KR20080064412A - Photosensor - Google Patents

Abstract

An optical sensor is provided to form an etch stopper without additional masks and to provide an optical sensor with low voltage high output by using an amorphous silicon thin film transistor. An optical sensor includes a gate electrode(120), a gate insulation layer(140), a semiconductor(150), an oxide layer(160), a resistive contact member(170), and a passivation layer(180). The gate electrode is formed on a substrate. The gate insulation layer is formed on the gate electrode. The semiconductor is formed on the gate insulation layer. The oxide layer is formed on the semiconductor. The resistive contact member is formed on the oxide layer. The passivation layer is formed on the resistive contact member. The semiconductor is formed by a hydro-amorphous silicon.

Description

Optical sensor {PHOTOSENSOR}

1 is a block diagram of a liquid crystal display including an optical sensor according to an exemplary embodiment of the present invention.

2 is an equivalent circuit diagram of one pixel of a liquid crystal display including an optical sensor according to an exemplary embodiment of the present invention.

3 is a schematic diagram of a liquid crystal display including an optical sensor according to an exemplary embodiment of the present invention.

4 is a cross-sectional view of a sensing element of an optical sensor according to an embodiment of the present invention.

The present invention relates to an optical sensor.

The display device includes a cathode ray tube, an organic electro-luminescence display, a plasma display, and a liquid crystal display that do not emit light by themselves and require a separate light source. (liquid crystal display).

A general liquid crystal display device includes two display panels including a pixel electrode and a common electrode and a liquid crystal layer having dielectric anisotropy interposed therebetween. The pixel electrodes are arranged in a matrix form and connected to a switching element such as a thin film transistor (TFT) to receive data voltages one by one in sequence. The common electrode is formed over the entire surface of the display panel and receives a common voltage. The pixel electrode, the common electrode, and the liquid crystal layer therebetween form a liquid crystal capacitor, and the liquid crystal capacitor becomes a basic unit that forms a pixel together with a switching element connected thereto.

In such a liquid crystal display, a voltage is applied to two electrodes to generate an electric field in the liquid crystal layer, and the intensity of the electric field is adjusted to adjust the transmittance of light passing through the liquid crystal layer to obtain a desired image. In this case, in order to prevent deterioration caused by the application of an electric field in one direction for a long time, the polarity of the data voltage with respect to the common voltage is inverted frame by frame, row by pixel, or pixel by pixel.

Recently, a product having an optical sensor in such a liquid crystal display has been developed. The optical sensor detects a change in light according to the touch of a hand, a touch pen, or the like on the screen of the liquid crystal display, and provides the sensing signal to the liquid crystal display. The liquid crystal display receives a detection signal from an optical sensor, processes the signal appropriately, and transmits the detected signal to an external device. do.

The present invention provides a low voltage high output optical sensor using an amorphous silicon thin film transistor and provides an optical sensor capable of forming an etch stopper without an additional mask.

The optical sensor according to an embodiment of the present invention for achieving the technical problem is a gate electrode formed on a substrate, a gate insulating film formed on the gate electrode, a semiconductor formed on the gate insulating film, is formed on the semiconductor An oxide film, an ohmic contact member formed on the oxide film, and a protective film formed on the ohmic contact member.

The semiconductor may be made of hydrogenated amorphous silicon.

The semiconductor may be 300 kW to 1000 kW.

The oxide layer may be 1 nm to 3 nm.

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated by like reference numerals throughout the specification. When a part of a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the other part being "right over" but also another part in the middle. On the contrary, when a part is "just above" another part, there is no other part in the middle.

A display device incorporating an optical sensor according to an exemplary embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

1 is a block diagram of a liquid crystal display including an optical sensor according to an embodiment of the present invention, FIG. 2 is an equivalent circuit diagram of one pixel of a liquid crystal display including an optical sensor according to an embodiment of the present invention. 3 is a schematic diagram of a liquid crystal display including an optical sensor according to an exemplary embodiment of the present invention.

