Pressure sensing element and manufacturing method thereof
By designing multiple accessories on the cavity of the pressure sensor device and forming a strain gauge element extending to the accessories on the membrane layer, the problems of piezoresistive element matching deterioration and membrane stress unevenness in the prior art are solved, and higher sensitivity and better measurement accuracy are achieved.
Patent Information
- Application Number
- CN202411234700.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-09-05
- Filing Date
- 2024-09-04
- Publication Date
- 2025-03-07
AI Technical Summary
When improving sensitivity, existing pressure sensor equipment faces problems such as deterioration of piezoresistive element matching and increasing membrane stress unevenness, resulting in a decrease in measurement accuracy.
A pressure sensing element is designed, wherein the cavity includes a main cavity and a plurality of accessories, a membrane layer covering the open periphery of the cavity and forming a strain gauge element on the membrane layer. The strain gauge element may partially or completely extend over the attachment of the cavity to improve sensitivity and matching.
Through this design, the sensitivity and sensitivity linearity of the pressure sensor equipment are improved, and the matching of the piezoresistive element is also improved nonlinearly, reducing measurement errors.
Smart Images
Figure CN119573930A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a pressure sensing element of the type including, for example, a membrane having a strain gauge element formed thereon, the membrane being disposed over a cavity formed in a substrate. The present invention also relates to a method of manufacturing a pressure sensing element of the type including, for example, forming a membrane over a cavity formed in a substrate, and forming a strain gauge element on the membrane. Background Art
[0002] In the field of pressure sensor elements, known structures include a substrate and a membrane layer, the substrate having an open cavity formed therein, such as a roughly rectangular cavity, and the membrane layer covers the substrate to close the cavity and form a membrane above the cavity. In such a structure, the cavity is sealed and set to a reference pressure (usually as close to a vacuum as possible), and is used when absolute pressure measurement is required. In contrast, in another pressure sensor structure, the cavity is open relative to the membrane layer so that relative pressure can be measured. One or more piezoresistive elements are usually arranged around the membrane near the edge of the membrane. When pressure is applied to the pressure sensor device, the membrane deflects, causing an uneven stress distribution on the membrane. Stress can be most effectively detected by placing the piezoresistive element around the membrane at a position where the stress on the membrane is the greatest. The location of these maximum stresses depends on the shape of the membrane used. Taking a substantially square membrane arranged above a substantially super-rectangular cavity as an example, the location of the highest stress coincides with a point located centrally along each side of the membrane near the edge of the membrane. However, the location of the maximum stress is a point on the membrane, and the piezoresistive element is larger and covers a limited area. Due to this larger area, the overall piezoresistive element cannot be sized just for the given much smaller location of the highest stress point, so any resulting average sensed stress level is reduced by the lower stress region surrounding the highest stress point.
[0003] For each maximum stress region on the membrane, the corresponding piezoresistive element can be formed as a single element or a pair of elements or an even number of elements. A single piezoresistive element along the edge of the membrane generally senses the stress on the membrane better than a single piezoresistive element across the edge of the membrane. Piezoresistive elements formed as a pair or an even number of piezoresistive elements provide improved sensitivity over a single piezoresistive element and excellent interconnection length matching, which is an important consideration when the piezoresistive elements are interconnected in a bridge arrangement for sensing purposes, such as the so-called Wheatstone bridge arrangement of piezoresistors arranged on at least two sides of the membrane. Such piezoresistive elements each include a pair (or more) of parallel piezoresistive material lines. In such an embodiment, and in the context of the square membrane mentioned above, the piezoresistive element is arranged at each of the four edges of the square membrane. However, all piezoresistive elements extend in the same direction, so the parallel piezoresistive material lines of the two longitudinal piezoresistive elements extend across the two edges of the membrane respectively, while the piezoresistive material lines of the remaining two transverse piezoresistive elements are parallel to the other two membrane edges respectively. With respect to lateral piezoresistive elements, despite the increased sensitivity, some sensitivity loss remains due to only a portion of the piezoresistive material, and therefore the overall piezoresistive area of the entire piezoresistive sensor element, residing on the edge of the membrane. In practice, this should be understood relative to the established practice of not optimally placing each of the piezoresistive elements, since the placement is chosen to optimize the integrated / average sensitivity across all piezoresistive elements. Thus, the first piezoresistive line (of a pair of piezoresistive material lines) that is closest to the edge of the membrane is more sensitive than the other piezoresistive line that is disposed further away from the edge. Similarly, longitudinal piezoresistive elements also suffer some sensitivity loss.
