KR20070071412A - Method for manufacturing thin film transistor and display substrate having the thin film transistor - Google Patents

Abstract

A method for manufacturing a switching device and a display substrate are provided to improve the generation of vertical afterimages on a display screen by reducing a leakage current by improving on/off driving characteristics of the switching device. A gate electrode is formed on a base substrate. A channel part(122) is formed in correspondence to the gate electrode, and is formed by stacking an active layer(122a) made of an amorphous silicon and an ohmic contact layer(122b) made of an n+ amorphous silicon. A source electrode and a drain electrode separated from the source electrode are formed on the channel part. The active layer corresponding to a separation part of the source electrode and the drain electrode is crystallized.

Description

Method for manufacturing a switching device and a display substrate {METHOD FOR MANUFACTURING THIN FILM TRANSISTOR AND DISPLAY SUBSTRATE HAVING THE THIN FILM TRANSISTOR}

1 is a plan view of an electroluminescent display substrate according to an exemplary embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line II ′ of FIG. 1.

3 through 9 are process diagrams for describing a method of manufacturing the electroluminescent display substrate illustrated in FIG. 2.

<Description of the symbols for the main parts of the drawings>

100: electroluminescent display substrate 112: second gate electrode

122: second channel portion 122a: active layer

122b: ohmic contact layer 123: first region

124: second region 150: pixel electrode

170: electroluminescent layer 180: common electrode

The present invention relates to a method for manufacturing a switching element and a display substrate, and more particularly, to a method for manufacturing a switching element and a display substrate for improving a vertical afterimage of a display screen.

An organic light emitting diode (OLED) includes a light emitting layer positioned between two electrodes and the electrode, and electrons injected from one electrode and holes injected from another electrode are formed in the light emitting layer. They combine to form excitons, which emit light while releasing energy. The organic light emitting display device is classified into a passive matrix type and an active matrix type.

 Most of the products currently commercialized are passive matrix organic light emitting diodes (Passive Matrix Organic Light Emitting Diode), a simple structure in which organic material is inserted between orthogonal anode wiring and cathode wiring. However, due to the high power consumption, large area is difficult and high resolution is difficult.

Active Matrix Organic Light Emitting Diodes (AMOLEDs) have thin film transistors that switch each pixel, and each pixel is controlled using a switching element, so power consumption is low and image quality is excellent. There is an advantage that can be obtained.

On the other hand, at least two TFTs are used to drive the AMOLED because the organic light emitting diode has a characteristic of increasing brightness according to the amount of current. One is a switching TFT and the other is a driving TFT for current control. AMOLED transistors are developing polycrystalline silicon TFTs with large output currents. The solid phase crystallization (SPC) method used to form polycrystalline silicon can obtain a polycrystalline silicon thin film by simple heat treatment, but the heat treatment temperature is higher than 600 degrees and the heat treatment time is too long to use glass as the base substrate. The disadvantage is that it is difficult to do. Therefore, various crystallization methods (Low Temperature Poly-Si) have been studied for obtaining polycrystalline silicon at a low temperature as short as possible in order to prepare poly-silicon (Poly-Si) TFT.

On the other hand, the switching element of the AMOLED includes a gate electrode extending from the gate wiring, a source electrode extending from the source wiring, a drain electrode spaced a predetermined distance from the source electrode, and electrically connected to an electroluminescent device, the gate electrode and the source. And a channel portion formed between the electrode and the drain electrode.

Since polycrystalline silicon has a lower bandgap energy than amorphous silicon, when the entire channel portion is formed of polycrystalline silicon, problems such as transition due to traps and direct transition occur. At this time, the electron-hole pairs respectively move to the drain / source region, causing an increase in leakage current. In addition, the band of band tunneling increases due to the large bending of the energy band due to the high electric field formed in the overlapping region of the gate electrode and the drain electrode. Increasing the transition between bands causes an increase in the gate induced drain leakage (GIDL). Accordingly, there is a problem in that vertical afterimages occur on the display screen.

