Silicon microdevices with planar strain sensing members

Abstract

A micromechanical device 1 comprises a semiconductor device layer 5 with a flexible section 2, a support structure 30 formed in a support layer 3, an intermediate oxide layer 4, and a detector 13 for

Description

The present invention is related to silicon micromechanical devices comprising thin flat flexible section, also called freestanding portions, such as micromembranes and / or microbeams, also called hereinafter cantilevers, the off-plane bending of which flexible section is detected with built-in strain sensing members, providing simultaneously both: increased sensitivity to said bending and a high degree of self-compensation of background noise. The envisaged micromechanical devices are applicable for measuring and monitoring directly or by exploiting relevant transducers a plurality of parameters, like: force, displacement, vibrations, acceleration, pressure, flow, or the like, parameters or their perturbations, for various applications, including analytical studies and measurements and / or processing of ultra-small structures, in order to study specific properties or processing with sub-atomic resolution, accuracy and increased dynamic range. The micromechanical devices, as part of a variety of specialized apparatus, will find application in various areas for research, manufacturing and control of modern products, where the development of relevant processes will be accelerated with significant impact on multiple domains, ensuring reduction in material and energy costs. Current development of technical areas and modern technologies is unthinkable without availability of relevant means and methods for measurement, monitoring and control. One such class of modern technical means, methods and relevant techniques specifically related to the use of devices comprising thin flat flexible elements are pressure sensors. Usually, a pressure sensor comprises a thick and rigid peripheral part having shape of a frame and a thin flat micromembrane having thickness du, in the range from about 1.0pm to about 20.0pm, the shape of which is substantially square, being able to bend in orthogonal direction to its top surface in response to the pressure difference on its two sides. As it is known by those who skilled in the art, on top surface of the said micromembrane at its periphery, two pairs of equivalent thin strain sensing members are embedded, that are co-planar with said surface. When the micromembrane is bended, strain sensing members change the value of their resistance, and being connected electrically in a full bridge configuration, a voltage signal is generated (Sensors and Actuators A 281 (2018) 156-175). Based on this principle, piezoresistive sensors that measure the strain in a deformable shaped piece of semiconductor that responds directly or by a transducer, to stimuli or to their perturbations, like: force of any nature, displacement, torque, vibrations / oscillations, accelerations, weight, pressure flow, etc., diverse sensors have been developed and some of them were massively exploited during the last decades. Specifically, past development of pressure sensors using thin silicon micromembranes with embedded planar strain sensing members having depth xj, being typically from about 0.5 pm to about 2.0pm, has enabled scaling-down in their size from centimeter to millimeter ranges. Despite the need for the thickness of the micromembrane d«to be at least three times larger the depth of the resistor, i.e., du >3. Xj (1), sensors’ usability facilitated and stimulated great expansion of the areas of their applicability, which has ensured a reduction in their cost and price. Devices of this type are increasingly widely applicable in many areas of life and technology, incl. in medicine, ensuring the quality of life, industry, transportation and all other domains of human activities. Therefore, the miniaturization of pressure sensors for different applications ranges is a major factor empowering their further development. At the same time, when reducing the size of a flexible micromembrane at constant thickness du, its stiffness increases, which decreases the sensor sensitivity, especially for the range for small pressures, e.g. <0.5Bar or similar. Furthermore, the square shape of the micromembrane prevents creation of sensors with small cross-sectional dimensions, e.g. <1 mm, which limits their application in a number of areas, e.g. in personalized invasive medicine, etc. important areas. Therefore, scaling down the size of devices inevitably faced limits that can be overcome only with radical changes of the design and technologies for their fabrication. A specific case of pressure sensors are microphones, also called MEMS microphones, which are exploited in all modern monitoring and communication systems, incl. in smart portable devices. Another class of technical means, specific methods and techniques related to applications of devices with thin flat flexible elements, are self-sensing microbeam, often called cantilever, sensors for atomic force microscopy (AFM). These sensors allow for measurements, analyses and processing to be performed with a resolution comparable to or better than the size of atoms. The devices consist of a thick and rigid body with a rectangular shape and a thin flat microcantilever having thickness de in the range from about 0.5pm to above 20pm, preferably from 0.7pm to 10pm, length L in the range from about 10pm to above 600pm, and width W in the range from about 2 pm to about 250pm, protruding of the body, being able to bend in orthogonal to the top surface direction. Single or plurality of thin sensitive strain sensing members having substantially uniform thickness xj are so single-side embedded, that are co-planar with the top surface of the said flexible beam, being located in the area close of its fixed end. If used, two or three planar fixed resistors having equivalent resistance are also located on the top surface of the non-bendable body, and all four elements are electrically connected in a full bridge configuration, so that generate a signal Vout, which corresponds to the interaction of a probe element with a sample. To ensure high sensitivity of the sensor, thickness de of the microcantilever that is at least three times larger than the depth Xj of strain sensing members (cfc^ 3. xj), is required. This constrains the exploitation of the devices with self-sensing cantilevers for measurement and analyses of soft, e.g. biological, samples which are among the most important applications of modern AFM. The usually exploited configuration in a full voltage bridge of said sensitive strain sensing members and constant-value resistors, is balanced in non-bended position. A common feature the above-described technical means - pressure sensor and microcantilever sensor for AFM, is that planar strain sensing members are single-side built-in on top surface and respond to the deflection in orthogonal direction to the said surface of the flat flexible element, generating an electrical signal, without any additional components needed. This simplifies the operation of the respective devices and apparatus, providing additional advantages and functionalities that were unattainable with their alternatives. However, due to the increasingly widening and varied application of off-plane bendable silicon piezoresistive microdevices, as well as the unexpected opportunities that they can provide being temperature independent, these devices can replace multiple types of currently mass exploited sensors exploiting alternative principles of operation. This requires further new sensors to be created with controlled stiffness of their flexures, minimal lateral size, low noise, and extended dynamic range, that are applicable for detection of a single or plurality of pre-selected stimuli or their perturbations. By being used in common appliances and devices, these sensors will improve their performance and expand their capabilities. In a first aspect, the present disclosure is directed at a micromechanical device comprising a device layer with a flexible section, a support layer, an optional intermediate oxide layer, a support structure formed in the support layer, and a detector for detecting deflection of the flexible section, wherein a first surface of the device layer and a second surface of the device layer are orientated parallel to each other and located on opposite sides of the device layer, wherein the device layer of semiconductor material is attached to the support layer at the second surface and wherein the device layer comprises a freestanding portion that extends from the support structure. The flexible section comprises the freestanding portion and is configured to deflect in the direction that is orthogonal to the first and second surfaces of the device layer. The detector comprises a first strain sensing member, a second strain sensing member, a third strain sensing member, and a fourth sensing member, an electrical conductor connected to the first strain sensing member and the second strain sensing member, and an electrical conductor connected to the third strain sensing member and the fourth strain sensing member, wherein the first strain sensing member and third sensing member are located at the first surface within the flexible section and the second strain sensing member and fourth strain sensing member are located at the second surface within the flexible section. According to an embodiment, the first strain sensing member and third strain sensing member are a piezoresistor or a channel of a field effect transistor, made of inverse doped semiconductor material, such as: silicon, diamond, gallium arsenide, gallium nitride or made of a single-layer material, such as graphene, boron nitride; molybdenum nitride, and the second strain sensing member and fourth sensing member are a piezoresistor made of said inverse doped semiconductor material. According to an embodiment, the first semiconductor strain sensing member is located above the second strain sensing member, and third strain sensing member is located above the fourth strain sensing member, wherein, for example, an outer contour of the first strain sensing member overlaps with an outer contour of the second strain sensing member and an outer contour of the third strain sensing member overlaps with an outer contour of the fourth strain sensing member. According to an embodiment, a resistance of the first strain sensing member and a resistance of the second strain sensing member differ by at most 0.5%, such at most 0.25%, at most 0.1%, at most 0.075% or at most 0.05%, and wherein a resistance of the third strain sensing member and a resistance of the fourth strain sensing member differ by at most 0.5%, such at most 0.25%, at most 0.1%, at most 0.075% or at most 0.05%. According to an embodiment, the first strain sensing member and the second strain sensing member are electrically conductively connected in series, and the third strain sensing member and the fourth strain sensing member are electrically conductively connected in series. According to an embodiment, the first strain sensing member and the third strain sensing member are located within a recess of the first surface and / or the second strain sensing member and the fourth strain sensing member are located within a recess of the second surface. According to an embodiment, a depth of the recess is at least 0.25pm, such as at least 0.5pm, at least 0.7pm or at least 1 pm and / or at most 7pm, such as at most 5pm or at most 3pm, wherein, for example, the depth of the recess is between 0.5pm and 5pm, such as between 0.7pm and 3.0pm. According to an embodiment, the electrical circuit comprises an electrically conducting via that connects the first semiconductor strain sensing member with the second