JP2002216117A - Fingerprint detector in capacitance detection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fingerprint detector in a capacitance detection system by which output of an electric charge from a detection electrode of the whole line and a detection electrode from the whole column is not inhibited and with high reliability in fingerprint detection. SOLUTION: A part with cross sectional area smaller than that in superposed areas with control wiring 22 and input/output wiring 23 among wiring 24 for lightning rod is provided on the non-superposed areas other than the superposed areas. Thus, current to exceed allowable quantity flows to the wiring 24 for lighting rod, the part with small cross sectional area on the non-superposed area is first bused among the wiring 24 for lighting rod. Consequently, no fusion is caused on the superposed area with the control wiring 22 and on the superposed area with the input/output wiring 23 among the wiring 24 for lighting rod and the control wiring 22 and the input/output wiring 23 arranged on the superposed areas are not destructed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitance detection type fingerprint detection device for detecting capacitance between a finger and a plurality of detection electrodes.

[0002]

2. Description of the Related Art FIG. 2 shows a fingerprint detecting apparatus and a method of using the same. A fingerprint is detected by placing a finger 12 on a fingerprint detecting apparatus 11 as shown in FIG. FIG. 3 is a partially enlarged view of FIG. 2 and illustrates the principle of fingerprint detection. Insulating film 1 on semiconductor substrate (not shown)
A plurality of detection electrodes 14 are arranged in a matrix on 3, and the detection electrodes 14 are covered with a protective film 15. When the finger 12 is placed on the protective film 15, a capacitance element 16 corresponding to the unevenness of the fingerprint is formed between the surface of the finger 12 and the detection electrode 14.

Since the distance between the convex portion of the fingerprint and the detecting electrode 14 is smaller than the distance between the concave portion of the fingerprint and the detecting electrode 14, the capacitance of the capacitor 16a corresponding to the convex portion of the fingerprint corresponds to the concave portion of the fingerprint. Larger than the capacitance of the capacitive element 16b. Therefore, the fingerprint is detected by detecting the capacitance of each detection electrode 14. In order to detect the capacitance of the detection electrode 14, a plurality of switching transistors 21 connected to the respective detection electrodes 14 are provided on the semiconductor substrate as shown in FIG. The control wiring 22 and the input / output wiring 23 are connected to the transistor 21.

When the finger 12 is placed on the protective film 15, all the transistors 21 are turned on by the control wiring 22. When electric charges corresponding to the capacitances of the respective capacitance elements 16 are accumulated in the detection electrodes 14 via the input / output wirings 23, all the transistors 2 are controlled by the control wirings 22.
1 is turned off. Then, the control wiring 22 of each row
Operate sequentially, and the respective detection electrodes 14 in the row are operated.
Is read out via the input / output wiring 23, the capacitance of each detection electrode 14 is detected.

By the way, as shown in FIGS.
When detecting a fingerprint, the finger 12 is placed on the surface of the fingerprint detecting device 11.
And the finger 12 may be charged with static electricity, so that the protective film 15 is required to have dielectric breakdown resistance. In order to increase the dielectric breakdown resistance of the protective film 15, the electric field in the protective film 15 may be weakened by increasing the thickness of the protective film 15.
When the thickness is increased, the capacitance of the capacitive element 16 decreases,
Fingerprint detection sensitivity decreases.

Therefore, in order to remove the static electricity and keep the potential of the finger 12 constant, lightning rod wires 24 are arranged in a grid pattern around the detection electrode 14 as shown in FIGS. There is known a conventional example (US Pat. No. 5,325,442).
No.). In such a conventional example, if the potential of the lightning rod wire 24 is fixed to, for example, a ground potential different from the detection electrode 14 and the transistor 21, the electrostatically charged finger 12 contacts the surface of the fingerprint detection device 11. Even if this is done, the static electricity of the finger 12 is removed via the lightning rod wiring 24, so that the protective film 15 is protected from destruction.