As shown in FIG. 1, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal panel assembly 300, an image scanning unit 400, a data driver 500, and a sensing scan connected thereto. The unit 700 includes a signal reader 800, a gray voltage generator 550 connected to the data driver 500, and a signal controller 600 for controlling the gray voltage generator 550.

The liquid crystal panel assembly 300 is connected to a plurality of signal lines G ₁ -G _n , D ₁ -D _m , S ₁ -S _n , P ₁ -P _m , P _SG , and P _SD in an equivalent circuit. It includes a plurality of pixels arranged in a substantially matrix form.

The signal lines G ₁ -G _n and D ₁ -D _m include a plurality of image scanning lines G ₁ -G _n for transmitting an image scanning signal and data lines D ₁ -D _m for transmitting an image data signal. do. The image scanning lines G ₁ -G _n extend substantially in the row direction and are substantially parallel to each other, and the data lines D ₁ -D _m extend substantially in the column direction and are substantially parallel to each other.

Includes a detection signal (P ₁ -P _m) to pass - (S _n S ₁₎ and the detection signal lines _{(S 1 -S n, P 1} -P m) comprises a plurality of scan lines for transmitting a detection signal detected injection . The sensing scan lines S ₁ -S _n extend substantially in the row direction and are substantially parallel to each other, and the sensing signal lines P ₁ -P _m extend substantially in the column direction and are substantially parallel to each other.

The signal lines P _SG and P _SD include a control voltage line P _SG for transmitting the control voltage V _SG and an input voltage line P _SD for transferring the input voltage V _SD , and extend in the row or column direction. have.

Each pixel includes a switching element Q _S1 connected to a signal line G ₁ -G _n , D ₁ -D _m , and a liquid crystal capacitor C _LC and a storage capacitor C _ST connected thereto. It includes. The holding capacitor C _ST can be omitted as necessary.

The switching element Q _S1 , such as a thin film transistor, is a three-terminal element whose control terminal and input terminal are connected to the image scanning line G ₁ -G _n and the data line D ₁ -D _m, respectively, and the output terminal is a liquid crystal. It is connected to a capacitor (C _LC ) and a holding capacitor (C _ST ).

The liquid crystal capacitor C _LC has two terminals, a pixel electrode (not shown) of the lower panel 100 of the liquid crystal panel assembly 300 and a common electrode (not shown) of the upper panel 200. The liquid crystal layer functions as a dielectric. The pixel electrode is connected to the switching element Q _s1 , and the common electrode is formed on the front surface of the upper panel 200 and receives the common voltage V _com .

The storage capacitor C _ST , which serves as an auxiliary part of the liquid crystal capacitor C _LC , is formed by overlapping a separate signal line (not shown) and a pixel electrode of the lower panel 100 with an insulator interposed therebetween. A predetermined voltage such as the common voltage V _com is applied to the signal line of. However, the storage capacitor C _ST may be formed such that the pixel electrode overlaps the front gate line directly above the insulator.

On the other hand, to implement color display, each pixel uniquely displays one of the three primary colors (spatial division) or each pixel alternately displays the three primary colors over time (time division) so that the desired color can be selected by the spatial and temporal sum of these three primary colors. To be recognized. As an example of spatial division, each pixel may include a red, green, or blue color filter (not shown) in a region corresponding to the pixel electrode.

The pixel also includes an optical sensor, which includes a sensing element Q _P connected to the signal lines P _SG , P _SD , and a switching element Q _S2 connected to the signal lines S ₁ -S _n , P ₁ -P _m . And a sense signal capacitor C _P connected thereto. However, not all pixels need to include such an optical sensor, and for example, one pixel of the plurality of pixels may include an optical sensor or an optical sensor for each pixel spaced at predetermined intervals. That is, the formation density of the photosensor may be adjusted as needed, and accordingly, the number of sensing scan lines S ₁ -S _n and sensing signal lines P ₁ -P _m may be adjusted.

The sensing element Q _P is a three-terminal element whose control terminal and input terminal are connected to the control voltage line P _SG and the input voltage line P _SD, respectively, and the output terminal is a sensing signal capacitor C _P and a switching element. Is connected to (Q _S2 ). In the sensing element Q _P , when the channel semiconductor is irradiated with light, the channel semiconductor consisting of amorphous silicon or polycrystalline silicon forms a photo current, and the photo current is generated by the input voltage V _SD applied to the input voltage line P _SD . Flows in the direction of the sense signal capacitor C _P and the switching element Q _S2 .