strain sensing memberthrough the freestanding portion of the device layer, wherein, for example, the electrically conducting via is located within the flexible section. According to an embodiment, the electrically conducting via comprises a depression within one of the first surface and the second surface, and the via comprises an electrically conducting region, for example formed by an inverse doped region of the device layer, extending from the one of the first surface and the second surface into the device layer, wherein the electrically conducting region or overlaps with the depression. According to an embodiment, the material separating the first semiconductor strain sensing member and the second semiconductor strain sensing member is one of: a semiconductor, such as a doped semiconductor; diamond, gallium arsenide, gallium nitride. According to an embodiment, a further insulating layer is located at the first surface. According to an embodiment, a thickness of the device layer and / or a thickness of the freestanding portion is between 0.25pm and 40pm, such as between 0.5pm and 20pm or 0.7pm to 10pm, According to an embodiment, a length of the freestanding portion is at least 2.5pm, 5pm, 10pm, 20pm, 25pm or 50pm and / or at most 300pm, 500pm, 600pm, or 1mm, wherein, for example, the length of the freestanding portion is between 10 pm and 600pm, such as between 50pm and 450pm. According to an embodiment, a width of the freestanding portion is at least 1pm, 2pm, or 5pm and / or at most 100pm, 250pm or 500pm, wherein, for example, a width of the freestanding portion is between 2pm and 250pm, such as between 10pm and 120pm. According to an embodiment, the freestanding portion forms a cantilever that has a free end and a clamped end located opposite the free end, wherein the freestanding portion is only connected to the support structure and / or to the support layer at the clamped end. According to an embodiment, the freestanding portion has at least a first clamped end and a second clamped end located opposite the first clamped end and the freestanding portion is connected to the support structure and / or to the support layer at both the first clamped end and the second clamped end, wherein, for example, the freestanding portion forms a membrane that has a connection to the support structure and / or to the support layer that fully surrounds the freestanding portion. In a second aspect, the present disclosure is directed at a micromechanical device comprising a device layer with a flexible section, a support layer, a support structure formed in the support layer, and a detector for detecting deflection of the flexible section, wherein a first surface of the device layer and a second surface of the device layer are orientated parallel to each other and located on opposite sides of the device layer. The first surface and the second surface extend parallel to a first transverse direction and a second transverse direction, the second transverse direction being perpendicular to the first transverse direction. The device layer is attached to the support layer at the second surface and comprises a freestanding portion that extends from the support structure in the first transverse direction and does not overlap with the support structure in a height direction perpendicular to the first transverse direction and the second transverse direction. The freestanding portion comprises the flexible section and the flexible section is configured to deflect in the height direction. The detector comprises a first strain sensing member, a second strain sensing member, and an electrical circuit connected to the first strain sensing member and the second strain sensing member, wherein the first strain sensing member is located at the first surface within the flexible section and the second strain sensing member is located at the second surface within the flexible section. According to an embodiment, device layer comprises, such as consists of, a semiconductor material. According to an embodiment, each of the first strain sensing member and the second strain sensing member is selected from: a piezoresistor and a channel of a field effect transistor, wherein the piezoresistor or the channel of the field effect transistor comprise, such as are made of, an inverse doped semiconductor material, such as silicon, diamond, gallium arsenide, or gallium nitride, or comprise, such are made of, a single-layer material, such as graphene, boron nitride, or molybdenum nitride. According to an embodiment, the first strain sensing member is selected from the piezoresistor and the channel of the field effect transistor, wherein the second strain sensing member is selected as the piezoresistor. For example, the first strain sensing member may be selected as the channel of the field effect transistor and the second strain sensing member may be selected as the piezoresistor According to an embodiment, the first strain sensing member is located above the second strain sensing member in the height direction, wherein, for example, an outer contour of the first strain sensing member overlaps with an outer contour of the second strain sensing member in the height direction. The outer contours may delimit the respective first and second strain sensing member in the first transverse direction and / or the second transverse direction. According to an embodiment, the first strain sensing member and the second strain sensing member cover the same area in the first transverse direction and in the second transverse direction. According to an embodiment, the first strain sensing member and / or the second strain sensing member are elongated along the first transverse direction, the first strain sensing member and / or the second strain sensing member may have an extent in the first transverse direction that is larger than an extent in the second transverse direction. According to an embodiment, a resistance of the first strain sensing member and a resistance of the second strain sensing member differ by at most 5%, such at most 2.5%, at most 1%, at most 0.75%, at most 0.5%, at most 0.25%, at most 0.1%, at most 0.075% or at most 0.05%. According to an embodiment, the first strain sensing member and the second strain sensing member are electrically conductively connected in series. According to an embodiment, the first strain sensing member extends in a length direction and the second strain sensing member extends parallel to the first strain sensing member in the length direction. Thereby, the first strain sensing member and the second strain sensing member are electrically conductively connected to each other at the same end in the length direction. According to an embodiment, the length direction is the first transverse direction. According to an embodiment, a sensing conductor of the electrical circuit is electrically conductively connected to the first strain sensing member and to the second strain sensing member in between the first strain sensing member and the second strain sensing member. According to an embodiment, the micromechanical device further comprises a third strain sensing member and a fourth strain sensing member, wherein the third strain sensing member is located at the first surface and the fourth strain sensing member is located at the second surface. According to an embodiment, the third strain sensing member and / or the fourth strain sensing member are located within the flexible section. According to an embodiment, each of the third strain sensing member and the fourth strain sensing member is selected from: a piezoresistor and a channel of a field effect transistor, wherein the piezoresistor or the channel of the field effect transistor comprise, such as are made of, an inverse doped semiconductor material, such as silicon, diamond, gallium arsenide, or gallium nitride, or comprise, such as are made of a single-layer material, such as graphene, boron nitride, or molybdenum nitride. According to an embodiment, the third strain sensing member is selected from the piezoresistor and the channel of a field effect transistor and the fourth strain sensing member is selected as the piezoresistor. For example, the third strain sensing member may be selected as the channel of a field effect transistor and the fourth strain sensing member may be selected as the piezoresistor According to an embodiment, the third strain sensing member is located above the fourth strain sensing member in the height direction, wherein, for example, an outer contour of the third strain sensing member overlaps with an outer contour of the fourth strain sensing member. The outer contours may delimit the respective third and fourth strain sensing member in the first transverse direction and / or the second transverse direction. According to an embodiment, a resistance of the third strain sensing member and a resistance of the fourth strain sensing member differ by at most 5%, such at most 2.5%, at most 1%, at most 0.75%, at most 0.5%, at most 0.25%, at most 0.1%, at most 0.075% or at most 0.05%. According to an embodiment, the third strain sensing member and the fourth strain sensing member are electrically conductively connected in series. According to an embodiment, the first strain sensing member and the second strain sensing member are connected in series and form a voltage divider in between a first conductor and a second conductor, wherein, for example, the first conductor is a supply voltage conductor and the second conductor is a ground conductor. According to an embodiment, the detector comprises a first circuit element and a second circuit element, wherein the first circuit element and the second circuit element are connected in series and form a further voltage divider in between the first conductor and the second conductor and the further voltage divider is electrically conductively connected in parallel to the voltage divider. According to an embodiment, a further sensing conductor of the electrical circuit is electrically conductively connected to the first circuit element and to the second circuit element in between the first circuit element and the second circuit element. According to an embodiment, the first circuit element is configured as the third strain sensing member and / or the second circuit element is configured as the fourth strain sensing member. According to an embodiment, the first circuit element and / or the second circuit element are located within the flexible section. According to an embodiment, the first strain sensing member is electrically conductively connected in between the first conductor and the second strain sensing member, wherein the first circuit element is electrically conductively connected in between the second conductor and the second circuit element. According to an embodiment, the first circuit element is located at the first surface and the second circuit element is located at the second surface. According to an embodiment, the first circuit element is located above the second circuit element in the height direction, wherein, for example, an outer contour of the first circuit element overlaps with an outer contour of the second circuit element in the height direction. According to an embodiment, the first circuit element and the second circuit element cover the same area in the first transverse direction and the second transverse direction. According to an embodiment, a resistance of the first circuit element and a resistance of the second circuit element differ by at most 5%, such at most 2.5%, at most 1%, at most 0.75%, at most 0.5%, at most 0.25%, at most 0.1%, at most 0.075% or at most 0.05%. According to an embodiment, the resistances of the first strain sensing member, the second strain sensing member, the first circuit element and the second circuit element differ by at most 5%, such at most 2.5%, at most 