[0004] It is known to increase the sensitivity of a pressure sensor device by increasing the surface area of the membrane. However, this requires that the piezoresistive elements remain at the edges of the enlarged membrane, thereby increasing the distance between the piezoresistive elements. This increase results in a degradation of the matching of the piezoresistive elements due to the increased distance between the piezoresistive elements and the stress around the membrane being distributed with increasing non-uniformity as the membrane surface area increases. Additionally, as the membrane size increases, the piezoresistive elements move closer to the edge of the semiconductor die including the membrane and the cavity. This proximity to the edge of the die may cause delamination of the die and / or errors in the measurement in response to the drift of the piezoresistive elements over time and temperature. Summary of the invention
[0005] According to a first aspect of the present invention, there is provided a pressure sensing element for a pressure sensor device, the pressure sensing element comprising: a substrate portion including a cavity formed therein, the mouth of the cavity having an open periphery; a membrane layer covering the open periphery of the cavity; and a strain gauge element disposed on the membrane layer above the cavity; wherein the cavity comprises a main cavity and a first accessory formed integrally with the main cavity.
[0006] The strain gauge element disposed on the membrane layer above the cavity may extend at least partially above the first attachment.
[0007] The strain gauge element disposed on the membrane layer above the cavity may extend partially over the first attachment.
[0008] The cavity may include a peripheral sidewall; a first portion of the peripheral sidewall may follow a first primary path to define a first side of the main cavity, and a second portion of the peripheral sidewall may deviate from the first primary path about the first attachment and return to the first primary path.
[0009] The first appendage of the cavity may be substantially rectangular. The corner of the second portion of the peripheral sidewall may be curved relative to the first appendage. The corner of the second portion of the peripheral sidewall may be an inner corner. The corner of the second portion of the peripheral sidewall may be an outer corner. At least one corner of the main cavity may be curved.
[0010] The cavity may further include a second attachment formed integrally with the main cavity; and a third portion of the peripheral sidewall may follow a second main path to define a second side of the main cavity, and a fourth portion of the peripheral sidewall may deviate from the second main path about the second attachment and return to the second main path.
[0011] The first primary path may be substantially parallel to the second primary path.
[0012] The cavity may further include a third accessory formed integrally with the main cavity; a fifth portion of the peripheral side wall may follow a third main path to define a third side of the main cavity, and a sixth portion of the peripheral side wall may deviate from the third main path with respect to the third accessory and return to the third main path; and the third main path may be non-parallel to the first main path.
[0013] The third primary path may be substantially perpendicular to the first primary path.
[0014] The cavity may further include a fourth attachment formed integrally with the main cavity; a seventh portion of the peripheral side wall may follow a fourth main path to define a fourth side of the main cavity, and an eighth portion of the peripheral side wall may deviate from the fourth main path about the fourth attachment and return to the fourth main path.
[0015] The fourth primary path may be substantially perpendicular to the second primary path.
[0016] The cavity may include a peripheral sidewall; a first portion of the peripheral sidewall may follow a first primary path to define a first side of the main cavity; the cavity may further include a second attachment formed integrally with the main cavity; and the first attachment and the second attachment may extend away from the first primary path, respectively.
[0017] A second portion of the peripheral side wall may follow a second primary path to define a second side of the main cavity; a third portion of the peripheral side wall may follow a third primary path to define a third side of the main cavity; a fourth portion of the peripheral side wall may follow a fourth primary path to define a fourth side of the main cavity; the cavity may further include a third accessory and a fourth accessory respectively formed integrally with the main cavity; the third accessory may extend away from the second primary path, and the fourth accessory may extend away from the third primary path; and the first portion, the second portion, the third portion, and the fourth portion of the peripheral side wall may define a substantially rectangular periphery.
[0018] The first attachment may have a width dimension in a direction away from the first main path, and a length dimension parallel to the first main path; and the length-to-width dimension ratio may be less than 2.5:1.
[0019] The side of the first attachment may be configured to extend along a line substantially parallel to the first side of the main cavity for less than 50% of the length of the first side of the main cavity.
[0020] The first appendage may have a first length dimension parallel to the first primary path; and the first length dimension may be between 10% and 20% of the length of the first side of the main cavity.
