CN118062801A - MEMS devices - Google Patents

Abstract

A microelectromechanical (MEMS) device includes a substrate having a cavity, and a microelectromechanical structure disposed on the cavity and attached to the substrate. The microelectromechanical structure includes a plurality of cantilever portions, wherein each cantilever portion includes a free end and an anchor end. In addition, the micro-electromechanical device further comprises a membrane disposed over the micro-electromechanical structure, and the membrane comprises a plurality of protrusions respectively connected to the free ends of the cantilever portions. In addition, the microelectromechanical device includes a gap between the microelectromechanical structure and the membrane, the gap surrounding the protrusions.

Description

MEMS devices

Technical Field

The present invention relates to the technical field of micro electro mechanical system (MEMS) devices, and in particular to a MEMS device comprising a membrane vertically bonded to a MEMS structure.

Background technique

Micro-electromechanical (MEMS) devices are micro-components that are manufactured using existing semiconductor processes, such as depositing or selectively etching material layers. These micro-components contain electronic and mechanical functions and operate based on some effects, such as electromagnetic, electrostrictive, thermoelectric, piezoelectric, or piezoresistive effects. Therefore, MEMS devices are often used in microelectronic products, such as accelerometers, gyroscopes, acoustic sensors, etc.

Existing piezoelectric MEMS sensors use a diaphragm in most applications. The diaphragm has a cantilever structure that can bend or vibrate under sound pressure. The bending or vibration of the cantilever structure will generate stress in the diaphragm, thereby generating a corresponding electrical signal. However, the stress distribution generated by the cantilever structure is usually uneven, which greatly affects the performance of the piezoelectric MEMS sensor, for example, causing the piezoelectric MEMS sensor to have a low sensitivity. Therefore, the industry is in urgent need of technology that can improve the sensitivity of MEMS sensors.

Summary of the invention

In view of this, some embodiments of the present invention provide a micro-electromechanical system device capable of improving sensitivity. The micro-electromechanical system device includes a membrane vertically bonded to a micro-electromechanical structure to increase a sensing area, thereby improving the sensitivity of the micro-electromechanical system device.

According to one embodiment of the present invention, a micro-electromechanical device is provided, comprising a substrate, a micro-electromechanical structure, a diaphragm, and a gap between the micro-electromechanical structure and the diaphragm. The substrate has a cavity, and the micro-electromechanical structure is arranged on the cavity and attached to the substrate. The micro-electromechanical structure includes a plurality of cantilever portions, and each of the cantilever portions includes a free end and an anchor end. The diaphragm is arranged on the micro-electromechanical structure and includes a plurality of protrusions, which are respectively connected to the free ends of the cantilever portions. In addition, the gap surrounds the protrusions.

In order to make the features of the present invention more clearly understood, embodiments are given below with reference to the accompanying drawings for detailed description as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to make the following easier to understand, the drawings and their detailed text descriptions can be referred to when reading the present invention. Through the specific embodiments in this article and with reference to the corresponding drawings, the specific embodiments of the present invention are explained in detail and the working principles of the specific embodiments of the present invention are explained. In addition, for the sake of clarity, the features in the drawings may not be drawn according to the actual scale, so the size of some features in some drawings may be deliberately enlarged or reduced.

FIG. 1 is a schematic cross-sectional view of a micro-electromechanical system (MEMS) device according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a MEMS device according to another embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view of a MEMS device according to yet another embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view of a MEMS device according to yet another embodiment of the present invention.

FIG. 5 is a schematic top view of a MEMS structure, a substrate, and a diaphragm of a MEMS device according to an embodiment of the present invention.

FIG. 6 is a schematic top view of a MEMS structure, a substrate, and a diaphragm of a MEMS device according to another embodiment of the present invention.

FIG. 7 is a schematic top view of a MEMS structure, a substrate, and a diaphragm of a MEMS device according to yet another embodiment of the present invention.

FIG. 8 is a schematic top view of a MEMS structure, a substrate, and a diaphragm of a MEMS device according to yet another embodiment of the present invention.

9 and 10 are schematic cross-sectional views of some stages of a method for manufacturing a MEMS device according to an embodiment of the present invention.

100…MEMS devices

101…Base

101F…Front

101B…Back

101P…Part of the base

102…Cavity

102B…Bottom

102C…Shared cavity

102S…Sub-cavity

102W…Sidewall

103…Sacrificial layer

103E, 103P, 103W…Part of the sacrificial layer

104…Open

105…Sacrificial layer

107…Protective layer

110…MEMS structure

111…Seed layer

113, 115 ... sensing material layer

117…Passivation layer

120…Truncation

121…first electrode layer

123…Second electrode layer

125…Third electrode layer

127, 129…Contact pad

130…Cantilever part

140…Diaphragm

141…Suspension

142…Protrusion

144…Anti-adhesion barrier

150…Gap

A…Anchor end

F…Free end

L1, L2, L3, L4, L5, L6, L7, L8, L9, L10, L11, L12, L13, L14, L15, L16, L17, L18, L19, L20…distance

