JP2013033828A - Method for forming film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming film in a plasma CVD method which produces a silicon film having high crystallinity and low defect density, and achieves a high film forming speed.SOLUTION: A plasma generation space is formed at an upper part of a processing container 1 by disposing a coiled antenna 52 on the upper surface of the processing container 1, and by applying high-frequency power to the antenna 52. Helium active species are generated by supplying helium gas from a first gas supply part into the plasma generation space. On the other hand, monosilane gas is discharged upward from a second gas supply part 4 that is below the first gas supply part. Thus, the helium active species and the monosilane gas are mixed together, and the monosilane is plasmatized. A film forming processing is performed by supplying a mixed gas containing the plasmatized monosilane to a substrate S. The film forming processing uses no hydrogen gas.

Description

  The present invention relates to a technique for forming a silicon film by converting silane gas into plasma.

  Thin-film silicon solar cells have been actively studied in recent years because they consume less silicon than bulk type crystalline silicon solar cells, are relatively easy to increase in area, and are low in manufacturing costs. For example, a tandem thin-film silicon solar cell (hereinafter simply referred to as a solar cell) has an amorphous silicon film laminated on the top surface of a microcrystalline silicon film, and each layer absorbs light in different wavelength regions, thereby converting light energy conversion efficiency. It is a thing that raised.

As a film formation method of a microcrystalline silicon thin film (μc-Si film) that serves as a power generation layer in a thin film silicon solar cell, silicon is deposited on a substrate using, for example, monosilane (SH ₄ ) gas and hydrogen (H ₂ ) gas. A plasma CVD (Chemical Vapor Deposition) method is used. As a plasma source in this case, generally capacitively coupled plasma (CCP) using a high frequency power source (RF power source) is used.

In this plasma CVD method, various active species derived from SiH ₄ or H ₂ are generated. Among them, the dominant active species for growing the μc-Si film is SiH ₃ . On the other hand, for example, active species other than SiH ₃ such as Si, SiH, and SiH ₂ are taken into the film while having dangling bonds (dangling bonds), thereby increasing the defect density of the μc-Si film. In addition, these active species are polymerized to produce higher order silanes such as Si _n H _{2n + 2} (n = 2, 3, 4...), And these are taken into the film. Even when it grows and is taken in the form of fine particles, it causes an increase in the defect density of the μc-Si film. For this reason, when the film formation rate is increased in the plasma CVD method, the proportion of active species other than the above-mentioned SiH ₃ in the plasma increases, the crystallinity of the μc-Si film decreases, and the defect density increases. There was a problem.

  As described above, in the plasma CVD method using the RF power source, it is difficult to increase the deposition rate while maintaining the required crystallinity and low defect density of the μc-Si film. Although a very high frequency (VHF) has been proposed, further studies are required to deal with large-area substrates.

In Patent Document 1, H ₂ gas is activated to generate the plasma, and SiH ₄ gas is supplied to the substrate side from the plasma generation space while suppressing decomposition of SiH ₄ due to contact with the plasma. A technique for improving the film quality by forming a film by increasing the proportion of SiH ₃ in the active species by reacting with the active species of H ₂ is different from the present invention.

JP2011-86912A

  The present invention has been made under such a background, and an object of the present invention is to provide a film forming method capable of obtaining a silicon film having high crystallinity and low defect density and having a high film forming speed in the plasma CVD method. It is to provide.

The film forming method of the present invention comprises:
A method of forming a film with plasma on a substrate placed in a processing container,
Supplying a silane-based gas and a helium gas as a dilution gas into the processing vessel;
Generating inductively coupled plasma or microwave plasma in the processing vessel and activating a silane-based gas;
Forming a silicon film on the substrate with a silane-based gas that has been converted to plasma, and
Hydrogen gas is not supplied into the processing container.

  In the present invention, when a silicon film is formed by decomposing a silane-based gas, helium (He) gas is used as a dilution gas without supplying a normally used hydrogen gas, and inductively coupled plasma or microwave plasma The gas is turned into plasma. For this reason, the effect is estimated as described later, and a silicon film having a high crystallinity and a low defect density can be quickly formed as supported by experimental examples.

