KR102397999B1 - Solar cell and method for manufacturing the same - Google Patents

Abstract

A method of manufacturing a solar cell according to an embodiment of the present invention includes forming a control passivation film on one surface of a semiconductor substrate; forming a first conductivity type region including a first conductivity type dopant on the control passivation layer; and forming a first electrode connected to the first conductivity-type region. The forming of the first conductivity type region may include: forming an intrinsic semiconductor layer; forming a first dopant layer including the first conductivity type dopant on the intrinsic semiconductor layer; and a doping process of doping the intrinsic semiconductor layer with the first conductivity-type dopant included in the first dopant layer using a defocused laser.

Description

Solar cell and manufacturing method thereof

The present invention relates to a solar cell and a method for manufacturing the same, and more particularly, to a solar cell including a conductive region including a semiconductor material and a method for manufacturing the same.

Recently, as existing energy resources such as oil and coal are expected to be depleted, interest in alternative energy to replace them is increasing. Among them, a solar cell is spotlighted as a next-generation battery that converts solar energy into electrical energy.

In such a solar cell, various layers and electrodes can be manufactured according to design. The design of these various layers and electrodes can determine solar cell efficiency. In order to commercialize the solar cell, it is necessary to overcome the low efficiency. Therefore, various layers and electrodes are required to be designed and manufactured to maximize the efficiency of the solar cell.

A solar cell in which a conductive region is formed as a layer separate from a semiconductor substrate has been proposed. In such a solar cell, it may be difficult for carriers to move to the conductive region. In particular, when another layer is located between the conductive region and the semiconductor substrate, the problem may be further exacerbated by the discontinuous energy band diagram.

An object of the present invention is to provide a solar cell having excellent efficiency and productivity and a method for manufacturing the same.

A method of manufacturing a solar cell according to an embodiment of the present invention includes forming a control passivation film on one surface of a semiconductor substrate; forming a first conductivity type region including a first conductivity type dopant on the control passivation layer; and forming a first electrode connected to the first conductivity-type region. The forming of the first conductivity type region may include: forming an intrinsic semiconductor layer; forming a first dopant layer including the first conductivity type dopant on the intrinsic semiconductor layer; and a doping process of doping the intrinsic semiconductor layer with the first conductivity-type dopant included in the first dopant layer using a defocused laser.

A solar cell according to an embodiment of the present invention includes: a semiconductor substrate; a control passivation film formed on one surface of the semiconductor substrate; a first conductivity type region formed on the control passivation layer and including a first conductivity type dopant; and a first electrode connected to the first conductivity type region. A first diffusion region having the first conductivity type dopant is formed in a portion of the semiconductor substrate corresponding to the first conductivity type region. The control passivation layer is positioned between the first conductivity type region and the first diffusion region and includes a first doped portion including the first conductivity type dopant. The doping profile has a doping profile in which the doping concentration of the first conductivity-type dopant is continuously decreased toward the first conductivity-type region, the control passivation layer, and the first diffusion region. Here, the control passivation layer or a portion of the first conductivity type region adjacent thereto has a first doping profile, and a portion of the first diffusion region adjacent to the control passivation layer has a second doping profile different from the first doping profile have An absolute value of the second concentration gradient of the second doping profile is less than an absolute value of the first concentration gradient of the first doping profile.

According to the present embodiment, by forming a diffusion region in the semiconductor substrate corresponding to the conductive region, the open-circuit voltage and filling density of the solar cell can be improved, thereby improving the efficiency of the solar cell. In addition, a diffusion region having a desired doping profile and thickness can be formed by a simple process. Thereby, the manufacturing method of the solar cell with excellent efficiency can be simplified, and productivity can be improved.

1 is a cross-sectional view illustrating a solar cell according to an embodiment of the present invention.
FIG. 2 is a partial rear plan view of the solar cell shown in FIG. 1 .
3 (a) is an energy band diagram of a solar cell according to the present embodiment, and (b) is an energy band diagram of a solar cell without a diffusion region.
FIG. 4 is a graph illustrating doping profiles of a first conductivity type region, a first doped portion, and a first diffusion region in the solar cell shown in FIG. 1 .
5A to 5H are cross-sectional views illustrating a method of manufacturing a solar cell according to an embodiment of the present invention.
FIG. 6 schematically shows a shape of a laser beam formed on a first dopant layer by a doping process included in the method for manufacturing a solar cell shown in FIG. 5D , and (a) is a laser beam when a focused laser is used. The shape of (b) is the shape of the laser beam when a defocused laser is used.
7 is a schematic diagram illustrating an example of a doping process included in the method of manufacturing the solar cell shown in FIG. 5D .
8 is a schematic diagram illustrating another example of a doping process included in the method of manufacturing the solar cell illustrated in FIG. 5D .
9 is a cross-sectional view illustrating a solar cell according to another embodiment of the present invention.
FIG. 10 is a plan view of the solar cell shown in FIG. 9 .

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it goes without saying that the present invention is not limited to these embodiments and may be modified in various forms.

In the drawings, in order to clearly and briefly describe the present invention, the illustration of parts irrelevant to the description is omitted, and the same reference numerals are used for the same or extremely similar parts throughout the specification. In addition, in the drawings, the thickness, width, etc. are enlarged or reduced in order to make the description more clear, and the thickness, width, etc. of the present invention are not limited to the bars shown in the drawings.

And, when a certain part "includes" another part throughout the specification, other parts are not excluded unless otherwise stated, and other parts may be further included. Also, when a part such as a layer, film, region, plate, etc. is said to be “on” another part, it includes not only the case where the other part is “directly on” but also the case where another part is located in the middle. When a part, such as a layer, film, region, or plate, is "directly above" another part, it means that no other part is located in the middle.

Hereinafter, a solar cell and a method of manufacturing the same according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view illustrating a solar cell according to an embodiment of the present invention, and FIG. 2 is a partial rear plan view of the solar cell shown in FIG. 1 .

1 and 2 , the solar cell 100 according to the present embodiment includes a semiconductor substrate 10 and a dopant-controlled passivation film (hereinafter, referred to as “rear surface”) formed on one surface (hereinafter “rear surface”) of the semiconductor substrate 10 . "control passivation film") 20 , a first conductivity type region 32 positioned over the control passivation film 20 and having a first conductivity type, and a first electrically connected to the first conductivity type region 32 . electrode 42 . Here, a second conductivity type region 34 having a second conductivity type opposite to the first conductivity type and a second electrode 44 electrically connected to the second conductivity type region 34 may be further included. In addition, the solar cell 100 is positioned on the semiconductor layer 30 including the front passivation film 24 and the anti-reflection film 26 and the conductive regions 32 and 34 positioned on the front surface of the semiconductor substrate 10 . A back passivation layer 40 may be further included. This will be described in more detail.

The semiconductor substrate 10 may include the base region 110 having the first or second conductivity type by including the first or second conductivity type dopant at a relatively low doping concentration. For example, the base region 110 may have the second conductivity type. The base region 110 may be formed of a crystalline semiconductor (eg, a single crystal or polycrystalline semiconductor, for example, single crystal or polycrystalline silicon, particularly single crystal silicon) including a first or second conductivity type dopant. As described above, the solar cell 100 based on the base region 110 or the semiconductor substrate 10 having few defects due to its high crystallinity has excellent electrical characteristics.

In the present embodiment, the front electric field region 130 is positioned on the front side of the semiconductor substrate 10 . The front electric field region 130 is a doped region having the same first or second conductivity type (eg, second conductivity type) as the base region 110 and having a higher doping concentration than the base region 110 , and is a semiconductor substrate. It may constitute a part of (10).

In addition, an anti-reflection structure capable of minimizing reflection may be formed on the front surface of the semiconductor substrate 10 . For example, as an anti-reflection structure, a texturing structure having irregularities in the shape of a pyramid or the like may be provided. The texturing structure formed on the semiconductor substrate 10 may have a predetermined shape (eg, a pyramid shape) having an outer surface formed along a specific crystal plane (eg, (111) plane) of the semiconductor. When unevenness is formed on the front surface of the semiconductor substrate 10 by such texturing and the surface roughness is increased, the reflectance of light incident through the front surface of the semiconductor substrate 10 may be lowered to minimize light loss.

In addition, the rear surface of the semiconductor substrate 10 may be formed of a relatively smooth and flat surface having a lower surface roughness than the front surface by mirror polishing or the like. In the case where the first and second conductivity-type regions 32 and 34 are formed together on the rear surface of the semiconductor substrate 10 as in the present embodiment, the characteristics of the solar cell 100 according to the characteristics of the rear surface of the semiconductor substrate 10 . Because this can make a big difference. Accordingly, the passivation characteristic may be improved by not forming unevenness due to texturing on the rear surface of the semiconductor substrate 10 , thereby improving the characteristics of the solar cell 100 . However, in some cases, irregularities may be formed on the rear surface of the semiconductor substrate 10 by texturing. Various other modifications are also possible.

A control passivation layer 20 may be formed on the rear surface of the semiconductor substrate 10 . For example, the control passivation layer 20 may be formed entirely in contact with the rear surface of the semiconductor substrate 10 . Then, the control passivation film 20 can be easily formed without patterning, the structure can be simplified, and carriers can be stably moved.

