Micromechanical structural element
By constructing a reinforcing structure in the diaphragm anchor and connection structure regions of the micromechanical pressure sensor, the problem of diaphragm cracking under high pressure is solved, thereby improving the stability and durability of the sensor.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ROBERT BOSCH GMBH
- Filing Date
- 2021-10-06
- Publication Date
- 2026-08-04
AI Technical Summary
Existing micromechanical pressure sensors are prone to diaphragm cracking under high pressure, especially in low-pressure sensors, where the thin film's instability leads to sensor damage under overload conditions.
Reinforcing structures are constructed in the anchor and connection structures of the diaphragm to enhance the stability of the diaphragm through a defined geometric design. This includes setting reinforcing layers or additional elements in the anchor and/or connection structures, and using materials such as Si, Ge, and SiO2 to optimize the reinforcement effect.
It effectively reduces the stress curve of the diaphragm under high pressure, avoids diaphragm cracks and damage, and improves the robustness and tolerance of the sensor.
Smart Images
Figure CN116615389B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a micromechanical structural element. Furthermore, this invention also relates to a method for manufacturing micromechanical structural elements. Background Technology
[0002] Known micromechanical pressure sensors contain a diaphragm clamped within a frame structure, which can be made, for example, of bulk silicon (single-crystal silicon wafers) or fabricated using OMM (Oberflächen-Mikromechanik) technology. When using OMM, the frame is typically made of polycrystalline silicon.
[0003] A pressure sensor is known from DE 10 2018 222 715 A1, in which the diaphragm clamping part is not composed of a continuously surrounding frame, but is composed of a single anchor structure.
[0004] Especially in the case of low-pressure sensors, thin and / or large diaphragms are used to achieve good measurement sensitivity / response sensitivity. However, the diaphragm must still possess high stability to prevent damage to these sensors under higher pressures (e.g., under overload conditions). High forces can occur under overload conditions, particularly in the clamping areas of the diaphragm or at the edges of the diaphragm reinforcement structure, which could lead to cracks in the diaphragm. Summary of the Invention
[0005] The objective of this invention is to provide a micromechanical structural element that is particularly improved in terms of diaphragms.
[0006] According to the first aspect, this task is solved by means of a micromechanical structural element, which has: - Membrane; among which, - The diaphragm has at least one reinforcing structure in the region of at least one anchor structure and / or in the region of at least one connecting structure, the reinforcing structure being constructed in a defined manner in terms of geometry, by means of the reinforcing structure reinforcing the diaphragm in a defined manner.
[0007] In this way, the diaphragm can be particularly robust with respect to high pressure loads, thereby advantageously minimizing the stress profile within the diaphragm. Consequently, this method can largely prevent, for example, cracks or damage to the diaphragm caused by high pressure loads.
[0008] According to the second aspect, this task is solved by means of a method for manufacturing micromechanical structural components, the method comprising the following steps: - Provide membrane sheets; wherein, - In the diaphragm, at least one reinforcing structure is constructed in the region of at least one anchor structure and / or in the region of at least one connecting structure, the reinforcing structure being constructed in a defined manner in terms of geometry, by means of the reinforcing structure reinforcing the diaphragm in a defined manner.
[0009] Preferred extension schemes for micromechanical structural elements are described below.
[0010] A key advantage of this extension to the micromechanical structural element is that the reinforcing structure is constructed to overlap in a defined manner over at least one anchor structure and / or at least one connecting structure. Advantageously, this allows for further improvement in the reinforcing effect of the reinforcing structure.
[0011] Another advantageous extension of the micromechanical structural element is that the lateral dimension of the protrusion of the reinforcing structure relative to the remaining diaphragm is related to the extent of the overlapping area and / or the thickness of the diaphragm.
[0012] Another advantageous extension of micromechanical structural elements is characterized by reinforcing structures having substantially the same or different lateral dimensions above and below the surface of the diaphragm. This allows for specific dimensional design of each region of the reinforcing structure, thereby further improving its reinforcing effect.
