This application claims the priority benefit of Taiwan application serial no. 105104409, filed on Feb. 16, 2016. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.
Field of the Invention
The invention relates to a micro-electro-mechanical system (MEMS) sensor and a sensing apparatus and more particularly to an MEMS force sensor and a force sensing apparatus.
Description of Related Art
A micro-electro-mechanical system (MEMS) technique refers to a design based on a miniaturized electro-mechanical integrated structure. At present, the common MEMS techniques are mainly applied in three major fields, i.e., micro sensor, micro actuator and micro structure elements. Among them, the micro sensor can be used to convert an external environmental changes (e.g., forces, pressures, sounds, speeds, etc.) into electrical signals (e.g., voltages or currents), thereby achieving environmental sensing functions, such as force sensing, pressure sensing, sound sensing, acceleration sensing and so on. The micro sensor may be fabricated by using a semiconductor fabrication process and integrated with an integrated circuit, thus has preferable competitiveness. Accordingly, an MEMS sensor and a sensing apparatus applying the MEMS sensor in fact become the development trend of MEMS systems.
The invention provides a micro-electro-mechanical system (MEMS) force sensor capable of sensing a change of a force applied to the MEMS force sensor.
The invention provides a force sensing apparatus capable of sensing a change of a force applied to the force sensing apparatus.
According to an embodiment of the invention, an MEMS force sensor including a first substrate, a second substrate and a plurality of conductive terminals is provided. The second substrate is disposed opposite to the first substrate and includes a deformable portion and a force receiving portion. The deformable portion has a plurality of sensing elements. The force receiving portion protrudes from a surface of the deformable portion which is back facing to the first substrate, such that a cavity is formed above the deformable portion. The conductive terminals are electrically connected to the sensing elements, and the conductive terminals are centrally disposed under the cavity. The second substrate is fixed with the first substrate through the conductive terminals.
In an embodiment of the invention, the first substrate is a printed circuit board (PCB) or a display panel.
In an embodiment of the invention, the sensing elements include a plurality of connection portions and a plurality of piezoresistive sensing elements. Each of the piezoresistive sensing elements is connected with two adjacent connection portions. Each of four sides of the deformable portion has a sensing unit. The sensing unit is composed of at least one of the piezoresistive sensing elements and multiple of the connection portions.
In an embodiment of the invention, orthographic projections of the piezoresistive sensing elements on the surface of the deformable portion which is back facing to the first substrate fall within a range covered by the cavity.
In an embodiment of the invention, the sensing elements are disposed near a central region of the deformable portion, and orthographic projections of the sensing elements and the piezoresistive sensing elements on the surface of the deformable portion which is back facing to the first substrate fall within the range covered by the cavity.
In an embodiment of the invention, the second substrate further includes a circuit structure. The circuit structure is disposed on a surface of the deformable portion facing the first substrate, and the sensing elements are electrically connected to the conductive terminals through the circuit structure. Therein, two adjacent sensing units share one of the conductive terminals through the circuit structure and form a Wheatstone bridge.
In an embodiment of the invention, the MEMS force sensor further includes an overload protection layer. The overload protection layer is filled in the cavity, and a top surface of the overload protection layer is higher than a top surface of the force receiving portion.
In an embodiment of the invention, a rigidity of the overload protection layer is less than a rigidity of the second substrate.
In an embodiment of the invention, the MEMS force sensor further includes an overload protection layer. The overload protection layer is disposed on a surface of the deformable portion facing the first substrate and exposes the conductive terminals. A gap is kept between the overload protection layer and the first substrate.
According to an embodiment of the invention, a force sensing apparatus including an MEMS force sensor and a third substrate is provided. The MEMS force sensor includes a first substrate, a second substrate and a plurality of conductive terminals. The second substrate is disposed opposite to the first substrate and includes a deformable portion and a force receiving portion. The deformable portion has a plurality of sensing elements. The force receiving portion protrudes from a surface of the deformable portion which is back facing to the first substrate, such that a cavity is formed above the deformable portion. The conductive terminals are electrically connected to the sensing elements, and the conductive terminals are centrally disposed under the cavity. The second substrate is fixed with the first substrate through the conductive terminals. The third substrate has a protruding portion, a width of the protruding portion is less than a width of the cavity, and a thickness of the protruding portion is less than a depth of the cavity. The third substrate is assembled onto the second substrate, and the protruding portion is embedded in the cavity.