It is a vertical side view of the film-forming apparatus which concerns on embodiment. It is a top view which shows the 2nd gas supply part provided in the said film-forming apparatus. It is a top view which shows typically the plasma production mechanism provided in the said film-forming apparatus. It is a vertical side view explaining typically the operation concerning the embodiment. It is a vertical side view explaining typically the operation concerning the embodiment. It is a graph which shows the experimental result concerning the Example of this invention. It is a graph which shows the experimental result concerning the Example of this invention. It is a graph which shows the experimental result concerning the Example of this invention. It is a graph which shows the experimental result concerning the Example of this invention. It is a graph which shows the experimental result concerning the Example of this invention.

An embodiment of the present invention will be described by taking an inductively coupled plasma (ICP) film forming apparatus as an example. In FIG. 1, reference numeral 1 denotes a processing container (vacuum chamber) that is configured in a cylindrical shape as a whole, for example, and a substrate S that is a glass substrate for a flat panel display, for example, is placed in the approximate center of the processing container 1. A mounting table 2 for this purpose is provided via an insulating material 21. The mounting table 2 is made of, for example, aluminum nitride (AlN) or Al ₂ O ₃ , and a cooling jacket 22 through which a cooling medium flows is provided. In addition, in the mounting table 2, a heater 23 is provided as a heating unit that constitutes a temperature control mechanism together with the cooling jacket 22. The mounting surface of the mounting table 2 is provided with an electrostatic chuck (not shown) so that the substrate S can be held.

  A first gas supply unit 3 for supplying helium gas into the processing container 1 is provided on the upper side wall of the processing container 1. The first gas supply unit 3 is provided over the entire circumference in the side wall of the processing container 1 and a plurality of gas supply holes 31 that are bored substantially uniformly in the side wall of the processing container 1 over the entire circumference. The buffer chamber 32 is connected to the gas supply hole 31. The buffer chamber 32 is connected by a gas flow path 33 to a first gas supply source 36 for supplying helium gas via a valve 34 and a flow rate adjustment unit (MFC) 35.

In the processing container 1, a second planar shape is formed in a substantially circular shape, for example, below the upper space and between the mounting table 2 and the height level of the first gas supply unit 3. A gas supply unit 4 is provided. The second gas supply unit 4 is made of a dielectric material. As shown in FIG. 2, a gas channel network 41 is formed in a lattice shape inside the second gas supply unit 4, and a large number of gas supply holes 42 are formed from the gas channel network 41. 2 is drilled toward the upper surface of the gas supply unit 4 (surface opposite to the mounting table 2). A second gas supply source for supplying a silane-based gas such as monosilane (SiH ₄ ) gas to the gas channel network 41 through a valve 44 and a flow rate adjusting unit (MFC) 45 through a gas supply channel 43. 46 is connected.

  Further, the second gas supply unit 4 is formed with a large number of openings 47 penetrating the second gas supply unit 4 vertically so as to sew the gaps of the reaction gas flow channel network 41. The opening 47 is for allowing gas to pass from the upper region to the lower region of the second gas supply unit 4.

  The ceiling portion of the processing container 1 is open, and a plasma generation mechanism 5 serving as an activating means is provided at this portion via a seal member (not shown) such as an O-ring. As shown in FIG. 1, the plasma generation mechanism 5 includes a cover plate 51 made of a dielectric provided so as to face the second gas supply unit 4, and above the cover plate 51 (outside the processing container 1). The antenna 52 is a conductor provided, for example, a spiral coil, and is connected between both ends of the antenna 52, and includes a high frequency (for example, RF) power source 53 that generates a high frequency of 13.56 Hz, for example. The plasma generation mechanism 5 generates a high-frequency magnetic field by flowing a high-frequency current through the antenna 52 from a high-frequency power source 53, and causes high-frequency discharge in the space above the processing container 1 by an induction electric field generated by electromagnetic induction by the high-frequency magnetic field. To generate plasma.

An exhaust port 11 is provided at the bottom of the processing container 1, and an exhaust pipe 12 is connected to the exhaust port 11. The exhaust pipe 12 is connected to a vacuum pump 14 via a pressure adjusting unit 13 so that the inside of the processing container 1 can be evacuated to a predetermined pressure.
A loading / unloading port 15, which is an opening for loading / unloading the substrate S that is the target of the film forming process, is provided on the lower side wall of the processing container 1. ing.

