Method for creating a vacuum grip for a semiconductor workpiece, and vacuum grip

Abstract

The present invention relates to a method for producing a vacuum gripper (100) for a semiconductor workpiece, in which the vacuum gripper (100) is produced from at least one base material by an additive construction method, and to a vacuum gripper (100) of this type.

Description

[Technical field]

[0001] The present invention relates to a method for creating a vacuum grip for a semiconductor workpiece and to such a vacuum grip for a semiconductor workpiece. [Background technology]

[0002] prior art Vacuum grippers, often referred to as "chucks" or suction grippers or vacuum suction grippers, are used in the creation and processing of semiconductor workpieces, such as wafers of silicon or other semiconductor materials, to allow these semiconductor workpieces to be secured and / or transported and / or held in a particular alignment during various process steps. At the same time, however, the semiconductor workpieces are also processed as they are placed or held on the vacuum gripper. This includes, for example, polishing, etching, cleaning, sizing, and grinding the surface.

[0003] Such vacuum grippers for semiconductor workpieces can be manufactured as cast, welded, and machined devices, but as has been shown, these manufacturing processes only allow for limited realization of the shaping and functional features of the vacuum gripper.

[0004] Document US 2019 / 272982 A1 thus discloses a method for producing a vacuum gripper for a semiconductor workpiece, in which the vacuum gripper is produced by an additive build-up process from at least one base material.

[0005] Document US2019 / 080954 A1 discloses an apparatus for holding semiconductor wafers using a vacuum.

[0006] Document US2017 / 345692 A1 also discloses an apparatus for holding semiconductor wafers using a vacuum, which apparatus is produced by 3D printing. Summary of the Invention [Problem to be solved by the invention]

[0007] Thus, a need exists for improved vacuum grippers for semiconductor workpieces, and / or their creation.

[0008] Disclosure of the Invention According to the invention a method is proposed for producing an apparatus suitable for holding a semiconductor workpiece by means of a vacuum. Advantageous embodiments are the subject of the dependent claims and of the following description. [Means for solving the problem]

[0009] The present invention relates to the creation of a vacuum gripper for semiconductor workpieces, such as silicon wafers, and thus also to the structural design thereof. As already mentioned at the beginning, a vacuum gripper is a device that can hold a semiconductor workpiece, in particular a wafer, firmly. For this purpose, as the name already indicates, a vacuum is created, by which the semiconductor workpiece can be sucked, so to speak, onto the vacuum gripper.

[0010] Such a vacuum gripper preferably has a (at least substantially) flat area on which the semiconductor workpiece can be placed, one or more suction openings and one or more channels connected thereto. In that case, these channels should be connected to the suction openings accordingly. Also, the suction openings should be provided as far as possible in the region of the flat area, so that the semiconductor workpiece can be positioned on them. Furthermore, the channels should then be connectable to or connected to a negative pressure source, in order to be able to create a negative pressure or vacuum in the channels. The flat area may for example have a round shape, so that a typical wafer can be placed on it. The diameter of this round area or of the entire vacuum gripper may then be for example 300 mm, or even more.

[0011] In the proposed method, the vacuum gripper is produced in or with a particularly predefined shape from at least one base material by an additive deposition or production process (which may in particular be known as 3D printing). The base materials are thus for example joined together layer by layer until the final desired predefined shape is produced. In this respect, the vacuum gripper is preferably designed such that it has at least a substantially flat area, one or more suction openings and one or more channels connected thereto, as already mentioned above as an advantageous embodiment of the vacuum gripper.

[0012] The vacuum gripper is preferably further designed such that it includes a reinforcing structure, in particular formed from the base material. The creation of such a reinforcing structure, for example a strut, thickening, etc., may be possible in a particularly simple manner and in or with any more or less desired shape by additive deposition processes or by 3D printing. However, the reinforcing structure may also be formed from another material, for example having a material hardness different from the base material.

[0013] At least one additive capable of adapting the material hardness is preferably added to the base material. In this way, for example for the formation of a reinforcing structure, it is possible to influence the mechanical properties of the vacuum gripping part in a targeted manner, in particular selectively at specific points or areas, as well as the reinforcing structure.