S101, S103, S105...steps

Detailed ways

The present invention provides several different embodiments that can be used to implement different features of the present invention. For the sake of simplicity of description, the present invention also describes examples of specific components and arrangements. The purpose of providing these embodiments is only for illustration, not for any limitation. For example, the description below for "a first feature is formed on or above a second feature" may refer to "the first feature is in direct contact with the second feature", or it may refer to "there are other features between the first feature and the second feature", so that the first feature and the second feature are not in direct contact. In addition, various embodiments of the present invention may use repeated reference symbols and/or text annotations. The use of these repeated reference symbols and annotations is to make the description more concise and clear, rather than to indicate the association between different embodiments and/or configurations.

In addition, for the spatially related descriptive words mentioned in the present invention, such as "under", "low", "down", "above", "on", "top", "bottom" and similar words, for the convenience of description, their usage is to describe the relative relationship between one element or feature and another (or multiple) elements or features in the drawings. In addition to the swing direction shown in the drawings, these spatially related words are also used to describe the possible swing direction of the semiconductor device during use and operation. As the swing direction of the semiconductor device is different (rotated 90 degrees or other orientations), the spatially related descriptions used to describe its swing direction should also be interpreted in a similar manner.

Although the present invention uses the terms first, second, third, etc. to describe various elements, components, regions, layers, and/or blocks, it should be understood that these elements, components, regions, layers, and/or blocks should not be limited by these terms. These terms are only used to distinguish a certain element, component, region, layer, and/or block from another element, component, region, layer, and/or block, and they themselves do not imply or represent any previous ordinal number of the element, nor do they represent the arrangement order of a certain element and another element, or the order in the manufacturing method. Therefore, without departing from the scope of the specific embodiments of the present invention, the first element, component, region, layer, or block discussed below can also be referred to as the second element, component, region, layer, or block.

The terms "about" or "substantially" mentioned in the present invention generally mean within 20% of a given value or range, preferably within 10%, and more preferably within 5%, or within 3%, or within 2%, or within 1%, or within 0.5%. It should be noted that the quantities provided in the specification are approximate quantities, that is, in the absence of a specific description of "about" or "substantially", the meaning of "about" or "substantially" can still be implied.

The terms "coupling", "coupling" and "electrical connection" mentioned in the present invention include any direct and indirect electrical connection means. For example, if the text describes that a first component is coupled to a second component, it means that the first component can be directly electrically connected to the second component, or indirectly electrically connected to the second component through other devices or connection means.

Although the present invention is described below by specific embodiments, the principles of the present invention may also be applied to other embodiments. In addition, in order not to obscure the spirit of the present invention, certain details will be omitted, and the omitted details belong to the knowledge scope of those with ordinary knowledge in the art.

The present invention relates to a micro-electromechanical (MEMS) device including a diaphragm vertically bonded to a micro-electromechanical (MEMS) structure, the MEMS structure including a plurality of cantilever portions, each cantilever portion including a free end and an anchor end. During operation of the MEMS device, the free end of the cantilever portion may bend and vibrate, thereby generating stress in the cantilever portion, and the stress is mainly concentrated at the anchor end of the cantilever portion. The diaphragm of some embodiments of the present invention can provide a larger sensing area for sensing environmental signals, such as pressure, velocity, gas, molecules, etc., and the diaphragm is connected to the free end of the cantilever portion to further increase the sensing area, thereby increasing the output of the electrical signal, thereby increasing the sensitivity of the MEMS device.

In addition, the diaphragm of some embodiments of the present invention is vertically integrated with the cantilever portion of the MEMS structure, so that the sensing area can be increased without expanding the size of the MEMS device. In addition, for the MEMS structure, under the same sensing area, the output of the electrical signal can be further increased by increasing the number of cantilever portions and reducing the size of the cantilever portions without expanding the size of the MEMS structure. The MEMS structure of some embodiments of the present invention is suitable for both piezoelectric and piezoresistive sensors, and the MEMS device is suitable for pressure sensors, microphones, energy grabbers, accelerometers, etc.

FIG. 1 is a cross-sectional schematic diagram of a microelectromechanical (MEMS) device 100 according to an embodiment of the present invention. As shown in FIG. 1 , the MEMS device 100 includes a substrate 101 having a cavity 102. The substrate 101 may be a semiconductor substrate, such as a silicon (Si) wafer or other suitable semiconductor wafers. In some embodiments, the cavity 102 may penetrate the substrate 101. In other embodiments, the cavity 102 may not penetrate the substrate 101 and extend from the front surface 101F of the substrate 101 to a height position in the substrate 101, wherein the front surface 101F is adjacent to the MEMS structure 110. The MEMS structure 110 includes a truncation portion 120 that penetrates the MEMS structure 110 and is located on the cavity 102 to form a plurality of cantilever portions 130. In some embodiments, each cantilever portion 130 may be a polygonal cantilever diaphragm, such as a triangle, a rectangle, a fork, etc. In other embodiments, each cantilever portion 130 may have a curved edge, such as a circle, an ellipse, etc. In some embodiments, the plurality of cantilever portions 130 may be a combination of several shapes. In addition, a plurality of cantilever portions 130 may be arranged in an array form.