  The plasma film forming apparatus in the present embodiment is provided with a control unit 6, which starts and stops the high-frequency power supply 53, opens and closes the valves 34 and 44, and adjusts the gas flow rate by the flow rate adjustment units 35 and 45. The pressure adjustment in the processing container 1 by the adjustment and pressure adjustment unit 13 is controlled.

  Subsequently, the operation of the present embodiment will be described with an example in which a microcrystalline silicon thin film (μc-Si film) is formed on the substrate S. First, the substrate S is carried into the processing container 1 by a transport mechanism (not shown), placed on the mounting table 2 by the cooperative action of a lifting pin (not shown) and the transport mechanism, and held by an electrostatic chuck (not shown) of the mounting table 2. Is done. At this time, the temperature of the mounting table 2 is adjusted by the cooling jacket 22 and the heater 23 so that the substrate S is heated to 200 ° C., for example. After the loading / unloading port 15 is closed by the shutter 16, the processing container 1 is decompressed by the vacuum pump 14 and the pressure is adjusted to, for example, 0.6 Pa to 20 Pa by the pressure adjusting unit 13.

Then, helium gas is supplied from the first gas supply unit 3 to the upper space in the processing container 1 at a flow rate of, for example, 200 sccm, and monosilane gas is adjusted from the second gas supply unit 4 to, for example, a flow rate of 20 sccm, and further the high frequency For example, high frequency power of 13.56 MHz and 2000 W is applied to the antenna 52 by the power source 53. FIG. 4 shows a state in which the gas supplied into the processing container 1 is turned into plasma and a silicon film is formed on the substrate S. Is schematically shown. That is, the helium gas supplied to the upper space of the processing container 1 is turned into plasma by the high-frequency electric field induced in the upper space of the processing container 1 based on the high-frequency power applied to the antenna 52 to generate active helium species. Is done. Since the atmosphere in the processing container 1 is evacuated at the lower part of the processing container 1, the activated helium gas flows downward. On the other hand, the monosilane gas discharged upward from the second gas supply unit 4 is partially activated by the high-frequency electric field, but most is activated (plasmaized) in contact with the activated species of helium gas. It is thought. In this case, it can be said that the monosilane gas is activated by the inductively coupled plasma as a result.

Then, the monosilane gas is mixed with plasma helium gas and supplied to the substrate S through the opening 47 of the second gas supply unit 4 while being activated. Here, the presumed mechanism of activation of monosilane gas is described in the following ac.
a. SiH ₄ is directly converted into plasma by a high-frequency electric field to generate SiH _x (x = 0, 1, 2, 3) which is an active species.
b. At this time, the generated active species of hydrogen react with SiH ₄ to produce SiH ₃ as an active species as follows, and further, the active species of hydrogen generated during this reaction react with SiH _3. Te SiH ₂ is generated, the chain reactions as described below takes place and so on.
c. SiH ₄ reacts with the active species of helium to produce SiH _x (x = 0, 1, 2, 3).

In order to increase the crystallinity of the microcrystalline silicon film, it is known that a sufficiently large amount of hydrogen radicals are required for the active species SiH _x . At the same time, in order to reduce the defect density in the microcrystalline silicon film, the concentration of active species SiH ₃ is increased, and the concentration of active species (for example, SiH ₂ , SiH, Si, etc.) further decomposed from SiH ₃ is increased. It is known that it is necessary to suppress this. The active species obtained by further decomposing SiH ₃ is taken into the film while having dangling bonds (dangling bonds), thereby increasing the defect density of the microcrystalline silicon film. In addition, these active species are polymerized to produce higher order silanes such as Si _n H _{2n + 2} (n = 2, 3, 4...), And these are taken into the film. Even when it grows and is taken in the form of fine particles, it becomes a factor in increasing the defect density of the microcrystalline silicon film.

Therefore, it is important to increase the concentration of SiH ₃ while maintaining the amount of hydrogen radicals in the plasma. Therefore, in the present invention, helium gas is used as a dilution gas without using hydrogen gas. As described, the monosilane gas is converted into plasma mainly by helium gas converted into plasma, so that helium gas can also be referred to as plasma generation gas. In general, when a silicon film is formed using monosilane gas as a film forming gas, hydrogen gas is supplied to the substrate at a flow rate of, for example, several tens of times that of monosilane gas in order to improve crystallinity. Such a method is a film forming method with high production efficiency because it can promote hydrogenation of silicon dangling bonds while maintaining high crystallinity in a plasma CVD process using capacitively coupled plasma, for example.

