Carrier for edge passivation

Abstract

The present invention relates in general to a carrier for the edge passivation of semiconductor elements and, specifically, to a storage insert for receiving a stack of multiple wafers or semiconductor elements, to a carrier for a plurality of such storage inserts and to a method for populating such a carrier.

Description

[0001] CARRIER FOR EDGE PASSIVATION

[0002] The present invention relates generally to a carrier for the edge passivation of semiconductor components and, more specifically, to a storage insert for receiving a stack of a plurality of wafers or semiconductor components, a carrier for a plurality of such storage inserts and a method for populating such a carrier.

[0003] For example, it is known from DE 10 2018 123485 B4 that it can be advantageous to passivate the cut edges of semiconductor components or wafers. In order to provide these cut surfaces or cut edges with an interface passivation layer, conventional systems for applying passivation layers require the semiconductor components or wafers to be vertically aligned, which deviates from the usual horizontal alignment of such wafers during manufacturing and coating processes. Therefore, appropriate alternative carrier systems are required for passivation.

[0004] The present invention therefore has the object of providing such an alternative carrier system or a corresponding assembly method which are optimized with regard to processing speed and quality.

[0005] This object is achieved by a storage insert according to claim 1, a carrier according to claims 10 and 16, and a mounting method according to claims 23 and 29. Preferred embodiments of these aspects of the invention can be found, inter alia, in the dependent claims.

[0006] The invention is based, among other things, on the idea of ​​inserting one or more stacks of multiple wafers into one or more corresponding compartments of a carrier as a wafer package rotated by 90°. Because the wafers are not transported into the carrier individually, as is usually the case, but rather in packages, the assembly process can be significantly accelerated.

[0007] According to a first aspect of the invention, the wafer packages are not inserted directly into the carrier compartments, but first into a corresponding storage insert or tray. Accordingly, according to a first aspect, the present invention is directed to a storage insert or tray for receiving a stack of multiple wafers, having two opposing side walls and a base plate displaceably mounted relative to the side walls for depositing a stack of multiple wafers. The storage insert further comprises a restoring mechanism capable of exerting an upward restoring force (i.e., along the stacking direction) on the base plate, parallel to the side walls.

[0008] The storage insert is preferably dimensioned such that a stack of at least 30, preferably at least 100, more preferably at least 250, even more preferably at least 500, and particularly preferably at least 1,000 wafers can be accommodated. For this purpose, the storage insert preferably has a height of at least 1 cm, more preferably at least 2 cm, particularly preferably at least 3 cm. The return mechanism preferably comprises one or more spring elements (preferably two spring elements) and / or an elastic material. The return mechanism is preferably suitable for exerting a force between 0.1 N and 20 N, preferably between 0.5 N and 5 N, on the base plate. The maximum return force of the return mechanism is preferably greater than 0.1 N, more preferably greater than 0.3 N, even more preferably greater than 1 N, and particularly preferably greater than 3 N.

[0009] The return mechanism, as will be explained in more detail below, serves to compress the wafer package, which will later be rotated by 90°, into the corresponding compartment of the carrier. This effectively prevents a gap from forming between adjacent, vertically aligned wafers, which could lead to parts of the wafer's top or bottom being inadvertently coated with an electrically insulating coating during the passivation process.

[0010] The base plate can be slidably mounted on the side walls by means of the return mechanism. However, it is particularly preferred that the storage insert further comprises a base plate fixedly connected to the side walls, and that the base plate is connected to the base plate via the return mechanism. The latter connection can be detachable or fixed. For example, one or more spring elements can be mounted on the base plate, onto which the base plate is loosely placed or with which the base plate is releasably engaged. Alternatively, the base plate can also be fixedly connected to spring elements attached to the base plate.

[0011] The side walls of the storage insert preferably each have a projection or ridge along one edge on their inner side as a support for the wafer stack. When the storage insert with the wafer stack is rotated 90°, the now vertically aligned wafers rest with their edges on these projections or ridges. This effectively prevents the wafers from falling out of the storage insert when the storage insert is rotated. Furthermore, all edges are aligned flush, preventing mutual shadowing by projections.

[0012] On their outer sides, the side walls of the storage insert preferably each have a receptacle for handling. This can be one or more of the following components: a hook, an eyelet, a raised or recessed structure that allows a positive grip, ensuring precise positioning and rotation.

