KR20130135351A - Thin film forming device - Google Patents

Abstract

A thin film forming apparatus for forming a passivation film on a substrate, comprising: a chamber into which a reaction gas containing a source gas of the passivation film is introduced, a substrate plate disposed in the chamber to load the substrate, a substrate plate disposed in the chamber, and a substrate on the substrate plate; An alternating current power of 40 kHz or more and a frequency of 450 kHz or less is supplied between the substrate plate and the electrode while stopping the supply of the alternating current power at regular intervals, and the source gas is supplied from the upper surface of the substrate. An alternating current power source for exciting the plasma to be included is provided.

Description

Thin Film Forming Equipment {THIN FILM FORMING DEVICE}

The present invention relates to a thin film forming apparatus for exciting a plasma to perform a film forming process.

In the manufacturing process of a semiconductor device, the plasma processing apparatus is used in a film forming process, an etching process, an ashing process, etc. from the advantage that high precision process control is easy. For example, a plasma chemical vapor deposition (CVD) apparatus is known as a plasma processing apparatus.

In a plasma CVD apparatus, source gas is plasma-formed by high frequency electric power etc., and a thin film is formed on a board | substrate by a chemical reaction. Moreover, in order to improve film-forming efficiency, the plasma CVD apparatus which uses a hollow cathode discharge is proposed (for example, refer patent document 1).

Patent Document 1: Japanese Patent Application Laid-Open No. 2004-296526

In general, a silicon nitride film having a refractive index of 1.92 to 2.4 and a film thickness of about 70 to 100 nm is used for a passivation film such as an antireflection film of a crystalline silicon solar cell. In the case of forming such a thin film, when a low frequency of 1 MHz or less is used as the frequency of the AC power supply of the plasma CVD apparatus, the passivation effect of the surface of the crystalline silicon film and the inside of the substrate on which the crystalline silicon film is formed is increased, and the solar cell is converted. The efficiency is improved. However, when a low frequency of 1 MHz or less is used, the plasma density during the film forming process decreases and the film forming efficiency decreases.

On the other hand, in a plasma CVD apparatus using hollow cathode discharge, an AC power source having a frequency of 1 MHz or more is used. For example, in the case of forming a thin film silicon film for a thin film transistor (TFT), there is no particular problem even if a frequency of 1 MHz or more is used. However, in the case of forming an anti-reflection film of a crystalline silicon solar cell, using an AC power source having a frequency of 1 MHz or more, the passivation effect of the surface of the crystalline silicon film and the inside of the substrate is low, and the conversion efficiency of the solar cell is lowered. There was.

In view of the above problems, an object of the present invention is to form a thin film in which the deterioration of the passivation effect is suppressed and to provide a thin film forming apparatus having high film forming efficiency.

According to one aspect of the present invention, there is provided a thin film forming apparatus for forming a passivation film on a substrate, comprising: (a) a chamber into which a reaction gas containing a source gas of the passivation film is introduced; and (b) a chamber disposed therein for loading a substrate. (C) an electrode disposed in the chamber, (c) an electrode having a groove formed on a surface of the substrate plate facing the substrate, and (d) AC power having a frequency of 40 kHz or more and 450 kHz or less at regular intervals. A thin film forming apparatus is provided, which is provided with an AC power supply that is supplied between a substrate plate and an electrode and stops a plasma containing a source gas at an upper surface of the substrate while stopping.

According to this invention, the thin film by which the fall of the passivation effect was suppressed can be formed, and the thin film forming apparatus with high film-forming efficiency can be provided.

1 is a schematic view showing the configuration of a thin film forming apparatus according to an embodiment of the present invention.
2 is a schematic view showing an example of a groove formed on the surface of an electrode of the thin film forming apparatus according to the embodiment of the present invention.
3 is a graph showing the relationship between the frequency of power supplied and the number of ions colliding with the surface of the substrate.
4 is a graph showing the relationship between substrate temperature and conversion efficiency.
5 is a table showing a comparison between thin film formation by a thin film forming apparatus according to an embodiment of the present invention and thin film formation by a comparative example.
6 is a schematic view showing the configuration of a thin film forming apparatus according to another embodiment of the present invention.
It is a schematic diagram which shows the structure of the thin film forming apparatus which concerns on other embodiment of this invention.

