Method and apparatus for singulating wafers

Abstract

The invention relates to a method for singulating a wafer (100) having a first face (100a) and a second face (100b) located opposite the first face (100a) wherein the method comprises the following steps: contacting the wafer (100) with a protection device (120) having one or more carrier structures (122) such that the first face (100a) of the wafer (100) is in contact with the plurality of carrier structures (122), the wafer (100) in contact with the protection device (120) is singulated into a plurality of chips (180a, 180b), and the chips (180a, 180b) are removed (440) from the wafer (100) in contact with the protection device (120). Moreover, the invention also relates to a protection device (120) having one or more carrying structures (122) for temporarily carrying a wafer (100), the protection device being configured to be used in the method according to the invention.

Description

Technical Field

[0001] The present invention relates to the field of producing semiconductor chips from wafers, in particular for micro-electromechanical devices, and to a method for singulating wafers and a protective device for temporarily supporting the wafers for use in the method. Background Art

[0002] Devices containing microelectromechanical systems (MEMS), such as microlens arrays or microlens actuators, are used today in a variety of devices, for example in smartphones, projectors, head-mounted displays, barcode readers, mask exposure units in semiconductor manufacturing, and microscopes. Corresponding microlens arrays are known, for example, from the documents DE 10 2013 208 446 A1, EP 0 877272 A1 and WO 2010 / 049076 A2. During the wafer-based production of individual microelectromechanical systems, it is necessary to ensure constant protection of the microelectromechanical structures of these systems in order to avoid unwanted damage. Particularly important steps here are, for example, soldering or sintering processes, in particular the singulation of the wafer into individual chips (dies), since these can easily cause damage and / or contamination to the microelectromechanical structures. For this reason, sensitive structures are usually temporarily protected by suitable protective structures, which, however, significantly reduces the fill factor of the end product, i.e. the produced chips. Summary of the invention

[0003] According to the present invention, a method for singulating a wafer and a protective device for temporarily supporting a wafer for use in the method according to the present invention are provided.

[0004] According to a first aspect of the invention, a method for singulating a semiconductor wafer (also referred to as wafer in the present context of the invention), in particular a silicon wafer, having a first face and a second face is provided, wherein the second face is located opposite to the first face. The first and second faces are therefore two different main faces of the wafer. In this case, the method comprises contacting the wafer with a protective device, for example, for positioning the wafer on the protective device, wherein the protective device has one or more supporting structures. In this case, the wafer is contacted with the protective device so that the first face of the wafer is in contact with the one or more supporting structures. In this case, for example, the protective device can be used to temporarily support the wafer or can be temporarily positioned thereon. Therefore, the wafer can generally be placed on the protective device or the protective device is positioned on the wafer.

[0005] Bonding of the wafer to the protective device may be performed, for example, by sintering or eutectic bonding, at the time of contact or thereafter, in order to avoid unwanted movements, for example displacements, of the wafer and the protective device relative to each other. Thus, handling of the wafer and the protective device is facilitated and thus a movement and / or rotation of the protective device in engagement with the wafer is possible. Alternatively, it is also possible to spread such bonding and, optionally, also to use fixing devices for temporarily fixing the contact between the protective device and the wafer. Spreading the bonding allows the protective device to be reused for other wafers, if appropriate, after cleaning.

[0006] After contacting the wafer with the protective device, optionally, once further steps for processing the wafer have been performed, such as etching of release structures for MEMS (micro-electromechanical systems) in so-called sacrificial areas (sacrificial layer etching) in the semiconductor layer of the wafer, and / or wafer bonding of a second wafer to a wafer, such as eutectic bonding, the wafer (when wafer bonding has been completed, together with the second wafer singulated, i.e. the entire coupled wafer) is singulated into a plurality of semiconductor chips (also referred to as chips in the context of the present invention for short). The sacrificial layer etching can be performed, for example, by chlorine trifluoride (ClF3), chlorine fluoride (ClF), chlorine pentafluoride (ClF5), bromine trifluoride (BrF3), bromine pentafluoride (BrF5), iodine pentafluoride (IF5), iodine heptafluoride (IF7), sulfur tetrafluoride (SF4), xenon difluoride (XeF2) or similar substances. These chips are then removed from the wafer, which is still in contact with the protective device. In this case, the steps of singulation and removal can be combined, ie, occur simultaneously. Thus, singulation of the wafer can occur before removing the chips from the wafer, but can also be performed together with removing the chips.

[0007] In this case, the protective device is used as part of the protection of the wafer during important steps, such as bonding, such as wafer bonding of another wafer to the wafer (such as eutectic bonding) or bonding of other chips to the wafer, in particular by soldering and / or sintering and / or eutectic bonding; wafer testing and / or singulation, whereby it is temporarily carried by the protective device. The wafer is preferably in contact with the protective device, for example, positioned relative thereto, such that the structures of the wafer to be protected do not come into contact with one or more supporting structures of the protective device. Furthermore, the wafer is preferably in contact with the protective device, such that the structures to be protected are protected by the protective device and, possibly, are available for subsequent processing steps.

[0008] After contacting the wafer with the protective device and before singulating the wafer, a gap structure is preferably formed, which surrounds each chip, partially perforates (penetrates) the wafer (does not form a closed shape such as a rectangle) and has a plurality of gaps in the wafer. The subsequent singulation is performed at least partially along these plurality of gaps. Singulation can be, for example, by breaking and / or cutting with a laser (laser cutting) and / or etching method. The chips to be removed from the wafer are partially separated from the rest of the wafer (the rest of the wafer) by the step of forming the gap structure. This gap structure is typically formed in such a way that a web (separating connection) connects each chip to the rest of the wafer. What is achieved by this is that the chip can be easily removed from the wafer later, for example when the chip is removed from the protective device. In this case, for example, the chip can be removed from the wafer by simply breaking the webs, so that chip removal and singulation can be performed simultaneously. By using appropriate methods for laser cutting, it is also possible to evaporate these webs. This has the advantage that the webs are completely moved out of the way without causing an uncontrolled breakage of the webs.

[0009] Alternatively or additionally, a trench structure surrounding each chip and having one or more trenches can also be formed on the first side and / or the second side of the wafer. With this trench structure, the wafer is thinned in a targeted manner, i.e. provided with one or more trenches. The wafer is then singulated at least partially along the one or more trenches. In the context of the present invention, on the surface of the wafer, a trench structure having one or more trenches means a structure consisting of one or more trenches in a wafer, so that the trench system is open to the surface. The trenches of the trench structure, in the case of singulation, usually surround the chip to be removed from the rest of the wafer. In the case of a trench structure, for example, there are also advantages in simplifying singulation by breaking the chip from the rest of the wafer. The trench structure surrounding each chip can also include non-interconnected trenches, i.e., can, for example, be composed of a plurality of trenches, which surround the chip and do not need to be interconnected. The entirety of these trenches is referred to as a trench structure in the context of the present invention.

[0010] Alternatively or additionally, a gap structure can be formed which surrounds the chips and has one or more gaps in the wafer. Here, singulation can be performed at least in part by forming the gap structure. If all chips on the wafer are surrounded by the gap structure, the wafer can be completely singulated by the gap structure. Separate singulation is not necessary. As in the case of the trench structure, the gap structure can also consist of non-interconnected cuts around the chips, for example; it is possible to configure the corresponding cuts in the form of gaps surrounding the chip. The entirety of these gaps is referred to as a gap structure in the context of the present invention. Locally penetrating gap structures are therefore gap structures, which do not form a closed shape. Singulating the wafer by forming a gap structure in the wafer is particularly advantageous because, in this case, the release of particles that could cause contamination of sensitive structures on the wafer can be completely avoided.

[0011] In the context of the present invention, a gap structure is understood to mean one or more cuts of the wafer which completely penetrate the wafer in a vertical direction. In contrast, a trench structure means one or more depressions which do not extend over the entire thickness of the wafer. Singulating a wafer along partially penetrating gap structures means singulation such that multiple cuts of the gap structure are utilized to detect chips from the rest of the wafer, which occurs by destroying, for example, breaking, connections still existing between the chip and the rest of the wafer (e.g. in the form of webs). The gaps of the gap structures and the trenches of the trench structures may differ from simple gaps and trenches which pass vertically through the wafer, i.e. rectangular cuts and depressions; for example, the use of undercuts may be conceivable. More specifically, the gaps and trenches may be made such that the retaining structures are at least partially shaped to continue to fix the chips in the wafer after their singulation, i.e. to limit the movement of the chips after singulation, e.g. in order to prevent the chips from accidentally falling off the wafer during movement of the wafer.

[0012] In a specific configuration of the method according to the invention, the formation of gaps and / or trenches and also of gap structures and / or partially perforated gap structures and / or trench structures is performed by an etching process. In this case, for example, deep reactive ion etching (DRIE) can be used as an etching method. Furthermore, the formation of the gap structure and / or trench structure can be performed before contacting the wafer with the protective device. Preferably, the formation of the gap structure and / or trench structure is performed after contacting the wafer with the protective device, and preferably also after the wafer may be bonded to the protective device, in order to utilize the protective function of the protective device that has been used in this method step. This etching process is preferably combined with an etching process for etching structures of the chip, such as sacrificial layer etching, so that a method step includes forming a gap structure and / or a partially perforated gap structure and / or trench structure, and performing sacrificial layer etching.

[0013] Singulation can finally be carried out, for example, using etching methods, laser cutting methods and / or breaking methods. A suitable etching method here is also deep reactive ion etching (DRIE), but also etching by xenon difluoride (XeF2).

[0014] The method according to the invention can be used particularly advantageously for the production of microelectromechanical systems. More specifically, this is the case if the wafer has an open structure, for microelectromechanical systems (MEMS structures). In this case, the wafer contacts and is preferably bonded to the protective device, so that the one or more supporting structures do not contact the open MEMS structure. If the open MEMS structure is open towards a first side of the wafer, further steps of processing the wafer in the present context can be carried out on the opposite second side of the wafer, such as welding, sintering, wafer bonding, bonding of other chips, wafer testing and / or final singulation of the wafer, without endangering the first side protected by the protective device during the steps. The method is useful and particularly advantageous if the open MEMS structure also comprises a MEMS structure for a microlens array, since this structure is particularly sensitive.

[0015] In a particularly preferred embodiment of the method according to the invention, the wafer has a holding structure and / or a holding structure is formed in the wafer after contacting the protective device and before singulating the wafer, wherein the holding structure is configured to limit possible movement of the chips in at least one direction after singulation. For example, the holding structure can prevent the chips from falling out of the wafer and / or falling off after singulation and, on the contrary, can hold the chips on the rest of the wafer and thus on the protective device. The holding structure can be represented, for example, by suitable cuts and / or recesses and undercuts in the wafer. The holding structure is advantageously arranged at the edge of the chip released for singulation and ensures that the interlocking of the chip with the rest of the wafer is already completed after singulation, which prevents free movement of the chip in a direction perpendicular to the first face of the wafer. This makes it possible to prevent the chips from falling off, for example, if the wafer is arranged horizontally on the protective device (i.e. perpendicular to the direction of gravity). It is also conceivable that the holding device is implemented as a gap structure, which is suitable for preventing the chips of the wafer from undesired movement in two directions perpendicular to the first side of the wafer after singulation.

[0016] The holding structure is particularly advantageous if the wafer is rotated and / or moved together with the protective device. After singulation and before removing the chips, the wafer together with the protective device can advantageously be rotated about an axis parallel to the first face of the wafer by an angle of 170° to 190°, preferably 180°, for the purpose of removing the chips, wherein the holding structure for this purpose is embodied such that the chips remain on the wafer during the rotation. For the rotation, the protective device is releasably or non-releasably connected to the wafer, for example by means of a bond and / or a fixing device for temporarily fixing the wafer. The formation of a gap structure for singulating the wafer is particularly advantageous in combination with this rotation if the gap structure comprises a suitable holding structure. For this purpose, for example, the gap structure can have a groove at an appropriate position on one side of the gap of the gap structure, the groove being carried out along a first face parallel to the wafer, and the gap structure can have a protrusion at the same position on the opposite side of the gap, for example, a protrusion in the form of a track or a protrusion, in such a way that the track or protrusion is received by the groove and a spatial distance is retained between the two components. Thus, the combination of groove and protrusion provides a loose connection between each chip and the rest of the wafer. In this case, the groove can be implemented in the chip, and therefore, the protrusion belongs to the rest of the wafer. However, the opposite configuration (groove in the rest of the wafer, protrusion related to the chip) can also be conceived in the same way. The rest of the wafer can be formed by one or more appropriate depressions so that the protrusion or track can be displaced by the chip. Thus, the loose connection can be separated. Thus, by this mechanism, after singulation, the chip can first be held in the wafer and then released in a targeted manner because the chip can be removed from the wafer.

[0017] Rotating the wafer by 170° to 190° can be particularly advantageous if the protective device is mounted on the wafer before the rotation, that is to say, in particular if the contact between the wafer and the protective device is achieved by applying the protective device to the wafer from above. In the context of the present invention, the terms "above" and "from top to bottom" relate to the direction of gravity: an object is "above" another object if it is arranged in relation to the other object in the opposite direction of gravity. Thus, "from top to bottom" means that the object acts in the direction of gravity; "upward" means in the opposite direction of gravity. The terms "below", "from bottom to top" and "downward" can be understood equivalently. In the case described, the support structure of the protective device supports the wafer after the rotation, and the rotation is carried out about an axis perpendicular to the direction of gravity. The chip can be removed from the wafer after the rotation. This method is particularly preferred if, for certain method steps, it is preferred that the first side of the wafer protected by the protective device is positioned upward and / or if the protective device is located on the wafer. For example, it may be the case that, for etching purposes, etching gas is supplied via openings in the region of the outer wall of the protective device. In this case, it is generally advantageous that this opening is distributed as evenly as possible over as large an area as possible. If the regions of the outer wall are intended to serve as a base for positioning the protective device on the storage element, the openings present in these regions run the risk of being blocked, and gas supply thus becomes impossible. The possible positions of the openings for gas supply are therefore limited. This restriction can be waived, for example, by performing an etching process with the protective device directed toward the wafer so that the protective device is arranged above the wafer. Therein, there is no risk of the opening for supplying etching gas being blocked; the position of this opening can be freely selected. Since, after singulation, the chip must be removed in a direction that is not blocked by the protective device, it is generally necessary to rotate the wafer for the purpose of removal. After performing the etching process, for the purpose of removing the chip, the wafer is therefore rotated preferably by 180° together with the protective device about an axis parallel to the first face (i.e. about an axis perpendicular to the direction of gravity) and positioned on the storage face.

[0018] Before singulating the wafer, any desired steps in the context of the present production method can be envisaged. For example, in order to prepare the wafer for further method steps in the production method, sinter paste and / or solder can be applied to the second side of the wafer after contacting the wafer with the protective device. Furthermore, for example, wafer bonding of a second wafer, for example by eutectic bonding, can be performed. Testing of the wafer with respect to the functionality of the wafer (wafer testing) and / or testing of wafer components can also take place before singulation while the wafer is still in contact with the protective device.

[0019] According to a second aspect of the invention, a protective device having one or more supporting structures for temporarily supporting a wafer on a protective device and / or temporarily supporting a protective device on a wafer is proposed, wherein the protective device is configured for use in a method according to the invention. Typically, the wafer to be protected is placed with a first surface to be protected facing downwards on one or more supporting structures of the protective device, wherein the first surface of the wafer is arranged in such a way as to be oriented perpendicular to the direction of gravity. Furthermore, the protective device is also implemented so that it can be positioned on the wafer, i.e., it is usually applied to the wafer from top to bottom, wherein the first surface of the wafer to be protected faces upwards. In this case, the supporting structure carries the protective device on the wafer.

[0020] The protective device according to the invention can consist essentially of silicon, which can be provided with a passivation layer, for example, to provide protection against the etching gas used. The advantage of using silicon is that in the case of temperature changes, the protective device has the same expansion and contraction range as the wafer with which it is in contact and which is also composed of silicon. Therefore, no displacement and no unwanted mechanical stresses occur between the wafer and the protective device. The passivation layer can, for example, consist of silicon dioxide and / or silicon nitride. Alternatively, the protective device according to the invention can also consist of other materials or material compositions, for example, metals and / or metal alloys, for example, steel and / or ceramics.

[0021] Preferably, the protective device at least partially shields the environment of the protective device with one or more outer walls to prevent unwanted substances, such as foreign particles, from reaching the first protected face of the wafer, in particular, the protected structure located there. For example, the protective device can have one or more side walls and a base. The outer wall of the protective device can have one or more openings for gas supply. Preferably, the one or more outer walls and the wafer positioned in the protective device surround the interior. In addition to the optional openings for gas supply, the one or more outer walls of the protective device are preferably implemented in a gastight manner or have only a low gas permeability. This preferably also applies to the connection between the outer wall of the protective device and the wafer, and the connection between the two outer walls of the protective device. One or more openings for gas supply can be positioned, for example, in the outer wall opposite to the wafer (rear outer wall) and / or in the lateral outer wall (side wall) and are preferably configured to supply etching gas to the interior. By supplying gas and / or positioning the protective device in a corresponding gas atmosphere, it is possible to change the gas pressure inside the protective device. Preferably, the protective device has a plurality of openings for gas supply, which are implemented as holes, which have a size such that unwanted particles (foreign particles) originating from outside the protective device and starting from a certain particle size cannot pass at all or with a sufficiently high probability into the interior of the protective device. Thus, these holes have a filtering function. For example, the size of the holes can be determined by a correspondingly selected diameter so that they do not allow any foreign particles starting from a particle size of 5 microns, 2 microns, 1 micron, 0.5 microns, 0.2 microns, or 0.1 microns to pass through, or only allow them to pass through with a tolerable probability. Thus, these holes can be used to supply etching gas to the interior of the protective device in order to perform an etching process on a wafer positioned on the protective device without contaminating the first side of the wafer with foreign particles of external origin in the step. Preferably, the rear side outer wall of the protective device, i.e. its rear side, is designed to be flat, so that it allows particularly simple handling and can be used as a base on which the protective device and the wafer can be placed together, for example, for wafer testing and / or chip removal steps after singulation.

[0022] The one or more supporting structures of the protective device can have, for example, the form of continuous or interrupted walls, arcs, grids, pillars and / or supports, which are preferably arranged in a grid. In the wafer to be supported, this supporting structure can preferably be at least partially parallel and / or along the gaps and / or trenches of the gap structure and / or trench structure (formed or to be formed for the purpose of singulating the wafer) and can thereby surround the structures to be protected according to the chip and, when for example a continuous wall, can provide further protection for these structures. When contacting the wafer with the protective device according to the invention, for example when positioning the wafer on the protective device, the wafer is preferably arranged so that the supporting structure does not contact, in particular does not contact sensitive areas of the wafer. In order to achieve this and / or simplify the method steps that are automatically performed, the protective device can be formed so that the wafer can only contact the protective device in a defined direction. For example, a groove or a flat surface of the wafer that interacts with a corresponding shape of the protective device can be used for this purpose.

[0023] In a particularly preferred configuration of the protective device according to the invention, the protective device comprises a fixture for fixing the wafer during temporary loading of the wafer. Therefore, the working system of this fixture is to prevent unwanted movement of the wafer. For this purpose, the fixture preferably has one or more fixing components to prevent unwanted lateral displacement of the wafer. This fixing component can, for example, be composed of a frame surrounding the wafer. This frame can also be implemented at the same time so that its sealing protective device is laterally facing outward to better protect the first face of the wafer. In this case, therefore, the frame also acts as an outer wall. Another preferred possibility that can be used as an alternative or in addition to the fixture to prevent unwanted movement of the wafer is to combine the wafer to the protective device.

[0024] The invention discloses a method and a device in a method for producing semiconductor chips for protecting particularly sensitive structures of the corresponding wafer from damage and / or contamination, for example by foreign particles. More specifically, the possibility of protecting the chips during singulation of the wafer is also disclosed. In this case, the protection device according to the invention supports itself in an area outside the chip, so that the fill factor on the individual chips is not negatively affected. The protection device according to the invention can thus protect structures on the wafer without having to produce additional structures on the wafer for this protection device.

[0025] The protection device according to the invention can be optimized for singulating wafers by etching, breaking and / or using lasers. This makes it possible to improve the fill factor of the individual chips and wafers, since it is not necessary to provide wide sawing streets for sawing, and the method is more precise than sawing. In particular, if etching methods and / or laser cutting are used, no unwanted particle contamination occurs.

[0026] Although according to the invention the wafer preferably has to be in contact with the protective device so that one or more supporting structures of the protective device are in contact with the wafer only outside the protected area, the filling factor of the wafer is not impaired as a corresponding area generally also has to remain available for singulation and stabilization of the wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Embodiments of the present invention are explained in more detail with reference to the accompanying drawings and the following description.

[0028] In the attached picture:

[0029] Figure 1A A schematic diagram showing details of an exemplary protection device and a first wafer according to the present invention;

[0030] Figure 1B A schematic diagram showing details of an exemplary protection device and a second wafer according to the present invention;

[0031] Figure 1C Showing that according to the present invention Figure 1B An exemplary protective device and after singulation Figure 1B a schematic diagram of details of a second wafer;

[0032] Figure 2 A schematic diagram showing a plan view and a perspective view of a wafer in a protective device according to the present invention;

[0033] Figure 3A , 3B 3C shows three schematic diagrams of another exemplary protection device according to the present invention with details of a third wafer at different time points; and

[0034] Figure 4 A schematic flow chart showing the method according to the invention for singulating wafers using the protection device according to the invention is shown. DETAILED DESCRIPTION

[0035] In the following description of the embodiments of the present invention, the same or similar components are designated by the same reference numerals, and in individual cases, repeated description of these components is omitted. The figures merely schematically illustrate the subject matter of the present invention.

