Claims:1. A method of fabricating a MEMS device for facilitating sensing applications, said method comprising:
depositing an insulating layer of a predefined thickness on top of a substrate;
forming a photoresist layer on the insulating layer and a first patterning of the insulating layer with a predefined metal element and the photoresist, wherein the first patterning of the insulating layer with the predefined metal element and the photoresist forms a patterned structure;
performing a first dry etching of the insulating layer using the patterned structure;
performing a second dry etching of the substrate after a second patterning of the insulating layer and the photoresist using the formed patterned insulating layer structure, wherein based on the deposition, the first patterning and the second patterning and etching, a suspended structure having a meandering path is developed.
2. The method as claimed in claim 1, wherein the insulating layer is deposited using chemical vapor deposition.
3. The method as claimed in claim 1, wherein the first patterning is obtained by lithography and lift off.
4. The method as claimed in claim 1, wherein the first dry etching corresponds to a reactive ion anisotropic etching.
5. The method as claimed in claim 1, wherein the second dry etching corresponds to isotropic etching of the substrate.
6. The method as claimed in claim 1, wherein the substrate is a semiconductor material of a predefined thickness.
7. The method as claimed in claim 1 wherein the insulating material is a dielectric material.
8. A MEMS device for facilitating sensing applications, said device comprising:
an insulating layer of a predefined thickness disposed on top of a substrate;
a photoresist deposited on the insulating layer, wherein a first patterning is performed on the insulating layer with a predefined metal element and the photoresist, wherein the first patterning of the insulating layer with the predefined metal element and the photoresist forms a patterned structure;
a first dry etch of the insulating layer using the patterned structure;
a second dry etch of the substrate formed after a second patterning of the insulating layer and the photoresist based on the formed patterned insulating layer structure, wherein based on the deposition, the first patterning and the second patterning and etching, a suspended structure having a meandering path is developed.
9. The device as claimed in claim 8, wherein the device is any or a combination of actuator and sensor.
10. The device as claimed in claim 9, wherein the sensor is any or a combination of a micro heater, a vacuum sensor, a mass flow sensor, a thermal accelerometer, a temperature sensor and a gas sensor.

, Description:TECHNICAL FIELD
[0001] The present disclosure relates generally to MEMS design. In particular, the present disclosure relates to design of suspended patterned MEMS device for facilitating multiple sensing applications.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Bulk micromachining defines structures by selectively etching inside a substrate. Whereas surface micromachining creates structures on top of a substrate, bulk micromachining produces structures inside a substrate. Usually, silicon wafers are used as substrates for bulk micromachining, as they can be anisotropically wet etched, forming highly regular structures. Wet etching typically uses alkaline liquid solvents, such as potassium hydroxide (KOH) or tetra methyl ammonium hydroxide (TMAH) to dissolve silicon which has been left exposed by the photolithography masking step. These alkali solvents dissolve the silicon in a highly anisotropic way, with some crystallographic orientations dissolving up to 1000 times faster than others. Such an approach is often used with very specific crystallographic orientations in the raw silicon to produce V-shaped grooves. The surface of these grooves can be atomically smooth if the etch is carried out correctly, and the dimensions and angles can be precisely defined. Pressure sensors are usually created by bulk micromachining technique. Bulk micromachining starts with a silicon wafer or other substrates, which is selectively etched, using photolithography to transfer a pattern from a mask to the surface. Like surface micromachining, bulk micromachining can be performed with wet or dry etching, although the most common etch in silicon is the anisotropic wet etch. This etching takes advantage of the fact that silicon has a crystal structure, which means its atoms are all arranged periodically in lines and planes. Certain planes have weaker bonds and are more susceptible to etching. The etch results in cavities that have angled walls, with the angle being a function of the crystal orientation of the substrate.
[0004] In the present scenario, suspended designed MEMS structures are released by wet etching technique where there is high risk of defective devices also having low or poor yields. The devices developed in the literature are researched and shown results on single application. Moreover, the membrane type device in micron level with series of fabrication steps has issues with film stress which impose constraints with the area of the design, when wet etching technique is used. This leaves a residues and also has stiction related issues for different device dimension. The presence of such a structure which supports the membrane suffers from the long response time which in-turn results in high power consumption and it is not adequate for in systems requiring quick response.
[0005] There is, therefore, a requirement in the art for a methodology in fabricating bulk micro-machined meandering patterned suspended structure that would mitigate the disadvantages in the prior art.

OBJECTS OF THE PRESENT DISCLOSURE
[0006] Some of the objects of the present disclosure, which at least one embodiment herein satisfies are as listed herein below.
[0007] An object of the present disclosure is to provide for a device that facilitates compensation of the stress of the film.
[0008] An object of the present disclosure is to provide for a dry etching technique which does not lead to residue issue which is prevalent in wet etching.
[0009] An object of the present disclosure is to provide for a device that enables very fast response time and low power consumption i.e., <1ms and <10mW for operating voltage of 1V.
[0010] An object of the present disclosure is to provide for a device that can be used in multiple areas of application.
[0011] An object of the present disclosure is to provide for a device that could be used in vacuum based measurements, viz; biological (Body temperature, wearable sensor etc.,), and space applications, as temperature sensors replacing platinum sensors, and the like which can generate localized temperature in the range of room temperature to 440 deg C.
[0012] An object of the present disclosure is to provide for a device that can be easily integrated on a sigle chip along with electronics circuit.

