KR101143776B1 - Back contact solar cell and fabrication method thereof - Google Patents

Abstract

The present invention is a back-electrode solar cell forming both the emitter and the base on the back of the silicon wafer, the method using the laser chemical process (LCP) to apply a dopant while melting the back of the silicon wafer, the emitter and the base Forming a back side of the silicon wafer; Forming a SiO ₂ oxide film on a back surface of the silicon wafer; Forming a contact hole in the SiO ₂ oxide film in the region where the emitter and the base are formed; Forming a metal electrode in each contact hole; relates to a back electrode solar cell comprising a; and a method of manufacturing the same.
According to the present invention, it is possible to significantly reduce the manufacturing cost and manufacturing time by reducing the manufacturing process of the back-electrode solar cell, and also to prevent the occurrence of butting between the emitter and the base by the SiO ₂ barrier, HAZ is not formed by blocking unnecessary heat transfer to the emitter or the base during the formation of the contact hole.

Description

BACK CONTACT SOLAR CELL AND FABRICATION METHOD THEREOF

The present invention relates to a back electrode solar cell, and more particularly, to form an emitter and a base using a laser chemical process (LCP) on a rear surface of a semiconductor substrate, and to form an electrode on each of the emitter and the base. A battery and a method of manufacturing the same.

A solar cell is a device that converts light energy into electrical energy by using a photovoltaic effect. The solar cell is classified into a silicon solar cell, a thin film solar cell, a dye-sensitized solar cell, and an organic polymer solar cell. . These solar cells are used independently as main power sources such as electronic clocks, radios, unmanned light towers, satellites, rockets, etc., and are also used as auxiliary power sources in connection with commercial AC power systems. Increasingly, interest in solar cells is increasing.

In the conventional general solar cell, an electrode is formed on the front and the rear, respectively, and there is a problem in that absorption of sunlight is reduced due to the electrode formed on the front. Therefore, in order to improve the efficiency of solar cells, the general trend is to narrow the area of the electrode formed on the front surface to have a fine pattern as much as possible. However, even in this case, the solar cell may not absorb sunlight as much as the electrode area formed on the front surface, and there is also a problem in that resistance is unnecessarily increased due to the fine electrode.

Therefore, in order to fundamentally eliminate the reduction of absorption by the electrode at the front of the solar cell, a solar cell having a back electrode structure in which all the electrodes are installed at the rear has been developed.

In the solar cell of the back electrode structure, all the electrodes on the front side are installed on the back side to reduce the shadowing loss caused by the electrode, thereby obtaining high short circuit current and low series resistance value. Has This makes it possible to manufacture high efficiency solar cells. In addition, the module using the back-junction solar cell is easy to manufacture because it is possible to connect the electrode on the plane, and has the advantage of improving the efficiency of the module and lowering the manufacturing cost by increasing the packing density of the solar cell.

Such a back electrode solar cell has a base and an n-type (or p-type) charge that collects a p-type (or n-type) charge on a back surface opposite to the front surface where light is incident on a p-type (or n-type) silicon substrate. It shows a structure in which all of the emitters collected are formed.

Such a back electrode solar cell is expected to improve efficiency by improving the absorption rate of the solar light, but the manufacturing process was complicated and costly disadvantages, and thus the situation is difficult to commercialize the back electrode solar cell.

Therefore, a back electrode solar cell has been proposed that can simplify the process and reduce the manufacturing cost. An example thereof is disclosed in US Patent No. US 07339110 (a solar cell and its manufacturing method, hereinafter referred to as a prior patent).

The solar cell manufacturing process according to the prior patent consists of about 30 processes. Particularly, about 20% of the high temperature process, that is, the n + layer, the p + layer, and the oxide film forming process, are performed at a temperature of about 900 ° C. or higher.

Here, the process of forming the base and the emitter on the back of the p-type silicon wafer of the manufacturing process of the prior patent will be described.

First, a p + layer is formed on one side (i.e., the opposite side to which sunlight is incident) of the p-type silicon wafer where the saw damage etching process is completed (step 1), and a thermal oxide film is formed thereon (step 2). .

Then, an etch resist is printed on a portion of the thermal oxide film, that is, a portion except for the portion where the n + layer is to be formed in a subsequent process (step 3).

Thereafter, the thermal oxide film formed on the portion where the etch resist is not printed is etched (step 4), the etch resist is removed (step 5), and the surface of the silicon wafer is etched to a predetermined depth (step 6). In this case, the etching depth may be larger than the junction depth of the p + layer. In the above patent, it is illustrated as 3㎛.

