KR20110083641A - Methods and systems of manufacturing photovoltaic devices - Google Patents

Abstract

A system for manufacturing a photovoltaic device comprising a semiconductor wafer, the system comprising: a laser device arranged to generate a laser beam; And a laser scanning device arranged to scan the laser beam on the wafer to locally heat the surface of the wafer. The laser scanning apparatus includes: a beam splitting module for dividing a laser beam into at least two sub beams having the same laser power; At least two scanners arranged to control the sub-beams to be scanned along a predetermined scan path defined on the wafer; And at least two lenses arranged such that the controlled sub-beams are focused at a focal position coinciding with the predetermined scan path.

Description

Manufacturing method and system of photovoltaic device {Methods and Systems of manufacturing Photovoltaic devices}

The present invention relates to a manufacturing technique of a photovoltaic device, and more particularly, to a manufacturing method and a manufacturing system of a photovoltaic device.

Currently, many photovoltaic modules are formed of photovoltaic devices (eg, solar cells) based on silicon wafers. Increasing the efficiency of silicon cells and lowering costs using relatively thin wafers is extremely important. As a step in the fabrication of photovoltaic devices based on silicon wafers, there is a process that allows the contact to be metallized through screen-printing. However, as photovoltaic device manufacturers improve battery efficiency and make wafers thinner and lower costs, the limitations of the screen printing process are also being revealed. For example, screen printing contact technology causes at least the following defects. (a): High shading loss due to wide line width (100-200 μm) leads to low efficiency solar cell formation, and (b): physical pressure applied during screen printing process Increases production loss of thin wafers (thickness less than 200 μm).

In addition, for 125 x 125 mm wafers, producing a photovoltaic device is a high yield process that produces 1400 wafers approximately every hour. Any new process, system or method must meet the high yield requirements in the fabrication of photovoltaic devices.

According to one aspect of the invention, there is provided a system for manufacturing a photovoltaic device comprising a semiconductor wafer. The system includes a laser device arranged to generate a laser beam; And a laser scanning device arranged to scan a laser beam on the wafer to locally heat the wafer surface; It may include.

According to another aspect of the present invention, a method of manufacturing a photovoltaic device is provided. The photovoltaic device comprises a semiconductor wafer and the semiconductor wafer comprises: a semiconductor substrate; An emitter layer formed on the surface of the semiconductor substrate; And a dielectric layer overlying the emissive layer surface. The method includes forming a dopant source material layer on the surface of the dielectric layer; By locally heating the wafer surface through a laser beam to define a plurality of openings through the dielectric layer and to melt the substrate surface underlying the dielectric layer, dopants contained in the dopant raw material layer diffuse through the openings into the molten substrate. Thereby forming heavily doped zones; And depositing the conductor in the heavily doped region; It may include.

According to another aspect of the present invention, a method of processing a wafer through laser scanning is provided. The method includes partitioning the wafer into at least two regions having the same size; And scanning the regions through one or a plurality of laser beams, respectively.

According to another aspect of the present invention, a method of processing a wafer through laser scanning is provided. The method includes moving the wafer along one direction at a constant speed; And controlling the laser beam in a bow-tie pattern along the pattern scan path to form a straight pattern on the wafer; Wherein the scanning range of the laser beam in the wafer movement direction is defined by the pitch of the scan path.

1 is a flowchart illustrating a method of manufacturing a photovoltaic device according to an embodiment of the present invention.
2A to 2D are exemplary views illustrating steps of manufacturing a photovoltaic device according to an embodiment of the present invention.
3 shows the range of interaction between the laser beam intensity and the wafer surface material being processed.
4 is an exemplary view illustrating a manufacturing system of a photovoltaic device according to a specific embodiment of the present invention.
5 is an exemplary view illustrating a manufacturing system of a photovoltaic device according to another specific embodiment of the present invention.
6A through 6D are exemplary views illustrating a method of processing a wafer through laser scanning according to another exemplary embodiment of the present invention.
6E is an exemplary view illustrating a method of processing a wafer through laser scanning according to another exemplary embodiment of the present invention.
6F is an exemplary view showing a method of processing a wafer through laser scanning according to another embodiment of the present invention.
7A to 7C are exemplary views illustrating a stitching method of processing a wafer through laser scanning according to an exemplary embodiment of the present invention.
8A through 8B are exemplary views illustrating a method of processing a wafer through laser scanning according to another selectable embodiment of the present invention.

