Method for manufacturing micromechanical structures and micromechanical structures

Abstract

The invention proposes a method for manufacturing a micromechanical structure and a micromechanical structure. The method comprises the following steps: forming a first micromechanical functional layer (5); forming a plurality of trenches (7) in the first micromechanical functional layer (5), the trenches having an upper region (7a) with a widening at an upper side (O) of the first micromechanical functional layer (5) and a lower region (7b) with a substantially constant width; depositing a sealing layer (8) on the upper side (O) of the first micromechanical functional layer (5) for sealing the plurality of trenches (7), wherein a sealing point (P) of the plurality of trenches (7) is formed below the upper side (O) of the first micromechanical functional layer (5) and at least partially fills a first trench (7); thinning the sealing layer (8) by a predefined thickness (d); forming a second micromechanical functional layer (13) above the thinned sealing layer (8').

Description

Technical Field

[0001] This invention relates to a method for manufacturing micromechanical structures and a micromechanical structure. Background Technology

[0002] Although any micromechanical component can be applied, this invention and the problem on which it is based are explained based on acceleration and rotation sensors.

[0003] DE 10 2011 080 978 A1 discloses a method for topographically structuring MEMS functional layers. This known method is typically used to arrange multiple MEMS functional layers one above the other. Here, a narrow, vertical first trench is etched in a first MEMS functional layer made of silicon. The first trench is then filled with oxide by a first oxide deposition. In a further step, a narrow second trench is etched in the first oxide layer, and silicon from the first MEMS functional layer is etched between each pair of first trenches using isotropic etching steps. The narrow second trench in the first oxide layer is sealed by a second oxide deposition. A second MEMS functional layer made of silicon is deposited on the now flat second oxide layer. Two oxide layers between the two MEMS functional layers are typically removed using a sacrificial layer etching method. In this method, the two functional layers can be structured independently of each other. Furthermore, the thickness of the first MEMS functional layer can be selected independently of the thickness of the second MEMS functional layer.

[0004] However, the spacing between the first and second MEMS functional layers is determined by two oxide deposits. These two oxide deposits must be chosen to be thick enough to fill both the first and second trenches.

[0005] Therefore, the thickness of the first oxide deposition is coupled to the width of the first trench that must be filled by the first oxide deposition. The minimum width of the first trench is technically determined by the minimum representable trench width in the first MEMS functional layer. For thin MEMS functional layers, the minimum width is determined by the minimum resolution of the photolithography process. For thick MEMS functional layers, the minimum width is determined by the trench-prozess process, which is determined by the maximum ratio of trench height to trench width.

[0006] The thickness of the second oxide deposition is not coupled to the thickness of the first MEMS functional layer, but is coupled to the opening width of the narrow second trench in the first oxide layer through the thickness of the first oxide layer, and therefore can be selected to be relatively low in the case of a thin first oxide layer.

[0007] For some applications, the first groove serves as a functional gap to facilitate the fabrication of capacitive sensing or capacitive actuation structures for accelerometers or speed sensors. Therefore, it is generally desirable not to implement the first groove with a minimum width, but rather with a slightly wider width, and for some applications, also with a variable width (e.g., a contour groove). Summary of the Invention

[0008] This invention proposes a method for manufacturing micromechanical structures, the method comprising the following steps:

[0009] Forming the first micromechanical functional layer;

[0010] Multiple trenches are formed in the first micromechanical functional layer. These trenches have an expanded upper region at the upper side of the first micromechanical functional layer and a lower region having a substantially constant width.

[0011] A sealing layer is deposited on the upper side of the first micromechanical functional layer to seal a plurality of trenches, wherein sealing points of the plurality of trenches are formed below the upper side of the first micromechanical functional layer and at least partially fill the first trenches.

[0012] Reduce the sealing layer to a predetermined thickness;

[0013] A second micromechanical functional layer is formed on top of the thinned sealing layer.

[0014] The present invention also proposes a micromechanical structure having:

[0015] First micromechanical functional layer;

[0016] Multiple trenches in a first micromechanical functional layer, the trenches having an expanded upper region at the upper side of the first micromechanical functional layer and a lower region having a substantially constant width.

[0017] A sealing layer on the upper side of the first micromechanical functional layer is provided for sealing a plurality of trenches, wherein sealing points of the plurality of trenches are formed below the upper side of the first micromechanical functional layer, and the first trenches are at least partially filled.

