Method for forming a layer structure surrounding at least one recess, and apparatus with a layer structure
Patent Information
- Application Number
- EP2023705384
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-02-22
- Filing Date
- 2023-02-14
- Publication Date
- 2025-01-01
AI Technical Summary
Conventional methods for forming a layer structure surrounding recesses in semiconductor wafers often result in undesired bending or bulging, especially when the second semiconductor layer is thin, due to the lack of effective support structures during critical process steps.
The method involves structuring depressions in a semiconductor layer to form recesses and wall structures that are converted into support structures through a chemical reaction with a medium, allowing for the formation of a thin second semiconductor layer with reduced risk of bending, and optionally using these structures as support during subsequent processes, with the ability to delay or avoid removal of reaction products until critical processes are complete.
This approach enables the production of a warp-free layer structure with a thin second semiconductor layer, effectively preventing bending and bulging, and allows for the use of residual support structures to maintain planarity and stability during further processing steps.
Smart Images
Figure 1.1
Abstract
Description
[0001] Description
[0002] title
[0003] Method for forming a layer structure surrounding at least one recess and device with a layer structure
[0004] The invention relates to a method for forming a layered structure surrounding at least one recess. The invention also relates to devices having a layered structure.
[0005] State of the art
[0006] US 10,578,505 B2 describes a process for forming a cavity covered by a silicon membrane in a monocrystalline silicon wafer. When implementing the conventional process, a plurality of trenches are first etched into the silicon wafer in such a way that a plurality of columns are patterned out of the silicon wafer. The trenches are then sealed by epitaxial deposition of a silicon layer. A high-temperature annealing step is then carried out in a hydrogen atmosphere at 1190°C for 30 minutes. By rearranging the material of the columns previously patterned out of the silicon wafer, the silicon layer is supposedly convertible into the desired silicon membrane, which spans a column-free cavity at the location of the former trenches.
[0007] Disclosure of the invention
[0008] The invention provides a method for forming a layer structure surrounding at least one recess having the features of claim 1, a device having the features of claim 11 and a device having the features of claim 12.
[0009] Advantages of the invention
[0010] The present invention enables the production of a layer structure surrounding at least one recess, wherein even with a comparatively large-area formation of the at least one recess and with a relatively thin layer thickness of the second / third semiconductor layer covering at least part of the area of the at least one recess, an undesired bending or bulging of the second / third semiconductor layer is prevented.Even when producing at least one component on a side of the second / third semiconductor layer directed away from the first semiconductor layer, such as at least one conductor track and / or at least one resistor structure, at least remnants of the first / second wall structures can be used as support structures for supporting at least the second / third semiconductor layer, so that even then there is no / little fear of undesired bending or bulging of the second / third semiconductor layer of the layer structure.
[0011] In an advantageous embodiment of the method, a product of the chemical reaction between the medium and the first wall structures is removed from the at least one first recess. The embodiment of the method described here is therefore also suitable for producing a layered structure whose at least one recess is "free" of residues of the product of the chemical reaction.
[0012] Advantageously, the first wall structures, which are at least partially converted into the product of the chemical reaction due to the chemical reaction with the medium, can be used as support structures for supporting at least the second semiconductor layer for at least one further process carried out between the introduction of the medium and the removal of the product of the chemical reaction. In particular, the removal of the product of the chemical reaction can be delayed until all processes critical to the deflection or warping of the second semiconductor layer have been completed.
[0013] For example, the medium can be introduced into and / or retained in the at least one first recess until the first wall structures projecting into the at least one first recess are completely converted into the product of the chemical reaction due to the chemical reaction of the medium with the first wall structures. Alternatively, the chemical reaction of the medium with the first wall structures can also be stopped early enough that residues of the first wall structures made of at least one material identical to the first semiconductor layer remain.Preferably, the first wall structures projecting into the at least one first recess are used as support structures for supporting at least the second semiconductor layer for at least one further process performed between the at least partial covering of the at least one first recess on the first surface of the first semiconductor layer and the introduction of the medium. Thus, even if the at least one process is conventionally associated with a high risk of the second semiconductor layer bending or bulging into the at least one recess, this undesirable process is prevented by the first wall structures used as support structures.
[0014] As an advantageous development, at least the following steps can be carried out between the at least partial covering of the at least one first recess on the first surface of the first semiconductor layer and the introduction of the medium: structuring a plurality of second depressions in the second semiconductor layer starting from a second surface of the second semiconductor layer directed away from the first semiconductor layer, such that the second depressions form at least one coherent second recess in the second semiconductor layer comprising a plurality of second depressions, into which second wall structures structured out of the second semiconductor layer by means of the second depressions protrude, and covering the at least one second recess on the second surface of the second semiconductor layer at least partially,by forming at least one third semiconductor layer from at least one material identical to the first semiconductor layer, wherein at least one second medium supply opening is formed for the at least one second recess, which extends at least through the third semiconductor layer and opens into the associated second recess, wherein the medium is also introduced into the at least one second recess through the at least one second medium supply opening. The introduction of the medium into the at least one second recess can optionally take place simultaneously with the introduction of the medium into the at least one first recess or at an earlier or later time. The layer structure produced by means of the further development described here can be advantageously used for the purposes explained below.