[0013] Another advantageous extension of micromechanical structural elements is that the reinforcing structure is integrally constructed from a single material. In this way, the reinforcing effect of the reinforcing structure can be specified very accurately based on well-known material properties.
[0014] Another advantageous extension of micromechanical structural elements is characterized by the reinforcing structure comprising at least one enclosed additional element. In this way, the reinforcing effect of the reinforcing structure can be further improved through the combined action of two different materials.
[0015] Another advantageous extension of the micromechanical structural element is characterized by at least one additional element being arranged in the region of at least one anchor structure and / or in the region of at least one connecting structure. In this way, the reinforcing effect of the reinforcing structure can be further optimized.
[0016] Another advantageous extension of the micromechanical structural element is that the reinforcing structure is constructed from at least one of the following materials: Si, Ge, SiO2, Si3N4, GeO2, Ge3N4, SiC, Al2O3, and silicon-rich silicon nitride. Advantageously, this allows the use of different materials, each with its own material parameters, to achieve the reinforcing structure, and thus, for example, allows for the use of optimized manufacturing processes to provide the reinforcing structure. Attached Figure Description
[0017] The invention is described in detail below with reference to several accompanying drawings, and by means of other features and advantages. Identical or functionally identical elements have the same reference numerals. These drawings are intended in particular to illustrate principles important to the invention, and are not necessarily illustrated to scale. For clarity, it may be arranged that not all reference numerals are drawn in all drawings.
[0018] As shown in the attached figure: Figure 1 A cross-sectional view of a conventional micromechanical sensor is shown; Figure 2 Show Figure 1 A cross-sectional view of a traditional micromechanical sensor, which has the problem of crack formation; Figure 3 Multiple views of the proposed reinforcement structure of the proposed micromechanical structural element are shown in the clamping region of the diaphragm; Figure 4 This illustrates an alternative variation of the proposed reinforcement structure in the clamping region of the proposed micromechanical structural element; Figure 5 Further variations of the proposed reinforcement structure are shown in the clamping region of the proposed micromechanical structural element; Figure 6 A top view of the proposed reinforcement structure is shown in the clamping region of the diaphragm of the micromechanical structural element; Figure 7 A top view of the proposed reinforcement structure is shown in the clamping region of the diaphragm of the proposed micromechanical structural element. Figure 8 A top view of the proposed reinforcement structure is shown in the clamping region of the proposed micromechanical structural element; Figure 9 A variation of the proposed reinforcement structure is shown in the reinforced region of the diaphragm of the proposed micromechanical structural element; Figure 10 The schematic process for manufacturing the proposed micromechanical structural components is shown. Detailed Implementation
[0019] The core concept of this invention lies particularly in having a diaphragm that specifically reinforces the micromechanical structural elements in the clamping region and / or in the transition region of the diaphragm (e.g., the reinforcement structure) so that cracks are minimized in the diaphragm under overload conditions.
[0020] In the context of this invention, an "anchor structure" can be a plurality of separate anchor structures or anchoring structures, or a continuous, one-piece, or integral anchor region or anchoring region. For simplicity, this distinction will not be made in the following text.
[0021] Figure 1 A cross-sectional view of the conventional micromechanical structure element 100 is shown, which takes the form of a capacitive micromechanical pressure sensor, as is known, for example, from DE 10 2018 222715 A1. A substrate 1 (preferably a silicon substrate, such as a silicon wafer) can be seen, having a layered structure disposed thereon, primarily comprising a functional layer 2 and an upper sacrificial layer 3. Here, clamping of the diaphragm in clamping region 11 is achieved by means of various anchor structures arranged side-by-side. Reinforcement of the diaphragm 10 in the intermediate reinforcement region 12 is achieved by one or more support structures that collectively fix the upper electrode 15 above the lower electrode 16 of the effective capacitance. These support structures are connected to the diaphragm 10 via connecting structures 14, thereby causing localized reinforcement of the diaphragm 10.
