A patterned laser doping method and device

Abstract

A patterned laser doping method and device, belonging to the photovoltaic field. The patterned laser doping method includes: grouping target patterns to form at least two types of patterns; wherein the grouping method includes recording at least patterns with the same doping duration as one type of pattern according to the doping duration of each pattern in the target pattern; corresponding to the at least two types of patterns, laser doping is performed on the silicon wafer independently by laser in at least two processes. The doping method can shorten the production cycle of the selective emitter.

Description

Technical Field

[0001] The present application relates to the photovoltaic field, and in particular, to a patterned laser doping method and device. Background Art

[0002] In the production process of monocrystalline PERC cells, SE (Selective Emitter) plays a vital role as a low-cost and key efficiency-improving process.

[0003] The main feature of SE cells is high-concentration phosphorus doping in the metallized area and low-concentration phosphorus doping in the illuminated area.

[0004] The main implementation method of SE is to use the PSG layer formed after silicon wafer diffusion as an impurity source for doping, and according to the metallization pattern, SE laser driving is used to achieve local re-diffusion.

[0005] However, the current technology development direction is high square resistance dense grid lines. The more grid lines there are, the longer the marking time of the SE process. Therefore, it is urgent to speed up the SE process. Summary of the invention

[0006] The present application provides a patterned laser doping method and device, which can partially or completely improve or even solve the problem of low Se process speed in the related art.

[0007] This application is implemented as follows:

[0008] In a first aspect, an example of the present application provides a patterned laser doping method, comprising: grouping target graphics to form at least two types of graphics; wherein the grouping method comprises, based on the doping time of each graphics in the target graphics, recording at least graphics with the same doping time as one type of graphics; corresponding to the at least two types of graphics, laser doping the silicon wafer independently by laser in at least two processes.

[0009] Since different graphics have different doping times, the process needs to be adjusted accordingly when laser doping different graphics. In addition, the various types of graphics in the target graphics are dispersedly distributed. Therefore, when laser doping is performed according to the target graphics, it is necessary to frequently adjust between different process parameters, and these process adjustment devices cannot perform effective laser doping operations, resulting in some "invalid" time and operations in the entire laser doping process. Therefore, since laser doping is difficult to perform "continuously", the laser doping cycle for completing a complete target graphic is longer.

[0010] The present application scheme, by classifying various graphics in the target graphics according to the doping time (the doping time of graphics of the same type is close or roughly the same or equal; the doping time of graphics of different types is greatly different). After the target graphics are classified, according to the classified graphics, when laser doping, one type of graphics is completed before another type of graphics is operated, thereby effectively reducing the adjustment time between the laser doping processes of different types of graphics, thereby substantially shortening the cycle of laser doping according to the entire target graphics.

[0011] In short, since the laser doping cycle of the exemplary solution of the present application is shorter, the exemplary solution of the present application can achieve laser doping of more target patterns within the same time, thereby achieving a higher laser doping speed.

[0012] According to some examples of the present application, the target graphics include any one or more of a mark point, a secondary grid line, an anti-break grid, and a segmented main grid;

[0013] Optionally, the mark point includes any one or more of a circular mark, a solid mark and a cross mark.

[0014] According to some examples of the present application, the target graphics include mark points and secondary grid lines, and the at least two types of graphics include a first type of graphics composed of mark points and a second type of graphics composed of secondary grid lines.

[0015] According to some examples of the present application, corresponding to at least two types of patterns, a method for laser doping a silicon wafer by laser in at least two processes independently includes:

[0016] First, the silicon wafer is doped by laser according to the first type of pattern; then, the silicon wafer is doped by laser according to the second type of pattern.