[0015] Optionally, the at least one first medium supply opening and / or the at least one second medium supply opening can be closed such that a liquid-tight and / or gas-tight sealed cavity is present at the location of the at least one first recess and / or the at least one second recess. The layer structure produced in this way can be advantageously used for a variety of devices, such as a sensor device, especially for a surface micromechanical pressure sensor.
[0016] Preferably, the at least one first medium supply opening and / or the at least one second medium supply opening are created by laser melting the second semiconductor layer and / or the third semiconductor layer. In contrast to a deposition process, laser melting allows for the relatively free adjustment of any desired internal pressure and the inclusion of a freely selectable medium, e.g., a gas or gas mixture, in the at least one liquid-tight and / or gas-tight sealed cavity of the produced layer structure.
[0017] Alternatively or additionally, the first wall structures, which are at least partially converted into the product of the chemical reaction due to the chemical reaction with the medium, can also be used as support structures for supporting at least the second semiconductor layer for at least one further process carried out between the introduction of the medium and the closure of the at least one first medium supply opening. This also ensures reliable protection against deflection or warping, especially during critical processes.
[0018] For example, the second semiconductor layer can be formed by growing the second semiconductor layer of monocrystalline or polycrystalline silicon on the first surface of the first semiconductor layer of monocrystalline or polycrystalline silicon. However, it should be noted that the feasibility of the method described here is not limited to the use of silicon for at least the first semiconductor layer and the second semiconductor layer.
[0019] Furthermore, the devices according to the invention also realize the advantages explained above.
[0020] Brief Description of the Drawings Further features and advantages of the present invention are explained below with reference to the figures. They show:
[0021] Fig. 1A to IE show cross sections of (intermediate) products for explaining a first embodiment of the method for forming a layer structure surrounding at least one recess;
[0022] Fig. 2 shows a cross section of an (intermediate) product for explaining a second embodiment of the method for forming a layer structure surrounding at least one recess;
[0023] Fig. 3 shows a cross section of an (intermediate) product for explaining a third embodiment of the method for forming a layer structure surrounding at least one recess;
[0024] Fig. 4A and 4B show cross sections of (intermediate) products for explaining a fourth embodiment of the method for forming a layer structure surrounding at least one recess; and
[0025] Fig. 5A and 5B show cross sections of (intermediate) products for explaining a fifth embodiment of the method for forming a layer structure surrounding at least one recess.
[0026] Embodiments of the invention
[0027] Fig. 1A to IE show cross sections of (intermediate) products for explaining a first embodiment of the method for forming a layer structure surrounding at least one recess.
[0028] In the embodiment of the method described here, a plurality of (first) depressions 10 are first structured into a first semiconductor layer 12 of the later layer structure. The depressions 10 can also be referred to as trench or channel structures. The depressions 10 are structured starting from a first surface 12a of the first semiconductor layer 12. For example, the depressions 10 can be etched into the first semiconductor layer 12 using a photoresist mask and / or a hard mask, specifically made of silicon dioxide. The depressions 10 are formed in the first semiconductor layer 12 such that the depressions 10 form at least one contiguous (first) recess 14 comprising a plurality of depressions 10 in the first semiconductor layer 12. Fig. 1Aa shows a cross section through the depressions 10 oriented perpendicular to the first surface 12a of the first semiconductor layer 12, while in Fig.lAb shows a cross-section through the depressions 10 aligned parallel to the first surface 12a. As can be seen in Fig. lAb, the respective connected formation of the at least one recess 14 is to be understood in each case that the depressions 10 encompassed by the respective recess 14 "open" into one another (or are connected to one another) in such a way that a medium transfer of a liquid or gaseous substance is possible between all depressions 10 encompassed by the same recess 14.
[0029] Furthermore, by means of the depressions 10, (first) wall structures 16 are patterned out of the first semiconductor layer 12, which protrude into the at least one recess 14. The wall structures 16 can also be described as ridge or column structures. The wall structures 16 patterned out of the first semiconductor layer 12 are therefore formed from at least one of the same material as the first semiconductor layer 12. The first semiconductor layer 12 is to be understood as a layer which has at least one semiconductor material as its at least one material. The first semiconductor layer 12 can, for example, be a silicon layer, in particular a monocrystalline silicon layer. However, it should be noted that the feasibility of the method described here is not limited to any specific material of the first semiconductor layer 12.Instead of or as a supplement to silicon, the first semiconductor layer 12 can also comprise at least one further semiconductor material and / or at least one non-semiconductor material, such as at least one electrically insulating material and / or at least one metal.
