Transport and / or gripping device for semiconductor wafer solar cells or for semiconductor wafer solar cell precursors

Abstract

comprising a device for transporting and / or gripping semiconductor wafers: a wafer fixing device (1) with a plurality of adjacently arranged negative pressure areas (2, 20, 200), each having a gas inlet channel (10) for supplying a gas flow and a gas outlet structure (11) for discharging the gas flow, wherein the wafer fixing device (1) with the gas inflow channels (10) and the gas outflow structures (11) is designed such that the low-pressure areas (2, 20, 200) provide a holding force for a semiconductor wafer according to the Bernoulli principle, and wherein the wafer fixing device (1) has a plurality of planar wafer support areas (3, 30, 300, 3000) adjacent to the low-pressure areas (2, 20, 200), which are arranged such that the wafer support areas (3, 30, 300, 3000) lie in a common wafer plane (E) and the wafer support areas (3,30,300,3000) are designed in such a way that they realize the deflection of at least a portion of the gas flow from the gas inlet channels (10) into the gas outflow structures (11), wherein at least one of the gas outflow structures (11) has an outflow section (110) which extends away from the wafer plane (E) when viewed from the low-pressure areas (2, 20, 200) and wherein an L-shaped outflow element (4) limiting the outflow section (110) forms a wafer support area (3,30,300,3000) at one end.

Description

[0001] The invention relates to a device for transporting and / or gripping semiconductor wafer solar cells or precursors of semiconductor wafer solar cells. These solar cells and their precursors are collectively referred to as wafers below.

[0002] The starting material for the production of crystalline solar cells is semiconductor wafers. These are flat discs of a semiconductor material, such as silicon. The base area of ​​the wafers can be square, square with beveled corners (pseudosquare), or round. Currently, their diameter or edge length is typically between 50 and 210 mm, and their thickness between 100 and 300 µm.

[0003] During the production process of a wafer solar cell, the semiconductor material's solid-state physical properties are influenced, for example, by diffusion, and / or a multitude of layers are deposited on the wafer, which then form the solar cell structure. These layers are significantly thinner than the wafer thickness.

[0004] During the manufacturing process, it is often necessary to grip and transport individual wafers. Due to their material properties and their thin, yet large surface area, wafers are highly susceptible to breakage, especially under bending loads. Therefore, special systems must be used for gripping and transporting them, which place as little stress on the wafer as possible. In contrast, the gripping and transport steps must be carried out as quickly as possible to ensure short cycle times and thus cost-effective production in in-line production.

[0005] A well-known method for reliably gripping and transporting wafers is systems with vacuum suction cups. These systems hold the wafers at a few discrete suction points, thus applying local stress. Another disadvantage of these systems is that they are susceptible to clogging, for example, due to dust or splinters from broken wafers. If one or more suction cups become clogged, the suction cups do not contact the wafer surface evenly, thus making damage-free gripping and transport impossible. Therefore, these systems are comparatively maintenance-intensive.

[0006] WO 2011 / 009446 A2 describes a vacuum suction device in which negative pressure areas are created by sucking out air. The wafers do not rest on the suction device, but are lifted without contact to prevent damage to the wafer by the suction device.

[0007] Another well-known option is gripping and transport systems that operate according to the Bernoulli principle. These have a small cavity on the underside of a wafer fixation device. Air is blown into the upper side of the cavity, opposite the object to be gripped, so that the air flows out of the cavity's outer walls. The escaping air also carries molecules from the air cushion within the cavity, creating a negative pressure relative to the surrounding space. This negative pressure area can be used, for example, to lift a wafer and even move it in a contactless manner.

[0008] A gripper that provides contactless transport of a wafer is described, for example, in JP 2009-028 862 A. The gripper has Bernoulli devices, each with an opening. Air is blown into the openings, which flows out of each Bernoulli device. A gap remains between the Bernoulli devices and the wafer so that the incoming gas can flow out essentially parallel to the wafer. The gripper is therefore suitable for contactless, i.e., floating, wafer transport.