In an embodiment of the invention, the third substrate is a substrate of a touch panel or a substrate of a display panel.
To sum up, in the embodiments of the invention, the deformable portion has a plurality of sensing elements, and the force receiving portion protrudes from the surface of the deformable portion which is back facing to the first substrate. When an external force is applied to the force receiving portion, the deformable portion receives a pressing-down force and is deformed, and the sensing elements in the deformable portion correspondingly generate a physical quantity change, such that the MEMS force sensor and the force sensing apparatus having the MEMS force sensor can determine the change of the force applied to the MEMS force sensor or the force sensing apparatus according to the physical quantity change.
To make the above features and advantages of the invention more comprehensible, embodiments accompanied with drawings are described in detail below.
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a portion of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
The first substrate 110 may be a printed circuit board (PCB), a display panel or any other suitable substrate, and the first substrate 110 has a circuit suitable for exporting electrical signals to a processor. The second substrate 120 may be a semiconductor substrate, and the deformable portion 122 and the force receiving portion 124 may be formed through a patterning process. The force receiving portion 124 is disposed around the edge of the deformable portion 122, such that the cavity C is located in the center of the second substrate 120. The aforementioned semiconductor substrate is, for example, a silicon-on-insulator (SOI) substrate, but the invention is not limited thereto. The conductive terminals 130 are located between the first substrate 110 and the second substrate 120, and the conductive terminals 130 may export the electrical signals and serve as mechanical fixing terminals. In the present embodiment, the conductive terminals 130 are solder balls having advantages, such as good conductivity, no need to package and small volume.
The sensing elements SS are disposed near a surface of the deformable portion 122 facing the first substrate 110 and are disposed near the edge of the deformable portion 122, which is not limited in the invention. In another embodiment, the sensing elements SS may also be disposed near a central region of the deformable portion 122. The second substrate 120 may further include a circuit structure (not shown) for electrically connecting the sensing elements SS with the conductive terminals 130. In this way, when an external force is applied to the force receiving portion 124, the deformable portion 122 is deformed by a pressing-down force received by the force receiving portion 124, such that the sensing elements SS in the deformable portion 122 correspondingly generate a physical quantity change. The aforementioned physical quantity change correspondingly causes a change in an electrical signal, and the change in the electrical signal may be output through the circuit structure and the conductive terminals 130 in sequence to an external circuit (e.g., the processor) for subsequent signal processing and analysis. In this way, the MEMS force sensor 100 may determine the change of the force applied thereto.
Several specific implementation forms of the MEMS force sensor 100 will be described with reference to
Referring to
Each of four sides of the deformable portion 122 has a sensing unit U. Each sensing unit U is composed of at least one of the piezoresistive sensing elements SS2 and multiple of the connection portions SS1. For example, each sensing unit U is composed of two piezoresistive sensing elements SS2 and three connection portions SS1, but the invention is not limited thereto.
Referring to
In the present embodiment, the circuit structure CS includes a first inter-layer dielectric layer 140, a plurality of conductive wires 150, a second inter-layer dielectric layer 160 and a plurality of pads 170. The first inter-layer dielectric layer 140 is disposed on the surface S of the deformable portion 122 facing the first substrate 110. The first inter-layer dielectric layer 140 has a plurality of first openings O1. Each of the first openings O1 exposes a portion of one of the connection portions SS1. The conductive wires 150 are disposed on the first inter-layer dielectric layer 140. The portion of each of the connection portions SS1 is connected with one of the conductive wires 150. The second inter-layer dielectric layer 160 is disposed on the first inter-layer dielectric layer 140 and the conductive wires 150, and the second inter-layer dielectric layer 160 has a plurality of second openings O2. Each of the second openings O2 exposes a portion of one of the conductive wires 150. The pads 170 are disposed on the second inter-layer dielectric layer 160. Each of the pads 170 is connected with the portion of a corresponding conductive wire 150 through one of the second openings O2. Each of the conductive terminals 130 is connected to one of the pads 170 to export an electrical signal from the second substrate 120.