[0018] A second micromechanical functional layer above the sealing layer.

[0019] Preferred extension schemes are described below.

[0020] Advantages of the present invention

[0021] The idea behind this invention is to reliably fill the trenches in the first MEMS functional layer with a thin sealing layer in the vertical direction, which is particularly suitable for applications with limited uniformity. Layer deposition.

[0022] The basic idea is to use a special trench geometry with an open cup (Kelch) in the upper region of the trench. In this upper region, more sealing material (e.g., oxide) is initially needed to achieve a seal. However, the sealing point (where the sealing material co-grows) is located deeper and can be achieved through a suitable geometry: the sealing point is located within the cup below the upper side of the MEMS functional layer. This allows for the thinning of the sealing material after layer deposition via, for example, a CMP process. Because the sealing point is located below the upper side, the trench reliably maintains a seal, and ideally, the oxide thickness can be reduced to almost zero.

[0023] Therefore, wider trenches can be filled with sealing material. The gap between two MEMS functional layers can be configured to be low. Sealing material deposition methods with low or fluctuating consistency can be used for sealing. Trench sealing can be robustly configured and can reliably fill trenches of different widths.

[0024] According to a preferred extension scheme, when forming multiple trenches, a mask layer is formed on the upper side of the first micromechanical functional layer. This mask layer has mask openings corresponding to the multiple first trenches to be formed, wherein the width of the mask openings corresponds to a substantially constant width of the multiple trenches to be formed in the lower region. An isotropic etching process is performed to form a widened upper region on the upper side of the first micromechanical functional layer, wherein the mask openings are etched. An anisotropic etching process is performed to form a lower region with a substantially constant width, and the mask layer is removed. This allows trenches with the desired geometry to be formed.

[0025] According to another preferred extension, a polishing stop layer is formed on the upper side of the first micromechanical functional layer. This polishing stop layer has openings corresponding to a plurality of trenches to be formed, wherein the width of the openings corresponds to the width of the plurality of trenches to be formed on the upper side in the upper region. A mask layer is formed on the polishing stop layer, wherein the mask openings are correspondingly offset relative to the openings. This allows for precise and defined removal of the sealing layer thereafter.

[0026] According to another preferred extension, when forming multiple trenches, a polishing stop layer is formed on the upper side of the first micromechanical functional layer. This polishing stop layer has openings corresponding to the multiple trenches to be formed, wherein the width of the openings corresponds to the width of the multiple trenches to be formed in the upper region on the upper side. A mask layer is formed on the polishing stop layer, having mask openings corresponding to the multiple trenches to be formed, wherein the width of the mask openings corresponds to a substantially constant width of the multiple trenches to be formed in the lower region, and the mask openings are correspondingly offset relative to the openings. An anisotropic etching process is performed to form the lower region with a substantially constant width. The mask layer is removed, and an isotropic etching process is performed to form a widened upper region on the upper side of the first micromechanical functional layer, wherein the polishing stop layer serves as a mask. Thus, trenches with desired geometries can be formed in an alternative method.

[0027] According to another preferred extension, a sealing layer is deposited on the polishing stop layer, wherein the sealing layer is thinned to a predetermined thickness until the polishing stop layer is reached. This allows for precise and defined removal of the sealing layer subsequently, in alternative methods used for trench formation.

[0028] According to another preferred extension, after thinning, the polishing stop layer is removed, the thinned sealing layer is further thinned until the top side, and an intermediate layer is deposited on the top side and the further thinned sealing layer before forming the second micromechanical functional layer on the further thinned sealing layer. With the help of the intermediate layer, the spacing between the first and second micromechanical functional layers can be set independently of the sealing layer.

[0029] According to another preferred extension, as a further step, the following is performed: a first isolation layer is formed over a substrate; a first micromechanical functional layer is formed on the first isolation layer; first etch channels are formed in a thinned sealing layer, these first etch channels partially exposing the first micromechanical functional layer; the first micromechanical functional layer is etched through the etch channels, wherein trenches and the first isolation layer serve as etch stops; and after etching, a second isolation layer is formed on the thinned sealing layer, wherein the etch channels are sealed. Thus, the first micromechanical functional layer can be structured after the trenches are sealed by the sealing layer.

