrate temperature of 25 ° C. in amorphous carbon to which trimethylboron (boron) is added. Further, (4.42, 3.21 × 10 ¹⁸ ) is a result obtained under the conditions of an exposure time of 10 seconds and a substrate temperature of 100 ° C. in amorphous carbon to which trimethylboron (boron) is added. In addition, (0, 2.62 × 10 ¹⁸ ) is a result when the fluorine treatment is not performed.

As shown in FIG. 4, the defect density is about 2 × 10 ¹⁸ cm ⁻³ or less when the fluorine concentration is in the range of 5 × 10 ^{−5 to} 3% (atm). Here, 5 × 10 ⁻⁵ % (atm), which is the lower limit of the fluorine concentration, is due to the fact that if there is fluorine (F) having a sufficient number of defects, there is an effect of reducing defects.

  DESCRIPTION OF SYMBOLS 10 ... Plasma CVD apparatus, 11 ... Chamber, 12 ... Source gas source, 13 ... Exhaust means, 14 ... Waveguide, 15 ... Microwave generator, 16 ... Quartz window, 17 ... Slot antenna, 18 ... Substrate stage, 19 ... Exhaust port, 20 ... cooling fan, B ... substrate, C ... amorphous carbon, G ... source gas, P ... surface wave plasma, W ... microwave.

Claims (7)

The fluorine concentration is 5 × 10 ^{−5 to} 3% (atm),
Amorphous carbon. The fluorine concentration is 5 × 10 ^{−5 to} 0.66% (atm).
The amorphous carbon according to claim 1. The fluorine concentration is 0.1 to 0.66% (atm).
The amorphous carbon according to claim 1 or 2. Used as a photoelectric element for solar cells,
The amorphous carbon as described in any one of Claims 1-3. A source gas supply step of supplying a source gas containing fluorine and argon into the chamber;
A plasma generating step for generating plasma of the source gas in the chamber;
A step of forming amorphous carbon on the substrate in the chamber by the plasma,
Amorphous carbon manufacturing method. The fluorine in the source gas is supplied as fluorine (F ₂ ) gas.
The method for producing amorphous carbon according to claim 5. Comprising a fluorine treatment step of exposing the amorphous carbon formed in the forming step to fluorine (F ₂ ) gas,
The method for producing amorphous carbon according to claim 5 or 6.

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