In addition, the MEMS device 100 further includes a sacrificial layer 103 disposed between the substrate 101 and the MEMS structure 110. The sacrificial layer 103 has an opening 104 connected to the truncated portion 120 and the cavity 102. In the X-axis direction, the width of the opening 104 may be greater than the width of the cavity 102. In some embodiments, the material of the sacrificial layer 103 is, for example, silicon oxide (SiO ₂ ) or other suitable dielectric materials. The MEMS structure 110 is attached to the sacrificial layer 103 and the substrate 101. Each cantilever portion 130 of the MEMS structure 110 includes a free end F and an anchor end A, wherein the anchor end A is attached to the sacrificial layer 103 and the substrate 101, and the free end F is adjacent to the truncated portion 120 of the MEMS structure 110.

In one embodiment, the MEMS structure 110 includes a first electrode layer 121, a second electrode layer 123, a third electrode layer 125, a sensing material layer 113 disposed between the first electrode layer 121 and the second electrode layer 123, and another sensing material layer 115 disposed between the second electrode layer 123 and the third electrode layer 125. In another embodiment, the MEMS structure 110 includes a first electrode layer 121, a second electrode layer 123, and a sensing material layer 113 disposed between the first electrode layer 121 and the second electrode layer 123. In other embodiments, the MEMS structure 110 may include more than three electrode layers and more than two sensing material layers, wherein each sensing material layer is sandwiched between two electrode layers.

In some embodiments, the materials of the first electrode layer 121, the second electrode layer 123, the third electrode layer 125 and other electrode layers may be molybdenum (Mo), aluminum (Al), platinum (Pt), ruthenium (Ru), titanium (Ti), other suitable conductive materials or combinations thereof. In some embodiments of the present invention, the sensing material layers 113 and 115 and other sensing material layers may be piezoelectric materials, piezoresistive materials or other suitable sensing materials, wherein the piezoelectric material is, for example, aluminum nitride (AlN), scandium-doped AlN (ScAlN), zinc oxide (ZnO), lead zirconate titanate (PZT), gallium nitride (GaN), etc., and the piezoresistive material may be doped silicon (e.g., p-type Si), silicon carbide (SiC), etc.

As shown in FIG. 1 , in one embodiment, the MEMS structure 110 further includes a seed layer 111 disposed on the bottom surface of the first electrode layer 121, and a passivation layer 117 disposed on the top surface of the third electrode layer 125, and the truncation portion 120 also penetrates the passivation layer 117 and the seed layer 111. In some embodiments, the material of the seed layer 111 and the passivation layer 117 may be AlN, SiO ₂ or silicon oxynitride (SiON), but is not limited thereto. The MEMS structure 110 further includes a contact pad 127, which passes through the passivation layer 117, is disposed on the third electrode layer 125, and is electrically coupled to the first electrode layer 121 via a via. The MEMS structure 110 further includes another contact pad 129, which passes through the passivation layer 117, is disposed on the third electrode layer 125, and is electrically coupled to the second electrode layer 123 via another via hole, so that the electrical signals generated in the sensing material layers 113 and 115 can be transmitted to the external circuit through the electrode layers 121, 123 and 125 and the contact pads 127 and 129. In some embodiments, the material of the contact pads 127 and 129 can be aluminum-copper alloy (AlCu) or other suitable conductive materials.

According to some embodiments of the present invention, the MEMS device 100 further includes a diaphragm 140 vertically bonded to the MEMS structure 110, the diaphragm 140 includes a suspension portion 141 vertically separated from the MEMS structure 110, and a plurality of protrusions 142, the protrusions 142 are respectively connected to the free ends F of the cantilever portion 130 of the MEMS structure 110, for example, the protrusions 142 are connected to the passivation layer 117 located at the free ends F of the cantilever portion 130. There is a gap 150 between the MEMS structure 110 and the suspension portion 141 of the diaphragm 140, the gap 150 surrounds the protrusions 142 of the diaphragm 140, and the protrusions 142 are laterally separated from each other by the gap 150, and each protrusion 142 may be a columnar shape. In addition, the diaphragm 140 may be an integrally formed structure including a plurality of protrusions 142, and the material of the diaphragm 140 may be a semiconductor material such as silicon or polysilicon, a metal material such as Al, or a polymer material such as polyimide.