[0030] According to another preferred extension, as a further step, the following is performed: a first isolation layer is formed over a substrate; a first micromechanical functional layer is formed on the first isolation layer; first etch channels are formed in an intermediate layer, these first etch channels partially exposing the first micromechanical functional layer; the first micromechanical functional layer is etched through the etch channels, wherein trenches and the first isolation layer serve as etch stops; and after etching, a second isolation layer is formed on the intermediate layer, wherein the etch channels are sealed. Thus, when the intermediate layer is used, the first micromechanical functional layer can be structured after the trenches are sealed by the sealing layer.

[0031] According to another preferred extension, as a further step, the following is performed: a second micromechanical functional layer is formed over the second isolation layer, and second etch channels are formed in the second micromechanical functional layer to partially expose the second isolation layer. The first and second isolation layers, along with the thinned sealing layer, are selectively etched relative to the first and second micromechanical functional layers to remove the first isolation layer down to the remaining areas that anchor the first micromechanical functional layer to the substrate. Thus, the sealing layer can function as a sacrificial layer.

[0032] According to another preferred extension, as a further step, the following is performed: a second micromechanical functional layer is formed over the second isolation layer, and second etch channels are formed in the second micromechanical functional layer, these second etch channels partially exposing the second isolation layer; the first and second isolation layers, the thinned sealing layer, and the intermediate layer are selectively etched relative to the first and second micromechanical functional layers, wherein the first isolation layer is removed down to the remaining area, these remaining areas anchoring the first micromechanical functional layer to the substrate. Thus, the sealing layer can additionally serve as a sacrificial layer.

[0033] According to another preferred extension, the first groove has rounded edges and / or intersections with localized contractions. This allows for a constant groove width even at the edges and intersections.

[0034] According to another preferred extension, the sealing layer and / or intermediate layer is selected from the group consisting of oxide layers, silicon nitride layers, silicon oxynitride layers, silicon layers, aluminum layers, germanium layers, titanium layers, tungsten layers, copper layers, or combinations of the aforementioned layers. Attached Figure Description

[0035] Other features and advantages of the invention are described below with reference to the accompanying drawings and embodiments.

[0036] The attached diagram shows:

[0037] Figure 1a(1g) shows schematic cross-sectional views for illustrating the micromechanical structure and corresponding manufacturing method according to a first embodiment of the present invention;

[0038] Figure 2a (1) to (2) show schematic cross-sectional views for illustrating the micromechanical structure and corresponding manufacturing method according to a second embodiment of the present invention;

[0039] Figure 3a 3a to 3c) show schematic cross-sectional views for illustrating the micromechanical structure and corresponding manufacturing method according to a third embodiment of the present invention;

[0040] Figure 4a 4a to 4e) show schematic diagrams illustrating preferred trench shapes in embodiments of the invention, more specifically, Figure 4a (This shows a cross-sectional view and) Figure 4b ) to 4e) show the top view;

[0041] Figure 5a (5h) shows schematic cross-sectional views for illustrating the micromechanical structure and corresponding manufacturing method according to the fourth embodiment of the present invention;

[0042] In the accompanying drawings, the same reference numerals denote the same or functionally identical elements. Detailed Implementation

[0043] Figure 1a (1g) are schematic cross-sectional views used to illustrate the micromechanical structure and corresponding manufacturing method according to the first embodiment of the present invention.

[0044] exist Figure 1a In the figure, reference numeral 5 indicates a micromechanical functional layer, such as a polysilicon layer, which is applied, for example, to a substrate (not shown).

[0045] In the micromechanical functional layer 5, a plurality of trenches 7 are first formed. These trenches have a cup-shaped, widened upper region 7a at the upper side O of the first micromechanical functional layer 5 and a lower region 7b, which has a substantially constant width, as further explained below. For the sake of simplicity, only one trench 7 of the plurality of trenches 7 is shown below.

[0046] Further reference Figure 1a First, a mask layer 6, such as a photoresist mask, is formed on the upper side of the first micromechanical functional layer 5. This mask layer has mask openings 6a corresponding to the plurality of first trenches 7 to be formed. The width b of the mask openings 6a corresponds to the substantially constant width of the plurality of trenches 7 to be formed in the lower region 7b.

[0047] Reference Figure 1b First, an isotropic etching process is performed to form a widened upper region 7a at the upper side O of the first micromechanical functional layer 5, wherein the mask opening 6a is etched.

[0048] Next, according to Figure 1c An anisotropic etching process is then performed to form a lower region 7b with a substantially constant width. The mask layer 6 is then removed again.