[0030] In a further method step, the at least one recess 14 on the first surface 12a of the first semiconductor layer 12 is covered at least partially by forming at least one second semiconductor layer 18 from the at least one same material as the first semiconductor layer 12. If the second semiconductor layer 18 is arranged directly on the first surface 12a of the first semiconductor layer 12, the second semiconductor layer 18 can be referred to as a sealing layer of the at least one recess 14 in the first semiconductor layer 12. The second semiconductor layer 18 is also to be understood as a layer which has at least one semiconductor material as its at least one material.The second semiconductor layer 18 can be formed, for example, by forming the second semiconductor layer 18 from polycrystalline or epitaxially grown monocrystalline silicon (directly) on the first surface 12a of the first semiconductor layer 12 made of (monocrystalline) silicon. Instead of or in addition to silicon, the second semiconductor layer 18 can also comprise at least one further semiconductor material and / or at least one non-semiconductor material, such as at least one electrically insulating material and / or at least one metal.
[0031] During or after the formation of the second semiconductor layer 18, at least one (first) medium supply opening 20 is formed for the at least one recess 14, which extends at least through the second semiconductor layer 18. The at least one medium supply opening 20 is formed in such a way that each medium supply opening 20 opens at the recess 14 assigned to it and can therefore be used to introduce a gaseous and / or liquid substance into the recess 14 assigned to it. Fig. 1Aa shows the intermediate product after the formation of the second semiconductor layer 18 with the at least one medium supply opening 20 extending through the second semiconductor layer 18. It can be seen that the wall structures 16 structured from the first semiconductor layer 12 support the second semiconductor layer 18 in such a way that bending or bulging of the second semiconductor layer 18 is reliably prevented.
[0032] Fig. 1B schematically illustrates the introduction of a medium through the at least one medium supply opening 20 into the at least one recess 14. However, it should be noted here that at least one further process can be performed between the at least partial covering of the at least one recess 14 on the first surface 12a of the first semiconductor layer 12 and the introduction of the medium. During the execution of the at least one further process, the wall structures 16 projecting into the at least one recess 14 serve as support structures for supporting at least the second semiconductor layer 18. Thus, the wall structures 16 prevent undesired deformation of the second semiconductor layer 18, even if the at least one further process would conventionally be associated with a high risk of bending or warping of the second semiconductor layer 18.The second semiconductor layer 18 can therefore be easily formed with a comparatively thin layer thickness, without having to fear undesirable bending or warping during the at least one further process. The method described here thus enables the production of the second semiconductor layer 18 as a warping-free membrane, whose bending or warping during the process steps is effectively prevented.
[0033] As schematically shown in Fig. 1B and 1C, the medium introduced through the at least one medium supply opening 20 into the at least one recess 14 is to be understood as a substance which chemically reacts with the wall structures 16 protruding into the at least one recess 14. Thus, due to the chemical reaction of the medium with the wall structures 16, the wall structures 16 protruding into the at least one recess 14 are at least partially converted into a product 22 of the chemical reaction (i.e., into the sole product 22 of the chemical reaction or into one of the products 22 of the chemical reaction).The product 22 of the chemical reaction can also be formed on a second surface 18a of the second semiconductor layer 18 directed away from the first semiconductor layer 12, on a second surface 18b of the second semiconductor layer 18 directed toward the first semiconductor layer 12, on the walls of the at least one medium supply opening 20, and / or on the walls of the recess 14. As can be seen in Fig. 1B, the formation of the at least one medium supply opening 20 and the continuous formation of the at least one recess 14 ensure that the medium flows into the at least one recess 14 and flows around the wall structures 16 projecting therein.
[0034] The medium carrying out the chemical reaction with the wall structures 16 can be understood as a gaseous medium or a liquid medium. If the semiconductor layers 12 and 18 are formed from silicon, oxygen, for example, can be introduced as a medium into the at least one recess 14. In this case, the oxygen introduced as a medium can cause a thermal oxidation process as a chemical reaction, which leads to the formation of silicon dioxide as the product 22. However, the feasibility of the method described here is not limited to the use of oxygen as the medium. As shown in Fig.As schematically shown in Fig. 1C, the medium can be introduced into and / or held in the at least one recess 14 until the wall structures 16 projecting into the at least one recess 14 are (almost) completely converted into the product 22 of the chemical reaction due to the chemical reaction of the medium with the wall structures 16. However, as schematically shown in Fig. 1B, the chemical reaction can alternatively be terminated so early that remnants of the wall structures 16 made of the at least one material identical to the first semiconductor layer 12 still remain.
[0035] It can be seen in Figs. 1B and 1C that the reaction of the medium with at least the wall structures 16 does not lead to clogging of the at least one medium supply opening 20 with the product 22 of the chemical reaction. The pressure prevailing in the at least one recess 14 during the chemical reaction therefore has no influence on a subsequent internal pressure in at least one cavern formed at the location of the at least one recess 14 by means of the further process steps.
[0036] Fig. 1D shows the intermediate product after removal of the product 22 of the chemical reaction of the medium with the first wall structures 16 from the at least one recess 14. However, it should be noted here that removal of the product 22 of the chemical reaction from the at least one recess 14 is optional. If desired, the wall structures 16, which are at least partially converted into the product 22 due to the chemical reaction with the medium, can also be retained. However, if removal of the product 22 of the chemical reaction from the at least one recess 14 is desired, this method step takes place before a subsequent closure of the at least one medium supply opening 20.For example, the product 22 of the chemical reaction can be removed from the at least one recess 14 by means of an etching medium introduced via the at least one medium supply opening 20, selectively with respect to the at least one material of the semiconductor layers 12 and 18. Optionally, the removal of the product 22 of the chemical reaction from the at least one recess 14 can be carried out, for example, by means of an HF gas-phase etching process.
