JPH0199213A - Device for formation of film - Google Patents

Abstract

PURPOSE:To homogeneously form a film on a substrate having a large area at a high film forming speed by employing a high frequency application electrode in which its predetermined specified surface is formed in an uneven state. CONSTITUTION:A substrate 4 is mounted or advanced in a glow discharge generated between a high frequency application electrode 1 and a ground electrode 2, and a thin film is formed on the substrate 4. In this case, the surface of the electrode 1 is formed in an uneven state. The height (h) of a crest on the uneven state of the electrode, i.e., the depth of a recess is 1/2 or more of the interval (d) of the electrodes, and preferably the same as the (d) or more. The width (w) of the crest of the electrode 1 is made 5cm or less. Thus, a film is homogeneously formed on the substrate 4 having a large area at a high film forming speed.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a film forming apparatus that continuously forms thin films by glow discharge, and in particular, relates to a film forming apparatus that uniformly forms a high performance semiconductor thin film at a high film forming rate. It relates to a film forming apparatus.

[Prior Art] Amorphous silicon-based semiconductor thin films obtained by glow discharge decomposition or photodecomposition of silicon compounds have an excellent ability to convert light to electrical energy, and are used as photovoltaic devices. Furthermore, use is being considered not only for consumer devices such as calculators, but also as power solar cells, but for this purpose it is necessary to manufacture large-area solar cells at low cost. In this respect, it is basically relatively easy to expand the area of amorphous silicon-based solar cells, and research on increasing the area is being conducted.

However, conventional film forming apparatuses using capacitively coupled parallel plate electrodes have had several problems when uniformly forming a high performance semiconductor thin film at a high film forming rate.

That is, first of all, in this film forming method, a substrate on which a film is formed is installed between an electrode to which a high frequency is applied (high frequency application electrode) and an electrode that is grounded (ground electrode). In this case, the uniformity of the thin film cannot be obtained unless the uniformity of the glow discharge is ensured within the plane of the high-frequency applied electrode.Naturally, when depositing a film on a large-area substrate, The area of the high frequency application electrode must be made larger than the substrate, but with a large area electrode, a skin effect peculiar to high frequency current occurs, making it impossible to effectively introduce high frequency current. In addition, as a result of the edge effect and skin effect on the electric lines of force, glow discharge becomes stronger around the electrode to which high frequency is applied, which not only makes the film formation rate uneven, but also deteriorates the properties of the obtained thin film. In addition to the non-uniformity, under high-speed film formation conditions, the glow discharge around the high-frequency application electrode becomes even stronger, further exacerbating this problem.

[Object of the Invention] The object of the present invention is to generate a high concentration plasma between the high frequency application tF11 and the ground electrode, and to form a uniform semiconductor thin film on a substrate at a high deposition rate. An object of the present invention is to provide a film forming apparatus.

[Basic idea] As a result of intensive studies from this point of view, and detailed studies of various plasma CVD devices and glow discharges used for continuous formation, the inventors found that by forming the surface of the high-frequency application electrode in an uneven manner, They discovered that high-concentration plasma spreads uniformly over the entire electrode, leading to the completion of the present invention. In other words, parallel plate electrodes with large areas have the problem that plasma is localized on the electrode surface as described above, but the present inventors found that when electrodes with a specific surface shape are used, high-density plasma is It was found that the film was formed uniformly over the scratched surface, and this was utilized for high-speed film formation using an in-line film forming apparatus.

[Disclosure of the Invention] The present invention provides an in-line film forming apparatus for forming a thin film on a substrate by setting or advancing a substrate during a glow discharge generated between a high frequency applying electrode and a grounded electrode. The present invention relates to a film forming apparatus characterized in that an electrode surface is formed in an uneven shape.

The in-line film forming apparatus that is the object of the present invention transports a substrate (actually, a substrate held and fixed to a substrate holder) to a film forming chamber without breaking the vacuum, and the substrate is installed in the film forming chamber. Alternatively, it is an apparatus in which a semiconductor thin film is formed while moving and progressing within a room.

FIG. 1 shows a specific embodiment of the present invention in a schematic cross-sectional view.

That is, in an in-line film forming apparatus in which a substrate 4 is placed during a glow discharge generated between a high frequency applying electrode 1 and a ground electrode 2 and a thin film is formed on the substrate, the surface of the liquid high frequency applying electrode is formed in an uneven shape. This is a film-forming device that has been used for many years.