[0049] Typically, the width b in the upper cup-shaped region 7a widens by at least 10% towards the surface O.

[0050] The etching process for trench 7 is preferably a cyclic etching process consisting of at least two repeated steps. In the first step, silicon is etched primarily isotropically, and a passivation layer is opened at the bottom of trench 7 through anisotropic etching portions.

[0051] In the second step, passivation is deposited primarily isotropically across the entire surface of trench 7. To create the cup-shaped upper region 7a, for example, it is desirable to begin the trench etching process with an isotropic silicon etching process, and to etch at least 50% more silicon in the first cycle than on average across all silicon etching cycles. Specifically, the first silicon etching cycle and possibly some other silicon etching cycles are performed such that the upper region is widened by at least 10% relative to the width b.

[0052] Next, refer to Figure 1d A sealing layer 8 (e.g., an oxide layer) is deposited on the upper side O of the first micromechanical functional layer 5 to seal the multiple trenches. Here, at least 50% of the width b is typically deposited as the thickness of the sealing layer 8. The deposition method is a non-uniform deposition method, which typically creates voids V inside the sealing trenches 7. The trenches 7 are filled to such an extent that the trench walls are covered with the sealing layer 8 and the sealing points P of the multiple trenches 7 are located below the upper side O of the first micromechanical functional layer 5, which is important for subsequent process steps.

[0053] The effective minimum opening angle of the upper region 7a is usually greater than the arctangent of 1 (consistency of deposition process), where consistency is the ratio of the deposition rate on the horizontal upper side O to the deposition rate at the vertical wall of the trench 7.

[0054] according to Figure 1e The deposition continues to such an extent that the sealing layer 8 extends beyond the upper side O.

[0055] Further reference Figure 1fThe sealing layer 8 is thinned to a predetermined thickness d, preferably using a CMP (chemical mechanical polishing) process. Preferably, a CMP process with endpoint identification is used to achieve a defined remaining thickness, or a defined thickness removal d, which results in... Figure 1f The process status shown in the figure.

[0056] In a further process step, this process step is in Figure 1g As shown in the figure, a second micromechanical functional layer 13, such as a polycrystalline silicon layer, is deposited on the thinned sealing layer 8'.

[0057] By following the process step sequence from Figure 1) to 1g), a stack of the first micromechanical functional layer 5 and the second micromechanical functional layer 13, and the thinned sealing layer 8' located therebetween, can be generated without topographic structure, which enables a very low gap between the two micromechanical functional layers 5 and 13.

[0058] Then, in a further (not shown) process step, the second micromechanical functional layer 13 can be structured, and the sealing layer 8' can be partially or completely removed in a sacrificial layer etching method.

[0059] Figure 2a (1) to (2h) are schematic cross-sectional views used to illustrate the micromechanical structure and corresponding manufacturing method according to the second embodiment of the present invention.

[0060] Reference Figure 2a First, a polishing stop layer 20 is formed on the upper side O of the first micromechanical functional layer 5. The polishing stop layer 20 has an opening 21 corresponding to the plurality of grooves 7 to be formed. The width b' of the opening corresponds to the width of the plurality of grooves 7 to be formed on the upper side in the widened upper region 7a.

[0061] Of particular advantage is that the silicon nitride layer serves as the polishing stop layer 20. The silicon nitride layer is particularly well suited for oxide CMP processes due to its high selectivity, and can also be removed very selectively relative to the oxide layer serving as the sealing layer 7, for example, using phosphoric acid.

[0062] Further reference Figure 2b A mask layer 6 is formed on the polishing stop layer 20, wherein the mask layer 6 has mask openings corresponding to a plurality of grooves 7 to be formed, the width b of which corresponds to a substantially constant width of the plurality of grooves 7 to be formed in the lower region. The mask openings 6a are offset relative to the openings 21 accordingly, particularly offset by a distance x on both sides, wherein the relationship 2x + b = b' applies.

[0063] Then in Figure 2bAs shown in the process diagram, an isotropic etching process is first performed to form a lower region 7b with a substantially constant width. Next, the mask layer 6 is removed, as shown in... Figure 2c As shown in ), then refer to Figure 2d An isotropic etching process is performed to form an expanded upper region 7a at the upper side O of the first micromechanical functional layer 5, wherein the polishing stop layer 20 serves as a mask.

