KR20010035260A - Thin film transistor type fingerprint acquisition device whose light sensing part has light shield layer thereon - Google Patents

Abstract

PURPOSE: A thin film transistor fingerprint recognition system having an optical shield layer formed in an optical sensor is provided to reduce a range of a ray projected to an optical sensor by forming an optical shield layer in a peripheral area except a ray incidence layer on a surface of the optical sensor. CONSTITUTION: A ray shielding layer(17) is formed on a surface of an insulation layer over a drain(12-D) and a source(12-S) of an optical sensor(12). The ray shielding layer(17) of the optical sensor(12) can be formed by a non-permeability insulation film. A passivation(18) can be formed in an upper part of the ray shielding layer(17). If the passivation is formed in the upper part of the ray shielding layer(17), an edge is thicker. Therefore, a substantial incident area is reduced.

Description

Thin film transistor type fingerprint acquisition device whose light sensing layer has light shield layer thereon}

The present invention relates to a TFT type fingerprint input device, and more particularly, to a TFT fingerprint input device having a structure in which a light shielding layer is formed on a surface of the light sensing unit except for the light incidence layer to reduce an incident range of light reflected from the fingerprint. will be.

As a technique for granting a user's access authority of a computer, a fingerprint recognition system that recognizes a fingerprint of a user registered in advance and grants an access right is used. The fingerprint recognition device is an apparatus for access authentication by analyzing a reflected fingerprint image by shining light on a fingerprint and comparing the fingerprint image with a fingerprint stored in a database. Fingerprint readers are installed in a large computer, as well as a small portable computer, a wireless keyboard, a mouse body.

The fingerprint recognition apparatus is largely divided into a method using a lens or a prism, and a planar thin film transistor (TFT) fingerprint input device as a lensless method. The TFT fingerprint input device is a kind of contact image sensor that uses a-Si: H photosensitivity, and has a relatively thin structure to obtain high photosensitivity.

The structure and working principle of the TFT fingerprint input device will be described with reference to Figs. 1A and 1B. FIG. 1A is a longitudinal cross-sectional view of a unit cell of a TFT fingerprint input device, and FIG. 1B shows an equivalent circuit in which four unit cells, such as the fingerprint input device of FIG. 1A, are arranged.

In FIG. 1A, in the TFT fingerprint inputter 10, the light sensing unit 12 and the switching unit 13 are horizontally arranged on the transparent substrate 11, and a back light is directed upward below the transparent substrate 11. It emits light and passes through the fingerprint input device 10. The source electrode 12 -S of the light sensing unit 12 and the drain electrode 13 -D of the switching unit 13 are electrically connected through the first electrode 14, and the gate of the light sensing unit 12 is connected. The second electrode 15 is connected to the electrode 12 -G.

In the above configuration, a photosensitive layer 12-P such as amorphous silicon (a-Si: H) is formed between the drain electrode 12-D and the source electrode 12-S of the light sensing unit 12. Therefore, when light having a predetermined amount of light or more is incident on the photosensitive layer 12 -P, the drain electrode 12-D and the source electrode 12-S are electrically conductive. As a result, when the user attempts to access the computer with the fingerprint inputter 10, the light L generated from the backlight under the transparent substrate 11 is reflected according to the fingerprint pattern, thereby causing the photosensitive layer 12 of the light sensing unit 12 to be exposed. By receiving light at -P), the light sensing unit 12 is turned on.

On the other hand, the switching unit 13 is switched every frame set to scan the fingerprint by the gate control signal applied to the gate terminal (13-G), each of the light sensing arranged in the fingerprint image input to the fingerprint input unit 10 It forms so that it may form as a frame scanned for every 12. Accordingly, the light blocking layer 13-sh is covered with the drain electrode 13-D and the source electrode 12-S so that external light does not enter the switching unit 13.

However, in the conventional TFT fingerprint input device, there is a problem as shown in FIG. 1C. The effective sensing area of the photosensitive layer 12 -P of the photosensitive unit 12 is the area of the photosensitive layer 12 -P exposed between the drain 12 -D and the source 12 -S (hereinafter referred to as "light incidence"). Layer ″), the area of the fingerprint reflection light (actually incident area) that is actually incident on the light incident layer becomes much wider than this. That is, since light reflected from an object (fingerprint) is scattered and reaches the photosensitive layer 12 -P, it can be incident at a very wide angle. In particular, in the structure where a plurality of light sensing units are arranged as shown in FIG. 1D, when a fingerprint is input in an actual incident region overlapping between adjacent light sensing units 12a and 12b, the resolution of the fingerprint pattern is reduced. Unlike the optical method using a lens and a prism, it is not easy to reduce the real incident area by a lens or a prism in the lensless TFT method, which is a planar fingerprint reader.

Accordingly, an object of the present invention is to provide a TFT fingerprint input device having a structure in which a light shielding layer is formed on the surface of the light sensing part of the TFT fingerprint input device in a peripheral area except the light incidence layer to reduce the range of light incident on the light sensing part. .

1A is a cross-sectional view of a conventional TFT fingerprint input device.

Fig. 1B is an equivalent circuit of the TFT fingerprint input device shown in Fig. 1A.