Note that FIG. 2 is a perspective view thereof. Of course, the substrate 4 can be moved and advanced through the glow discharge, and the thin film can be continuously formed on the substrate.

In the present invention, the shape of the unevenness is not particularly limited, but from the viewpoint of manufacturing, it is practical and preferable to make the cross section rectangular because the uniformity of the plasma is not impaired. In addition to what is shown in FIG. 1, FIG. 3 shows some specific examples of uneven shapes of high-frequency applying electrodes having rectangular cross sections.

The height h5 of the ridges in the unevenness of the high-frequency applying electrode as shown in FIG. 1, that is, the depth of the recesses, is 172 or more of the electrode spacing d, preferably the same as or more than d. However, under high-speed film-forming conditions, it is required to increase the pressure during film-forming, so if the peak height h is less than 1/2 of the electrode spacing d, the electrode surface may be uneven. This is not preferable because the effect created by the process becomes smaller. The uniformity of the thin film is also affected by the shape of the device, such as the distance d between the high-frequency applying electrode and the ground electrode and the distance between the high-frequency applying electrode and the substrate. By setting the distance to 1/2 or more of the distance d, preferably the same as or more than d, it is possible to almost eliminate the influence of these device shapes.

On the other hand, the width W of the ridges in the unevenness of the high-frequency applying electrode as shown in FIGS. 1 and 2, that is, the width of the convex portion, is 172 or more of the electrode spacing d, preferably the same as or more than d. However, if the width is too wide, the effect of uniform film formation due to the unevenness of the electrode is small (which is not preferable).

The uniformity of the thin film is also affected by the shape of the device, such as the distance between the high frequency application electrode and the ground electrode and the distance between the high frequency application electrode and the substrate, but by setting the width W of the peak of the high frequency application electrode to 5 cm or less, It is possible to almost eliminate the influence of these device shapes. Furthermore, in this case as well, the distance between the high frequency application electrode, the ground electrode, the substrate, etc. is not limited to ().

Furthermore, the width of the valley in the unevenness of the high frequency application electrode as shown in FIGS. 1 and 2 is 5III11 or more, preferably the same as d or more. In this case, if the electrode surface is too wide, the effect of uniform film formation by forming the electrode surface in an uneven shape will be small (the width is preferably 5 cm or less).

In the present invention, although it is not an essential condition to provide the earth shield 5.5' to the irregularly shaped high frequency application electrode, by providing the earth shield to the high frequency application electrode, it is possible to effectively prevent the discharge from being grounded. It can be oriented towards the electrode side. For this reason, it is preferable to provide a spacing that allows formation of an earth shield. As a specific example, 5
It is sufficient if there is an interval of +a+m or more. Fig. 1 shows a different example.

Regarding the materials of these high frequency application electrodes and grounding electrodes,
Although not particularly limited, considering the amount of impurities imparted to the formed semiconductor thin film, electrical conductivity, thermal stability, etc., stainless steels such as 5US316 and 5US304 may be used.
and aluminum are used as preferred materials.

As described above, the in-line film forming apparatus of the present invention includes a substrate introducing chamber and a substrate unloading chamber, or a substrate introducing chamber that also serves as a substrate unloading chamber, in which the substrate can be transferred to the film forming chamber without breaking the vacuum. Alternatively, it is a film forming apparatus that has at least a substrate introduction means and a substrate ejection means that perform these functions, and a semiconductor thin film is formed on the substrate while the substrate is installed in a film forming chamber or moved within the chamber.

The film forming chamber is a metal reaction vessel equipped with a reaction gas introduction means and an exhaust means, and at least a heating means for heating the substrate, an intermediate high frequency application electrode for generating high-density plasma, and a ground electrode. , a transport means for moving the substrate holder (substrate carrier) is provided. Note that the substrate holder is a transport tool for transporting a substrate on which a semiconductor thin film is formed while fixing it by fitting, installing, or the like. Therefore, as long as the main surface of the substrate is exposed and a thin film can be formed on this surface, there are no limitations on the method of installing the substrate on the substrate carrier. Normally, the substrate holder is the same size as the substrate and the path, or slightly larger than this. The substrate held on the substrate holder is placed in a direction perpendicular to the high frequency application electrode and the opposing ground electrode in a high frequency plasma generated between the high frequency application electrode and the ground electrode,
Alternatively, it moves in that direction, and a semiconductor thin film or the like is formed on the moving substrate.