[0037] A particular advantage of the method described here is that, even upon subsequent removal of the product 22 of the chemical reaction from the at least one recess 14, the wall structures 16 at least partially converted into the product 22 of the chemical reaction can still be used as support structures for supporting at least the second semiconductor layer 18 for at least one further process carried out between the introduction of the medium and the removal of the product 22 of the chemical reaction with the wall structures 16. The removal of the product 22 of the chemical reaction can be delayed in the method described here until all processes critical with regard to deformation of the second semiconductor layer 18 have been completed.The method described here can therefore be advantageously integrated into manufacturing processes which conventionally have problematic processes with regard to a desired flatness or freedom from warpage of the second semiconductor layer 18.
[0038] Fig. 1E shows the (intermediate) product of the method described here after closing the at least one medium supply opening 20. Closing the at least one medium supply opening 20 is understood to mean at least a particle-tight closure of the at least one medium supply opening 20. Preferably, the at least one medium supply opening 20 is closed in a liquid-tight and / or gas-tight manner in the method step schematically illustrated by Fig. 1E. By closing the at least one medium supply opening 20, a cavity 26 is realized at the location of the at least one recess 14, which cavity is surrounded by a layer structure 28 comprising at least the semiconductor layers 12 and 18. The finished layer structure 28 with its at least one cavity 26 designed as a cavern and / or channel structure can then be used for a variety of devices.
[0039] To close the at least one medium supply opening 20, for example, at least one sealing material 24 can be deposited until the at least one medium supply opening 20 is completely filled with the at least one sealing material 24. Deposits of the at least one sealing material 24, which are often also formed on the second surface 18a of the second semiconductor layer 18, on a second surface 18b of the second semiconductor layer 18 directed towards the first semiconductor layer 12, on the walls of the at least one medium supply opening 20 and / or on the walls of the at least one cavity 26 during the deposition of the at least one sealing material 24, have (essentially) no influence on the subsequent layer structure 28. In the embodiment described here, silicon 24 is deposited as the sealing material 24 purely by way of example.
[0040] Fig. 2 shows a cross section of an (intermediate) product for explaining a second embodiment of the method for forming a layer structure surrounding at least one recess.
[0041] The embodiment schematically illustrated in Fig. 2 differs from the previously explained method only in that silicon dioxide 30 is deposited as the sealing material 30 for sealing the at least one medium supply opening 20. For further method steps of the method of Fig. 2, reference is made to the previously explained embodiment of Figs. 1A to 1E.
[0042] Fig. 3 shows a cross section of an (intermediate) product for explaining a third embodiment of the method for forming a layer structure surrounding at least one recess.
[0043] In the embodiment of Fig. 3, a silicon layer 32 is first grown to close the at least one medium supply opening 20. A silicon dioxide layer 34 is then deposited until the at least one medium supply opening 20 is completely filled. For further method steps of the method of Fig. 3, reference is made to the above-explained embodiment of Figs. 1A to 1E.
[0044] Fig. 4A and 4B show cross sections of (intermediate) products for explaining a fourth embodiment of the method for forming a layer structure surrounding at least one recess.
[0045] As can be seen in Fig. 4Aa based on a cross-section through the depressions 10 in a plane oriented perpendicular to the first surface 12a, a plurality of connected recesses 14a and 14b can also be structured into the first semiconductor layer 12 by means of the depressions 10. Optionally, the recesses 14a and 14b can also be connected to one another via at least one channel structure. Although this is not illustrated, a height hl of the depressions 10 of a first recess 14a oriented perpendicular to the first surface 12a can be different from a second height h2 of the depressions 10 of a second recess 14b oriented perpendicular to the first surface 12a. The later recesses 14a and 14b (or caverns 26a and 26b) formed by the method described here can therefore also have different heights hl and h2. Fig.Fig. 4Ab shows a cross section through some of the depressions 10 aligned parallel to the first surface 12a of the first semiconductor layer 12. It can be seen from a comparison of Figs. 1Ab and 4Ab that a pattern formed by the depressions 10 of the same recess 14 can be selected with a relatively high degree of design freedom.
[0046] In the method step illustrated in Fig. 4B, the at least one medium supply opening 20 is closed by laser melting the second semiconductor layer 18. By means of a light beam 36, specifically a laser beam 36, which is directed onto the at least one medium supply opening 20 on the second surface 18a of the second semiconductor layer 18, the second semiconductor layer 18 can be locally melted at the location of the at least one medium supply opening 20 in such a way that subsequent solidification of the molten material leads to the closure of the at least one medium supply opening 20. A particular advantage of the method step illustrated in Fig. 4B is that, during laser melting, the internal pressure enclosed in the at least one subsequent cavity 26a and 26b can be selected relatively freely.Furthermore, the closing of the at least one medium supply opening 20 by means of laser melting can also be used to enclose a freely selectable gas or gas mixture in the at least one later cavern 26a and 26b.