The control passivation film 20 positioned between the semiconductor substrate 10 and the conductive regions 32 and 34 serves as a dopant control to prevent excessive diffusion of dopants in the conductive regions 32 and 34 into the semiconductor substrate 10 . Alternatively, it may serve as a diffusion barrier. The control passivation layer 20 may include various materials capable of controlling diffusion of dopants and transporting majority carriers, and may include, for example, oxides, nitrides, semiconductors, conductive polymers, and the like.

For example, the control passivation layer 20 may be a dielectric layer or an insulating layer including a dielectric material having a dielectric constant above a certain level to enable carriers to move. As described above, having a certain level of permittivity allows carriers to easily move or pass through because a polarization phenomenon occurs when an electric field is applied. The control passivation film 20 may be formed of an oxide film, a dielectric film or insulating film containing silicon, a nitride oxide film, a carbide oxide film, or the like. For example, the control passivation film 20 may be formed of a metal oxide film, a silicon oxide film, a silicon nitride film, a silicon nitride oxide film, a metal nitride oxide film, a silicon carbide oxide film, or the like. In this case, the metal included in the metal oxide layer or the metal nitride oxide layer may be aluminum, titanium, hafnium, or the like. As such, when the metal is included, the control passivation film 20 may be formed of an aluminum oxide film, a titanium oxide film, a hafnium oxide film, an aluminum nitride oxide film, a titanium nitride oxide film, a hafnium nitride oxide film, or the like.

For example, the control passivation layer 20 may be a silicon oxide layer including silicon oxide. This is because the silicon oxide film has excellent passivation properties and is a film in which carrier transport is smooth. In addition, the silicon oxide film may be easily formed on the surface of the semiconductor substrate 10 by various processes. At this time, in the present embodiment, the control passivation layer 20 composed of a silicon oxide layer is formed under specific process conditions, so that the dopant can be smoothly moved through the control passivation layer 20 . Specific process conditions for this will be described in more detail later. As described above, the chemical formula of the silicon oxide film formed under specific process conditions may be SiOx, and x may be 1.1 or more (1.1 to 2.0). In addition, the refractive index of the silicon oxide film constituting the control passivation film 20 may be 1.5 or more (for example, 1.5 to 1.7). At this time, the refractive index of the control passivation film 20 made of the silicon oxide film is the refractive index of the other insulating film (the antireflection film 26, or the front and rear passivation films 24 and 40) made of the silicon oxide film (for example, 1.4 or more) , less than 1.5). However, the present invention is not limited thereto, and the silicon oxide film used as the control passivation film 20 may have various chemical formulas or refractive indices.

In this case, the control passivation layer 20 may have an amorphous structure. More specifically, the control passivation film 20 may be an amorphous film made of only an amorphous structure, or an amorphous film including a partially crystallized portion.

As such, the control passivation layer 20 having an amorphous structure may contribute to forming the diffusion portions 320 and 340 positioned inside the semiconductor substrate 10 . More specifically, when the control passivation layer 20 has an amorphous structure, the first or second conductivity type dopant included in the conductivity type regions 32 and 34 may easily pass through the control passivation layer 20 . Accordingly, the first or second conductivity-type dopant included in the conductivity-type regions 32 and 34 diffuses through the control passivation film 20 to the inside of the semiconductor substrate 10 and diffuses into the semiconductor substrate 10 . The regions 320 and 340 can be easily formed. In addition, the control passivation film 20 includes a first doped portion 202 and/or a second doped portion ( 204) may be included. The first doped portion 202 and the second doped portion 204 may have a doping concentration higher than that of other insulating films (anti-reflection film 26, front and rear passivation films 24 and 40) that do not contain a substantially dopant. can The diffusion regions 320 and 340 and the doped portions 202 and 204 will be described in more detail later.

As described above, the control passivation layer 20 having an amorphous structure may have a thin thickness for carrier movement through the control passivation layer 20 , diffusion control of a dopant, and the like. Accordingly, the thickness of the control passivation film 20 may be smaller than that of other insulating films (the anti-reflection film 26 , the front and rear passivation films 24 and 40 , in particular, other insulating films including oxide films). For example, the thickness of the control passivation layer 20 may be 5 nm or less (more specifically, 2 nm or less, for example, 0.5 nm to 2 nm). If the thickness of the control passivation film 20 exceeds 5 nm, carriers are difficult to move, so the solar cell 100 may not work, and if the thickness of the control passivation film 20 is less than 0.5 nm, the control passivation film of the desired quality ( 20) may be difficult to form. In order to facilitate carrier movement and dopant diffusion, the control passivation layer 20 may have a thickness of 2 nm or less (more specifically, 0.5 nm to 2 nm). In this case, the control passivation layer 20 may have a thickness of 0.5 nm to 1.5 nm to more smoothly move carriers and diffuse dopant. However, the present invention is not limited thereto, and the thickness of the control passivation layer 20 may have various values.

A semiconductor layer 30 including conductive regions 32 and 34 may be positioned on the control passivation layer 20 . In this embodiment, the first and second conductivity-type regions 32 and 34 are formed separately from the semiconductor substrate 10 on the semiconductor substrate 10 (more specifically, on the control passivation film 20), and The semiconductor layer 30 is doped with a first or second conductivity type dopant. For example, the semiconductor layer 30 (or the conductive regions 32 and 34 ) may be formed in contact with the control passivation film 20 to simplify the structure and allow carriers to be easily transferred.

In this embodiment, the first conductivity type region 32 may have a first conductivity type with a first conductivity type dopant, and the second conductivity type region 34 may have a second conductivity type with a second conductivity type dopant. there is. In this case, the first and second conductivity-type regions 32 and 34 and the region having the same conductivity type as the base region 110 (eg, the second conductivity-type region 34 ) have a higher doping than the base region 110 . have concentration. The first conductivity-type region 32 and the second conductivity-type region 34 may be co-located in the semiconductor layer 30 continuously formed on the control passivation film 20 to be positioned on the same plane. In addition, a barrier region 36 may be positioned between the first conductivity-type region 32 and the second conductivity-type region 34 on the same plane as them.

Among the first and second conductivity type regions 32 and 34 , one region having a conductivity type different from that of the base region 110 constitutes at least a portion of the emitter region. The emitter region forms a pn junction (or pn tunnel junction) with the base region 110 to generate carriers by photoelectric conversion. Another one of the first and second conductivity type regions 34 and 34 having the same conductivity type as the base region 110 constitutes at least a part of a back surface field region. The rear electric field region forms a rear electric field that prevents loss of carriers due to recombination on the rear surface of the semiconductor substrate 10 .

When the first or second conductivity-type dopant is p-type, a group 3 element such as boron (B), aluminum (Al), gallium (Ga), or indium (In) may be used. When the first or second conductivity-type dopant is n-type, a group 5 element such as phosphorus (P), arsenic (As), bismuth (Bi), or antimony (Sb) may be used. For example, one of the first and second conductivity-type dopants may be boron (B) and the other may be phosphorus (P).

In addition, a barrier region 36 is positioned between the first conductivity-type region 32 and the second conductivity-type region 34 to space the first conductivity-type region 32 and the second conductivity-type region 34 apart from each other. When the first conductivity-type region 32 and the second conductivity-type region 34 come into contact with each other, a shunt may occur, thereby degrading the performance of the solar cell 100 . Accordingly, in the present embodiment, the barrier region 36 is positioned between the first conductivity-type region 32 and the second conductivity-type region 34 to prevent unnecessary shunts.

An undoped (ie, undoped) insulating material (eg, oxide, nitride) or the like may be used as the barrier region 36 . Alternatively, the barrier region 36 may include an intrinsic semiconductor. In this case, the first conductivity-type region 32 , the second conductivity-type region 34 , and the barrier region 36 are continuously formed while the side surfaces are in contact with each other (eg, a semiconductor including the polycrystalline portion 302 ). layer 30), wherein the barrier region 36 may be an i-type (intrinsic) semiconductor material substantially free of dopant. For example, after an intrinsic semiconductor layer is formed, a first conductivity-type dopant is doped in a portion of the intrinsic semiconductor layer to form a first conductivity-type region 32, and a second conductivity-type dopant is doped in a portion of the other region. When the second conductivity-type region 34 is formed, the first conductivity-type region 32 and the region where the second conductivity-type region 34 is not formed may constitute the barrier region 36 . Accordingly, the manufacturing method of the first conductivity type region 32 , the second conductivity type region 34 , and the barrier region 36 can be simplified.

However, the present invention is not limited thereto. Accordingly, the barrier region 36 may be formed by various methods to have various thicknesses and may have various shapes. The barrier region 36 may be configured as a trench that is an empty space. Various other modifications are possible. In addition, in the drawing, it is exemplified that the barrier region 36 is entirely spaced apart between the first conductivity-type region 32 and the second conductivity-type region 34 . However, the barrier region 36 may be formed to separate only a portion of the boundary between the first conductivity-type region 32 and the second conductivity-type region 34 . Alternatively, since the barrier region 36 is not formed, the boundary between the first conductivity-type region 32 and the second conductivity-type region 34 may contact each other.