[0013] The storage insert preferably contains a stack of multiple wafers resting on the base plate. The storage insert preferably contains at least 100, more preferably at least 250, even more preferably at least 500, and particularly preferably at least 1,000 wafers. The wafers preferably have substantially the same footprint as the base plate. This means that the ratio of base plate length to wafer length and / or base plate width to wafer width is less than 1.05, more preferably less than 1.03, and particularly preferably less than 1.01. The wafer stack preferably rests against the projections or webs on the inner sides of the side walls, with one edge of each wafer preferably coming into contact with the projections or webs.

[0014] The invention further relates to the storage insert rotated by 90°, in which the base plate is aligned vertically and the wafers of the stack rest on the projections or webs of the side walls.

[0015] The present invention is directed, according to a second aspect, to a carrier for one or more storage inserts as described above, wherein the carrier has a frame and one or more compartments for one or more storage inserts each as described above.

[0016] Each compartment of the carrier is preferably delimited by at least one web, preferably by two opposing webs, so that when multiple compartments are present, the two adjacent compartments are each separated from each other by a web arranged between them. If there is only a single compartment, the two webs delimiting this compartment preferably simultaneously form part of the frame. In other words, in this case, the compartment can also be formed or defined by the frame parts, so that in this case, the following features relating to the webs can then analogously relate to frame parts.

[0017] Preferably, each web has at least one, more preferably two, recess(es).

[0018] Preferably, at least one of the compartments accommodates a storage insert as described above, which has been rotated by 90° so that the base plate is vertically aligned. Preferably, a storage insert as described above is accommodated in several, particularly preferably in all, of the compartments.

[0019] The carrier preferably has at least 10, more preferably at least 25, even more preferably at least 50 and particularly preferably at least 100 compartments.

[0020] The storage insert accommodated in the respective compartment preferably has a wafer stack, which is preferably clamped between the base plate of the storage insert and the web (or frame part) defining the compartment. For this purpose, the storage insert is preferably introduced into the compartment such that the base plate of the storage insert is arranged parallel and adjacent to a web (or frame part) defining the compartment, and the uppermost wafer of the wafer stack is adjacent to the second web (or frame part) defining the compartment. Since the return mechanism of the storage insert exerts an upward return force (in the regular orientation) on the base plate parallel to the side walls, the return mechanism presses the wafer stack, now rotated by 90°, against the web (or frame part) defining the compartment.The return mechanism should preferably press the wafer stack against the web (or frame part) delimiting the compartment with a force between 0.1 N and 20 N, more preferably with a force between 0.5 N and 5 N.

[0021] If the web (or frame part) adjacent to the topmost wafer in the wafer stack has one or more recesses, these should preferably be arranged such that they do not overlap with electrical contacts in this topmost wafer, so that no material gets onto the electrical contacts during the passivation step. If this is not possible, the passivation could alternatively be performed using a dummy wafer as the topmost wafer, which is preferably used several times and shields the wafer below it in the stack from material.

[0022] The carrier and the storage insert can in principle be made of any material, provided that they survive edge passivation without damage, so that their melting point should preferably be greater than 200 °C, more preferably greater than 300 °C, and especially preferably greater than 400 °C. Examples of materials for the storage insert and / or the carrier are: steel, aluminum, titanium, polyetheretherketone (PEEK), polytetrafluoroethylene (PTFE), polyamide-imide (PAI), and polyphenylsulfone (PPS).

[0023] According to a third aspect, the present invention is directed to a method for equipping a carrier as described above. Within the scope of this method, a storage insert is first provided as described above, and a stack of several wafers is introduced into the storage insert such that the wafer stack rests on the base plate of the storage insert. The storage insert is then rotated by 90° such that the base plate is aligned vertically and preferably the wafers of the stack rest on the projections or webs of the side walls of the storage insert. The wafer stack is further pressed together, and the pressed and rotated wafer stack is then introduced into a compartment of the carrier. The rotation of the storage insert can take place before, after, or simultaneously with the pressing together.When the wafer stack is compressed, the return mechanism, in particular, is preloaded against its return force, so that after the wafer stack is inserted into the carrier's compartment, the return mechanism presses the wafer stack against the web (or frame part) defining the compartment, as already described above. Accordingly, the force during compression is preferably greater than the return force of the return mechanism.