[0009] Furthermore, JP H06-40 560 A describes a holding device comprising a base body, an operating surface, a chamber, a fluid inlet opening, and a fluid suction opening for holding a plate-shaped body. The chamber may also be a circular groove, with partition walls and a pocket provided.

[0010] JP 2002-280439 A describes a gripping and / or transport device for a plate-shaped body such as a wafer. It comprises a substrate with a chamber, a holding surface, a nozzle, and a cover. The device operates according to the Bernoulli principle. A high-pressure fluid flows through the nozzle formed on a side surface of a cylinder, and a fluid detector may be provided.

[0011] A disadvantage of these Bernoulli systems is the fact that, given the fragile nature of the wafers, they can only be manufactured up to a certain size. If the systems were simply scaled up, the cavity on the underside of the gripper would also become increasingly larger. Since spatial differences in the vacuum level become increasingly greater in larger systems, this inevitably leads to excessive bending stress on the wafer.

[0012] This makes it impossible to lift and move larger wafers without risking damage. If a smaller system only grips them in the center, vibrations and bending stresses caused by air resistance during transport can lead to wafer breakage in the area of ​​the freely suspended wafer edges, especially the corners.

[0013] This technical disadvantage cannot be circumvented by placing several vacuum regions next to one another. Such an arrangement is described, for example, in German patent application DE 10 2008 023 907 A1. The wafer fixing device described therein features a plurality of adjacently arranged vacuum regions, each having a gas inflow channel and a gas outflow structure in the form of a gas outflow channel. As already described, the wafer fixing device with the gas inflow channels and the gas outflow channels is designed such that the vacuum regions provide a holding force for a semiconductor wafer according to the Bernoulli principle. The wafer fixing device has, adjacent to the vacuum regions, a plurality of planar wafer support regions arranged on the wafer fixing device such that the wafer support regions lie in a common wafer plane.

[0014] The disadvantage here is that the airflows from the individual negative pressure zones influence each other. This makes the overall airflow system unstable, resulting in excessive local fluctuations in the holding force.

[0015] The object of the invention is therefore to provide a device which avoids the disadvantages of the known systems and enables a safe transport, in particular a safe and gentle gripping, of wafers in the form of wafer solar cells and their precursors.

[0016] This object is achieved by a device having the features of claim 1.

[0017] According to the invention, at least one of the gas outflow structures has an outflow section which extends away from the wafer plane, starting from the negative pressure regions.

[0018] The feature relating to the "extending away" for the outflow section particularly encompasses the configurations in which the outflow section of the gas outflow structure extends, for example, as a straight or curved channel-like structure at an angle greater than 10 degrees, preferably greater than 40 degrees, and particularly preferably greater than 80 degrees, away from the wafer plane. As a special case, this encompasses the configuration in which the outflow section extends perpendicularly away from the wafer plane. This geometry of the gas outflow structure is fundamentally different from the prior art. There, the gas outflow structure typically has an outflow section that extends parallel to the wafer plane and to the edge of the device. The geometry claimed here enables individually controllable Bernoulli vacuum regions to be positioned on defined sections of the entire gripping surface of the device.The gas outflow structures of the individual vacuum zones therefore do not interfere with each other in terms of their position on the gripping surface. This results in a greater degree of freedom regarding the spatial design of the vacuum zones on the gripping surface, without the outflowing gas flows influencing each other fluidically to such an extent that the desired holding forces of the vacuum zones fluctuate excessively.

[0019] Preferably, the gas outflow structures of at least two adjacent vacuum regions are fluidically coupled. This embodiment provides that the gas outflow structures of at least two adjacent vacuum regions are fluidically coupled. This means that at least a portion of the outflowing gas from a first-order vacuum region flows into an adjacent second-order vacuum region. The second-order vacuum region either additionally has its own gas inflow channel and / or the gas outflow structure of the first-order vacuum region merges into the gas inflow channel of the second-order vacuum region.

[0020] This embodiment uses the outflowing gas from one vacuum region as the inflowing gas for adjacent higher-order vacuum regions. This way, either no additional gas flow, or at least significantly less additional gas flow, needs to be supplied to the adjacent higher-order vacuum regions via dedicated gas inflow channels.