However, when the same hydrogen gas addition is used for inductively coupled plasma or microwave plasma, hydrogen radicals are excessively generated, so that the contact probability between the hydrogen radicals and SiH ₃ is increased, so that further decomposition proceeds from SiH _3. Many active species are generated. On the other hand, when helium gas is used, the helium radical has a higher electron temperature than the hydrogen radical, so that SiH ₄ can be rapidly activated to SiH ₃ even if the radical density is kept low. Since the speed can be increased and the probability of contact between the helium radical and SiH ₃ can be reduced by keeping the radical density low, the decomposition of SiH ₃ is suppressed, so that the It is believed that the defect density can be reduced. Further, since hydrogen radicals necessary for crystallization of the silicon thin film are sufficiently generated in the process of decomposition from SiH ₄ to SiH ₃ , it is possible to increase the deposition rate while maintaining high crystallinity and low defect density. It is considered possible.

Thus, an active species group containing a high concentration of SiH ₃ and in which decomposition of SiH ₃ is suppressed is supplied to the substrate S, and a microcrystalline silicon film with high crystallinity and low defect density is formed on the surface of the substrate S. FIG. 5 shows an image in which SiH ₃ is deposited on the substrate S, and the active species indicated by oblique lines in the figure are those generated by further decomposition of SiH ₃ . Then, after a preset time has elapsed, the application of high-frequency power is stopped, and then the gas supply is stopped.

According to this embodiment, since a mixed gas of monosilane gas and helium gas is converted into a plasma by a high-frequency electric field induced by application of high-frequency power without using hydrogen gas, high-concentration SiH ₃ as already described in detail. The active species group in which decomposition of SiH ₃ is suppressed is supplied onto the substrate S. Therefore, microcrystalline silicon with high crystallinity and low defect density can be obtained at a high film formation rate.

In the above-described embodiment, monosilane gas is used as the silane-based gas, but other silane-based gases such as disilane (Si ₂ H ₆ ) gas and trichlorosilane (SiHCl ₃ ) gas may be used. In this case as well, by generating helium active species, it is possible to suppress the silane-based gas molecules from being shredded, and the same effect can be obtained. Here, the silane-based gas means SiH ₄ gas, polysilane (Si _n H _{2n + 2} (n = 2, 3, 4...)) Gas, silane compound gas, and the like. In the above-described embodiment, inductively coupled plasma is generated. Instead of the antenna 52, for example, an antenna in which a cross-shaped opening is formed in a spiral shape on a circular conductor plate is used and guided to the center of the antenna. A wave tube may be joined, and a microwave may be radiated from the waveguide through the antenna, and the gas may be converted into plasma by the microwave.

  Here, the present invention requires that no hydrogen gas is used, and the adverse effect of promoting the decomposition of the monosilane gas by adding the hydrogen gas appears. However, the influence of hydrogen gas becomes a problem when supplying many times the amount of monosilane gas, and hardly affects when supplying the same amount of hydrogen gas as monosilane gas. The addition of such a small amount of hydrogen gas has no technical meaning in the first place, and this approach is an unreasonable practice that seeks to dive into the limitations of the expression of the claims while carrying out the present invention. Therefore, the term “do not use hydrogen gas” in the claims does not exclude the addition of a small amount of hydrogen gas which has no technical meaning.

Examples of the present invention will be described.
[Experiment 1]
As will be described below, the process pressure is set to 0.4 Pa to 1.0 Pa, the SiH ₄ gas supply amount is fixed in the range of 5 sccm to 6 sccm, and monosilane (SiH ₄ ) A microcrystalline silicon (μc-Si) film is formed by ICP-CVD while adding various dilution gases about 10 times the gas, and measurement and film formation by Raman spectroscopy is performed on the microcrystalline silicon film. Speed measurements were taken. Note that the dilution gas described below is a gas added to the reaction gas during the film forming process.