[0014] Likewise, it is advantageous if the predefined areas of the vacuum gripper are produced by an additive deposition process from a material different from the base material. In this way it is possible to create e.g. flexible areas that act as seals, for example.

[0015] In this context, it is likewise preferred if a layer with a material having a lower or lesser hardness than the base material is formed in the area or side of the vacuum gripper that is to face the semiconductor workpiece. This layer may then include a flat area. This layer then serves to avoid possible damage to the semiconductor workpiece and may thus serve as a replacement for what is known as a "chuck pad". Such a "chuck pad" is conventionally a piece of a kind of fabric or cloth, also made of polyurethane where appropriate, that is placed on a hard surface in a conventional vacuum gripper in order to avoid damage to the semiconductor workpiece. Such a chuck pad is no longer necessary with the design of the described layer.

[0016] Then, i.e. after the vacuum gripper has been produced with a predefined shape from the base material or optionally from further materials, it is possible to apply a coating material for protection against chemicals either completely or in predefined areas of the surface of the (thus deposited) body. That is to say, the vacuum gripper is rendered resistant to chemicals by the coating (which acts as a protective layer) and the surface roughness is reduced. In this respect, the relevant areas of the surface to which the coating material is applied are in particular areas which will come into contact with the corresponding medium or chemical during later use and therefore should be protected. This concerns in particular the upper side (in particular the already mentioned flat area) which serves to suck the semiconductor workpiece. In this respect, preferred coating materials are polytetrafluoroethylene, PTFE, perfluoroalkoxy polymers, PFA, polyvinylidene fluoride, PVDF, DLC (diamond-like carbon) or silicon carbide.

[0017] The reason for the preferred use of such coatings is that for parts produced by additive deposition processes such as 3D printing, and for the mentioned vacuum gripper, which (possibly) consists (only) of a base material depending on the desired application, the roughness of the surface can be too strongly pronounced, i.e. the surface generally has a roughness that is too great for the desired use, resulting in organic and inorganic contaminants (produced, for example, during polishing of the semiconductor workpiece held by the vacuum gripper) being deposited in and on the surface, which under certain circumstances adversely affects the quality of the semiconductor workpiece to be processed.

[0018] However, a coating, for example with PTFE, on the relevant surfaces of a vacuum gripper produced by an additive deposition process now makes it possible to combine the positive properties of a conventionally produced vacuum gripper (i.e. in particular resistance to chemicals) with the positive properties of a vacuum gripper produced by an additive deposition process for silicon wafers (i.e. in particular free forming).

[0019] Since in the case of conventional coating processes the vacuum gripper created by the additive deposition process is expected to be subjected to high thermal loads and, as a result, to deformation, it is possible to use low temperature coating processes in targeted combination with additive deposition processes. High purity coatings (i.e., particularly high purity coatings) which are necessary for processes in the case of semiconductor workpieces are conventionally applied to surfaces at high temperatures.

[0020] The low-temperature coating process, used in a targeted manner and preferably at temperatures below 150°C, allows the application of high-purity coatings even to less thermally stable surfaces of 3D printed parts, such as vacuum grippers, and thus brings together the advantages of free shaping, targeted positioning of suction openings, chemical and physical properties. For example, the material PA3200GF has a heat distortion temperature of up to 157°C according to ISO75-1 / -2 (at a pressure of 0.45 MPa and in the X-direction). A comparable situation applies for the preferred base material, which in particular comprises polyamide filled with glass beads. Above this temperature, the plastic contour typically collapses under its own weight. For example, PTFE coatings are generally molded on top of a furnace and sintered in the furnace at temperatures of about 220°C to 420°C. A low-temperature sintering process, typically at 100°C for example and lasting a relatively long time, has made it possible to achieve a situation in which the 3D printed vacuum grippers for silicon wafers become resistant to chemicals and dirt.

[0021] The surface roughness of the vacuum gripper produced by the additive deposition process can be reduced by the low-temperature coating, with the Rz and Ra values ​​(specifying the roughness) typically being reduced by about 70% with respect to the corresponding values ​​of the vacuum gripper without the low-temperature coating. This also contributes to the fact that particles of the liquid on the vacuum gripper or other organic or inorganic components adhere to the surface (of the vacuum gripper) to a much lesser extent and can thus be removed in a much easier and targeted manner.