[0017] According to some examples of the present application, the target graphics include mark points, secondary grid lines and anti-break grid lines, and at least two types of graphics include a third type of graphics consisting of mark points and anti-break grid lines, and a fourth type of graphics consisting of secondary grid lines;

[0018] Alternatively, the target graphics include mark points, secondary grid lines and anti-break grid lines, and at least two types of graphics include a fifth type of graphics composed of mark points and anti-break grid lines, a sixth type of graphics composed of anti-break grid lines, and a seventh type of graphics composed of secondary grid lines.

[0019] According to some examples of the present application, corresponding to at least two types of patterns, a method for laser doping a silicon wafer by laser in at least two processes independently includes:

[0020] First, the silicon wafer is doped by laser according to the third type of pattern; then, the silicon wafer is doped by laser according to the fourth type of pattern.

[0021] According to some examples of the present application, corresponding to at least two types of patterns, a method for laser doping a silicon wafer by laser in at least two processes independently includes:

[0022] First, the silicon wafer is doped by laser according to the fifth type of pattern; then, the silicon wafer is doped by laser according to the sixth type of pattern; and then, the silicon wafer is doped by laser according to the seventh type of pattern.

[0023] According to some examples of the present application, the patterned laser doping method further includes:

[0024] Positioning the silicon wafer before laser doping the silicon wafer by laser in at least two processes respectively and independently in correspondence with at least two types of patterns;

[0025] Optionally, the positioning method includes taking a photo of the silicon wafer and positioning the silicon wafer according to the photo result;

[0026] Optionally, the photo taking operation is completed by taking photos with one camera at a time.

[0027] In a second aspect, an example of the present application provides a patterned laser doping device, which is used to implement the above-mentioned patterned laser doping method.

[0028] The device includes:

[0029] A rotatable stage having a photographing station adjustable by rotation and at least two laser operating stations;

[0030] The camera is opposite and away from the stage;

[0031] at least two laser manipulators capable of pre-positioning based on the stage, disposed opposite and away from the stage;

[0032] The at least two laser operators are independently configured and correspond to at least two laser operating stations respectively.

[0033] In a third aspect, an example of the present application provides a patterned laser doping device, which is used to implement the patterned laser doping method described above.

[0034] The device includes:

[0035] A rotatable stage having a photographing station adjustable by rotation and at least two laser operating stations;

[0036] The camera is opposite and away from the stage;

[0037] A laser manipulator capable of pre-positioning based on the stage, opposite to and away from the stage;

[0038] The laser operator is arranged in a rotatable manner and can be operated corresponding to at least two laser operating stations by rotating.

[0039] In the above implementation process, the patterned laser doping method provided in the embodiment of the present application uses laser doping to produce a selective emitter, and improves the production efficiency of the entire selective emitter by segmenting / grouping the pattern of the selective emitter, effectively shortening the production cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0041] Figure 1 It is a schematic diagram of the process of the patterned laser doping method in the example of this application. DETAILED DESCRIPTION

[0042] In order to collect current, in the solar cell structure, electrodes need to be made on the surface of the cell / silicon wafer, and based on the need for light, the electrodes are usually made into grid electrodes. Further, the grid electrodes can be adjusted in various ways according to needs, such as arrangement, grid width, number and shape, etc.

[0043] Furthermore, as an improvement method different from the counter electrode, the selective emitter solar cell performs high-concentration doping at the contact point between the (metal) gate line and the silicon wafer and the area near the gate line, and performs low-concentration doping in the area outside the electrode. This method can reduce the contact resistance between the silicon wafer and the electrode, and reduce the carrier recombination on the surface of the silicon wafer, thereby increasing the minority carrier lifetime and further improving the conversion efficiency of the battery.

[0044] In PERC cells, selective emitter technology is widely used, and the combination of the two has a significant effect on improving the conversion efficiency of the cell, for example, a 20% improvement in conversion efficiency compared to conventional traditional cells.

[0045] Usually, selective emitters are made by laser doping. That is, the phosphorus-silicate glass layer produced during the diffusion of silicon wafers is used as the doping source, and laser scanning is performed on the selected area on the surface of the silicon wafer to form a heavily doped area; while the area not scanned by the laser constitutes a lightly doped area.