[0047] With regard to further method steps of the method of Figs. 4A and 4b, reference is made to the embodiments of Figs. 1 to 3 explained above.
[0048] All of the methods explained above can be used to produce a layer structure 28 with a second semiconductor layer 18 formed as a membrane, which delimits the at least one recess 14, 14a, and 14b (or cavity 26, 26a, and 26b) formed in the layer structure 28. Due to the support / stabilization of the second semiconductor layer 18 by the wall structures 16 used as support structures during each of the methods, an advantageous flatness or freedom from warping of the membrane thus realized is ensured.For example, by means of a chemical-mechanical polishing step performed during one of the methods on the second semiconductor layer 18 supported by the wall structures 16, a homogeneous removal can be achieved to reduce the thickness of the second semiconductor layer 18, without the processed second semiconductor layer 18 disadvantageously bending or warping before and / or during the chemical-mechanical polishing step. The second semiconductor layer 18 can therefore be formed warp-free even with a relatively small layer thickness.
[0049] A layer structure 28 realized by means of the methods explained above can be used, for example, as at least part of a surface micromechanical pressure sensor, wherein a pressure measurement is carried out using the second semiconductor layer 18 used as a pressure-sensitive membrane.
[0050] However, it should also be noted that when carrying out each of the methods described above, the removal of the wall structures 16, which are at least partially converted into the product 22 of the chemical reaction due to the chemical reaction with the medium, can be omitted. Instead, at least remnants of the wall structures 16 can be retained in the at least one recess 14, 14a, and 14b, which can thus still be used to support at least the second semiconductor layer 18 even during operation of a device formed with the layer structure 28. Optionally, at least remnants of the wall structures 16 can also be used to produce thermally insulated regions of the semiconductor layer 18.By shaping the medium supply opening 20, it is also possible to form a thermally insulated region consisting of at least a part of the semiconductor layer 18, which region can be at least partially supported / attached / arranged on non-removed wall structures 16 in the at least one recess 14, 14a and 14b.
[0051] The methods described above thus also realize a device as schematically illustrated in Figs. 1E, 2, 3, and 4B. The device has a layer structure 28 and at least one recess 14, 14a, and 14b (or cavity 26, 26a, and 26b) formed in a first semiconductor layer 12 of the layer structure 28. The at least one recess 14, 14a, and 14b each comprises a plurality of first depressions 10, which are structured into the first semiconductor layer 12 starting from a first surface 12a of the first semiconductor layer 12. Furthermore, the first depressions 10 form the at least one contiguous first recess 14, 14a, and 14b in the first semiconductor layer 12, comprising a plurality of first depressions 10.The at least one first recess 14, 14a, and 14b is each at least partially covered on the first surface 12a of the first semiconductor layer 12 by at least one second semiconductor layer 18 formed from the at least one same material as the first semiconductor layer 12. In addition, the layer structure 28 for the at least one first recess 14, 14a, and 14b has at least one track of at least one first medium supply opening 20, which extends at least through the second semiconductor layer 18 and opens into the associated first recess 14, 14a, and 14b.The layer structure 28 also has at least remnants of first wall structures 16 projecting into the at least one first recess 14, 14a, and 14b, which are patterned out of the first semiconductor layer 12 by means of the first depressions 10 and are at least partially converted into a product 22 of a chemical reaction of the at least one material of the first semiconductor layer 12 with a medium. Thus, the device described here can be used well for applications in which supporting at least the second semiconductor layer 18 by means of the remnants of the first wall structures 16 is advantageous.
[0052] Fig. 5A and 5B show cross sections of (intermediate) products for explaining a fifth embodiment of the method for forming a layer structure surrounding at least one recess.
[0053] In the method schematically illustrated by Figures 5A and 5B, between the at least partial covering of the at least one first recess 14 formed in the first semiconductor layer 12 on the first surface 12a and the introduction of the medium, a plurality of second depressions 40 are first structured into the second semiconductor layer 18. The structuring of the second depressions 40 takes place starting from the second surface 18a of the second semiconductor layer 18 such that the second depressions 40 form at least one contiguous second recess 42a and 42b in the second semiconductor layer 18. In addition, second wall structures 44 are structured out of the second semiconductor layer 18 by means of the second recesses 40 such that the second wall structures 44 protrude into the at least one second recess 42a and 42b.If at least two second recesses 42a and 42b are formed in the second semiconductor layer 18, these can have different heights perpendicular to the second surface 18a of the second semiconductor layer 18.
[0054] As can be seen in Fig. 5A, the at least one second recess 42a and 42b is then at least partially covered on the second surface 18a of the second semiconductor layer 18. This is done by forming at least one third semiconductor layer 46 from the at least one same material as the first semiconductor layer 12. The third semiconductor layer 46 is also to be understood as a layer which has at least one semiconductor material as its at least one material. For example, a polycrystalline or epitaxially grown monocrystalline silicon layer can be formed as the third semiconductor layer 46 directly on the second surface 18a of the second semiconductor layer 18 made of silicon. Instead of or as a supplement to silicon, the third semiconductor layer 46 can, however, also contain at least one further semiconductor material and / or at least one non-semiconductor material, such asat least one electrically insulating material and / or at least one metal.