[0021] The pressure sensing element may further include a bridge arrangement including strain gauge elements.
[0022] The strain gauge element may include a first portion of pressure sensitive material disposed substantially parallel to a second portion of pressure sensitive material.
[0023] The pressure sensitive material may be a piezoresistive material.
[0024] According to a second aspect of the present invention, there is provided a method for manufacturing a pressure sensing element for a pressure sensor device, the method comprising: etching a substrate portion to form a cavity therein, the mouth of the cavity having an open periphery; providing a membrane layer covering the open periphery of the cavity; and forming a strain gauge element on the membrane layer above the cavity; wherein forming the cavity comprises forming a main cavity and a first accessory formed integrally with the main cavity.
[0025] It is therefore feasible to provide a pressure sensor device and a method for manufacturing the same, which provides improved sensitivity of measurement and linearity of sensitivity, the sensitivity of the pressure sensor device decreasing less with increasing measured pressure than known membrane and cavity pressure sensor devices. The structure of the pressure sensor device avoids the need to significantly increase the surface area of the membrane with a corresponding increase in the spacing between the pressure sensor elements. Additionally, the pressure sensor device provides improved matching of nonlinearities between piezoresistive elements disposed longitudinally and transversely relative to respective edges of the membrane. Thus, when integrated into a bridge circuit configuration for measurement purposes, the resulting bridge has improved immunity to nonlinearities relative to the resistive elements of the bridge circuit configuration. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] At least one embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:
[0027] Figure 1 is a schematic diagram of a plan view of a partially formed, unpackaged pressure sensing element constituting a pressure sensor device of an embodiment of the present invention;
[0028] Figure 2 The manufacturing method of another embodiment of the present invention is Figure 1 A flow chart of a method of partially forming a pressure sensing element; and
[0029] Figures 3 to 9 yes Figure 1 Schematic diagram of different formation stages of a pressure sensing element. DETAILED DESCRIPTION
[0030] Throughout the following description, the same reference numerals will be used to identify the same parts.
[0031] refer to Figure 1 , a partially formed pressure sensing element 100 of a pressure sensor device includes a substrate 102 (not shown) having a cavity 104 therein and a membrane layer 106 disposed above the substrate 102. A first pad 108, a second pad 110, a third pad 112, and a fourth pad 114 are disposed on the membrane layer 106 and are located near a corner 116 of the cavity 104 in this example. The cavity 104 includes a generally rectangular main cavity 118 and a first appendage 120, a second appendage 122, a third appendage 124, and a fourth appendage 126 that are respectively formed integrally with the main cavity 118. In this example, the first appendage 120, the second appendage 122, the third appendage 124, and the fourth appendage 126 of the main cavity 118 extend away from the main cavity 118, respectively. The main cavity 118 is the largest cavity among the main cavity 118 and the first appendage 120, the second appendage 122, the third appendage 124, and the fourth appendage 126 of the main cavity 118.
[0032] In this regard, the cavity 104 includes a peripheral sidewall 128 that defines the sides of the cavity 104 (both the perimeter of the main cavity 118 and the perimeters of the first, second, third, and fourth appendages 120, 122, 124, and 126). In this example, the main cavity 118 includes a first side 130, a second side 132, a third side 134, and a fourth side 136. The first side 130, the second side 132, the third side 134, and the fourth side 136 together define the rectangular shape of the main cavity 118. Thus, the peripheral sidewall 128 includes a first portion 138 thereof that defines the first side 130 of the main cavity 118, and in this regard, the first portion 138 follows a first primary path to define a substantially straight side of the first side 130. The second portion 140 of the peripheral side wall 128 deviates from the first main path and then returns to the first main path after extending a first predetermined distance 141 parallel to the first main path so as to form the first appendage 120 having a lug-like appearance relative to the main cavity 118, for example, the first appendage 120 protrudes from the main cavity 118. The peripheral side wall 128 also includes a third portion 142 thereof defining the second side 132 of the main cavity 118, and in this regard, the third portion 142 follows the second main path to define another generally straight side of the second side 132. The fourth portion 144 of the peripheral side wall 128 deviates from the second main path and then returns to the second main path after extending a second predetermined distance 145 parallel to the second main path so as to form the second appendage 122 having a lug-like appearance relative to the main cavity 118. The peripheral side wall 128 further includes a fifth portion 146 thereof defining the third side 134 of the main cavity 118, and in this regard, the fifth portion 146 follows the third main path to define another generally straight side of the third side 134. The sixth portion 148 of the peripheral side wall 128 deviates from the third main path and then returns to the third main path after extending a third predetermined distance 149 parallel to the third main path to form a third appendage 124 having a lug-like appearance relative to the main cavity 118. The peripheral side wall 128 also includes a seventh portion 150 thereof defining a fourth side 136 of the main cavity 118, and in this regard, the seventh portion 150 follows the fourth main path to define another generally straight side of the fourth side 136. The eighth portion 152 of the peripheral side wall 128 deviates from the fourth main path and then returns to the fourth main path after extending a fourth predetermined distance 153 parallel to the fourth main path to form a fourth appendage 126 having a lug-like appearance relative to the main cavity 118.