[0022] By additive deposition processes or by 3D printing, it is possible to produce vacuum grippers that are optimized in various respects compared to conventional production processes. Improved shaping, i.e. the shapes that can actually be produced, allows optimal shapes to be achieved better than with conventional production processes, and actively effective suction openings, for example in the form of suction funnels, can be adapted to the respective desired application in contrast to conventionally produced vacuum grippers. Free shaping allows the required holding force created by the vacuum or negative pressure to be set in a particularly precise manner. The areas (channels) that are to be evacuated can be kept as small as possible by application-optimized variable shaping, which contributes to a faster build-up and fall of the holding force, thus accelerating the transfer of, for example, semiconductor workpieces.

[0023] Compared to conventional manufacturing processes, which are limited by the use of manufacturing tools that can create thin and deep holes with only limited length, the additive production process makes it possible to produce, for example, a vacuum tank directly in the vacuum gripper, for example as a result of a locally relatively large cross-section of the channels in the vacuum gripper. As a result, the vacuum gripper is less sensitive to temporary vacuum leaks, and the risk of damage to the semiconductor workpiece is reduced if the holding force is reduced during surface processing. The individual design and arrangement of the suction openings and suction channels makes it possible, compared to conventional production processes, to set the holding force for the semiconductor workpiece in a targeted manner, for example so that a higher holding force is set in the peripheral area during processing than in other areas (which entails a specific action of the force on the workpiece edge).

[0024] The additive production process allows to select the number of suction openings and channels in a targeted manner depending on the area of ​​the vacuum gripper, thus increasing the number of suction openings and channels in the peripheral area, for example, compared to conventionally produced vacuum grippers, so that the medium, for example abrasive, that is sucked during the processing of the semiconductor workpiece can be extracted by suction more quickly, thus avoiding cases of peripheral corrosion.

[0025] The shaping of the suction openings themselves, for example in the peripheral region, which can be designed in a targeted manner and adapted to the respective processing process of the semiconductor workpiece, is also made possible with the proposed method in comparison with conventional production processes. In the case of processes for processing the edge of the semiconductor workpiece, for example edge grinding, as a result of the action of forces on the edge, the process medium also typically enters the region between the vacuum gripper and the semiconductor workpiece. The suction openings, designed as annular channels on the upper side of the vacuum gripper, for example, allow for a fast exit of the entering medium and, as a result, avoid undesired chemical or physical reactions of the medium with the surface of the semiconductor workpiece.

[0026] The use of additive deposition processes, in comparison with conventional production processes of the vacuum gripper, allows for example even flexible seals, as already mentioned, to be directly integrated or subsequently attached. For example, 3D printed sealing elements, in comparison with conventional seals, can be precisely adapted to the processing process for the semiconductor workpiece and thus prevent the process medium from penetrating the edge area between the support area and the semiconductor workpiece, for example during an edge grinding process. The use of such a vacuum gripper, produced by additive deposition processes and with integrated or separate seals, also produced by additive deposition processes, allows for the seal to be variably and more quickly adapted to modified processing processes for the semiconductor workpiece than conventional production processes.

[0027] The targeted manufacturing by additive deposition process makes it possible to realize suction openings with any desired shape, in comparison with conventional production processes. As a result, it is possible to avoid, for example, sharp edge transitions, for example in the radial direction, instead of the processed edge of the semiconductor workpiece, with the suction openings and the support area being formed in any desired manner. In the case of conventionally produced vacuum grippers, the sharp edge transitions are a significant cause of impressions, scratches or other damage to the surface of the semiconductor workpiece, because as a result of the vacuum evacuation, the surface is pressed against the support area, and the sharp edge transitions create impressions (known as "chuck marks") on the semiconductor workpiece or wafer due to the high holding force required, for example, during edge polishing.

