TWM487487U - Capacitive fingerprint sensor with electrostatic protection - Google Patents

Description

Capacitive fingerprint sensor with electrostatic protection

The present invention relates to a capacitive fingerprint sensor, and more particularly to a capacitive fingerprint sensor with electrostatic protection.

Fingerprints are the lines of protrusion on the epidermis of the skin, and each person has different fingerprints according to different genetic characteristics, so that the finger has been widely used in a biometric feature in personal identification. With the rapid development of the semiconductor industry, capacitive fingerprint sensors made of semiconductor wafers have been gradually applied to a wide variety of mobile electronic devices to reduce the risk of theft of the mobile electronic device. Since the capacitive sensing element in the capacitive fingerprint sensor has a surface that is exposed to a finger for detection, it must be exposed to an outside world in a large area, but any charged object may be electrostatically generated. The capacitive sensing element causes damage, thus making the antistatic structure in the capacitive fingerprint sensor more and more important. For example, in the Chinese Patent Publication No. CN102682271, an electrostatic damage protection structure of a capacitive fingerprint integrated circuit is disclosed, which comprises a plurality of sensing plates, forming a sensing plate array to define a sensing region; a first passivation a layer overlying the sensing plate; a patterned electrostatic damage protective metal layer deposited on the first passivation layer and having a fish-bone-like structure; a common conductive layer Connected to the fishbone structure and surrounding the sensing region and used to conduct electrostatic charge to the outside; an associated signal processing circuit is located below the sensing plate and electrically connected to the sensing plate And a second passivation layer disposed between the sensing board and the signal processing circuit. Accordingly, the sensing board and the signal processing circuit can be protected from electrostatic damage. However, in the above-mentioned electrostatic damage protection structure, the fishbone structure extends laterally so that the electric field concentration effect generated by the tip thereof has an improved space for guiding static electricity generated from the surface, and there is Improved demand.

The main purpose of the novel is to solve the conventional capacitive fingerprint sensor, and the electrostatic damage protection structure still has insufficient problems in guiding the static electricity. To achieve the above objective, the present invention provides a capacitive fingerprint sensor with electrostatic protection, comprising a sensing substrate, a plurality of capacitive sensing plates, a first dielectric layer, a second dielectric layer, and a third A dielectric layer and an electrostatic protection structure. The sensing substrate includes a substrate and a sensing circuit disposed on the substrate; the capacitive sensing plate is disposed on the sensing circuit and electrically connected to the sensing circuit; the first dielectric layer is disposed on the Between the capacitive sensing plate and the sensing circuit; the second dielectric layer is disposed on the first dielectric layer to cover the capacitive sensing plate; the third dielectric layer is disposed on the second dielectric layer And the electrostatic protection structure is disposed in the third dielectric layer, and includes a conductive grid and a plurality of conductive pillars disposed on the conductive grid, the conductive grid comprising a plurality of positions corresponding to the capacitive sensing a space area of the board and a plurality of interlaced grid lines, wherein the conductive pillar is disposed on the grid line, and includes a bottom section and a top section disposed on the bottom section, the top section having a top section smaller than the bottom section width. According to the present invention, the conductive grid and the conductive pillar are disposed by the electrostatic protection structure, so that the top section of the conductive pillar has a width smaller than the top section of the bottom section, so that the conductive pillar can face upward The generated static electricity is directly and quickly guided to improve the effect on an electric field concentration to increase the protection of the capacitive sensing board and the sensing circuit.