[0064] As in Figure 2e As shown in the diagram, the sealing layer 8 is then deposited on the polishing stop layer 20 using a non-uniform deposition process. As in the first embodiment, the deposition process continues until the sealing layer 8 extends beyond the upper side O of the first micromechanical functional layer 5, wherein the sealing point P is located below the upper side O, as shown in the diagram. Figure 2f As shown in the figure.

[0065] Further reference Figure 2g For example, the sealing layer 8 is thinned down to the polishing stop layer 20 by CMP process and a pre-given thickness d'.

[0066] Next, refer to Figure 2h The second micromechanical functional layer 13 (e.g., a polysilicon layer) is deposited, and possible further process steps are performed, as mentioned in conjunction with the first embodiment.

[0067] Furthermore, in a variation of the first embodiment, a polishing stop layer 20 having an opening 21 can also be used.

[0068] Figure 3a 3a to 3c) are schematic cross-sectional views used to illustrate the micromechanical structure and corresponding manufacturing method according to the third embodiment of the present invention.

[0069] The third embodiment is a variation of the second embodiment, wherein, in Figure 2g After the process state shown in the figure, the polishing stop layer 20 is removed after thinning, as shown in the figure. Figure 3a As shown in the figure, selective removal is achieved, for example, by means of phosphoric acid.

[0070] Further reference Figure 3b The thinned sealing layer 8' is further thinned until it reaches the upper side O, so that the further thinned sealing layer 8' now extends flush with the upper side O of the first micromechanical functional layer 5.

[0071] Next, refer to Figure 3c An intermediate layer 8” is deposited on the upper side O and the further thinned sealing layer 8’, the thickness of which can be set to any low. The intermediate layer 8” is, for example, also an oxide layer.

[0072] Finally, according to Figure 3c A second micromechanical functional layer 13 is deposited on the intermediate layer. Further process steps—as described above—can then be performed on... Figure 3c The process is carried out as shown in the diagram.

[0073] Figure 4a (4) to (4e) are schematic diagrams illustrating preferred groove shapes in embodiments of the present invention, more specifically, Figure 4a ) is a cross-sectional view and Figure 4b ) to 4e) are top views.

[0074] Figure 4a ) and according to Figure 1a The diagram corresponds to this. Figure 4b The image shows a top view of the mask layer 6, where the trench 7 has a right-angled angle 20. However, according to... Figure 4c For the proposed method, it is preferable that the corner 20 has a rounded portion 21, thereby having a constant groove width.

[0075] Accordingly, Figure 4d As shown, trench 7 has right-angled branches 22. However, according to Figure 4e For the proposed method, it is preferable that branch 22 has a local contraction portion 23, so that the groove width remains constant.

[0076] Figure 5a (5h) are schematic cross-sectional views used to illustrate the micromechanical structure and corresponding manufacturing method according to the fourth embodiment of the present invention.

[0077] Reference Figure 5a A basic isolation layer 2 is deposited on a silicon substrate 1. Optionally, this basic isolation layer 2 can now be structured to, for example, connect the nearest functional layer located above it to the substrate 1. Optionally, one or more functional layers 3, for example made of polycrystalline silicon, can then be deposited and structured. Then, in a further process, a first isolation layer 4 is deposited on the one or more functional layers 3. This first isolation layer 4 serves as a sacrificial layer, isolation layer, or anchoring layer in further processes. Obviously, the first isolation layer 4 can also be structured if necessary to establish electrical and / or mechanical contacts with the nearest functional layer located above it.

[0078] In a further process, a first micromechanical functional layer 5 is deposited on the first isolation layer 4. This can be performed, for example, by LPCVD or by a combination of an LPCVD initiation layer and an epitaxial layer made of polysilicon located above the LPCVD initiation layer. The first micromechanical functional layer 5 made of polysilicon can then be planarized optionally by a polishing method (CMP = Chemical-Mechanical Polishing). Depending on the substructure or thickness of the first micromechanical functional layer 5, this may be necessary to obtain sufficiently good lithographic resolution in subsequent steps.

[0079] Further reference Figure 5b A mask layer 6 is provided on the first micromechanical functional layer 5, the mask layer having an opening 6a, by means of which the polysilicon of the first micromechanical functional layer 5 located below it should be slotted in a subsequent process step, as has been described in conjunction with the first to third embodiments.