In this embodiment, the first and second conductivity-type regions 32 and 34 or the semiconductor layer 30 may have a different crystal structure from that of the semiconductor substrate 10 so that they can be easily formed on the semiconductor substrate 10 . For example, the first and second conductivity-type regions 32 and 34 may be formed of an amorphous semiconductor, a microcrystalline semiconductor, or a polycrystalline semiconductor (eg, amorphous silicon, microcrystalline silicon) that can be easily manufactured by various methods such as deposition. , or polycrystalline silicon) may be formed by doping with a dopant of the first or second conductivity type. In particular, if the first and second conductivity-type regions 32 and 34 have polycrystalline semiconductors, they may have high carrier mobility.

In this case, in the present embodiment, diffusion regions 320 and 340 may be formed in the semiconductor substrate 10 . The diffusion regions 320 and 340 constitute a part of the semiconductor substrate 10 and have the same crystal structure as the base region 110 , and may have a different conductivity type or doping concentration from the base region 110 .

The diffusion regions 320 and 340 may include one of the first diffusion region 320 and the second diffusion region 340 , or may include the first diffusion region 320 and the second diffusion region 340 , respectively. there is. Here, the first diffusion region 320 is partially positioned to correspond to the first conductivity-type region 32 in a plan view and is located in the region of the semiconductor substrate 10 adjacent to the control passivation film 20 in a thickness direction. can be formed. The total doping concentration of the first conductivity type impurities may be lower in the first diffusion region 320 than in the first conductivity type region 32 . In addition, the second diffusion region 340 is partially positioned to correspond to the second conductivity-type region 34 in a plan view and is formed in a region of the semiconductor substrate 10 adjacent to the control passivation film 20 in a thickness direction. can be A total doping concentration of the second conductivity type impurities may be lower in the second diffusion region 340 than in the second conductivity type region 34 . In this case, the doping concentration or the total doping concentration of the second conductivity type impurities may be greater in the second diffusion region 340 than in the base region 110 . In the solar cell 100 having the rear electrode structure as described above, since the first and second conductivity-type regions 32 and 34 are located on the rear surface together, the diffusion regions 320 and 340 are formed entirely on the rear surface of the semiconductor substrate 10 . When formed, the diffusion regions 320 and 340 may rather prevent the necessary carrier movement. For example, when the first diffusion region 320 is formed as a whole, the first diffusion region 320 hinders the flow of carriers from the portion adjacent to the second conductivity-type region 34 to the second conductivity-type region 34 . do. Alternatively, when the second diffusion region 340 is formed as a whole, the second diffusion region 340 prevents the flow of carriers from the portion adjacent to the first conductivity-type region 32 toward the first conductivity-type region 32 . In particular, the diffusion regions 320 and 340 are formed to be spaced apart from each other, and the base region 110 spaced apart from each other may be positioned between the diffusion regions 320 and 340 , thereby reducing the doping region in the semiconductor substrate 10 . A change in characteristics of the semiconductor substrate 10 may be minimized.

In addition, since the first and second diffusion regions 32 and 34 have shapes corresponding to the first and second conductivity-type regions 32 and 34 , the first diffusion region 32 and the second diffusion region 34 are separated from each other. They may be positioned alternately.

In the present embodiment, the diffusion regions 320 and 340 are of the first or second conductivity type at a portion where the first and second conductivity type regions 32 and 34, the control passivation film 20 and the semiconductor substrate 10 are bonded. It serves to transform the energy bands so that the majority carriers in regions 32 and 34 can pass easily. Thereby, the open circuit voltage and the filling density can be improved, and in particular, the filling density can be greatly improved. This will be described in more detail with reference to FIG. 3 .

3A is an energy band diagram of the solar cell 100 according to the present embodiment, and (b) is an energy band diagram of a solar cell that does not include diffusion regions 320 and 340 . 3 illustrates a case in which the base region 110 has an n-type and the first diffusion region 320 and the first conductivity-type region 32 have a p-type, as an example. For reference, the doping concentration of the first diffusion region 320 is smaller than the doping concentration of the first conductivity-type region 32 .

Referring to FIG. 3A , in the first diffusion region 320 , the conduction band and the valence band each gradually increase toward the first conductivity type region 32 , the control passivation layer 20 , and the base region 10 . and transform the energy band to decrease continuously. With such an energy band diagram, an energy band gap ΔEc exists between the base region 10 and the first conductivity-type region 32 for electrons (e-) located in the conduction band, as shown by the solid arrow in the figure. It cannot move to the conductive region 32, and the holes located in the valence conduction band have an energy band gap ΔEv between the base region 10 and the first conductive region 32, as shown by the dotted arrow in the figure. It is easily moved to the first conductivity type region 32 . On the other hand, in the absence of the first diffusion region 320, the conduction band and the valence band are discontinuously located with respect to the control passivation film 20 as shown in FIG. movement in that direction can be prevented. That is, the discontinuous conduction band and valence band in the vicinity of the control passivation film 20 become an energy barrier that prevents the desired carriers from moving to the conductive regions 32 and 34 . As such, in the present embodiment, the diffusion regions 320 and 340 transform an energy band so that desired carriers can easily move to the first and second conductivity-type regions 32 and 34, so that the open-circuit voltage of the solar cell 100 and The filling density can be improved.

Referring back to FIGS. 1 and 2 , the control passivation layer 20 is positioned between the first conductivity type region 32 and the first diffusion region 320 and includes a first doped portion ( 202 ) and/or a second doped portion 204 positioned between the second conductivity type region 34 and the second diffusion region 340 and including a second conductivity type dopant. That is, the control passivation layer 20 may include first and second doped portions 202 and 204 partially formed to correspond to the first and second conductivity-type regions 32 and 34 , respectively. In this embodiment, for example, the control passivation layer 20 corresponds to the barrier region 36 and the first and second doped portions 202 and 204 are spaced apart from each other with the undoped portion 206 interposed therebetween. Thus, they can be positioned alternately with each other. However, the present invention is not limited thereto. In this case, the dopant is partially concentrated in the first and second doped portions 202 and 204 to form the heavily doped portions 202a and 204a having a higher concentration than other portions. The heavily doped portions 202a and 204a may be portions formed by aggregating and remaining dopants in a portion of the control passivation layer 20 . The heavily doped portions 202a and 204a may have various and random shapes and may be irregularly positioned.

Accordingly, the first and second doped portions 202 and 204 of the control passivation film 20 are formed with other undoped insulating films (anti-reflection film 26, front and rear surface passivation films 24 and 40), in particular, oxide films. The doping concentration of the dopant of the first or second conductivity type is higher than that of the other insulating film included.

As described above, in the diffusion regions 320 and 340 , the control passivation film 20 has an amorphous structure, so that the first or second conductivity-type dopant in the conductivity-type regions 32 and 34 easily forms the control passivation film 20 . It can be formed by passing At this time, in the present embodiment, the first conductivity type region 32 , the first doped portion 202 and the first diffusion region 320 related thereto may be formed to have a specific doping profile. In particular, conductivity-type regions 32 and 34 (eg, first conductivity-type region 32 ) having a different conductivity type than that of the base region 110 and functioning as emitter regions, and a doped portion 202 associated therewith, 204) and the doping profile of the diffusion regions 320 and 340 can be controlled. The thicknesses of the diffusion regions 320 and 340 are that the conductivity-type regions 32 and 34 (eg, the second conductivity-type region 34 ) serving as the back field region have the same conductivity type as the base region 10 . , the total doping concentration, etc. may not significantly affect the characteristics of the solar cell 100 . However, the present invention is not limited thereto, and any one of the first and second conductivity-type regions 32 and 34 and the related doped portions 202 and 204 and the diffusion regions 320 and 340 have a doping profile to be described later. can have At this time, in the present specification, the terms "first" and "second" are used only to distinguish each other, and are not limited to these terms.

The doping profile of the first conductivity type region 32 and the first doped portion 202 and the first diffusion region 320 related thereto will be described in detail with reference to FIG. 4 together with FIGS. 1 and 2 . A specific manufacturing method for forming such a doping profile will be described in detail later with reference to FIGS. 5A to 5H and FIGS. 6 to 8 .

FIG. 4 is a graph illustrating doping profiles of the first conductivity type region 32 , the first doped portion 202 , and the first diffusion region 320 in the solar cell shown in FIG. 1 . For reference, the doping profile according to FIG. 4 is shown as measured by secondary ion mass spectrometry (SIMS).

4 , in this embodiment, when viewed in the thickness direction of the solar cell 100 , the first conductivity type region 32 , the control passivation film 20 or the first doped portion 202 , and the first It has a doping profile in which the doping concentration of the dopant of the first conductivity type is continuously decreased toward the diffusion region 320 .