[0022] Figure 2 The following scenario is illustrated: In this scenario, a high mechanical pressure F is applied to the diaphragm 10. If this pressure F is too high, in the worst-case scenario, cracks may appear in the clamping region 11 and / or in the reinforced region 12 of the diaphragm 10. The possible locations of this type of crack are indicated by circles drawn with dashed lines.
[0023] To avoid this type of cracking in the diaphragm 10, it is proposed to reinforce the clamping region 11 of the diaphragm 10 in a defined manner, such as... Figure 3 b) – Figure 3 As shown in d).
[0024] Figure 3 a) A cross-sectional view of a conventional anchor structure 13 in the clamping region 11 is shown, as is known, for example, from DE2018 222 715 A1. The anchor structure 13 includes a functional layer 2 (e.g., made of polysilicon) and is in direct contact with the diaphragm 10 or diaphragm layer. Here, the functional layer 2 is arranged within the lower sacrificial layer 4 and within the upper sacrificial layer 3 in a manner that completely penetrates both the lower sacrificial layer 4 and the upper sacrificial layer 3. Different possibilities are considered to enhance the clamping region 11, as described below.
[0025] For example, such as Figure 3 As shown in b), the upper side of the diaphragm 10 can be thickened or reinforced by an additional layer that extends beyond the anchor structure 13, thereby creating a diaphragm reinforcement in the region of the transition between the anchor structure 13 and the diaphragm 10. Preferably, a layer made of polysilicon can be used to fabricate this diaphragm reinforcement in order to, for example, keep the thermal impact on sensor performance low and / or provide good chemical etch stability relative to the etch medium of the sacrificial layer. If the sacrificial layers 3 and 4 are made of, for example, SiO2, the reinforcement layer should have the highest possible etch resistance relative to the etch medium in the form of liquid or gaseous HF. As expressed by means of the equation below, the reinforcement can extend beyond the region or width and length (i.e., the lateral dimension of the anchor structure 13), wherein the corresponding protrusions do not necessarily need to have the same dimensional design.
[0026] The geometric design of the reinforcing structure 20 given below is possible, wherein the term "arbitrary" is understood below as a range of suitable dimensional design parameters (bandbreite) in the context of possible dimensional design parameters of the micromechanical structural element, such as the range of dimensional design parameters for the geometry of the diaphragm. It is considered here that, for example, the thickness of the diaphragm 10 of the micromechanical structural element 100 can be from tens of nm to hundreds of µm.
[0027] a, c>= 0 a = c a>c a <c dV = arbitrary dVU <dO dM = arbitrary a´、c´>= 0 a´ = c´ a´>c´ a´ <c´ a´ = a a´>a a´ c´ = c c´>c c´ <c exist Figure 3 c) shows another variation of the reinforcing structure 20, in which a diaphragm reinforcement can be implemented in the region of the transition between the anchor structure 13 and the diaphragm 10. Here, the reinforcing layer can also be made of silicon and can extend beyond the anchor structure 13. In this case, the protrusions with widths a and c can also be designed with different dimensions. Although in Figure 3 In b), the thickness of the reinforcing layer can be arbitrary, but in Figure 3 In the variation of c), the thickness should be smaller than the thickness of the uppermost sacrificial layer 3 (e.g., made of SiO2), which is located between the film layer and the next functional layer 2 (e.g., made of polycrystalline silicon) located below the film layer.
[0028] Figure 3 d) Shows the result of in Figure 3 b) and Figure 3 The combination constitutes the variant shown in c). In this case, the reinforcing layers are disposed above and below the membrane layer in the region of the anchor structure 13, and the reinforcing layers can extend beyond the anchor structure 13 at different distances. Figure 3 b')- Figure 3 d') shows the corresponding variation of the reinforcement structure 20 after the removal of sacrificial layers 3 and 4.