Accordingly, the technical problem of the present invention is to solve such a conventional problem, and an object of the present invention is to provide a method of manufacturing a switching device for improving vertical afterimages.

Another object of the present invention is to provide a display substrate manufactured using the above-described method for manufacturing a switching element.

According to one or more exemplary embodiments, a method of manufacturing a switching device includes forming a gate electrode on a base substrate, an active layer formed of amorphous silicon, and an n + amorphous silicon. Forming a channel portion in which an ohmic contact layer is sequentially stacked; forming a source electrode and a drain electrode spaced a predetermined distance from the source electrode on the channel portion; Crystallizing the corresponding active layer.

In order to realize the above object of the present invention, the display substrate according to the exemplary embodiment includes a gate wiring, a source wiring, a switching element, a bias voltage wiring, a driving element, and a light emitting element. The gate wiring extends in the first direction. The source wiring extends in a second direction crossing the first direction. The switching element is connected to the gate wiring and the source wiring. The bias voltage wiring is adjacent to the source wiring and extends in the second direction. The driving device includes a source electrode connected to the bias voltage line and a gate electrode connected to the switching element. The light emitting device is connected to the drain electrode of the driving device. The first channel portion of the driving device may include a first region made of amorphous silicon corresponding to the source and drain electrodes, and a second region made of polycrystalline silicon corresponding to a spaced portion of the source and drain electrodes.

According to the method of manufacturing the switching device and the display substrate, the on / off driving characteristics of the switching device are improved to reduce the leakage current, thereby improving the generation of afterimages on the display screen.

Hereinafter, with reference to the accompanying drawings, it will be described in detail the present invention.

 In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. As described in the drawing, when it is described from an observer's point of view, when a part such as a layer, a film, an area, or a plate is "on" another part, it is not only when another part is "directly" but also another part in between. It also includes the case. On the contrary, when a part is "just above" another part, it means that there is no other part in the middle.

1 is a plan view of an electroluminescent display substrate according to an exemplary embodiment of the present invention.

Referring to FIG. 1, the electroluminescent display substrate includes a plurality of pixel portions defined by a plurality of source lines DL, a plurality of gate lines GL, and a plurality of bias voltage lines VL. P).

The source lines DL and the bias voltage lines VL extend in a first direction, and the gate lines GL extend in a second direction crossing the first direction.

In each pixel portion P, a first switching element TFT1, a second switching element TFT2, a storage capacitor CST, and an electroluminescent element EL are formed.

The first switching element TFT1 includes a first gate electrode 111 connected to the gate line GL, a first source electrode 131 connected to the source line DL, the storage capacitor CST, and a second The first drain electrode 132 is connected to the switching element TFT2 in common. In addition, the first switching element TFT1 includes the first gate electrode 111 and a first channel portion 121 formed between the first source and drain electrodes 131 and 132.

The second switching element TFT2 may include a second gate electrode 112 connected to the first drain electrode 132, a second source electrode 133 connected to the bias voltage line VL, and the electroluminescent element EL. ) And a second drain electrode 134 connected thereto. In addition, the second switching element TFT2 includes the second gate electrode 112 and a second channel portion 122 formed between the second source and drain electrodes 133 and 134. The second switching element TFT2 is a driving element for driving the electroluminescent element EL.

The storage capacitor CST is in electrical contact with the first drain electrode 132 and the first contact hole 141, and the first electrode 113 and the bias voltage connected to the second gate electrode 112. The second electrode 135 is connected to the wiring VL.

The electroluminescent device EL is interposed between a pixel electrode 150 connected to the second drain electrode 134, a common electrode (not shown), and the pixel electrode 150 and a common electrode (not shown). The electroluminescent layer 170.