1, and 2a to 2d, a method of manufacturing a photovoltaic device according to an aspect of the present invention. According to the method, a semiconductor (for example, silicon) wafer having a substrate 100 and an emission layer 105 is provided, wherein the emission layer 105 is formed by lightly diffusing a dopant onto the substrate 100. do. The polarity of the dopant and the polarity of the dopant used in the substrate are opposite to each other to form a p-n junction between the emission layer 105 and the substrate 100. And forming a dielectric layer 101 on the top surface of the radiation layer 105, which may be a passivation film made of silicon oxide and / or silicon nitride, and may also be used as an antireflection coating (ARC). have. The process of forming the emissive layer 105 and the dielectric layer 101 may be performed through any known technique that may be used.

Then, a dopant raw material layer 104 (see 20 in Fig. 1) is formed on the upper surface of the dielectric layer 101. The polarity of the dopant included in layer 104 and that of emissive layer 105 are the same. Referring to FIG. 2B, the wafer surface is processed through a laser beam to melt the substrate in some regions where metal contact is formed with the dielectric layer 101. Specifically, dielectric layer 101 is opened to define a plurality of openings such that dopants contained in layer 104 can diffuse through the openings into the substrate. As the molten substrate cools and recrystallizes, the dopant remains in the substrate to form a plurality of heavily doped regions in the substrate.

Referring to FIG. 2C, after the laser processing step, only the dopant raw material layer is dissolved and the wafer is cleaned in a solution that does not damage the dielectric layer 101 to remove the dopant raw material layer 104. Next, referring to FIG. 2D, a heavily doped region exposed to the substrate (eg, by electroplating, electroless plating, or heating a metal-containing paste to form a metal contact, etc.) For example, a metallization step (40 in FIG. 1) is performed to form a metal semiconductor contact by depositing a conductor 107 on silver, nickel and / or copper, and the like. In the metallization step, the dielectric layer 101 serves as a self-aligned mask that metallizes the contacts through openings in some molten regions (metal contacts are formed therein). can do.

Those skilled in the art will understand that the wafer should be kept as clean as possible both before and after the dopant raw material layer 104 is formed, which is contaminants, particularly contaminants larger than a few microns in size, can disperse and absorb laser energy. This is because the material melting efficiency is lowered and high impedance is generated at the interface between the metal and the substrate. Therefore, it is desirable to minimize the time between the dopant raw material layer forming step and the laser processing step so that contaminants do not adhere to the wafer.

According to one embodiment of the invention, the intensity of the laser beam focused on the wafer surface must be maintained high enough so that the substrate surface melts and only a very small vaporization is produced. When the substrate surface is melted, very few additional defects or no additional defects are created on the wafer. Laser processing according to the present embodiment does not produce clear grooves on the wafer surface as compared to the conventional laser groove buried contact (LGBC) method. According to one specific embodiment, the surface doping concentration of the heavily doped regions formed by the method of the present invention may reach or exceed 10 ¹⁹ cm ⁻³ , while substantially no new defects are added to the wafer. .

3 shows the range of interaction between the laser beam intensity and the processed wafer material when the substrate material is silicon. The melting point of silicon is about 1414 ° C and the vaporization temperature is about 3217 ° C. The laser beam intensity graph is divided into ranges 112, 113, and 114 according to the melting threshold and the vaporization threshold of silicon. Range 112 is a heating range where the wafer surface is irradiated to a temperature below the melting threshold. Thus, the silicon remains in a solid state, but the dielectric layer 101 is partially damaged, creating unwanted heat-affected zones (HZAs) on the wafer surface. Range 113 is the melting range, where the wafer surface is heated to a temperature above the melting threshold and below the vaporization threshold. As indicated by arrow 110, a portion of the silicon surface within range 113 changes to a liquid state. As indicated by arrow 111, range 114 is a vaporization range where the wafer surface is heated to a temperature above the vaporization threshold and a portion of the silicon surface is vaporized. Vaporization can reduce the surface doping concentration of the substrate, create defects on the wafer surface, and can also penetrate the doped layer resulting in electrical shunting between the metal contact and the substrate. Therefore, the intensity of the laser beam focused on the wafer surface must be maintained such that the wafer surface can be heated to a temperature above the silicon melting threshold and below the silicon vaporization threshold. 3 shows a laser beam intensity graph, where the distal portion of the laser beam intensity graph can be cut to minimize the HAZ effect and the top portion of the laser beam intensity graph can be smoothed to prevent silicon vaporization. .