Example 1
High frequency power: 2000W
Reaction gas species and reaction gas supply amount: SiH ₄ , 5 sccm
Dilution gas type and dilution gas supply amount: Helium (He), 49 sccm
Process pressure: 0.6Pa
(Reference Example 1)
High frequency power: 2000W
Reaction gas species and reaction gas supply amount: SiH ₄ , 5 sccm
Dilution gas type and dilution gas supply amount: Ar, 50 sccm
Process pressure: 0.9Pa
(Comparative Example 1-1)
High frequency power: 2000W
Reaction gas species and reaction gas supply amount: SiH ₄ , 6 sccm
Dilution gas type and dilution gas supply: No dilution gas is supplied.
Process pressure: 1.0 Pa
(Comparative Example 1-2)
High frequency power: 2000W
Reaction gas species and reaction gas supply amount: SiH ₄ , 5 sccm
Dilution gas type and dilution gas supply amount: H ₂ , 50 sccm
Process pressure: 0.4 Pa

  FIG. 6 shows the results of Raman spectroscopic measurement in this experiment, and Table 1 shows the calculated values of the intensity ratio Xc described later calculated from the results of Raman spectroscopic measurements and the film formation rate.

The intensity patterns a, b, c, and d in FIG. 6 correspond to Example 1, Reference Example 1, Comparative Example 1-1, and Comparative Example 1-2, respectively.
The intensity Ia at a wave number of 480 cm ⁻¹ in Raman spectroscopy corresponds to the amount of material of amorphous silicon (a-Si), and the intensity Ic at 520 cm ⁻¹ corresponds to the amount of material of microcrystalline silicon (μc-Si). . The intensity ratio Xc (Xc = Ic / (Ia + Ic)) is known as an index representing the crystallinity of the measured silicon film. In this example, the crystallinity of the silicon film was evaluated using the intensity ratio Xc corresponding to this crystallinity.

As can be seen from FIG. 6, in Example 1, the wave number at the peak position of the intensity pattern is very close to 520 cm ⁻¹ (ideal wave number) corresponding to μc-Si, but in Reference Example 1, the wave number at the peak position. Is about 515 cm ^−1, which is slightly shifted from the ideal wave number. The wave number at the peak position in Comparative Example 1-1 is further shifted from the ideal wave number, and in Comparative Example 1-2, the wave number at the peak position is less than 510 cm ⁻¹ . On the other hand, the film formation rate in Example 1 is slower than those in Comparative Example 1-1 and Comparative Example 1-2. However, as can be seen from the results of Experiment 2, the film formation is performed by increasing the flow rates of monosilane gas and helium gas. Speed can be improved.
In Example 1 and Reference Example 1, the strength ratio Xc is 80% or more, and it can be seen that the crystallinity is good.

[Experiment 2]
In response to the result of Experiment 1 described above, when the deposition rate is increased by increasing the supply amount of SiH ₄ gas when forming a film by adding He gas, what is the crystallinity of the silicon film? In order to verify whether or not the behavior is exhibited, the relationship between the supply amount of SiH ₄ gas, Xc, and the film formation rate was experimentally determined for each of cases where He gas was added (Example 2) and not (Comparative Example 2). Examined. The film forming conditions in this experiment are shown below.

(Example 2)
High frequency power: 2000W
Reaction gas species and reaction gas supply amount: SiH ₄ , 5, 10, 15, 20 sccm
Dilution gas type and dilution gas supply amount: He, 10 times the reaction gas supply amount Process pressure: 0.6 Pa to 1.9 Pa
(Comparative Example 2)
High frequency power: 2000W
Reactive gas species and reactive gas supply amount: SiH ₄ , 6, 8, 12 sccm
Dilution gas type and dilution gas supply: No dilution gas is supplied.
Process pressure: 1.0 Pa

The results of this experiment are shown in FIGS.
First, FIG. 7 shows the experimental results when no He gas is added. When the SiH ₄ gas supply amount was 6 sccm, Xc of 60% or more could be obtained. However, when the SiH ₄ gas supply amount was 8 sccm or more, the deposition rate increased in proportion to the SiH ₄ gas supply amount. In contrast, Xc was significantly reduced. Although not shown, the same tendency was observed when H ₂ gas was added.
On the other hand, when He gas is added, as shown in FIG. 8, as the SiH ₄ gas supply amount is increased, the deposition rate increases almost in proportion to this, and when Xc is not added with He gas (comparison). The high value of about 80% was maintained without decreasing as in Example 2). For example, if the deposition rate of the silicon film is 0.55 nm / sec or more and the peak intensity ratio (crystallinity) Xc is 70% or more, it is a preferable manufacturing method in terms of productivity and crystallinity of the silicon film. Can do.