At this time, the control passivation layer 20 or a portion of the first conductivity-type region 32 adjacent thereto has the first doping profile PF1 , and the portion of the first diffusion region 320 adjacent to the control passivation layer 20 is The second doping profile PF2 may be different from the first doping profile PF1 . More specifically, the absolute value of the second concentration gradient of the second doping profile PF2 is smaller than the absolute value of the first concentration gradient of the first profile PF1 . Here, the concentration gradient may be a value obtained by averaging the entire concentration gradient in the profile, or may be a value obtained by calculating the concentration gradient at each point in the profile and averaging them. That is, the doping concentration in the portion of the first diffusion region 320 adjacent to the control passivation film 20 is higher than the degree to which the doping concentration decreases in the control passivation film 20 or in the portion of the first conductivity-type region 32 adjacent thereto. The degree of degradation may be small. For example, a kind of kink or an inflection point may be provided in the second doping profile PF2 . Accordingly, the first diffusion region 320 adjacent to the control passivation layer 20 may be formed to have a thin thickness T2 while having a total doping concentration greater than that of the comparative example or the related art. This is because the manufacturing process is improved when forming the first conductivity type region 32 , the first diffusion region 320 , and the like.

On the other hand, in the comparative example in which the manufacturing process is not improved, it can be seen that the control passivation layer or the portion of the first conductivity type region adjacent thereto and the portion of the first diffusion region adjacent to the control passivation layer have the same or similar doping concentration gradient. . This is because the doping profile of the dopant of the first conductivity type has an approximately linear shape and is diffused such that the control passivation film or a portion of the first conductivity type region adjacent thereto and the portion of the first diffusion region adjacent to the control passivation film are the same or similar. profile, and thus the thickness T2 of the first diffusion region is also relatively large. This will be described in more detail later in the manufacturing method of the solar cell 100 .

In this embodiment, the thickness T2 of the first diffusion region 320 is 100 nm to 300 nm (for example, 200 nm to 300 nm), and the total doping concentration of the first diffusion region 320 is 10 ¹⁷ /cm ³ to 10 ¹⁹ It can be /cm ³ . In addition, the thickness T1 of the first conductivity type region 32 may be 400 nm or less (for example, 100 nm to 400 nm), and the total doping concentration of the first conductivity type region 32 may be 10 ²⁰ /cm ³ or more. . In this case, the thickness T2 of the first diffusion region 320 may be equal to or smaller than the thickness T1 of the first conductivity-type region 32 . In addition, the total doping concentration of the first conductivity-type region 32 may be 10 times or more of the total doping concentration of the first diffusion region 320 . However, the present invention is not limited thereto. The thickness, total doping concentration, etc. of the first diffusion region 320 and the first conductivity-type region 32 may be variously modified. For example, the thickness T2 of the first diffusion region 320 may be greater than the thickness T1 of the first conductivity-type region 32 .

As described above, by reducing the thickness T2 of the first diffusion region 320 compared to the conventional (or comparative example), the open-circuit voltage may be improved. At this time, a relatively low total doping concentration (10 ¹⁹ /cm ³ Since the first diffusion region 320 having the hereinafter) has a low total doping concentration, Auger recombination can be minimized, and a defect site adjacent to the surface of the semiconductor substrate 10 is surrounded ( It acts as a screening) and can rather reduce recombination. Thereby, the open circuit voltage can be further improved. In addition, the first diffusion region 320 has a total doping concentration (10 ¹⁷ /cm ³ ) above a certain level. above), carriers generated by photoelectric conversion in the semiconductor substrate 10 can be easily injected into the first conductivity-type region 32 .

For example, the thickness T2 of the first diffusion region 320 may be based on a distance from the surface of the semiconductor substrate 10 to a portion at which the reference doping concentration Co is determined to be substantially undoped. there is. For example, when the doping concentration is measured by secondary ion mass spectrometry as described above, the reference doping concentration (Co) may be 10 ¹⁷ /cm ³ . This is in consideration of the fact that, according to the secondary ion mass spectrometry method, the doping concentration is indicated by noise or the like even when the dopant is not actually doped. That is, when the doping concentration is less than 10 ¹⁷ /cm ³ , although it is indicated that the doping concentration is present, it is not actually doped, so this part is not considered when determining the thickness of the first diffusion region 320 . However, the present invention is not limited thereto. Therefore, the doping concentration of the first diffusion region 320 may be measured by various methods, and the thickness of the first diffusion region 320 may be measured or determined by various methods in consideration of this. The thickness T1 of the first conductivity type region 32 can be easily found by measuring or determining the thickness of the semiconductor layer 30 . In addition, the total doping concentration may be defined as a value obtained by dividing the total amount of dopants located in the corresponding region by the total volume.

In the first conductivity-type region 32 , a portion spaced apart from the control passivation layer 20 (a portion located on the first electrode 42 side) has a third doping profile different from the first and second doping profiles PF1 and PF2 . (PF3). In this case, absolute values of the first and second concentration gradients of the first and second doping profiles PF1 and PF2 may be greater than absolute values of the third concentration gradient of the third doping profile PF3 . This is because a portion having the same or similar doping concentration exists in a portion spaced apart from the control passivation layer 20 in the first conductivity type region 32 . This means that the portion of the first conductivity type region 32 adjacent to the portion provided with the first conductivity type dopant is relatively uniform and has a first doping profile of a high doping concentration, and the control passivation film 20 and the first diffusion region are relatively uniform. This is because the doping concentration decreases as it passes through (320).

In this embodiment, the second conductivity type region 34 , the second doped portion 204 and the second diffusion region 340 are the first conductivity type region 32 , the first doped portion 202 and the first diffusion region. It may have a doping profile different from that of the region 320 . For example, the doping concentration is uniformly high in the second conductivity-type region 34 and toward the control passivation film 340 and the second diffusion region 340 with a high doping concentration without an approximate linear shape or a large concentration gradient difference. It may have a lowering doping profile. For example, the second conductivity type region 34 , the second doped portion 204 , and the second diffusion region 340 may have doping profiles similar to those of the comparative example of FIG. 4 . This is because the second conductivity type region 34 is doped with a different doping method in a doping process different from that of the first conductivity type region 32 . However, the present invention is not limited thereto.

As another example, the second conductivity type region 34 , the second doped portion 204 , and the second diffusion region 340 include the first conductivity type region 32 , the first doped portion 202 and the first diffusion region ( 320) and may have a doping profile of the same or similar aspect. However, the specific doping concentration or thickness T3 of the second diffusion region 340 may be the same as or different from those of the first conductivity type region 32 , the first doped portion 202 , and the second diffusion region 320 . may be

For example, when viewed in the thickness direction, the absolute value of the doping concentration gradient of the second diffusion region 340 may be smaller than the second doping gradient of the first diffusion region 320 . In addition, the thickness T3 of the second diffusion region 340 having the same second conductivity type as the base region 110 may be greater than the thickness T2 of the first diffusion region 320 having the first conductivity type. This is because the second diffusion region 340 having the same second conductivity type as the base region 110 may be formed to have a relatively large thickness in the base region 110 . In addition, since the first diffusion region 320 must be doped to have a first conductivity type opposite to that of the base region 110 , if it is formed to be relatively thick, passivation characteristics may be deteriorated. For example, in order to simplify the process, according to the thermal diffusion method in which the second conductivity type region 34 and the front electric field region 130 can be formed in the same process, the second conductivity type dopant is infinite, so a relatively thick second diffusion region (340) can be easily formed. In addition, since the first conductivity-type region 32 is formed using a laser for partial doping and the first conductivity-type dopant is finite, a relatively thin first diffusion region 320 can be easily formed. However, the present invention is not limited thereto, and the thickness of the second diffusion region 340 may be smaller than that of the first diffusion region 320 .

Alternatively, the thickness of the second diffusion region 340 may be 800 nm or less (50 nm to 800 nm). Within this thickness range, the effect of the second diffusion region 340 may be sufficiently realized. However, the present invention is not limited thereto.

In the drawings and the above description, it is exemplified that both the first diffusion region 320 and the second diffusion region 340 are provided. Alternatively, only one of the first diffusion region 320 and the second diffusion region 340 may be provided. For example, among the first and second diffusion regions 320 and 340 , the first diffusion corresponding to a conductivity type region (eg, the first conductivity type region 32 ) having a conductivity type opposite to that of the semiconductor substrate 10 . Only the region 320 may be provided, but the second diffusion region 340 corresponding to the conductivity-type region (eg, the second conductivity-type region 34 ) having the same conductivity type as the semiconductor substrate 10 may not be provided. there is. This is a conductive region in which carriers by the conductive dopant included in the semiconductor substrate 10 are used as majority carriers, and carriers are easily controlled through the passivation film 20 by the electric field formed while the carriers of the semiconductor substrate 10 are accumulated. This is because it is difficult for carriers to easily move through the control passivation film 20 to the conductive region using opposite carriers as majority carriers even though they can move. In another embodiment, only the second diffusion region 340 may be provided and the first diffusion region 320 may not be provided.

A rear passivation layer 40 may be formed on the first and second conductivity-type regions 32 and 34 and the barrier region 36 on the rear surface of the semiconductor substrate 10 . For example, the back passivation layer 40 may be formed in contact with the first and second conductivity-type regions 32 and 34 and the barrier region 36 to simplify the structure.

The back passivation layer 40 has contact holes 46 for electrical connection between the conductive regions 32 and 34 and the electrodes 42 and 42 . The contact hole 46 includes a first contact hole 461 for connecting the first conductive region 32 and the first electrode 42 , and the second conductive region 34 and the second electrode 44 . and a second contact hole 462 for connection of The back passivation layer 40 may have an effect of passivating the first and second conductivity-type regions 32 and 34 and/or the barrier region 36 .

