JP7547147B2 - Film forming tray and solar cell manufacturing method - Google Patents

Description

The present invention relates to a film forming tray and a solar cell manufacturing method.

In the manufacture of semiconductor devices, a semiconductor substrate may be placed on a tray and a film may be formed on the upper surface of the semiconductor substrate (see, for example, Patent Document 1). In the manufacture of solar cells, a tray may be used to hold the semiconductor substrate in order to form an anti-reflective film on the surface of the semiconductor substrate (the surface on which light is incident). When a film is formed on the semiconductor substrate placed on the tray, a film is also formed on the edge surface of the semiconductor substrate. In solar cells, light emission from the edge surface of the semiconductor substrate can reduce the photoelectric conversion efficiency, so it is considered preferable to form an anti-reflective film on the edge surface of the semiconductor substrate as well.

JP 2008-159893 A

A detailed examination of a solar cell that was placed on a conventional film-forming tray and had an anti-reflective film formed on the semiconductor substrate confirmed that film formation on the edge of the semiconductor substrate was insufficient, and that light still emitted from the outer periphery of the semiconductor substrate, reducing the photoelectric conversion efficiency. Therefore, the objective of the present invention is to provide a film-forming tray and a solar cell manufacturing method that can manufacture solar cells that emit less light.

A film formation tray according to one aspect of the present invention includes a support portion that supports the underside of a substrate, a plurality of positioning portions that position the substrate in a planar direction, and a recessed portion that is formed on the outside of the support portion and forms a lower space that is open to the outside of the substrate below the outer periphery of the substrate.

In the film formation tray according to the present invention, the recessed portion may be a groove extending along the outer periphery of the substrate and increasing in width toward the upper side.

In the film forming tray according to the present invention, the recessed portion may be V-groove-shaped.

The film forming tray according to the present invention may further include an inclined surface formed along the outside of the recessed portion and inclined from the upper outside toward the recessed portion.

In the film forming tray of the present invention, the inclined surface may be a flat surface that is smoothly connected to the outer surface of the recessed portion.

In the film formation tray of the present invention, the positioning portion may regulate the positions of the four corners of the substrate.

The recessed portion does not have to be formed below the portion of the substrate that is restricted by the positioning portion.

A solar cell manufacturing method according to one aspect of the present invention includes a step of forming an anti-reflective film on the substrate using the film-forming tray.

The film formation tray and solar cell manufacturing method of the present invention make it possible to manufacture solar cells that emit little light.

FIG. 2 is a plan view showing a film formation tray according to the first embodiment of the present invention. 2 is an enlarged cross-sectional view of the film formation tray shown in FIG. 1 taken along line AA. 2 is an enlarged cross-sectional view of the film formation tray shown in FIG. 1 along line BB. FIG. 11 is an enlarged cross-sectional view of an end portion of a film formation tray according to a second embodiment of the present invention. FIG. 11 is an enlarged cross-sectional view of an end portion of a film formation tray according to a third embodiment of the present invention.

Embodiments of the present invention will be described below with reference to the drawings. For convenience, hatching and component symbols may be omitted. In such cases, other drawings should be referenced. Also, the dimensions of various components in the drawings have been adjusted for ease of viewing.

First Embodiment
Fig. 1 is a plan view of a film formation tray 1 according to a first embodiment of the present invention. Fig. 2 is an enlarged cross-sectional end view of the film formation tray 1 taken along line A-A in Fig. 1. Fig. 3 is an enlarged cross-sectional end view of the film formation tray 1 taken along line B-B in Fig. 1.

The film-forming tray 1 of this embodiment holds the substrate P inside the film-forming apparatus. The substrate P on which a film is formed using the film-forming tray 1 is typically a semiconductor substrate on which a solar cell is formed, and may have a pn junction, electrodes, etc. formed on the front and back sides. A typical example of the film that is laminated on the substrate P using the film-forming tray 1 is an anti-reflective film.