1%, at most 0.75%, at most 0.5%, at most 0.25%, at most 0.1%, at most 0.075% or at most 0.05%. According to an embodiment, the first strain sensing member is located within a recess of the first surface and / or the second strain sensing member is located within a recess of the second surface. According to an embodiment, a depth of the recess in the height direction is at least 0.25pm, such as at least 0.5pm, at least 0.7pm or at least 1 pm and / or at most 7pm, such as at most 5pm or at most 3pm, wherein, for example, the depth of the recess in the height direction is between 0.5pm and 5pm, such as between 0.7pm and 3.0pm. According to an embodiment, the detector comprises an electrically conducting via that connects the first strain sensing member with the second strain sensing memberthrough the freestanding portion of the device layer in the height direction, wherein, for example, the electrically conducting via is located within the flexible section. According to an embodiment, the electrically conducting via comprises a depression within one of the first surface and the second surface, and the via comprises an electrically conducting region, for example formed by an inverse doped region of the device layer, extending from the one of the first surface and the second surface into the device layer parallel to the height direction. Thereby, the electrically conducting region overlaps with the depression in the height direction. According to an embodiment, the via comprises a further electrically conducting region, for example formed by a doped region of the device layer, extending from the other one of the first surface and the second surface into the device layer parallel to the height direction, wherein the electrically conducting region and the further electrically conducting region are separated from each other by a distance in the height direction in a region offset from the via and wherein the depth of the depression in the height direction is larger than the distance so that the electrically conducting region joins the further electrically conducting region at the via. According to an embodiment, a distance A between the first strain sensing member and the second strain sensing member is between 0.5pm and 20 pm, for example between 0.7pm and 10 pm. According to an embodiment, the strain sensing member comprises a doped area of the device layer. For example, the strain sensing member may be formed as the doped area. According to an embodiment, the material separating the first strain sensing member and the second strain sensing member is one of: a semiconductor, such as a doped semiconductor; gallium nitride; boron nitride; molybdenum nitride; and a single-layer material, such as graphene, wherein, for example, the semiconductor is silicon, gallium arsenide, gallium nitride. According to an embodiment, the second surface of the device layer has a planar connection to the support layer. According to an embodiment, the device layer is bonded to the support layer at the second surface. According to an embodiment, the device layer is made from a semiconductor one of: a semiconductor, such as an inverse doped semiconductor; gallium nitride; boron nitride; molybdenum nitride; and a single-layer material, such as graphene, wherein, for example, the semiconductor is silicon, gallium arsenide, gallium nitride. According to an embodiment, the support layer is made from one of: a semiconductor, such as a doped semiconductor; gallium nitride; boron nitride; molybdenum nitride; and a single-layer material, such as graphene, wherein, for example, the semiconductor is silicon, gallium arsenide, gallium nitride. According to an embodiment, an intermediate oxide layer is located in between the device layer and the support layer at the second surface. According to an embodiment, at least part of the freestanding portion, such as at least the flexible section or the entire freestanding portion, is free from the intermediate oxide layer. According to an embodiment, an insulating layer is located at the first surface. According to an embodiment, a length of the freestanding portion in the first transverse direction and a width of the freestanding portion in the second transverse direction are larger than a height of the freestanding portion in the height direction. According to an embodiment, a length of the freestanding portion in the first transverse direction is larger than a width of the freestanding portion in the second transverse direction. According to an embodiment, a thickness of the device layer and / or a thickness of the freestanding portion in the height direction is between 0.25pm and 40pm, such as between 0.5pm and 20pm or 0.7pm to 10pm, wherein, for example, the thickness of the device layer and / or the thickness of the freestanding portion in the height direction is between 2pm and 250pm, such as between 10pm and 120pm. According to an embodiment, a length of the freestanding portion in the first transverse direction is at least 2.5pm, 5pm, 10pm, 20pm, 25pm or 50pm and / or at most 300pm, 500pm, 600pm, or 1 mm, wherein, for example, the length of the freestanding portion in the first transverse direction is between 10 pm and 600pm, such as between 50pm and 450pm. According to an embodiment, a width of the freestanding portion in the second transverse direction is at least 1pm, 2 pm, or 5pm and / or at most 100pm, 250pm or 500pm, wherein, for example, a width of the freestanding portion in the second transverse direction is between 2pm and 250pm, such as between 10pm and 120pm. According to an embodiment, the freestanding portion forms a cantilever that has a free end and a clamped end located opposite the free end, wherein the freestanding portion is only connected to the support structure and / or to the support layer at the clamped end. According to an embodiment, the flexible section has at least a first clamped end and a second clamped end located opposite the first clamped end, and the flexible section is connected to the support structure and / or to the support layer at both the first clamped end and the second clamped end. For example, the flexible section may form a micromembrane that has a connection to the support structure and / or to the support layer that fully surrounds the freestanding portion. With all aspects and embodiments of the present disclosure, the support layer and the device layer may be made from different materials. Alternatively, they may be made from the same material. The support layer may be made from a single material and / or the device layer may be made from a single material. The material of the support layer and / or the material of the device layer may be structured, such as etched and / or doped, to form individual elements of the micromechanical device. The device layer and / or the support layer may be configured as flat layers that extend in the first transverse direction and in the second transverse direction and that each have a height in the height direction that is smaller than an extent in the first transverse direction and an extent in the second transverse direction. For example, the extent in the first transverse direction and / or the extent in the second transverse direction may be at least 3 times, such as at least 5 times, at least 10 times, or at least 100 times the height. The micromechanical device may comprise at least one intermediate layer, such as an oxide layer, in between the support layer and the device layer. The intermediate layer may be formed from a material that is different from the material of the device layer and / or from the material of the support layer. The device layer may be connected to the support layer via the intermediate layers. The intermediate layer may separate the device layer and the support layer in the height direction. The intermediate layers may be configured as flat layers that extend in the first transverse direction and in the second transverse direction and that each have a height in the height direction that is smaller than an extent in the first transverse direction and an extent in the second transverse direction. For example, the extent in the first transverse direction and / or the extent in the second transverse direction may be at least 3 times, such as at least 5 times, at least 10 times, at least 100 times, or at least 1000 times the height. Each individual intermediate layer may have a height in the height direction that is at most 50 nm, such as at most 100 nm, at most 250 nm, at most 500 nm, at most 1 pm or at most 5 pm. The device layer may be connected to the support layer at the second surface either directly so that the material of the device layer is in direct contact with the material of the support layer or indirectly so that an intermediate material, such as the at least one intermediate layer, is located in between the material of the device layer and the material of the support layer. The support layer, the device layer and the optional intermediate layers may be stacked above each other in the height direction. The deflection of the flexible section in the height direction may be perpendicular to a plane defined by the flat device layer. The deflection thus corresponds to an out-of-plane deflection of the flexible section. The deflection of the flexible section thus differs from an in-plane deflection, which would correspond to a deflection that is parallel to the plane defined by the flat device layer. The plane defined by the flat device layer is parallel to the first and second transverse direction in which the device layer transversely extends and parallel to the first and second surfaces of the device layer. The first and second surfaces each limit the device layer in the height direction. Consequently, the device layer is only located at one side from the first surface in the height direction and at one side from the second surface in the height direction. The strain sensing members may be made from a semiconductor material, such as from an inverse doped semiconductor material, such as: silicon, diamond, gallium arsenide, gallium nitride or made of a single-layer material, such as graphene, boron nitride; molybdenum nitride. The semiconductor material may be the material of the device layer. For example, the material of the device layer may be inversely doped to form the strain sensing members. FIGURES Fig, 1 is a longitudinal cross-section of an off-plane bendable flexure section, as cantilever or similar with double-side embedded four strain sensing members, according to the current invention. Fig. 2 displays full bridge detector circuit of four double-side located strain sensing members, according to the current invention. Fig. 3 is a longitudinal cross-section of an off-plane bendable flexure section, as a micromembrane or similar with double-side embedded four strain sensing members, according to the current invention. Fig. 4 is a longitudinal cross-section of an off-plain bendable flexure section with double-side embedded strain sensing members and increased sensitivity by modifying the thickness of freestanding portion, according current invention. Fig. 5 is a longitudinal cross-section of an off-plain bendable flexure section with double-side embedded strain sensing members, at least one of the members on first surface is further provided with a voltage transmitting member G. Fig. 6 displays full bridge detector circuit of four double-side located strain sensing members, two of them provided with a voltage-controlled resistance, according to the current invention. DETAILED DESCRIPTION Exemplary micromechanical device 1 shown in Fig. 1, comprises a flat flexure element, exemplarily formed by a flexible section 2, having a first surface 51 and a second surface 52. The flexible section 2 is protruding out of or from a thick and rigid support layer 3. The flexible