[0055] Fig. 5A shows the intermediate product after forming at least one second medium supply opening 48 for the at least one second recess 42a and 42b in the second semiconductor layer 18. The at least one second recess 42a and 42b can optionally lie completely above the at least one first recess 14, at least partially above the at least one first recess 14, or completely outside the area above the at least one first recess 14. The at least one second medium supply opening 48 extending at least through the third semiconductor layer 46 is formed such that it opens into the associated second recess 42a and 42b. As can be seen in Fig. 5A, the at least one first medium supply opening 20 can also be formed as an opening extending both through the second semiconductor layer 18 and through the third semiconductor layer 46. In the embodiment of Fig.5A and 5B, the medium supply openings 20 and 48 are designed such that they can be used to introduce a gaseous and / or liquid substance into the respective associated recess 14, 42a and 42b.
[0056] During the introduction of the medium into the at least one first recess 14 (not illustrated here), the medium is also introduced into the at least one second recess 42a and 42b through the at least one second medium supply opening 48. Instead of simultaneously introducing the medium into the at least one first recess 14 and into the at least one second recess 42a and 42b, the medium can also be introduced into the at least one first recess 14 before or after the medium is introduced into the at least one second recess 42a and 42b.
[0057] If desired, the medium can be held in the at least one second recess 42a and 42b until the wall structures 44 projecting into the at least one second recess 42a and 42b are (almost) completely converted into the product 22 of the chemical reaction due to the chemical reaction with the medium. Alternatively, however, the chemical reaction can also be stopped before the wall structures 44 have been completely converted. Optionally, after the chemical reaction has been completed, the product 22 of the chemical reaction can be removed from the at least one second recess 42a and 42b. Alternatively, however, removal of the product 22 of the chemical reaction from the at least one second recess 42a and 42b can also be omitted.
[0058] Fig. 5B shows the intermediate product before closing the at least one second medium supply opening 48, by means of which a liquid-tight and / or gas-tight sealed cavity 50a and 50b is realized at the respective location of the at least one second recess 42a and 42b. The at least one cavity 50a and 50b formed in the second semiconductor layer 18 can be used as a (large-area) cavity region 50b with a reference pressure set therein and / or as a channel structure 50a with a connection to the cavity region 50b, or as a channel structure 50a between two cavity regions. Therefore, the layer structure 28 shown in Fig. 5B can also be advantageously used for a surface micromechanical pressure sensor.
[0059] Optionally, the at least one first medium supply opening 20 can also be closed. However, it should be noted that even if the at least one second medium supply opening 48 is closed, the at least one first medium supply opening 20 can remain open. By appropriately designing the at least one medium supply opening 20, the at least one recess 14 formed in the first semiconductor layer 12 can be used to stress-decouple the layer structure / layer composite produced above the at least one recess 14 if the at least one medium supply opening 20 is not closed.
[0060] Using the method of Figs. 5A and 5B, multiple levels of recesses 14, 42a, and 42b (or cavities 26 and 50) can be realized. It can be seen that the method described here creates a layer structure 28 in which the third semiconductor layer 46 can be advantageously used as a warpage-free membrane.
[0061] In an alternative embodiment, the wall structures 16 in the at least one first recess 14 can also first be at least partially converted into the product 22 of the chemical reaction of the at least one material of the first semiconductor layer 12 with the medium before the at least one first medium supply opening 20 is closed by deposition of a layer, e.g. silicon dioxide. If desired, only then can the plurality of second recesses 40 be structured into the second semiconductor layer 18 such that the second recesses 40 form at least one contiguous second recess 42a and / or 42b in the second semiconductor layer 18. If at least two second recesses 42a and 42b are formed in the second semiconductor layer 18, these can have different heights perpendicular to the second surface 18a of the second semiconductor layer 18.After the subsequent formation of the third semiconductor layer 46, the at least one second medium supply opening 48 is formed such that it extends at least through the third semiconductor layer 46 and opens into the second recess 42a and / or 42b and / or exposes the at least one first medium supply opening 20 in the second semiconductor layer 18. After at least partial conversion of the wall structures 44 in the at least one second recess 42a and 42b into the product 22 of the chemical reaction, the product 22 of the chemical reaction can be removed from the recesses 14, 42a and / or 42b. Alternatively, however, removal of the product 22 of the chemical reaction can also be omitted.The process sequence described above allows for a free choice of the recesses 14, 42a, 42b in which the chemical reaction is triggered by the supply of the medium and the recesses 14, 42a, 42b in which the resulting product 22 is removed. The opening of the medium supply opening 20 and / or 48 and / or the removal of the wall structures 16 and / or 44 can, in particular, also take place during the final process steps. For further process steps of the method of Figs. 5A and 5b, reference is made to the above-explained embodiments of Figs. 1 to 4.