[Experiment 3]
As described in the above-described embodiment, the present inventor has activated SiH ₄ under a condition in which the radical density is suppressed by the He radical having a high electron temperature. Therefore, the active species SiH ₃ is further decomposed. It is considered that film formation can be performed in a state where the above is suppressed. Therefore, in this experiment, the degree of decomposition from SiH ₃ to SiH ₂ was investigated for each of the case using helium gas (Example 3) and the case using hydrogen gas (Comparative Example 3). Specifically, the concentrations of SiH, which is a further active product of decomposition of SiH ₂ , and Si in the processing atmosphere are identified by emission spectroscopy (OES), and the concentration ratio thereof, that is, the peak intensity ratio SiH / Si is The degree of decomposition from SiH ₃ to SiH ₂ was evaluated by assuming that it was equal to the concentration ratio of SiH ₃ and SiH ₂ . The “SiH ₄ gas flow rate ratio” described below is the ratio of the SiH ₄ gas supply amount to the total gas supply amount of the SiH ₄ gas and the dilution gas.

(Example 3)
High frequency power: 2000W
Total gas supply amount of SiH ₄ gas and dilution gas: 100 sccm
Dilution gas type: He
SiH ₄ gas flow ratio: 5, 10, 15, 20, 25, 30%
Process pressure: 1.0 Pa
(Comparative Example 3)
High frequency power: 2000W
Total gas supply amount of SiH ₄ gas and dilution gas: 10 sccm
Dilution gas type: H ₂
SiH ₄ gas flow ratio: 15, 40, 50, 60, 80, 100%
Process pressure: 1.0 Pa

The result of this experiment is shown in FIG. The SiH ₄ gas flow rate ratio of 100% indicates a case where only SiH ₄ gas is supplied without adding a dilution gas. As shown in FIG. 9, when the dilution gas is hydrogen gas, the emission intensity ratio SiH / Si tends to decrease as the SiH ₄ gas flow rate ratio decreases. That is, as the ratio of the supply amount of hydrogen gas in the mixed gas is increased, the degree to which SiH ₃ is decomposed into SiH ₂ tends to increase. On the other hand, when the dilution gas is helium gas, the emission intensity ratio SiH / Si increases as the SiH ₄ gas flow rate ratio is increased from 5% (the flow rate ratio of helium gas is decreased from 95%). If the SiH ₄ gas flow rate ratio is further increased (the helium gas flow rate ratio is decreased), the emission intensity ratio SiH / Si is presumed to decrease, but hydrogen gas is used by adjusting the supply amount of helium gas. It can be seen that a considerably high value is obtained for the emission intensity ratio SiH / Si as compared to the case.

[Experiment 4]
In this experiment, the crystal orientation of the deposited silicon film was verified by X-ray diffraction (XRD). The film thickness of the measurement sample is 1000 nm, and the ratio I (220) / I (111) between the peak intensity I (220) corresponding to Si (220) and the peak intensity I (111) corresponding to Si (111) is crystallized. It was used as an index of orientation. Generally, it is said that the larger the peak intensity ratio I (220) / I (111), the more desirable characteristics as a solar cell. In this experiment, a silicon film formed by CCP-CVD with H ₂ gas added as a reference example was also measured by X-ray diffraction. The dilution gas supply ratio described below is the ratio of the dilution gas supply amount to the SiH ₄ gas supply amount.

Example 4
Plasma source: ICP, high frequency power 2000W
Reaction gas species and reaction gas supply amount: SiH ₄ , 5 sccm
Dilution gas type and dilution gas supply ratio: He, 10/1
Process pressure: 0.6Pa
(Comparative Example 4-1)
Plasma source: ICP, high frequency power 2000W
Reaction gas species and reaction gas supply amount: SiH ₄ , 6 sccm
Dilution gas type and dilution gas supply ratio: No dilution gas is supplied.
Process pressure: 0.9Pa
(Comparative Example 4-2)
Plasma source: ICP, high frequency power 1600W
Reaction gas species and reaction gas supply amount: SiH ₄ , 2 sccm
Dilution gas type and dilution gas supply ratio: H ₂ , 7/1
Process pressure: 1.0 Pa
(Reference Example 4-1)
Plasma source: CCP, high frequency power 100W
Reaction gas species and reaction gas supply amount: SiH ₄ , 10 sccm
Dilution gas type and dilution gas supply ratio: H ₂ , 50/1
Process pressure: 800Pa
(Reference Example 4-2)
Plasma source: CCP, high frequency power 100W
Reaction gas species and reaction gas supply amount: SiH ₄ , 5 sccm
Dilution gas type and dilution gas supply ratio: H ₂ , 100/1
Process pressure: 800Pa