[0029] Although Figure 3 b')- Figure 3 The variation in d') shows the reinforcement of the diaphragm clamping portion by thickening with the aid of layers; however, in principle, it is also possible to stabilize the clamping region 11 by means of multiple reinforcing layers. Thus, for example, the stress and stress profile in the clamping region 11 of the diaphragm 10 can be influenced and adjusted in a targeted manner.
[0030] Therefore, in Figure 4 a) to Figure 4 Possible variations of the proposed reinforcing structure 20 are shown in section c). Figure 4 In a), for example, a variation is shown in which the additional element or additional layer 5 is integrated into the reinforced region of the diaphragm clamping portion, such as in Figure 3 As shown in b). If the reinforced region is entirely composed of polysilicon, then the additional element 5 or the additional layer is completely surrounded by polysilicon. Here, the thickness of the covering silicon layer can be, for example, the same everywhere, for example, different everywhere, or, for example, only partially the same. The width of the reinforced region is derived by the sum of the overhang width and the width of the anchor structure 13.
[0031] from Figure 3 c) Starting from this, another variation is derived. Here, a reinforcement structure 20 is provided that extends in the clamping region 11 into the region below the diaphragm 10 within the region of the anchor structure 13. One or more additional layers may be integrated into this reinforcement structure, which, similarly to those previously described, are surrounded by silicon, which optionally has different layer thicknesses.
[0032] Figure 4 c) shows a combination of the aforementioned variations. Figure 4 a')- Figure 4c') Again, the corresponding variation of the reinforcement structure 20 after removing the sacrificial layers 3 and 4 is shown.
[0033] Reference Figure 4 a) to Figure 4 The parameters shown in c) should be applicable to: a+b+c>bZ dV+dM>dZ dV+dVu+dM>dZ a´、c´>0 a´ = c´ a´>c´ a´ <c´ a´ = a a´>a a´ c´ = c c´>c c´ <c exist Figure 4 a and Figure 4 As indicated in b, the additional element 5 can be arranged substantially above or below the surface of the diaphragm.
[0034] This also applies Figure 5 a) and Figure 5 b) arrangement, Figure 5 a) and Figure 5 b) Shows relative to Figure 4 Two other variations of (c) are provided, in which the additional element 5 can be arranged substantially above the surface of the diaphragm. Figure 5 a) or below the surface of the membrane ( Figure 5 b)). In Figure 5 a) and Figure 5 As can also be seen in b), an additional reinforcement layer without additional element 5 may exist. If the additional element or additional layer 5 is composed of a layer or layer system that is resistant to the etch medium of the sacrificial layer, it is also possible to partially cover the additional element or additional layer 5 with silicon and omit the need for full coverage. Figure 5 a') and Figure 5 b') Again, the corresponding variation of the reinforcement structure 20 after removing the sacrificial layers 3 and 4 is shown.
[0035] As previously mentioned, in the case of the capacitive pressure sensor mentioned in DE 2018 222 715 A1, the diaphragm clamping part is achieved by a separate, substantially adjacent anchor structure.
[0036] Figure 6 a) A top view showing a segment of the diaphragm 10 of the clamping region 11 described in DE 10 2018 222 715 A1, in which it can be seen that the diaphragm clamping portion is implemented on a separate anchor structure 13.
[0037] Figure 6 b) A top view is shown in which the multiple proposed reinforcement structures 20 are implemented discontinuously, only in regions surrounding a single anchor structure 13. Here, the same premises or assumptions for the reinforcement structures 20 then apply in planes in both directions surrounding the anchor structure 13, as described above. Figure 3 a)- Figure 3 d) and Figure 4 a)- Figure 4 As described in the context of the variant of c).
[0038] Figure 6 c) A top view showing another variation in which the reinforcing structures 20 of adjacent anchor structures 13 at least partially transition into each other, creating a larger, coherent reinforcing area. Figure 6 As shown in c), the reinforcement area can be arranged in the area of anchor structure 13, but it is not necessarily required there. Figure 6 The land is constructed symmetrically as shown in c).