[0021] A preferred embodiment provides that the gas outflow structures of at least two adjacent vacuum regions merge into one another, oriented parallel to the wafer plane. The gas supply via the gas inflow channels typically occurs transversely to the wafer plane.

[0022] A particularly simple embodiment provides that the gas outflow structures of all adjacent negative pressure areas merge into one another, oriented parallel to the wafer plane.

[0023] Preferably, the device, viewed from above onto the wafer plane, has a central vacuum region arranged on the wafer fixing device in the region of the center of the wafer fixing device, which is surrounded by at least one first-order wafer support region. The term "surrounded" refers not only to a support region that extends continuously around the central vacuum region, but also to one with interruptions along the circumference of the support region.

[0024] In a preferred embodiment, the first-order wafer support region(s) are enclosed by at least one second-order wafer support region, with at least one second-order vacuum region being formed between the first-order wafer support region(s) and the second-order wafer support region(s). The distance between the support regions is dimensioned such that the required holding force does not cause such deformation of the wafer in the vacuum region that mechanical damage to the wafer occurs.

[0025] In order to be able to fix wafers with edge lengths or diameters greater than 10 cm without the risk of damage due to the holding force, it is advantageous that the second-order wafer support area(s) is / are enclosed by at least one third-order wafer support area, wherein at least one third-order vacuum area is formed between the second-order wafer support area(s) and the third-order wafer support area(s).

[0026] Preferably, a plurality of gas outflow structures of adjacent vacuum regions extend parallel to the wafer plane, merging into one another, with several of the wafer support regions being configured as concentrically arranged circular rings when viewed from the wafer plane. The openings of the concentrically arranged circular rings represent pressure openings to the various vacuum regions.

[0027] The wafer support areas are designed in such a way that they realize the deflection of at least a portion of the gas flow from the gas inflow channels into the gas outflow structures.

[0028] Furthermore, it is provided that an outflow component defining the outflow section forms a wafer support area at one end. This allows the number of required components to be reduced.

[0029] The concentrically arranged circular rings advantageously provide a plurality of wafer support areas and a plurality of pressure openings between the gas inflow channel and an adjacent outflow section of a gas outflow structure. The number and dimensions of the support areas and pressure openings, in turn, take into account the mechanical sensitivity under the required contact pressure conditions.

[0030] When viewed from above onto the wafer plane, the wafer support areas and / or the vacuum areas are preferably configured in a circular, elliptical, or pseudo-square geometry. The geometry typically depends on the geometry of the wafers to be fixed.

[0031] An advantageous embodiment of the device is characterized in that the wafer support areas, viewed from the center of the wafer plane outwards, have an extension in the range of 5 to 30 mm, preferably 15 to 25 mm, particularly preferably 20 mm and / or the pressure openings, viewed from the center of the wafer plane outwards, have an extension in the range of 5 to 30 mm, preferably 8 to 20 mm, particularly preferably 10 mm.

[0032] Further properties and advantages of the device are explained in connection with the description of some preferred embodiments.

[0033] They show: Fig. 1: a plan view of the wafer plane E on the underside of a first embodiment of the device; Fig. 2: a sectional view through the device according to Fig. 1 along the dotted line II-II; Fig. 3: a sectional view of a second embodiment of the device similar to the view according to Fig. 2 and Fig. 4: a sectional view of a non-inventive embodiment of the device similar to the view according to Fig. 2.