The measurement results in this experiment are shown in FIG.
First, when the three comparisons of Example 4, Comparative Example 4-1 and Comparative Example 4-2, which are examples by ICP-CVD, are performed, the examples are in descending order of the peak intensity ratio I (220) / I (111). 4 and Comparative Example 4-1 and Comparative Example 4-2 were obtained. That is, the crystal orientation was good in the order of He dilution, SiH ₄ supply, and H ₂ dilution. Next, when Example 4 is compared with Reference Example 4-1 and Reference Example 4-2, which are examples based on CCP-CVD, Example 4 does not reach Reference Example 4-1 in terms of crystal orientation. However, it was better than Reference Example 4-2.

[Experiment 5]
In this experiment, the spin density of a silicon film formed by electron spin resonance (ESR) analysis was measured, and the density of dangling bonds in the silicon film was measured. At that time, the crystallinity Xc and the film formation rate were also measured, and the results are also shown in Table 2 described later.

(Example 5)
Plasma source: ICP, high frequency power 2000W
Reaction gas species and reaction gas supply amount: SiH ₄ , 15 sccm
Dilution gas type and dilution gas supply ratio: He, 6/1
Process pressure: 1.0 Pa
(Comparative Example 5-1)
Plasma source: ICP, high frequency power 2000W
Reaction gas species and reaction gas supply amount: SiH ₄ , 6 sccm
Dilution gas type and dilution gas supply ratio: No dilution gas is supplied.
Process pressure: 1.0 Pa
(Comparative Example 5-2)
Plasma source: ICP, high frequency power 1600W
Reaction gas species and reaction gas supply amount: SiH ₄ , 2 sccm
Dilution gas type and dilution gas supply ratio: H ₂ , 7/1
Process pressure: 1.0 Pa
(Reference Example 5)
Plasma source: CCP, high frequency power 100-700W
Reaction gas species and reaction gas supply amount: SiH ₄ , 5 to ₄₀ sccm
Dilution gas type and dilution gas supply ratio: H ₂ , 50/1 to 100/1
Process pressure: 800-1200Pa

Table 2 shows the measurement results in this experiment.
As shown in Table 2, in Example 5, since the detection value of ESR analysis is smaller than those in Comparative Example 5-1 and Comparative Example 5-2, dangling bonds are reduced by adding He gas. It is presumed that defects in the formed silicon film are reduced. Regarding the crystallinity Xc and the film formation rate, Example 5 was a better result than Comparative Example 5-1 and Comparative Example 5-2. Example 5 had more dangling bonds than Reference Example 5 which is a silicon film formed by CCP-CVD.

S glass substrate 1 processing vessel 13 pressure adjusting unit 14 vacuum pump 2 mounting table 3 first gas supply unit 4 second gas supply unit 5 plasma generation mechanism 52 antenna 53 high frequency power supply 6 control unit

Claims (3)

A method of forming a film with plasma on a substrate placed in a processing container,
Supplying a silane-based gas and a helium gas as a dilution gas into the processing vessel;
Generating inductively coupled plasma or microwave plasma in the processing vessel and activating a silane-based gas;
Forming a silicon film on the substrate with a silane-based gas that has been converted to plasma, and
A film forming method, wherein hydrogen gas is not supplied into the processing container. The rate of forming the silicon film is 0.55 nm / sec or more,
2. The film forming method according to claim 1, wherein Ic / (Ia + Ic) is 70% or more when the peak intensity of crystalline silicon and the peak intensity of amorphous silicon by Raman spectroscopy are Ic and Ia, respectively. A substrate, a silane-based gas supply port, a helium gas supply port, and a plasma generation unit are arranged in this order from the bottom,
3. The film forming method according to claim 1, wherein the helium gas is converted into plasma, and the silane-based gas is converted into plasma by the plasma-formed helium gas.

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