EMBODIMENT OF THE INVENTION Embodiment of this invention is described with reference to drawings. In description of the following drawings, the same or similar code | symbol is attached | subjected to the same or similar part. However, it should be noted that the drawings are schematic. In addition, embodiment shown below illustrates the apparatus and method for actualizing the technical idea of this invention, and embodiment of this invention does not specify the structure, arrangement | positioning, etc. of a component as follows. Embodiment of this invention can add a various change in a Claim.

The thin film forming apparatus 10 according to the embodiment of the present invention is a thin film forming apparatus for forming the passivation film 110 on the substrate 100. As shown in FIG. 1, the thin film forming apparatus 10 is disposed in the chamber 11 and the chamber 11 into which the reaction gas 120 containing the source gas of the passivation film 110 is introduced, and the substrate 100. ) And a plurality of jet holes 131 disposed in the chamber 11 and in the chamber 11 and facing the substrate 100 on the substrate plate 12 so that the reaction gas 120 passes. The substrate plate (with the electrode 13 provided with the opening of the opening and the groove 132 formed around the opening) and the AC power having a frequency of 50 kHz or more and 450 kHz or less while stopping the supply of the AC power at regular intervals ( An AC power supply 14 is provided between the electrode 12 and the electrode 13 to excite the plasma containing the source gas on the upper surface of the substrate 100.

The reaction gas 120 is introduced into the chamber 11 by the gas supply mechanism 15. In addition, the inside of the chamber 11 is decompressed by the gas exhaust mechanism 16. After the pressure of the reaction gas in the chamber 11 is adjusted to a predetermined gas pressure, between the electrode plate 13 and the substrate plate 12 provided with the predetermined alternating current power by the alternating current power supply 14 through the matching box 141. Supplied. As a result, the reaction gas 120 including the source gas in the chamber 11 is converted into plasma. By cutting the substrate 100 on the formed plasma, a desired thin film is formed on the exposed surface of the substrate 100.

As shown in FIG. 1, an opening and a groove 132 of the ejection hole 131 are disposed on a surface of the electrode 13 that faces the substrate 100, and the electrode 13 causes hollow cathode discharge to be generated. It functions as a hollow cathode electrode. That is, the confinement of electrons by the hollow cathode effect occurs in the groove 132 formed on the surface of the electrode 13, and the high-density plasma is stably generated in the form supplied from the groove 132. As a result, the source gas is decomposed efficiently, and the passivation film 110 is formed on the substrate 100 at a high speed and in a large area uniformly.

In FIG. 2, the grooves 132 are continuously formed around the jetting holes 131 along the array direction of the jetting holes 131 for one row on the surface 130 facing the substrate 100 of the electrode 13. The example which formed. If it is arrange | positioned around the opening part of the blowing hole 131, various structures can be employ | adopted for the layout of the groove | channel 132. As shown in FIG. For example, the grooves 132 may be formed in a lattice shape so that the openings of the blowing holes 131 are arranged at the intersections of the lattice.

Usually, when exciting a plasma using hollow cathode discharge, the frequency of the alternating current power supplied between electrodes is 1 MHz or more. For this reason, in the thin film forming apparatus 10 using the alternating current power of the frequency of 50 kHz-450 kHz, supply of alternating current power is stopped by a fixed period in order to form plasma stably in the chamber 11.

That is, the AC power supply 14 pulse-controls the supply of AC power between the substrate plate 12 and the electrode 13, and periodically turns on and off the supply of AC power. For example, the substrate plate 12 and the electrode 13 are set so that the on time for supplying AC power is 600 µs and the off time for stopping supply of AC power is 50 µs, and the on time and the off time are alternately repeated. AC power is supplied between In addition, on time is set to about 300 microseconds-about 1500 microseconds, and off time is set to about 25 microseconds-about 50 microseconds. If the off time is set too long, the power efficiency is lowered. Therefore, it is preferable to set the off time at about 50 μsec. Usually, when the frequency of AC power is 1 MHz or more, it is not necessary to turn off supply of AC power.