[0046] Therefore, it is very important to perform laser doping on the surface of silicon wafers efficiently and with high quality.

[0047] The present application is a new method for manufacturing a selective emitter developed to address the situation where the current manufacturing speed of a selective emitter is difficult to meet the technical requirements of high square resistance and dense grid lines. Moreover, based on the general description in the industry, the manufacturing of the selective emitter can be simply described as marking. At the same time, considering that the marking process is achieved by laser scanning, it can also be called laser engraving.

[0048] In this application, the inventor proposes to optimize and improve the laser engraving / marking process. In the example, the inventor proposes to group the graphics that need to be laser engraved, and on the premise of grouping, perform corresponding laser engraving on the grouped graphics - referred to as segmented engraving. For example, when there are two types of graphics in the graphics, it can be divided into two laser engravings, one of which is used to make one type of graphics, and the other laser engraving is used to make the other type of graphics.

[0049] The grouping method includes recording at least the graphics with the same doping time as one type of graphics according to the doping time of each graphic in the target graphic. Since the doping time of the same type of graphics (same shape) is consistent (similar or roughly the same, or even the same; in comparison, the doping time of different types of graphics is generally relatively large), therefore, the above-mentioned classification of graphics according to doping time can also be classified by the shape of the graphics in some examples. Furthermore, in other examples, on the basis of the above classification, the classified graphics can be appropriately selected for re-combination and classification; for example, the mark points, anti-break grids and auxiliary grids mentioned later are divided into three types of graphics; further, the already classified mark points and anti-break grids can be merged into one category, and the auxiliary grids as another category. In other words, the graphics with significantly longer laser doping time in the target graphics are treated as an independent category, while other graphics with shorter but close laser doping time can be merged into another category.

[0050] By using such a segmented laser engraving scheme, the manufacturing cycle CT (Cycle Time) of the selective emitter of a silicon wafer can be shortened; in other words, the scheme of the example of the present application increases the marking speed.

[0051] The embodiments of the present application will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0052] The following is a detailed description of a patterned laser doping method and device according to an embodiment of the present application:

[0053] Previously, the inventors generally performed marking in the following manner in practice: a target pattern was imported into a computer, and a preheated laser used a laser with high energy density and a certain engraving speed to engrave the target pattern on the surface of a silicon wafer.

[0054] For example, the SE marking process is divided into: placing the film, taking pictures with a camera, laser engraving, and taking the film.

[0055] In the SE marking process, the most time-consuming step is the laser engraving process. However, laser engraving is limited by the corresponding laser pattern. In view of the problem encountered in the current marking process - long marking time - the inventor proposes to perform multiple laser engravings to solve the problem of long marking time.

[0056] Considering that the graphics engraved by laser can usually be composed of different types of shapes, for example, the basic components of laser graphics include mark points and auxiliary grid lines. In addition, some graphics may include segmented main grids or anti-break grids. Therefore, laser graphics can cover mark points, auxiliary grid lines, segmented main grids, anti-break grids, etc. Since the distribution and arrangement of these graphics on the surface of the silicon wafer are configured according to needs and designs, they are usually laid out in a dispersed manner. The current marking method usually marks from one side of the surface of the silicon wafer in sequence until it reaches the other side of the surface of the silicon wafer. Then, in the marking process, the laser needs to frequently mark different types of graphics, which significantly increases the marking time.

[0057] Through practice and analysis of the above-mentioned problems and reasons for the long marking time, the inventors proposed a solution for marking different types of graphics separately according to the characteristics of the laser graphics. For example, the above-mentioned laser graphics include mark points (for example, any one or more of a circular mark, a solid mark, and a cross mark), auxiliary grid lines, segmented main grids, and anti-break grids. Therefore, the laser graphics include four types of graphics. For example, the first type of graphics: mark points; the second type of graphics: auxiliary grid lines; the third type of graphics: segmented main grids; the fourth type of graphics: anti-break grids. Therefore, different from the currently generally used marking method described above—marking in sequence without distinguishing between graphics—in the example of this application, the inventors choose to mark any of the above-mentioned graphics; after one type of graphics is marked, another type of graphics is marked.