SUMMARY
[0013] The present disclosure relates to design of a meandering patterned suspended MEMS device for facilitating multiple sensing applications.
[0014] In an aspect, the present disclosure provides a method of fabrication of a MEMS device for facilitating sensing applications. The method may include the steps of depositing an insulating layer of a predefined thickness on the top of a substrate, thus forming a photoresist layer on the insulating layer and a first patterning of the insulating layer with a predefined metal element and the photoresist. The first patterning of the insulating layer with the predefined metal element and the photoresist may allow forming a patterned structure. The method may also include the steps of performing a first dry etching of the insulating layer using the patterned structure, followed by performing a second dry etching of the substrate after a second patterning of the insulating layer and the photoresist using the formed patterned insulating layer structure. Based on the deposition, the first patterning and the second patterning and etching, a suspended meandering path structure may be developed.
[0015] In an embodiment, the insulating layer may be deposited by chemical vapor deposition.
[0016] In an embodiment, the first patterning may be obtained by lithography and lift off process.
[0017] In an embodiment, the first dry etching may correspond to a reactive ion anisotropic etching.
[0018] In an embodiment, the second dry etching may correspond to isotropic etching of the substrate.
[0019] In an embodiment, the substrate may be a semiconductor material of a predefined thickness.
[0020] In an embodiment, the insulating material may be a dielectric material.
[0021] In an aspect, a MEMS device for facilitating sensing applications is provided. The device may include an insulating layer of a predefined thickness disposed on top of a substrate, a photoresist deposited on the insulating layer. A first patterning may be performed on the insulating layer with a predefined metal element and the photoresist, and the first patterning of the insulating layer with the predefined metal element and the photoresist may form a patterned structure. The device may include a first dry etch of the insulating layer using the patterned structure and a second dry etch of the substrate formed after a second patterning of the insulating layer and the photoresist based on the formed patterned insulating layer structure. Based on the deposition, the first patterning and the second patterning and etching, a suspended meandering path structure may be developed.
[0022] In an embodiment, the device may be any or a combination of actuator and sensor.
[0023] In an embodiment, the device may be any or a combination of a micro heater, a vacuum sensor, a mass flow sensor, a thermal accelerometer, a temperature sensor and a gas sensor.