In addition, the front passivation film 24 and/or the anti-reflection film 26 may be positioned on the front surface of the semiconductor substrate 10 (more precisely, on the front electric field region 130 formed on the front surface of the semiconductor substrate 10 ). there is. However, the present invention is not limited thereto, and an insulating layer having a different stacked structure may be formed on the front electric field region 130 .

The front passivation layer 24 and the anti-reflection layer 26 may be substantially formed entirely on the entire surface of the semiconductor substrate 10 . In addition, the back passivation layer 40 may be entirely formed on the back surface of the semiconductor layer 30 except for the contact hole 46 .

The front passivation film 24 or the rear passivation film 40 is formed in contact with the semiconductor substrate 10 or the semiconductor layer 30 to prevent defects present in the front surface or the bulk of the semiconductor substrate 10 or the semiconductor layer 30 . immobilize Accordingly, the open circuit voltage of the solar cell 100 may be increased by removing the recombination site of minority carriers. The anti-reflection layer 26 may reduce the reflectance of light incident on the front surface of the semiconductor substrate 10 to increase the amount of light reaching the pn junction. Accordingly, the short-circuit current Isc of the solar cell 100 may be increased.

The front passivation layer 24 , the anti-reflection layer 26 , and the back passivation layer 40 may be formed of various materials. For example, the front passivation film 24, the anti-reflection film 26 or the passivation film 40 is a silicon nitride film, a silicon nitride film containing hydrogen, a silicon oxide film, a silicon oxynitride film, an aluminum oxide film, a silicon carbide film, MgF ₂ , ZnS, Any single layer selected from the group consisting of TiO ₂ and CeO ₂ , or a multilayer structure in which two or more layers are combined may have a structure.

For example, in the present embodiment, the front passivation film 24 and/or the anti-reflection film 26 and the rear passivation film 40 may not include a dopant or the like so as to have excellent insulating properties and passivation properties. However, the present invention is not limited thereto.

The front passivation layer 24 , the antireflection layer 26 , and the back passivation layer 40 may have a thickness greater than that of the control passivation layer 20 . Thereby, an insulating characteristic and a passivation characteristic can be improved. Various other modifications are possible.

The first electrode 42 is formed while filling at least a portion of the first contact hole 461 of the rear passivation film 40 to be electrically connected to the first conductivity-type region 32 (eg, contact is formed), The second electrode 44 is formed while filling at least a portion of the second contact hole 462 of the back passivation layer 40 , and is electrically connected to the second conductivity-type region 34 (eg, a contact is formed).

In the present embodiment, the first conductivity-type region 32 and the second conductivity-type region 34 are formed to be elongated to form a stripe shape, respectively, and are alternately positioned in a direction crossing the longitudinal direction. A barrier region 36 spaced apart from the first conductivity-type region 32 and the second conductivity-type region 34 may be positioned.

In this case, the area of the first conductivity type region 32 may be larger than the area of the second conductivity type region 34 . Accordingly, the emitter region having a large area can effectively collect holes having a relatively slow moving speed, thereby further contributing to the improvement of photoelectric conversion efficiency. However, the present invention is not limited thereto. For example, the areas of the first conductivity-type region 32 and the second conductivity-type region 34 may be adjusted by varying their widths. That is, the width W1 of the first conductivity-type region 32 may be greater than the width W2 of the second conductivity-type region 34 .

In addition, the first electrode 42 may be formed in a stripe shape corresponding to the first conductivity type region 32 , and the second electrode 44 may be formed in a stripe shape corresponding to the second conductivity type region 34 . . The contact hole 46 may be formed to connect only a portion of the first and second electrodes 42 and 44 to the first conductivity-type region 32 and the second conductivity-type region 34 , respectively. For example, the contact hole 46 may include a plurality of contact holes. Alternatively, each of the contact holes 46 may be formed in the entire length of the first and second electrodes 42 and 44 to correspond to the first and second electrodes 42 and 44 . Accordingly, carrier collection efficiency can be improved by maximizing the contact area between the first and second electrodes 42 and 44 and the first conductivity-type region 32 and the second conductivity-type region 34 . Various other modifications are possible.

When light is incident on the solar cell 100 according to the present embodiment, electrons and holes are generated by photoelectric conversion, and the generated holes and electrons pass through the control passivation film 20 to the first conductivity type region 32 , respectively. and the first and second electrodes 42 and 44 after moving to the second conductivity type region 34 . Thereby, electrical energy is generated.

In the solar cell 100 having a rear electrode structure in which electrodes 42 and 44 are formed on the rear surface of the semiconductor substrate 10 and electrodes are not formed on the front surface of the semiconductor substrate 10 as in the present embodiment, the semiconductor substrate 10 ) in front of the shading loss (shading loss) can be minimized. Thereby, the efficiency of the solar cell 100 can be improved. However, the present invention is not limited thereto. A solar cell 100 having a different structure will be described in detail later with reference to FIGS. 9 and 10 .

In addition, since the first and second conductivity-type regions 32 and 34 are formed on the semiconductor substrate 10 with the control passivation film 20 interposed therebetween, they are configured as separate layers different from the semiconductor substrate 10 . Accordingly, loss due to recombination can be minimized compared to the case where the doped region formed by doping the semiconductor substrate 10 with a dopant is used as the conductivity type region. In this case, by improving the open circuit voltage and filling density of the solar cell 100 by the diffusion regions 320 and 340 , the efficiency of the solar cell 100 may be improved.

The above-described doping profiles of the first conductivity-type region 32 , the first doped portion 202 , and the first diffusion region 320 may be implemented by a specific manufacturing method. Hereinafter, a method of manufacturing the solar cell 100 according to an embodiment of the present invention will be described in detail with reference to FIGS. 5A to 5H .

5A to 5H are cross-sectional views illustrating a method of manufacturing the solar cell 100 according to an embodiment of the present invention.

First, as shown in FIG. 5A , a control passivation film 20 is formed on the rear surface of the semiconductor substrate 10 including the base region 110 . The control passivation layer 20 may be entirely formed in contact with the rear surface of the semiconductor substrate 10 .

In this embodiment, as described above, the control passivation layer 20 may have an amorphous structure so that the diffusion regions (reference numerals 320 and 340 in FIG. 5D ) can be easily formed. As such, the control passivation film 20 having an amorphous structure can be easily formed by performing a thermal oxidation process at normal pressure and a process temperature of 600°C to 800°C. More specifically, under normal pressure conditions, the thermal oxidation process is performed by heating from a temperature of 500° C. or less to a process temperature of 600° C. to 800° C., and then cooled to a temperature of 500° C. to 550° C., a control passivation film ( 20) can be formed. In particular, in the present embodiment, after the control passivation film 20 is made by the above-described thermal oxidation process, a separate heat treatment for making the control passivation film 20 dense before forming the semiconductor layer 30 may not be performed. there is. Then, the control passivation layer 20 having an amorphous structure can be formed by a simple process as described above.

In the above-described thermal oxidation process, the gas atmosphere includes oxygen gas (O ₂ ) as a raw material gas, and may further include a halogen gas. The halogen gas may serve to increase the purity and quality of the control passivation layer 20 . As the halogen gas, chlorine gas, which is readily available and has relatively good stability, can be used. As another example, in the thermal oxidation process, the gas atmosphere may include an inert gas or nitrogen gas to form the control passivation layer 20 . As an example, it may include only an inert gas or nitrogen gas. As another example, in the thermal oxidation process, the controlled passivation layer 20 may be formed by decomposing the ozone-containing gas into ultraviolet (UV) light under normal pressure.

Next, as shown in FIGS. 5B to 5F , a first conductivity type region 32 and a second conductivity type region 34 are formed on the control passivation film 20 , and the entire surface of the semiconductor substrate 10 is An electric field region 130 is formed. In addition, an anti-reflection structure (eg, a texturing structure) may be formed on the entire surface of the semiconductor substrate 10 . This will be described in more detail as follows.

As shown in FIG. 5B , the semiconductor layer 30 is formed on the control passivation film 20 . In this case, the semiconductor layer 30 may be an intrinsic semiconductor layer. As described above, the semiconductor layer 30 may be formed of a microcrystalline, amorphous, or polycrystalline semiconductor. The semiconductor layer 30 may be formed by, for example, a deposition method (eg, low-pressure chemical vapor deposition (LPCVD)). Various other methods may be applied.

Although the drawing illustrates that the semiconductor layer 30 is formed only on the rear surface of the semiconductor substrate 10, the present invention is not limited thereto. According to a method of manufacturing the semiconductor layer 30 , the semiconductor layer 30 may be additionally formed on the front surface and/or the side surface of the semiconductor substrate 10 . The semiconductor layer 30 formed on the front surface of the semiconductor substrate 10 in this way may be removed later in a separate step.