[0062] 5A and 5B thus creates a device with a layer structure 28, at least one first recess 14 / cavity 26 formed in a first semiconductor layer 12 of the layer structure 28, which recess 14 is structured into the first semiconductor layer 12 starting from a first surface 12a of the first semiconductor layer 12 and is at least partially covered on the first surface 12a of the first semiconductor layer 12 by at least one second semiconductor layer 18 of the layer structure 28, and at least one second recess 42a and 42b / cavity 50a and 50b formed in the second semiconductor layer 18 of the layer structure 28, which recess extends into the second semiconductor layer 18 starting from a second surface 18a of the second semiconductor layer 18 directed away from the first semiconductor layer 12. The second semiconductor layer 18 is formed from at least one of the same material as the first semiconductor layer 12.In addition, the at least one second recess 42a and 42b / cavity 50a and 50b formed in the second semiconductor layer 18 is at least partially covered on the second surface 18a of the second semiconductor layer 18 by at least one third semiconductor layer 46 of the layer structure 28 formed from the at least one same material as the first semiconductor layer 12. For the at least one first recess 14, the layer structure has at least one trace of at least one first medium supply opening 20, which extends at least through the second semiconductor layer 18 and the third semiconductor layer 46 and opens at the associated first recess 14. The at least one first medium supply opening 20 can thus be an open medium supply opening 20 or a closed medium supply opening 20, in front of which only its trace is possibly still recognizable.Accordingly, at least one trace of at least one second medium supply opening 48 can also be seen on the layer structure 28 for the at least one second recess 42a and 42b, which extends at least through the third semiconductor layer 46 and opens into the associated second recess 42a and 42b. The at least one second medium supply opening 48 can also be open or closed, in particular, only recognizable as a trace.
[0063] It is again pointed out that all of the methods explained above can be carried out using silicon, such as in particular monocrystalline or polycrystalline silicon, for the at least two semiconductor layers 12, 18, and 46. In this case, thermal oxidation can be achieved using oxygen as a medium to chemically convert the wall structures 16 and 44 into silicon dioxide. However, it is again pointed out that the materials mentioned here are to be interpreted only as examples of the feasibility of the methods explained above.
[0064] Furthermore, the layer structure 28 shown in the figures can be expanded as desired with additional layers / conductor track levels. By reclosing the at least one medium supply opening 48, e.g., by means of a laser, a capacitive or piezoresistive pressure sensor can be produced using the semiconductor layer 46 and the additional layers / conductor track levels, for example, in whose cavity 50b any desired internal pressure and a freely selectable (preferably gaseous) medium are enclosed. By means of the at least one recess 14 in the first semiconductor layer 12 with at least one open medium supply opening 20, the sensitive region of the pressure sensor can be designed to be stress-decoupled from the layer system surrounding the pressure sensor.
[0065] In a further embodiment, the at least one medium supply opening 20 and / or 48 can also be configured such that it completely surrounds a partial area of the supported semiconductor layer 18 and / or 46. Thus, by means of partial or complete thermal oxidation of the wall structures 16 and / or 44, a thermally insulated monocrystalline and / or polycrystalline silicon surface can be created, which can be used, for example, for the production of radiation detectors. Components thermally insulated in this way can be electrically connected via electrically conductive tracks that span the at least one medium supply opening 20 and / or 48.
Claims
Claims 1. Method for forming a layer structure (28) surrounding at least one recess (14, 14a, 14b, 42a, 42b) comprising the steps: Structuring a plurality of first depressions (10) into a first semiconductor layer (12) of the subsequent layer structure (28) starting from a first surface (12a) of the first semiconductor layer (12) such that the first depressions (10) form at least one connected first recess (14, 14a, 14b) in the first semiconductor layer (12) comprising several first depressions (10), into which first wall structures (16) structured out of the first semiconductor layer (14, 14a, 14b) by means of the first depressions (10) project; Covering at least one first recess (14, 14a, 14b) on the first surface (12a) of the first semiconductor layer (12) at least partially by forming at least one second semiconductor layer (18) from the same material as the first semiconductor layer (12), wherein at least one first medium supply opening (20) is formed for the at least one first recess (14, 14a, 14b), which extends at least through the second semiconductor layer (18) and opens at the associated first recess (14, 14a, 14b); and Introducing a medium through the at least one first medium supply opening (20) into the at least one first recess (14, 14a, 14b), which chemically reacts with the projecting wall structures (16); and 2. Method according to claim 1, wherein a product (22) of the chemical reaction of the medium with the first wall structures (16) is removed from the at least one first recess (14, 14a, 14b).