In the thin film forming apparatus 10, the frequency of the alternating current power supplied between the substrate plate 12 and the electrode 13 is set to 50 kHz to 450 kHz to the substrate 100 in a state where a plasma is formed in the chamber 11. This is because the number of colliding ions is increased. Thereby, the passivation effect of the surface and the inside of the board | substrate 100 can be enlarged, and the conversion efficiency of a crystalline silicon solar cell can be improved as demonstrated below.

For example, a polysilicon substrate is used for the substrate of the crystalline silicon solar cell. In a polysilicon substrate, the grain boundary of polysilicon becomes a defect. Carriers are supplemented with this defect and the conversion efficiency is lowered. However, by impinging hydrogen (H) ions or the like on the substrate 100, the unbound portion of the crystal in the polysilicon can be terminated by the H ions. This reduces the replenishment of carriers due to defects and increases the passivation effect. As a result, the conversion efficiency of the crystalline silicon solar cell is improved.

The graph shown in FIG. 3 shows the relationship between the frequency of the power supplied between the electrodes and the number of ions colliding with the surface of the substrate (Akihisa Matsuda et al., `` Influence of Power-Source Frequency on the Properties of GD a-Si: H '' , Japanese Journal of Applied Physics, Vol. 23, NO. 8, August, 1984, L568-L569). As shown in Fig. 3, the number of ions colliding with the substrate is high when the frequency is 10 kHz to 500 kHz, and the number of ions colliding with the substrate is small when the frequency is 1 MHz or more.

Therefore, by setting the frequency of the alternating current power supplied between the substrate plate 12 and the electrode 13 to 10 kHz to 500 kHz, a large number of ions can collide with the substrate 100 as compared with the case where the frequency is 1 MHz or more. . As described above, by impinging H ions or the like on the substrate 100, the passivation effect on the surface and the inside of the substrate 100 can be increased. Moreover, more reliably, it is preferable to make the frequency of AC power into 50 kHz-450 kHz.

As described above, according to the thin film forming apparatus 10, the passivation effect of the surface and the inside of the substrate 100 is increased by setting the frequency of the alternating current power supplied by the alternating current power supply 14 to 50 kHz to 450 kHz. That is, according to the thin film formation apparatus 10, the thin film with high passivation effect can be formed. Thereby, for example, the conversion efficiency of a solar cell can be improved.

The case where the anti-reflection film of a crystalline silicon solar cell is formed by the thin film forming apparatus 10 shown in FIG. 1 below is considered. That is, the substrate 100 is a crystalline silicon solar cell substrate, and the passivation film 110 is an antireflection film. At this time, the substrate 100 has a surface diffusion concentration of 1 × 10 ¹⁸ to 1 × 10 ²² formed on the p-type silicon substrate, or a surface diffusion concentration of 1 on the n-type silicon substrate. The board | substrate etc. which formed the p-type semiconductor layer which are x10 <^18> -1 * 10 <^22> are employable. The passivation film 110 is a silicon nitride (SiN) film having a refractive index of 1.3 to 3.0 and a film thickness of about 50 to 150 nm.

In order to form the passivation film 110 which consists of SiN films, for example on the board | substrate 100, monosilane, ammonia, etc. are employ | adopted as source gas, and nitrogen (N), hydrogen (H), Argon (Ar), helium (He), and the like are employed.

The width of the groove 132 is set to 5 mm to 10 mm. In the case of using a conventional hollow cathode discharge, the width of the grooves formed on the surface of the high frequency electrode is about 1 to 4 mm. In the thin film forming apparatus 10, plasma can be stably formed by making the groove 132 wide. However, if the width is too wide, the state of the plasma tends to be unstable, so the groove of the groove 132 is preferably not more than 10 mm. In addition, although the diameter of the opening part of the blowing hole 131 depends on the number of the blowing holes 131 formed in the electrode 13, it is generally 1 mm or less.