The material of the reaction vessel is not limited, but preferred materials include stainless steel, nickel and its alloys, aluminum and its alloys. From the viewpoint of handling considering workability and corrosion resistance, it is very easy! , steel (SUS316.5US304) or aluminum and its alloys are preferred.

In the present invention, the material of the substrate is not limited to a glass substrate, a glass substrate with a transparent conductive film such as tin oxide or tin oxide/indium, a ceramic substrate, aluminum, chromium, stainless steel (sus316, 5US3
Metal thin plates such as 04), ceramic substrates with metals such as aluminum, chromium, and stainless steel (SIIS316.5tlS304) vapor-deposited, polymer substrates such as polyethylene terephthalate, stainless steel substrates, and polycrystalline and single-crystalline silicon wafers are effective substrates. used.

The reactive gas used in the present invention is mainly a silicon compound gas, and is a silane represented by the general formula 51hHzn*z (where n is a natural number), such as monosilane and disilane. Furthermore, the general formula SiH+cF<-x (χ is 0
Fluorosilane represented by an integer of ~4), general 2〇〇,
Examples include hydrogenated germane represented by FIzn*t (n is a natural number). Depending on the purpose, phosphine PHx, diborane BJh, helium He1 hydrocarbon gas CyHzy*z, CyHzy -CyHzy~2
(y is a natural number), organic silicon gas such as monomethylsilane, etc. can be used alone or in combination.

[Example] First, a substrate holder is installed in the substrate insertion chamber, and the temperature is set to 0.
The substrate is heated by a heating means until it reaches a predetermined temperature while exhausting to a temperature of 0.01 torr or less. After reaching the predetermined pressure and substrate temperature, a high-frequency electric current i (h = 20 mm, w = 20 mm) is applied to the uneven shape shown in FIG.

201), the substrate was transported while being held in a substrate holder into a reaction chamber in which disilane discharge was being generated, and after being fixed to a ground electrode, an amorphous silicon thin film was formed.

Disilane 10 cc/min High frequency power 5〇1 Substrate temperature 250'C Reaction pressure Q, l torr Electrode dimensions 100 ■ φ Substrate dimensions 20 umbrellas 80111I11 Bottom 1st grade; Average film formation rate 25 A/see substrate Film formation rate distribution above (Figure 4) ±5χ Typical optical conductivity 3.5
Umbrella 10-' S/cm Typical dark conductivity 4.6 Umbrella 1
0-” S/cm [Comparative Example] As a result of forming a film under the same film forming conditions as in the example and using only the electrode as a normal balanced plate type high frequency application electrode, the film forming rate was IIA/sec to 27 A/sec. It was confirmed that uniform film formation was extremely difficult.

[Effects of the Invention] As described above, in the present invention, a film can be formed uniformly on a large-area substrate at a high film-forming rate by using a high-frequency application electrode with irregularities formed on the specific surface defined by the present invention. can do. The properties of the obtained thin film are excellent, and the industrial applicability of the present invention is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a reaction chamber having a high-frequency application electrode with an uneven surface, and FIG. 2 is a perspective view thereof. FIG. 3 is an explanatory diagram showing an example of an embodiment of the uneven shape and arrangement of a high frequency application electrode having a rectangular cross section. Fourth
The figure is an explanatory diagram showing the positions on the substrate where the film deposition rate distribution was measured in the example. Measurement points were provided at intervals of 5111 inches passing through the center of the rectangle and parallel to the long sides. In the figure, 1-.
・−・−・−・−Heater, 4−・・−・−・−・One board, 5.5′・・−・−・・−・・Earth shield, h
−・−−−−−1・−・−Height of the mountain in unevenness,
w −−−−−−−−−・−・−Width of the mountain in unevenness,
L ----------・---m---・Width of valley in unevenness

Claims (1)

[Claims] (1) In an in-line film forming apparatus that places or advances a substrate to form a thin film on the substrate during glow discharge that occurs between a high-frequency applying electrode and a grounded electrode, the surface of the high-frequency applying electrode is uneven. A film forming apparatus characterized in that: