Method and preparation unit

Abstract

To provide a simplified and enhanced method for planarizing an uneven surface of a workpiece and a preparation unit for preparing the workpiece.SOLUTION: A method of preparing a workpiece 10 for processing includes the steps of providing a workpiece, providing a protective sheeting 20 including at least a first layer 21 and a second layer 22, the second layer being formed from a material having a higher glass transition temperature or melting temperature than the first layer, combining a first side 11 of the workpiece and the first layer of the protective sheeting, and applying heat to the first layer of the protective sheeting through the second layer of the protective sheeting.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method of preparing a workpiece for processing and a preparation unit for preparing a workpiece for processing.

[0002] Device chips are typically fabricated by forming devices in areas defined by parting lines on the surface of a substrate (wafer). However, devices formed on the front side of the substrate cause the front side to have a non-uniform profile. In other words, the front side is not flat, but has various grooves, depressions, and protrusions, resulting in a non-uniform surface profile on this side, which can cause difficulties when processing the substrate.

[0003] More specifically, this unevenness on the front side of the substrate has been shown to be susceptible to damage or result in damage when the substrate is mechanically processed from the side opposite the front side, such as by grinding or dicing. One reason identified as the cause is that forces applied during processing are unevenly distributed across the surface of the front side of the substrate due to various supports, which tend to cause stress peaks and can lead to cracks in the substrate and device.

[0004] As an approach to preventing this damage during processing, various techniques have been proposed to compensate for the uneven surface of the front side of the substrate that causes uneven support.

[0005] For example, U.S. Patent Application Publication No. 2017 / 062278 A1 proposes providing a carrier in which a protective film covering devices on one side of a wafer is attached to the wafer, the protective film is bonded to at least a portion of one side of the wafer with an adhesive, and a curable resin is added to the front side of the carrier, and the one side of the wafer with the protective film attached is attached to the surface of the carrier so that the protruding portion protruding from the flat surface of the wafer is embedded in the curable resin.

[0006] A technique has also been proposed in which tape is applied to the front side of a substrate on which a device is formed (see, for example, JP 2013-021017 A). After applying the tape to this uneven device surface on the substrate, the tape experiences surface variations on its exposed surface. These are then removed by flattening the exposed surface through a type of rolling process using a diamond bit. This process also requires additional time and fairly complex machinery to perform properly.

[0007] Also, U.S. Patent Application Publication No. 2020 / 335 382 A1 proposes stacking a sheet and a flat plate on the front side of a substrate. This procedure is followed by a thermocompression step. The sheet is heated through the substrate while a compressive force is applied to the sheet on the substrate through the flat plate. In this way, the sheet is heated from one side and flattened by applying an external force to the sheet from the opposite side through the flat plate. The flat plate is then removed. However, this technique has been found to be effective when the unevenness of the surface profile is relatively small. Summary of the Invention

[0008] Therefore, there remains a need for a simplified and enhanced method for planarizing uneven surfaces of workpieces, particularly those caused by devices formed on the front side of a substrate or wafer.

[0009] To address this objective, the present disclosure provides a method for preparing a workpiece for subsequent processing. The method includes providing a workpiece and a protective sheeting including at least a first layer and a second layer. The second layer is formed of a material having a higher glass transition temperature and / or melting temperature than the first layer. The method also includes combining a first side of the workpiece with the first layer of the protective sheeting and applying heat to the first layer of the protective sheeting through the second layer of the protective sheeting.

[0010] This method has the advantage that it makes it possible to essentially level out irregularities present on a first side of the workpiece, caused for example by a device arranged on that side.

[0011] In particular, planarization is achieved through the protective sheeting by embedding the uneven surface of a first side of the workpiece in a first layer of the protective sheeting, and the second layer is intended to provide an essentially flat surface that can be used to support the workpiece, particularly during mechanical processing using processing forces applied to the workpiece.

[0012] Additionally, applying heat to the first layer through the second layer allows for a uniform heat conduction path that is independent of the workpiece material and thickness, allowing for a fast and responsive heating procedure for the first layer.

[0013] Preferably, when applying heat to at least the first layer of the protective sheeting, the first side of the workpiece faces the heating means, in this way uniform heating can be achieved across the first side of the workpiece, which certainly affects the leveling function of the protective sheeting.

[0014] The difference in glass transition temperature and / or melting temperature between the first and second layers allows for control of the malleability of the two layers. In particular, the first layer can be heated to make it more malleable than the second layer. More preferably, the temperatures of the two layers can be controlled so that the material of the first layer is soft enough to absorb irregularities on the first side of the workpiece. For example, the material of the first layer may be plastically deformed by displacing material located in a protruding area on the first side into an adjacent, less protruding area. At the same time, the second layer can essentially maintain a solid state, substantially preventing deformation.

[0015] The first layer of the protective sheeting is preferably in contact with the first side of the workpiece, and this contact between the first layer and the first side of the workpiece (i.e., touching or no contact therebetween) is advantageous in that the first layer compensates for irregularities on the first side of the workpiece.

[0016] The method may further include the step of placing the second layer of protective sheeting on a heating means, the heating means being configured to apply heat to the first layer of protective sheeting through the second layer of protective sheeting.

[0017] Thus, since the heating means is configured to apply heat to the first layer through the second layer in a controlled environment, a predetermined heating protocol can be easily used, in other words, heat can be applied to the first layer in a predeterminable manner.

[0018] Preferably the second layer is in contact with the heating means. Additionally, the second layer of protective sheeting may be held on the heating means under suction.

[0019] When the second layer is placed in contact with the heating means, efficient and uniform heat transfer is achieved, which can be further supported by using suction to enhance contact between the heating means and the second layer.

[0020] The first and / or second layer is preferably provided as a foil or film, which allows for better conformability to the workpiece surface during application and easy removal after processing.

[0021] The first and second layers are preferably made of a polymer material (particularly a polymer film), and more preferably the polymer materials of the first and second layers are different from each other. For example, the first layer may be made of polyolefin or polypropylene, and / or the second layer may be made of polyethylene terephthalate (PET).

[0022] Polymer materials are easy to handle and can be easily applied as films. The use of different polymer materials for the first and second layers allows for the adaptation of materials or material properties depending on the function of the protective sheeting.

[0023] As previously indicated, the surface structure may be formed or present on the first side of the workpiece. When heat is applied to the first layer of the protective sheeting, the first layer softens, and after applying heat to the first layer of the protective sheeting, the surface structure is embedded in the first layer. When heat is applied to the protective sheeting, preferably, only the first layer softens. In other words, the first layer preferably softens (e.g., by assuming a malleable state), and the second layer remains undeformed, unsoftened, or in a solid state.

[0024] The first layer of the protective sheeting is preferably heated to a temperature above the glass transition or melting temperature of the first layer and below the glass transition or melting temperature of the second layer.

[0025] Thus, the first layer becomes malleable before the second layer, enhancing its embedding properties. In contrast, the second layer maintains a flat surface, which, as mentioned above, is advantageous for supporting the workpiece during processing. This is particularly achieved when the second layer is heated only below its glass transition temperature or melting temperature.

[0026] At least the step of placing the first side of the workpiece on the first layer of protective sheeting and / or the step of applying heat to the first layer of protective sheeting may be performed under essentially vacuum conditions, preferably in a vacuum chamber.

[0027] The use of a vacuum environment during the process of attaching the first layer to the workpiece, among other things, prevents gas from becoming trapped between the workpiece and the first layer, which could otherwise form bubbles, and can speed up the process of placing, applying, or embedding the first layer, since there is no gas to prevent contact between the first layer and the workpiece.

[0028] At least during or after applying heat to the first layer of the protective sheeting through the second layer of the protective sheeting, the workpiece and the protective sheeting can be pressed together, preferably by applying a pressure load through the second layer of the protective sheeting and / or the workpiece.

[0029] This, especially in combination with the vacuum environment, enhances and accelerates the filling process of the first layer, in which the displacement of the material of the first layer towards the periphery of the recesses and protrusions is supported by mechanical pressure.

[0030] This pressure may be applied through the workpiece and / or the second layer, i.e., the means for applying pressure is located on the side or sides of the workpiece. In either case, the pressure acts on the first layer to promote its processing, filling the recesses in the workpiece on the side facing the first layer. Applying pressure through the workpiece while the protective sheeting is held on the chuck table is preferred for easier handling.

[0031] The second layer, particularly the side of the second layer opposite the side facing the first layer, can include a substantially flat shape, and the shape of the second layer remains essentially unchanged upon application of heat to the first layer of the protective sheeting.

[0032] Prior to the step of applying heat to the first layer, the side of the second layer of the protective sheeting facing away from the workpiece preferably has a uniform or flat surface when placed on a flat surface, such as the surface of a chuck table or pad. Even more preferably, this also applies to the side of the first layer facing the workpiece. This condition of the side of the second layer remains essentially unchanged, particularly during the step of applying heat (and possibly pressure), and the side of the first layer facing the workpiece at least partially embeds the surface topography of the side of the workpiece facing the first layer.

[0033] As a result, the flat side of the second layer of protective sheeting provides a flat support surface for processing the workpiece, while the deformed first layer maintains uniform support on the side of the workpiece, thereby preventing cracks that may occur during processing.

[0034] The present disclosure also addresses the above-mentioned object by providing a preparation unit for preparing a workpiece, the preparation unit being configured to attach a protective sheeting to a workpiece. The protective sheeting has at least a first layer disposed on a side of the workpiece and a second layer disposed on a side opposite the workpiece. The workpiece preparation unit includes a chuck table including a holding surface that holds the workpiece via the second layer, heating means, and a control unit configured to control the heating means so that the first layer is heated via the second layer according to a predetermined heating protocol.

[0035] The preparation unit is therefore configured to apply any of the above-mentioned methods to the protective sheeting in order to apply it to the workpiece.

[0036] Preferably, the predetermined heating protocol heats the first layer of the protective sheeting through the second layer of the protective sheeting so that the first layer softens (i.e., becomes malleable) and is able to embed the surface structure of the workpiece facing the first layer.

[0037] Thus, the preparation unit achieves the above-mentioned advantages for achieving uniform support of the workpiece during subsequent machining (e.g., grinding, dicing, etc.).

[0038] The preparation unit comprises in particular pressure means arranged to apply a pressure load to the first layer.

[0039] As described above, applying pressure assists the embedding process of the surface structure of the workpiece into the first layer. The pressure means preferably has a substantially flat surface for applying pressure via the workpiece side and / or the second layer side so as to act between the workpiece and the first layer during the embedding process. In other words, the pressure means is specifically positioned on one or both sides of the pressure.

[0040] Additionally, the preparation unit may include a camera configured to inspect an exposed surface of a second layer of protective sheeting attached to the workpiece.

[0041] Such a camera allows the inspection of the surface structure of the workpiece through the protective sheeting and can also be used to check the results of preparing the workpiece for further processing, in particular the embedding of the surface structure and / or the flatness of the exposed side of the second layer.

[0042] Additionally, the camera may be configured as a means of controlling the process, for example, the camera may be used to adjust the position of a dicing blade or a laser beam to process the workpiece. [Brief explanation of the drawings]

[0043] The following figures schematically illustrate exemplary embodiments of a method for preparing a workpiece for processing according to the present disclosure, as well as portions of a preparation unit for preparing a workpiece for processing. In these figures, like reference numerals refer to features having the same or equivalent function and / or structure throughout the figures. It should be understood that the figures illustrate schematic examples of how a method for preparing a workpiece for processing may be performed in accordance with the present disclosure, but are not intended to limit the invention thereto. [Figure 1] FIG. 1 schematically illustrates an exemplary embodiment and arrangement of a workpiece and protective sheeting used to prepare the workpiece for subsequent processing. [Figure 2] FIG. 2 illustrates diagrammatically the arrangement shown in FIG. 1 installed in a preparation unit for preparing a workpiece. [Figure 3] FIG. 3 illustrates a schematic diagram of an exemplary embodiment of a process for preparing a workpiece. [Figure 4] FIG. 4 illustrates, in schematic form, another embodiment of a process for preparing a workpiece for subsequent processing. [Figure 5] FIG. 5 schematically illustrates inspection of a workpiece prepared in accordance with the present disclosure. [Figure 6] FIG. 6 illustrates a schematic example of a subsequent workpiece prepared in accordance with the present disclosure. [Figure 7] FIG. 7 illustrates a schematic representation of a workpiece formed as a wafer.

[0044] Detailed Description of the Preferred Embodiments

[0045] The method of preparing a workpiece for processing and the preparation unit for preparing a workpiece for processing according to the present disclosure will be further described in more detail below with reference to the accompanying drawings.

[0046] In this regard, it should be noted that the drawings show various configurations of methods and components of the preparation unit in a schematic manner, and that the dimensions of the sheeting, workpieces, and machine components have been exaggerated (i.e., shown larger or smaller) for illustrative purposes.

[0047] As mentioned above, the present disclosure aims to prevent workpieces from being damaged when they are processed, particularly by mechanical processes such as grinding, dicing, etc. During processing, forces are applied or generated that cause stresses within the workpiece. If these stresses exceed the limits of the workpiece's material, the stresses may be relieved by cracks that develop. Also, distortions or residual stresses in the material may be induced by such processing.

[0048] One of the factors that can have a significant impact and prevent these negative effects is the proper support of the workpiece during machining. On the one hand, this support is provided by the support means of the machine that processes the workpiece. However, on the other hand, it also depends on the characteristics of the workpiece.

[0049] 1, a workpiece 10, which may be, for example, a wafer or an ingot, is supported on a workpiece support 30. The workpiece 10 comprises a substrate, which may be any (semiconductor) substrate.

[0050] The substrate may include, for example, a semiconductor, glass, sapphire (Al2O3), ceramic such as alumina ceramic, quartz, zirconia, PZT (lead zirconate titanate), polycarbonate, optical crystal material, etc. Specifically, the substrate may include silicon carbide (SiC), silicon (Si), gallium arsenide (GaAs), gallium nitride (GaN), gallium phosphide (GaP), indium arsenide (InAs), indium phosphide (InP), silicon nitride (SiN), lithium tantalate (LT), lithium niobate (LN), aluminum nitride (AlN), silicon oxide (SiO2), etc.

[0051] The substrate can be a single crystal substrate, a glass substrate, a compound substrate such as a compound semiconductor substrate (eg, a SiC, SiN, GaN, or GaAs substrate), or a polycrystalline substrate (eg, a ceramic substrate).

[0052] As described above, the substrate may be a wafer. For example, the substrate may be a semiconductor-sized wafer. Here, the term "semiconductor wafer" refers to a wafer having a predetermined dimension (normalized dimension), in particular, the diameter (normalized diameter, outer diameter) of the semiconductor wafer. Such dimensions of a semiconductor wafer are defined, for example, in SEMI standards. For example, the dimensions of polished monocrystalline silicon wafers are specified in SEMI standards M1 and M76. The semiconductor-sized wafer may be a 3-inch, 4-inch, 5-inch, 6-inch, 8-inch, 12-inch, or 18-inch wafer.

[0053] The substrate may be made of a single material or a combination of different materials, for example, two or more of the materials identified above.

[0054] On a substrate, in particular a wafer, functional layers or devices may be formed (see FIG. 7). Such functional layers or devices are preferably formed on one side of the substrate. On this side, the substrate may comprise a central device region 15 in which devices or functional layers are formed, and a peripheral limiting region 16 surrounding said device region 15. Preferably, no devices or functional layers are formed in said peripheral region 16.

[0055] Hereinafter, the side of substrate or workpiece 10 on which device region 15 is formed will generally be referred to as first side or front side 11 of workpiece 10. The opposite side of substrate or workpiece 10 will be referred to as second side or backside 12 of workpiece 10.

[0056] The devices in device region 15 may be ICs (integrated circuits) or LSIs (large-scale integrated circuits). For example, the devices may be semiconductor devices, power devices, optical devices, medical devices, electrical components, MEMS devices, or combinations thereof. The devices may comprise or be transistors, such as MOSFETs, insulated gate bipolar transistors (IGBTs), or diodes, such as Schottky barrier diodes.

[0057] The workpiece 10 may be supported by a workpiece support 30 on either the front side 11 (see FIG. 3) of the workpiece 10 bearing the functional layer or device or the opposing back side 12 (see FIG. 4).

[0058] The shape of the workpiece 10 is not particularly limited. The workpiece 10 may be cylindrical and / or plate-shaped, and may have a cross-section with a substantially circular outer shape (defining the periphery of the workpiece 10), such as an oval or circle. In other words, in a top view, the workpiece 10 may have a generally round shape, particularly an oval or circle shape.

[0059] However, workpiece 10 may have at least one straight section (not shown) or notch 13 along its cross-sectional profile. In particular, in top view (or in a cross-section perpendicular to its longitudinal axis), workpiece 10 may have the shape of a polygon (plate), such as a square or rectangle. Plate-like in this context means that the thickness, i.e., longitudinal dimension, of workpiece 10 is significantly smaller than the transverse / lateral dimension of workpiece 10. The peripheral edges of workpiece 10 may be rounded or chamfered.

[0060] The front side 11 and / or back side 12 of the workpiece 10 are preferably substantially parallel. Furthermore, the back side 12 of the workpiece 10 may be substantially flat or planar. However, the workpiece 10 has a height difference at least on its front side 11. When the front side 11 of the workpiece 10 has a device region 15 formed thereon, the front side 11 may have a plurality of protrusions, such as bumps protruding from the functional layer. Thus, the protrusions result in an uneven front side 11 or surface of the workpiece 10.

[0061] Furthermore, the workpiece 10, and in particular the functional layers, may also have recesses such as grooves, for example in the form of parting lines between devices. Along these parting lines, the workpiece 10 is divided to obtain single device chips. Also, the functional layers formed on the front side 11 may themselves have height differences (with or without bumps).

[0062] Thus, the front side 11 of the workpiece 10 may have an uneven surface (ie, surface structure) due to the presence of multiple devices or device chips.

[0063] The following example is used to illustrate how an uneven surface on the front side 11 of the workpiece 10 can be flattened in accordance with the present invention by adding a protective sheeting 20. Preferably, the protective sheeting 20 comprises or consists of at least a first layer 21 and a second layer 22. The protective sheeting 20 is configured to conform to the shape of the workpiece 10 on one side and to provide a flat support surface on the opposite side.

[0064] The first layer 21 and the second layer 22 may be provided as separate layers that are attached to each other to form the protective sheeting 20, or may be provided as a prefabricated protective sheeting 20 (e.g., a bi-layer film). The protective sheeting may include an adhesive layer to bond the first layer 21 and the second layer 22 to each other. In contrast to a plate, a film has essentially no bending stiffness when a force is applied perpendicular to the film. The film is preferably formed as a sheeting or applied by spray coating.

[0065] As shown in FIG. 1, the protective sheeting 20 is disposed on the first front side 11 of the workpiece 10, with the first layer 21 facing the workpiece 10 and the second layer 22 facing in the opposite direction, i.e., away from the workpiece 10.

[0066] The first layer 21 of the protective sheeting is configured to be conformable to the surface structures (i.e., protrusions and / or depressions) present on the front side 11 of the workpiece 10. The protrusions and depressions can be defined based on an average height (arithmetic) or a median height. Alternatively, the peripheral limiting region 16 (without formed devices, parting lines or streets, chamfers or rounded edges) has the original height of the bare wafer and may be used as the reference height.

[0067] In contrast, second layer 22 is configured to essentially maintain its shape at least or particularly on the side of protective sheeting 20 facing away from the workpiece while first layer 21 conforms to its shape, as described in more detail below. For reasons described in more detail below, second layer 22 can also be configured to enhance heat transfer. In such a configuration, second layer 22 can be essentially flat and provide a support surface parallel to second side 12 of workpiece 10.

[0068] These different characteristics of the first layer 21 and second layer 22 of the protective sheeting 20 make it possible to provide uniform support to the side of the second layer 22 (i.e., the side exposed to the protective sheeting 20) through a flat surface and to essentially maintain this uniform support at the interface between the first layer 21 and the front side 11 of the workpiece 10.

[0069] Preferably, the protective sheeting 20 is applied as a unit when combining the first side 11 of the workpiece 10 and the first layer 21 of the protective sheeting 20. Furthermore, the first layer 21 is made malleable (at least partially and permanently) to conform to its shape, while the second layer attached to the first layer is even more preferably essentially non-conforming (i.e., essentially not subject to plastic deformation). It can also be configured to enhance heat absorption.

[0070] Due to the different functions of these layers, the first layer 21 and the second layer 22 are preferably made of a polymer material, and in particular are provided as a polymer film. Polymer materials have the advantage that they can be engineered to have material properties that fulfill the functions of the first layer 21 and the second layer 22 of the protective sheeting 20. As mentioned above, the films used preferably do not have significant bending stiffness. This is particularly advantageous for the first layer 21, which is configured to conform to the surface structure of the first side 11 of the workpiece 10.

[0071] Preferably, the polymer materials of the first layer 21 and the second layer 22 are different from each other: the first layer 21 is preferably made of polyolefin and / or polypropylene, and the second layer 22 is preferably made of polyethylene terephthalate (PET).

[0072] Preferably, first layer 21 is at least partially directly attached to (i.e., in physical contact with) front side 11 of workpiece 10. If a (central) device region 15 is present, first layer 21 is in contact with device region 15 in particular, and may be in contact with the entire front side 11 (i.e., (preferably completely) surrounding marginal region 16 as well). The degree of contact may depend on the technique used to attach first layer 21 to front side 11.

[0073] The first layer 21 is preferably attached to the entire surface of the front side 11 of the workpiece 10 without any adhesive between the protective sheeting 20 and the workpiece 10. For example, attachment may be achieved by combining the first side 11 of the workpiece 10 with the first layer 21 of the protective sheeting 20 and applying heat to the first layer 21 through the second layer of the protective sheeting 20. In other words, the first layer 21 may be attached directly to the front side 11 of the workpiece without any adhesive layer therebetween, while embedding the surface structure of the front side 11 of the workpiece in the first layer 21 of the protective sheeting 20.

[0074] This prevents adhesive contamination of devices and functional layers formed on the front side 11 of the workpiece 10. Furthermore, it facilitates peeling of the workpiece 10 from the protective sheeting 20 and cleaning of the workpiece 10 (if necessary).

[0075] Nevertheless, as an alternative, the above-mentioned protective sheeting 20 may comprise an adhesive. In this case, the adhesive is arranged on the side facing the workpiece 10. The adhesive is provided on a circumferential portion of the protective sheeting 20, in particular on the entire circumferential portion of the first layer 21 facing the first front side 11 of the workpiece 10. The circumferential portion on which the adhesive is provided preferably corresponds to the peripheral limiting region 16 surrounding the (central) device region 15 of the workpiece 10.

[0076] In embodiments in which protective sheeting 20 includes adhesive disposed on the side facing workpiece 10, it is preferred that the adhesive contact peripheral limiting region 16 surrounding device region 15 of workpiece 10 with front side 11 of workpiece 10 disposed on protective sheeting 20. In other words, it is particularly preferred that the adhesive not contact device region 15 of workpiece 10.

[0077] In the case of adhesive placed in the peripheral marginal region 16 surrounding the device region 15 of the workpiece 10, any height differences that may arise due to the adhesive or adhesive layer are preferably compensated for by or embedded in the first layer 21.

[0078] Also, first layer 21 and second layer 22 are preferably attached without an adhesive layer. Nevertheless, an adhesive layer may be used to attach first layer 21 and second layer 22 to one another. Thus, the adhesive does not come into contact with first side 11 of workpiece 10. Using such an adhesive layer facilitates handling of the protective sheeting, particularly when combined with workpiece 10.

[0079] 1-6, the protective sheeting 20 may include a circumferential excess portion that extends laterally beyond the lateral dimension of the workpiece 10 to mount the workpiece 10 to a support frame 40. The support frame 40 is preferably a ring frame that may surround the workpiece 10.

[0080] The support frame 40 is attached to the protective sheeting 20, particularly to the first layer 21. The circumferential portion (layer 21) of the protective sheeting 20 is attached to the support frame 40 such that the protective sheeting 20 closes a central opening in the support frame 40, for example, the area inside the inner diameter of the ring frame.

[0081] As shown, the ring frame 40 is preferably attached to the side of the protective sheeting 20 (i.e., the first layer 21) that faces the workpiece 10. However, the ring frame 40 may also be provided on the opposite side of the protective sheeting 20.

[0082] The step of attaching the ring frame 40 to the protective sheeting 20 can be performed before or during the assembly of the protective sheeting 20 and the workpiece 10. In this way, handling of the protective sheeting 20 is facilitated, particularly when placing the protective sheeting 20 on the workpiece 10.

[0083] Furthermore, after the protective sheeting 20 is placed on the workpiece 10, the workpiece 10 can be more easily handled by the support frame 40 via the protective sheeting 20. This makes it easier to handle and transport the workpiece 10.

[0084] Any of the above-described mounting steps can be performed in a vacuum environment (i.e., in a vacuum chamber). In particular, the application of protective sheeting 20 as shown in Figure 1 is preferably performed in a vacuum during and / or after application or lamination of protective sheeting 20.

[0085] By using a vacuum (i.e., negative pressure), the protective sheeting 20 conforms to height differences (i.e., protrusions or recesses) on the front side 11 of the workpiece 10 in an enhanced manner. As a result, the protective sheeting 20 can be attached more reliably because at least fewer voids and / or air bubbles exist between the protective sheeting 20 and the first side 11 of the workpiece 10, which could otherwise create a risk of the protective sheeting 20 unintentionally separating from the workpiece 10. Thus, attachment of the protective sheeting 20 to the workpiece 10 is enhanced.

[0086] The vacuum environment also enables secure attachment of the first side 11 of the workpiece 10, particularly to its central region (e.g., corresponding to the device region 15 on the substrate of the workpiece 10), without the use of adhesives. If no adhesive is used, the protective sheeting 20 (e.g., first layer 21) can be easily and completely removed from the front side 11 of the workpiece 10, and therefore, post-processing of the workpiece to remove residual material is essentially not required. In other words, the protective sheeting 20 is not permanent (e.g., not part of a singulated device or final product) and is removed after processing the workpiece 10.

[0087] For example, the step or steps of placing protective sheeting 20 on first side 11 of workpiece 10 may be performed in a vacuum chamber as follows.

[0088] After the workpiece 10 and protective sheeting 20 are loaded into the vacuum chamber, the chamber is evacuated. If necessary, air may be supplied to the rubber membrane through an air inlet port, causing the rubber membrane to expand into the vacuum chamber and act as a pressurizing means, described in more detail below (see FIGS. 3 and 4). In this manner, the rubber membrane moves toward the workpiece 10 within the vacuum chamber, pressing the protective sheeting 20 against the first side 11 of the workpiece 10.

[0089] Alternatively or additionally, a pressure pad 35 may be used to press the protective sheeting 20 and the first side 11 of the workpiece 10 together (see Figures 3 and 4). Such a pressure pad is essentially rigid compared to the protective sheeting 20 in order to obtain a substantially flat surface on the side of the second layer 22 that contacts the pressure pad 35 during pressing.

[0090] Subsequently, the vacuum in the vacuum chamber is released, and the protective sheeting 20 is held in position on the first side 11 of the workpiece 10 by the attachment force created between the protective sheeting 20 and the workpiece 10. When the vacuum is released, atmospheric pressure can also exert a compressive force that presses the protective sheeting 20 and the workpiece 10 together, which can also support the embedding process in the first layer 21 in accordance with the present disclosure.

[0091] Additionally, a vacuum chamber can be used to apply protective sheeting 20 to first side 11 of workpiece 10 via vacuum (e.g., without applying additional pressure using pressure pad 35 or a membrane). In either case, the steps of applying heat and pressure as described above may occur after the vacuum is released or after workpiece 10, including the protective sheeting, is released from the vacuum chamber (i.e., additionally or alternatively).

[0092] 1-6 and described above may be applied to workpiece 10 in a pre-assembled state (i.e., layers 21 and 22 are assembled prior to performing the method), or may be assembled as part of the method. Accordingly, the method may include applying, with or without adhesive, a first layer 21 of protective sheeting 20 to front side 11 of workpiece 10 that substantially corresponds to peripheral limiting region 16 surrounding (central) device region 15 of workpiece 10. Next, a second layer 22 of protective sheeting 20 is applied to first layer 21, with or without an adhesive layer between first layer 21 and second layer 22. Nevertheless, it is preferred to attach second layer 22 to first layer 21 before applying the assembled protective sheeting 20 to first side 11 of workpiece 10.

[0093] In any event, application of any of the layers 21, 22 of the protective sheeting 20 is preferably performed in a vacuum (i.e., using a vacuum chamber). Additionally, the method may employ heat during and / or after any or all of the above application or lamination processes.

[0094] As shown in Figure 2, after combining the first side 11 of the workpiece 10 and the first layer 21 of the protective sheeting 20, heat is applied to the first layer 21 of the protective sheeting 20 through the second layer 22 using a heating means 32. The heating means 32 is therefore located on the side of the second layer 22 of the protective sheeting. The heating means 32 may be included in the workpiece support 30 (see Figures 2 and 3) or the pressure pad (see Figure 4).

[0095] The heating surface 36 of the heating means 32 is preferably in contact with the second layer 22. Heat is therefore transferred from the heating means 32 through the second layer 22 to the first layer 21 of the protective sheeting, preferably to the side or surface of the first layer 21 facing the first side 11 of the workpiece 10.

[0096] The heat of the heating means 32 transferred to the first layer 21 is controlled to soften the first layer 21. In particular, the heat is configured to switch the first layer 21 from a solid state to a soft state, such that the first layer undergoes plastic deformation, or the material of the first layer can be displaced from an area of high compression to an area of low compression. A fluid state in this context means that the material of the first layer 21 of the protective sheeting 20 can flow to such an extent that it can embed the surface structure of the first side 11 of the workpiece 10. In other words, on the first side 11, protrusions are embedded and recesses are filled by the material of the first layer 21 of the protective sheeting 20.

[0097] This embedding process is preferably supported by heating the first layer 21 of the protective sheeting 20 to at least its glass transition temperature, preferably below its melting temperature, to avoid stickiness of the first layer (i.e., the first layer has adhesive properties that allow it to adhere to the first side 11 of the workpiece 10).

[0098] First layer 21 is specifically heated to a temperature that softens the material sufficiently to compensate for irregularities, but does not cause the material to become so tacky or adhesive that it would adhere residue to first side 11 upon removal of protective sheeting 20. Nevertheless, first layer 21 may be heated above the melting temperature of its material if this does not result in such adverse adhesive properties.

[0099] For example, when using the above-mentioned materials for the first layer 21 (particularly polyolefin or polypropylene), a temperature of at least 60° C. to 160° C., particularly 100° C. to 160° C., is preferred. At this temperature, the first layer 21 becomes soft enough to fill in any height differences on the first side 11 of the workpiece 10, while the second layer 22 can essentially maintain its initial flatness.

[0100] In this regard, the heat applied to first layer 21 via heating surface 36 preferably raises the temperature of second layer 22 of protective sheeting 20 to at least 30° C., 40° C., 50° C., 60° C., or 70° C. below the melting temperature and preferably above the glass transition temperature of the material of first layer 21 of protective sheeting 20. In this way, second layer 22 can more easily maintain a flat support surface.

[0101] Nevertheless, it may be 5° C., 10° C., 15° C., 20° C., or 25° C. below the glass transition temperature. In particular in such cases, the sheet-like shape of second layer 22 of protective sheeting 20 may remain essentially unchanged.

[0102] Preferably, the second layer 22 or the side of the second layer 22 of the protective sheeting 20 is held under suction on the heating surface 36 of the heating means 32. Thus, the heating surface 36 may be an at least partially porous surface or may have suction grooves for creating a negative pressure to hold the protective sheeting 20 under suction.

[0103] The heat treatment is selected in particular so that the surface structure of the first side 11 of the workpiece 10 (i.e., the volume of the protrusions and / or recesses of the functional layer of the workpiece 10) is embedded by at least 80%, 85%, 90%, 95%, or 98%.

[0104] The temperature of the first layer 21 of protective sheeting is preferably maintained for 15 to 180 seconds. While shorter times are preferred from a productivity standpoint, it should also be considered that longer times allow for reduced stresses acting on the first side 11 of the workpiece 10 during heating (and in this case, during application of pressure, as discussed further below). Longer times also allow for enhanced embedding and application of pressure with less risk of damaging the workpiece 10.

[0105] The heating protocol for heating the first layer 21 through the second layer 22 of the protective sheeting is preferably a predetermined heating protocol, in other words, the heating process may be determined in advance by means of experiments, which is facilitated by the heating process being carried out from the side of the protective sheeting 20.

[0106] The degree of embedding as described above can be selected to determine and evaluate the parameters for the heating protocol in these experiments. For example, one possibility to determine whether the embedding is sufficient or not can be by optically inspecting (e.g., using a microscope or camera) the front side 11 of the workpiece 10 for bubbles, particularly from the side of the second layer 22.

[0107] Alternatively or additionally, the degree of cracking, fracture, or defective devices (especially after mechanical processing) can be used as a parameter to determine the heating protocol. A predetermined heating protocol has the advantage of high productivity and uncomplicated production management, since real-time temperature control is not required (although it can still be used).

[0108] The heat treatment is preferably carried out under vacuum conditions, as described above with respect to the application of the protective sheeting 20.

[0109] 3 and 4, a pressure applying means can be used to apply pressure to strengthen the embedding of the first side 11 of the workpiece 10 into the first layer 21 of the protective sheeting 20. The application of pressure by the pressure applying means is preferably carried out during and / or after the above-mentioned heating. In particular, when applying pressure, the above-mentioned heating time is preferably longer than 30 seconds, more preferably longer than 60 seconds, in order to reduce stress peaks during the embedding process.

[0110] In contrast to heating the side of the second layer 22 of the protective sheeting 20, the pressure means can apply pressure from either side 11, 12 of the workpiece 10 (see Figures 3 and 4) or both sides 12.

[0111] 3, the pressure means applies pressure from the second side or backside 12 of the workpiece 10 using a pressure pad 35. The heating means 32 is therefore positioned on the opposite side, i.e., on the front side 11 of the workpiece 10 where the protective sheeting 20 is located.

[0112] In this embodiment, the protective sheeting is placed on a workpiece support 30 (e.g., a chuck table) that includes a heating means 32. As mentioned above, the side of the heating means 32 that includes a heating surface 36 (which also acts as the holding surface 31 of the workpiece support 30 in FIG. 3 ) is preferably configured to hold the second layer 22 of the protective sheeting 20 under suction.

[0113] In Fig. 4, the pressure means applies pressure from the first or front side 11 of the workpiece 10. The pressure is therefore applied through the protective sheeting 20. The pressure means and the heating means 32 are therefore both located at the side of the first side 11 of the workpiece 10. In Fig. 4, they are contained in a pressure pad 35. In particular, by means of the heating means 32, the pressure pad 35 may be configured to hold the protective sheeting 20 under suction. In the exemplary embodiment of Fig. 4, the second side 12 of the workpiece 10 is placed on a holding surface 31 of a workpiece support 30 in the form of a chuck table.

[0114] The pressure pad 35 may be replaced by the above-mentioned membrane or the like. Preferably, the pressure means has a rigid flat surface. Such a rigid flat surface is advantageous for achieving a reinforced flat support surface on the side of the second layer 22 of the protective sheeting 20, particularly when the second layer 22 of the protective sheeting is a sheet-like film.

[0115] The use of heat, particularly in combination with pressure, to attach protective sheeting 20 can cause first layer 21 to conform to the surface structure of first side 11 of workpiece 10 (i.e., an interlocking relationship between first layer 21 and the surface structure of first side 11 of workpiece 10). Without wishing to be bound by theory, it is believed that this conformance is achieved by the material of first layer 21 flowing or deforming around and into protrusions and recesses, respectively, of the surface structure of the first side.

[0116] 5, the preparation unit may also include a camera 50 for inspecting the first side 11 of the workpiece 10 and / or the protective sheeting 20 attached to the first side 11 of the workpiece 10. The camera 50 is positioned on the side of the protective sheeting 20, and the workpiece 10 is supported on a workpiece support (not shown) opposite the camera 50.

[0117] The camera 50 may be used to detect air bubbles (e.g., to determine the extent of embedding by volume or surface). In this configuration, a visible light camera can be used if the protective sheeting is transparent to the corresponding wavelength. Alternatively, an infrared camera may be used to inspect the first side 11 of the workpiece 10.

[0118] Another embodiment including a camera 150 is illustrated in FIG. 6 , where the camera 150 may be used to assist in the inspection and / or processing of the workpiece 10. As shown schematically, the workpiece 10 is supported on a workpiece support 30 on its first side 11, i.e., with a protective sheeting disposed therebetween. As with the exemplary embodiment shown in FIG. 5 , the camera 150 may be an infrared camera or a visible light camera. In the latter case, the workpiece support 30 and the protective sheeting 20 (e.g., made of a transparent material such as glass) are preferably semi-transparent to visible light wavelengths.

[0119] In general, the material between the camera 50, 150 and the object being viewed (particularly the first side 11 of the workpiece 10) should be transparent to the wavelengths that the camera 50, 150 can detect.

[0120] In FIG. 6 , a camera may be used to inspect the embedding results, as described above. Additionally or alternatively, a camera may be used to assist in the processing of workpiece 10. In FIG. 6 , this is illustrated schematically by dicing blade 60. For example, camera 150 may detect intersecting parting lines or streets or cut alignment marks formed on first side 11 of workpiece 10 to enable proper positioning of dicing blade 60 for separating workpiece 10 into single device chips. Thus, FIG. 6 illustrates an example of mechanically processing workpiece 10 with enhanced support provided by a protective sheeting pre-attached to first side 11 of workpiece 10.

[0121] In further embodiments, protective sheeting 20 may also include one or more additional layers. The additional layers of protective sheeting 20 may be formed of the same or different materials as the layers of protective sheeting 20. As previously mentioned, the additional layers of protective sheeting 30 may be adhesive layers.

[0122] The thickness of the protective sheeting 20 is 100 to 500 μm, preferably 100 to 300 μm, and more preferably 150 to 200 μm. In particular, the first layer 21 of the protective sheeting 20 has a thickness greater than the difference between the highest point and the deepest point of the surface structure placed on the first side 11 of the workpiece 10.

[0123] Reference sign

[0124] 1,101…preparatory units, 10...workpiece, 11...first side or front side, 12...second side or back side, 13...notch, 14... Street, 15...Device area, 16...peripheral marginal area, 20...protective sheeting, 21...first layer, 22...second layer, 30...Workpiece support (e.g., chuck table) 31...holding surface, 32...Heating means, 35...Pressure pad, 36...heating surface, 40...support frame, 50,150...camera, 60...Dicing blade.

Claims

1. A method of preparing a workpiece (10) for processing, comprising: providing the workpiece (10); providing a protective sheeting (20) comprising at least a first layer (21) and a second layer (22), said second layer (22) being formed of a material having a higher glass transition temperature or melting temperature than said first layer (21); combining a first side (11) of the workpiece (10) with the first layer (21) of the protective sheeting (20); applying heat to the first layer (21) of the protective sheeting (20) through the second layer (22) of the protective sheeting; A method comprising:

2. 2. The method of claim 1, wherein when heat is applied to the first layer (21) of the protective sheeting (20), the first side (11) of the workpiece (10) faces a heating means (32) and the first layer (21) of the protective sheeting (20) is preferably in contact with the first side (11) of the workpiece (10).

3. The method comprises: further comprising the step of placing the second layer (22) of the protective sheeting (20) over the heating means (32); 3. The method of claim 2, wherein the heating means is configured to apply heat to the first layer (21) of the protective sheeting (20) through the second layer (22) of the protective sheeting (20), the second layer (22) preferably being in contact with the heating means (32).

4. 4. The method of claim 3, wherein the second layer (22) of the protective sheeting (20) is held on the heating means (32) under suction.

5. The method according to any one of claims 1 to 3, wherein the first layer (21) and the second layer (22) are formed from polymeric materials, and the polymeric materials of the first layer and the second layer are different.

6. 6. The method of claim 5, wherein the first layer (21) is made of polyolefin or polypropylene and / or the second layer (22) is made of polyethylene terephthalate.

7. 7. The method according to claim 1, wherein a surface structure is formed on a first side (11) of the workpiece (10), and when heat is applied to the first layer (21) of the protective sheeting (20), the first layer (21) is softened so that the surface structure is embedded in the first layer (21), and when heat is applied to the protective sheeting (20), preferably only the first layer (21) is softened.

8. 8. The method according to any one of claims 1 to 7, wherein the first layer (21) of the protective sheeting (20) is heated to a temperature above the glass transition or melting temperature of the first layer (21) and below the glass transition or melting temperature of the second layer (22).

9. 9. The method according to claim 1, wherein the step of placing the first side (11) of the workpiece (10) on the first layer (21) of the protective sheeting (20) and / or the step of applying heat to the first layer (21) of the protective sheeting (20) are carried out essentially under vacuum conditions, preferably in a vacuum chamber.

10. 10. The method according to any one of claims 1 to 9, wherein the workpiece (10) and the protective sheeting (20) are pressed together, preferably by applying a pressure load via the second layer (22) of the protective sheeting (20) and / or the workpiece (10), during or after applying heat to the first layer (21) through the second layer (22) of the protective sheeting (20).

11. 11. The method according to any one of claims 1 to 10, wherein the second layer (22), in particular the side of the second layer (22) opposite to the side facing the first layer (21), has a substantially flat shape, and the shape of the second layer (22) remains substantially unchanged when heat is applied to the first layer (21) of the protective sheeting (20).

12. A preparation unit (1; 101) for preparing a workpiece (10), The preparation unit is configured to attach a protective sheeting (20) to the workpiece (10), the protective sheeting (20) comprising at least a first layer (21) arranged on the workpiece side and a second layer (22) arranged on the side opposite to the workpiece side, and the workpiece preparation unit comprises: a workpiece support (30) including a holding surface (31) for holding a workpiece (10) via said second layer (22); a heating means (32); a control unit configured to control the heating means (32) such that the first layer (21) is heated via the second layer (22) according to a predetermined heating protocol; A preparation unit (1; 101) comprising:

13. 13. A preparation unit (1) according to claim 12, further comprising pressure means for applying a pressure load to said first layer (21).

14. 14. A preparation unit (1) according to claim 12 or 13, further comprising a camera (50) arranged to inspect the exposed surface of the second layer (22) of protective sheeting (20) attached to the workpiece (10).

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