Usually, when using a hollow cathode discharge, the pressure of reaction gas is 500 Pa or more. However, in the thin film forming apparatus 10, in order to stably form the plasma in the chamber 11, it is preferable to set the pressure of the reaction gas 120 including the source gas and the carrier gas as low as 50 Pa to 100 Pa. desirable.

In addition, setting the substrate 100 at 250 ° C to 550 ° C while the plasma is excited in the chamber 11 realizes high solar cell conversion efficiency (hereinafter, simply referred to as "conversion efficiency"). It is preferable at the point. As shown in FIG. 4, the relationship between the substrate temperature and the conversion efficiency, a high conversion efficiency of 15.6% to 16% or more is obtained at a substrate temperature of 300 ° C to 450 ° C.

In the thin film forming apparatus 10 shown in FIG. 1, the temperature of the board | substrate 100 can be set arbitrarily by the heater 17 integrated in the board | substrate plate 12. FIG. As mentioned above, high conversion efficiency is obtained by setting the temperature of the board | substrate 100 to 300 to 450 degreeC. Moreover, it is more preferable to make the temperature of the board | substrate 100 into 400 to 450 degreeC.

5 shows an example in which the passivation film 110 is formed as an antireflection film of a crystalline silicon solar cell using the thin film forming apparatus 10 shown in FIG. 1 and the thin film forming apparatus of the comparative example, respectively. Here, the frequency of the AC power of the thin film forming apparatus 10 is 250 kHz. In the comparative example 1, the frequency of alternating current power was 250 kHz, and the parallel plate electrode was used without using a hollow cathode electrode. In the comparative example 2, the hollow cathode electrode is used and the frequency of alternating current power is 213.56 MHz. In addition, the prepared crystalline silicon solar cell has a structure in which a SiN film having a thickness of 80 nm is formed on a polysilicon substrate.

As shown in FIG. 5, in the thin film forming apparatus 10 and the comparative example 1 whose frequency of alternating current power is 250 kHz, solar cell conversion efficiency is equal. However, while the film forming rate of Comparative Example 1 is 28 nm / min, the film forming rate of the thin film forming apparatus 10 using the hollow cathode electrode is 180 nm / minute, and the film forming efficiency of the thin film forming apparatus 10 is very high.

In addition, in the comparative example 2 which used the thin film forming apparatus 10 and the hollow cathode electrode, film-forming rates are equivalent. However, the solar cell conversion efficiency of the thin film forming apparatus 10 is 16.5%, and is larger than the comparative example 2 while the solar cell conversion efficiency of the comparative example 2 whose AC power frequency is 13.56 MHz is 16.3%. That is, in the comparative example 2 with a high frequency of alternating current power, the fall of a passivation effect is large and conversion efficiency falls. On the other hand, in the thin film forming apparatus 10, the fall of a passivation effect is suppressed compared with the comparative example 2, and high conversion efficiency is obtained.

Therefore, in the thin film forming apparatus 10, high film forming efficiency by using a hollow cathode electrode can be realized, while obtaining a high solar cell conversion efficiency by supplying an AC electrode of a low frequency.

As described above, in the thin film forming apparatus 10 according to the embodiment of the present invention, film formation using hollow cathode discharge can be realized using AC power having a frequency of 50 kHz to 450 kHz. As a result, the thin film in which the fall of the passivation effect was suppressed can be formed, and the thin film forming apparatus 10 with high film-forming efficiency can be provided.

As mentioned above, although this invention was described by embodiment, it should not be understood that the description and drawings which form a part of this indication limit this invention. Various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art from this disclosure.