Subsequently, as shown in FIGS. 5C to 5E , a first conductivity type region 32 is formed by doping a portion of the semiconductor layer 30 with a first conductivity type dopant, and the entire surface of the semiconductor substrate 10 is textured and reflected. A prevention structure is formed, and as shown in FIG. 5F , the front surface of the semiconductor substrate 10 and the other part of the semiconductor layer 30 are doped with a second conductivity type dopant to form the front electric field region 130 and the second conductivity type region. (34) can be formed. In this case, an undoped region not doped with a dopant may be positioned between the first conductivity-type region 32 and the second conductivity-type region 34 , and this region may constitute the barrier region 36 .

At this time, in this embodiment, the first conductivity type region 32 , the first doped portion 202 , and the first diffusion region 320 are simultaneously formed, and the second conductivity type region 34 and the second doped portion 204 are formed at the same time. ) and the second diffusion region 340 are simultaneously formed.

First, as shown in FIG. 5C , a first dopant layer 322 including a first conductivity type dopant is positioned at a position corresponding to a region where the first conductivity type region 32 is to be formed on the semiconductor layer 30 having intrinsic properties. ) to form The first dopant layer 322 may be made of various materials including the first conductivity type dopant, for example, may be an insulating layer or a semiconductor layer including the first conductivity type dopant. The first dopant layer 322 may include a single or a plurality of silicon nitride films, silicon oxide films, or amorphous silicon films containing the first conductivity type dopant. In addition, the first dopant layer 322 may be formed by, for example, a thermal growth method, a deposition method, or the like. Various other methods may be applied.

Next, as shown in FIG. 5D , the first conductivity type region 32 is formed by diffusing the first conductivity type dopant included in the first dopant layer 322 into the semiconductor layer 30 using a laser 324 . to form In this case, the first conductivity-type dopant is also diffused into the control passivation layer 20 and a part of the semiconductor substrate 10 to form the first doped portion 202 and the first diffusion region 320 together.

In this case, the laser 324 may be irradiated in a defocused state. Whether the laser 324 is in a defocused state or a focused state can be easily distinguished by the shape of the laser beam. This will be described in detail with reference to FIG. 6 .

FIG. 6 schematically shows the shape of a laser beam formed on the first dopant layer 322 by the doping process included in the method of manufacturing the solar cell 100 shown in FIG. 5D , (a) is a focused laser The shape of the laser beam when using , (b) shows the shape of the laser beam when the defocused laser is used.

As shown in FIG. 6A , according to the focused laser 324 (eg, the laser 324 focused on the first dopant layer 322 ), the first dopant layer 322 is formed. The boundary line of the laser beam is clear, clear, and thin. On the other hand, as shown in FIG. 6B, according to the defocused laser 324 (eg, the defocused laser 324 on the first dopant layer 322), the first dopant layer ( 322), the boundary line of the laser beam formed is blurred or has a spread shape. Whether the laser is focused or defocused can be determined by the shape of the laser beam. However, the present invention is not limited thereto, and it is possible to determine whether the focus is focused or defocused by various methods.

When the defocused laser 324 is used in the doping process as described above, the first conductivity-type dopant included in the first dopant layer 322 can be accumulated in a portion adjacent thereto after passing through the control passivation layer 20 . there is. Accordingly, the thickness T2 of the first diffusion region 320 may be minimized while increasing the total doping concentration of the first diffusion region 320 . That is, the doping profile of the first conductivity-type region 32 , the first doped portion 202 , and the first diffusion region 320 may be controlled by the laser defocused on the first dopant layer 322 . Accordingly, as in the embodiment of FIG. 4 , the first to third doping profiles PF1 , PF2 , and PF3 may be provided, and the thickness T2 of the first diffusion region 320 may be 100 nm to 300 nm.

On the other hand, when the laser is used in a focused state, unlike the present embodiment, the dopant of the first conductivity type included in the first dopant layer is deeply diffused to the inside of the semiconductor substrate with a similar concentration gradient. Accordingly, as in the comparative example of FIG. 4 , the doping profile in the first doped portion and the first diffusion region has an approximately linear shape and has the same or similar concentration gradient, and thus the total doping concentration of the first diffusion region is relatively small and the thickness is relatively large.

As described above, in the present embodiment, in the doping process using the first dopant layer 322 and the laser 324 , the laser 324 is irradiated to the first dopant layer 322 in a defocused state to form the first conductivity type dopant. The doping profile may be controlled and the thickness T2 of the first diffusion region 320 may be minimized. Accordingly, while maximizing the effect of the first diffusion region 320 , it is possible to minimize or prevent a recombination problem that may occur when the first diffusion region 320 is formed.

As a method of defocusing the laser 324 in the first dopant layer 322 as described above, various methods may be applied. A detailed method of defocusing the laser 324 in the doping process according to the present embodiment will be described with reference to FIGS. 7 and 8 together. 7 is a schematic diagram illustrating an example of a doping process included in the method of manufacturing the solar cell 100 illustrated in FIG. 5D , and FIG. 8 is a doping included in the method of manufacturing the solar cell 100 illustrated in FIG. 5D . It is a schematic diagram showing another example of the process. 7 and 8, only the first dopant layer 322 and the semiconductor layer 30 are shown in the solar cell 100 for clear and simple illustration, and the lenses 324a, 324b, and 324c are shown in arbitrary shapes. However, the present invention is not limited to the shape of the lenses 324a, 324b, and 324c.

For example, as shown in FIG. 7 , the laser 324 is focused on the first dopant layer 322 (that is, the boundary line of the laser beam is clear as shown in FIG. 6A ). After positioning), the position of the laser 324 may be changed, and in particular, the distance between the first dopant layer 324 and the laser 322 may be decreased or increased so as to be defocused. In this case, a change in the distance between the first dopant layer 322 and the laser 324 for defocusing may be within 30 mm. That is, the distance between the laser 324 and the first dopant layer 322 may be increased or decreased within 30 mm in the focused state. If the distance change exceeds 30 mm, it is difficult for energy by the laser 324 to be sufficiently transmitted to the first dopant layer 322 , so that the doping process may not be smoothly performed. In this case, a change in the distance between the first dopant layer 322 and the laser 324 for defocusing may be greater than the thickness of the first dopant layer 324 . For example, the change in the distance between the first dopant layer 322 and the laser 324 for defocusing may be 0.5 mm or more (eg, 0.5 mm to 2 mm). This is to sufficiently realize the effect of the defocus. However, the present invention is not limited thereto. 7 illustrates that the lens 324a is used, but the present invention is not limited thereto.

As another example, as shown in FIG. 8 , the laser 324 is focused on the first dopant layer 322 using the first lens 324b having a first magnification (that is, in FIG. 6(a) ), after positioning so that the boundary line of the laser beam becomes clear), by changing the first lens 324b to a second lens 324c having a second magnification different from the first magnification, the laser 324 ) may be defocused on the first dopant layer 322 . The second magnification of the second lens 324c may be greater or smaller than the first magnification of the first lens 324b. As shown in FIG. 8 , the laser 324 can be easily changed to a defocused state by replacing the lenses 324b and 324c. The laser beam by the defocused laser 324 may be larger or smaller than the laser beam by the focused laser 324 . The first or second magnifications of the first and second lenses 324b and 324c may be X1 to X10, but the present invention is not limited thereto.

Referring back to FIG. 5D , various lasers for a doping process may be used as the laser 324 in this embodiment. For example, the laser 324 may have a wavelength of 1064 nm or less. However, the present invention is not limited thereto.

For example, the laser 324 may be a pulsed wave laser that has an output for a predetermined time in a pulse waveform and no output for a predetermined time. According to this, sufficient energy is provided to the first dopant layer 322 in a short time so that the first conductivity-type dopant can be stably diffused. For example, the pulse width of the laser 324 may be in the range of femtoseconds (psec) to nanoseconds (nsec). In such a pulse width of the laser 324 , energy required for removal in the doping process may be sufficiently provided. If the pulse width of the laser 324 is less than the femtosecond level, the process time may be long. can be On the other hand, unlike the present embodiment, a continuous wave laser having a constant and continuous output may not provide sufficient energy to the first dopant layer 322 . However, the present invention is not limited thereto. Therefore, the laser 324 may have a different pulse width, or a continuous oscillation laser may be used.

The size of the laser beam of the laser 324 may be 10 μm to 2 mm. The size of the laser beam of the laser 324 is limited to a size suitable for application to the doping process. In this case, if the size of the laser beam is less than 10 μm, the processing time may be long, and if the size of the laser beam exceeds 2 mm, it is difficult for the first conductivity-type region 32 to have a desired doping concentration, and properties may be deteriorated. However, the present invention is not limited to the size of the laser beam, the laser beam irradiation method, and the like.

Subsequently, as shown in FIG. 5E , the first dopant layer 322 may be removed. The first dopant layer 322 may be removed by various methods. For example, the first dopant layer 322 may be removed by a wet process using a material (eg, a solution) capable of removing the first dopant layer 322 .