When the etching process is completed, the back surface of the silicon wafer is cleaned with a cleaning liquid (step 7).

Then, an n + layer is formed on the surface of the etched silicon wafer using a liquid dopant source such as' POCl 3 (phosphorus oxychloride), a doping element of the p-type silicon wafer, as a raw material (step 8). Of course, when the n-type silicon wafer and p + layer to form a liquid dopant source such as 'BBr3' is used.

As such, in the prior patent, a process of jointly forming a base for collecting charges of the same conductivity type as the silicon wafer and an emitter for collecting charges of another conductivity type on the back surface of the silicon wafer is performed in eight steps. have.

In addition, the process of doping the p-type and n-type impurities in the prior patent and the process of forming a thermal oxide film is carried out in a high temperature diffusion furnace, it is carried out at a high temperature of about 900 ℃. In other words, two diffusion processes and one thermal oxide film formation step were necessary at high temperatures.

In general, if the process temperature can be lowered while maintaining the efficiency in the solar cell process, this can help to reduce costs and simplify the process.

However, as described above, when the base and the emitter are formed on the back surface of the silicon wafer, the process is performed at a high temperature of 900 ° C. or higher, and the situation is not lowered to a process temperature below that. In addition, since the process is performed at a high temperature of more than 900 ℃ it was difficult to reduce the current number of processes.

As a result, the prior patent has a substantial problem that it is difficult to sufficiently reduce the manufacturing cost of the solar cell because not only the amount of energy input but also the process time is long when manufacturing the back electrode solar cell.

On the other hand, due to the characteristics of the back electrode solar cell in which both the emitter and the base are formed on the back side of the wafer, there is a concern that the butting phenomenon between the emitter and the base may occur. That is, since the recombination of holes and electrons rapidly increases in the overlapping region of the emitter and the base, the efficiency of the back electrode solar cell is greatly reduced as the overlapping region is larger or larger. Therefore, an intrinsic semiconductor buffer region is generally provided between the emitter and the base, which is not technically easy due to the need for very fine control.

In addition, in order to form electrodes for the emitter and the base, a SiO ₂ oxide film is formed on the back surface of the silicon wafer and then irradiated with laser to form contact holes. At this time, in the process of melting the SiO ₂ oxide film through such laser irradiation, high temperature heat may directly or indirectly affect the emitter and the base or the surface of the silicon wafer by the melting point difference between the silicon wafer and the SiO ₂ oxide film. do.

That is, in the case of single crystal silicon, the melting point is 1414 ° C, but in the case of SiO ₂ oxide film, the melting point is melted at a high temperature of 1710 ° C or higher. Therefore, in order to form a contact hole there is this melt the heat SiO ₂ oxide film over 1710 ℃ through the laser irradiation, SiO ₂ oxide film is both the moment of melt reaches the surface of the wafer, the high heat causes not, directly or indirectly, to the wafer It will have a good effect. For example, high-temperature heat forms a heat-affected zone (HAZ) around the surface of a silicon wafer on which emitters or bases are formed, which can degrade solar cell performance.

SUMMARY OF THE INVENTION The present invention has been made to solve various problems in the prior art as described above, and its main object is to significantly reduce the manufacturing cost and manufacturing time by reducing the manufacturing process of the back electrode solar cell.

It is another object of the present invention to prevent the occurrence of butting between the emitter and the base.

In another aspect, the present invention is to block the unnecessary heat transfer to the emitter or the base in the process of forming a contact hole so that the HAZ is not formed.

A method for manufacturing a back electrode solar cell according to the present invention as a means for solving the above problems, in the back electrode solar cell to form both the emitter and the base on the back of the silicon wafer, using a laser chemical process (LCP) Forming an emitter and a base on the backside of the silicon wafer by applying a dopant while melting the backside of the silicon wafer; Forming a SiO ₂ oxide film on a back surface of the silicon wafer; Forming a contact hole in the SiO ₂ oxide film in the region where the emitter and the base are formed; Forming a metal electrode in each contact hole; characterized in that it comprises a.

In addition, the method of manufacturing a back electrode solar cell according to the present invention, in the back electrode solar cell to form both the emitter and the base on the back of the silicon wafer, any of the emitter and base on the back of the silicon wafer using a diffusion process Forming one; Forming a remaining one of the emitter and the base on the back side of the silicon wafer by applying a dopant while melting the back side of the silicon wafer using a laser chemical process (LCP); Forming a SiO ₂ oxide film on a back surface of the silicon wafer; Forming a contact hole in the SiO ₂ oxide film in the region where the emitter and the base are formed; And forming a metal electrode in each contact hole.