[0058] In short, the patterned laser doping method in the examples of the present application includes: grouping the target graphics to form at least two types of graphics. Then, corresponding to the at least two types of graphics, the silicon wafer is laser doped by laser in at least two processes respectively and independently. Because in general, the marking time of the secondary grid line, one of the components of the laser graphics, accounts for the largest proportion. Therefore, in some examples, the grouping method can be implemented in the following manner: taking the marking time of different types of graphics as a comparison benchmark, the secondary grid line with the longest marking time is grouped as a group, and the other graphics can be divided into one or two or more categories.

[0059] The target graphics are grouped to classify the graphics of the same type or category into one graphic or one category of graphics, so that the same category of graphics can be laser engraved during subsequent laser engraving; after the laser engraving of one category of graphics is completed, the next engraving can be performed.

[0060] For the target graphics having four types of graphics, four laser engravings can be selected. In other examples, the target graphics having four types of graphics can also be divided into three types of graphics or two types, etc. In other words, the present application does not specifically limit the classification method of the target graphics. The classification method can be, for example, the same type of graphics as one type of graphics, or two types of graphics as one type of graphics, or other methods. For example, mark points and anti-break fences can be one type of graphics or two types of graphics.

[0061] In addition, with respect to the classification method of the target graphics, the order of laser engraving of different types of graphics is arbitrarily selected, and the present application does not make specific limitations on this. For example, when the target graphics have a mark point and a sub-grid, the target graphics can be divided into two types of graphics. Under the premise of this grouping method, the mark point can be marked first, and then the sub-grid can be marked; or, in other examples, the sub-grid can be marked first, and then the mark point can be marked. When there are multiple laser engraving devices, different devices can also mark the above two types of graphics simultaneously and independently, provided that different devices work simultaneously without interfering with each other.

[0062] In addition, before laser engraving the surface of the silicon wafer, the silicon wafer can be photographed. By taking photos and analyzing the photographed images, the silicon wafer can be positioned according to the photographed results. The method of photographing and positioning can be implemented in a general operating method in the art, and this application will not describe it in detail.

[0063] The reason for taking pictures and aligning is that the placement of the silicon wafer may deviate, and positioning can ensure that the laser pattern is engraved in the center of the silicon wafer to the maximum extent. In some examples, the operation of taking pictures can be completed by one camera taking a picture at a time.

[0064] In order to facilitate those skilled in the art to implement the patterned laser doping method in the example of the present application, the inventors in the example also proposed a patterned laser doping device.

[0065] The device includes a stage, a camera, and a laser manipulator.

[0066] As the name implies, the stage is a structure used to place and fix the silicon wafer. The camera is used to take pictures of the silicon wafer in order to locate it. The laser manipulator is used to perform laser engraving / marking according to the target pattern.

[0067] In order to improve the utilization rate and working efficiency of the equipment, the stage can be configured as a rotatable structure, and thus has a photographing station that can be adjusted by rotation and at least two laser operating stations.

[0068] The stage can be realized by fixing a rotating structure (such as a motor) on a frame structure. For example, a frame is formed by welding metal angle steel. Then the motor is fixed on the frame, and the output shaft of the motor is arranged in the vertical direction. The output shaft of the motor is connected to a structure such as a storage plate with a groove for placing silicon wafers.

[0069] The camera can be selected from various commercially available devices used in this industry, which can be fixed near the stage by a mechanical arm. For example, the camera is fixed in a posture facing and away from the stage. In some examples, the stage can automatically compensate parameters according to the camera's photo results to ensure that the laser pattern is engraved in the center of the silicon wafer to the maximum extent.