[0034] Fig. 1 shows a plan view of the underside of a first embodiment of the device for transporting and / or gripping semiconductor wafers. The device includes a radially symmetrical wafer fixing device 1. A first-order circular wafer support region 30 is arranged concentrically around a circular central wafer support region 3, spaced apart by a circular central vacuum region 2. This first-order wafer support region 30 is enclosed by a concentrically arranged, first-order circular vacuum region 20. This first-order wafer support region is surrounded by a concentrically arranged, second-order circular wafer support region 300, which in turn is concentrically enclosed by a second-order circular vacuum region 200. The device structure terminates at the outside with a concentrically arranged, third-order circular wafer support region 3000.The circular and annular wafer support areas 3, 30, 300, and 3000 together span a wafer plane E. The goal is for a semiconductor wafer that is sucked onto the device by the vacuum areas 2, 20, and 200 to experience only minimal mechanical deflection. This requires, firstly, that the wafer support areas 3, 30, 300, and 3000 describe the wafer plane E with an accuracy of significantly less than 100 µm. Furthermore, the spacing of the radial widths of the vacuum areas must be selected to be smaller, the thinner the semiconductor wafer to be sucked onto. Otherwise, excessive deflection of the semiconductor wafer between adjacent wafer support areas will occur, which in extreme cases can lead to breakage.

[0035] The Fig. 1 and Fig. The embodiment shown in Figure 2 is radially symmetrical and thus has the advantage of being easily manufactured as a turned part with the required precision. However, a variety of other geometries are conceivable for the design and arrangement of the vacuum areas and the wafer support areas. These can, for example, also be arranged elliptically, squarely, or pseudo-squarely.

[0036] Fig. 2 shows a sectional view through the first embodiment of the device according to Fig. 1 along the dotted line II-II.

[0037] Above the central wafer support area 3 is the gas inflow channel 10 of the central vacuum region 2. This vacuum region 2 has a pressure opening 5, which is bordered by the central wafer support area 3 and the surrounding first-order wafer support areas 30. The first-order 20 and second-order 200 vacuum regions are each implemented using L-shaped outflow components 4. The short leg of the L-shape, with its downward-facing surface, forms the first-order 30, second-order 300, and third-order 3000 wafer support areas. At the same time, the long leg of the L-shape serves as a boundary of the gas inflow channel 10 for each of the higher-order vacuum regions 20, 200. The inner side of the L-shaped leg of the outflow component 4 deflects the gas flow entering through the gas inflow channel 10.The next L-shaped outflow component 4, arranged radially outwardly adjacent, forms with a long leg the boundary for the channel-shaped outflow section 110, which in this embodiment extends substantially perpendicular to the wafer plane E. It would also be conceivable for the outflow section 110 to extend at an obtuse angle with respect to the wafer plane E. Because the outflow section 110 extends away from the wafer plane E, it is possible to arrange independently controllable vacuum regions 2, 20, 200 with respect to the wafer plane E. This makes it possible to realize a variety of geometries that allow optimized fixing of the mechanically extremely fragile semiconductor wafers.

[0038] Fig. 3 shows a sectional view of a second embodiment of the device similar to the view according to Fig. 2 in a sectional view not to scale. Functionally identical components are provided with the same reference numerals. To avoid repetition, reference is also made to the preceding explanations. Unlike in the Fig. In the variant shown in Figure 2, a plurality of wafer support areas 3,30 are assigned to each of the vacuum areas 2,20.

[0039] Fig. 4 shows a sectional view of a non-inventive embodiment of the device similar to the view according to Fig.2 in a sectional view not to scale. Functionally identical components are provided with the same reference numerals. In this respect, reference is also made to the preceding explanations to avoid repetition. This non-inventive embodiment shows a second variant of the device. The central vacuum region 2 has a gas outflow structure 11 that runs essentially parallel to the wafer plane E defined by the wafer support regions 3, 30. The gas flow supplied through the gas inflow channel 10 of the central vacuum region 2 is diverted outwards between the wafer support regions 3, 30 and the outflow components 4, parallel to the wafer plane E. In the radial direction, the diverted gas flow is amplified by a gas supply from the gas inflow channels 10 of the higher-order vacuum regions 2, 20.Unlike the previous embodiments, the different negative pressure areas 2, 20 merge into one another and are not structurally clearly separated from one another. List of reference symbols: 1 wafer fixing device 2 central negative pressure area 20 First-order negative pressure range 200 Second order vacuum range 10 Gas inlet channel 11 Gas outflow structure 110 outflow section 3 central wafer support area 30 first-order wafer support area 300 second-order wafer support area 3000 third-order wafer support area 4 Outflow component 5 pressure openings E wafer level W semiconductor wafer