1C is a structure diagram of a light detecting unit of a conventional TFT fingerprint input device.

1D is a schematic diagram showing a problem of a conventional TFT fingerprint input device.

2A is a structural diagram of a TFT fingerprint input device according to the present invention;

Figure 2b is a schematic diagram showing that the problem is solved according to the present invention.

<Explanation of drawing code>

TFT fingerprint input device 10, transparent substrate 11, light sensing unit 12, source electrode 12-S, gate electrode 12-G, drain electrode 12-D, photosensitive layer 12-P ), Switching unit 13, drain electrode 13-D, source electrode 12-S, light shielding layer 13-sh, first electrode 14, second electrode 15, light shielding layer (17), Shield (18)

TFT fingerprint input device according to the present invention,

In the known TFT fingerprint input device which consists of a light-sensing part which consists of a light incident layer, the drain and the source electrode formed in the light incident layer surface, and the switching part in which the light shielding layer is formed in the drain and the source electrode in the surface,

The light sensing unit includes a light incidence layer through which light incident from the fingerprint is incident, a drain electrode and a source electrode connected to both ends of the light incidence layer, an insulating layer formed on a surface of the drain electrode and the source electrode, and on the insulating layer Is formed but has a structure consisting of a light shielding layer formed to expose the light incident layer.

With this structure, the angle of incidence of the light incident on the light incident layer is limited by the edge of the light shielding layer, so that the angle of incidence of the light incident on the light incident layer can be reduced and the physical strength of the structure can be increased. .

In addition, if a passivation film such as nitride film (Si ₃ N ₄ ) or PSG is formed on the surface of the light shielding layer, the incident angle range of incident light may be further reduced, and the physical strength of the light sensing unit may be further improved.

Example

2A is a structural diagram of a TFT fingerprint input device according to the present invention. Although generally having a structure similar to that of a conventional TFT fingerprint input device (see FIG. 1A), the light shielding layer 17 is formed on the surface of the insulating layer on the drain 12-D and the source 12-S of the light sensing unit 12. Formed. This is formed in the same process as the light shielding layer 13 -sh of the switching unit 13.

However, the operation is completely different. The light shielding layer 13-sh of the switching unit 13 is for shielding external light completely so that only the switching operation can be performed, but the light shielding layer 17 of the light sensing unit 12 is provided to the light incident layer. In order to reduce the incident range of the incident reflected light as much as possible to reduce the actual incident region as described in Figure 1c.

The light blocking layer 17 of the light sensing unit 12 may be formed by an opaque insulating film. For example, it can be formed from an oxide film, a nitride film, an insulating polysilicon film, or the like. In addition, the manufacturing process of the light shielding layer 17 is similar to the process of the light shielding layer of the switching unit 13. However, since the light incident layer must be exposed, a photomask process and an etching process will be added. For example, after depositing the light shielding layer so as to cover the entire insulating layer on the surface of the drain 12-D and the source 12-S of the light sensing unit 12, the region except the light incident layer is applied to the lithography method. Can be coated with a photoresist and the light incident layer can be exposed by etching.

Meanwhile, a passivation layer 18 may be formed on the light shielding layer 17 again. The protective film refers to a nitride film or glass (PSG) layer formed on the final outer layer before forming and packaging an integrated circuit. A protective film is formed mainly for the purpose of increasing physical strength, improving resistance to external moisture or temperature, and improving insulation.

In the present invention, if the protective film 18 is formed on the light shielding layer 17, the edge where the incident light is scattered becomes thicker, and thus the actual incident area can be further reduced, and the physical strength of the fingerprint input device itself can be reduced. It can be further increased than when. The manufacturing process of the protective film 18 is also made similarly to the light shielding layer 17.

According to the present invention, since the actual incident area where the fingerprint reflection light is incident on the light incident layer of the TFT fingerprint input device can be reduced, only light close to the effective sensing area of the light incident layer can be detected. Therefore, in the actual fingerprint input device using the light sensing unit in an array structure, only the light within the range which is in charge of each light sensing unit can be received, thereby increasing the resolution and contrast of the input fingerprint image. In addition, it is possible to increase the physical mechanical strength of the fingerprint input itself. Physical strength is further increased by further forming a protective film.

Claims (3)

In the known TFT fingerprint input device which consists of a light-sensing part which consists of a light incident layer, the drain and the source electrode formed in the light incident layer surface, and the switching part in which the light shielding layer is formed in the drain and the source electrode in the surface, The light sensing unit, A light incident layer through which light incident upon reflection from a fingerprint is incident; A drain electrode and a source electrode connected to both ends of the light incident layer, An insulating layer formed on surfaces of the drain electrode and the source electrode, Is formed on the insulating layer and consists of a light shielding layer having an open portion to which the light incident layer is exposed, And the angle of incidence of light incident on the light incident layer is limited by an edge of the light shielding layer to reduce an incident angle range of light incident on the light incident layer. The method of claim 1, wherein the light shielding layer is At least covering the entire drain electrode and source electrode; And the opening is located in a light incidence area of the light incidence layer. The TFT fingerprint input device according to claim 1 or 2, wherein a passivation layer is formed on the light shielding layer so that the light incident layer is exposed through the opening.