[0033] The film layer 106 covers the cavity 104 , the cavity 104 includes the first attachment 120 , the second attachment 122 , the third attachment 124 and the fourth attachment 126 , and the area where the film layer 106 covers the cavity 104 forms a film above the cavity 104 .
[0034] Although in this example, the cavity 104 includes accessories on each side 130, 132, 134, 136 of the main cavity 118, in other examples, a greater or lesser number of accessories may be provided, for example, no accessories may be provided on one side of the cavity 104, which in this example means that the cavity 104 includes three accessories. In other examples, more than one accessory of the main cavity 118 may be provided at one or more sides of the main cavity 118. For example, instead of the second accessory 122 of the main cavity 118 being provided at the second side 132 of the main cavity 118, the second accessory 122 of the main cavity 118 may be provided at the first side 130 of the main cavity 118, such that the first accessory 120 and the second accessory 122 extend away from the first main path.
[0035] In this example, the first side 130 is substantially parallel to the second side 132 and substantially perpendicular to the third side 134. The fourth side 136 is substantially perpendicular to the first side 130 and the second side 132 and substantially parallel to the third side 134.
[0036] The first attachment 120, the second attachment 122, the third attachment 124, and the fourth attachment 126 are generally rectangular, and therefore, in this example, the first attachment 120, the second attachment 122, the third attachment 124, and the fourth attachment 126 each have a first outer corner 158 and a second outer corner 160, and a first inner corner 162 and a second inner corner 164. One or more of the first outer corner 158 and the second outer corner 160 and the first inner corner 162 and the second inner corner 164 may be rounded to improve reliability in terms of performance (e.g., to minimize measurement drift), and durability during the service life of the pressure sensor device.
[0037] Each of the first accessory 120, the second accessory 122, the third accessory 124, and the fourth accessory 126 has a respective width dimension 154 extending in a direction away from the first primary path, the second primary path, the third primary path, and the fourth primary path, respectively. The first accessory 120, the second accessory 122, the third accessory 124, and the fourth accessory 126 also each have a respective length dimension 156 extending in a direction parallel to the first primary path, the second primary path, the third primary path, and the fourth primary path, respectively. In this example, the aspect ratio of each of the first accessory 120, the second accessory 122, the third accessory 124, and the fourth accessory 126 is less than 2.5 to 1. It should also be understood that the exact aspect ratio of each of the first accessory 120, the second accessory 122, the third accessory 124, and the fourth accessory 126 may vary between the accessories 120, 122, 124, 126, but generally remain within the constraint of less than 2.5 to 1.
[0038] As described above, each of the second portion 140, the fourth portion 144, the sixth portion 148, and the eighth portion 152 of the peripheral sidewall 128 extends parallel to the first main path for a first predetermined distance 141, parallel to the second main path for a second predetermined distance 145, parallel to the third main path for a third predetermined distance 149, and parallel to the fourth main path for a fourth predetermined distance 153, respectively. The first predetermined distance 141, the second predetermined distance 145, the third predetermined distance 149, and the fourth predetermined distance 153 are respectively less than 50% of the length of the first side 130, the second side 132, the third side 134, and the fourth side 136 of the main cavity 118. In this example, the lengths of the first predetermined distance (length) 141, the second predetermined distance (length) 145, the third predetermined distance (length) 149, and the fourth predetermined distance (length) 153 are respectively between about 10% and 20% of the length of the first side 130, the second side 132, the third side 134, and the fourth side 136.