[0036] Figure 1ASchematic diagram showing details of an exemplary wafer 100 having a first side 100a and a second side 100b (upper half), the wafer being positioned on an exemplary protective device 120 according to the present invention (shown only in the lower half), the lower half showing a surface view of the protective device 120 and also purely for demonstration purposes. In this case, the lower half shows the plane A indicated by the dashed line in the upper half. The upper half shows details of the wafer 100, showing that the first side 100a of the wafer has two open MEMS structures 130, and the figure shows two chips 180a, 180b of the MEMS system produced by singulation of the wafer 100, the MEMS system being referred to as MEMS structure 130. The protective device 120 protects the MEMS structure 130.

[0037] Starting with the chips to be produced, the left chip 180a is surrounded by a partially through-wafer gap structure, wherein the gap 140a penetrates the wafer 100 in a vertical direction, and the web 110 has been formed as a connection between the chip 180a to be produced and the remainder 105 of the wafer 100. In order to make the web 110 as thin as possible and thus simplify purely mechanical singulation of the wafer 100 by, for example, breaking, a recess 150 can be provided in the wafer 100, as can be seen in the lower half of the figure, which makes the web 110 thinner than the chip 180a and the remainder 105 of the wafer.

[0038] As shown in the lower half of the figure, the wafer 100 is positioned on the support structure 122 of the protective device 120. The support structure 122 can be a wall-type component, for example, which is parallel to the gap 140a of the gap structure and supports the wafer 100 from bottom to top. In this case, the wafer 100 is placed on the support structure 122 so that the first side 100a with the MEMS structure 130 faces downward and at the same time the support structure 122 is in contact only with insensitive areas of the wafer 100. Thus, for example, by the support structure 122 being implemented as a continuous wall and / or by an outer wall (not shown) surrounding the protective device 120, the MEMS structure 130 can be protected from foreign particles that may be generated by further processing steps performed on or starting from the first side 100b of the wafer.

[0039] The web 110 holds the chip 180a shown on the left, so that work processes such as printing of solder and / or sinter paste, for example bonding to another wafer, wafer testing and finally singulation can still be carried out on the wafer 100. For the purpose of singulation of the wafer 100, the web 110 can be broken off mechanically and / or cut by laser, preferably directly during the removal of the chip 180a from the protective device 120. The web 110 or residues of the web 110 which may remain on the chip 180 after this singulation can, if desired, be completely removed in a further step after the singulation, for example by mechanical and / or laser and / or etching methods.

[0040] exist Figure 1A In the case of the second chip 180b on the right side of the wafer 100, other possibilities for simplifying the subsequent singulation of the wafer 100 are shown: In this case, in the wafer 100, a trench structure with a trench 140b is formed on the second face 100b, but it is also conceivable that the trench structure is formed on the first face 100a. In the case where a trench structure is formed on the first face 100a, it is also conceivable that the trench structure is formed together with a sacrificial layer etching (removing the so-called sacrificial area by etching) for the purpose of processing the wafer 100, for example for the purpose of releasing the MEMS structure 130. For this variant, an opening can be provided in the outer wall of the protective device 120, through which the etching gas can be supplied. For greater simplicity, in this variant, the trench 140b is also depicted in the upper half of the figure, even if the trench is not visible in the view of the first face 100a.

[0041] In the case of the right chip 180b, the distribution of the web 110 is specifically presented, relative to the deformation on the left (chip 180a). Alternatively, by forming the trench 140b, the wafer 100 is thinned continuously around the chip 180b. Subsequent singulation can then be performed along the trench 140b thus formed, for example by etching and / or laser cutting and / or, if the remaining wafer 100 in the region of the trench 140b is thin enough, by breaking.

[0042] Figure 1B Displays something like Figure 1A The second wafer 101 (upper and lower half of the diagram) of the schematic diagram also has a first surface 101a and a second surface 101b, and again has Figure 1A 1 is a side view of a detail of an exemplary protection device 120 according to the present invention relative to plane A. Like wafer 100, wafer 101 has an open MEMS structure 131 on a first side 101a, which is provided for chip 181. Areas 141 (etched structures) provided for a subsequent etching process to singulate wafer 101 are indicated at Figure 1BAs can be seen from the lower half of the figure, these etched structures 141 only partially penetrate the wafer. For simplicity, these etched structures 141 are also depicted in the upper half of the figure, even though as can be seen from the lower half of the figure, these etched structures 141 are not visible in the view of the first side 100a.

[0043] Furthermore, recesses 151 are embodied in the wafer 101, which may have been produced by a previous etching process and constitute trenches surrounding each chip 181. Therefore, in the context of the present invention, the totality of these trenches 151 constitutes a trench structure surrounding each chip 181. Figure 1A 1 , where the trench structures are embodied on the first face 100a. The recesses 151 have the form of an L-shape realized by corresponding undercuts 160 of the wafer 101. These undercuts 160 act as retaining structures. If the wafer is singulated by etching the areas of the etched structure 141 along the trench structures formed by the recesses 151 (or some other method is used to remove material of the wafer in these areas for singulation), the chips 181 are separated from each other and from the rest of the wafer 106. Figure 1B As shown by arrow 190 in FIG. 1 (if the protective device 120 and the wafer 101 are perpendicular to the direction of gravity), each chip 181 first falls vertically downward, but as in FIG. Figure 1C As shown, it is then braked by the retaining structure. Figure 1B and 1C As shown, the retaining structure can also be implemented only locally, ie it does not need to be present at every point of the trench or gap.