In this case, an anti-reflection structure may be formed together on the entire surface of the semiconductor substrate 10 . The anti-reflection structure may be formed by texturing, and wet or dry texturing may be used. Wet texturing may be performed by immersing the semiconductor substrate 10 in a texturing solution, and has the advantage of a short process time. According to the wet texturing, the removal and texturing of the first dopant layer 322 can be simultaneously performed, thereby simplifying the process. In dry texturing, the surface of the semiconductor substrate 10 is cut using a diamond grill or a laser, and the unevenness may be uniformly formed, but the processing time is long and damage to the semiconductor substrate 10 may occur. In addition, the semiconductor substrate 10 may be textured by reactive ion etching (RIE) or the like. As described above, in the present invention, the semiconductor substrate 10 may be textured by various methods.

Subsequently, as shown in FIG. 5F , a second conductivity type region 34 , a second diffusion region 340 , and a front electric field region 130 may be formed.

For example, a second dopant layer (not shown) containing a second conductivity type dopant is formed on the semiconductor layer 30 at a position corresponding to the region where the second conductivity type region 34 is to be formed, and then heat treatment ( For example, laser irradiation) may be performed to form the second conductivity type region 34 and the second diffusion region 340 . Then, when the second conductivity type region 34 is formed, the second conductivity type dopant passes through the second conductivity type region 34 (or the semiconductor layer 30 ) and the control passivation film 20 to the semiconductor substrate 10 . to form a second doped portion 204 and a second diffusion region 340 . For example, the second conductivity type region 34 , the second doped portion 204 , the second diffusion region 340 , and the front electric field region 130 are formed by thermal diffusion using a gas containing the second conductivity type dopant. can be formed at the same time. As described above, the doping process for forming the second conductivity-type region 34 may be different from the doping process for forming the first conductivity-type region 32 to simplify the process. However, the present invention is not limited thereto. The second conductivity type region 34 , the front electric field region 130 , etc. are formed by various methods such as an ion implantation method, a method of heat treatment or laser irradiation after forming a second dopant layer containing the second conductivity type dopant. can be

In this embodiment, after forming the first conductivity-type region 32 and the first diffusion region 320 , the second conductivity-type region 34 and the second diffusion region 340 are exemplified. However, the present invention is not limited thereto. As another example, after forming the first dopant layer 322 including the first conductivity type dopant and the second dopant layer (not shown) including the second conductivity type dopant, doping using the laser 324 described above The processes may be performed simultaneously. According to this, the second conductivity type region 34, the second doped portion 204, and the second diffusion region 340, although there is a difference in thickness, doping concentration, concentration gradient, etc., as shown in FIG. It may have a doping profile including the first to third doping profiles PF1 , PF2 , and PF3 . In addition, although the first and second diffusion regions 320 and 340 have been illustrated in this embodiment, the second diffusion region 340 may not be provided. In addition, although it has been exemplified that the front electric field region 130 is formed by the same doping process as the second conductivity type region 34 and/or the second diffusion region 340 , the front electric field region 130 is formed in a different process. it might be That is, the formation order of the first conductivity type region 32 , the second conductivity type region 34 , the front electric field region 130 , the first and second diffusion regions 320 and 340 , and the texturing structure may be variously modified. It is possible.

Next, as shown in FIG. 5G , another insulating film is formed on the front and rear surfaces of the semiconductor substrate 10 . That is, the front passivation film 24 and the anti-reflection film 26 are formed on the front surface of the semiconductor substrate 10 , and the rear passivation film 40 is formed on the rear surface of the semiconductor substrate 10 .

More specifically, the front passivation film 24 and the anti-reflection film 26 are formed entirely on the front surface of the semiconductor substrate 10 , and the rear passivation film 40 is formed entirely on the rear surface of the semiconductor substrate 10 . The front passivation film 24 , the anti-reflection film 26 , or the rear passivation film 40 may be formed by various methods such as vacuum deposition, chemical vapor deposition, spin coating, screen printing, or spray coating. The formation order of the front passivation film 24, the antireflection film 26, and the rear passivation film 40 is not limited.

Next, as shown in FIG. 5H , first and second electrodes 42 and 44 respectively connected to the first and second conductivity-type regions 32 and 34 are formed.

For example, a contact hole 46 is formed in the back passivation layer 40 by a patterning process, and thereafter, the first and second electrodes 42 and 44 are formed while filling the contact hole 46 . In this case, the contact hole 46 may be formed by laser ablation using a laser or various methods using an etching solution or an etching paste. In addition, the first and second electrodes 42 and 44 may be formed by various methods such as sputtering, plating, and vapor deposition. In particular, in this embodiment, the first and second electrodes 42 and 44 may be formed by a sputtering method.

However, the present invention is not limited thereto. As another example, the first and second electrode forming pastes are respectively coated on the back passivation film 40 by screen printing, etc., and then fire through or laser firing contact is performed to form the above-described shape. It is also possible to form the first and second electrodes 42 and 44 of In this case, since the contact hole 46 is formed when the first and second electrodes 42 and 44 are formed, a separate process of forming the contact hole 46 does not need to be added.

According to the present embodiment, the diffusion regions 320 and 340 having a desired doping profile and thickness can be formed by a simple process. Accordingly, the manufacturing method of the solar cell 100 having excellent efficiency can be simplified, and productivity can be improved.

In the above-described embodiment, the structure in which the first and second conductivity-type regions 32 and 34 and the first and second electrodes 42 and 44 are both located on the rear surface of the semiconductor substrate 10 has been described as an example. However, the present invention is not limited thereto, and the above-described control passivation film 20 , the first and second conductivity-type regions 32 and 34 , and the diffusion regions 320 and 340 in the solar cell 100 having a different structure. This can be applied.

Hereinafter, a solar cell and a method for manufacturing the same according to another embodiment of the present invention will be described in detail. A detailed description of the same or extremely similar parts to the above description will be omitted and only different parts will be described in detail. In addition, combinations of the above-described embodiment or a modified example thereof and the following embodiment or a modified example thereof are also within the scope of the present invention.

9 is a cross-sectional view illustrating a solar cell according to another embodiment of the present invention, and FIG. 10 is a plan view of the solar cell shown in FIG. 9 .

9 and 10 , in the present embodiment, the first conductivity type region 32 is located on the first control passivation film 20a on one surface of the semiconductor substrate 10 , and the second conductivity type region 34 is It is positioned on the second control passivation film 20b positioned on the other surface of the semiconductor substrate 10 . At this time, the first control passivation film 20a and the first conductivity type region 32 are entirely formed on one surface of the semiconductor substrate 10 , and the second control passivation film 20b is formed with the second conductivity type region 34 . It may be formed entirely on the other surface of the semiconductor substrate 10 . And unlike the embodiment with reference to FIGS. 1 to 5 , the front electric field region 130 is not provided in this embodiment.

For example, the first control passivation layer 20a may be in contact with the semiconductor substrate 10 , and the first conductivity-type region 32 may be positioned in contact with the first control passivation layer 20a. For example, the second control passivation layer 20b may be in contact with the semiconductor substrate 10 , and the second conductivity type region 34 may be disposed in contact with the second control passivation layer 20b.

In this case, the first and second passivation films 20a and 20b may be the same as or very similar to the control passivation film 20 of the above-described embodiment. In addition, the first and second control passivation layers 20a and 20b may be formed by the same method as the control passivation layer 20 of the above-described embodiment. For example, in the process of forming the control passivation film 20 , the first control passivation film 20a formed on the front surface of the semiconductor substrate 10 and the second control passivation film 20b formed on the rear surface of the semiconductor substrate 10 . ) can be simultaneously formed by the same process. In this case, the first passivation film 20a may be composed of a first doped portion (reference numeral 202 in FIG. 1 ) including a first conductivity-type dopant, and the second passivation film 20b entirely contains a second conductivity-type dopant. It may be composed of the included second doped portion (reference numeral 204 in FIG. 1 ). Although not shown in the drawings, the first and second passivation layers 20a and 20b may include heavily doped portions (reference numerals 202a and 204a in FIG. 1 ).

And the first and second conductivity type regions 32, 34 may be the same or extremely similar to the first or second conductivity type regions 32, 34 of the above-described embodiments, except for shape and/or location. Accordingly, the first and second semiconductor layers 30a and 30b constituting the first and second conductivity-type regions 32 and 34 are the semiconductor layers (reference numeral 30 in FIG. 1 , the same hereinafter) in the above-described embodiment. ) may be applied. As an example, in the process of forming the semiconductor layer 30 , the first semiconductor layer 30a positioned on the first control passivation film 20a on the front surface of the semiconductor substrate 10 and The second semiconductor layer 30b positioned on the second control passivation film 20b on the rear surface of the semiconductor substrate 10 may be simultaneously formed by the same process.

In addition, in the present embodiment, the first diffusion region 320 is formed as a whole in the portion of the semiconductor substrate 10 adjacent to the first control passivation film 20a under the first conductivity type region 32 , and the second conductivity type region 32 is formed. A second diffusion region 340 may be formed entirely in a portion of the semiconductor substrate 10 adjacent to the second control passivation layer 20b under the region 34 . In addition, the first passivation film 20a may be entirely composed of the first doped portion 202 , and the second passivation film 20b may be composed entirely of the second doped portion 204 . The first and second diffusion regions 320 and 340, and the first and second doped portions 202 and 204 are described in the above embodiments except for planar shapes (in particular, descriptions of doping profiles, etc.) This can be applied as it is.