In addition, when the laser beam is scanned so that the wafer surface is heated, the size of each dielectric layer opening is determined by the spot size D of the laser beam focused on the wafer surface. In order to obtain a small spot size, the laser beam can be selected in TEM00 mode. The opening sizes thus obtained are generally in the range of 10 to 25 microns. The size of such openings is generally smaller than those obtainable through conventional screen printing methods.

Although the method has been described above with particular reference to the manufacture of frontside contacts, the methods described herein may be used to form backside contacts in a valid fashion.

According to another aspect of the invention, a system for manufacturing a photovoltaic device includes a laser device arranged to generate a laser beam; And a laser scanning device arranged to scan a laser beam on a surface of a target object (eg, a semiconductor wafer). According to one embodiment of the invention, the system can be arranged to manufacture a photovoltaic device in the manner described above.

Referring to FIG. 4, a system 200 for manufacturing a photovoltaic device includes a laser device 202 arranged to generate a laser beam 230; And a laser scanning device that includes a beam separation module 205, a scanner 208, and a lens 209. The beam splitting module 205 separates the laser beam 230 generated by the laser apparatus 202 into a plurality of sub-beams having substantially the same intensity. For convenience of description, two sub-beams 232 will be described as an example in FIG. 4. Each sub beam can be controlled from a corresponding scanner 208 and scanned along a predetermined scan path on the wafer. A set of lenses 209 may be provided to allow the sub-beams to focus on the wafer surface. According to the system shown in FIG. 4, high throughput of the system can be realized by collectively processing two or more wafers through the plurality of sub-beams 233.

The laser device 202 may be a quasi-continuous wave (QCW) laser device, and its pulse repetition rate may be 1 MHz or more. According to one embodiment of the invention, the QCW laser device is a picosecond laser device. In one specific embodiment, the pulse width of the picosecond laser device is about 15 picoseconds. The laser device 202 may be a continuous wave (CW) laser device. In an exemplary embodiment, the laser device 202 generates a laser beam having the following features. (a) the wavelength is about 532 nm or smaller; (b) the beam mode is TEM00; (c) the beam quality factor M ² is about 1.3 or less; And (d) the beam output diameter is at least about 1 mm, preferably 2 mm or larger. The laser device 202 may be a UV laser device or a green laser device.

)이 약 75~99.99%가 되도록 레이저 빔을 스캐닝한다. 일반적으로 반복율

은 관계식

를 만족시켜야 하는데, 여기에서 D는 웨이퍼 표면 상에 집광된 레이저 빔 스팟 크기이다. 예시적인 일 실시예에 있어서, 빔 스팟 크기（D）는 약 10㎛ 내지 약 50㎛ 사이이고, 웨이퍼 표면에서 평균 레이저 파워 밀도(laser power density)는 약 2MW/cm²내지 약 20MW/cm² 사이이다. The scanner 208 may be a two-dimensional (2-D) XY or three-dimensional (3-D) XYZ galvanometer scanner, which scans the laser beam at a speed of about V = 2000 mm / s to 3000 mm / s on the wafer surface. Can be. In addition to scanning the laser within the XY plane, the 3-D XYZ scanner can control the focus height (Z) so that the focal point is placed on the wafer surface in a real time format. Lens 209 may be an f-theta lens or a telecentric scan lens. The diameter of the laser beam 232 at the entrance pupil of the scanner 208 may be about 8 mm to 16 mm. For pulse quasi-continuous wave laser devices, the scanner can

The laser beam is scanned so that) is about 75-99.99%. Typical repetition rate

Silver relation

Where D is the laser beam spot size focused on the wafer surface. In one exemplary embodiment, the beam spot size (D) is between about 10 μm and about 50 μm, and the average laser power density at the wafer surface is between about 2 MW / cm ² and about 20 MW / cm ² . to be.

보다 높아야 한다. 그런데 레이저 빔(230)은 복수 개의 서브 빔(232)으로 분리되므로 도 4에 도시된 시스템(200)은 레이저 파워가 부족한 현상이 발생할 수 있다. 웨이퍼 표면 상에 집광된 레이저 빔 스팟 크기(D)와 렌즈의 초점거리 사이의 관계는