[0044] Figure 1C Shown in Figure 1B After singulation of the wafer 101 with the etched structures 141 removed, the etched structures 141 are now replaced with cavities 142 according to the wafer 101 and the protective device 120 of the present invention. Figure 1B For the sake of clarity, the cavity 142 is depicted here in the etched structure 141, but in the view of the face 100a of the wafer 100, the cavity is not actually visible.

[0045] As shown, the protrusions 185 on the chips 181 implemented by the recesses 151 in the wafer 101 ensure that the downward movement 190 of each chip 181 is stopped because these protrusions 185 are captured on the remaining part 106a of the rest of the wafer 106. This prevents the situation where the chips 181 collide with the open MEMS structure 131 after singulation, for example, against the base of the protective device 120, which may cause damage to the open MEMS structure 131. However, after singulation, the chips 181 can be removed from the protective device 120 upwards (i.e., opposite to the direction of gravity and, therefore, in the direction of arrow 190) (arrow 195), for example, by a suitable removal device 192, which can be vacuum-based. After singulation and removal of each chip from the protective device, the protrusions 185 can be completely removed in a further step, for example mechanically and / or by laser cutting and / or etching methods.

[0046] From Figure 1A The steps can also be further combined from Figure 1B and 1C The steps are performed to prevent the chips 180a, 180b from unintentionally falling and / or falling after singulation when the chips 180a, 180b cannot be directly singulated and removed from the protection device 120.

[0047] Figure 2 A schematic diagram of another wafer 200 in another exemplary protective device 220 according to the present invention is shown in plan view (half view A) and perspective view (half view B). The wafer 200 has MEMS structures 230 (only shown in half view A) located on twelve chips 280 to be produced. In half view A, these MEMS structures 230 are located on the back of the wafer 200. Figure 2 20 is not shown on the side facing the viewer, which is why the corresponding square representing the MEMS structure 230 is indicated with a dashed edge. The same can also be applied to the supporting structure 222 of the protective device 220, which is also indicated with dashed lines and represents a continuous wall under the wafer 200. Advantageously for the protective device 220, the protective device 220 has walls 221 that laterally close the protective device 220 in order to protect the downwardly facing surface of the wafer 220 from damage and contamination. The protective device 220 also has a fixing assembly 224, which is constituted by a frame 226 surrounding the wafer 220. This frame prevents the wafer 220 from being undesirably displaced laterally. The fixing assembly 224 is advantageously shaped so that a notch or flat cut 228 of the wafer 220 (not shown in half B) is used to achieve the desired orientation of the wafer 220 during positioning of the wafer 220 in the protective device 220 (during contact between the wafer 220 and the protective device 220). For example, for this purpose, the frame 226 may be provided with corresponding lobes 228 (not shown in half-figure B).

[0048] Figure 3A ,3B 3C and 3D are three schematic diagrams showing details of another exemplary protection device according to the present invention, with a third wafer after different steps of the method according to the present invention. The three figures are shown in side view. In this embodiment of the present invention, the gap structure is used for singulation.

[0049] Figure 3A An exemplary protection device 320 according to the invention is shown, having a support structure 332, which is in contact with a wafer 300 having two faces 300a and 300b. The wafer 300 is located on a storage member 310. Two chips 380a, 380b to be produced are shown by way of example, which have open MEMS structures 330. These open MEMS structures 330 face upward. The protection device 320 is positioned on the wafer 300 so that the first face 300a of the wafer is in contact with the support structure 322, which does not contact the open MEMS structures 330. In order to avoid unwanted displacement of the wafer and the protection device relative to each other and to achieve a subsequent rotation of the protection device and the wafer, the protection device is bonded to the wafer.

[0050] In each case, the wafer 300 has etch structures 340 on the left and right sides of the chips 380a, 380b to be produced, which delimit the chips 380a, 380b. These etch structures 340 are used to form gap structures that allow the wafer 330 to be singulated. At the same time, the holding structures 360 are intended to be embodied by the etching process, these future holding structures 360 comprising laterally positioned recesses 386 in the chips 380a, 380b and matching protrusions arranged in the adjacent wafer portion 390 of the rest of the wafer 305. The holding structures 360 are partially delimited, that is, they do not extend along the complete etch structures 340. Figure 3A , 3B , 3C each show a cross-sectional view precisely penetrating the holding structure 360. The recess 323 is positioned in the region below the wafer portion 390 having the protrusion 385 to enable movement of the wafer portion 390 having the protrusion 385 after the etching process of etching the etched structure 340. Thus, the support structure 322 is exposed in the region of the wafer portion 390. To enable movement of the protrusion 385 and the wafer portion 390 associated therewith, other etched structures 342 are located in the region of these wafer portions 390. After the etching process is completed, the wafer portion 390 of the wafer 300 located between the etched structures 340 and 342 can be moved and can be configured as a spring assembly, for example.