[0080] Optionally, additional settings can be configured to combine Figure 2a The polishing stop layer 20 described in ( ) to 2h)

[0081] Figure 5c This illustrates the process state after the grooving step, in which trenches 7 are formed in the first micromechanical functional layer 5, extending to the first isolation layer 4. This is, for example, consistent with... Figure 1c Corresponding to the process state, if a polishing stop layer 20 is additionally set, then it can also be performed according to... Figure 2a The process steps from 2d to 2d, wherein, then, in Figure 5c In the process, the polishing stop layer replaces the mask layer 6.

[0082] Reference Figure 5d Remove mask layer 6, and then proceed according to... Figure 1d The process steps from 1f) to 1f) can be performed. Alternatively, the process steps can be performed according to... Figure 2e The process steps from 100g to 2g, or the following steps... Figure 2g ) Execution based on Figure 3a The process steps from 3c) are used to fill the groove 7 and form a thinned sealing layer 8' or intermediate layer 8".

[0083] Then, according to Figure 5e Etched channels 9 are formed in the sealing layer 8' or the intermediate layer 8', which partially expose the first micromechanical functional layer 5. The width of these first etched channels 9 is chosen such that they can be completely sealed again by subsequent oxide deposition, which will be described later.

[0084] As in Figure 5fAs shown in the diagram, the notch 10 is then etched into the first micromechanical functional layer 5 in an etching step. Preferably, an isotropic method is used for this purpose. Vapor phase methods have proven particularly advantageous because it can be difficult to flush the liquid etching medium out of the etched area again through the narrow first etching channel 9. An exemplary method is an etching process using SF6 in plasma or using ClF3 or XeF2. In this etching of the first micromechanical functional layer, the first trench 7 filled with oxide and the first isolation layer 4 located below it serve as an etching stop. In other partial areas, the etching of the polysilicon of the first micromechanical functional layer 5 can be limited by the etching time. Similarly, a second isolation layer 8 made of oxide, deposited in the narrow trench 7, can be used to stabilize the layer. In the case of such a large area, it is additionally advantageous to construct the etching channel 9 in the second sealing layer 8' or intermediate layer 8' in such a way that the stress in the layer can be reduced by the geometric arrangement of the etching channel. For example, the bending of the etching channel 9 can be used. Arrangement of long, mutually offset etched channels 9.

[0085] Further reference Figure 5f Another isolation layer 11 made of oxide is deposited to seal the etched channels 9 in the sealing layer 8' or intermediate layer 8'. The sealing layer 8' or intermediate layer 8' together with the other isolation layer 11 forms another sacrificial layer and isolation layer. In particular, by the described manufacturing method, no substantial morphological structure is produced at the location where the first micromechanical functional layer 5 has been etched.

[0086] As in Figure 5g As shown in the diagram, one or more contact areas K of the first micromechanical functional layer 5 are then exposed by removing the second sealing layer 8' or intermediate layer 8" and the isolation layer 11 at the relevant locations via an etching process. These contact areas K define connections to other micromechanical functional layers 13 subsequently deposited from polysilicon.

[0087] Then, the second micromechanical functional layer 13 is structured in a manner known per se to form second etch channels 14, which partially expose the isolation layer 11, as shown in Figure 5g As shown in the figure.

[0088] Finally, refer to Figure 5h Further etching processes are performed to completely remove the sealing layer 8' or intermediate layer 8" and the isolation layer 11, and to remove the first isolation layer 4 down to the remaining region R, where the first micromechanical functional layer 5 is anchored to the substrate 1.

[0089] Although the invention has been described based on preferred embodiments, the invention is not limited thereto. In particular, the materials and topologies mentioned are merely exemplary and are not limited to the illustrated examples.

[0090] Its applications are also wide-ranging and not limited to acceleration and rotation speed sensors, but can be used in any micromechanical sensor, especially capacitive pressure sensors, for example.

[0091] Previously, it was assumed that oxide deposition was used to fill trenches; however, the described invention is not limited to oxide deposition, and the invention can be applied to any deposition capable of sealing trenches. The invention is particularly applicable to the deposition of SiN (silicon nitride), SiRiN (silicon-rich nitride), SiON (silicon oxynitride), Si (silicon), Al (aluminum), Ge (germanium), Ti (titanium), W (tungsten), Cu (copper), etc.