[0024] The rotation of the storage insert, the compression of the wafer stack, and the insertion into the compartment are preferably carried out by means of a handling device or robot arm. For this purpose, the side walls of the storage insert preferably each have a receptacle on their outer side for a corresponding counterpart of the handling device or robot arm, which engages with these receptacles during or before the rotation and compression. The handling device or robot arm preferably also has a pressing mechanism for compressing the wafer stack or pressing it against the return mechanism.

[0025] As already explained above, the webs defining the compartments can have one or more recesses. These can be provided so that the pressing mechanism can at least partially engage these recesses when the compressed and rotated wafer stack is inserted into the carrier compartment. The pressing mechanism can then detach from the wafer stack and be retracted through the recesses, allowing the return mechanism to press the wafer stack against the web.

[0026] According to a fourth aspect, the present invention is further directed to an alternative carrier for one or more horizontally aligned wafer stacks, wherein the carrier has a frame and one or more compartments, each for one or more horizontally aligned wafer stacks. Each compartment of the carrier is preferably delimited by at least one web, preferably by two opposing webs, so that when there are multiple compartments, the two adjacent compartments are each separated from one another by a web arranged therebetween, and wherein a horizontally aligned wafer stack is received in at least one of the compartments such that the wafers in the compartment are vertically aligned and arranged parallel to the web or webs.

[0027] If there is only a single compartment, the two webs delimiting this compartment preferably simultaneously form part of the frame. In other words, in this case, the compartment can also be formed or defined by the frame parts, so that in this case, the following features relating to the webs can then analogously relate to frame parts.

[0028] Accordingly, in this fourth aspect of the invention, the storage insert discussed above is dispensed with and the wafer stack is inserted directly into a corresponding compartment of the carrier.

[0029] Accordingly, the wafer stack is preferably clamped, directly or indirectly, between two webs (or frame parts) defining the compartment. Each web can also have one or more (preferably two) recesses. In this fourth aspect of the invention, each compartment preferably has a compression mechanism that compresses the wafer stack in the compartment in the stacking direction, preferably with a force between 0.1 N and 20 N, more preferably with a force between 0.5 N and 5 N. The compression mechanism can comprise one or more, preferably two, spring elements and / or an elastic material arranged within the compartment. The compression mechanism is preferably attached, detachably or permanently, to one of the webs (or frame parts) defining the compartment. For example, a resilient plate can be attached to a web (or frame part) by means of one or more springs.Alternatively, the compression mechanism could be attached to one or both of the side walls defining the compartment, either detachably or fixedly.

[0030] Finally, according to a fifth aspect, the present invention is directed to a method for loading the carrier according to the fourth aspect. In this method, a stack of several wafers is first provided, and then the wafer stack is inserted into a compartment of a carrier such that the wafers are vertically aligned in the compartment and arranged parallel to the webs (or frame parts) of the carrier, wherein the insertion preferably takes place while overcoming the restoring force applied by the compression mechanism.

[0031] Here, too, insertion is preferably carried out using a handling device or robot arm. This handling device preferably has a pressure mechanism that preloads the compression mechanism when inserting the wafer stack.

[0032] For example, if the aforementioned resilient plate is attached to a web of the compartment by one or more springs, the handling device's pressing mechanism can first press the resilient plate toward the web against the restoring force of the springs, thereby enlarging the compartment accordingly. The handling device can then insert the wafer stack into the enlarged compartment and subsequently detach itself from the resilient plate, so that the latter, using the restoring force of the springs, acts on the wafer stack and presses it against the opposite web. Here, too, corresponding recesses can be provided on the webs into which the pressing mechanism can engage.However, this is not absolutely necessary since, for example, appropriate receptacles for the pressure mechanism can be provided between the web and the spring plate, so that the pressure mechanism can be detached from the compression mechanism without the need for corresponding recesses.

[0033] Preferred embodiments of the present invention are described in more detail below with reference to the figures. They show:

[0034] Figure 1 shows a storage insert according to a preferred embodiment of the present invention in a perspective view;

[0035] Figure 2 shows a carrier according to a preferred embodiment of the present invention in perspective view;

[0036] Figure 3 shows a handling device for use in the method according to the invention in a perspective view;

[0037] Figure 4 shows a carrier according to another preferred embodiment of the present invention in a perspective view; and Figure 5 shows a section of the carrier according to Figure 4.