[0070] The laser manipulator is opposite and away from the stage, and based on the accuracy of engraving, it can be pre-positioned based on the stage; for example, the laser manipulator can be a device based on the combination of industrial robot arm and pan-tilt stabilizer technology, and the laser manipulator is fixed accordingly. The laser manipulator is a device that emits laser as needed, which can be provided by commercially available equipment, and its structure is not described in detail in this application.

[0071] In different usage modes, the laser operator may have different configuration modes. For example, there may be multiple laser operators, exemplarily at least two. Each laser operator corresponds to a laser engraving station. That is, multiple (at least two) laser operators are independently configured and correspond to multiple (at least two) laser operation stations respectively. In other examples, the degree of freedom or flexibility of the laser operator can be increased, and the number of configurations of the laser operator can be reduced. Therefore, the laser operators in these examples can be arranged in a rotatable manner, and can be operated by rotating to correspond to at least two laser operation stations.

[0072] Based on such a patterned laser doping device, the following can be done: Figure 1Marking is performed in the manner shown.

[0073] The method of reducing CT value by segmented laser includes the following steps:

[0074] (1) The silicon wafers after diffusion in the flower basket are transported to the Figure 1 (a) The table where the films are placed.

[0075] (2) The silicon wafer at the placement position is rotated to (2) the camera photography position, and the silicon wafer to be laser engraved is positioned and photographed.

[0076] Generally, the position of the silicon wafer on the table is determined by X / Y and angle. It is usually determined that the X / Y deviation is within ±4 and the angle is within 2 to be qualified, otherwise the robot arm will discard the silicon wafer.

[0077] (3) After the silicon wafer passes the photo, it is rotated to the first laser engraving station (iii) for the first part of engraving.

[0078] The qualified photography means that the placement of the silicon wafer is within the specified range. And within the specified placement position, the laser can automatically make up for it during laser engraving, thereby avoiding possible abnormalities in the appearance of the silicon wafer after marking, to ensure mass production.

[0079] (4) The silicon wafer that has completed the first part of the engraving is rotated to (iv) the second laser engraving station to carry out the second part of the engraving.

[0080] It should be noted that, as mentioned above, after the target graphics are grouped, the graphics of different groups can be laser engraved in any order. Therefore, in this example, the first part of the graphics is engraved first, and then the second part is engraved. In some other examples, the second part of the graphics can be engraved first, and then the first part is engraved.

[0081] (5) After laser engraving, the silicon wafer rotates to the (5) wafer picking position and is transferred to the unloading basket, completing the entire SE process.

[0082] A patterned laser doping method and device of the present application are further described in detail below in conjunction with embodiments.

[0083] Example 1

[0084] Taking a pattern containing only MRAK dots and auxiliary grids as an example, the method of reducing the CT value by segmented laser includes the following steps:

[0085] (1) The silicon wafers diffused in the basket are transferred to the wafer placement table by a belt.

[0086] (2) The silicon wafer is rotated to the camera position to position and photograph the silicon wafer to be laser engraved.

[0087] (3) The qualified silicon wafer is rotated to Figure 1 Laser engraving 1, engrave the first part of the 4 circular MARKs.

[0088] (4) The silicon wafer that has completed the first part of the engraving is rotated to the laser engraving 2 position to carry out the second part of the sub-gate engraving.

[0089] (5) After laser engraving, the silicon wafer is rotated to the wafer taking position and transferred to the material unloading basket, completing the entire SE process.

[0090] The laser engraving time of this embodiment is reduced from 0.94 seconds to 0.84 seconds, a reduction of 10%.

[0091] Example 2

[0092] Taking the pattern containing MARK points, auxiliary grid and anti-break grid as an example, the method of reducing the CT value by segmented laser includes the following steps:

[0093] (1) The silicon wafers diffused in the basket are transferred to the wafer placement table by a belt.