During the operation of the MEMS device 100, when an environmental signal, such as an acoustic wave, applies acoustic pressure to the MEMS structure 110, or an electrical signal is applied to the MEMS structure 110, the free end F of the cantilever portion 130 of the MEMS structure 110 may bend or vibrate, and the maximum stress may occur near the anchor end A of the cantilever portion 130. According to some embodiments of the present invention, the diaphragm 140 may be used as an additional larger sensing layer outside the MEMS structure 110 to sense the environmental signal, wherein the diaphragm 140 connected to the free end F of the cantilever portion 130 may increase the sensing area and increase the maximum stress occurring at the anchor end A of the cantilever portion 130, thereby improving the sensitivity of the MEMS device 100. In addition, the dimensions of the diaphragm 140, such as the length, width, and thickness, may be adjusted to further control the bending and vibration frequencies of the cantilever portion 130, thereby improving the performance of the MEMS device. In addition, since the diaphragm 140 is vertically bonded to the MEMS structure 110 , the area of the MEMS device will not be enlarged, thereby improving the sensitivity of the MEMS device 100 without increasing the XY plane size of the MEMS device 100 .

FIG. 2 is a cross-sectional schematic diagram of a MEMS device 100 according to another embodiment of the present invention. As shown in FIG. 2 , the MEMS device 100 includes a substrate 101 having a shared cavity 102C and a plurality of sub-cavities 102S, wherein the shared cavity 102C extends from a back surface 101B of the substrate 101 to a height position in the substrate 101, and the sub-cavity 102S extends from a front surface 101F of the substrate 101 to the height position of the substrate 101. The shared cavity 102C and the sub-cavity 102S can be formed by two different photomasks and two etching processes, respectively. The sub-cavities 102S are separated from each other by a portion 101P of the substrate 101, and the shared cavity 102C is connected to the sub-cavity 102S. The shared cavity 102C and the sub-cavity 102S can be collectively referred to as the cavity 102 of the substrate 101. In addition, the MEMS device 100 further includes a sacrificial layer 103 disposed between the substrate 101 and the MEMS structure 110. The sacrificial layer 103 has a portion 103P located between the portion 101P of the substrate 101 and the MEMS structure 110. In addition, the sacrificial layer 103 may have a plurality of openings 104, each connected to the sub-cavity 102S.

The difference between the MEMS device 100 of FIG. 2 and the MEMS device 100 of FIG. 1 is that the MEMS structure 110 of FIG. 2 includes more truncated portions 120, which penetrate the MEMS structure 110 to form more cantilever portions 130, wherein the anchor end A of the cantilever portion 130 is attached to the sacrificial layer 103 and the substrate 101, or to a portion 103P of the sacrificial layer and a portion 101P of the substrate 101, and the free end F of the cantilever portion 130 is adjacent to the truncated portion 120. In addition, the diaphragm 140 of the MEMS structure 110 of FIG. 2 includes more protrusions 142, which are respectively connected to the free ends F of the plurality of cantilever portions 130. In the embodiment of FIG. 2, the MEMS structure 110 thereof includes more and smaller cantilever portions 130 within the same area as the embodiment of FIG. 1. In this embodiment, these more and smaller cantilever portions 130 can generate more anchor ends A and more free ends F to further increase the electrical signal output, thereby improving the sensitivity of the MEMS device 100. In addition, the materials and detailed structures of other features of the MEMS device 100 of FIG. 2 may refer to the description of FIG. 1 .

FIG. 3 is a cross-sectional schematic diagram of a MEMS device 100 according to yet another embodiment of the present invention. The difference between the MEMS device 100 of FIG. 3 and the MEMS device 100 of FIG. 2 is that the sub-cavity 102S of the MEMS device 100 of FIG. 3 penetrates the substrate 101, and there is no shared cavity 102C of the MEMS device 100 of FIG. 2, wherein a portion 101P of the substrate 101 extends from the front surface 101F of the substrate 101 to the back surface 101B of the substrate 101. In addition, the diaphragm 140 of the MEMS device 100 of FIG. 3 further includes a plurality of anti-adhesion barrier members 144, which protrude toward the MEMS structure 110 and are separated from the MEMS structure 110 by a small gap, and the small gap is much smaller than the gap 105 between the suspended portion 141 of the diaphragm 140 and the MEMS structure 110. In some embodiments, the anti-adhesion barrier members 144 are disposed at the edge of the diaphragm 140, and the anti-adhesion barrier members 144 may be conical or pyramidal. During the operation of the MEMS device 100, when an environmental signal such as a sound wave applies sound pressure to the MEMS structure 110, or an electrical signal is applied to the MEMS structure 110, the free end F of the cantilever portion 130 of the MEMS structure 110 may bend or vibrate. In the present embodiment, when the cantilever portion 130 bends or vibrates, the anti-adhesion barrier 144 of the diaphragm 140 may contact the MEMS structure 110, thereby preventing the diaphragm 140 from adhering to the MEMS structure 110. In addition, in the present embodiment, more and smaller cantilever portions 130 may generate more anchor ends A and more free ends F to further increase the output of the electrical signal, thereby improving the sensitivity of the MEMS device 100. In addition, the materials and detailed structures of other features of the MEMS device 100 of FIG. 3 may refer to the description of the aforementioned FIG. 1 and FIG. 2.