BRIEF DESCRIPTION OF DRAWINGS
[0024] The accompanying drawings are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present invention and, together with the description, serve to explain the principles of the present invention.
[0025] FIG. 1 illustrates an exemplary suspended meandered patterned MEMS device structure, in accordance with an embodiment of the present disclosure.
[0026] FIG. 2 illustrates an exemplary flow diagram of the proposed method in accordance with an embodiment of the present disclosure.
[0027] FIG. 3 illustrates exemplary steps in the design of the proposed device, in accordance with an embodiment of the present disclosure.
[0028] FIG. 4 illustrates exemplary scanning electron microscope (SEM) image of released structure of the proposed device, in accordance with an embodiment of the present disclosure.
[0029] FIGs. 5A-5E illustrate exemplary structural analysis of the proposed device, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0030] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0031] Exemplary embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. These exemplary embodiments are provided only for illustrative purposes and so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those of ordinary skill in the art.
[0032] The present invention provides solution to the above-mentioned problem in the art by providing a method for designing MEMS device. Particularly, a MEMS device for multiple sensing applications can be designed based on CMOS compatible Dry etching technique which avoids residue issue existed from wet etching.
[0033] FIG. 1 illustrates an exemplary suspended meandered patterned MEMS device structure, in accordance with an embodiment of the present disclosure.
[0034] As illustrated, a MEMS device 100 (also referred to as device 100 herein after) can include a substrate 106. In an exemplary embodiment, the substrate can be Silicon (referred to as Si hereinafter) substrate but not limited to the like.
[0035] The device 100 may include an insulating layer 104 of a predefined thickness disposed on top of the substrate 106. A photoresist 102 may be deposited on the insulating layer 104. In an embodiment, the device 100 may be fabricated on a Si chip along with electronics, but not limited to it.
[0036] In an embodiment, the insulating layer 104 may include any dielectric material such as SiN, SiO2 and the like. In another embodiment, the photoresist 102 may include polymer, a sensitizer, and a solvent and but not limited to the like.
[0037] In an exemplary embodiment, a first patterning of the insulating layer 104 with a predefined metal element 110 and the photoresist 102 may form a patterned structure. The device may include a first dry etch of the insulating layer 104 using the patterned structure and a second dry etch of the substrate 102 formed after a second patterning of the insulating layer and the photoresist based on the formed patterned insulating layer structure. Based on the deposition, the first patterning and the second patterning and etching, a suspended meandering path structure 108 may be developed.
[0038] In an embodiment, the predefined metal element may include metals such as Platinum, Titanium and the like. In an embodiment, the insulating layer is deposited with methods including Low pressure chemical vapor deposition (LPCVD) or Plasma Enhanced chemical vapor deposition (PECVD) but not limited to the same. In an embodiment, the first patterning may be obtained by lithography and lift off but not limited to the like and the first dry etching may correspond to a reactive ion anisotropic etching but not limited to the like. In an embodiment, the second dry etching corresponds to isotropic etching of the substrate.
[0039] In an embodiment, the substrate is a semiconductor material of a predefined thickness.
[0040] FIG. 2 illustrates an exemplary flow diagram of the proposed method in accordance with an embodiment of the present disclosure.
[0041] In an aspect, the present disclosure provides for a method 200 for fabricating a MEMS device for facilitating sensing applications. The method may include at step 202, the step of depositing an insulating layer of a predefined thickness on top of a substrate and at step 204, forming a photoresist on the insulating layer and a first patterning of the insulating layer with a predefined metal element and the photoresist. In an embodiment, the first patterning of the insulating layer with the predefined metal element and the photoresist may form a patterned structure. The method may also include the step 206 of performing a first dry etching of the insulating layer using the patterned structure, and a step 208 of performing a second dry etching of the substrate after a second patterning of the insulating layer and the photoresist using the formed patterned insulating layer structure. Based on the deposition, the first patterning and the second patterning and etching, a suspended meandering path structure may be developed.
[0042] FIG. 3 illustrates exemplary fabrication steps in the design of the proposed device, in accordance with an embodiment of the present disclosure.
[0043] As illustrated, in an exemplary embodiment, Silicon sample 106 may be deposited with Silicon nitride 104 using Low Pressure Chemical Vapor deposition (LPVCD) or Plasma Enhanced Chemical Vapor deposition (PECVD) technique but not limited to the same. The Silicon nitride 104 may have a thickness of at least 1µm but not limited to it. The fabrication process then includes pattern transfer with any metal 110 such as Titanium, Platinum and the like using lithography and lift off method but not limited to it. The fabrication process may then include pattern transfer using lithography and then is followed by dry etching. In an exemplary embodiment, the dry etching may be performed by reactive ion etching with fluorine based chemistry but not limited to it. Reactive ion etching with fluorine based chemistry may be performed as an anisotropic etch of Silicon nitride but not limited to it. In an exemplary embodiment, isotropic etch may be performed for etching of Silicon for structure release.
[0044] FIG. 4 illustrates exemplary scanning electron microscope (SEM) image of released structure of the proposed device, in accordance with an embodiment of the present disclosure.
[0045] The SEM characterization was carried out for structural analysis and is illustrated in FIG. 4.
[0046] FIGs. 5A-5E illustrate exemplary structural analysis of the proposed device, in accordance with an embodiment of the present disclosure.
[0047] FIG. 5A illustrates response time measurement of the proposed device. As illustrated, in an exemplary implementation, response time measurements details show that the device is stable around <1ms. FIG. 5B illustrates power consumption of the proposed device. In an exemplary implementation, low power consumption of 35 mW was achieved with the proposed device for a temperature of 440 deg C as illustrated in FIG. 5B.
[0048] FIG. 5C illustrates life cycle measurement of the proposed device. In an exemplary implementation, life cycle measurement was carried for six lakh cycles and found that the device is still intact without any defect as can be seen in FIG. 5C. FIG. 5D illustrates resistance variation with respect to time from atmospheric pressure to 10e-6 Torr. In an exemplary implementation, the proposed device was tested under vacuum conditions in normal atmospheric pressure to 10E-6 torr changes in pressure and as illustrated in FIG. 5D the output changes by almost double the resistance value from the initial value.
[0049] FIG. 5E illustrates temperature vs resistance of the proposed device from -40 deg C to 120 deg C. In an exemplary implementation, the proposed device was tested as Temperature sensor and resistance measurement was carried out from -40 deg C to 120 deg C as shown in FIG. 5E.
[0050] It should be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive patent matter, therefore, is not to be restricted except in the spirit of the appended claims.
[0051] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

ADVANTAGES OF THE PRESENT DISCLOSURE
[0052] The present disclosure provides for a device that facilitates compensation of the stress of the film.
[0053] The present disclosure provides for a dry etching technique which avoids residue issue existed from wet etching.
[0054] The present disclosure provides for a device that enables very fast response time and low power consumption i.e., <1ms and <10mW for operating voltage of 1V.
[0055] The present disclosure provides for a device that can be used in multiple areas of application.
[0056] The present disclosure provides for a device that could be used in vacuum based measurements biological (body temperature, wearable sensor etc.,), space applications, as temperature sensors replacing platinum sensors, and the like which generates the temperature range from room temperature to 440 deg C.
[0057] The present disclosure provides for a device that can be easily integrated with electronics on chip, because the processes adopted here are compatible with the conventional chip process.