[0094] (2) The silicon wafer is rotated to the camera position to position and photograph the silicon wafer to be laser engraved.

[0095] (3) The qualified silicon wafer is rotated to Figure 1 Laser engraving 1, engrave the first part of the 4 circular MARKs and anti-breakage fence.

[0096] (4) The silicon wafer that has completed the first part of the engraving is rotated to the laser engraving 2 position to carry out the second part of the sub-gate engraving.

[0097] (5) After laser engraving, the silicon wafer is rotated to the wafer taking position and transferred to the material unloading basket, completing the entire SE process.

[0098] The laser engraving time of this embodiment is reduced from 1.01 seconds to 0.80 seconds, a reduction of 21%.

[0099] It can be seen that the laser engraving methods of the above two examples can reduce the laser engraving time by about 10%-21%, thereby effectively solving the problem of excessive laser engraving time.

[0100] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A patterned laser doping method, characterized in that: include: The target graphics are grouped to form at least two types of graphics, wherein the grouping method includes recording at least graphics with the same doping duration as one type of graphics according to the doping duration of each graphic in the target graphics; Corresponding to the at least two types of patterns, the silicon wafer is laser doped independently by laser in at least two processes.

2. The patterned laser doping method according to claim 1, characterized in that: The target graphics include any one or more of mark points, auxiliary grid lines, anti-break grids and segmented main grids.

3. The patterned laser doping method according to claim 2, characterized in that: The mark point includes any one or more of a circular mark, a solid mark and a cross mark.

4. The patterned laser doping method according to claim 1, characterized in that: The target graphics include mark points and secondary raster lines, and the at least two types of graphics include a first type of graphics formed by the mark points and a second type of graphics formed by the secondary raster lines.

5. The patterned laser doping method according to claim 4, characterized in that: Corresponding to the at least two types of patterns, the method of laser doping a silicon wafer by laser independently in at least two processes includes: First, the silicon wafer is doped by laser according to the first type of pattern; and then the silicon wafer is doped by laser according to the second type of pattern.

6. The patterned laser doping method according to claim 1, characterized in that: The target graphics include mark points, auxiliary grid lines and anti-break grid lines, and the at least two types of graphics include a third type of graphics consisting of the mark points and the anti-break grid lines, and a fourth type of graphics consisting of the auxiliary grid lines; Alternatively, the target graphics include mark points, secondary grid lines and anti-break grid lines, and the at least two types of graphics include a fifth type of graphics composed of the mark points and anti-break grid lines, a sixth type of graphics composed of the anti-break grid lines, and a seventh type of graphics composed of the secondary grid lines.

7. The patterned laser doping method according to claim 6, characterized in that: Corresponding to the at least two types of patterns, the method of laser doping a silicon wafer by laser independently in at least two processes includes: First, the silicon wafer is doped by laser according to the third type of pattern; and then the silicon wafer is doped by laser according to the fourth type of pattern.

8. The patterned laser doping method according to claim 6, characterized in that: Corresponding to the at least two types of patterns, the method of laser doping a silicon wafer by laser independently in at least two processes includes: First, the silicon wafer is doped by laser according to the fifth type of pattern; then, the silicon wafer is doped by laser according to the sixth type of pattern; and then, the silicon wafer is doped by laser according to the seventh type of pattern.

9. The patterned laser doping method according to claim 1 or 5 or 7 or 8, characterized in that: The patterned laser doping method further comprises: In correspondence with the at least two types of patterns, the silicon wafer is positioned before the silicon wafer is independently doped with lasers in at least two processes.

10. The patterned laser doping method according to claim 9, characterized in that: The positioning method includes taking a photo of the silicon wafer and positioning the silicon wafer according to the photo result.

11. The patterned laser doping method according to claim 10, characterized in that: The photo taking operation is completed by taking a photo with one camera at a time.

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