FIG. 4 is a cross-sectional schematic diagram of a MEMS device 100 according to yet another embodiment of the present invention. The difference between the MEMS device 100 of FIG. 4 and the MEMS device 100 of FIG. 1 is that the cavity 102 of the MEMS device 100 of FIG. 4 does not penetrate the substrate 101. In this embodiment, the cavity 102 extends from the front surface 101F of the substrate 101 to a height position in the substrate 101, and the bottom surface 102B of the cavity 102 is located in the substrate 101. In addition, the MEMS device 100 of FIG. 4 includes a sacrificial layer 103 disposed between the substrate 101 and the MEMS structure 110, and the sacrificial layer 103 further includes a portion 103W disposed along the sidewall 102W of the cavity 102, and another portion 103E extending into the substrate 101. In addition, the sacrificial layer 103 has an opening 104 connected to the cavity 102, and the width of the opening 104 in the X-axis direction can be the same as the width of the cavity 102. The cavity 102 and the opening 104 can be formed by an etching process, and the cavity 102 and the opening 104 can be released from the front side of the MEMS device 100, and these portions 103W and 103E of the sacrificial layer 103 can be used to limit and control the size of the cavity 102. In this embodiment, the provision of the diaphragm 140 can increase the sensing area to improve the sensitivity of the MEMS device 100 without increasing the size of the MEMS device 100. In addition, the materials and detailed structures of other features of the MEMS device 100 of FIG. 4 can refer to the description of FIG. 1 above.

FIG5 is a schematic top view of a MEMS structure 110, a substrate 101, and a diaphragm 104 of a MEMS device according to an embodiment of the present invention, and a cross-sectional view of the MEMS device 100 of FIG1 can be obtained along the cross-sectional cut line I-I of FIG5. As shown in FIG5, in one embodiment, the MEMS structure 110 may include four cantilever portions 130, and these cantilever portions 130 are separated from each other by truncation portions 120. In this embodiment, each cantilever portion 130 is a triangle, and the truncation portions 120 intersect to form an X-shape, and each cantilever portion 130 has an anchor end A located at the bottom of the triangle and a free end F located at the top of the triangle. The four cantilever portions 130 of FIG5 have four distances L1, L2, L3, and L4, respectively, wherein each distance is from the anchor end A to the free end F, and the four distances L1, L2, L3, and L4 may be the same or different. In addition, the four cantilever portions 130 can be connected together through a portion of the MEMS structure 110 surrounding the four cantilever portions 130, so that those portions of the first electrode layer 121 located in the four cantilever portions 130 are electrically connected together in series, and those portions of the second electrode layer 123 located in the four cantilever portions 130 are also electrically connected together in series, and those portions of the third electrode layer 125 located in the four cantilever portions 130 are also electrically connected together in series, so that the electrical signals generated in the four cantilever portions 130 can be transmitted through the same contact pad.

In addition, as shown in FIG5 , when viewed from a top view, the edge of the diaphragm 140 extends outward beyond the edge of the cavity 102. In addition, the edge of the opening 104 of the sacrificial layer 103 may also extend outward beyond the edge of the cavity 102. In one embodiment, the diaphragm 140 may have twelve protrusions 142 connected to the free ends F and the sides of the four cantilever portions 130. In another embodiment, the diaphragm 140 may have four protrusions 142 connected to the free ends F of the four cantilever portions 130. In addition, the diaphragm 140 may also include four anti-adhesion blocking members 144 disposed at the edge of the diaphragm 140, but is not limited thereto. For example, the number of the anti-adhesion blocking members 144 may be two, three, or more than four.

FIG6 is a schematic top view of a MEMS structure 110, a substrate 101, and a diaphragm 140 of a MEMS device according to another embodiment of the present invention, and the cross-sectional view of the MEMS device 100 of FIG3 can be obtained along the cross-sectional cutting line II-II of FIG6. As shown in FIG6, in one embodiment, the MEMS structure 110 includes eight cantilever portions 130, and these cantilever portions 130 are separated from each other by the truncation portions 120. In this embodiment, each cantilever portion 130 is rectangular, and the truncation portions 120 intersect to form a cross shape. The four outer cantilever portions 130 in the X-axis direction have an anchor end A located outside the rectangle, and a free end F opposite to the anchor end A. The four inner cantilever portions 130 in the X-axis direction have an anchor end A located inside the rectangle, and a free end F opposite to the anchor end A, and the anchor end A and the free end F of each cantilever portion 130 are located on opposite sides of the rectangle. 3 , the anchor ends A of the four inner cantilever portions 130 are attached to a portion 101P of the substrate 101. In addition, the eight cantilever portions 130 have eight distances L1 to L8, each of which is from the anchor end A to the free end F, and the eight distances L1 to L8 may be the same or different. In addition, the eight cantilever portions 130 are connected together through a portion of the MEMS structure 110 surrounding the eight cantilever portions 130, and this portion of the MEMS structure 110 has a connecting portion connected to the eight cantilever portions 130, so that the portions of the first electrode layer 121 located in the eight cantilever portions 130 are electrically connected together in series, the portions of the second electrode layer 123 located in the eight cantilever portions 130 are also electrically connected together in series, and the portions of the third electrode layer 125 located in the eight cantilever portions 130 are also electrically connected together in series, so that the electrical signals generated in the eight cantilever portions 130 can be transmitted through the same contact pad. In addition, the number of the cantilever portions 130 is not limited to eight, for example, the number of the rectangular cantilever portions 130 may be two, four, six, or more than eight.