The film-forming tray 1 is formed by arranging multiple holding parts 10 vertically and horizontally, each holding one substrate P. Each holding part 10 of the film-forming tray 1 is provided with a support part 11 that supports the lower surface of the substrate P, multiple positioning parts 12 that regulate the planar position of the substrate P, a recessed part 13 formed on the outside of the support part 11 and forming a lower space S that is open to the outside of the substrate P below the outer periphery of the substrate P, and an inclined surface 14 formed along the recessed part 13 on the outside of the recessed part 13 and inclined from the upper outside toward the recessed part 13.

The film formation tray 1 can be made of a metal such as aluminum, an aluminum alloy, or stainless steel. In particular, by making the film formation tray 1 out of a metal such as aluminum that has a relatively low specific heat and high thermal conductivity, the film formation quality can be improved.

The support portion 11 has a planar mounting surface 111 at its upper end that is in substantially continuous contact with the underside of the substrate P and can prevent the deposition gas from entering the central underside of the substrate P. As a specific example, the mounting surface 111 may have protrusions, for example, several tens of μm in height, and be configured to support the substrate P with a relatively small contact area and form minute gaps in other areas that substantially prevent the deposition gas from penetrating.

The mounting surface 111 may be formed over the entire support part 11 in plan view, but is formed at least in the area near the outer periphery of the support part 11. By making the height of the outer periphery of the support part 11 slightly larger and forming the mounting surface 111 partially, the machining accuracy of the parts other than the mounting surface can be reduced.

The positioning portions 12 each have a restricting portion 121 that can come into contact with the outer edge of the substrate P. The restricting portion 121 is preferably a surface perpendicular to the placement surface 111 so that the planar position of the substrate P can be accurately restricted. The film formation tray 1 of this embodiment has four positioning portions 12 that restrict the positions of the four corners of the substrate P. In this way, a film cannot be formed on the portion of the substrate P where the restricting portion 121 comes into contact, but by abutting the restricting portion 121 against the four corners of the substrate P where the internal light is relatively difficult to reach, the amount of light emitted from that portion can be reduced even if a film cannot be formed on that portion.

The recessed portion 13 supplies film formation gas to the underside of the outer periphery of the substrate P by forming a lower space S below the four sides of the substrate P. However, since the amount of film formation gas supplied from the recessed portion 13 is less than the amount of film formation gas supplied to the upper surface of the substrate P, the thickness of the film formed from the edge surface of the substrate P to the rear end portion gradually decreases.

It is preferable that the dug portion 13 is groove-shaped with a width that increases toward the upper side. This allows the deposition gas to be efficiently guided to the underside of the substrate P. The dug portion 13 can be formed relatively easily by making it a V-groove formed by an inner surface 131 and an outer surface 132, as in this embodiment. The base angle of the V-groove-shaped dug portion 13 is preferably 90° or more in order to efficiently guide the deposition gas. Furthermore, if the base angle of the V-groove-shaped dug portion 13 is approximately 90°, the dug portion 13 can be formed more easily, for example, by an end mill.

In this embodiment, the recessed portion 13 is not formed in the portion where the positioning portion 12 is provided. In other words, in this embodiment, the recessed portion 13 is not formed near the four corners of the substrate P. This makes the shape of the recessed portion 13 simpler, and therefore the recessed portion 13 can be formed even more easily.

The average overlap width of the recessed portion 13 with the substrate P in plan view can be, for example, 0.2 mm to 2.0 mm, and preferably 0.5 mm to 1.0 mm. By setting the average overlap width of the recessed portion 13 with the substrate P to be equal to or greater than the lower limit, a lower space S can be formed below the substrate P regardless of positioning errors of the substrate P. Furthermore, by setting the average overlap width of the recessed portion 13 with the substrate P to be equal to or less than the upper limit, it is possible to prevent more film than necessary from being formed on the rear surface of the substrate P.