A fabrication process of the MEMS force sensor 100A will be described as follow. Referring to
Then, an insulating layer IN is formed on the substrate SB. The insulating layer IN, for example, covers all surfaces of the substrate SB, but the invention is not limited thereto. The insulating layer IN is, for example, a silicon oxide layer, but the invention is not limited thereto.
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Based on different demands, a person ordinarily skilled in the art may change the sequence of the fabrication process or additionally dispose other elements or layers, or change shapes of the elements or relative disposition relations, without departing the spirit or scope of the invention. For example, referring to
Besides, referring to
In addition, in an MEMS force sensor 100D illustrated in
Since the overload protection layer 180A is disposed on the deformable portion 122, the rigidity of the overload protection layer 180A may influence a deformation degree of the deformable portion 122. Namely, the rigidity of the overload protection layer 180A may influence sensing sensitivity. In the present embodiment, the sensing sensitivity may be fine-tuned through changing a material of the overload protection layer 180A. For example, the material of the overload protection layer 180A may include a polymer, but the invention is not limited thereto.
Additionally, a size of the gap G determines a maximum pressing-down distance of the MEMS force sensor 100C. Therefore, in the present embodiment, the size of the gap G may be modulated (for example, by keeping the gap G smaller than a maximum deformation of the deformable portion 122) to prevent the deformable portion 122 from being damaged due to the pressing-down distance being greater than the maximum deformation of the deformable portion 122.
The third substrate 14 has a protruding portion PT. A width WPT of the protruding portion PT is less than a width WC of the cavity C, and a thickness H of the protruding portion PT is less than a depth D of the cavity C. Thereby, when the third substrate 14 is assembled onto the second substrate 120, the protruding portion PT may be embedded in the cavity C, which facilitates improving the convenience of alignment.
Additionally, in the present embodiment, the size of a gap G′ between the protruding portion PT and the deformable portion 122 may be modulated to modulate a pressure range of the the deformable portion 122. For example, the gap G′ may be less than the maximum deformation of the deformable portion 122 to prevent the deformable portion 122 from being damaged due to the pressing-down distance being greater than the maximum deformation of the deformable portion 122. In other words, the protruding portion PT facilitates not only improving the convenience of alignment, but also achieving an overload protection effect.
Based on different demands, other film layers may be disposed on the third substrate 14. For example, a touch element may be disposed on the third substrate 14, i.e., the third substrate 14 may be a substrate of a touch panel. In this way, the force sensing apparatus 10 may further provide a two-dimensional sensing function in addition to the force sensing function. Namely, the force sensing apparatus 10 is capable of not only detecting a force change in a Z-axial direction, but also detecting a touched coordinate on the X-Y plane. However, the invention is not limited thereto. In another embodiment, the third substrate 14 may also be a substrate of a display panel.
To summarize, in the exemplary embodiments of the invention, the deformable portion has a plurality of sensing elements, and the force receiving portion protrudes from the surface of the deformable portion which is back facing to the first substrate. When an external force is applied to the force receiving portion, the deformable portion receives a pressing-down force and is deformed, and the sensing elements in the deformable portion correspondingly generate a physical quantity change, such that the MEMS force sensor and the force sensing apparatus having the MEMS force sensor can determine the change of the force applied to the MEMS force sensor or the force sensing apparatus according to the physical quantity change. In other embodiments, the MEMS force sensor can further be equipped with the overload protection layer to provide the stress buffering or overload protection effect. Moreover, the third substrate of the force sensing apparatus which is designed with the protruding portion can facilitate not only improving the convenience of alignment but also achieving the overload protection effect.
Although the invention has been disclosed by the above embodiments, they are not intended to limit the invention. It will be apparent to one of ordinary skill in the art that modifications and variations to the invention may be made without departing from the spirit and scope of the invention. Therefore, the scope of the invention will be defined by the appended claims.
Number | Date | Country | Kind |
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105104409 | Feb 2016 | TW | national |