JP2667665B2 - Film forming equipment - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film forming apparatus for continuously forming a thin film by glow discharge, and more particularly, to a method for forming a high performance semiconductor thin film uniformly and continuously at a high film forming rate. The present invention relates to a film forming apparatus for forming a film. [Prior Art] An amorphous silicon-based semiconductor thin film obtained by glow discharge decomposition or photodecomposition of a silicon compound has excellent photo-electric energy conversion ability and is used as a photovoltaic element. In addition, the use as not only consumer electronic devices such as calculators but also solar cells for electric power is being studied. For this purpose, it is necessary to manufacture large-area solar cells at low cost. Also in this regard, the area of the amorphous silicon-based solar cell is basically relatively easy to expand, and research on increasing the area is being conducted. However, in a conventional film forming apparatus using a capacitively coupled parallel plate electrode, there are some problems when forming a high-performance semiconductor thin film uniformly and continuously 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 placed between an electrode to which a high frequency is applied (a high-frequency application electrode) and an electrode that is grounded (a ground electrode). In this case, the uniformity of the thin film cannot be obtained unless uniformity of the glow discharge is secured in the surface of the high frequency application electrode. Next, when a film is formed on a large-area substrate, the area of the high-frequency application electrode must be larger than that of the substrate, as a matter of course. Therefore, the high-frequency current cannot be effectively introduced. In addition, as a result of the edge effect based on the lines of electric force and the skin effect, the glow discharge around the high-frequency application electrode becomes strong, and not only the film forming rate becomes non-uniform, but also the characteristics of the obtained thin film become poor. In addition to the non-uniformity, the glow discharge in the periphery of the high-frequency application electrode becomes stronger under high-speed film formation conditions, and this problem is further emphasized. [Object of the Invention] An object of the present invention is to generate a high-concentration plasma between a high-frequency application electrode and a ground electrode, and to form a uniform semiconductor thin film continuously on a substrate at a high deposition rate. Is to provide a so-called in-line film forming apparatus. [Basic idea] The inventors of the present invention have made intensive studies from such a viewpoint, and as a result of detailed studies of various plasma CVD apparatuses and glow discharges used for continuous formation, have found that the length of the high-frequency application electrode in the direction of travel of the substrate. It was found that by making the value shorter than a certain value, the high-concentration plasma spread uniformly over the entire electrode, and the present invention was completed. That is, in the case of a large-area parallel plate electrode, there is a problem that plasma is localized on the electrode surface as described above. It has been found that the film is uniformly formed on the entire surface of the electrode, and this is used for high-speed film formation by an in-line film forming apparatus. [Disclosure of the Invention] The present invention provides an in-line component for continuously forming a thin film on a substrate by advancing a substrate held by a substrate holder during a glow discharge generated between a high-frequency application electrode and a ground electrode. In the membrane device, the length of the high-frequency application electrode in the traveling direction of the substrate is shorter than the length of the substrate holder in the traveling direction,
The present invention also relates to a film forming apparatus characterized by a narrow electrode in a range of 0.5 cm to 10 cm, and more preferably, to a film forming apparatus in which a plurality of high frequency applying electrodes are arranged in parallel. The in-line film forming apparatus to which the present invention is applied transfers a substrate (actually, a substrate held and fixed by a substrate holder) to a film forming chamber without breaking vacuum, and moves the substrate in the film forming chamber. This is an apparatus in which a semiconductor thin film is formed as it proceeds. The length L of the high-frequency application electrode in the traveling direction of the substrate is specifically 10 cm or less, preferably 5 cm or less. When it exceeds 10 cm, the plasma at the center and the end of the electrode loses uniformity. As a result, the deposition rate becomes non-uniform, and the thickness of the obtained thin film becomes non-uniform. In particular, this non-uniformity has been remarkable under high-speed film forming conditions required to increase the pressure during film formation. 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. By setting the range, especially 0.5 to 5 cm, the influence of these device shapes is almost eliminated. FIG. 1 and FIG. 2 show a specific embodiment showing one embodiment of the present invention. FIG. 1 is a schematic sectional view, and FIG. 2 is a perspective view thereof. That is, during the glow discharge generated between the high-frequency application electrode 1 and the ground electrode 2, in an in-line film forming apparatus that advances a substrate held by the substrate holder 5 and continuously forms a thin film on the substrate, The height L of the high-frequency applying electrode in the traveling direction of the substrate is the length l of the substrate holder 5 in the traveling direction.
This is a film forming apparatus which is a shorter electrode and is a narrow electrode in the range of 0.5 cm to 10 cm. In the present invention, the high frequency applying electrodes 1, 1 ', 1 "...
Can be used simultaneously. In this case, the intervals 1 to 1 ', 1' to 1 "between the high frequency applying electrodes,...