The detailed description and technical content of the present invention will now be described as follows: Please refer to the "Figure 1" to "Figure 3", and Figure 1 is a top plan view of an embodiment of the present invention. 』 is a schematic enlarged perspective view of a conductive column according to an embodiment of the present invention, and FIG. 3 is a partial cross-sectional view of FIG. 1 , as shown in the figure: the present invention is a capacitive fingerprint sensor with electrostatic protection, including a sensing The substrate 10 , the plurality of capacitive sensing boards 20 , a first dielectric layer 30 , a second dielectric layer 40 , a third dielectric layer 50 , and an electrostatic protection structure 60 . The sensing substrate 10 includes a substrate 11 and a sensing circuit 12 . The substrate 11 is generally a substrate, and the sensing circuit 12 is disposed on the substrate 11 . The capacitive sensing board 20 is disposed on the sensing circuit 12 and electrically connected to the sensing circuit 12 . The first dielectric layer 30 is disposed between the capacitive sensing board 20 and the sensing circuit 12 . It is made of a polyimine used in an intermetallic dielectric (IMD), and has a dielectric constant of about 2.8 to 3.2. In this embodiment, the capacitive sensing board 20 includes a connecting line 21 extending through the first dielectric layer 30. The capacitive sensing board 20 is electrically connected to the sensing circuit 12 through the connecting line 21. The second dielectric layer 40 is disposed on the first dielectric layer 30 to cover the capacitive sensing plate 20. The second dielectric layer 40 can be made of cerium oxynitride (SiON), and the dielectric constant thereof is Between 6.4 and 6.8, the thickness is about 15 μm to 20 μm. The third dielectric layer 50 is disposed on the second dielectric layer 40, and can also be made of polyimide. The thickness is about 3 μm to 4 μm. The third dielectric layer 50 has a sensing surface 51 that is contacted by a finger and away from the second dielectric layer 40. In addition, the first dielectric layer 30, the second dielectric layer 40, and the first The three dielectric layers 50 can also be various passivation layers. The electrostatic protection structure 60 is disposed in the third dielectric layer 50 and is made of metal. In this embodiment, the conductive structure 61 includes a conductive mesh 61, a conductive ring 63, and a plurality of conductive pillars 62. The conductive grid 61 includes a plurality of space areas 611 and a plurality of grid lines 612. The spaces area 611 are located above the capacitive sensing board 20, and the grid lines 612 are interlaced with each other. In the region 611, the conductive ring 63 surrounds a periphery of the conductive mesh 61, and is electrically connected to the conductive mesh 61 and grounded. The conductive pillars 62 are disposed on a staggered intersection 613 of the ruled line 612, and include a bottom section 621 and a top section 622. The bottom section 621 and the top section 622 are along the grid line 612. The direction forms a cross shape, but is not limited thereto. It may also be a circle, a square, a triangle, etc., and the bottom section 621 has a bottom section width W3 of 4 μm to 6 μm and a bottom section 621 of about 1 μm. The top section 622 is disposed on the bottom section 621 and has a top section width W2 that is smaller than the bottom section 621. The top section width W2 is greater than about 2 μm and less than 4 μm. The height of the top section 622 is about this. It is 1 μm. In this embodiment, the conductive post 62 can further include a tip 623 disposed on the top segment 622 having a tip width W1 that is less than the top segment width W2, about 1 μm. The height is about 1 μm. It should be noted that the value of the width W3 of the bottom section, the width W2 of the top section, and the width W1 of the tip are only examples, and are not limited thereto. The main spirit lies in the tip of the conductive pillar 62. The width W1 is smaller than the top section width W2, and the top section width W2 is smaller than the bottom section width W3, so that the conductive post 62 is pointed by the tip 623 toward the sensing surface 51. In this embodiment, when a finger or a charged object approaches the sensing surface 51, the bottom section 621 of the conductive post 62 and the top section 622 and the tip 623 are bottom-up. Gradually narrowing, the tip 623 is further directed to the sensing surface 51, so that an electric field concentration effect generated by the tip 623 is brought close to the sensing surface 51, so that the sensing surface 51 is below the third surface. The power line in the electrical layer 50 is attracted to the tip 623 such that the conductive post 62 has a greater electric field strength than the space region 611, increasing the probability that the electrostatic discharge from the sensing surface 51 will occur at the conductive post 62. The electrostatic discharge is generated, and the static electricity can be immediately guided from the tip 623 to the top segment 622, the bottom segment 621, and then guided to the conductive ring 63 via the conductive mesh 61, and finally derived from the ground. The effect of the capacitive sensing board 20 and the sensing circuit 12 is protected. Furthermore, in this embodiment, since the third dielectric layer 50 has a lower dielectric constant than the second dielectric layer 40, when electrostatic discharge occurs in the third dielectric layer 50, The probability of the static electricity flowing further to the second dielectric layer 40 is reduced, and the second dielectric layer 40 has a higher dielectric constant and the capacitance sensing can be improved in the case of normal fingerprint measurement. The capacitance value between the board 20 and the sensing surface 51 compensates for the capacitance value lost between the capacitive sensing board 20 and the sensing surface 51 due to the increase in distance, thereby improving the sensing capability. In summary, since the present invention is provided with the conductive mesh and the conductive post by the electrostatic protection structure, the conductive post is gradually narrowed from bottom to top, and the tip is directed to the sensing surface so that the tip can face upward. Directly and rapidly guiding the static electricity generated downwards to improve the effect on an electric field concentration to increase the protection of the capacitive sensing board and the sensing circuit. Furthermore, the present invention also provides the third dielectric layer. Having a lower dielectric constant than the second dielectric layer reduces the probability of static electricity flowing to the second dielectric layer to protect the capacitive sensing plate and the sensing circuit, and can also compensate for The capacitance value lost between the capacitive sensing board and the sensing surface is increased by the distance, and the sensing capability is improved. Therefore, the novel is highly progressive and meets the requirements for applying for a new patent, and the application is made according to law, and the praying office is an early one. Granting a patent, it is really sensible. The present invention has been described in detail above, but the above is only a preferred embodiment of the present invention, and the scope of the present invention is not limited. That is, the equal changes and modifications made in accordance with the scope of this new application shall remain within the scope of the patent of this new type.