The driving method of the pixel portion P is as follows. When a gate signal is applied from the gate line GL, the first switching element TFT1 is turned on so that the source signal transferred from the source wiring DL is passed through the first switching element TFT1. The second switching element TFT2 is turned on and charged in the storage capacitor CST.

As the second switching element TFT2 is turned on, the source voltage via the first switching element TFT1 is based on the bias voltage transferred from the bias voltage line VL. Is delivered). As a result, the EL device emits light having a predetermined brightness.

FIG. 2 is a cross-sectional view taken along the line II ′ of FIG. 1.

1 and 2, the electroluminescent display substrate includes a base substrate 101. The source wiring DL, the gate wiring GL, the bias voltage wiring VL, the first switching device TFT1, the second switching device TFT2, and a storage capacitor are disposed on the base substrate 101. CST) and the electroluminescent element EL are formed.

In detail, the second switching element TFT2 includes a second gate electrode 112 formed on the base substrate 101, a second channel portion 122 formed on the second gate electrode 112, and the second switching element TFT2. And second source and drain electrodes 133 and 134 formed on the two channel portions 122.

The second channel part 122 may include a first region 123 corresponding to the second source electrode 133 and a second drain electrode 134, and the second source electrode 133 and a second drain electrode 134. And a second region 124 corresponding to the spaced portion.

The first region 123 has a structure in which an active layer 122a made of amorphous silicon and an ohmic contact layer 122b made of amorphous silicon doped with a high concentration of n + ions are sequentially stacked. The second region 124 is connected to the active layer 122a of the first region and is made of poly-silicon (Poly-Si).

Although not shown in FIG. 2, the first channel portion 121 of the first switching element TFT1 is also formed in the same structure as the second channel portion 122.

A gate insulating layer 102 is formed between the second gate electrode 112 and the second channel portion 122, and a passivation layer 103 is formed on the second source and drain electrodes 133 and 134. .

The storage capacitor CST is formed on the first electrode 113 formed on the base substrate 101, the gate insulating layer 102 formed on the first electrode 113, and the gate insulating layer 102. The second electrode 135 is formed. The passivation layer 103 is formed on the second electrode 135.

In the electroluminescent device EL, a pixel electrode 150 is formed on a base substrate 101 on which the gate insulating layer 102 and the passivation layer 103 are sequentially formed, and an electroluminescent layer on the pixel electrode 150. A 170 is formed, and a common electrode 180 is formed on the EL layer 170. The pixel electrode 150 is an anode of the electroluminescent device EL, and the common electrode 180 is a cathode of the electroluminescent device EL.

The electroluminescent layer 170 includes a part or all of a hole injection layer, a hole transport layer, a light emitting layer, an electron injection layer, and an electron transport layer, and is formed in the emission region defined as the bank layer 160 on the pixel electrode 150. .

3 to 8 are process diagrams for describing a method of manufacturing the electroluminescent display substrate illustrated in FIG. 2.

1 and 3, the electroluminescent display substrate includes a base substrate 101. The base substrate 101 may be formed of, for example, glass, sapphire or polyester, polyacrylate, polycarbonate, and poly ether ketone. It is formed of a transparent synthetic resin such as.

Gate metal patterns are formed by depositing and patterning a gate metal layer on the base substrate 101. The gate metal layer is, for example, a metal such as chromium, aluminum (Al), tantalum (Ta), molybdenum (Mo), titanium (Ti), tungsten (W), copper (Cu), silver (Ag), or the like. After the deposition by a sputtering process to a conductive film containing an alloy containing a mixture, and patterned to form gate metal patterns.

The gate metal patterns may include gate lines GL, first and second gate electrodes 111 and 112 of the first and second switching elements TFT1 and TFT2, and a first electrode of the storage capacitor CST. 113).

A gate insulating layer 102 is formed on the base substrate 101 on which the gate metal patterns are formed. The gate insulating layer 102 is formed of a silicon oxide film or a silicon nitride film.