Claims

1. A method for manufacturing micromechanical structures, the method comprising the following steps: Forming the first micromechanical functional layer (5); Multiple trenches (7) are formed in the first micromechanical functional layer (5), the trenches having an expanded upper region (7a) at the upper side (O) of the first micromechanical functional layer (5) and a lower region (7b) having a substantially constant width. A sealing layer (8) is deposited on the upper side (O) of the first micromechanical functional layer (5) to seal the plurality of trenches (7), wherein, Sealing points (P) of the plurality of grooves (7) are formed below the upper side (O) of the first micromechanical functional layer (5), and the first groove (7) is at least partially filled; The sealing layer (8) is thinned to a predetermined thickness (d; d'); A second micromechanical functional layer (13) is formed above the thinned sealing layer (8'). The formation of the plurality of trenches (7) includes the following steps: A mask layer (6) is formed on the upper side (O) of the first micromechanical functional layer (5), the mask layer having a mask opening (6a) corresponding to a plurality of first trenches (7) to be formed, wherein the width (b) of the mask opening (6a) corresponds to a substantially constant width of the plurality of trenches (7) to be formed in the lower region (7b). An isotropic etching process is performed to form the widened upper region (7a) on the upper side (O) of the first micromechanical functional layer (5), wherein the mask opening (6a) is etched. An anisotropic etching process is performed to form the lower region (7b) having a substantially constant width; Remove the mask layer (6).

2. The method according to claim 1, wherein the method comprises the following steps: A polishing stop layer (20) is formed on the upper side (O) of the first micromechanical functional layer (5), the polishing stop layer having an opening (21) corresponding to the plurality of grooves (7) to be formed, wherein the width (b') of the opening (21) corresponds to the width of the plurality of grooves (7) to be formed on the upper side (O) in the upper region (7a); The mask layer (6) is formed on the polishing stop layer (20), wherein the mask opening (6a) is offset relative to the opening (21).

3. A method for manufacturing micromechanical structures, the method comprising the following steps: Forming the first micromechanical functional layer (5); Multiple trenches (7) are formed in the first micromechanical functional layer (5), the trenches having an expanded upper region (7a) at the upper side (O) of the first micromechanical functional layer (5) and a lower region (7b) having a substantially constant width. A sealing layer (8) is deposited on the upper side (O) of the first micromechanical functional layer (5) to seal the plurality of trenches (7), wherein, Sealing points (P) of the plurality of grooves (7) are formed below the upper side (O) of the first micromechanical functional layer (5), and the first groove (7) is at least partially filled; The sealing layer (8) is thinned to a predetermined thickness (d; d'); A second micromechanical functional layer (13) is formed above the thinned sealing layer (8'). The formation of the plurality of trenches (7) includes the following steps: A polishing stop layer (20) is formed on the upper side (O) of the first micromechanical functional layer (5), the polishing stop layer having an opening (21) corresponding to the plurality of grooves (7) to be formed, wherein the width (b') of the opening (21) corresponds to the width of the plurality of grooves (7) to be formed on the upper side (O) in the upper region (7a); A mask layer (6) is formed on the polishing stop layer (20), the mask layer having a mask opening (6a) corresponding to the plurality of trenches (7) to be formed, wherein the width (b) of the mask opening (6a) corresponds to a substantially constant width of the plurality of trenches (7) to be formed in the lower region (7b), and the mask opening (6a) is offset relative to the opening (21); An anisotropic etching process is performed to form the lower region (7b) having a substantially constant width; Remove the mask layer (6), An isotropic etching process is performed to form the widened upper region (7a) on the upper side (O) of the first micromechanical functional layer (5), wherein the polishing stop layer (20) is used as a mask.

4. The method according to claim 3, wherein, The sealing layer (8) is deposited on the polishing stop layer (20), and the sealing layer (8) is thinned to the predetermined thickness (d') until the polishing stop layer (20).

5. The method according to claim 4, wherein, After the thinning, the polishing stop layer (20) is removed, the thinned sealing layer (8') is further thinned until the upper side (O), and an intermediate layer (8") is deposited on the upper side (O) and the further thinned sealing layer (8') before forming a second micromechanical functional layer (13) on the further thinned sealing layer (8').

6. The method according to any one of claims 1 to 4, wherein the method comprises the further step of: A first isolation layer (4) is formed above the substrate (1); The first micromechanical functional layer (5) is formed on the first isolation layer (4); A first etch channel (9) is formed in the thinned sealing layer (8'), which partially exposes the first micromechanical functional layer (5); The first micromechanical functional layer (5) is etched through the etching channel (9), wherein, The trench (7) and the first isolation layer (4) serve as an etch stop; After the etching, a second isolation layer (11) is formed on the thinned sealing layer (8'), wherein the etched channel (9) is sealed.