[0039] The first strain gauge element 166 is disposed on an area of the membrane layer 106 that functions as a membrane near the first attachment 120, and the second strain gauge element 168 is disposed on an area of the membrane layer 106 that functions as a membrane near the second attachment 122. The third strain gauge element 170 is disposed on an area of the membrane layer 106 that functions as a membrane near the third attachment 124, and the fourth strain gauge element 172 is disposed on an area of the membrane layer 106 that functions as a membrane near the fourth attachment 126. In this example, the first strain gauge element 166, the second strain gauge element 168, the third strain gauge element 170, and the fourth strain gauge element 172 are thus disposed on the membrane layer 106 above the cavity 104, and extend partially above the first attachment 120, the second attachment 122, the third attachment 124, and the fourth attachment 126, respectively. However, in other examples, one or more of the strain gauge elements may simply be close to the respective interfaces between the main cavity 118 and the first attachment 120, the second attachment 122, the third attachment 124, and the fourth attachment 126.
[0040] In this example, each of the first strain gauge element 166, the second strain gauge element 168, the third strain gauge element 170, and the fourth strain gauge element 172 is formed of a piezoresistive material and includes doped polysilicon. In this example, each strain gauge element includes a first portion 174 of polysilicon and a second portion 176 of polysilicon, which are arranged in parallel and doped with the same dopant and constitute a first portion of the piezoresistance material substantially parallel to the second portion of the piezoresistance material. The first portion 174 of polysilicon and the second portion 176 of polysilicon are connected at their first ends by an interconnect portion 178 of polysilicon, which is doped with a dopant different from the dopant used to form the first portion 174 of polysilicon and the second portion 176 of polysilicon. Opposite ends of the first portion 174 of polysilicon and the second portion 176 of polysilicon, which form each strain gauge, are connected to a first pad connection 180 and a second pad connection 182.
[0041] In this example, first pad connection 180 of second strain gauge element 168 is coupled to first pad 108, and second pad connection 182 of second strain gauge element 168 is coupled to fourth pad 114. First pad connection 180 of third strain gauge element 170 is coupled to fourth pad 114, and second pad connection 182 of third strain gauge element 170 is coupled to third pad 112. First pad connection 180 of first strain gauge element 166 is coupled to third pad 112, and second pad connection 182 of first strain gauge element 166 is coupled to second pad 110. First pad connection 180 of fourth strain gauge element 172 is coupled to second pad 110, and second pad connection 182 of fourth strain gauge element 172 is coupled to first pad 108.
[0042] First strain gauge element 166, second strain gauge element 168, third strain gauge element 170, and fourth strain gauge element 172 are interconnected in a bridge configuration or arrangement (e.g., a Wheatstone bridge configuration) via first pad 108, second pad 110, third pad 112, and fourth pad 114. However, it should be understood that in other examples, different circuit configurations may be employed, such as a half-bridge configuration or any other suitable interconnection arrangement for measurement.
[0043] as follows( Figures 2 to 9 ) forms the pressure sensing element 100 as described above.
[0044] First, a substrate 102 is formed (step 200) using any suitable substrate manufacturing technique and provided ( Figure 3 ) substrate 102 for forming pressure sensing element 100. Then, cavity 104 ( Figure 4 and Figure 5 ), and the cavity 104 includes a main cavity 118 and a first attachment 120, a second attachment 122, a third attachment 124, and a fourth attachment 126. The cavity 104 has an open mouth 184, and the open mouth 184 has an open periphery 186. Then, a film constituting a diaphragm is formed (step 204) using any suitable technique for forming a film layer, and then the film is applied (step 206) above the substrate 102 ( Figure 6 ) to cover the open periphery 186 of the cavity 104, thereby closing the cavity 104, but the cavity 104 still has an open periphery 186.
[0045] The first strain gauge 166, the second strain gauge 168, the third strain gauge 170 and the fourth strain gauge 172 are formed (step 208) Figure 7 Then, the first pad connection 180, the second pad connection 182 and the interconnection portion 178 ( Figure 8 ) are arranged (step 210) on the film layer 106 to prepare for the interconnection of the first strain gauge element 166, the second strain gauge element 168, the third strain gauge element 170 and the fourth strain gauge element 172. Then, the first pad 108, the second pad 110, the third pad 112 and the fourth pad 114 are formed (step 212) on the film layer 106. Fig. 9 ) to complete the interconnection of the first strain gauge element 166, the second strain gauge element 168, the third strain gauge element 170 and the fourth strain gauge element 172, and to complete and provide an electrical connection access point to the above-mentioned bridge configuration.