[0038] Figure 1 shows a perspective view of a storage insert according to a preferred embodiment of the first aspect of the invention. The storage insert or tray 1 for receiving a stack (not shown) of a plurality of wafers or semiconductor elements has two opposing side walls 2 and a base plate 3, which is displaceably mounted relative to the side walls 2, for depositing a stack (not shown) of a plurality of wafers. Furthermore, a reset mechanism 4 is provided, which is suitable for exerting an upward restoring force on the base plate 3 parallel to the side walls 2. In the preferred embodiment shown, the reset mechanism is formed by two schematically indicated spring elements 4, via which the base plate 3 is connected to a base plate 5, which is connected to the side walls 2. The base plate 3 can be fixedly connected to the two spring elements 4 or rest loosely on them.Instead of the two springs 4, a single, larger leaf spring or a layer of an elastic material could alternatively be used to exert an upward restoring force on the base plate 3.

[0039] As is easily understood, the base plate 5 is not required for the invention, since the return mechanism could also be attached, for example, directly or indirectly to the two side walls 2. The two side walls 2 each have a projection or web 6 along one edge on their inner side, which serves as a support for the wafer stack once the storage insert 1 has been rotated by 90°. In the preferred embodiment shown in Figure 1, each of the side walls 2 has such a projection or web 6 on both inner edges, although this is not required.

[0040] On their outer side, the side walls 2 each have a receptacle 7 for a handling device 20 (see Figure 3). This receptacle 7 can preferably engage in a form-fitting manner with a corresponding counterpart in the handling device 20.

[0041] Furthermore, on the outside of each side wall 2, two lower support points 8 are provided, which serve to rest on corresponding supports in the carrier, as explained in more detail below.

[0042] Furthermore, the outer sides of the side walls 2 each have an insertion bevel 9 on one side edge, which is intended to facilitate the insertion of the storage insert 1 into the carrier 10.

[0043] Figure 2 shows a perspective view of a carrier 10 according to a preferred embodiment of the second aspect of the invention for a plurality of storage inserts 1, for example for a plurality (here: 26) storage inserts as shown in Figure 1. The carrier 10 has a frame 11a, 11b and a plurality of compartments 12, each for a storage insert 1. The frame can also have the shape of a base plate 18 in sections and, for example, be provided with guide rails 17 for easy processing. The individual compartments 12 preferably have no bottom in order to also enable passivation of the wafer stack from below if necessary. Instead, support webs 16 are preferably provided, which support the support points 8 of the storage insert 1 (cf. Figure 1).

[0044] In the preferred embodiment shown, the compartments 12 are each separated from one another by webs 13, so that each compartment 12 is formed by two webs 13 and by two sections of the lateral frame elements 11b. In the case of edge-side compartments, the compartment could also be delimited on one side by a section of the frame 11a. In the preferred embodiment shown, the webs 13 each have two recesses 14 for the pressing mechanism 25 of the handling 20 (see Figure 3). Of course, the frame 10 can also have more or fewer compartments than the 26 shown as an example. In particular, the frame 10 could also have only a single compartment 12, which is then preferably delimited by frame parts 11a, so that the webs 13 would then not be necessary.

[0045] An exemplary handling device 20 is shown in perspective view in Figure 3. The handling device 20 comprises, among other things, a gripper arm 21 with a receiving mechanism 22 and a pressing mechanism 24. The receiving mechanism 22 has the above-mentioned counterparts 23 for the receptacles 7 in the side walls 2 of the storage insert 1, with which these can engage in a form-fitting manner. This allows a filled storage insert 1 to be lifted and rotated by 90°. In the preferred embodiment shown, the pressing mechanism 24 has two arms 25 that can press the wafer stack towards the base plate 5 and, in doing so, can overcome the restoring force of the restoring mechanism 4.

[0046] The storage insert 1 with the thus compressed wafer stack can then be inserted into a compartment 12 of the carrier 10, whereby the two arms 25 of the pressing mechanism 24 engage the recesses 14 provided for this purpose in the associated web 13 when the pressing mechanism is released. The handling device 20 is then retracted, and the restoring forces of the restoring mechanism 4 press the base plate 3 together with the wafer stack toward the opposite web 13.