[0028] In comparison with a vacuum gripper conventionally produced, for example, by a machining process, it is possible by the additive deposition process to realize, for example, optimized channels or channel guides and suction openings. This contributes to maintaining a sufficient holding force between the vacuum gripper and the semiconductor workpiece in the case of time-limited vacuum leaks, which are produced, for example, due to the lifting of the edge of the semiconductor workpiece and the grinding forces. Furthermore, a (as) homogeneous distribution of the forces acting during the process is achieved by the variable arrangement of active holding elements (i.e. suction openings) on the upper side or holding area of ​​the vacuum gripper, so that, while keeping the system power the same, the load experienced by the substrate is kept low and the risk of the semiconductor workpiece being damaged (wafer breakage) is considerably reduced.

[0029] As already mentioned, providing a layer of material having a lower hardness than the base material makes it possible to dispense with the use of what is known as a "chuck pad". If such a layer is not provided and / or if the intention is nevertheless to use a "chuck pad", its production can be simplified as well. The reason for this is that in the case of "chuck pads" for conventional vacuum grippers, an annular cutout is generally necessary in order to be able to expose the suction openings provided in the vacuum gripper. The considerably more variable design of the suction openings in the vacuum gripper produced by the additive deposition process accordingly also makes it possible to keep the cutouts in the "chuck pad" simpler, for example in the form of a circular cutout. In addition, it is also conceivable to produce the "chuck pad" itself by the additive deposition process.

[0030] The additive deposition process or 3D printing allows freedom in terms of the number of items, an optimized use of materials and lower tool costs, especially compared to the casting or machining processes used up to now. As a result, the production costs of the vacuum gripper are considerably lower than in conventional production processes. For example, a modification of the underlying 3D CAD data for controlling the 3D printing may be sufficient to generate or print a modified design of the vacuum gripper. And, additional instances of tool manufacturing, such as in conventional production processes, for example casting models and special machining heads, are not necessary.

[0031] As already mentioned, additive deposition processes or 3D printing allow free shaping and thus also targeted mass distribution of the material or base material used for defined avoidance of vibrations that may be caused by imbalances. For example, by using honeycomb structures, mass-reducing struts instead of solid materials, and FEM (finite element method)-generated designs optimized for the respective application, a reduction in the use of material is also achieved while the mechanical stiffness remains the same. Furthermore, the use of fillers for targeted setting of mechanical properties can be taken into account. In this context, fiber proportions such as, for example, carbon fiber, glass fiber, or ceramic fiber can preferably be used for targeted setting of stiffness, which in the case of additive deposition processes can even differ within the vacuum gripper. In this way, the vacuum gripper can be designed as being more wear-resistant at the mechanical fastening points than at the periphery, for example.

[0032] Also as already mentioned, additives can be used for targeted adaptation of the material hardness, which can also be variably set in the case of additive deposition processes, so that, for example, certain areas of the vacuum gripper can be generated as flexible, for example as a seal, and other areas can be generated as stronger and harder, for example.

[0033] In comparison with conventional production processes, in the case of additive deposition processes or 3D printing, different materials can be combined without joining techniques, so that the required properties defined for the respective application can be realized. This preferably makes it possible to obtain a mechanism of action by a combination of materials that in the case of conventionally produced vacuum grippers can only be realized by additional actuators. In the case of 3D printing processes, for example, the peripheral area of ​​the vacuum gripper can be produced with elastic and resilient materials, which better support the peripheral area during grinding of the edges.

[0034] In addition, application-specific smoothing of specific areas, such as the surface of the vacuum gripper, can be preferably obtained by specific grinding processes, especially by ultrasonics and grinding additives, which advantageously reduce the surface roughness on all surfaces of the vacuum gripper and also the internal channels, resulting in reduced adhesion of media, such as abrasives, on the surfaces and thus avoiding damage to the semiconductor workpiece.

[0035] The invention also relates to a vacuum gripper for a semiconductor workpiece, which is produced from at least a base material by an additive deposition process, in particular in a predefined shape or with said shape. In this respect, the vacuum gripper advantageously has at least a substantially flat area on which the semiconductor workpiece can be placed, one or more suction openings and one or more channels connected thereto. In this case, such a vacuum gripper is preferably produced by a method according to the invention. Regarding further preferred embodiments and advantages, in order to avoid repetition, reference should be made to the above description of the method which applies correspondingly here.

[0036] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

[0037] It will be understood that the features identified above, and those to be further elucidated below, may be used not only in the specific combinations indicated, but also in other combinations, or alone, without departing from the scope of the present invention.