section 2 thereby protrudes from a support structure 30 formed in the support layer 3. The flexible section 2 further comprises, an optional intermediate oxide layer 4 disposed on the second surface 52 of the flexible section 2, a device layer 5 with a freestanding portion 5’ and an optional further insulation layer 6 disposed on the first surface 51 of the flexible section 2. When the flexible section 2 is off-plane bended in a height direction Z perpendicular to the first and second surfaces 51, 52, in the areas located near its upper and lower surfaces formed by the first surface 51 and the second surface 52, respectively, mechanical strains of maximum amplitude and opposite sign are generated. Thus, optimal sensitivity may be achieved if strain sensing members 7'u and 7k are located at said two surfaces 51,52 of the flexible section 2, which may form a microcantilever, a thin micromembrane, or the like. The strain sensing members 7'u and 7k thereby may be located on the surfaces 51,52 or integrated into the surfaces 51,52. As shown in Fig. 1, the first and second surfaces 51,52 extend in a plane parallel to a first transverse direction Y and parallel to a second transverse direction X. The height direction Z is orientated perpendicular to the first and second transverse direction Y, Z. The surfaces 51,52 form surfaces of the device layer 5. The device layer 5 is placed on top of the support layer 3 in the height direction Z and partly overlaps the support structure 30 formed in the support layer 3 in the height direction Z. Furthermore, the device layer 5 extends from the support structure 30 along the second transverse direction Y, forming the freestanding portion 5’. The support structure 30 is formed from the support layer 3 that is located adjacent the device layer 5 in the height direction Z, whereby the support layer 3 has been removed in a region adjacent the freestanding portion 5’ of the device layer 5, for example by etching and the remaining parts of the support layer 3 comprise the support structure 30. The support structure 30 and the support layer 3 thereby may be spaced from the device layer 4 by intermediate layers, such as by the intermediate oxide layer 4, or they may be directly adjacent the device layer 5. The device layer 5 and the support layer 3 are orientated parallel to each other and both extend in the first and second transverse directions Y, X. A transverse extent of the device layer 5, the support layer 3, the freestanding portion 5’ and the support structure 30 in the first and second transverse directions Y, X thereby is larger than respective heights of the device layer 5, the support layer 3, the freestanding portion 5’ and the support structure 30 in the height direction Z. According to a general embodiment of the present disclosure, pairs of strain sensing members 7'u, 7'l, piezoresistors or similar, are located at two parallel surfaces 51,52 of a flat flexible section 2, that is bendable in the height direction Z orthogonal to said surfaces, 51,52. The strain sensing members 7'u, 7'l of each pair are aligned to each other in both horizontal directions Y, X parallel to said surfaces 51,52 and located at the opposite surfaces 51,52 of the freestanding portion 5’. Furthermore, they are placed at a minimum distance A from each other in the height direction Z, and both strain sensing members 7'u, 7'l of each pair have substantially the same shape, the same size and same coordinates in a horizontal plane parallel to said surfaces 51, 52 and the same resistances, with a relative difference AR / R of the resistance values <1%, preferably <0.5%. Being closely and oppositely placed, typically at distance A between the strain sensing members 7'u, 7'l of each pair, which distance ranges from 0.5pm to above 20 pm, preferably from 0.7pm to above 10 pm, both strain sensing members 7'u, 7'l of a respective pair are exposed at same stimuli having impact on the value of their resistances, which determines a compensation of the respective responds when electrically connecting them in differential configuration. Thus, several sources of noise, can be simultaneously compensated. The smaller is the distance A, also the smaller is the time-constant of the equilibrium achieved after any external impact on both said strain sensing members 7'u, 7'l of each pair. With some embodiments of the present disclosure, the micromechanical device 1 may comprise two pairs of strain sensing members 7'u, 7'l, a first pair having two strain sensing members 71u, 71l located above each other at the first and second surface 51,52, respectively, and a second pair having two strain sensing members 72u, 72l located above each other at the first and second surface 51, 52, respectively. The first pair comprises a first strain sensing member 71u located at the first surface 51 and a second strain sensing member 71l located at the second surface 52. Furthermore, the second pair comprises a third strain sensing member 72u located at the first surface 51 and a fourth strain sensing member 72l located at the second surface 52. The first strain sensing member 71u and the third strain sensing member 72u may be shifted with respect to each other parallel to the first surface 51 and / or the second strain sensing member 71l and the fourth strain sensing member 72l may be shifted with respect to each other parallel to the second surface 52. For example, the first and third strain sensing members 71u, 72u may be shifted with respect to each other parallel to an edge direction of an edge of the support structure 30 and the support layer 3 from which the freestanding portion 5’ protrudes. As shown in Fig. 1, this edge direction is parallel to the first transverse direction X. Additionally or alternatively, the second and fourth strain sensing members 71l, 72l may be shifted with respect to each other parallel to the edge direction. Furthermore, the first and second strain sensing member 71u, 72u and the third and fourth strain sensing member 71 l, 72l may be located on top of each other in the height direction Z on the opposing surfaces 51, 52. In general, the first pair of strain sensing members 71u, 71l and the second pair of strain sensing members 72u, 72l may be shifted with respect to each other along the edge direction. As shown in Fig. 1, at least one pair of strain sensing members 7'u, 7'l may be located in an edge region at the edge from which the freestanding portion 5’ protrudes. In particular, both pairs of strain sensing members 7'u, 7'l may be located in the edge region. Fig. 1 shows one of the pairs of strain sensing members 7'u, 7'l with the strain sensing members 7'u, 7'l of that pair located on top of each other in the height direction Z and being aligned which each other parallel to the surfaces 51,52 in a plane perpendicular to the height direction Z. The strain sensing members 7'u, 7'l further are located in the edge region at the edge from which the freestanding portion 5’ protrudes. The other one of the pairs of strain sensing members 7'u, 7'l may have the same configuration and may be shifted with respect to the one of the pairs of strain sensing members 7'u, 7'l shown in Fig. 1 parallel to the second transverse direction X. For such a configuration, both a cut through the one of the pair of strain sensing members 7'u, 7'l and a cut through the other one of the pair of strain sensing members 7'u, 7'l would look like the sectional view shown in Fig. 1. In the embodiment of this invention shown in Fig. 1, a cross-section of a micromechanical device 1, comprising a freestanding portion 5’ being shaped as a micro bulk, also called cantilever, is displayed. The thick and rigid support layer 3 is handling the protruding freestanding portion 5’ that further comprises the flexible section 2 having thickness c / c- A thickness of the support layer 3 in the height direction is larger than a thickness of the device layer 5, for example by a factor of at least 2, 5 10 or 100. Exemplarily, the freestanding portion 5’ forms the flexible section 2. The freestanding portion 5’ is made of silicon and has two thin insulating layers of e.g. an intermediate oxide layer 4 on the second surface 52 and a further insulating layer 6 on the first surface 51, both of which are optional. The freestanding portion 5’ of the micromechanical device 1 may be exploited in atomic force microscopy (AFM), for detection of the chemical composition of gases or etc., and has a length L along the first transverse direction Y in the range from about 10 pm to about 600pm, preferably from about 50pm to 450pm, and a width W along a second transverse direction X, (the width W being not shown in the Fig. 1), in the range from about 2pm to about 250pm, preferably from 10 pm to 120pm. In this embodiment two pairs of strain sensing members 7, which may be configured as piezoresistors, are embedded on both opposite surfaces of the freestanding portion 5’. Here, the figure shows only one of the two identical strain sensing members 7'u and 7'l of one of the pairs, which are double-side located in an area of thickness dR, which in the particular case is equal to the thickness de (dR = de) of the silicon freestanding portion 5’, respectively, having a thickness along the height direction Z in the range from about 0.5pm to about 10pm, preferably from 0.7pm to about 6pm. The four strain sensing members 7'u and 7'l, i = 1,2 of the two pairs are conductively connected in a full bridge configuration shown in Fig. 2. For example, they form a Wheatstone bridge. The four sensitive strain sensing members 7'u and 7'l, i = 1,2 of the full bridge, are located in pairs and are substantially identical to each other, respectively: two strain sensing members 7'u are located on the first surface 51, and two strain sensing members 7'l are located on the second surface 52. Optionally, said strain sensing members 7 are disposed in a horizontal plane parallel to the first and second transverse directions Y, X between two vias 80. The vias 80 comprise corresponding, also double-side placed, heavily doped electrically conducting regions 8 and 9 doped with dopants ensuring same type of conductivity. Said electrically conducting regions 8 and 9, being located at a distance 61 along the height direction Z, are insulated from each other, elsewhere but not in depressions 10. In vicinity of the said depressions 10, electrically conducting region 8 overlaps electrically conducting region 9 in the height direction Z which provides a desired galvanic contact between them. Remaining areas of electrically conducting region 9 are locally electrically isolated from opposite areas of electrically conducting region 8. For this purpose, the specific design of the micromechanical device 1 includes single or a plurality of depressions 10 of minimum horizontal dimensions located within the said electrically conducting regions 9 of the vias 80 on the first surface 51. Further, electrical conductors 11 i ( / = 1, 2, 3), typically made of patterned metal tracks, are provided. Despite said electrical conductors 11 i ( / = 1, 2, 3) are single-side located on the upper first surface 51 of the micromechanical device 1, they connect each pair of double-sided embedded planar strain sensing members 7'u and 7'l, i = 1,2, in voltage dividers 12i, 122 via the vias 80. Both dividers 12i, 122 are connected into a full bridge circuit detector 13, shown in Fig. 2, forming a Wheatstone bridge. The detector 13 comprises the full bridge circuit. In the exemplary embodiment, the detector 13 consists of the full bridge circuit. Specifically, the individual signals generated by both strain sensing members 7'u and 7'l in a pair, in response to the bending the flexible section 2 in the orthogonal direction to the surfaces 51,52, that is in the height direction Z, have the same amplitudes and the opposite signs, while the