7. The method according to claim 5, wherein the method comprises the following further steps: A first isolation layer (4) is formed above the substrate (1); The first micromechanical functional layer (5) is formed on the first isolation layer (4); A first etch channel (9) is formed in the intermediate layer (8), which partially exposes the first micromechanical functional layer (5). The first micromechanical functional layer (5) is etched through the etching channel (9), wherein, The trench (7) and the first isolation layer (4) serve as an etch stop; After the etching, a second isolation layer (11) is formed on the intermediate layer (8"), wherein the etched channel (9) is sealed.

8. The method according to claim 6, wherein, Implement the following further steps: The second micromechanical functional layer (13) is formed above the second isolation layer (11); A second etch channel (14) is formed in the second micromechanical functional layer (13), the second etch channel partially exposing the second isolation layer (11); The first and second isolation layers (4, 11) and the thinned sealing layer (8') are selectively etched relative to the first and second micromechanical functional layers (5, 13) to remove the first isolation layer (4) down to the remaining area (R) which anchors the first micromechanical functional layer (5) onto the substrate (1).

9. The method according to claim 7, wherein, Implement the following further steps: The second micromechanical functional layer (13) is formed above the second isolation layer (11); A second etch channel (14) is formed in the second micromechanical functional layer (13), the second etch channel partially exposing the second isolation layer (11); The first and second isolation layers (4, 11), the thinned sealing layer (8'), and the intermediate layer (8") are selectively etched relative to the first and second micromechanical functional layers (5, 13), wherein the first isolation layer (4) is removed down to the remaining region (R), which anchors the first micromechanical functional layer (5) onto the substrate (1).

10. The method according to any one of claims 1 to 5, wherein, The first groove (7) has rounded edges and / or intersections, and the edges and / or intersections have local contractions (23).

11. The method according to any one of claims 1 to 5, wherein, The sealing layer (8) is selected from the group consisting of oxide layer, silicon nitride layer, silicon oxynitride layer, silicon layer, aluminum layer, germanium layer, titanium layer, tungsten layer, copper layer or a combination of the former layers.

12. The method according to claim 5, wherein, The intermediate layer (8) is selected from the group consisting of oxide layer, silicon nitride layer, silicon oxynitride layer, silicon layer, aluminum layer, germanium layer, titanium layer, tungsten layer, copper layer, or a combination of the preceding layers.

13. A micromechanical structure manufactured by the method according to any one of claims 1 to 12, the micromechanical structure comprising: First micromechanical functional layer (5); The first micromechanical functional layer (5) has a plurality of trenches (7), each trench having an expanded upper region (7a) at the upper side (O) of the first micromechanical functional layer (5) and a lower region (7b) having a substantially constant width. A thinned sealing layer (8') on the upper side (O) of the first micromechanical functional layer (5) is used to seal the plurality of trenches (7), wherein, The sealing points (P) of the plurality of grooves (7) are formed below the upper side (O) of the first micromechanical functional layer (5), and the first groove (7) is at least partially filled; A second micromechanical functional layer (13) above the thinned sealing layer (8').

14. The micromechanical structure according to claim 13, wherein, A polishing stop layer (20) is provided at the upper side (O), the polishing stop layer being laterally adjacent to the thinned sealing layer (8') and extending flush with the sealing layer.

15. A micromechanical structure manufactured by the method according to any one of claims 1 to 12, the micromechanical structure comprising: First micromechanical functional layer (5); The first micromechanical functional layer (5) has a plurality of trenches (7), each trench having an expanded upper region (7a) at the upper side (O) of the first micromechanical functional layer (5) and a lower region (7b) having a substantially constant width. A thinned sealing layer (8') on the upper side (O) of the first micromechanical functional layer (5) is used to seal the plurality of trenches (7), wherein, The sealing points (P) of the plurality of grooves (7) are formed below the upper side (O) of the first micromechanical functional layer (5), and the first groove (7) is at least partially filled; The thinned sealing layer (8') extends flush with the upper side (O) of the first micromechanical functional layer (5); The upper side (O) and the intermediate layer (8") on the thinned sealing layer (8'); The second micromechanical functional layer (13) is located above the intermediate layer (8).

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