[0047] Figure 4 shows a perspective view of a preferred embodiment of a carrier 10a according to the fourth aspect of the invention, which makes the use of the storage insert 1 obsolete. The carrier 10a according to Figure 4 also has a frame 11a, 11b and a plurality of compartments 12, each for a horizontally aligned wafer stack, wherein the compartments 12 are separated from one another by webs 13 and wherein a horizontally aligned wafer stack 1a is received in at least one of the compartments 12 such that the wafers (not shown individually in Figure 4) are vertically aligned in the compartment 12 and arranged parallel to the webs 13.

[0048] In this variant, too, it is preferred that each compartment has a compression mechanism 3a, 4, which compresses the wafer stack 1a in the compartment 12 in the stacking direction in order to prevent gaps between adjacent wafer edges as effectively as possible. In the preferred embodiment shown (see, in particular, the detailed view in Figure 5), the compression mechanism has a resilient plate 3a, which is resiliently mounted on the adjacent web 13 by means of two spring elements 4, so that the inserted wafer stack 1a is pressed together between a web 13 on the one hand and the resilient plate 3a on the other.

[0049] In Figures 4 and 5, the webs 13 are also provided with corresponding recesses 14, which allow the two arms 25 of the pressing mechanism 24 to be inserted. However, this is not necessary in the preferred embodiment shown, since here the pressing mechanism can be inserted into the space between the web 13 and the resilient plate 3a. For this purpose, the preferred embodiment shown provides two receptacles 19 for the handling device, which enable the handling device to engage with the resilient plate 3a and pull it towards the adjacent web 13 against the restoring force of the springs 4. The wafer stack can then be inserted into the thus enlarged compartment 12. After the handling device is retracted, the resilient plate 3a is pressed against the wafer stack by means of the springs 4, and the wafer stack is pushed to the opposite side towards the web 13.

Claims

Claims 1. Storage insert (1) for receiving a stack of several wafers with two opposite side walls (2) and a base plate (3) displaceably mounted relative to the side walls (2) for storing a stack of several wafers, further comprising a return mechanism (4) which is suitable for exerting an upward return force on the base plate (3) parallel to the side walls (2).

2. Storage insert according to claim 1, wherein the storage insert (1) further comprises a base plate (5) connected to the side walls (2) and wherein the bottom plate (3) is connected to the base plate (5), detachably or fixedly, via the return mechanism (4).

3. Storage insert according to claim 1 or 2, wherein the return mechanism (4) comprises one or more, preferably two, spring elements and / or an elastic material.

4. Storage insert according to one of the preceding claims, wherein the return mechanism (4) is suitable for exerting a force between 0.1 N and 20 N, preferably between 0.5 N and 5 N, on the base plate (3).

5. Storage insert according to one of the preceding claims, wherein the side walls (2) each have on their inner side along an edge a projection or a web (6) as a support for the wafer stack.

6. Storage insert according to one of the preceding claims, wherein the side walls (2) each have on their outer side a receptacle (7) for a handling device (20).

7. Storage insert according to one of the preceding claims, further comprising a stack of several wafers resting on the base plate (3), wherein the wafers preferably have the same base area as the base plate (3).

8. Storage insert according to claim 7, dependent on claim 5, wherein the stack is attached to the projections or webs (6).

9. Storage insert according to claim 8, wherein the storage insert (1) has been rotated by 90° so that the base plate (3) is aligned vertically and the wafers of the stack rest on the projections or webs (6).

10. A carrier (10) for one or more storage inserts (1) according to one of claims 7 to 9, wherein the carrier (10) comprises a frame (11a, 11b) and one or more compartments (12) for one or more storage inserts (1) according to one of claims 7 to 9.

11. Carrier according to claim 10, wherein each compartment (12) is delimited by at least one web (13), preferably by two webs (13), and / or wherein the plurality of compartments (12) are each separated from one another by webs (13) and wherein preferably each web (13) has at least one, preferably two, recess(es) (14).

12. Carrier according to claim 10 or 11, wherein in at least one of the compartments (12) a storage insert (1) according to one of claims 7 to 9 is received, which has been rotated by 90° so that the base plate (3) is aligned vertically.

13. Carrier according to claim 12, wherein the wafer stack is clamped between the base plate (3) of the storage insert (1) and the web (13) delimiting the compartment (12).

14. Carrier according to claim 12 or 13, wherein the return mechanism (4) of the storage insert (1) presses the wafer stack with a force between 0.1 N and 20 N, preferably between 0.5 N and 5 N, against the web (13) delimiting the compartment (12).