The sensing signal capacitor C _{P is} connected between the sensing element Q _P and the control voltage line P _SG , and accumulates charges according to the photocurrent from the sensing element Q _P to maintain a predetermined voltage. The sensing signal capacitor C _P may be omitted as necessary.

The switching element Q _S2 is also a three-terminal element whose control terminal, output terminal and input terminal are connected to the sensing scan lines S ₁ -S _n , the sensing signal lines P ₁ -P _m and the sensing elements Q _P, respectively. It is. The switching element Q _S2 is a voltage stored in the sensing signal capacitor C _P or the sensing element Q _P when a voltage for turning on the switching element Q _S2 is applied to the sensing scan lines S ₁ -S _n . The photocurrent from is output to the sensing signal lines P ₁ -P _m as sensing signals V _P.

The switching elements Q _S1 and Q _S2 and the sensing element Q _P may be formed of amorphous silicon or poly crystalline silicon thin film transistors.

Meanwhile, although the optical sensor is described as being included in the pixel, the optical sensor may be disposed in a separate area between the pixels or outside the pixel.

As shown in FIG. 3, the liquid crystal panel assembly 300 includes a black matrix 32 defining a display area 31, and includes pixels and signal lines G ₁ -G _n , D ₁ -D _m , S _1. Most of -S _n , P ₁ -P _m , P _SG , and P _SD are located in the display area 31. Since the upper panel 200 is smaller than the lower panel 100, a portion of the lower panel 100 is exposed, and the data line D ₁ -D _m extends to be connected to the data driver 500. . The scan lines G ₁ -G _n and S ₁ -S _n also extend into regions obscured by the black matrix 32 to connect with the image scanning unit 400 and the sensing scanning unit 700, respectively.

Referring back to FIG. 1, the gray voltage generator 550 generates two sets of gray voltages related to the transmittance of the pixel. One of the two sets has a positive value for the common voltage (V _com ) and the other set has a negative value.

The image scanning unit 400 is connected to the image scanning lines G ₁ -G _n of the liquid crystal panel assembly 300 to display an image scanning signal formed by a combination of a gate on voltage V _on and a gate off voltage V _off . It is applied to the scan line G ₁ -G _n .

The data driver 500 is connected to the data lines D ₁ -D _m of the liquid crystal panel assembly 300 to select the gray voltage from the gray voltage generator 550 and apply the gray voltage to the pixel as a data signal.

The sensing scan unit 700 is connected to the sensing scan lines S ₁ -S _n of the liquid crystal panel assembly 300 to sense a sensing scan signal formed by a combination of a gate on voltage V _on and a gate off voltage V _off . It is applied to the scanning lines S ₁ -S _N.

The image scanning unit 400 and the sensing scanning unit 700 include a plurality of stages arranged substantially in a row as a shift register. In FIG. 3, the image scanning unit 400 and the sensing scanning unit 700 are positioned in the region covered by the black matrix 32 and are formed in the same process as the switching elements Q _S1 and Q _S2 and the sensing element Q _P. Are integrated. However, it may be mounted in the form of an integrated circuit (IC).

Signal reading unit 800 receives the predetermined detection signal (V _P) output is connected to the detection signal of the liquid crystal panel assembly _{(300) (P 1 -P m} ) detected through the signal line (P ₁ -P _m) Signal processing is performed.

The signal controller 600 controls operations of the image scanner 400, the data driver 500, the sensing scanner 700, and the signal reader 800.

The gray voltage generator 550, the data driver 500, the signal reader 800, and the signal controller 600 are implemented as a single chip 33 as illustrated in FIG. 3 to form a chip on glass (COG) method. The liquid crystal panel assembly 300 is mounted on the liquid crystal panel assembly 300. However, the plurality of individual chips may be mounted in a COF (chip on film) method.