response to the synphase stimuli have the same value and sign. Thus, upon connecting of the said two planar strain sensing members 7'u and 7'l in one of the voltage dividers 12i or 122, a twofold voltage amplification of the signals associated with the response of the out of plane bending is provided, and a high degree of compensation the response to all other stimuli, is simultaneously achieved. Furthermore, according to design rules known to those skilled in the art, the electric current flows in a horizontal direction perpendicular to the height direction Z between the electrical conductors 11 i connecting the strain sensing members 7'u and 7'l, but not in a vertical direction parallel to the height direction Z between them, whereby the current 112 between the electrical conductors 111 and H2 is substantially the same as the current I23 between the electrical conductors H2 and 113, and for the current 112 and the current I13 between the conductor 112 and the conductor 113 the relationship is valid: 113 <10-3.112 (2), preferably, h3 <104. h2 (3) The conductors 11 i located on the first surface 51 are used, as follows: a first conductor 111 forms a supply voltage conductor to provide supply voltage Vcc, a further conductor 112 is a sensing conductor to output signal Vout of a voltage divider 12i of the voltage dividers 12i, 122, an additional further conductor H’2 is a further sensing conductor to output signal Vout of a further voltage divider 122 of the voltage dividers 12i, 122, and a second conductor 113 is a ground conductor connected to a ground potential. In a similar manner, having inverse polarity of supply conductors to Vcc and ground, the other pair of strain sensing members 7'u and 7'l is also connected. Both voltage dividers 12i and 122 are connected in a full bridge circuit 110 of the detector 13, as shown in Fig. 2. The detector 13 shown in Fig. 2 comprises the first strain sensing member 71u located at the first surface 51 and the second strain sensing member 71l located at the second surface 52. The first strain sensing member 71u and the second strain sensing member 71l are connected in series in between the first conductor 111 and the second conductor 112. Furthermore, the further conductor 112 is connected in between the first strain sensing member 71u and the second strain sensing member 71l. The first strain sensing member 71u is connected in between the first conductor 111 and the second strain sensing member 71l via the further conductor 112. The second strain sensing member 71l is connected in between the second conductor 113 and the first strain sensing member 71u via the further conductor 112. The first strain sensing member 71u and the second strain sensing member 71l form the voltage divider 12i. The first strain sensing member 71u is directly connected to the first conductor 111 and the further conductor 112 and the second strain sensing member 71l is directly connected to the second conductor 113 and the further conductor 112. The detector 13 shown in Fig. 2 further comprises the third strain sensing member 72u located at the first surface 51 and the fourth strain sensing member 72l located at the second surface 52. The third strain sensing member 72u and the fourth strain sensing member 72l are connected in series in between the first conductor 111 and the second conductor 112. Furthermore, the additional further conductor 11 ’2 is connected in between the third strain sensing member 72u and the fourth strain sensing member 72l. The third strain sensing member 72u is connected in between the second conductor 1l2and the fourth strain sensing member 72l via the second conductor 112. The fourth strain sensing member 72l is connected in between the first conductor 111 and the third strain sensing member 72u via the additional further conductor H’2. The third strain sensing member 72u and the fourth strain sensing member 72l form the further voltage divider 122. The fourth strain sensing member 72l is directly connected to the first conductor 111 and the additional further conductor 11’2 and the third strain sensing member 72u is directly connected to the second conductor 113 and the additional further conductor 11’2. The voltage divider 12i and the further voltage divider 122 are connected in parallel between the first conductor 111 and the second conductor 112 to form the full bridge configuration. With the exemplary embodiment shown in Fig. 1, the strain sensing members 71u, 71l, 72u, 72l are piezoresistors. In general, the strain sensing members 71u, 71l, 72u, 72l form circuit elements of the detector 13 and the voltage dividers 122,122. In particular, the third strain sensing member 72u forms a first circuit element of the detector 13 and of the further voltage divider 122 and the fourth strain sensing member 72l forms a second circuit element of the detector 13 and of the further voltage divider 122. With other embodiments, some or all of the circuit elements may comprise transistors. The strain sensing members 71u, 71l, 72u, 72l may be elongated and extend in a length direction, wherein a respective extent of the strain sensing members 71u, 71l, 72u, 72l may be larger in the length direction than a respective extent in a direction perpendicular to the length direction. The length direction may be orientated parallel to the first transverse direction Y. In another embodiment of this invention shown in Fig. 3, a cross-section of a micromechanical device 1, comprising flexible section 2 with a freestanding portion 5’ being shaped as a silicon micromembrane, is displayed. As far as no differences are disclosed in connection with the description and the Figures, the embodiment shown in Fig. 3 is configured as it is disclosed in connection with the embodiment shown in Figures 1 and 2 and vice versa. The all-sides-clamped micromembrane 5’ has length L along the first transverse direction Y in the range from about 10 pm to about 600pm, preferably from about 50 pm to 450pm, and width W along the second transverse direction X, (not shown in the Fig. 3), in the range from about 10 pm to about 600pm, preferably from about 50 pm to 450pm, for exploitation in pressure sensing devices, microphones, microfluidic devices and alike. In this embodiment two pairs of strain sensing members 7 are embedded on both opposite surfaces of the micromembrane 5’. Here, the figure shows only one of the two identical strain sensing members 7'u and 7'l, which are double-side located in a flexible section of thickness dR, which in the particular case is equal to the thickness of the flexure de (dp = de), respectively, having thickness along the height direction Z in the range from about 0.5pm to about 10pm, preferably from 0.7pm to about 6pm. The thick and rigid support layer 3 having a support structure 30 with a shape of a rectangular frame is handling the said micromembrane 5’ having thickness de, that further comprises also two insulating layers of e.g. an intermediate oxide layer 4 and a further insulating layer 6, both of them being optional. The four strain sensing members 7'u and 7'l, i = 1,2 of the bridge, are located in pairs and are substantially identical to each other, respectively: two strain sensing members 7'u are located at the first surface 51, and two strain sensing members 7'l are located at the second surface 52. Said strain sensing members 7'u, 7'l are disposed in the horizontal plane between corresponding, also double-side placed, doped electrically conducting regions 8 and 9. Said conducting regions, being at a distance 5i along the height direction Z, are insulated from each other, elsewhere but not in specific depressions 10. In vicinity of the said depressions 10, electrically conducting regions 8 and 9 overlap in a vertical direction formed by the height direction Z which provides a desired galvanic contact between them. Further, electrical conductors 11 i ( / = 1, 2, 3), typically made of patterned metal tracks, are provided. Despite said conductors are single-side located on the first surface 51 of the micromechanical device 1, they connect each pair of double-sided embedded strain sensing members 7'u and 7'l, i = 1,2, in voltage dividers 12i, 122 and both dividers 12i, 122 are connected into the full bridge detector 13, shown in Fig. 2. Specifically, the individual signals generated by both strain sensing members 7'u and 7'l in a pair, in response to the bending the flexure in orthogonal direction to the surfaces 51,52, namely in the height direction Z, have the same amplitudes and the opposite signs, while the response to the synphase stimuli are the same in value and sign. Thus, upon connecting the pair of two strain sensing members 7'u, 7'l in a voltage divider 12i or 122, a twofold voltage amplification of the signals associated with the response of the out of plane bending is provided, and a high degree of compensation the response to all other stimuli, is simultaneously achieved. It is characteristic for the micromechanical device 1 that the full bridge detector 13 is made of four strain sensing members, 7'u and 7'l, i = 1,2, that are located on both sides of the micromembrane 5’ of thickness de. These strain sensing members, have substantially the same resistance. When strained, even if they are symmetrically located at a single clamping side of the micromembrane 5’, all four said strain sensing members 7 change their value of resistance with the same amplitude, generating sensor signals with two opposite signs. Thus, compared to the alternative devices with single side located strain sensing members on one of the surfaces 51,52 only, unexpectedly appears that shape of the micromembrane 1 is not mandatory to be square shaped. Thus, micromechanical devices 1 having rectangular shape membranes that fulfill the condition L + W (4) with a length L of the flexible section 2 in the first transverse direction Y that differs from a width W of the flexible section 2 in the second transverse direction X can have same sensitivity, as ones having square shaped flexible sections 2 or micromembranes formed by the freestanding portions 5’. In one embodiment of this invention, shown in Fig. 4, when aiming to further increase the sensitivity of a micromechanical device 1 comprising freestanding portion 5’ being shaped as a microcantilever of a length L along the first transverse direction Y and width W (not shown in the figure) along the second transverse direction X in comparison to alternative devices with single-side located strain sensing members, with a multiplication factor in the range >2.0, on one or on both surfaces of the microcantilever 5’ along its entire width W in the second transverse direction Y, recesses 14 and / or 15 are placed. Respectively, recess 15 is shaped on first surface 51 and recess 14 is shaped on the second surface 52. The recesses 14 and 15 have a depth in the range from about 0.5pm to about 5pm, preferably from 0.7pm to 3.0pm. They are set vertically in the height direction Z substantially above each other, and horizontally along the first transverse direction Y between electrically conducting regions 8 or 9. Optionally, when the depth of above mentioned of recesses 14 and / or 15 are less than the depth of the corresponding electrically conducting regions 8 or 9, the strain sensing members 7'u and 7'l, i = 1,2, can be in the bottoms of said recesses 14 or 15. Moreover, the local thickness dR of the microcantilever formed by the freestanding portion 5’ in the region of placement of the strain sensing members 7'u and 7'l, i = 1,2, is smaller than the thickness de of the remaining regions of the microcantilever 5’, i.e. dR <de. As a result, when off-plane bending the microcantilever 5’ in the height direction Z, the mechanical stresses in the vicinities of the sensitive strain sensing members 7'u and 7'l, i = 1,2, are further increased. The connection