The average width of the recessed portion 13 (the outer edge of the recessed portion 13 is the intersection with the extended surface of the mounting surface 111) is preferably 2 mm to 8 mm, and more preferably 3 mm to 5 mm. By making the average width of the recessed portion 13 equal to or greater than the lower limit, the lower space S can be more reliably opened to the outer space. Furthermore, by making the average width of the recessed portion 13 equal to or less than the upper limit, the holding portion 10 is prevented from becoming unnecessarily large, and the number of substrates P that can be processed simultaneously on one film formation tray 1 can be increased.

The inclined surface 14 guides the film formation gas to the recessed portion 13, thereby promoting film formation on the rear end side of the substrate P. For this reason, it is preferable that the inclined surface 14 is smoothly connected to the outer surface 132 of the recessed portion 13. In particular, if the inclined surface 14 and the outer surface 132 of the recessed portion 13 are continuous and planar, as in this embodiment, the inclined surface 14 can be easily formed simultaneously with the outer surface 132.

The inclined surface 14 forms a ridge-like protrusion between the holding parts 10, which also contributes to improving the strength of the film formation tray 1. This allows the thickness of the support part 11 to be reduced, making the film formation tray 1 lighter.

The inclination angle of the inclined surface 14 relative to the mounting surface 111 can be, for example, 30° or more and 60° or less. This allows the deposition gas to be guided relatively efficiently to the recessed portion 13.

The height of the inclined surface 14 (vertical height from the mounting surface 111) can be, for example, 0.5 mm or more and 3 mm or less. This makes it possible to guide the film formation gas to the recessed portion 13 while preventing the height of the film formation tray 1 from becoming unnecessarily large.

As described above, by using a film-forming tray 1 that forms a lower space S that allows the film-forming gas to flow around to the back side of the substrate P, it is possible to perform continuous film formation on the front surface, outer peripheral edge, and outer edge of the back surface of the substrate P. Since the amount of film-forming gas supplied to the outer peripheral edge and outer edge of the back surface of the substrate P may be smaller than that for film formation on the front surface, the film formed from the outer peripheral edge to the back surface of the substrate P may gradually become thinner from the front surface, but a coating with sufficient thickness can be formed at least on the outer peripheral edge.

Therefore, by using the film-forming tray 1 to form an anti-reflective film on the semiconductor substrate for a solar cell, it is possible to prevent light from emitting from the end face and manufacture a solar cell with high photoelectric conversion efficiency. In this way, a solar cell manufacturing method that includes a step of forming an anti-reflective film on the substrate P using the film-forming tray 1 can be understood as one embodiment of the solar cell manufacturing method according to the present invention.

To explain in more detail, in the solar cell manufacturing method according to the present invention, the substrate P is placed on the support portion 11 of the film-forming tray 1 with its planar position determined by a plurality of positioning portions 12. The film-forming tray 1 on which the substrate P is placed is then placed in a vacuum chamber of a CVD or PVD device, and a film-forming gas is supplied to form an anti-reflective film on the top surface, edge surface, and rear outer edge portion of the substrate P.

The substrate P for forming the solar cell is a single photoelectric conversion substrate that absorbs incident light to generate photocarriers (electrons and holes), and a crystalline silicon substrate such as crystalline silicon or polycrystalline silicon can be used. In addition, before forming the anti-reflection film, various components such as a semiconductor layer that forms a pn junction for collecting carriers, an electrode for collecting electric charge, a passivation layer that suppresses recombination of carriers, and an insulating layer that separates the components may be formed on the substrate P.

The anti-reflection film is a layer that re-reflects light inward on the surface of the substrate P so that the light that enters the substrate P is not reflected internally and emitted to the outside. Examples of materials that can be used for the anti-reflection film include SiO, SiN, and SiON.

Second Embodiment
4 is a cross-sectional view of a film formation tray 1A according to a second embodiment of the present invention. In the following embodiments, the same components as those in the previously described embodiments are denoted by the same reference numerals, and duplicated descriptions may be omitted.