A portion of the back surface of the silicon wafer is melted through the laser of the laser chemical process (LCP), and at the same time, the dopant is formed by being diffused and recrystallized in the molten portion.

In addition, the manufacturing method of the back electrode solar cell, forming a barrier hole around at least one of the emitter and the base; While forming a SiO ₂ oxide film on the backside of the silicon wafer, the SiO ₂ layer may be implanted into the barrier hole to form an SiO ₂ barrier to prevent overlap between the emitter and the base.

In addition, the method for manufacturing a back electrode solar cell according to the present invention comprises: forming a SiO ₂ oxide film on a back surface of a silicon wafer in a back electrode solar cell forming both an emitter and a base on a back surface of a silicon wafer; Melting and penetrating a portion of the SiO ₂ oxide film using a laser; And forming a emitter and a base by applying a dopant while melting the surface of the silicon wafer exposed through the SiO ₂ oxide film through a laser chemical process (LCP).

In addition, the manufacturing method of the back electrode solar cell according to the present invention, in the back electrode solar cell to form both the emitter and the base on the back of the silicon wafer, the back surface of the wafer through a diffusion process or laser chemical process (LCP) process Forming either an emitter and a base; Forming a SiO ₂ oxide film on a back surface of the silicon wafer; Melting and penetrating a portion of the SiO ₂ oxide film using a laser; And applying the dopant while melting the surface of the silicon wafer exposed through the SiO ₂ oxide film through a laser chemical process (LCP) to form the other of the emitter and the base.

Here, the step of forming a metal electrode in the portion through which the SiO ₂ oxide film; preferably comprises a further comprising.

Further, before forming the SiO ₂ oxide film, barrier holes are formed around at least one of the region where the emitter and the base are to be formed on the rear surface of the silicon wafer; While forming a SiO ₂ oxide film on the back side of the silicon wafer, it is preferable to inject a SiO ₂ layer into the barrier hole to form an SiO ₂ barrier to prevent overlap between the emitter and the base.

In addition, during the melting of the SiO ₂ oxide film, the laser emits heat above the melting point of the SiO ₂ oxide film; When the SiO ₂ oxide film penetrates and exposes the surface of the silicon wafer, it is more preferably configured to emit heat through the laser at a temperature between the melting point of the single crystal silicon and the melting point of the SiO ₂ oxide film.

Meanwhile, whether the SiO ₂ oxide film is penetrated and the surface of the silicon wafer is exposed may be configured to detect the difference of the resistance value measured at the portion to which the laser is irradiated.

In addition, whether the SiO ₂ oxide film penetrates and exposes the surface of the silicon wafer may be configured to detect whether a preset laser irradiation time has elapsed through experiments.

And the back electrode solar cell according to the present invention is manufactured according to the above-described manufacturing method, characterized in that both the emitter and the base is formed on the back of the silicon wafer.

According to the present invention, it is possible to significantly reduce the manufacturing cost and manufacturing time by reducing the manufacturing process of the back electrode solar cell.

According to the present invention, the butting phenomenon between the emitter and the base is not caused by the SiO ₂ barrier.

According to the present invention, by sequentially controlling the temperature of the heat emitted from the laser, HAZ is not formed by blocking unnecessary heat transfer to the emitter or the base in the process of forming the contact hole.

1 is a cross-sectional view illustrating a method of manufacturing a back electrode solar cell according to a first embodiment of the present invention.
2 is a cross-sectional view illustrating a method of manufacturing a back electrode solar cell according to a second exemplary embodiment of the present invention.
3 is a cross-sectional view illustrating a method of manufacturing a back electrode solar cell according to a third exemplary embodiment of the present invention.
4 is a cross-sectional view illustrating a method of manufacturing a back electrode solar cell according to a fourth embodiment of the present invention.
5 is a cross-sectional view illustrating a method of manufacturing a back electrode solar cell according to a fifth exemplary embodiment of the present invention.
6 is a cross-sectional view illustrating a method of manufacturing a back electrode solar cell according to a sixth embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings a preferred embodiment of a method for manufacturing a back electrode solar cell according to the present invention will be described in detail.

In an embodiment of the present invention, a laser chemical process (LCP) is used. The LCP is a device for doping by simultaneously supplying a laser and a compound which is a p-type or n-type dopant. This device is a well-known device, and detailed description thereof will be omitted in the present embodiment.