However, the present invention is not limited thereto, and the second control passivation layer 20b, the second doped portion 204 and the second diffusion region 340 may not be provided. The front surface passivation film 24 and the antireflection film 26 are substantially on the first conductivity-type region 32 except for the first contact hole 461 corresponding to the first electrode 42 , on the front surface of the semiconductor substrate 10 . may be formed throughout. For example, the front passivation layer 24 may contact the first conductivity type region 32 , and the anti-reflection layer 26 may contact the front passivation layer 24 . A rear passivation layer 40 may be formed on substantially the entire rear surface of the semiconductor substrate 10 on the second conductivity-type region 34 except for the second contact hole 462 corresponding to the second electrode 44 . . For example, the back passivation layer 40 may be formed in contact with the second conductivity type region 34 .

The first electrode 42 is formed through the first contact hole 461 formed in the front passivation film 24 and the anti-reflection film 26 (that is, through the front passivation film 24 and the anti-reflection film 26). It may be electrically connected (eg, contacted) to the first conductivity type region 32 . The second electrode 44 is electrically connected to the second conductivity type region 34 through the second contact hole 462 formed in the rear passivation film 40 (that is, through the rear passivation film 40) ( For example, contact) may be used.

Although the drawings illustrate that the anti-reflection structure is formed on the front and rear surfaces of the semiconductor substrate 10, respectively, the anti-reflection structure may be formed on only one of the front and rear surfaces, or the anti-reflection structure may not be formed on the front and rear surfaces of the semiconductor substrate 10 .

The planar shape of the first and second electrodes 42 and 44 will be described in detail with reference to FIG. 10 .

Referring to FIG. 10 , the first and second electrodes 42 and 44 may include a plurality of finger electrodes 42a and 44a spaced apart from each other while having a constant pitch. Although the figure illustrates that the finger electrodes 42a and 44a are parallel to each other and parallel to the edge of the semiconductor substrate 10, the present invention is not limited thereto. In addition, the first and second electrodes 42 and 44 may include bus bar electrodes 42b and 44b that are formed in a direction crossing the finger electrodes 42a and 44a and connect the finger electrodes 42a and 44a. there is. One such bus bar electrodes 42b and 44b may be provided, or as shown in FIG. 10 , a plurality of bus bar electrodes 42b and 44b may be provided while having a pitch greater than that of the finger electrodes 42a and 44a. In this case, the width of the bus bar electrodes 42b and 44b may be greater than the width of the finger electrodes 42a and 44a, but the present invention is not limited thereto. Accordingly, the widths of the bus bar electrodes 42b and 44b may be equal to or smaller than the widths of the finger electrodes 42a and 44a.

In the drawings, it is exemplified that the first electrode 42 and the second electrode 44 have the same planar shape. However, the present invention is not limited thereto, and the width and pitch of the finger electrode 42a and the bus bar electrode 42b of the first electrode 42 are determined by the finger electrode 44a and the bus bar electrode of the second electrode 44 . The width and pitch of (44b) may have different values. In addition, it is possible that the first electrode 42 and the second electrode 44 have different planar shapes, and various other modifications are possible.

As described above, in the present embodiment, the first and second electrodes 42 and 44 of the solar cell 100 have a constant pattern, so that the solar cell 100 can allow light to be incident on the front and rear surfaces of the semiconductor substrate 10 . It has a bi-facial structure. Accordingly, the amount of light used in the solar cell 100 may be increased, thereby contributing to the improvement of the efficiency of the solar cell 100 . However, the present invention is not limited thereto, and it is also possible to have a structure in which the second electrode 44 is formed entirely on the back side of the semiconductor substrate 10 . Various other modifications are possible.

The features, structures, effects, etc. as described above are included in at least one embodiment of the present invention, and are not necessarily limited to one embodiment. Furthermore, features, structures, effects, etc. illustrated in each embodiment can be combined or modified for other embodiments by those of ordinary skill in the art to which the embodiments belong. Accordingly, the contents related to such combinations and modifications should be interpreted as being included in the scope of the present invention.

100: solar cell
10: semiconductor substrate
20: control passivation film
202: first doped portion
204: second doped portion
32: first conductivity type region
34: second conductivity type region
36: barrier area
320: first diffusion region
340: second diffusion region
42: first electrode
44: second electrode

Claims (16)

semiconductor substrate;
a control passivation film formed on one surface of the semiconductor substrate;
a first conductivity type region formed on the control passivation layer and including a first conductivity type dopant;
a first electrode connected to the first conductivity type region;
a second conductivity type region comprising a second conductivity type dopant having a second conductivity type opposite to the first conductivity type; and
a second electrode connected to the second conductivity type region
including,
a first diffusion region having the first conductivity type dopant is formed in a portion of the semiconductor substrate corresponding to the first conductivity type region;
the control passivation layer includes a first doped portion positioned between the first conductivity type region and the first diffusion region and comprising the first conductivity type dopant;
The doping concentration of the dopant of the first conductivity type is continuously decreased toward the first conductivity type region, the control passivation layer, and the first diffusion region, so that the first diffusion region has a lower doping than the first conductivity type region. Have a doping profile having a concentration,
The control passivation layer or a portion of the first conductivity type region adjacent thereto has a first doping profile, and a portion of the first diffusion region adjacent to the control passivation layer has a second doping profile different from the first doping profile ,
an absolute value of the second concentration gradient of the second doping profile is smaller than an absolute value of the first concentration gradient of the first doping profile;
a second diffusion region having the second conductivity type dopant is formed in a portion of the semiconductor substrate corresponding to the second conductivity type region;
the control passivation layer includes a second doped portion positioned between the second conductivity type region and the second diffusion region and comprising the second conductivity type dopant;
Doedoe having a doping profile in which the doping concentration of the second conductivity type dopant is continuously decreased toward the second conductivity type region, the control passivation layer, and the second diffusion region, the first conductivity type region and the control passivation region a film, and a doping profile different from that of the first diffusion region,
The solar cell wherein the absolute value of the concentration gradient of the second diffusion region is smaller than the absolute value of the second concentration gradient. According to claim 1,
A solar cell wherein the thickness of the first diffusion region is 100 nm to 300 nm. 3. The method of claim 2,
A solar cell wherein the thickness of the first diffusion region is 200 nm to 300 nm. According to claim 1,
A solar cell having a total doping concentration of 10 ¹⁷ /cm ³ to 10 ¹⁹ /cm ³ in the first diffusion region. According to claim 1,
A solar cell having a total doping concentration of 10 ²⁰ /cm ³ or more in the first conductivity-type region. According to claim 1,
A solar cell in which a thickness of the first diffusion region is less than or equal to a thickness of the first conductivity-type region. According to claim 1,
a portion of the first conductivity-type region spaced apart from the control passivation layer has a third doping profile different from the first and second doping profiles;
and wherein absolute values of the first concentration gradient and the second concentration gradient are greater than absolute values of a third concentration gradient of the third doping profile. According to claim 1,
The solar cell in which the first conductivity type region has a conductivity type opposite to that of the base region of the semiconductor substrate. forming a control passivation film on one surface of a semiconductor substrate;
forming a first conductivity type region including a first conductivity type dopant and a second conductivity type region including a second conductivity type dopant on the control passivation layer; and
forming a first electrode connected to the first conductivity-type region and a second electrode connected to the second conductivity-type region
including,
The step of forming the first conductivity type region,
forming an intrinsic semiconductor layer;
forming a first dopant layer including the first conductivity type dopant on the intrinsic semiconductor layer; and
A doping process in which the first conductivity-type dopant included in the first dopant layer is diffused into the intrinsic semiconductor layer to dope the intrinsic semiconductor layer using a defocused laser
including,
The second conductivity type region is formed by a doping process different from that of the first conductivity type region,
In the doping process, a first diffusion region is formed in a portion of the semiconductor substrate corresponding to the first conductivity-type region, and a first diffusion region is formed in the control passivation layer between the first conductivity-type region and the first diffusion region. 1 a doped portion is formed,
The control passivation layer or a portion of the first conductivity type region adjacent thereto has a first doping profile, and a portion of the first diffusion region adjacent to the control passivation layer has a second doping profile different from the first doping profile ,
The method of manufacturing a solar cell, wherein the absolute value of the second concentration gradient of the second doping profile is smaller than the absolute value of the first concentration gradient of the first doping profile. 10. The method of claim 9,
In the doping process, after focusing the laser, the laser is defocused by changing the distance between the first dopant layer and the laser or by changing the lens arrangement of the laser.
A method of manufacturing a solar cell. delete delete 10. The method of claim 9,
A method of manufacturing a solar cell wherein the thickness of the first diffusion region is 100 nm to 300 nm. 11. The method of claim 10,
In the doping process, after focusing the laser, the laser is defocused by changing the distance between the first dopant layer and the laser,
A method of manufacturing a solar cell in which a change in a distance between the first dopant layer and the laser is within 30 mm. 10. The method of claim 9,
The method of manufacturing a solar cell wherein the second conductivity type region is formed by a doping process using a thermal diffusion method. 10. The method of claim 9,
The method of manufacturing a solar cell, wherein the control passivation layer includes an amorphous structure and is made of a dielectric material.

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