of the strain sensing members 7'u and 7'l, i = 1,2, in a full bridge detector 13, is the same as the embodiment shown in Fig. 2, which provides a further increase of the sensitivity of the micromechanical device 1. Optionally, the intermediate oxide layer 4 can be partially removed from the bottom side of the microcantilever formed by the freestanding portion 5’, as shown in the Fig. 4. For example, the microcantilever formed by the freestanding portion 5’ may be at least partly, for example completely, free of the intermediate oxide layer 4. In one embodiment of this invention, shown in Figs. 5, when aiming to achieve best control of the performance of the micromechanical device 1 of a length L along the first transverse direction Y and a width W (not shown in the figure) along the second transverse direction X, at least one of the strain sensing members 7'u located on the first surface 51 of the device layer 4 is further provided with a member Gi, i = 1, 2, also called “gate”, for voltage control of the resistance of said at least one strain sensing member 7'u. When a voltage is applied between the gate Gi and microcantilever 5’, the electric field creates an inversion layer or channel at the semiconductor surface formed by the respective first and second surface 51,52. Hence, total number of electric carriers in the surface layer, being also located in the region between electrically conducting regions 9, is changed. Thus, varying the voltage Vi between the gate Gi and substrate, a dynamic control of the resistance of said channel region between the electrically conducting regions 9, is ensured. The specific feature is that the value of the resistance of the strain sensing member 7'u can be controllably varied, thus providing different options to control the output voltage Voutof the detector 13 integrated in a micromechanical device 1. The connection of the four strain sensing members 7'u and 7'l, i = 1,2, in a full bridge detector 13, is displayed in Fig. 6. The value of the output voltage Vou;can be additionally driven by applying at least one voltage Vi on gates Gi. With the embodiment shown in Fig. 6, the first strain sensing member 71u comprises a first gate Gi for controlling the resistance of the first strain sensing member 71u and the third strain sensing member 72u comprises a second gate G2 for controlling the resistance of the third strain sensing member 72u. The second strain sensing member 71l and the fourth strain sensing member 7^ are configured without having a gate for changing their respective resistance. In general, both strain sensing members located at one of the first and second surfaces 51, 52, such as at the first surface 51, may have a gate for controlling their respective resistance and both strain sensing members located at the other one of the first and second surfaces 51,52, such as at the second surface 52, may be configured without such a gate. The strain sensing members having a gate for controlling the resistance may be configured as a channel of a transistor, such as a channel of a field effect transistor. Optionally, the intermediate oxide layer 4 can be partially removed from the bottom side of the flexure or left there, as shown in the Fig. 5. The configuration with one or several gates described in connection with Figures 5 and 6 may be employed with any of the devices described herein. Aspects of the present disclosure illustrated by the foregoing description are directed at the following enumerated embodiments: 1. Micromechanical device (1) comprising a device layer (5) with a flexible section (2), a support layer (3), a support structure (30) formed in the support layer (3), and a detector (13) for detecting deflection of the flexible section (2), wherein a first surface (51) of the device layer (5) and a second surface (52) of the device layer (5) are orientated parallel to each other and located on opposite sides of the device layer (5), wherein the first surface (51) and the second surface (52) extend parallel to a first transverse direction (Y) and a second transverse direction (X), the second transverse direction (Y) being perpendicular to the first transverse direction (X), wherein the device layer (5) is attached to the support layer (3) at the second surface (52), wherein the device layer (5) comprises a freestanding portion (5’) that extends from the support structure (30) in the first transverse direction (Y) and does not overlap with the support structure (30) in a height direction (Z) perpendicular to the first transverse direction (Y) and the second transverse direction (X), wherein the freestanding portion (5’) comprises the flexible section (2), wherein the flexible section (2) is configured to deflect in the height direction (X), wherein the detector (13) comprises a first strain sensing member (71u, 72u), a second strain sensing member (71l, 72l), and an electrical circuit (110) connected to the first strain sensing member (71u, 72u) and the second strain sensing member (71l, 72l), wherein the first strain sensing member (71u, 72u) is located at the first surface (51) within the flexible section (2) and the second strain sensing member (71l, 72l) is located at the second surface (52) within the flexible section (2). 2. Micromechanical device (1) according to embodiment 1, wherein the device layer (5) comprises, such as consists of, a semiconductor material. 3. Micromechanical device (1) according to at least one of the preceding embodiments, wherein each of the first strain sensing member (71u, 72u) and the second strain sensing member (71l, 72l) is selected from: a piezoresistor and a channel of a field effect transistor, wherein the piezoresistor or the channel of the field effect transistor comprise, such as are made of, an inverse doped semiconductor material, such as silicon, diamond, gallium arsenide, or gallium nitride, or comprise, such are made of, a single-layer material, such as graphene, boron nitride, or molybdenum nitride. 4. Micromechanical device (1) according to at least embodiment 3, wherein the first strain sensing member (71u, 72u) is selected from the piezoresistor and the channel of the field effect transistor, wherein the second strain sensing member (71l, 72l) is selected as the piezoresistor. 5. Micromechanical device (1) according to at least one of the preceding embodiments, wherein the first strain sensing member (71 u, 72u) is located above the second strain sensing member (71l, 72l) in the height direction (Z), wherein, for example, an outer contour of the first strain sensing member (71u, 72u) overlaps with an outer contour of the second strain sensing member (71l, 72l) in the height direction (Z). 6. Micromechanical device (1) according to at least one of the preceding embodiments, wherein the first strain sensing member (71u) and the second strain sensing member (71l) cover the same area in the first transverse direction (Y) and in the second transverse direction (Z). 7. Micromechanical device (1) according to at least one of the preceding embodiments, wherein the first strain sensing member (71u) and / or the second strain sensing member (71l) are elongated along the first transverse direction (Y). 8. Micromechanical device (1) according to at least one of the preceding embodiments, wherein a resistance of the first strain sensing member (71u) and a resistance of the second strain sensing member (71l) differ by at most 5%, such at most 2.5%, at most 1%, at most 0.75%, at most 0.5%, at most 0.25%, at most 0.1%, at most 0.075% or at most 0.05%. 9. Micromechanical device (1) according to at least one of the preceding embodiments, wherein the first strain sensing member (71u) and the second strain sensing member (71l) are electrically conductively connected in series. 10. Micromechanical device (1) according to at least one of the preceding embodiments, wherein the first strain sensing member (71u) extends in a length direction, wherein the second strain sensing member (71l) extends parallel to the first strain sensing member (71u) in the length direction, wherein the first strain sensing member (71u) and the second strain sensing member (71l) are electrically conductively connected to each other at the same end in the length direction. 11. Micromechanical device (1) according to at least embodiment 10, wherein the length direction is the first transverse direction (Y). 12. Micromechanical device (1) according to at least one of the preceding embodiments, wherein a sensing conductor (112) of the electrical circuit is electrically conductively connected to the first strain sensing member (71u) and to the second strain sensing member (71l) in between the first strain sensing member (71u) and the second strain sensing member (71l). 13. Micromechanical device (1) according to at least one of the preceding embodiments, further comprising a third strain sensing member (71u, 72u) and a fourth strain sensing member (71l, 72l), wherein the third strain sensing member (71u, 72u) is located at the first surface (51) and the fourth strain sensing member (71l, 72 J is located at the second surface (52). 14. Micromechanical device (1) according to at least embodiment 13, wherein the third strain sensing member (72u) and / or the fourth strain sensing member (72l) are located within the flexible section (2). 15. Micromechanical device (1) according to at least one of embodiments 13 and 14, wherein each of the third strain sensing member (72u) and the fourth strain sensing member (72l) is selected from: a piezoresistor and a channel of a field effect transistor, wherein the piezoresistor or the channel of the field effect transistor comprise, such as are made of, an inverse doped semiconductor material, such as silicon, diamond, gallium arsenide, or gallium nitride, or comprise, such as are made of a single-layer material, such as graphene, boron nitride, or molybdenum nitride. 16. Micromechanical device (1) according to at least embodiment 15, wherein the third strain sensing member (72u) is selected from the piezoresistor and the channel of a field effect transistor, wherein the fourth strain sensing member (72l) is selected as the piezoresistor. 17. Micromechanical device (1) according to at least one of embodiments 13 to 16, wherein the third strain sensing member (72u) is located above the fourth strain sensing member (72l) in the height direction (Z), wherein, for example, an outer contour of the third strain sensing member (72u) overlaps with an outer contour of the fourth strain sensing member (72l). 18. Micromechanical device (1) according to at least one of the preceding embodiments, wherein a resistance of the third strain sensing member (72u) and a resistance of the fourth strain sensing member (72l) differ by at most 5%, such at most 2.5%, at most 1%, at most 0.75%, at most 0.5%, at most 0.25%, at most 0.1%, at most 0.075% or at most 0.05%. 19. Micromechanical device (1) according to at least one of the preceding embodiments, wherein the third strain sensing member (72u) and the fourth strain sensing member (72l) are electrically conductively connected in series. 20. Micromechanical device (1) according to at least one of the preceding embodiments, wherein the first strain sensing member (71u) and the second strain sensing member (71l) are connected in series and form a voltage divider in between a first conductor (111) and a second conductor (113), wherein, for example, the first conductor (111) is a supply voltage conductor and the second conductor (113) is a ground conductor. 21. Micromechanical device (1) according to embodiment 20, wherein the detector (13) comprises a first circuit element (72u) and a second circuit element (72u), wherein the first circuit element (72u) and the second circuit element (72u) are connected in series and form a further voltage divider (12i) in between the first conductor (111) and the second conductor (113), wherein the further voltage divider (122) is electrically conductively connected in parallel to the voltage divider (12i). 