[0038] The invention is illustrated diagrammatically in the drawings by way of an exemplary embodiment and will be explained below with reference to the drawings. [Brief description of the drawings]

[0039] [Figure 1] FIG. 2 is a schematic diagram of the steps in the method according to the invention in a preferred embodiment. [Diagram 2] FIG. 2 is a schematic diagram of a vacuum gripper according to the present invention in a preferred embodiment. [Diagram 3] FIG. 3 shows the vacuum gripper from FIG. 2 in cross-sectional view. [Figure 4] FIG. 4 shows an enlarged detail from FIG. [Diagram 5] FIG. 2 is a schematic diagram of a vacuum gripper according to the present invention in a further preferred embodiment. [Figure 6] FIG. 2 is a schematic diagram of a vacuum gripper according to the present invention in a further preferred embodiment. [Figure 7] 7 shows the vacuum gripper from FIG. 6 in a different view. FIG. [Figure 8] 8A and 8B are diagrams showing different views of the vacuum gripper shown in FIG. 7. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] 1 shows a schematic diagram of the steps in the method according to the invention in a preferred embodiment. For this purpose, firstly shown in image (a) as a rough schematic diagram is an apparatus 150 for the additive deposition process, for example a 3D printer, which has a print head 155 to which a base material 160 is supplied. Optionally, additives 161 (in that case used in particular apart from the base material) and / or further materials can also be supplied to the print head 155. The print head 155 then first applies to the carrier 151 a first layer 101 of the vacuum gripper to be generated.

[0041] Further layers are applied in the further course of the procedure, in particular by applying each new layer to each preceding layer. By way of example, image (b) shows a further layer 102 applied to layer 101, and image (c) shows a further layer 103 applied to layer 102.

[0042] Thus, the vacuum gripper 100 is produced from the base material by an additive deposition process in a desired or predefined shape as shown in the rough schematic diagram in image (d). For a more detailed view, reference should now be made to the following figures. As also shown in image (d), a coating material 180 is applied, for example, to the upper side of the vacuum gripper 100 by an application tool 175 to which the coating material 180 is supplied, for example, from a tank 170.

[0043] The thus coated vacuum gripper 100 is then dried and in particular sintered, for example in an oven 190 as shown in image (e), for a given time within a given temperature range below the heat distortion temperature of the base material 160, for example at 150° C. This results in a finished coated vacuum gripper, which is therefore also resistant to chemicals.

[0044] Figure 2 shows a schematic diagram of a vacuum gripper 100 according to the invention in a preferred embodiment, for example as may be produced by the method shown in and described with respect to Figure 1. Figure 2 shows a top perspective view of the vacuum gripper 100, while Figure 3 shows a matching cross-sectional view. The axis of symmetry A shown in Figure 3 passes through the central opening of the view in Figure 2. Figures 2 and 3 are intended to be described collectively below.

[0045] The vacuum gripper 100 has a rounded shape relative to an axis of symmetry A, with an upper side having or designed as at least a substantially flat area 110. During use of the vacuum gripper 100, a semiconductor workpiece, such as a wafer, is placed indirectly or directly on this flat area 110. In this respect, reference should also be made to FIG.

[0046] A number of suction openings 120 are introduced on the upper side of the vacuum gripper 100. In Fig. 2 a particularly uniform distribution of these suction openings 120 can be seen on the upper side or in the flat area 110, while Fig. 3 shows the arrangement within the vacuum gripper. Starting from the upper side, the suction openings 120 narrow approximately conically towards the inside of the vacuum gripper 100 and then open into a channel 130. Each of the suction openings 120 may be attached to the channel 130, in particular the openings located on a radial line are attached to a common channel 130. In this respect, reference should also be made to Fig. 7.

[0047] The channel 130 and all further channels open into an opening 135 located centrally or on the axis of symmetry A, opposite the upper or flat area 110, where, for example, a suitable device can then be arranged to generate a negative pressure or vacuum which propagates through the channel 130 to the suction opening 120. In this way, a negative pressure or vacuum can be created at the suction opening 120, so that a wafer resting on the flat area 110 is sucked onto the flat area 110 or the vacuum gripper 100 and thus held in place.