[0007]

However, when the charge amount of the finger 12 is large and the current exceeding the allowable amount is applied to the lightning rod wiring 24,
, The lightning rod wiring 24 is blown. Then, when the lightning rod wiring 24 is blown, not only the blown portion of the lightning rod wiring 24 but also the adjacent area is destroyed. On the other hand, as shown in FIG. 5, in the above-described conventional lightning rod wiring 24 in the conventional example, its width is uniform and its cross-sectional area is also uniform.
As a result, the electrical resistance of any part of the lightning rod wiring 24 is uniform. For this reason, the portion that causes fusing when a current exceeding the allowable amount flows through the lightning rod wire 24 is not limited, and it is not possible to predict which portion of the lightning rod wire 24 will cause fusing.

If fusing occurs in the overlapping area with the control wiring 22 and the overlapping area with the input / output wiring 23 in the lightning rod wiring 24, the control wiring 22 and the input / output wiring arranged in these overlapping areas are provided. 23 may also be destroyed. When the control wiring 22 is destroyed, the reading of charges from the detection electrodes 14 in the entire row connected to the control wiring 22 is hindered, and when the input / output wiring 23 is broken, the connection to the input / output wiring 23 is made. The readout of the electric charges from the detection electrodes 14 in the entire column is disturbed. Therefore, the reliability of fingerprint detection is not always high in the lightning rod wiring 24 in the above-described conventional example.

Therefore, the invention of the present application provides a capacitance detection type fingerprint detection device which has high reliability in fingerprint detection without obstructing reading of charges from the detection electrodes of the entire row or the entire column. It is intended to be.

[0010]

In the capacitance detection type fingerprint detecting device according to the present invention, a lightning rod for a lightning rod is provided in a non-overlapping area other than an overlapping area with a control wiring and an overlapping area with an input / output wiring. , A portion having a smaller cross-sectional area than the cross-sectional area in the overlapping region is provided. For this reason, when a current exceeding the allowable amount flows through the lightning rod, the part of the lightning rod that has a small cross-sectional area in the non-overlapping region, that is, the part with high electrical resistance, is blown first. The current no longer flows in the portion adjacent to. Therefore, the portion of the lightning rod wiring that causes fusing is limited to a portion having a small cross-sectional area in a non-overlapping region with the control wiring and the input / output wiring.

When the lightning rod wiring is blown, not only the blown portion of the lightning rod wiring but also the adjacent area is destroyed. However, since the portion of the lightning rod wiring that causes fusing is limited to a small cross-sectional area in a non-overlapping region with the control wiring and the input / output wiring, even if a current exceeding the allowable amount flows through the lightning rod wiring, Among the lightning rod wires, a fusing does not occur in an overlapping area with the control wiring and an overlapping area with the input / output wiring, and the control wiring and the input / output wiring arranged in these overlapping areas are not broken.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG. As shown in FIG. 1, in the fingerprint detecting device 11 of the present embodiment, the thickness of the lightning rod wire 24 is uniform, but the width is not uniform. That is,
Among the lightning rod wires 24, in the overlapping region with the control wiring 22 and the overlapping region with the input / output wiring 23 and the region near them, the width of the lightning rod 24 is relatively large and the cross-sectional area is relatively large. In a region separated from the above-mentioned overlapping region, the width of the lightning rod wire 24 is relatively narrow and the cross-sectional area is relatively small. Except for these points, the fingerprint detection device 11 of the present embodiment has substantially the same configuration as the fingerprint detection device 11 of the conventional example shown in FIG.

In the fingerprint detecting device 11 of the present embodiment, a portion having a relatively small cross-sectional area is provided in the lightning rod wiring 24, and a portion having a relatively small cross-sectional area has a relatively high electric resistance. For this reason, even if the current flows uniformly through the lightning rod wiring 24, the heat generation amount is relatively large in a portion having a relatively small cross-sectional area. As a result, when the charge amount of the finger 12 is large and a current exceeding the allowable amount flows to the lightning rod wiring 24, a portion of the lightning rod wiring 24 having a relatively small cross-sectional area is blown first, and the fusing occurs once. Then, current no longer flows in the portion adjacent to the fusing portion.