Claims
1. A pressure sensing element for a pressure sensor device, the pressure sensing element comprising: a substrate portion, the substrate portion including a cavity formed therein, the mouth of the cavity having an open periphery; a film layer, the film layer covering the outer periphery of the opening of the cavity; as well as a strain gauge element, wherein the strain gauge element is disposed on the membrane layer above the cavity; The cavity comprises a main cavity and a first attachment formed integrally with the main cavity.
2. The pressure sensing element according to claim 1, characterized in that: The strain gauge element disposed on the membrane layer above the cavity extends at least partially over the first attachment.
3. The pressure sensing element according to claim 1 or claim 2, characterized in that: The cavity includes a peripheral sidewall, a first portion of the peripheral sidewall follows a first primary path to define a first side of the main cavity, and a second portion of the peripheral sidewall deviates from the first primary path about the first attachment and returns to the first primary path.
4. The pressure sensing element according to claim 3, characterized in that: The cavity further includes a second attachment formed integrally with the main cavity; and A third portion of the peripheral sidewall follows a second primary path to define a second side of the main cavity, and a fourth portion of the peripheral sidewall deviates from the second primary path about the second attachment and returns to the second primary path.
5. The pressure sensing element according to claim 4, characterized in that: The first primary path is substantially parallel to the second primary path.
6. The pressure sensing element according to claim 4, characterized in that: The cavity further includes a third attachment formed integrally with the main cavity; a fifth portion of the peripheral sidewall follows a third primary path to define a third side of the main cavity, and a sixth portion of the peripheral sidewall deviates from the third primary path about the third attachment and returns to the third primary path; and The third main path is non-parallel to the first main path.
7. The pressure sensing element according to claim 6, characterized in that: The cavity further includes a fourth attachment formed integrally with the main cavity; A seventh portion of the peripheral sidewall follows a fourth primary path to define a fourth side of the main cavity, and an eighth portion of the peripheral sidewall deviates from the fourth primary path about the fourth attachment and returns to the fourth primary path.
8. The pressure sensing element according to claim 1 or claim 2, characterized in that: The cavity includes a peripheral sidewall, a first portion of the peripheral sidewall follows a first primary path to define a first side of the main cavity; The cavity further includes a second attachment formed integrally with the main cavity; and The first attachment and the second attachment each extend away from the first main path.
9. The pressure sensing element according to claim 8, characterized in that: a second portion of the peripheral sidewall follows a second primary path to define a second side of the main cavity; a third portion of the peripheral sidewall follows a third primary path to define a third side of the main cavity; a fourth portion of the peripheral sidewall follows a fourth primary path to define a fourth side of the main cavity; The cavity further includes a third attachment and a fourth attachment respectively formed integrally with the main cavity, the third attachment extending away from the second main path, and the fourth attachment extending away from the third main path; and The first portion, the second portion, the third portion, and the fourth portion of the peripheral sidewall define a substantially rectangular perimeter.
10. The pressure sensing element according to claim 1, characterized in that: The first attachment has a width dimension in a direction away from the first primary path, and a length dimension parallel to the first primary path; and The aspect ratio is less than 2.5:
1.
11. The pressure sensing element according to claim 2, characterized in that: A side of the first attachment is configured to extend along a line substantially parallel to the first side of the main cavity for less than 50% of a length of the first side of the main cavity.
12. The pressure sensing element according to claim 11, characterized in that: The first attachment has a first length dimension parallel to the first primary path; and The first length dimension is between 10% and 20% of the length of the first side of the main cavity.
13. The pressure sensing element according to claim 1, further comprising: A bridge arrangement includes the strain gauge element.
14. The pressure sensing element according to claim 1, characterized in that: The strain gauge element includes a first portion of pressure sensitive material disposed substantially parallel to a second portion of the pressure sensitive material.
15. A method of manufacturing a pressure sensing element for a pressure sensor device, the method comprising: etching a substrate portion to form a cavity in the substrate portion, the mouth of the cavity having an open periphery; Disposing a film layer covering the outer periphery of the opening of the cavity; as well as forming a strain gauge element on the membrane layer above the cavity; in Forming the cavity includes forming a main cavity and a first attachment formed integrally with the main cavity.