[0048] Figure 4 shows an enlarged detail of the vacuum gripper 100 from Figure 3. On the rightmost side of the figure, i.e. based on the example of a suction opening 120 arranged radially outwards, a transition 122 of the suction opening 120 at the transition to the flat area 110 is shown. Here it can be seen that said transition is not a sharp edge, as in conventionally produced vacuum grippers, but rather has a rounded design or is designed as a radius. These can be produced particularly well or simply by additive deposition processes, leading to the fact that no damage occurs to the wafers resting against them, or that damage to the wafers resting against them can at least be very significantly reduced.

[0049] Figure 5 shows a schematic view of a vacuum gripper 100' according to the invention in a further preferred embodiment. The vacuum gripper 100' basically corresponds to the vacuum gripper 100 according to figures 2, 3 and 4. The view shown here corresponds to the view shown in figure 4.

[0050] Here it can be seen that a seal 140 is introduced at the radially outer end of the vacuum gripper 100'. Said seal is particularly flexible and can, for example, extend over one or more portions of the circumference of the vacuum gripper. The seal 140 can, for example, also be produced by an additive deposition process, in which case preferably another material is used as the base material.

[0051] Furthermore, a pad 155, or what is known as a "chuck pad", on which a semiconductor workpiece 150 in the form of a wafer is then placed, is applied or placed on the upper or flat area 110. Suction openings and for example suitable openings in the pad 155 (one of which is visible in the area of ​​the suction opening 120) allow the wafer 150 to be sucked together with the pad 155. It can also be seen that the wafer 150 is in contact with the seal 140, so that a seal is created and thus the negative pressure can produce a greater effect.

[0052] 6 shows a schematic diagram of a vacuum gripper 100'' according to the present invention in a further preferred embodiment. The vacuum gripper 100'' basically corresponds to the vacuum gripper 100' as shown for example in FIG. 5, but on the side of the vacuum gripper that is to face the wafer 150, a layer 105 is formed, which acts as a "chuck pad". Therefore, no separate "chuck pad" is required.

[0053] Figure 7 shows a schematic diagram of a vacuum gripper 100''' according to the invention in a further preferred embodiment, in particular in a perspective view equivalent to the view in Figure 2. In this respect, the vacuum gripper 100'' basically corresponds to the vacuum gripper 100 according to Figures 2, 3 and 4, but, as can be seen from a comparison with Figure 2, more suction openings 120 are provided. This shows that the suction openings 120 can be provided as required, for example in order to distribute the contact pressure created by the negative pressure at the suction openings as uniformly as possible on the wafer or its surface area.

[0054] Figure 8 shows the vacuum gripper 100''' from Figure 7 in a different view, specifically in a section perpendicular to the axis of symmetry (located in the same way as in the vacuum gripper according to Figure 2). In this figure, shown as an example are several channels 130 extending radially in a star shape and coinciding in the center. Each of the suction openings, for example as visible in Figure 7, can be connected by these channels 130.

Claims

1. 1. A method for producing an apparatus (100, 100', 100'', 100''') suitable for holding a semiconductor workpiece by vacuum, comprising: In the method, the device (100) is produced by 3D printing from at least one base material (160); The apparatus (100, 100', 100'', 100''') is designed such that it has at least a flat area (110) on which a semiconductor workpiece (150) can be placed, one or more suction openings (120) and one or more channels (130) connected thereto; The apparatus (100', 100'') is designed such that it has one or more flexible seals that can be brought into contact with a semiconductor workpiece (150) that is to be placed on the apparatus; The device (100, 100', 100', 100'''') is designed such that it includes a reinforcing structure formed from the base material (160); The apparatus (100''') is designed with a layer (105) of material having a lower hardness than the base material (160) formed on a side that is to face the semiconductor workpiece (150).

2. The method of claim 1 , wherein the predefined regions of the device (100, 100', 100'', 100''') are produced by 3D printing from a material different from the base material (160).

3. The method of claim 1, wherein the coating material (180) is applied at a temperature below 150°C by a low temperature coating process or a low temperature sintering process.

4. The method of any one of claims 1 to 3, wherein the device (100, 100', 100'', 100''') is lubricated, at least in predetermined areas, using ultrasound and using a grinding additive.

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