Also, for convenience of description, a manufacturing process of a back electrode solar cell using an n-type silicon wafer will be described. The silicon wafer has a specific resistance of 1 Ωcm and a thickness of about 150 to 200 µm. However, the specific resistance and thickness do not have to be limited as in the above examples.

(First embodiment)

1 is a cross-sectional view illustrating a process of manufacturing a back electrode solar cell by performing doping by LCP according to the first embodiment of the present invention.

1A illustrates a silicon wafer 100 in which a cleaning process is completed for removing impurities after removing a damage formed on a surface of the wafer and performing a texturing process.

Next, a laser and a p-type dopant chemical are applied to the region where the emitter is to be formed on the back surface of the silicon wafer 100 using the LCP. Then, as the surface irradiated with the laser is melted, dopants are diffused into the molten portion and selectively doped according to the recrystallization process to form the emitter 110 of the p + layer. The state in which the emitter 110 of the p + layer is formed is shown in FIG. 1 (b).

Here, the compound for forming the emitter 110 of the p + layer may include p-type dopants such as B, Al, Ga, and the like. The sheet resistance of the p + layer is preferably doped at a high concentration of 100 Ω / □ or less.

When the emitter 110 of the p + layer is formed, a laser and an n-type dopant compound are then applied to the region where the base is to be formed on the rear surface of the silicon wafer 100 using LCP. Then, as the surface irradiated with the laser is melted, dopants are diffused into the molten portion and selectively doped according to the recrystallization process to form a base 120 of the n + layer. This state is shown in Fig. 1 (c).

The chemical for forming the n + layer includes n-type dopants such as P and As. In this case, the base 120 of the n + layer should be separated from the emitter 110 of the p + layer. Although shown in the drawing to be connected to each other, substantially a step is formed to some extent, the emitter 110 and the base 120 are spaced apart. The reason for this is that when the p + layer and the n + layer are in contact with each other, a leakage current path is formed and the efficiency is lowered.

When the emitter 110 of the p + layer and the base of the n + layer are formed using the LCP, the number of laser groovings depends on the pitch of the silicon wafer 100. In addition, the doping concentration can be controlled according to the power of the laser, and the sheet resistance can be controlled according to the laser pulse energy density.

When the emitter 110 of the p + layer and the base 120 of the n + layer are formed using the LCP, the number of laser groovings depends on the pitch of the silicon wafer 100. The wavelength of the laser used at this time is 1064nm, 532nm, 355nm, but is not limited thereto. In addition, the shorter the pulse length of the laser, the less by-products or cracks on the surface. However, since the difference in the degree of surface grooving occurs according to the wavelength, pulse length, and duration of the laser, the laser control parameters are correlated and must be properly adjusted according to the situation.

The width of the laser grooving is adjustable by the diameter of the nozzle from which the chemical is injected. In addition, the doping concentration can be adjusted according to the type and concentration of the liquid, and the sheet resistance can be controlled according to the laser power and the laser pulse energy density.

For reference, the base 120 of the n + layer may be formed first. Since LCP is used, it is possible to change only the dopant type.

On the other hand, for more efficient formation of the emitter 110 and the base 120, it is possible to limit the power of the laser and the concentration of the dopant injected.

After the emitter 110 and the base 120 are formed using the LCP, an n + dope layer 130 is formed on the entire surface of the silicon wafer 100 as shown in FIG. In order to form the n + dope layer 130 only on the front surface, a diffusion mask (not shown) is formed on the rear surface of the silicon wafer 100. The diffusion barrier layer is preferably formed of a SiO ₂ layer by PECVD.

When the n + dope layer 130 is formed, the diffusion barrier layer is removed and the surface is cleaned with a cleaning liquid.

When the diffusion barrier is removed, as shown in FIG. 1 (e), SiO ₂ may perform an insulation function and a passivation film on the back and front surfaces of the silicon wafer 100 using a thermal oxidation process. Oxide films 140a and 140b are formed.

An anti-reflection film 150 is formed on the SiO ₂ oxide film 140b formed on the entire surface of the silicon wafer 100 among the SiO ₂ oxide films 140a and 140b. It is shown in Figure 1 (f).

Next, a contact hole 160 is formed using a laser so that the surface electrodes of the emitter 110 and the base 120 can be interconnected. The contact hole 160 is formed to expose a part of the emitter 110 and the base 120 to the outside, as shown in FIG.