로 알려져 있다. 그러므로, 웨이퍼 표면에서 레이저 빔 세기 문턱값

의 특징은

혹은

이다. 그러므로 레이저 파워가 부족한 현상을 방지하도록 렌즈(209)의 초점거리를 비교적 작게 유지하거나 혹은

를 비교적 낮게 유지하여 한다. 그러나 상술한 바와 같이, 일부 웨이퍼 표면을 기판 재료의 용융 온도까지 가열하기 위하여 문턱값이 너무 낮을 수 없다. 그러므로 레이저 파워가 부족한 현상을 방지하기 위하여, 렌즈(209)가 비교적 작은 초점거리를 가지도록 하여야 한다. 한편, 초점거리가 너무 작으면 시스템의 광학 수차(optical aberration)가 심해질 수 있다. 이런 경우, 스캐닝 품질은 일반적으로 레이저 빔이 시스템 스캔 필드(scan field)의 중심 영역에서 멀어짐에 따라 저하된다. 그러므로 실제 하드웨어의 제한을 받아 가공의 균일성이 저하되는 것을 야기시킬 수 있다. 작은 초점거리를 유지하는 것과 균일한 가공 결과를 획득하는 것 사이에 평형이 존재한다. 본 발명의 일 실시 방식에 따르면, 렌즈의 초점거리는 약 160mm내지 약 300mm 사이에 있다. 본 발명의 구체적인 일 실시 방식에 따르면, 초점거리는 250mm이다. As such, in order to melt the wafer surface, the intensity of the laser beam focused on the wafer surface must be maintained such that the wafer surface can be heated to a temperature above the substrate material melting threshold. That is, the intensity of the laser beam is the intensity threshold

It must be higher. However, since the laser beam 230 is divided into a plurality of sub beams 232, the system 200 illustrated in FIG. 4 may have a shortage of laser power. The relationship between the laser beam spot size (D) focused on the wafer surface and the focal length of the lens

Known as Therefore, the laser beam intensity threshold at the wafer surface

Characteristic of

or

to be. Therefore, the focal length of the lens 209 is kept relatively small to prevent the phenomenon that the laser power is insufficient, or

Should be kept relatively low. However, as mentioned above, the threshold cannot be too low to heat some wafer surfaces to the melting temperature of the substrate material. Therefore, in order to prevent the phenomenon that the laser power is insufficient, the lens 209 should have a relatively small focal length. On the other hand, if the focal length is too small, the optical aberration of the system may be severe. In this case, the scanning quality generally degrades as the laser beam moves away from the center region of the system scan field. Therefore, it is possible to cause the uniformity of processing to be deteriorated under the limitation of actual hardware. There is an equilibrium between maintaining a small focal length and obtaining a uniform processing result. According to one embodiment of the invention, the focal length of the lens is between about 160 mm and about 300 mm. According to a specific embodiment of the present invention, the focal length is 250 mm.

5 shows a manufacturing system of a photovoltaic device according to another specific embodiment of the present invention. Referring to FIG. 5, in addition to the device shown in FIG. 4, the system 200 includes a beam expander 204 arranged to enlarge the laser beam; And an attenuator 206 arranged to attenuate the power of the laser beam to a desired power level. The laser beam 230 may be enlarged through the beam expander 204 before being separated through the beam splitting module 205 and may also be attenuated through the attenuator 206 after passing through the splitting module 205. The system 200 includes a safety shutter 203 capable of selectively shutting off the laser; And / or a laser power meter 207 for monitoring the laser beam power.

Referring again to FIG. 5, the system 200 may include a laser mask 210 disposed to limit the scanning range of the laser beam. The laser mask 210 may prevent the laser beam from hitting a wafer area that should not be melted along the laser beam scan path. For example, an area such as a peripheral region on a wafer that must not melt along the turnaround paths of the laser beam when controlling the laser beam to move from one scan line to the next. The laser mask 210 may have a simple rectangular opening or more complex design. According to one exemplary embodiment, the mask is placed in sufficient proximity to the wafer to clearly define the end of the scan line. The vertical distance between the mask and the wafer may be less than 5 mm. The wafer 211 may be loaded onto the work bench 220 through vacuum chucks so that the wafer 211 may be planarized and processed into wafers. The work bench 220 may be, for example, a movable work bench such as an X-work bench and / or a Y work bench, and / or a Z work bench, and / or a rotary work bench. Although not shown in FIG. 5, the elements of system 200 (eg, laser device 202 other than laser mask 210, scanner 208, etc.) may be rigid and thermally stable. ) May be mounted on a plate (eg, MIC-6 aluminum plate or granite plate).