[0039] Alternatively, the reinforcement area can extend asymmetrically away from the anchor structure 13, such as... Figure 6 As shown in d). In extreme cases, the reinforcing structure 20 may be located throughout the entire surface outside the diaphragm region. Here, the diaphragm region may, for example, extend to the reinforcing structure 20 or to the anchor structure 13, or may include the anchor structure 13.
[0040] Figure 7 a)- Figure 7 c) is related to Figure 6 b) Figure 6 d) The corresponding illustration may also include additional elements or additional reinforcing layers 5. Alternatively, it is also possible to construct the reinforcing structure 20 not in a straight line parallel to the diaphragm clamping portion, but in a convex, concave, or otherwise constructed manner along the diaphragm clamping portion.
[0041] exist Figure 8 a)- Figure 8 Example d) shows the ventral (convex) orientation of the reinforcing structure 20 along the clamping region 11. Figure 8 A variation can be seen in a), in which individual, discontinuous reinforcing structures 20 achieve a convex orientation along the diaphragm clamping portion, while... Figure 8 A continuous area can be seen in b). Although in Figure 8 a) Figure 8 b) The ventral reinforcing structure 20 is constructed symmetrically around the anchor structure 13 along the diaphragm clamping portion, but a variation can also be achieved where, for example, the ventral reinforcing structure 20 extends only to the diaphragm region, as in Figure 8 c) Figure 8 As can be seen in d).
[0042] exist Figure 8 As shown in the top view of (c), the outline of the reinforcing structure 20 can extend ventrally from the straight arrangement of the anchor structure 13 into the membrane region, and can be constructed fully from the anchor structure 13 into the surrounding membrane region that is directed away from the membrane.
[0043] exist Figure 8 As shown in the top view of d), the area of the reinforcing structure 20 may be constructed asymmetrically around the anchor structure 13 and may have parallel and / or non-parallel orientations.
[0044] By reinforcing the bending direction of the reinforcing structure 20 in the clamping region 11, the stress curve in the diaphragm surface can be taken into account, and the following region of the diaphragm clamping part can be correspondingly reinforced while minimizing the influence of the reinforcing structure 20 on the diaphragm characteristics: the region is mechanically subjected to a stronger load.
[0045] Figure 9 a)- Figure 9 e) shows the application of the previously described content to the reinforced region 12 of the pressure sensor described in DE 102018 222 715 A1 in the region of effective capacitance.
[0046] Figure 9 a) A conventional reinforced area 12 is shown as an example.
[0047] exist Figure 9 In b), with Figure 3 b) Similarly, the proposed reinforcement structure 20 can be seen, which is discontinuously located on the diaphragm 10 in the region surrounding the connecting structure.
[0048] Figure 9 c) Showing Figure 3 c) Similarly, in this figure, the discontinuous reinforcing structure 20 is located in the region below the diaphragm 10, surrounding the connecting structure.
[0049] Figure 9 d) Shows a combination of the previously described variations. Figure 9e) illustrates a variation in which at least partially adjacent reinforcing structures 20 in the region of connecting structure 14 transition into each other and form a larger, coherent reinforcing surface. In this example, this applies to reinforcing structures 20 above and below the membrane layer. However, this is equally possible when the reinforcing structure is only above or below the membrane layer. Figure 9 b')- Figure 9 e') Again, the corresponding variation of the reinforcement structure 20 after removing the sacrificial layers 3 and 4 is shown.