4 is a cross-sectional view illustrating a sensing element of an optical sensor according to an exemplary embodiment of the present invention. As shown in FIG. 4, a gate electrode 120 is formed on a lower display panel 100.

The gate electrode is made of aluminum-based metal such as aluminum (Al) or aluminum alloy, silver-based metal such as silver (Ag) or silver alloy, copper-based metal such as copper (Cu) or copper alloy, and molybdenum-based metal such as molybdenum (Mo) or molybdenum alloy , Chromium (Cr), tantalum (Ta) and titanium (Ti). However, they may have a multilayer structure including two conductive films (not shown) having different physical properties. One of the conductive films is made of a metal having low resistivity, such as aluminum-based metal, silver-based metal, or copper-based metal, so as to reduce signal delay or voltage drop. In contrast, other conductive films are made of other materials, particularly materials having excellent physical, chemical, and electrical contact properties with indium tin oxide (ITO) and indium zinc oxide (IZO), such as molybdenum-based metals, chromium, tantalum, and titanium. Good examples of such a combination include a chromium bottom film, an aluminum (alloy) top film, and an aluminum (alloy) bottom film and a molybdenum (alloy) top film. However, the gate electrode 120 may be made of various other metals or conductors.

A gate insulating layer 140 made of silicon nitride (SiNx) or silicon oxide (SiOx) is formed on the gate electrode 120.

On the gate insulating layer 140, a semiconductor 150 made of hydrogenated amorphous silicon (amorphous silicon is abbreviated a-Si) is formed. Amorphous amorphous silicon (hydrogenated amorphous silicon) is deposited at 300 kPa to 1000 kPa.

An oxide film 160 is formed on the semiconductor 150.

The oxide layer 160 is formed to have a thickness of 1 to 3 nm, and serves as an etch stop layer of a process for forming the ohmic contact member 170 to be formed later.

An ohmic contact 170 is formed on the oxide film 160. The ohmic contact 170 is made of a material such as n + hydrogenated amorphous silicon in which n-type impurities such as phosphorus are heavily doped.

The passivation layer 180 is formed on the ohmic contact 170.

In the process of forming the optical sensor, the gate electrode 120, the gate insulating layer 140, and the semiconductor 150 are sequentially formed, and the oxide film 160 is formed on the surface of the semiconductor 150 in an amount of 1 to 3 nm by using O ₂ plasma. do.

Thereafter, a material layer such as n + hydrogenated amorphous silicon in which n-type impurities are heavily doped is formed and dry-etched to form an ohmic contact 170. Here, etching is performed using plasma etching, and only Si is selectively etched using SF ₆ + Cl ₂ + He as an etching gas.

In the sensing element of the optical sensor formed as described above, the oxide layer 160 is formed by the first external semiconductor light between the semiconductor 150 made of hydrogenated amorphous silicon and the ohmic contact member 170 made of a material such as n + hydrogenated amorphous silicon. As the Fermi level moves, the channel voltage is lowered to prevent the inflow of charge in a region where a low voltage difference is maintained when a carrier is introduced from a source. As a result, the effect of lowering the off current of the optical sensor is further reduced, and the inflow of carriers is exploded by the avalanche process when the threshold voltage difference that can tunnel the barrier is exceeded. Will happen.

In addition, the oxide layer protects the channel region during the etching of the material layer such as the n + hydrogenated amorphous silicon, thereby minimizing the damage and contamination of the channel that may occur due to exposure to the plasma during the subsequent process and at the same time reducing the thickness of the channel.

Thus, according to this invention, a low voltage high output optical sensor can be provided.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims (4)

A gate electrode formed on the substrate, A gate insulating film formed on the gate electrode, A semiconductor formed on the gate insulating film, An oxide film formed on the semiconductor, An ohmic contact formed on the oxide film, and A protective film formed on the ohmic contact member Optical sensor comprising a. In claim 1, The semiconductor is an optical sensor consisting of hydrogenated amorphous silicon. In claim 1, The semiconductor is an optical sensor of 300Å to 1000Å. In claim 1, The oxide film is an optical sensor of 1nm to 3nm.

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