… Is not particularly limited. The provision of the earth shield 6 on the high-frequency applying electrode 1 enables the discharge to be effectively directed to the opposite grounding distance side. For this reason, the interval between the electrodes at which the earth shield can be formed is reduced. It is preferred to take. Therefore, as a specific example, it is sufficient that there is an interval of at least 5 mm or more. It is preferable that a plurality of high-frequency application electrodes are arranged in parallel as shown in the figure. The shape of the ground electrode is not an essential requirement in the present invention, but is preferably the same as the high-frequency application electrode from the viewpoint of plasma stability. That is, a narrow electrode in which the length of the substrate in the traveling direction is shorter than the length in the direction perpendicular to the traveling direction is preferable. The material of the high-frequency application electrode and the ground electrode is not particularly limited, but in consideration of the amount of impurities given to the semiconductor thin film to be formed, electric conductivity, thermal stability, etc. SUS314 and aluminum are used as preferred materials. With the in-line film forming apparatus of the present invention, as described above,
A substrate introduction chamber and a substrate removal chamber capable of transporting a substrate to a film formation chamber without breaking a vacuum, or a substrate introduction chamber also serving as a substrate removal chamber, or at least a substrate introduction means or a substrate removal means performing these functions. This is an apparatus for forming a semiconductor thin film while moving a substrate. The film formation chamber is a metal reaction vessel provided with a reaction gas introduction unit and an exhaust unit, and includes at least a heating unit for heating the substrate, a narrow high-frequency application electrode for generating high-density plasma, and a ground electrode. In addition, transport means for moving the substrate holder (substrate carrier) is provided. In the present invention, the substrate holder is a carrier for fixing and transporting a substrate on which a semiconductor thin film is to be formed by fitting, setting, 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 is no limitation on the method of installing the substrate on the substrate carrier. Usually, the substrate holder is generally the same size as the substrate or slightly larger than this. As shown by the arrow in FIG. 1, the substrate held on the substrate holder passes through the high-density plasma generated between the high-frequency application electrode and the ground electrode with respect to the high-frequency application electrode and the opposite ground electrode. The semiconductor thin film and the like are formed on the moving substrate. The material of the substrate holder is stainless steel in consideration of the amount of impurities given to the semiconductor thin film to be formed, electric conductivity, thermal stability, and the like.
SUS316, SUS304 and aluminum are preferred materials. In the figure, reference numeral 3 denotes a plasma control electrode, which is also preferably installed to suppress unnecessary spread of plasma. The material of the reaction vessel is not limited, but preferred materials include stainless steel, nickel and its alloys, aluminum and its alloys, and the like. From the viewpoint of handling in consideration of workability and corrosion resistance, stainless steel (SUS316, SUS304) or aluminum and alloys thereof are preferable. In the present invention, the material of the substrate is not limited. Glass substrates include glass substrates with transparent conductive films such as tin oxide and tin oxide / indium, ceramic substrates, metal thin films such as aluminum, chromium, and stainless steel (SUS316, SUS304), and aluminum, chromium, and stainless steel (SU
Ceramic substrates on which metals such as S316, SUS304) are deposited, polymer substrates such as polyethylene terephthalate, stainless steel substrates, polycrystalline and single-crystal silicon wafers, etc. are effectively used as substrates. The reactive gas used in the present invention is mainly a silicon compound gas, and is a silane represented by the general formula Si _n H _{2n + 2} (where n is a natural number), for example, monosilane and disilane. Moreover, (the x, an integer of 0 to 4) general formula SiH _x F _4-x fluorosilane represented by the general formula Ge _n H _{2n + 2 (n} is a natural number) and the like hydrogenated germane represented by. Also, depending on the purpose, phosphine PH _3, diborane B ₂ H _6, helium He, hydrocarbon gas _{C y H 2y + 2, C} y H 2y, C y H 2y-2 (y is a natural number), monomethyl silane And the like can be used alone or in combination. [Example] First, a substrate holder made of SUS304 was installed in the substrate insertion chamber,
The substrate is heated to a predetermined temperature by a heating means while evacuating to 0.01 torr or less in a vacuum system. After reaching a predetermined pressure and substrate temperature, the shape shown in FIG. 1 becomes narrow (L = 30).
mm) high-frequency application electrodes 1 are arranged in parallel in five or more rows at 50 mm intervals, and a 300 × 500 mm substrate holder in which a 250 × 500 mm glass substrate is fitted in a reaction chamber where disilane discharge is generated. Was transported to the transporting means, and an amorphous silicon thin film was formed while passing through the reaction chamber. Deposition conditions: Disilane 20cc / min High frequency power 60W Substrate temperature 300 ° C Reaction pressure 0.6torr Electrode size 30 * 300mm Substrate size 250 * 500mm Deposition result; Average deposition rate 25A / sec Film speed distribution ± 5% Typical photoconductivity 3.5 * 10 ^-5 S / cm Typical dark conductivity 4.6 * 10 ^-11 S / cm [Comparative example] As a result of changing only the dimensions to wide (L = 150 mm), that is, 150 * 300 mm, it was confirmed that the film formation speed varied between 11 A / sec and 27 A / sec, and uniform film formation was extremely difficult. [Effects of the Invention] As described above, in the present invention, a uniform film can be formed uniformly on a large-area substrate at a high film forming rate by using the specific narrow high-frequency application electrode defined in the present invention. it can. The properties of the obtained thin film are excellent, and the industrial applicability of the present invention is extremely large.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional view of a reaction chamber having a narrow high-frequency application electrode, and FIG. 2 is a perspective view likewise. FIG. 3 is an explanatory view showing a position on a substrate at which a film deposition rate distribution is measured in the embodiment of the present invention. In this case, measurement points were provided at 0.5 cm intervals on a diagonal line. In the figure, 1 ... high-frequency application electrode, 2 ... ground electrode,
3 ... plasma control electrode, 4 ... heater, 5 ... substrate holder, 6 ... earth shield, L ... electrode width in substrate traveling direction

Claims (1)

(57) [Claims] During the glow discharge generated between the high-frequency application electrode and the ground electrode, the substrate held by the substrate holder is advanced to continuously form a thin film on the substrate. Proceeding between the electrode and the ground electrode, the length of the high-frequency application electrode in the direction of travel of the substrate is shorter than the length of the substrate holder in the direction of travel, and 0.5 cm
A film forming apparatus comprising: a narrow electrode having a width of about 10 cm; and an earth shield provided between the high-frequency applying electrodes to effectively direct discharge toward the ground electrode. 2. 2. The apparatus according to claim 1, wherein a plurality of high-frequency application electrodes are arranged in parallel.