In addition, as shown in FIG6 , in one embodiment, the substrate 101 may have two sub-cavities 102S separated by a portion 101P of the substrate 101. When viewed from a top view, the edge of the diaphragm 140 extends outward beyond the edge of the two sub-cavities 102S. In addition, the edge of the opening 104 of the sacrificial layer 103 may also extend outward beyond the edge of the two sub-cavities 102S. In other embodiments, the number of sub-cavities 102S is not limited to two, for example, the number of sub-cavities 102S may be four, six or more, and the number of sub-cavities 102S may be adjusted according to the layout of the cantilever portion 130 and the truncation portion 120. In addition, the diaphragm 140 may have twenty-four protrusions 142 connected to the free ends F of the eight cantilever portions 130, but is not limited thereto, for example, the number of protrusions 142 may be eight, sixteen or other multiples of eight. In addition, the film 140 may further include six anti-adhesion barrier members 144 located at the edge of the film 140 , but is not limited thereto. For example, the number of the anti-adhesion barrier members 144 may be two, four, or more than six.

FIG. 7 is a schematic top view of a MEMS structure 110, a substrate 101, and a diaphragm 140 of a MEMS device according to yet another embodiment of the present invention. As shown in FIG. 7 , in one embodiment, the MEMS structure 110 includes eight cantilever portions 130, which are separated from each other by truncated portions 120. In this embodiment, each cantilever portion 130 is a triangle, and the truncated portions 120 intersect to form a cross and a rhombus, and each cantilever portion 130 has an anchor end A located at the bottom of the triangle and a free end F located at the top of the triangle. In addition, the eight cantilever portions 130 respectively have eight distances L1 to L8, wherein each distance is from the anchor end A to the free end F, and the eight distances L1 to L8 may be the same or different. In addition, the eight cantilever portions 130 may be connected together through a portion of the MEMS structure 110 surrounding the eight cantilever portions 130, for example, the portion of the MEMS structure 110 has a connecting portion, which is connected to the corner of the anchor end A located at the eight cantilever portions 130. Therefore, those parts of the first electrode layer 121 located in the eight cantilever parts 130 are electrically connected together in series, and those parts of the second electrode layer 123 located in the eight cantilever parts 130 are also electrically connected together in series, and those parts of the third electrode layer 125 located in the eight cantilever parts 130 are also electrically connected together in series, so that the electrical signals generated in the eight cantilever parts 130 can be transmitted through the same contact pad.

In addition, as shown in FIG. 7 , in one embodiment, the substrate 101 may have five sub-cavities 102S, which are separated from each other by a portion 101P of the substrate 101. When viewed from a top view, the edge of the diaphragm 140 extends outward beyond the edge of the five sub-cavities 102S. In addition, the edge of the opening 104 of the sacrificial layer 103 may also extend outward beyond the edge of the five sub-cavities 102S, and the layout of the sub-cavities 102S may be adjusted according to the layout of the cantilever portion 130 and the truncation portion 120. In addition, the diaphragm 140 may include eight protrusions 142 connected to the free ends F of the eight cantilever portions 130, but is not limited thereto, for example, the number of the protrusions 142 may be other multiples of eight.

FIG8 is a schematic top view of a MEMS structure 110, a substrate 101 and a diaphragm 140 of a MEMS device according to another embodiment of the present invention. As shown in FIG8 , in one embodiment, the MEMS structure 110 includes eight cantilever portions 130, which are separated from each other by truncation portions 120, each cantilever portion 130 has a fork shape, and two adjacent cantilever portions 130 are interlocked with each other, some truncation portions 120 intersect to form a cross shape, and the truncation portion 120 between two adjacent cantilever portions 130 with a fork shape has a square wave shape. Each cantilever portion 130 has an anchor end A located at the base of the fork shape, and two or three free ends F located at the ends of the finger-shaped fork. In addition, the eight cantilever portions 130 have twenty distances L1 to L20, wherein each distance is from the anchor end A to the free end F, and the twenty distances L1 to L20 may be the same or different. In addition, the eight cantilever portions 130 may be connected together through a portion of the MEMS structure 110 surrounding the eight cantilever portions 130, for example, the portion of the MEMS structure 110 has a connection portion connected to the anchor ends A of the eight cantilever portions. Therefore, the portions of the first electrode layer 121 located in the eight cantilever portions 130 are electrically connected together in series, and the portions of the second electrode layer 123 located in the eight cantilever portions 130 are also electrically connected together in series, and the portions of the third electrode layer 125 located in the eight cantilever portions 130 are also electrically connected together in series, so that the electrical signals generated in the eight cantilever portions 130 can be transmitted through the same contact pad.