[0051] Furthermore, a hole 328 for supplying etching gas is located in the rear outer wall 326 of the protective device 320. For this purpose, the protective device 320 and the wafer 300 are located in an environment filled with etching gas. The etching gas penetrates the hole 328 into the interior 325 of the protective device 328; the etching structure 340 and the other etching structures 342 are etched. In this case, the etching gas can reach the other etching structures 342 via the recess 323. At the same time, the etching gas introduced into the interior 325 can, for example, be used to achieve sacrificial layer etching, thereby releasing the MEMS structure 330. For greater clarity, in each Figure 3A , 3B In FIG. 3C , only twelve holes 328 are shown, wherein this number is purely exemplary and can be much larger. Furthermore, the holes 328 are not depicted in the figures with real dimensions. The holes 328 generally have a selected diameter so that unwanted foreign particles starting from a certain size cannot enter the interior 325 from the environment.

[0052] Figure 3B It is shown that after the etching process is performed by the etching gas supplied through the hole 328, Figure 3A An exemplary protection device 320 according to the present invention and a corresponding wafer 300 are shown. By means of etching gas, the etching structure 340 is removed, which results in the formation of a gap structure having a gap 350 in the wafer 300, and the wafer 300 is thus singulated. Figure 3B In comparison with Figure 3A The MEMS structures 330 of the chips 380a, 380b are likewise released by the etching gas, as indicated by the different illustrations of the area of ​​the MEMS structure 330. Furthermore, the wafer together with the protective device is rotated by 180° about the rotation axis 315 running parallel to the first face 300a of the wafer 300 and, after the rotation, is positioned again on the storage element 310, blocking the hole 328. Therefore, it is no longer possible for the etching gas to be supplied via the hole 328. After the etching process, the rotation is performed. The holding structure 360 ​​with the interlocking protrusions 385 and recesses 386 present as a result of the etching process fixes the chips 380a, 380b in the wafer 300 after singulation by means of these protrusions 385 and recesses 386; the chips 380a, 380b cannot move freely upwards or downwards. Therefore, the protective device and the wafer can be rotated together without the risk of the chips 380a, 380b falling out.

[0053] For example, a vacuum removal device 392 is positioned on the left chip 380a and temporarily fixed on the chip 380a. In order for this chip 380a to now be removed, the wafer part 390 with the protrusion 385 is moved away from the groove 386 of the chip 308a (arrow 396). According to the other etching structures 342 formed by the etching process, since the cutout 370 has been etched in the wafer 300 in the movement direction 396, this movement in the direction 396 becomes possible. The movable wafer part 390 with the protrusion 385 can now be configured as a spring element, for example, and can be moved away from the chip 380a by a suitable tool (not shown). In this case, the chip 380a is continuously held by the removal device to prevent the chip 380a from falling.

[0054] Figure 3C The state after moving the wafer portion 390 with the protrusion 385 in the direction 396 is shown, the protrusion 385 is now completely positioned outside the groove 386. The chip 380a can now be moved upward and downward independently of the rest of the wafer 305, but is still fixed by the removal device 392 and can be removed from the wafer 300 upward (arrow 395) together with the removal device 392. Figure 3B and 3C The steps shown may also be applied to other chips in wafer 300 , for example, chip 380 b .

[0055] at last, Figure 4 A schematic flow chart of a method according to the present invention is shown for singulating wafers 100, 101, 200 using a protective device 120, 220 according to the present invention, wherein the wafers 100, 101, 200 have a first side 100a, 101a and a second side 100b, 101b, wherein a structure to be protected, such as a MEMS structure 130, 131, 230, is positioned on the first side 100a, 101a of the wafers 100, 101, 200.

[0056] The wafer 100, 101, 200 is contacted with the protection device 120, 220 according to the present invention (step 410), for example, positioned thereon, specifically, so that the first side 100a, 101a of the wafer 100, 101, 200 is in contact with the supporting structure 122, 222 of the protection device 120, 220. The typical protection device 120, 220 according to the present invention holds the wafer 100, 101, 200 in the opposite direction of gravity, the wafer 100, 101, 200 is supported on the supporting structure 122, 222, and the first side 100a, 101a of the wafer 100, 101, 200 faces downward (in the direction of gravity). The protection device 120, 220 protects the surface having the structure to be protected, that is, the first side 100a, 101a of the wafer 100, 101, 200 from being contaminated or otherwise damaged by foreign particles.

[0057] The wafer 100, 101, 200 may then be processed as desired. More specifically, after positioning the wafer 100, 101, 200 on the protective device 120, 220, it is possible for the wafer 100, 101, 200 to be provided with a gap structure, for example, by means of an etching process, partially penetrating the gap structure 140a and / or the trench structure 140b (step 415). This gap structure and / or partially penetrating the gap structure and / or the trench structure 140a, 140b may subsequently be used to singulate the wafer 100, 101, 200 into individual chips 180a, 180b, 181, 280. Alternatively or additionally, this structure may be formed before contacting 410 the wafer with the protective device 120, 220 (step 405).

[0058] After contacting 410 the wafer with the protective device, it is also possible to carry out further processing steps 420 at the same time, for example, to carry out a soldering and / or sintering process and / or to apply a corresponding solder and / or sintering paste, for example, by printing. More specifically, a wafer can be joined to another wafer to produce a coupled wafer. Furthermore, wafer testing of the wafers 100, 101, 200 and / or of the future chips 180a, 180b, 181, 280 can be carried out. Finally, singulation 430 of the wafers 100, 101, 200 is carried out, wherein, when the wafers 100, 101, 200 are correspondingly prepared with gaps and / or trench structures 140a, 140b, the singulation 430 is preferably carried out by mechanical breaking and / or laser cutting. Here, for example, in the case of singulation 430 by breaking, the removal 440 can be carried out in parallel with the singulation 430. For example, for this purpose, the chips 180a, 180b, 181, 280 are broken off from the wafer 100, 101, 200. At this point, when the chips 180a, 180b, 181, 280 still remain in the protective device 120, 220 after singulation 430, advantageously held by corresponding holding structures before removal 440, the chips 180a, 180b, 181, 280 can also be tested for their correct function at this point in time in the protective device 120, 220.