Subsequently, an active layer 122a made of amorphous silicon and an ohmic contact layer 122b made of amorphous silicon heavily doped with n + ions are sequentially stacked on the base substrate 101 on which the gate insulating layer 102 is formed.

Subsequently, the active layer 122a and the ohmic contact layer 122b are patterned by a photolithography process to form a first channel portion 121 on the portion where the first gate electrode 111 is located, and the second gate The second channel part 122 is formed on the portion where the electrode 112 is located.

1 and 4, source metal patterns are formed by depositing and patterning a source metal layer on a base substrate 101 on which the first and second channel portions 121 and 122 are formed. The source metal layer may include, for example, a metal such as molybdenum (Mo), copper (Cu), silver (Ag), aluminum (Al), chromium (Cr), tantalum (Ta), titanium (Ti), or a mixture thereof. After depositing by a sputtering process to a conductive layer containing an alloy containing, it is patterned to form the source metal patterns.

The source metal patterns may include the source wires DL, first and second source electrodes 131 and 133, first and second drain electrodes 132 and 134, and a second electrode 135 of a storage capacitor CST. ). The first drain electrode 132 is formed to be spaced apart from the first source electrode 131 by a predetermined distance, and the second drain 134 electrode is formed to be spaced apart from the second source electrode 133 by a predetermined distance. Accordingly, the ohmic contact layer 122b of the first and second channel portions 121 and 122 may be disposed at the spaced apart portions of the first and second source electrodes 131 and 133 and the first and second drain electrodes 132 and 134. Is exposed.

Subsequently, the ohmic contact layer 122b is etched using the first and second source electrodes 131 and 133 and the first and second drain electrodes 132 and 134 as an etch mask. Therefore, a part of the active layer 122a made of amorphous silicon is exposed at the spaced portion.

FIG. 5 is an enlarged view of the second switching device illustrated in FIG. 4.

Referring to FIG. 5, the catalyst metal CM is coated on the base substrate 110 on which the source metal pattern is formed. The catalyst metal (CM) is made of, for example, nickel (Ni), and other metals may be used to facilitate the crystallization of the amorphous silicon. The catalyst metal CM is coated on the base substrate 110 to a thickness of several tens of angstroms.

Subsequently, the base substrate coated with the catalyst metal (CM) is heat-treated in a furnace at 300 ° C to 500 ° C. As the heat treatment proceeds, the catalytic metal molecules coated on the active layer 122a diffuse into the active layer 122a by the diffusion principle. Amorphous silicon molecules in the active layer 122a are rearranged by the migration path of the catalytic metal molecules. This facilitates crystallization of the amorphous silicon even at low temperatures of 300 ° C to 500 ° C.

The crystallization of the amorphous silicon starts from the spaced portion where the catalytic metal (CM) is directly applied on the active layer 122a, and the crystallization region is extended as the heat treatment time elapses. Therefore, the second channel portion 122 may be locally crystallized by adjusting the heat treatment time.

For example, the heat treatment process is performed for a time during which only the active layer 122a in the region corresponding to the separation portion can be crystallized. That is, when the heat treatment process is completed, the active layer 122a corresponding to the spacer part is made of poly-silicon (Poly-Si), and the active layer 122a and the ohmic contact layer 122b corresponding to the source electrode and the drain electrode are It remains in the amorphous silicon state.

 Accordingly, the second channel portion 122 includes a first region 123 in which an active layer 122a made of amorphous silicon and an ohmic contact layer 122b made of amorphous silicon doped with a high concentration of n + ions are sequentially stacked; It is formed to be connected to the active layer 122a of the first region 123 and to include a second region 124 made of poly-silicon (Poly-Si). In FIG. 5, the second channel unit 122 of the second switching element TFT2 is described as an example, but the first channel unit 121 of the first switching element TFT1 is formed in the same manner.