22. Micromechanical device (1) according to at least embodiment 21, wherein a further sensing conductor (H2) of the electrical circuit (110) is electrically conductively connected to the first circuit element (72u) and to the second circuit element (72l) in between the first circuit element (72u) and the second circuit element (72l). 23. Micromechanical device (1) according to at least one of embodiments 21 to 22 and according to at least one of embodiments 13 to 17, wherein the first circuit element (72u) is configured as the third strain sensing member (72u) and / or the second circuit element (72l) is configured as the fourth strain sensing member (72l). 24. Micromechanical device (1) according to at least one of embodiments 21 to 23, wherein the first circuit element (72u) and / or the second circuit element (72l) are located within the flexible section (2). 25. Micromechanical device (1) according to at least one of embodiments 21 to 24, wherein the first strain sensing member (71u) is electrically conductively connected in between the first conductor (111) and the second strain sensing member (71l), wherein the first circuit element (72u) is electrically conductively connected in between the second conductor (113) and the second circuit element (72l). 26. Micromechanical device (1) according to at least one of embodiments 21 to 25, wherein the first circuit element (72u) is located at the first surface (51) and the second circuit element (72l) is located at the second surface (52). 27. Micromechanical device (1) according to at least embodiment 26, wherein the first circuit element (72u) is located above the second circuit element (72l) in the height direction (Z), wherein, for example, an outer contour of the first circuit element (72u) overlaps with an outer contour of the second circuit element (72u) in the height direction (Z). 28. Micromechanical device (1) according to at one of embodiments 21 to 27, wherein the first circuit element (72u) and the second circuit element (72l) cover the same area in the first transverse direction (Y) and the second transverse direction (X). 29. Micromechanical device (1) according to at least one of embodiments 21 to 28, wherein a resistance of the first circuit element (72u) and a resistance of the second circuit element (72l) differ by at most 5%, such at most 2.5%, at most 1%, at most 0.75%, at most 0.5%, at most 0.25%, at most 0.1%, at most 0.075% or at most 0.05%. 30. Micromechanical device (1) according to at least embodiment 29, wherein the resistances of the first strain sensing member (71u), the second strain sensing member (71l), the first circuit element (72u) and the second circuit element (72l) differ by at most 5%, such at most 2.5%, at most 1%, at most 0.75%, at most 0.5%, at most 0.25%, at most 0.1%, at most 0.075% or at most 0.05%. 31. Micromechanical device (1) according to at least one of the preceding embodiments, wherein the first strain sensing member (71u) is located within a recess (15) of the first surface (51) and / or the second strain sensing member (71l) is located within a recess (14) of the second surface (52). 32. Micromechanical device (1) according to at least embodiment 31, wherein a depth of the recess (15) in the height direction (Z) is at least 0.25pm, such as at least 0.5pm, at least 0.7pm or at least 1 pm and / or at most 7pm, such as at most 5pm or at most 3pm, wherein, for example, the depth of the recess (14) in the height direction (Z) is between 0.5pm and 5pm, such as between 0.7pm and 3.0pm. 33. Micromechanical device (1) according to at least one of the preceding embodiments, wherein the detector (13) comprises an electrically conducting via (80) that connects the first strain sensing member (71u) with the second strain sensing member (71l) through the freestanding portion (5’) of the device layer (5) in the height direction (Z), wherein, for example, the electrically conducting via (80) is located within the flexible section (2). 34. Micromechanical device (1) according to at least embodiment 33, wherein the electrically conducting via (80) comprises a depression (10) within one of the first surface (51) and the second surface (52), wherein the via (80) comprises an electrically conducting region (8, 9), for example formed by an inverse doped region of the device layer (5), extending from the one of the first surface (51) and the second surface (52) into the device layer (5) parallel to the height direction (Z), wherein the electrically conducting region (8, 9) overlaps with the depression (10) in the height direction (Z). 35. Micromechanical device (1) according to at least embodiment 34, wherein the via (80) comprises a further electrically conducting region (8, 9), for example formed by a doped region of the device layer (5), extending from the other one of the first surface (51) and the second surface (52) into the device layer (5) parallel to the height direction (Z), wherein the electrically conducting region (8, 9) and the further electrically conducting region (8, 9) are separated from each other by a distance in the height direction (Z) in a region offset from the via (80), wherein the depth of the depression (10) in the height direction (Z) is larger than the distance so that the electrically conducting region (8, 9) joins the further electrically conducting region (8, 9) at the via (80). 36. Micromechanical device (1) according to at least one of the preceding embodiments, wherein a distance A between the first strain sensing member (71u) and the second strain sensing member (71l) is between 0.5pm and 20 pm, for example between 0.7pm and 10 pm. 37. Micromechanical device (1) according to at least one of the preceding embodiments, wherein the strain sensing member (71u) comprises a doped area of the device layer (5), wherein, for example, the strain sensing member (71u) is formed as the doped area. 38. Micromechanical device (1) according to at least one of the preceding embodiments, wherein the material separating the first strain sensing member (71u) and the second strain sensing member (71l) is one of: a semiconductor, such as a doped semiconductor; gallium nitride; boron nitride; molybdenum nitride; and a single-layer material, such as graphene, wherein, for example, the semiconductor is silicon, gallium arsenide, gallium nitride. 39, Micromechanical device (1) according to at least one of the preceding embodiments, wherein the second surface (52) of the device layer (5) has a planar connection to the support layer (3). 40. Micromechanical device (1) according to at least one of the preceding embodiments, wherein the device layer (5) is bonded to the support layer (3) at the second surface (52). 41. Micromechanical device (1) according to at least one of the preceding embodiments, wherein the device layer (5) is made from a semiconductor one of: a semiconductor, such as an inverse doped semiconductor; gallium nitride; boron nitride; molybdenum nitride; and a single-layer material, such as graphene, wherein, for example, the semiconductor is silicon, gallium arsenide, gallium nitride. 42. Micromechanical device (1) according to at least one of the preceding embodiments, wherein the support layer (3) is made from one of: a semiconductor, such as a doped semiconductor; gallium nitride; boron nitride; molybdenum nitride; and a single-layer material, such as graphene, wherein, for example, the semiconductor is silicon, gallium arsenide, gallium nitride. 43. Micromechanical device (1) according to at least one of the preceding embodiments, wherein an intermediate oxide layer (4) is located in between the device layer (5) and the support layer (3) at the second surface (52). 44. Micromechanical device (1) according to at least embodiment 43, wherein at least part of the freestanding portion (5’), such as at least the flexible section (2) or the entire freestanding portion (5’), is free from the intermediate oxide layer (4). 45. Micromechanical device (1) according to at least one of the preceding embodiments, wherein an insulating layer (6) is located at the first surface (51). 46. Micromechanical device (1) according to at least one of the preceding embodiments, wherein a length (L) of the freestanding portion (5’) in the first transverse direction (Y) and a width of the freestanding portion (5’) in the second transverse direction (X) are larger than a height of the freestanding portion (5’) in the height direction (Z). 47. Micromechanical device (1) according to at least one of the preceding embodiments, wherein a length (L) of the freestanding portion (5’) in the first transverse direction (Y) is larger than a width of the freestanding portion (5’) in the second transverse direction (X). 48. Micromechanical device (1) according to at least one of the preceding embodiments, wherein a thickness (dp) of the device layer (5) and / or a thickness (dp) of the freestanding portion (5’) in the height direction (Z) is between 0.25pm and 40pm, such as between 0.5pm and 20pm or 0.7pm to 10pm, wherein, for example, the thickness (dp) of the device layer (5) and / or the thickness (dp) of the freestanding portion (5’) in the height direction (Z) is between 2pm and 250pm, such as between 10pm and 120pm. 49. Micromechanical device (1) according to at least one of the preceding embodiments, wherein a length (L) of the freestanding portion (5’) in the first transverse direction (Y) is at least 2.5pm, 5pm, 10pm, 20pm, 25pm or 50pm and / or at most 300pm, 500pm, 600pm, or 1mm, wherein, for example, the length (L) of the freestanding portion (5’) in the first transverse direction (Y) is between 10 pm and 600pm, such as between 50pm and 450pm. 50. Micromechanical device (1) according to at least one of the preceding embodiments, wherein a width of the freestanding portion (5’) in the second transverse direction (X) is at least 1 pm, 2 pm, or 5pm and / or at most 100pm, 250pm or 500pm, wherein, for example, a width of the freestanding portion (5’) in the second transverse direction (X) is between 2pm and 250|jm, such as between 10pm and 120pm. 51. Micromechanical device (1) according to at least one of the preceding embodiments, wherein the freestanding portion (5’) forms a cantilever that has a free end and a clamped end 5 located opposite the free end, wherein the freestanding portion (5’) is only connected to the support structure (30) and / or to the support layer (3) at the clamped end. 52. Micromechanical device (1) according to at least one of embodiments 1 to 51, 10 wherein the flexible section (2) has at least a first clamped end and a second clamped end located opposite the first clamped end, wherein the flexible section (2) is connected to the support structure (30) and / or to the support layer (3) at both the first clamped end and the second clamped end, wherein, for example, the flexible section (2) forms a micromembrane that has a connection to the 15 support structure (30) and / or to the support layer (3) that fully surrounds the freestanding portion (5’). Reference numeral list 1 micromechanical device 2 flexible section 3 support layer 4 oxide layer 5 device layer 5’ freestanding portion 6 insulating layer 71u first strain sensing member 71l second strain sensing member 72u third strain sensing member 72l fourth strain sensing member 8 conducting region 9 further conducting region 111 first conductor 112 further conductor 11 ’2 additional further conductor 113 second conductor 12i voltage divider 122 further voltage divider 13 detector 30 support structure 51 first surface 52 second surface 80 electrically conducting via 110 electrical circuit 111 further electrical circuit Y first transverse direction X second transverse direction Z height direction