When the contact hole 160 is formed, an electrode may be formed. A base electrode 170a is formed in the contact hole 160 formed in the base, and an emitter electrode 170b is formed in the contact hole 160 formed in the emitter.

Such electrode formation may be formed using electrolytic or electroless plating, or may be formed using photolithography and metal layer etching.

(2nd Example)

2 is a cross-sectional view illustrating a process of manufacturing a back electrode solar cell by doping by LCP according to a second embodiment of the present invention.

In the second embodiment, the overall process is the same as that of the first embodiment described above, except that both the emitter and the base are not formed by using LCP, and one of the emitter and the base is formed through a diffusion process, Only the other one is formed using the LCP as in the first embodiment described above is different.

Thus, the second embodiment will be described based on the process that is different from the first embodiment described above.

First, the silicon wafer 200 is shown in Figure 2 (a) after the cleaning process is completed for removing impurities, after removing the damage formed on the surface during the wafer cutting, the texturing process.

In this state, the emitter 210 of the p + layer is formed in a diffusion process using a liquid dopant source such as 'BBr3' in the entire region or the rear surface of the silicon wafer 200. This is shown in Figure 2 (b). The diffusion process may be a diffusion method using a tube type diffusion path, or an in-line diffusion diffusion path such as spray diffusion, spin on diffusion, or the like. .

When the emitter 210 of the p + layer is formed, a laser and an n-type dopant compound are applied to the region of the back surface of the silicon wafer 200 where the base is to be formed by the LCP method.

Then, the surface irradiated with the laser is melted and the dopants are diffused into the molten portion, and then doping is selectively performed according to the recrystallization process to form the base 220 of the n + layer as shown in FIG. At this time, the n + layer should be formed away from the p + layer. The compound for forming the base 220 of the n + layer includes an n-type dopant such as P or As.

Subsequently, the n + dope layer 230 is formed on the entire surface of the silicon wafer 200, the SiO ₂ oxide films 240a and 240b are formed, the antireflection film 250 is formed, and the contact hole 260 is formed according to the process of forming and removing the diffusion barrier. Formation and forming processes of the base electrode / emitter electrode 270a and 270b are shown in FIG. 1.

However, since the p + layer is formed by a diffusion process, it is preferable to remove phosphosilicate glass (PSG: Phosphor-Silicate Glass) formed as a by-product on the surface during the diffusion process. The PSG removal must be performed before the SiO ₂ oxide films 240a and 240b are formed.

(Third Embodiment)

3 is a cross-sectional view illustrating a process of manufacturing a back electrode solar cell by doping by LCP according to a third embodiment of the present invention.

3A illustrates a silicon wafer 300 in which a cleaning process is completed for removing impurities after removing a damage formed on a surface of the wafer and performing a texturing process.

Next, as shown in FIG. 3B, a SiO ₂ oxide film 330 is formed on the back surface of the silicon wafer 300. Alternatively, after the n + dope layer is formed on the front surface of the silicon wafer 300, the SiO ₂ oxide film 330 may be formed on each of the front and rear surfaces of the wafer 300. In the third embodiment, detailed description of the formation of the SiO ₂ oxide film and the anti-reflection film formed on the entire surface of the silicon wafer 300 is omitted.

The emitter 310 is formed by applying a laser and a p-type dopant chemical to a region where an emitter is to be formed in the SiO ₂ oxide layer 330 formed on the rear surface of the silicon wafer 300 using LCP. . That is, after the SiO ₂ oxide film 330 is melted through laser irradiation and the surface of the wafer 300 exposed to the outside is melted, dopants applied together with the laser irradiation are diffused into the molten portion of the wafer 300. The doping process is selectively doped to form emitter 310 of the p + layer. The state in which the emitter 310 of the p + layer is formed is shown in FIG. 3 (c). In addition, a portion of the SiO ₂ oxide layer 330 penetrated in the process of forming the emitter 310 becomes a contact hole 360a for forming an emitter electrode.

That is, the emitter formation 310 and the contact hole 360a for the emitter electrode may be simultaneously formed through a single laser irradiation, thereby significantly reducing the number of solar cell manufacturing processes.

When the emitter 310 of the p + layer is formed, a laser and an n-type dopant chemical are formed in a region where a base is to be formed among SiO ₂ oxide films 330 formed on the back surface of the silicon wafer 300 by using LCP. chemical) to form the base 320 of the n + layer. At this time, the emitter 310 and the base 320 do not overlap.