For convenience of description, the beam separation module 205 and the element located upstream of the beam separation module 205 in the system 200 are referred to as the beam processing main part, and the beam separation module 205 in the system 200. The device located downstream of the subfield is referred to as a beam processing sub-part. In another structure of the system shown in FIG. 5, the expander 204 may be included in the beam processing sub-part rather than the beam processing main-part. In another structure of the system shown in FIG. 5, the magnification of the laser beam 230 may be realized in multiple stages. For example, one or more beam expanders with the same or different magnification may be used. In another structure of the system shown in FIG. 5, if using a two-stage expander, one or two expander stages may be included in the beam processing sub-part rather than the beam-processing main part. In another structure of the system shown in FIG. 5, the laser power meter 207 may be located at different positions. For example, the laser power meter 207 may be located between the lens 209 and the wafer 211. In another structure of the system shown in FIG. 5, the beam processing sub-part may include only one laser power meter 207. Optionally, the laser power meter 207 may deviate from the optical path during wafer processing. In another structure of the system shown in FIG. 5, the attenuator 206 may be included in the beam processing main portion rather than in the beam processing sub portion. Additional optical elements such as turning mirrors can be used to change the direction of the laser beam.

In one specific embodiment of the present invention, the laser beam may be divided into three or more sub-beams having the same laser power to realize higher yield.

In another specific embodiment of the present invention, the system may not include a beam splitting module.

In another specific embodiment of the invention, the optical path in the system is an enclosed path and can be purified to block environmental contaminants through clean dry air (CDA) or nitrogen (N ₂ ). have.

In another specific embodiment of the present invention, the system maintains the cleanliness of the system and remains free of contaminants, such as lenses, such as lenses 209, in particular free of debris generated during wafer laser processing. It may include a removal structure.

In yet another specific embodiment of the present invention, the system may include a retention and capture structure that collects and captures excess doping chemicals from the wafer 211 to prevent system corrosion.

In another specific embodiment of the present invention, the polarization of the laser beam can be controlled via an adjustable polarizer (eg, quarter-wave or half-wavelength sheet) in the optical path.

For large wafers, for example industry standard 125x125mm, 156x156mm, or 210x210mm wafers, there are two problems to maintain the process window required by the present invention over the entire wafer. (a) Due to the limitations of the actual hardware of the lens 209 and the scanner 208, the laser beam spot size or laser beam intensity at the wafer surface generally decreases as the beam moves away from the center region of the system's scan field. The system has a limited "sweet spot" area located in the center of the scan field, which can provide optimum material processing results. (b) The combination of the short focal length f and the limitations of the actual hardware desired by the present invention (e.g., the limited scan angle of the scanner 208) allows the entire wafer to be processed with one scanning laser beam. Makes it difficult. In order to solve the above two problems in the method described below, it is intended to maintain the process window of the present invention over the entire area of the large wafer. The method described below can be combined with the system of the present invention to process a wafer.

6A through 6D are exemplary views illustrating a method of processing a wafer through laser scanning according to another exemplary embodiment of the present invention. 6A-6D, a large wafer is divided into four regions R1, R2, R3, and R4 that are substantially the same size. In FIGS. 6A to 6D, the number of regions is for illustrative purposes, and the wafer may be divided into as many different regions having substantially the same size. The wafer may be subjected to laser material processing for each region continuously under the “sweet spot” region of the scan field through the laser beam 233. It is possible to realize the required wafer movement by the movable worktable. The laser mask 210 may be used to prevent the laser beam from being heated in the wafer area that should not be processed along the laser beam scan path.

6E is an exemplary view illustrating a method of processing a wafer through laser scanning according to another exemplary embodiment of the present invention. Referring to FIG. 6E, the wafer is still divided into four regions for convenience of explanation. However, the wafer is processed through four laser beams, respectively. After the wafer has passed all four processing positions, all four regions of the wafer are finished processing. The wafer 211 may be divided into different numbers of regions having substantially the same size, and the number of laser beams used for processing the wafer may also be different. For example, the wafer may be processed through two, three, or six laser beams divided into six regions having substantially the same size.

6F is an exemplary view showing a method of processing a wafer through laser scanning according to another embodiment of the present invention. Referring to FIG. 6F, for convenience of description, each wafer is still divided into four regions having the same size, and can also be transported through the rotary work bench 220. Multiple areas on the wafer are processed through the same number of laser beams to optimize yield. According to the embodiment shown in FIG. 6F, the wafer area R1, R2 on the wafer by transferring the wafer by a rotating work bench 220 having six working positions P1, P2, P3, P4, P5, and P6. , R3, and R4) can be completed. The six work positions P1, P2, P3, P4, P5, and P6 may be symmetrical about the central axis line of the work bench 220 and may also be located around it. The wafers 211 may each be fixed at these working positions via a vacuum chuck. Working table 220 can be incrementally rotated at a rotational angle of 60 degrees to move the wafer from one position to the next, and also stop for a while at each position. When located at locations P2, P3, P4, and P5, wafer 211 is processed by four independent laser beams. Hereinafter, a machining process will be described with reference to the embodiment illustrated in FIG. 6F.