The film forming tray 1 includes a support portion 11 that supports the lower surface of the substrate P, a number of positioning portions (not shown) that regulate the planar position of the substrate P, a recessed portion 13A formed on the outside of the support portion 11 and forming a lower space that is open to the outside of the substrate P below the outer periphery of the substrate P, and an inclined surface 14A formed on the outside of the recessed portion 13A along the recessed portion 13A and inclined from the upper outside toward the recessed portion 13A.

In this embodiment, the recessed portion 13A is formed in a rectangular groove shape having vertical inner and outer surfaces 131 and 132 and a bottom surface 133 connecting the lower ends of these surfaces. Even with the recessed portion 13A having such a shape, it is possible to form a film that completely covers the edge of the substrate P by directing the film forming gas to the back side of the outer edge of the substrate P.

In this embodiment, the inclined surface 14A is formed at a distance from the outer surface 132. In this way, even if the inclined surface 14A and the recessed portion 13A are not continuous, the deposition gas can be guided to the back side of the outer edge portion of the substrate P.

Third Embodiment
5 is a cross-sectional view of a film formation tray 1B according to a third embodiment of the present invention. The film formation tray 1B of this embodiment includes a support portion 11, a plurality of positioning portions (not shown), a recessed portion 13B formed outside the support portion 11 and forming a lower space below the outer periphery of the substrate P that is open to the outside of the substrate P, and an inclined surface 14B formed outside the recessed portion 13B along the recessed portion 13B and inclined from the upper outside toward the recessed portion 13B.

In this embodiment, the recessed portion 13B is formed in a semicircular groove shape. In addition, the inclined surface 14B in this embodiment is formed in a cylindrical surface shape so that the inclination angle decreases toward the recessed portion 13B. Such recessed portion 13B and inclined surface 14B can each be formed using, for example, a ball end mill.

The above describes an embodiment of the present invention, but the present invention is not limited to the above embodiment and various modifications and variations are possible.

For example, in the film formation tray according to the present invention, the inclined surface may be omitted. Furthermore, the shape of the inclined surface may be any shape that slopes overall toward the recessed portion, and may be, for example, stepped.

In addition, in the film formation tray according to the present invention, the cross-sectional shape of the recessed portion is not limited to the shape of the above-mentioned embodiment, and may be, for example, trapezoidal, parabolic, stepped, etc. In addition, the recessed portion of the film formation tray according to the present invention may be formed integrally with the recessed portion of the adjacent holding portion. In this case, an inclined surface cannot be provided.

In addition to forming anti-reflective films for solar cells, the film-forming tray of the present invention can also be used in a wide range of applications when it is necessary to form a thin film that covers one of the main surfaces and end surfaces of a substrate.

In addition, in the film formation tray according to the present invention, the positioning portion may be capable of positioning the substrate by locally contacting a portion of the four sides of the substrate.

Reference Signs List 1, 1A, 1B Film formation tray 10 Holding portion 11 Support portion 111 Placement surface 12 Positioning portion 121 Regulating portion 13, 13A, 13B Depression portion 131 Inner surface 132 Outer surface 133 Bottom surface 14, 14A, 14B Inclined surface P Substrate S Lower space

Claims (6)

A support portion that supports a lower surface of the substrate;
A plurality of positioning portions that regulate a position of the substrate in a planar direction;
a recessed portion formed outside the support portion and defining a lower space open to the outside of the substrate below an outer periphery of the substrate;
Equipped with
the positioning portion regulates the positions of the four corners of the substrate,
The recessed portion is formed in a portion of the substrate excluding the vicinity of each of the four corners of the substrate . The film forming tray according to claim 1, wherein the recessed portion is a groove whose width increases toward the upper side. The film forming tray according to claim 2, wherein the recessed portion is a V-groove. The film forming tray according to any one of claims 1 to 3, further comprising an inclined surface formed along the hollow portion on the outside of the hollow portion and inclined from the upper outside toward the hollow portion. The film forming tray of claim 4, wherein the inclined surface is smoothly connected to the outer surface of the recessed portion. A solar cell manufacturing method, comprising: forming an anti-reflective film on the substrate by using the film formation tray according to claim 1 .

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