As such, when the surface of the wafer 300 is melted after the SiO ₂ oxide layer 330 is melted through laser irradiation, dopants applied together with the laser irradiation are diffused into the molten portion of the wafer 300, and thus, selective according to the recrystallization process. Doped to form a base 320 of n + layer. This state is shown in Fig. 1 (d). In addition, a portion of the SiO ₂ oxide layer 330 that penetrates during the formation of the base 320 becomes a contact hole 360b for forming a base electrode.

As such, the process of using the LCP completed the formation of the emitter 310 and the base 320, the formation of the SiO ₂ oxide film 330, and the formation of the contact holes 360a and 360b. The metal electrodes 370a and 370b are formed on the 360a and 360b by electrolytic or non-electrolytic plating.

(Example 4)

4 is a cross-sectional view illustrating a process of manufacturing a back electrode solar cell by performing doping by LCP according to the fourth embodiment of the present invention.

In the fourth embodiment, the overall process is the same as in the above-described third embodiment, except that neither the emitter and the base are formed by using LCP, but one of the emitter and the base is formed through a diffusion process, Only the other one is formed using the LCP, as in the third embodiment described above.

Therefore, the fourth embodiment will be described based on the process that is different from the above-described third embodiment.

4A illustrates a silicon wafer 400 in which a cleaning process is completed for removing impurities after removing a damage formed on a surface of the wafer and performing a texturing process.

In this state, the emitter 410 of the p + layer is formed in a diffusion process using a liquid dopant source such as 'BBr3' in the entire region or the rear surface of the silicon wafer 400. This is shown in Figure 4 (b).

Next, as illustrated in FIG. 4C, an SiO ₂ oxide film 430 is formed on the back surface of the silicon wafer 400 on which the emitter is formed.

Next, a laser and an n-type dopant chemical are applied to a region where the base is to be formed in the SiO ₂ oxide film 430 formed on the back surface of the silicon wafer 400 using LCP to thereby form the base 420 of the n + layer. Form. This is shown in Figure 4 (d).

As shown in FIG. 4E, after the laser is irradiated to the SiO ₂ oxide film 430 in the region where the emitter 410 is formed, the contact hole 460a for the emitter electrode is formed, the emitter and the base The electrodes 470a and 470b are formed in the contact holes 460a and 460b of, respectively.

Meanwhile, unlike the above, the base 420 may be first formed through the diffusion process, and then the emitter 410 may be formed through the LCP process.

Next, after forming the emitter and the base on the back surface of the wafer using the LCP as in the first to fourth embodiments described above, an embodiment for solving the overlap problem between the emitter and the base will be described.

(Fifth Embodiment)

5 is a cross-sectional view illustrating a process of manufacturing a back electrode solar cell by performing doping by LCP according to the fifth embodiment of the present invention.

As in the first and second embodiments described above, the emitter 510 and the base 520 are previously formed on the back surface of the silicon wafer 500 through an LCP process or a diffusion process. This is shown in Figure 5 (a). Thereafter, as shown in FIG. 5B, a barrier hole 540 having a predetermined depth is formed around the regions of the emitter 510 and the base 520.

The bearer hole 540 may be etched using a mask or may be formed using a laser. Meanwhile, the barrier hole 540 is a space for injecting the SiO ₂ layer in a subsequent SiO ₂ oxide film formation process, and may be formed only around one of the emitter 510 and the base 520. .

As such, after the barrier hole 540 is formed around at least one of the emitter 510 and the base 520, the SiO ₂ oxide layer 530 is formed on the back surface of the silicon wafer 500. During the oxide film formation, the SiO ₂ layer is also filled in the barrier hole 540 to form the SiO ₂ barrier 542. This is shown in Figure 5 (c).

Since the SiO ₂ barrier 542 more clearly distinguishes between the emitter 510 and the base 520, there is no fear of overlapping between the emitter 510 and the base 520, and thus, The efficiency can be maximized.

After the SiO ₂ barrier 542 is formed around at least one of the emitter 510 and the base 520 as described above, the SiO ₂ oxide film 530 is irradiated with a laser as shown in FIG. Contact holes for formation are formed in each emitter 510 and base 520, and metal electrodes 570a and 570b are formed in each contact hole by electrolytic or non-electrolytic plating.

(Sixth Embodiment)

6 is a cross-sectional view illustrating a process of manufacturing a back electrode solar cell by performing doping by LCP according to a sixth embodiment of the present invention.