10‧‧‧Sensing substrate
11‧‧‧Substrate
12‧‧‧Sensor circuit
20‧‧‧Capacitive sensing board
21‧‧‧Connecting line
30‧‧‧First dielectric layer
40‧‧‧Second dielectric layer
50‧‧‧ third dielectric layer
51‧‧‧Sense surface
60‧‧‧Electrostatic protection structure
61‧‧‧ Conductive grid
611‧‧‧Space area
612‧‧ ‧ grid
613‧‧‧Interlaced
62‧‧‧conductive column
621‧‧‧ bottom section
622‧‧‧ top section
623‧‧‧ tip
63‧‧‧ Conductive ring
W1‧‧‧ tip width
W2‧‧‧ top section width
W3‧‧‧ bottom width

FIG. 1 is a top plan view of an embodiment of the present invention. 2 is an enlarged perspective view of a conductive post according to an embodiment of the present invention. 3 is a partial cross-sectional view of FIG. 1.

611‧‧‧Space area

612‧‧ ‧ grid

613‧‧‧Interlaced

621‧‧‧ bottom section

622‧‧‧ top section

623‧‧‧ tip

W1‧‧‧ tip width

W2‧‧‧ top section width

W3‧‧‧ bottom width

Claims (12)

A capacitive fingerprint sensor with electrostatic protection, comprising: a sensing substrate, the sensing substrate comprises a substrate and a sensing circuit disposed on the substrate; a plurality of sensing circuits are disposed on the sensing circuit and a sensing circuit electrically connected to the sensing circuit; a first dielectric layer disposed between the capacitive sensing plate and the sensing circuit; a first dielectric layer disposed on the first dielectric layer to cover the capacitive a second dielectric layer of the test plate; a third dielectric layer disposed on the second dielectric layer; and an electrostatic protection structure disposed in the third dielectric layer, the electrostatic protection structure including a conductive a grid and a plurality of conductive pillars disposed on the conductive grid, the conductive grid comprising a plurality of spaces corresponding to the space of the capacitive sensing board and a plurality of grid lines interlaced around the space area, the conductive pillar Disposed on the grid line, comprising a bottom section and a top section disposed on the bottom section, the top section having a width greater than a top section of the bottom section. The electrostatic fingerprint-protected capacitive fingerprint sensor of claim 1, wherein the conductive pillars are disposed on a staggered intersection of the grid lines. The electrostatic fingerprint protection capacitive fingerprint sensor of claim 1, wherein the electrostatic protection structure further comprises a conductive ring surrounding the conductive mesh and electrically connected to the conductive mesh. The electrostatic fingerprint-protected capacitive fingerprint sensor of claim 1, wherein the conductive post further comprises a tip on the top segment, the tip having a tip width that is less than the width of the top segment. The electrostatic fingerprint-protected capacitive fingerprint sensor of claim 4, wherein the tip has a width of 1 μm. The capacitive fingerprint sensor with static electricity protection according to claim 1, wherein the top section has a width greater than 2 μm and less than 4 μm. The electrostatic fingerprint-protected capacitive fingerprint sensor of claim 1, wherein the bottom section has a bottom section width greater than 4 μm and less than 6 μm. The electrostatic fingerprint-protective capacitive fingerprint sensor of claim 1, wherein the second dielectric layer has a dielectric constant greater than the first dielectric layer. The electrostatic fingerprint-protected capacitive fingerprint sensor of claim 1, wherein the third dielectric layer has a dielectric constant smaller than the second dielectric layer. The capacitive fingerprint sensor with electrostatic protection according to claim 1, wherein the capacitive sensing plate comprises a connecting line electrically connected to the sensing circuit through the first dielectric layer. The electrostatic fingerprint-protective capacitive fingerprint sensor of claim 1, wherein the third dielectric layer has a thickness of between 3 μm and 4 μm. The electrostatic fingerprint-protected capacitive fingerprint sensor of claim 1, wherein the second dielectric layer has a thickness of between 15 μm and 20 μm.