[0050] Reference Figure 9 a) to Figure 9 The parameters shown in e) should be applicable to: s, u>= 0 s = u s>u s dV = arbitrary dVU <dO dM = arbitrary s´、u´>= 0 s´ = u´ s´>u´ s´ <u´ s´ = s s´>s s´ u´ = u u´>u u´ By considering the bending direction of the reinforcing structure 20 within the reinforced region 10 of the diaphragm 10, the stress curve in the diaphragm surface can be taken into account. This allows for the minimization of the influence of the reinforcing structure 20 on the diaphragm properties while correspondingly strengthening the region of the diaphragm reinforcement structure that is mechanically subjected to a stronger load. In the accompanying drawings, for simplicity, the reinforcing layer and the additional layer 5 are depicted as rectangles. However, in principle, the reinforcing layer and the additional layer can take any shape, such as lens-shaped, elliptical, goblet-shaped, champagne bowl-shaped, rectangular, or square with rounded corners and edges, as well as combinations of the aforementioned shapes.
[0051] The reinforcing structure 20 and the additional reinforcing layer 5 can be made of conductive, semi-conductive, or non-conductive materials, such as Si, Ge, SiO2, Si3N4, GeO2, Ge3N4, SiC, Al2O3, silicon-rich silicon nitride, and combinations thereof. Furthermore, these materials can be selectively doped, as is known in semiconductor technology, for example.
[0052] Figure 10 A possible process for manufacturing the proposed micromechanical structural element 100 is shown in a principle-based manner.
[0053] In step 200, a membrane 10 is provided.
[0054] In step 210, at least one reinforcing structure 20 is constructed in the diaphragm 10 in the region of at least one anchor structure 13 and / or in the region of at least one reinforcing structure 12, the reinforcing structure being constructed in a defined manner in terms of geometry, by means of the reinforcing structure reinforcing the diaphragm 10 in a defined manner.
[0055] Advantageously, this micromechanical structure element can be implemented in several different ways, such as as a capacitive pressure sensor, a microphone, a piezoresistive pressure sensor, etc.
Claims
1. A micromechanical structural element (100), the micromechanical structural element having: - Membrane (10); in, - The diaphragm (10) has at least one reinforcing structure (20) in the region of at least one anchor structure (13), the reinforcing structure being constructed in a defined manner in terms of geometry, by means of the reinforcing structure to reinforce the diaphragm (10) in a defined manner, wherein the reinforcing structure (20) is constructed to overlap in a defined manner over the at least one anchor structure (13). - wherein the reinforcing structure (20) includes at least one additional element (5) surrounded in the region of at least one anchor structure (13). - Wherein, the reinforcing structure (20) generates a diaphragm reinforcement in the region of the transition between the at least one anchor structure (13) and the diaphragm (10), thereby reducing stress variation inside the diaphragm (10).
2. The micromechanical structural element (100) according to claim 1, characterized in that, The additional element (5) is completely surrounded by polysilicon.
3. The micromechanical structural element (100) according to claim 1 or 2, characterized in that, The reinforcement structure (20) of each individual anchor structure (13) is not continuous.
4. The micromechanical structural element (100) according to claim 1 or 2, characterized in that, The lateral dimension of the protrusion of the reinforcing structure (20) relative to the remaining diaphragm (10) is related to the extent of the overlapping area and / or the thickness of the diaphragm (10).
5. The micromechanical structural element (100) according to claim 1 or 2, characterized in that, The reinforcing structure (20) has substantially the same or different lateral dimensions above and below the surface of the diaphragm (10).
6. The micromechanical structural element (100) according to claim 1 or 2, characterized in that, The reinforcing structure (20) is integrally constructed of a single material.
7. The micromechanical structural element (100) according to claim 1 or 2, characterized in that, The reinforcing structure (20) is constructed from at least one of the following materials: Si, Ge, SiO2, Si3N4, GeO2, Ge3N4, SiC, Al2O3, and silicon-rich silicon nitride.
8. A method for manufacturing a micromechanical structural element (100) according to any one of claims 1 to 7, the method comprising the following steps: - Provide a membrane (10); wherein, - At least one reinforcing structure (20) is constructed in the region of at least one anchor structure (13) in the diaphragm (10), the reinforcing structure being constructed in a defined manner in terms of geometry, by means of the reinforcing structure reinforcing the diaphragm (10) in a defined manner.