In the state in which the emitter and the base are not formed as in the above-described third and fourth embodiments, the barrier hole 640 having a predetermined depth is formed on the rear surface of the silicon wafer 600 around the region where the emitter and the base are to be formed. do. That is, unlike the fifth embodiment described above, the barrier hole 640 is formed before the emitter and the base are formed, and the barrier hole 640 is formed around the area where the emitter or the base to be formed is formed. The barrier hole 640 may be etched using a mask or may be formed using a laser. This is shown in Figure 6 (a).

Next, an SiO ₂ oxide film 630 is formed on the back surface of the silicon wafer 600. During the oxide film formation, the SiO ₂ layer is also filled in the barrier hole 640 to form the SiO ₂ barrier 642. This is shown in Figure 6 (b).

Thereafter, as in the above-described third or fourth embodiment, the contact holes 660a and 660b are formed in the SiO ₂ oxide film 630 through the LCP process, and the emitter 610 and the base 620 are simultaneously formed. do. This is shown in Figure 6 (c).

Since the SiO ₂ barrier 642 more clearly distinguishes between the emitter 610 and the base 620, there is no fear of overlapping between the emitter 610 and the base 620, and thus, The efficiency can be maximized.

In addition, since the emitter 610 and the base 620 may be defined and standardized through the SiO ₂ barrier 642, mass production of the back electrode solar cell may be facilitated.

Finally, the embodiment for blocking the generation of heat affected zones (HAZ) on the surface of the silicon wafer in the process of simultaneously forming the emitter and base and the contact hole on the back surface of the wafer using the LCP .

(Seventh Embodiment)

As in the above-described third embodiment, in the process of simultaneously performing emitter and base formation and contact hole formation on the back surface of the wafer using the LCP, the high temperature heat is generated by the melting point difference between the silicon wafer and the SiO ₂ oxide film. In order not to affect the wafer surface directly or indirectly, it is desirable to be configured to be able to sequentially control the intensity of heat emitted through laser irradiation.

That is, the high-temperature heat emitted from the laser melt to SiO ₂ oxide film, when the SiO ₂ oxide film is all melted the surface of the silicon wafer detection, tteurinda immediately dropped sharply to heat emitted by the laser. This allows the surface of the silicon wafer to be melted to enable emitter or base formation, while preventing the generation of heat affected zones (HAZ) for the silicon wafer.

For example, a laser beam at a high temperature melting point of more than 1710 ℃ of SiO ₂ to dissolve the SiO ₂ oxide film. Then, when all of the SiO ₂ oxide film is melted and the surface of the silicon wafer is sensed, the temperature of heat emitted from the laser is lowered to a temperature below the melting point of SiO ₂ , preferably about 1414 ° C., which is the melting point of single crystal silicon. As a result, the occurrence of heat affected zones (HAZs) due to rapid high temperature heat is prevented, and at the same time, the surface of the silicon wafer is melted to diffuse the dopants.

Meanwhile, as a method of detecting whether the SiO ₂ oxide film is melted and the surface of the silicon wafer is exposed, the SiO ₂ oxide film may be detected using a difference in resistance between the SiO ₂ oxide film and single crystal silicon. That is, by determining whether the resistance detected through the resistance sensor is the resistance value of the SiO ₂ oxide film or the resistance value of the single crystal silicon, it is possible to detect whether the silicon wafer surface is exposed.

Alternatively, statistical analysis based on experimental data can be used to detect the exposure of the silicon wafer surface. In other words, by analyzing the silicon wafer on which the SiO ₂ oxide film of a certain thickness was formed through an experiment in advance, it was statistically determined that after some time, the SiO ₂ oxide film melted to expose the silicon wafer surface. Clean up. Through the statistical data, the exposure time of the silicon wafer surface is set in advance, and when the predetermined time elapses during the laser irradiation process according to actual solar cell manufacturing, it is determined that the surface of the silicon wafer is exposed.

While the invention has been shown and described with respect to the specific embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims. Anyone with it will know easily.