15. A carrier according to any one of claims 12 to 14, dependent on claim 11, wherein the wafer has electrical contacts on top of the wafer stack and wherein the recesses (14) in the webs (13) are arranged such that the electrical contacts do not overlap with the recesses (14).

16. A carrier (10a) for one or more horizontally aligned wafer stacks, wherein the carrier (10a) has a frame (11a, 11b) and one or more compartments (12) for each horizontally aligned wafer stack, wherein each compartment (12) is delimited by at least one web (13), preferably by two webs (13), and / or wherein the plurality of compartments (12) are each separated from one another by webs (13), and wherein a horizontally aligned wafer stack is received in at least one of the compartments (12) such that the wafers in the compartment (12) are aligned vertically and arranged parallel to the web (13) or the webs (13).

17. A carrier according to claim 16, wherein each web (13) has at least one, preferably two, recess(es) (14).

18. Carrier according to claim 16 or 17, wherein the wafer stack is clamped, directly or indirectly, between two webs (13) delimiting the compartment (12).

19. Carrier according to one of claims 16 to 18, wherein each compartment (12) has a compression mechanism (3a, 4) which compresses the wafer stack in the compartment (12) in the stacking direction, preferably with a force between 0.1 N and 20 N, more preferably with a force between 0.5 N and 5 N.

20. Carrier according to claim 19, wherein the compression mechanism (3a, 4) comprises one or more, preferably two, spring elements (4) and / or an elastic material, which is / are preferably arranged within the compartment (12).

21. Carrier according to claim 19 or 20, wherein the compression mechanism (3a, 4) is attached, detachably or fixedly, to one of the webs (13) delimiting the compartment (12).

22. Carrier according to claim 19 or 20, wherein the compartment has side walls oriented perpendicular to the webs and wherein the compression mechanism (3a, 4) is attached to one or both of the side walls, detachably or fixedly.

23. A method for equipping a carrier (10) according to one of claims 10 to 15, comprising the following steps: a) providing a storage insert (1) according to one of claims 1 to 6; b) introducing a stack of several wafers into the storage insert (1) such that the wafer stack rests on the base plate (3) of the storage insert (1); c) rotating the storage insert (1) by 90° so that the base plate (3) is aligned vertically and preferably the wafers of the stack rest on the projections or webs (6); d) pressing the wafer stack together; and e) introducing the pressed and rotated wafer stack into a compartment (12) of the carrier (10).

24. The method according to claim 16, wherein the compression force is greater than the restoring force of the restoring mechanism (4).

25. Method according to claim 16 or 17, wherein steps c) to e) are carried out by means of a handling device (20).

26. Method according to claim 18, wherein the side walls (2) of the storage insert (1) each have on their outer side a receptacle (7) for the handling (20) and wherein the handling (20) engages with the receptacles (7) in step c).

27. Method according to claim 18 or 19, wherein the handling (20) comprises a pressing mechanism (24) and wherein step d) is carried out by means of the pressing mechanism (24).

28. The method according to claim 20, wherein the compartments (12) of the carrier (10) are separated from one another by webs (13) and wherein each web (13) has at least one, preferably two, recess(es) (14) and wherein the pressing mechanism (24) in step e) is at least partially immersed in the recess(es) (14).

29. A method for equipping a carrier (10a) according to one of claims 16 to 22, comprising the following steps: a) providing a stack of a plurality of wafers; b) introducing the wafer stack into a compartment (12) of a carrier (10a) according to one of claims 16 to 22 such that the wafers are vertically aligned in the compartment (12) and arranged parallel to the web (13) or webs (13) of the carrier (10), wherein the introduction preferably takes place while overcoming the restoring force applied by the compression mechanism (3a, 4).

30. The method according to claim 29, wherein step b) is carried out by means of a handling device (20).

31. The method according to claim 29 or 30, wherein the handling (20) has a pressing mechanism (24) and wherein in step b) the pressing mechanism (24) pretensions the compression mechanism (3a, 4), the wafer stack is introduced into the compartment (12) and subsequently the compression mechanism (3a, 4) compresses the wafer stack in the compartment (12).

32. Method according to claim 31, wherein the webs (13) of the compartments (12) each have at least one, preferably two, recess(es) (14) and wherein the pressing mechanism (24) in step b) is at least partially immersed in the recess(es) (14).

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