After the first wafer is loaded at position P1, work bench 220 is rotated 60 degrees to move the first wafer from position P1 to position P2 and stop. When the work bench 220 is stopped, the area R1 of the first wafer is processed by the laser beam. At the same time a second wafer is loaded at position P1. After the machining of the first wafer R1 is completed, the work bench 220 rotates again 60 degrees along the same direction to move the first wafer from the position P2 to the position P3 and the second wafer at the position P1. Move to position P2. As such, the region R2 of the first wafer is processed by the laser beam at position P3 and the region R1 of the second wafer is processed by the other laser beam at position P2.

The above steps are repeated until the first wafer is laser processed by four laser beams at positions P2, P3, P4, and P5. Through this wafer processing method, the wafer may sequentially pass through these positions and then be processed and unloaded at the position P6.

According to the embodiment shown in FIG. 6F, the number of laser beams and the number of regions to be processed on one wafer are equalized to optimize production. In another embodiment, only one laser beam is used to process a wafer having a plurality of regions. In this case, all areas of the entire wafer are processed by moving the laser beam or wafer with additional time and motion.

Referring back to FIG. 6F, the loading and unloading of the wafer may be performed during the laser processing process, thereby preventing additional delays from being added. In addition, by combining the rotary work station 220 and the four laser machining positions (P2, P3, P4, and P5) with each other, the system is capable of high throughput through one wafer loading and unloading operation. Can be. In addition, since the location P1 and the location P6 are physically adjacent to each other, the wafer can be loaded and unloaded with only one wafer handling apparatus to minimize the number of hardware required.

According to another embodiment, the loading and unloading positions P1 and P6 of the wafer may be combined into one if the wafer processing apparatus is fast enough to exchange the wafer within the wafer processing time. The rotation work table 220 has a rotation step size of 72 degrees instead of 60 degrees when only five wafer positions are provided.

Referring again to FIG. 6F, each of the four laser beams scans different regions R1, R2, R3, and R4 of the wafer, and the scanning order may differ from the order shown in FIG. 6F, with all four regions of the wafer. If all of the wafer positions on the rotary work bench 220 have passed, the machining is completed.

Referring back to FIG. 6F, the rotation direction of the work bench 220 may be clockwise or counterclockwise.

Referring back to FIG. 6F, the wafer 211 may be divided into different numbers of regions having substantially the same size and processed. The number of laser beams used for wafer processing and the number of regions on the wafer may be different.

7A through 7C are exemplary views illustrating a stitching method of processing a wafer through laser scanning according to one possible embodiment of the present invention. 7A to 7C, when the wafer is divided into a plurality of regions and laser processing is performed one region at a time, the stitching operation is generally a pattern generated on the wafer due to laser scanning (for example, a metal contact pattern). Their continuity must be maintained. 7A-7C, an exemplary embodiment of the front metal contact pattern and stitching method of the wafer 211 is shown. In order to form a metal contact pattern of fingerers 241 and busbars 242, wafer 211 through lines 243 has four regions (R1, R2, R3, and R4). Are separated by). Lines 243 also indicate overlapping areas between adjacent areas, and patterns may not be exactly aligned in the overlapping areas due to system-specific misalignment errors. According to FIG. 7B, the finger lines 241 are stitched to each other in an "X" shape between the region R2 and the region R3. According to FIG. 7C, the buses 242 are stitched together in the form of an “X” between the region R3 and the region R4. Selection, alignment, and calibration of system hardware minimizes the size of the stitching form "X". In addition to the "X" form, the stitching form can be used as long as the alignment error of the pattern between adjacent areas can be sufficiently solved. According to another embodiment, if the pattern lines adjacent to each other are aligned within an error of +/− 10 μm, the stitching may not be necessary since the metallization may tolerate this small misalignment error. .

Referring again to FIGS. 7A-7C, one possible implementation of the stitching method is to perform the stitching of the bus 242 rather than the finger 241 stitching in the overlap region. This is because finger wire 241 already has a continuous electrical path to bus 242. If necessary, two or more bus bars 242 may be formed on the wafer 211.