In FIG. 1, the reaction gas 120 passes through the inside of the electrode 13, and the reaction gas 120 blows into the chamber 11 from the opening of the blowing hole 131 formed in the surface of the electrode 13. Indicated. However, even if the electrode 13 is not the shower plate type electrode as mentioned above, this invention is applicable.

For example, as shown in FIG. 6, the reaction gas 120 is introduced into the chamber 11 directly from the gas supply mechanism 15 without passing the reaction gas 120 inside the electrode 13. Also good. Also in the thin film forming apparatus 10 shown in FIG. 6, the electrode 13 in which the groove 132 was formed in the surface functions as a hollow cathode electrode. That is, the confinement of electrons by the hollow cathode effect occurs in the groove 132 formed on the surface of the electrode 13, whereby a high density plasma is stably generated. As a result, the source gas is efficiently decomposed, and the passivation film 110 is formed on the substrate 100 at a high speed and large area uniformly. In addition, similarly to the thin film forming apparatus 10 shown in FIG. 1, in the thin film forming apparatus 10 shown in FIG. 6, various configurations can be adopted for the layout of the grooves 132. That is, the groove 132 may be formed in a lattice shape or may be formed in a stripe shape.

In addition, as shown in FIG. 7, the present invention is also applicable to the thin film forming apparatus 10 having a plurality of positions where the substrate 100 is arranged. In the example shown in FIG. 7, the substrate plate 12 and the electrode 13 form a comb shape having a plurality of teeth portions extending in the vertical direction toward the ground, respectively, to form the substrate plate 12 and the electrode 13. The teeth of the comb are arranged in the shape of the cross indication. The substrate 100 is mounted on a plurality of tooth portions that face the electrodes 13 of the substrate plate 12, respectively.

And the reaction gas 120 is introduce | transduced from the gas supply mechanism 15 in the chamber 11 of FIG. 7 in which the some board | substrate 100 is arrange | positioned vertically. The groove 132 is formed in the surface of the tooth part of the electrode 13, and the electrode 13 functions as a hollow cathode electrode. In the example shown in FIG. 7, the groove 132 is formed through the tooth portion of the electrode 13. According to the thin film forming apparatus 10 shown in FIG. 7, it is possible to form a passivation film | membrane on the some board | substrate 100 simultaneously.

Thus, of course, this invention includes various embodiment etc. which are not described here. Accordingly, the technical scope of the present invention is determined only by the specific matters of the invention according to the appended claims.

Industrial availability

The thin film forming apparatus of this invention can be used for the use which forms the thin film in which the fall of the passivation effect was suppressed.

Claims (9)

A thin film forming apparatus for forming a passivation film on a substrate,
A chamber into which the reaction gas containing the source gas of the passivation film is introduced;
A substrate plate disposed in the chamber for loading the substrate;
An electrode disposed in the chamber, the electrode having a groove formed on a surface of the substrate plate facing the substrate;
AC power having a frequency of 50 kHz or more and 450 kHz or less is supplied between the substrate plate and the electrode while stopping the supply of the AC power at a constant cycle to excite the plasma containing the source gas on the upper surface of the substrate. A thin film forming apparatus comprising a power supply. The method according to claim 1,
The opening part of the some blowing hole which the said reaction gas passes through is formed in the bottom part of the said groove | channel formed in the said electrode, The thin film forming apparatus characterized by the above-mentioned. The method according to claim 1,
The time for which the supply of the AC power is stopped is 25 μsec or more and 50 μsec or less. The method according to claim 1,
And the width of the groove is 5 mm or more and 10 mm or less. The method according to claim 1,
And a heating device for setting the substrate to 300 ° C or higher and 450 ° C or lower in a state where the plasma is excited. The method according to claim 1,
And the pressure of the reaction gas in the chamber is set to 50 Pa or more and 100 Pa or less. The method according to claim 1,
And the substrate is a crystalline silicon solar cell substrate. The method of claim 7,
And said passivation film formed on said substrate is an anti-reflection film of a crystalline silicon solar cell. The method according to claim 1,
And a passivation film formed on the substrate is 180 nm / min or more.

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