Furthermore, as shown in FIG8 , in one embodiment, the substrate 101 has two sub-cavities 102S separated by a portion 101P of the substrate 101. When viewed from a top view, the edge of the diaphragm 140 extends outward beyond the edge of the two sub-cavities 102S. Furthermore, the edge of the opening 104 of the sacrificial layer 103 may also extend outward beyond the edge of the two sub-cavities 102S. The number and layout of the sub-cavities 102S may be adjusted according to the layout of the anchor ends A of the cantilever portions 130. In addition, the diaphragm 140 may have twenty protrusions 142 connected to the free ends F of the eight cantilever portions 130, but is not limited thereto, and the number of the protrusions 142 may be adjusted according to the number of the finger-shaped portions of the cantilever portions 130.

FIG9 and FIG10 are cross-sectional schematic diagrams of some stages of a method for manufacturing a MEMS device according to an embodiment of the present invention. Referring to FIG9 , first, a substrate 101 is provided, such as a silicon substrate. Then, a sacrificial layer 103, such as a silicon oxide layer, is deposited on the front surface 101F of the substrate 101. Next, a seed layer 111, a first electrode layer 121, a sensing material layer 113, a second electrode layer 123, another sensing material layer 115, a third electrode layer 125, and a passivation layer 117 are sequentially formed on the sacrificial layer 103 from bottom to top. The first electrode layer 121, the second electrode layer 123, and the third electrode layer 125 are each formed by a deposition process and a patterning process, and the seed layer 111, the sensing material layers 113 and 115, and the passivation layer 117 are each formed by a deposition process. In some embodiments, the material of the seed layer 111 and the passivation layer 117 is, for example, AlN, and the material of the sensing material layers 113 and 115 can be a piezoelectric material, such as AlN, Sc-doped AlN (ScAlN), ZnO or PZT. In addition, the material of the sensing material layers 113 and 115 can also be a piezoresistive material, such as doped Si or SiC. The material of the first electrode layer 121, the second electrode layer 123 and the third electrode layer 125 is, for example, Mo. In addition, a contact pad 127 is formed on the third electrode layer 125 and is electrically coupled to the first electrode layer 121 through a via. Another contact pad 129 is also formed on the third electrode layer 125 and is electrically coupled to the second electrode layer 123 through another via, and the material of the contact pads 127 and 129 is, for example, AlCu. In addition, the passivation layer 117 , the sensing material layers 113 and 115 , the electrode layers 121 , 123 and 125 , and the seed layer 111 are etched to form a cut-off portion 120 , thereby forming a cantilever portion 130 of the MEMS structure 110 .

Next, still referring to FIG. 9 , in step S101 , another sacrificial layer 105 , such as a silicon oxide layer, is formed by a deposition process to fill the truncation portion 120 , and the sacrificial layer 105 is also formed on the surface of the MEMS structure 110 to cover the contact pads 127 and 129 . Then, the sacrificial layer 105 is etched to form holes for the subsequent formation of the protrusion of the diaphragm. Afterwards, a material layer for forming the diaphragm is deposited on the sacrificial layer 105 , and the material layer fills the holes of the sacrificial layer 105 . Then, the material layer is patterned by photolithography and etching processes to form a diaphragm 140 including a protrusion 142 , and the material of the diaphragm 140 is, for example, silicon, polysilicon, aluminum or polyimide. In some embodiments, the material layer of the diaphragm 140 is used to fill other holes of the sacrificial layer 105 to form the anti-adhesion barrier 144 of the diaphragm 140 , and these other holes of the sacrificial layer 105 are shallower than the holes used to form the protrusion 142 .

Next, referring to FIG. 10 , in step S103 , a protective layer 107, such as a silicon oxide layer, is deposited to cover the diaphragm 140 and the MEMS structure 110 . Afterwards, a hard mask 109 having an opening is formed on the back side 101B of the substrate 101 , and the material of the hard mask 109 is, for example, silicon nitride or silicon oxide. Then, an etchant is applied through the opening of the hard mask 109 to etch the substrate 101 to form a cavity 102 , and then the hard mask 109 is removed. In one embodiment, the cavity 102 may penetrate the substrate 101 , extend from the back side 101B of the substrate 101 , and stop on the sacrificial layer 103 .

Then, still referring to FIG. 10 , in step S105 , the sacrificial layer 103 is etched to form an opening 104 , and then an etchant, such as vapor hydrofluoric acid (VHF), is applied through the cavity 102 and the opening 104 to remove the sacrificial layer 105 and the protective layer 107 to release the MEMS structure 110 and the diaphragm 140 , thereby completing the MEMS device 100 .