8A through 8B are exemplary views illustrating a method of processing a wafer through laser scanning according to another possible embodiment of the present invention. According to the method illustrated in FIGS. 8A-8B, the wafer is moved at a substantially constant speed and not stationary within the laser processing time. In this case, the laser beam 233 can be controlled along the scan paths 240A, 240B, 240C, and 240D in a "bow-tie" pattern to repeatedly form a straight pattern on the wafer 211. have. When controlling the laser beam along path 240A and path 240C, a linear pattern is formed on the wafer 211, and the laser beam is also the starting position of the next line along path 240B and path 240D. Will return to. In addition to the linear scan movement along the path 240A or 240C, the laser beam 233 is controlled to advance slightly forward to follow the wafer speed to form a straight line on the wafer 211. The laser mask 210 can be used to prevent the laser beam from being heated on the wafer as it moves along its pivot paths 240B and 240D. When forming a straight line on the wafer 211 by controlling the laser beam with a “butterfly tie” scan pattern, the scan range in the wafer travel direction is limited to about a pitch of lines, which is limited. It is advantageous for systems with an "optimal spot" area.

In addition, the method illustrated in FIGS. 8A-8B is not only used to form a linear pattern. For example, a matrix of dots may be formed by the mask by using a mask that may block the laser beam at a predetermined position or pass the laser beam to write a pattern on the wafer. .

In addition, the method illustrated in FIGS. 8A-8B can be combined with the method illustrated in FIGS. 6A-6D and 6E to process a wafer. For example, the wafer is partitioned into a plurality of regions having substantially the same size, and each region can be processed through the method illustrated in FIGS. 8A-8B.

The foregoing has described a method and system for a photovoltaic device that is manufactured at high yields used in production in various various manners. Such methods and systems can be used not only to form front metal contacts on wafers, but also to form back metal contacts.

Although the present invention has been described through the above description, implementation manners, or examples, these examples do not limit the scope of the present invention in any form.

Claims (46)