Claims

[1] Device for transporting and / or gripping semiconductor wafers, comprising: a wafer fixing device (1) with a plurality of adjacently arranged negative pressure regions (2, 20, 200), each having a gas inflow channel (10) for supplying a gas flow and a gas outflow structure (11) for discharging the gas flow, wherein the wafer fixing device (1) with the gas inflow channels (10) and the gas outflow structures (11) is designed such that the vacuum regions (2, 20, 200) provide a holding force for a semiconductor wafer according to the Bernoulli principle, and wherein the wafer fixing device (1) has, adjacent to the vacuum regions (2, 20, 200), a plurality of planar wafer support regions (3, 30, 300, 3000), which are arranged such that the wafer support regions (3, 30, 300, 3000) lie in a common wafer plane (E) and the wafer support areas (3, 30, 300, 3000) are designed such that they realize the deflection of at least a portion of the gas flow from the gas inflow channels (10) into the gas outflow structures (11), wherein at least one of the gas outflow structures (11) has a outflow section (110) which extends away from the wafer plane (E) starting from the negative pressure regions (2, 20, 200) and wherein an L-shaped outflow component (4) delimiting the outflow section (110) forms a wafer support area (3,30,300,3000) at one end thereof. [2] Device according to claim 1, characterized by that the gas outflow structures (11) of at least two adjacent negative pressure regions (2,20,200) are fluidically coupled. [3] Device according to claim 2, characterized bythat the gas outflow structures (11) of at least two adjacent negative pressure regions (2,20,200) merge into one another oriented parallel to the wafer plane (E). [4] Device according to claim 3, characterized by that the gas outflow structures (11) of all adjacent negative pressure regions (2,20,200) merge into one another oriented parallel to the wafer plane (E). [5] Device according to claim 1, characterized by that, viewed in plan view of the wafer plane (E), a central vacuum region (2) arranged on the wafer fixing device (1) in the region of the center of the wafer fixing device (1) is surrounded by at least one first-order wafer support region (30). [6] Device according to one of the preceding claims, characterized bythat the first-order wafer support region(s) (30) are enclosed by at least one second-order wafer support region (300), wherein at least one first-order vacuum region (20) is formed between the first-order wafer support region(s) (30) and the second-order wafer support region(s) (300). [7] Device according to claim 6, characterized by that the second-order wafer support region(s) (300) is / are enclosed by at least one third-order wafer support region (3000), wherein at least one second-order vacuum region (200) is formed between the second-order wafer support region(s) (300) and the third-order wafer support region(s) (3000). [8] Device according to one of the preceding claims, characterized byin that a plurality of gas outflow structures (11) of adjacent negative pressure regions (2, 20, 200) extend parallel to the wafer plane (E) and merge into one another, wherein several of the wafer support regions (30, 300, 3000) are designed as concentrically arranged circular rings when viewed on the wafer plane (E). [9] Device according to one of the preceding claims, characterized by that a plurality of wafer support regions (3, 30) and a plurality of pressure openings (5) are arranged between the gas inflow channel (10) and an adjacent outflow section (110) of a gas outflow structure (11). [10] Device according to one of the preceding claims, characterized by that, viewed in plan view onto the wafer plane (E), the wafer support regions (3,30,300,3000) and / or the negative pressure regions (2,20,200) are formed in a circular, elliptical or pseudo-square geometry. [11] Device according to one of the preceding claims, characterized by that the wafer support areas (3,30,300,3000), starting from the area of ​​the center of the wafer plane (E), in which the central negative pressure area (2) is arranged, have an outward extension in the range of 5 to 30 mm, preferably of 10 to 25 mm and particularly preferably of 20 mm. [12] Device according to one of claims 9 to 11, characterized by that the pressure openings (5) have an outward extension in the range of 5 to 30 mm, preferably 8 to 15 mm and particularly preferably 10 mm, from the region of the center of the wafer plane (E), in which the central negative pressure region (2) is arranged.

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