100 silicon wafer 110 emitter
120: base 130: front n + dope layer
140a, 140b: SiO ₂ oxide film 150: antireflection film
160: contact hole 170a, 170b: base electrode, emitter electrode

Claims (11)

In the back electrode solar cell forming both the emitter and the base on the back of the silicon wafer,
Forming one of an emitter and a base on the back side of the silicon wafer by applying a dopant while melting the back side of the silicon wafer using a laser chemical process (LCP) or by a diffusion process;
Forming the other one of the emitter and the base on the back side of the silicon wafer by applying a dopant while melting the back side of the silicon wafer using the LCP;
Forming a barrier hole around at least one of the emitter and the base;
The method comprising, forming a SiO ₂ oxide film on the rear surface of the silicon wafer, by implanting the SiO ₂ layer to form a hole barrier SiO ₂ barrier for preventing overlap between an emitter and a base;
Forming a contact hole in the SiO ₂ oxide film in the region where the emitter and the base are formed; And
Forming a metal electrode in each contact hole;
Method of manufacturing a back electrode solar cell comprising a. The method of claim 1,
A portion of the back surface of the silicon wafer is melted through the laser of the laser chemical process (LCP), and at the same time, a dopant is formed by diffusing and recrystallization in the molten portion. delete In the back electrode solar cell forming both the emitter and the base on the back of the silicon wafer,
Before forming the SiO ₂ oxide film, forming a barrier hole around at least one of the region where the emitter and the base are to be formed on the rear surface of the silicon wafer;
The method comprising, forming a SiO ₂ oxide film on the rear surface of the silicon wafer, by implanting the SiO ₂ layer to form a hole barrier SiO ₂ barrier for preventing overlap between an emitter and a base;
Melting and penetrating a portion of the SiO ₂ oxide film using a laser;
Forming at least one of an emitter and a base by applying a dopant while melting the surface of the exposed silicon wafer through the SiO ₂ oxide film through a laser chemical process (LCP); And
Forming a metal electrode at a portion through which the SiO ₂ oxide film is penetrated;
Method of manufacturing a back electrode solar cell comprising a. The method of claim 4, wherein
Before forming the SiO ₂ oxide film on the backside of the silicon wafer,
Forming one of an emitter and a base on the back side of the silicon wafer by applying a dopant while melting the back side of the silicon wafer using a laser chemical process (LCP) or by a diffusion process;
Method of manufacturing a back electrode solar cell further comprising a. delete The method of claim 4, wherein
In the process of melting the SiO ₂ oxide film release heat over the melting point of the SiO ₂ oxide film by a laser and;
When the SiO ₂ oxide film penetrates to expose the surface of the silicon wafer, a method of manufacturing a back electrode solar cell, characterized in that configured to emit a heat of temperature between the melting point of the single crystal silicon and the melting point of the SiO ₂ oxide film through a laser. The method of claim 7, wherein
Method of manufacturing a back-electrode solar cell, characterized in that configured to detect whether the SiO ₂ oxide film penetrated to expose the surface of the silicon wafer through the difference in the resistance value measured at the laser irradiation site. The method of claim 7, wherein
The method of manufacturing a back electrode solar cell, characterized in that the SiO ₂ oxide film penetrates and exposes the surface of the silicon wafer through an experiment to detect whether a predetermined laser irradiation time has elapsed. Forming one of an emitter and a base on the back side of the silicon wafer by applying a dopant while melting the back side of the silicon wafer using a laser chemical process (LCP) or by a diffusion process; Forming the other one of the emitter and the base on the back side of the silicon wafer by applying a dopant while melting the back side of the silicon wafer using the LCP; Forming a barrier hole around at least one of the emitter and the base; The method comprising, forming a SiO ₂ oxide film on the rear surface of the silicon wafer, by implanting the SiO ₂ layer to form a hole barrier SiO ₂ barrier for preventing overlap between an emitter and a base; Forming a contact hole in the SiO ₂ oxide film in the region where the emitter and the base are formed; Forming a metal electrode in each contact hole; is manufactured according to a manufacturing method comprising a, the back electrode solar cell, characterized in that both the emitter and the base is formed on the back of the silicon wafer. Before forming the SiO ₂ oxide film, forming a barrier hole around at least one of the region where the emitter and the base are to be formed on the rear surface of the silicon wafer; The method comprising, forming a SiO ₂ oxide film on the rear surface of the silicon wafer, by implanting the SiO ₂ layer to form a hole barrier SiO ₂ barrier for preventing overlap between an emitter and a base; Melting and penetrating a portion of the SiO ₂ oxide film using a laser; Forming at least one of an emitter and a base by applying a dopant while melting the surface of the exposed silicon wafer through the SiO ₂ oxide film through a laser chemical process (LCP); Forming a metal electrode in the portion through which the SiO ₂ oxide film; is manufactured according to a manufacturing method comprising a, the back electrode solar cell, characterized in that both the emitter and the base is formed on the back of the silicon wafer.

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