Claims

1. Micromechanical device (1) comprising a device layer (5) with a flexible section (2), a support layer (3), an intermediate oxide layer (4), a support structure (30) formed in the support layer (3), and a detector (13) for detecting deflection of the flexible section (2), wherein a first surface (51) of the device layer (5) and a second surface (52) of the device layer (5) are orientated parallel to each other and located on opposite sides of the device layer (5), wherein the device layer (5) of semiconductor material is attached to the support layer (3) at the second surface (52), wherein the device layer (5) comprises a freestanding portion (5’) that extends from the support structure (30), wherein the flexible section (2) comprises the freestanding portion (5’), wherein the flexible section (2) is configured to deflect in the direction that is orthogonal to the first and second surfaces (51,52) of the device layer (5), wherein the detector (13) comprises a first strain sensing member (71u), a second strain sensing member (71l), a third strain sensing member (72u), and a fourth sensing member (72l), an electrical conductor (112) connected to the first strain sensing member (71u) and the second strain sensing member (71l), an electrical conductor (11’2) connected to the third strain sensing member (72u) and the fourth strain sensing member (72l), wherein the first strain sensing member (71u) and third sensing member (72u) are located at the first surface (51) within the flexible section (2) and the second strain sensing member (71l) and fourth strain sensing member (72l) are located at the second surface (52) within the flexible section (2).

2. Micromechanical device according to claim 1, wherein the first strain sensing member (71u) and third strain sensing member (72u) are a piezoresistor or a channel of a field effect transistor, made of inverse doped semiconductor material, such as: silicon, diamond, gallium arsenide, gallium nitride or made of a single-layer material, such as graphene, boron nitride; molybdenum nitride, and wherein the second strain sensing member (71l) and fourth sensing member (72l) is a piezoresistor made of said inverse doped semiconductor material.

3. Micromechanical device according to claims (1) to (2), wherein the first semiconductor strain sensing member (71u) is located above the second strain sensing member (71l), and third strain sensing member (72u) is located above the fourth strain sensing member (72l), wherein, for example, an outer contour of the first strain sensing member (71u) overlaps with an outer contour of the second strain sensing member (71l) and an outer contour of the third strain sensing member (72u) overlaps with an outer contour of the fourth strain sensing member (72l).

4. Micromechanical device (1) according to at least one of the preceding claims, wherein a resistance of the first strain sensing member (71u) and a resistance of the second strainsensing member (71l) differ by at most 0.5%, such at most 0.25%, at most 0.1%, at most 0.075% or at most 0.05%, andwherein a resistance of the third strain sensing member (72u) and a resistance of the fourth strain sensing member (72l) differ by at most 0.5%, such at most 0.25%, at most 0.1%, at most 0.075% or at most 0.05%.

5. Micromechanical device (1) according to at least one of the preceding claims, wherein the first strain sensing member (71u) and the second strain sensing member (71l) are electrically conductively connected in series, and wherein the third strain sensing member (72u) and the fourth strain sensing member (72l) are electrically conductively connected in series.

6. Micromechanical device (1) according to at least one of the preceding claims, wherein the first strain sensing member (71u) and the third strain sensing member (72u) is located within a recess (15) of the first surface (51) and / or the second strain sensing member (71l) and the fourth strain sensing member (72l) is located within a recess (14) of the second surface (52).

7. Micromechanical device (1) according to at least claim 6, wherein a depth of the recess (15) is at least 0.25pm, such as at least 0.5pm, at least 0.7pm or at least 1 pm and / or at most 7pm, such as at most 5pm or at most 3pm, wherein, for example, the depth of the recess (14) is between 0.5pm and 5pm, such as between 0.7pm and 3.0pm.

8. Micromechanical device (1) according to at least one of the preceding claims, wherein the electrical circuit (112) comprises an electrically conducting via (80) that connects the first semiconductor strain sensing member (71u) with the second strain sensing member (71l) through the freestanding portion (5’) of the device layer (5), wherein, for example, the electrically conducting via (80) is located within the flexible section (2).

9. Micromechanical device (1) according to at least claim 8,wherein the electrically conducting via (80) comprises a depression (10) within one of the first surface (51) and the second surface (52),wherein the via (80) comprises an electrically conducting region (9) or (8), for example formed by an inverse doped region of the device layer (5), extending from the one of the first surface (51) and the second surface (52) into the device layer (5), wherein the electrically conducting region (9) or (8) overlaps with the depression (10).

10. Micromechanical device (1) according to at least one of the preceding claims, wherein the material separating the first semiconductor strain sensing member (71u) and the second semiconductor strain sensing member (71l) is one of: a semiconductor, such as a doped semiconductor; diamond, gallium arsenide, gallium nitride.

11. Micromechanical device (1) according to at least one of the preceding claims,wherein a further insulating layer (6) is located at the first surface (51).

12. Micromechanical device (1) according to at least one of the preceding claims,wherein a thickness of the device layer (5) and / or a thickness of the freestanding portion (5’) is between 0.25pm and 40pm, such as between 0.5pm and 20pm or 0.7pm to 10pm,13. Micromechanical device according to at least one of the preceding claims, wherein a length of the freestanding portion (5’) is at least 2.5pm, 5pm, 10pm, 20pm, 25pm or 50pm and / or at most 300pm, 500pm, 600pm, or 1mm, wherein, for example, the length of the freestanding portion is between 10 pm and 600pm, such as between 50pm and 450pm.

14. Micromechanical device (1) according to at least one of the preceding claims, wherein a width of the freestanding portion (5’) is at least 1pm, 2pm, or 5pm and / or at most 100pm, 250pm or 500pm, wherein, for example, a width of the freestanding portion is between 2pm and 250pm, such as between 10pm and 120pm.

15. Micromechanical device (1) according to at least one of the preceding claims, wherein the freestanding portion (5’) forms a cantilever that has a free end and a clamped end located opposite the free end, wherein the freestanding portion (5’) is only connected to the support structure (30) and / or the support layer (3) at the clamped end.

16. Micromechanical device (1) according to at least one of claims 1 to 14, wherein the freestanding portion (5’) has at least a first clamped end and a second clamped end located opposite the first clamped end, wherein the freestanding portion (5’) is connected to the support structure (30) and / or to the support layer (3) at both the first clamped end and the second clamped end, wherein, for example, the freestanding portion (5’) forms a membrane that has a connection to the support structure (30) and / or to the support layer (3) that fully surrounds the freestanding portion (5’).

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