According to some embodiments of the present invention, a MEMS device includes a diaphragm vertically bonded to a MEMS structure, and the MEMS structure includes a plurality of cantilever portions, each cantilever portion includes an anchor end and a free end, a larger area can be provided through the diaphragm to sense environmental signals, and the diaphragm includes a plurality of protrusions connected to the free ends of the cantilever portions to increase the sensing area, thereby improving the sensitivity of the MEMS device. In addition, since the diaphragm is vertically integrated with the MEMS structure, its sensing area can be increased without increasing the size of the MEMS device.

In addition, according to some embodiments of the present invention, the output of electrical signals can be further increased by increasing the number of cantilever parts of the MEMS structure and reducing the size of the cantilever parts while maintaining the same sensing area, without expanding the size of the MEMS device. In addition, the MEMS structure of the MEMS device of the present invention can be applied to piezoelectric and piezoresistive sensors, so the MEMS device is suitable for pressure sensors, microphones, energy grabbers, accelerometers, etc.

The above descriptions are only preferred embodiments of the present invention. All equivalent changes and modifications made according to the claims of the present invention shall fall within the protection scope of the present invention.

Claims (18)

1. A micro-electromechanical device, comprising: a substrate having a cavity; A micro-electromechanical structure, comprising a first electrode layer, a second electrode layer, and a sensing material layer disposed between the first electrode layer and the second electrode layer, wherein the micro-electromechanical structure is disposed on the cavity and attached to the substrate, and the micro-electromechanical structure comprises a plurality of cantilever portions, and each of the cantilever portions comprises a free end and an anchor end; a diaphragm disposed on the micro-electromechanical structure, wherein the diaphragm includes a plurality of protrusions respectively connected to the free ends of the cantilever portions; and A gap is disposed between the micro-electromechanical structure and the diaphragm, wherein the gap surrounds the protrusions. 2 . The micro-electromechanical system device as claimed in claim 1 , wherein the cantilever portions are arranged in an array, and each of the cantilever portions comprises a triangle, a rectangle or an interdigitated shape. 3 . The micro-electromechanical system device as claimed in claim 1 , wherein the anchor end of each of the cantilever portions is attached to the substrate. 4 . The micro-electromechanical system device as claimed in claim 1 , wherein the cavity comprises a plurality of sub-cavities, and the sub-cavities are separated from each other by a portion of the substrate. 5 . The micro-electromechanical device of claim 4 , wherein the anchor end of one of the cantilever portions is attached to the portion of the substrate. 6 . The micro-electromechanical device as claimed in claim 4 , wherein the substrate comprises a first surface adjacent to the micro-electromechanical structure and a second surface opposite to the first surface, and the sub-cavities extend from the first surface to a height position in the substrate. 7 . The micro-electromechanical system device as claimed in claim 6 , wherein the cavity further comprises a common cavity extending from the second surface to the height position of the substrate and connected to the sub-cavities. 8. The micro-electromechanical device as claimed in claim 1, characterized in that the substrate includes a first surface adjacent to the micro-electromechanical structure and a second surface opposite to the first surface, the cavity extends from the first surface to a height position in the substrate, and the bottom surface of the cavity is located in the substrate. 9. The micro-electromechanical device as described in claim 8 is characterized in that it also includes a sacrificial layer arranged between the substrate and the micro-electromechanical structure, wherein the sacrificial layer has an opening connected to the cavity, and a portion of the sacrificial layer is arranged along the side wall of the cavity, and another portion of the sacrificial layer extends into the substrate. 10 . The micro-electromechanical system device as claimed in claim 1 , further comprising a sacrificial layer disposed between the substrate and the micro-electromechanical structure, wherein the sacrificial layer has an opening connected to the cavity. 11 . The micro-electromechanical system device as claimed in claim 1 , wherein each of the cantilever portions has a corresponding first electrode layer and a second electrode layer, and the first electrode layers and the second electrode layers are electrically connected in series. 12 . The micro-electromechanical system device as claimed in claim 11 , wherein the sensing material layer comprises a piezoelectric material or a piezoresistive material. 13 . The micro-electromechanical system device as claimed in claim 1 , wherein the membrane is made of a semiconductor material, a metal material or a polymer material. 14 . The micro-electromechanical system device as claimed in claim 1 , wherein the membrane further comprises an anti-adhesion barrier member protruding toward the micro-electromechanical system structure and spaced apart from the micro-electromechanical system structure. 15 . The micro-electromechanical system device according to claim 14 , wherein the anti-adhesion barrier component is disposed at an edge of the film. 16 . The micro-electromechanical device of claim 1 , wherein an edge of the membrane extends outwardly beyond an edge of the cavity when viewed from a top view. 17 . The micro-electromechanical system device of claim 1 , wherein the cantilever portions are separated from each other by a cutout portion penetrating the micro-electromechanical system structure. 18. The micro-electromechanical system device as claimed in claim 1, wherein the membrane further comprises a suspension portion vertically separated from the micro-electromechanical structure.