[0059] The invention is not limited to the exemplary embodiments described herein and the aspects emphasized herein. On the contrary, numerous modifications within the capabilities of a person skilled in the art are still possible within the scope specified by the claims.

Claims

1. A method for singulating a wafer (100, 101, 200, 300), the wafer having a first surface (100a, 101a, 300a) and a second surface (100b, 101b, 300b) located opposite to the first surface (100a, 101a, 300a), characterized in that: The method comprises the following steps: a. contacting (410) the wafer (100, 101, 200, 300) with a protective device (120, 220, 320) having one or more supporting structures (122, 222, 322), so that the first surface (100a, 101a, 300a) of the wafer (100, 101, 200, 300) contacts the one or more supporting structures (122, 222, 322); b. singulating (430) the wafer (100, 101, 200, 300) in contact with the protection device (120, 220, 320) into a plurality of chips (180a, 180b, 181, 280, 380a, 380b); and c. removing (440) the chip (180a, 180b, 181, 280, 380a, 380b) from the wafer (100, 101, 200, 300) in contact with the protection device (120, 222, 322).

2. The method according to claim 1, characterized in that After contacting (410) the wafer (100, 101, 200, 300) with the protective device (120, 220, 320) and before or simultaneously singulating (430) the wafer (100, 101, 200, 300): ● forming (405, 415) a gap structure that surrounds each chip (380a, 380b) and has one or more gaps (350) in the wafer (300), and the singulation (430) is performed at least in part by forming the gap structure; and / or ● forming (405, 415) a gap structure that surrounds each chip (180a), partially penetrates the wafer (100) and has a plurality of gaps (140a) in the wafer (100), and the singulation (430) is performed at least partially along these plurality of gaps (140a); and / or · Forming (405, 415) a trench structure that surrounds each chip (180b, 181) and has one or more trenches (140b, 151) on the first surface (100a) and / or the second surface (100b) of the wafer (100, 101), and the singulation (430) is performed at least partially along the one or more trenches (140b, 151).

3. The method according to claim 2, characterized in that The gap (140a, 350) and / or the trench (140b, 151) are formed (405, 415) by an etching process.

4. The method according to claim 3, characterized in that The etching process is also used to etch the structure of the chip (180a, 180b, 181, 280, 380), for example, sacrificial layer etching.

5. The method according to any one of claims 1 to 4, characterized in that: The singulation (430) is performed using etching, laser cutting and / or breaking.

6. The method according to claim 1, characterized in that The wafer (100, 101, 200, 300) has an open MEMS structure (130, 131, 230, 330) for a micro-electromechanical system.

7. The method according to claim 6, characterized in that The open MEMS structure has a first surface (100a, 101a, 300a) open to the wafer (100, 101, 200, 300), and the wafer (100, 101, 200, 300) is in contact with the protection device (120, 220, 320), so that the one or more supporting structures (122, 222, 322) do not contact the open MEMS structure (130, 131, 230, 330).

8. The method according to claim 6 or 7, characterized in that: The open MEMS structure (130, 131, 230, 330) includes a MEMS structure for a micro-mirror array.

9. The method according to claim 1, characterized in that: The wafer (101, 300) has a holding structure (160, 360), and / or a holding structure (160, 360) is formed in the wafer (101, 300) after contacting (410) with the protective device and before singulating the wafer (101, 300), wherein the holding structure (160, 360) is configured to limit possible movement of the chip (181, 380) in at least one direction after singulation.

10. The method according to claim 9, characterized in that The wafer (300) is connected to the protective device (320), and after singulation and before the chip (380) is removed, the wafer (300) and the protective device (320) are rotated together at an angle of 170° to 190° around an axis (315) parallel to the first surface (300a) of the wafer (300), and the holding structure (360) is implemented so that during the rotation, the chip (380) remains in the wafer (360) and the wafer (300) is connected to the protective device (320).

11. The method according to claim 10, characterized in that The protection device (320) is disposed on the wafer (300) prior to the rotation.

12. The method according to claim 1, characterized in that Singulating (430) the wafer (100) is performed by removing (440) the chips (180a) from the protective device (120).

13. A protection device (120, 220, 320), comprising one or more supporting structures (122, 222, 322), for temporarily supporting a wafer (100, 101, 200, 300) on the protection device (120, 220, 320) and / or for temporarily supporting the protection device (120, 220, 320) on the wafer (100, 101, 200, 300), characterized in that: The protection device (120, 200, 320) is configured to be used in a method according to any one of claims 1 to 12.

14. The protection device (220) according to claim 13, characterized in that: The protection device (220) comprises a fixing device (224) for temporarily fixing the wafer (200), wherein the fixing device (224) preferably has one or more fixing components (226) for preventing unwanted lateral displacement of the wafer (200).

15. The protection device (320) according to claim 13 or 14, characterized in that: The protective device (320) has an outer wall (326) with an opening (328) for gas supply.

Images