In the photovoltaic device manufacturing system including a semiconductor wafer,
A laser device arranged to generate a laser beam; And
And a laser scanning device arranged to scan the laser beam on the wafer to locally heat the surface of the wafer. The method of claim 1,
The wafer has a substrate and a dielectric layer formed on the substrate,
The laser scanning device is further configured to heat the surface of the wafer to define an opening through the dielectric layer and to melt the surface of the substrate located below the dielectric layer. The method of claim 2,
The photovoltaic device further includes a dopant raw material layer formed on the surface of the dielectric layer,
The laser scanning device is arranged to heat a surface of the wafer such that a dopant contained in the dopant raw material layer is diffused through the opening into the molten substrate to further form a highly doped region in the substrate. Manufacturing system. The laser scanning device of any one of claims 1 to 3, wherein
A beam splitting module arranged to split the laser beam into at least two sub-beams having equal laser power;
At least two scanners for controlling the sub-beams to be scanned along a predetermined scan path defined on the wafer; And
And at least two lenses arranged such that the controlled sub-beams are focused at a focal position coinciding with the predetermined scan path. The method of claim 4, wherein
And the scanners are arranged to control one subbeam each. The method of claim 4, wherein
And said lenses are each arranged to focus one sub-beam. The method of claim 1,
And a laser mask disposed to prevent scanning of the area where the laser beam does not need to be heated on the wafer. The method of claim 1,
The laser device is a quasi-continuous wave laser device or a continuous wave laser device manufacturing system of a photovoltaic device. The method of claim 1,
The laser device is a quasi-continuous wave laser device having a pulse repetition rate of 1MHz or more. The method of claim 1,
The laser device is a picosecond laser device manufacturing system for a photovoltaic device. The method of claim 1,
And a wavelength of the laser device is about 532 nm or less. The method of claim 1,
And a beam quality factor of the laser beam is 1.3 or less. The method of claim 1,
And a profile of the laser beam generated from the laser device is TEM00 mode. The method of claim 1,
The profile of the laser beam generated from the laser device is in the TEM00 mode, the spot of the laser beam focused on the wafer surface is 10㎛ to 50㎛ size of the manufacturing system of the photovoltaic device. The method of claim 1,
And a scanning speed of the laser beam is between 2000 mm / s and 3000 mm / s. The method of claim 1,
The average laser power density of the laser beam is 2MW / cm ² A system for manufacturing a photovoltaic device of between 20 MW / cm ² . The method of claim 4, wherein
The intensity of each sub-beam focused on the wafer surface is maintained to heat the wafer surface to a temperature above the melting threshold of the wafer material and below the vaporization threshold of the wafer material. The method of claim 17,
The focal length of the lens is short enough to maintain the intensity of the sub-beams at such an intensity that the wafer surface is heated to a temperature above the melting threshold of the wafer material by the intensity of each sub-beam focused on the wafer surface. System for manufacturing photovoltaic devices. The method of claim 18,
The focal length of the lens is 160mm to 300mm manufacturing system of a photovoltaic device. The method of claim 18,
The focal length of the lens is 250mm photovoltaic device manufacturing system. The method of claim 4, wherein
The wafer is partitioned into at least two regions having the same size,
And the laser scanning device is arranged to scan the regions respectively through the sub-beams. The method of claim 21,
And the wafer is divided into four regions having the same size. The method of claim 21,
And the wafer is successively scanned one area by one sub-beam. The method of claim 21,
The areas of the same wafer are each scanned by a different laser beam. The method of claim 21,
And the laser scanning device is arranged to control the sub-beams to stitch to unaligned scan lines between adjacent areas on the same scan path of the same wafer. The method of claim 25,
And the scanning lines are stitched to each other in an "X" shape in an overlapping region between the adjacent regions. The method of claim 1,
And the wafer stops when the wafer is scanned by the laser beam. The method of claim 1,
And the wafer moves along one direction at a constant speed when the wafer is scanned by the laser beam. The method of claim 28,
The laser scanning device is configured to control the laser beam along a scan path of a bow tie pattern to form a straight pattern on the wafer. The method of claim 4, wherein
And a workbench arranged to load the wafer. The method of claim 30,
The work table is a rotary work table including a plurality of positions surrounding and around the central axis line of the work table,
Each of the positions is arranged to load a wafer,
And said working platform is rotated to move respective corresponding wafers from one position to the next. 32. The method of claim 31,
Each wafer is partitioned into at least two regions having the same size,
The quantity of each region on the wafer is equal to the quantity of the sub-beams,
Wherein each area on the wafer is scanned by a corresponding sub-beam. 33. The method of claim 32,
Each wafer is loaded at a start position and unloaded at an end position, and when the wafer is unloaded, all regions on the wafer are already scanned by the sub-beams. The method of claim 4, wherein
And a debris removal structure arranged to keep the system free of contamination of contaminants. 1. A method of manufacturing a photovoltaic device comprising a semiconductor wafer having a semiconductor substrate, a radiation layer formed on a surface of the semiconductor substrate, and a dielectric layer covering the surface of the radiation layer.
Forming a dopant raw material layer on a surface of the dielectric layer;
Locally heating the surface of the wafer through a laser beam to define a plurality of openings penetrating the dielectric layer, and melting the surface of the substrate located below the dielectric layer, so that the dopant raw material contained in the dopant raw material layer is Diffusing through the openings into the molten substrate to form a heavily doped region; And
And depositing a conductor in said heavily doped region. 36. The method of claim 35,
And after the step of locally heating the surface of the wafer via a laser beam, removing the dopant raw material layer. 36. The method of claim 35,
And the dielectric layer is arranged to be an anti-reflection film. 36. The method of claim 35,
Locally heating the surface of the wafer via a laser beam,
Maintaining the intensity of the laser beam to heat the wafer surface to a temperature above the melting threshold of the wafer material and below the vaporization threshold of the wafer material. 36. The method of claim 35,
And a surface doping concentration of the heavily doped region is 10 ¹⁹ cm ⁻³ or more. 36. The method of claim 35,
The profile of the laser beam is a TEM00 mode of manufacturing a photovoltaic device. In the method of processing a wafer through laser scanning,
Partitioning the wafer into at least two regions having the same size; And
Scanning each of the regions through one or a plurality of laser beams. The method of claim 41, wherein
And the wafer is continuously scanned one area by one laser beam. The method of claim 41, wherein
Wherein each said area of one wafer is scanned by a corresponding laser beam. The method of claim 41, wherein
Stitching against unaligned scan patterns on the same scan path of the adjacent regions in overlapping regions between adjacent regions. The method of claim 44,
The pattern is stitched with each other in an "X" shape in an overlapping region between the adjacent regions. In the method of processing a wafer through laser scanning,
Moving the wafer along one direction at a constant speed; And
Controlling a laser beam in the form of a bow tie along a pattern scan path to form a straight pattern on the wafer,
And a scanning range of the laser beam in the wafer moving direction is limited to a pitch of a scan path.

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