3. The method of claim 2, wherein the first wall structures (16) that are at least partially converted into the product (22) of the chemical reaction due to the chemical reaction with the medium are used for at least one further process carried out between the introduction of the medium and the removal of the product (22) of the chemical reaction. Support structures are used to support at least the second semiconductor layer (18). A method according to one of the preceding claims, wherein the medium is introduced into and / or retained in the at least one first recess (14, 14a, 14b) until the first wall structures (16) projecting into the at least one first recess (14, 14a, 14b) are completely converted into the product (22) of the chemical reaction due to the chemical reaction of the medium with the first wall structures (16).A method according to any one of the preceding claims, wherein the first wall structures (16) projecting into the at least one first recess (14, 14a, 14b) are used as support structures for supporting at least the second semiconductor layer (18) in at least one further process carried out between the at least partial covering of the at least one first recess (14, 14a, 14b) on the first surface (12a) of the first semiconductor layer (12) and the introduction of the medium. A method according to any one of the preceding claims, wherein at least the following steps are carried out between the at least partial covering of the at least one first recess (14, 14a, 14b) on the first surface (12a) of the first semiconductor layer (12) and the introduction of the medium: - Structuring a plurality of second depressions (40) into the second semiconductor layer (18) such that, starting from a second surface (18a) of the second semiconductor layer (18) directed away from the first semiconductor layer (12), the second depressions (40) form at least one contiguous second recess (42a, 42b) in the second semiconductor layer (18) comprising several second depressions (40), into which second wall structures (44) structured from the second semiconductor layer (18) by means of the second depressions (40) project; and - Covering at least one second recess (42a, 42b) on the second surface (18a) of the second semiconductor layer (18) at least partially, by forming at least a third semiconductor layer (46) of the same material as the first semiconductor layer (12), wherein at least a second medium supply opening (48) is formed for the at least one second recess (42a, 42b), which extends at least through the third semiconductor layer (46) and opens at the associated second recess (42a, 42b); wherein the medium is also introduced through the at least one second medium supply opening (48) into the at least one second recess (42a, 42b), method according to one of the preceding claims, wherein the at least one first medium supply opening (20) and / or the at least one second medium supply opening (48) are closed in such a way that at the location of the at least one first recess (14, 14a, 14b) and / or the at least one second recess (42a, 42b) there is a liquid-tight and / or gas-tight sealed cavern (26, 26a, 26b, 50a, 50b).A method according to claim 7, wherein the sealing of the at least one first medium supply opening (20) and / or the at least one second medium supply opening (48) is carried out by laser melting of the second semiconductor layer (18) and / or the third semiconductor layer (46). A method according to claim 7 or 8, wherein the first wall structures (16), which are at least partially converted into the product (22) of the chemical reaction due to the chemical reaction with the medium, are used as support structures for at least one further process carried out between the introduction of the medium and the sealing of the at least one first medium supply opening (20), to support at least the second semiconductor layer (18).A method according to any of the preceding claims, wherein the second semiconductor layer (18) is formed by growing the second semiconductor layer (18) of monocrystalline or polycrystalline silicon on the first surface (12a) of the first semiconductor layer (12) of monocrystalline or polycrystalline silicon. Device comprising: a layer structure (28); and at least one first recess (14, 14a, 14b) formed in a first semiconductor layer (12) of the layer structure (28), each of which comprises a plurality of first depressions (10) structured into the first semiconductor layer (12) starting from a first surface (12a) of the first semiconductor layer (12), and which form at least one connected recess (14, 14a, 14b) in the first semiconductor layer (12) comprising several first depressions (10); wherein the at least one first recess (14, 14a, 14b) on the first surface (12a) of the first semiconductor layer (12) is at least partially covered by at least one second semiconductor layer (18) formed from the same material as the first semiconductor layer (12), wherein the layer structure (28) for the at least one first recess (14, 14a, 14b) has at least one trace of at least one first medium supply opening (20),which extends at least through the second semiconductor layer (18) and terminates at the associated first recess (14, 14a, 14b), and wherein the layer structure (28) has at least remnants of first wall structures (16) projecting into the at least one first recess (14, 14a, 14b), which are structured out of the first semiconductor layer (12) by means of the first depressions (10) and are at least partially converted into a product (22) of a chemical reaction of the at least one material of the first semiconductor layer (12) with a medium. Device comprising: a layer structure (28); at least one first recess (14, 14a, 14b) formed in a first semiconductor layer (12) of the layer structure (28), which extends from a first surface (12a) of the first semiconductor layer (12) into the, first semiconductor layer (12) is structured, and which is at least partially covered on the first surface (12a) of the first semiconductor layer (12) by means of at least one second semiconductor layer (18) of the layer structure (28) formed from at least one material of the same type as the first semiconductor layer (12); and at least one second recess (42a, 42b) formed in the second semiconductor layer (18), which is structured into the second semiconductor layer (18) starting from a second surface (18a) of the second semiconductor layer (18) directed away from the first semiconductor layer (12), and which is at least partially covered on the second surface (18a) of the second semiconductor layer (18) by means of at least one third semiconductor layer (46) of the layer structure (28) formed from at least one material of the same type as the first semiconductor layer (12);wherein the layer structure (28) for the at least one first recess (14, 14a, 14b) has at least one trace of at least one first medium supply opening (20) which extends at least through the second semiconductor layer (18) and the third semiconductor layer (46) and terminates at the associated recess (14, 14a, 14b), and wherein the layer structure (28) for the at least one second recess (42a, 42b) has at least one structure of at least one second medium supply opening (48) which extends at least through the third semiconductor layer (46) and terminates at the associated second recess (42a, 42b).