Therefore, the portion of the lightning rod wire 24 that causes fusing is limited to a region that is separated from the overlapping region with the control wiring 22 and the overlapping region with the input / output wiring 23. For this reason, the control wiring 22 out of the lightning rod wiring 24
Fusing does not occur in the superimposed region of the control wiring 22 and the input / output wiring 23 and the input / output wiring 23 is not destroyed. As a result,
Reading of charges from the detection electrodes 14 in the entire row connected to the control wiring 22 and reading of charges from the detection electrodes 14 in the entire column connected to the input / output wiring 23 are not hindered. The fingerprint detection device 11 has high reliability in fingerprint detection.

In the fingerprint detecting device 11 of the present embodiment described above, the cross-sectional area of this part is reduced by partially reducing the width of the lightning rod wiring 24. However, a step is provided under the lightning rod wiring 24, and the cross-sectional area may be reduced by reducing the thickness of the lightning rod wiring 24 at this step. In order to provide a step on the base of the lightning rod wiring 24, for example, FIG.
As is clear from FIG. 7, the interval between the detection electrodes 14 may be partially widened, and a step portion is provided in the protective film 15 in this portion. Further, a step may be provided below the insulating film 13.

In order to partially narrow the width of the lightning rod wire 24 or partially widen the interval between the detection electrodes 14, the lightning rod wire 24 and the detection electrode 14 are patterned by etching or the like. It is only necessary to change the pattern of the mask when performing. Therefore, neither the manufacturing process nor the manufacturing cost for the fingerprint detection device 11 of the present embodiment is increased as compared with the fingerprint detection device 11 of the related art shown in FIG.

[0017]

In the capacitance detection type fingerprint detection device according to the present invention, the control wiring and the input / output wiring are not destroyed even if a current exceeding the allowable amount flows through the lightning rod wiring. For this reason, the reading of charges from the detection electrodes in the entire row and the columns is not hindered, and the reliability of fingerprint detection is high.

[Brief description of the drawings]

FIG. 1 is a plan view of an embodiment of the present invention.

FIG. 2 is a side view showing a fingerprint detection device and a method of using the same.

FIG. 3 is a partial enlarged view of FIG. 2, showing the principle of fingerprint detection.

FIG. 4 is a side cross-sectional view for explaining lightning rod wiring in the fingerprint detection device.

FIG. 5 is a plan view of a conventional example of the present invention.

[Explanation of symbols]

11 fingerprint detection device, 14 detection electrode, 21 transistor (switch), 22 control wiring, 23 input / output wiring, 24 wiring for lightning rod

Claims (3)

[Claims] A plurality of detection electrodes and a plurality of switches respectively connected to the plurality of detection electrodes are arranged in a matrix, and a control line for controlling opening and closing of the switches and a detection electrode are provided. An input / output wiring for inputting / outputting electric charges is connected to the switch, and a lightning rod wiring is arranged in a lattice shape corresponding to the matrix, and is connected to the detection electrode via the switch and the input / output wiring. In the capacitance detection type fingerprint detection device that detects the capacitance of the detection electrode based on the charge that is read, a first overlapping area with the control wiring and a second one with the input / output wiring among the lightning rod wires An electrostatic capacitance detection type fingerprint detection device, wherein a portion having a smaller cross-sectional area than the first and second superposed regions is provided in a non-superposed region other than the two superposed regions. 2. The electrostatic capacitance detection type fingerprint detection device according to claim 1, wherein the cross-sectional area is reduced by reducing the width of the lightning rod wire in the non-overlapping area. 3. A light-emitting device according to claim 1, wherein a step is provided under the lightning rod in the non-overlapping region, and the cross-sectional area is reduced by reducing the thickness of the lightning rod at the step. Item 2. An electrostatic capacitance detection type fingerprint detection device according to item 1.