On the other hand, the catalyst metal (CM) is applied in a very small amount, it does not affect the brightness of the display screen. However, if necessary, a cleaning process for removing the catalyst metal CM remaining on the base substrate 110 may be performed. In one example, the cleaning process may be performed using an aqueous hydrofluoric acid solution.

5 and 6, the passivation layer 103 is formed on the base substrate 101 on which the crystallization process is completed. Subsequently, the passivation layer 103 is partially removed to form a second contact hole 142 on the second drain electrode 134.

The pixel electrode 150 is formed by depositing and patterning a transparent conductive material or an opaque material metal on the base substrate 101 on which the second contact hole 142 is formed. As the transparent conductive material, indium tin oxide (ITO) or indium zinc oxide (IZO) is used as an example. The pixel electrode 150 is patterned to be formed in the pixel region P defined by the source wiring DL, the bias voltage wiring VL, and the adjacent gate wiring GL.

The pixel electrode 150 is electrically connected to the second drain electrode 134 through the second contact hole 142, and the pixel electrode 150 is an anode of the electroluminescent device EL. Electrode).

1 and 7, a bank unit 160 is formed on the base substrate 101 on which the first and second switching elements TFT1 and TFT2 and the pixel electrode 150 are formed.

The bank unit 160 forms an inorganic film material such as SiO 2 and TiO 2 through sputtering, coating, chemical vapor deposition, or the like. Or after apply | coating the material which has heat resistance and solvent resistance, such as an acrylic resin and a polyimide resin, on a base board, it forms by patterning by photolithography technique etc. For example, the bank layer 160 is patterned through a mask 300 on which an opening pattern 310 defining a non-emission area and a light blocking pattern 320 defining a light emission area are formed.

By the exposure process, the bank layer 160 corresponding to the opening pattern 310 is cured, and the bank layer 160 corresponding to the light blocking pattern 320 is not cured. Subsequently, the bank layer 160 corresponding to the light blocking pattern 320 is etched by a developing process to define the emission area LA in the pixel area P.

Subsequently, the surface of the bank layer 160 is formed of a region showing lyophilic (affinity for droplets) and a region showing liquid repellency (resistance against droplets) through a plasma treatment process. The lyophilic region has a relatively large surface energy, and the liquid-repellent region has a relatively small surface energy.

Referring to FIG. 8, the electroluminescent layer 170 is formed in the emission area LA defined by the bank layer 160 by solution processing. The solution treatment process includes a spin coating method, a dip coating method, and an ink jet printing method.

The electroluminescent layer 170 includes a hole transport layer (HTL) and an emission layer (ELM), and includes a separate electron transport layer (ETL) and an electron injecting layer (EIL). One or more layers that contribute to the improvement of device characteristics, such as a hole injection layer (HIL) or a hole blocking layer (HBL), may be further inserted.

Specifically, the hole injection layer / transport layer (HIL / HTL) 171, the emission layer 172, and the electron injection layer / transport layer (EIL / ETL) are formed on the pixel electrode 150 in the emission area LA by inkjet printing. 173) are formed sequentially.

As the hole transport layer, for example, polyethylene dioxythiophene, triphenylanyl derivative (TPD), pyrazoline derivative, aryl amine derivative, stilbene derivative, tripetyl diamine derivative and the like are used.

The hole injection layer may be formed in place of the hole transport layer, and both the hole injection layer and the hole transport layer may be formed. In addition, one or more layers for improving the characteristics of the device may be formed separately or simultaneously with the hole transport layer or the hole injection layer.

The light emitting layer may be a low molecular organic light emitting material or a high molecular organic light emitting material, that is, a light emitting material made of various fluorescent materials or phosphorescent materials.

9, a common electrode 180 is formed on the base substrate 101 on which the electroluminescent layer 170 is formed. The common electrode 180 may be made of a transparent conductive material or a metal material of an opaque material. The common electrode 180 is made of, for example, indium tin oxide (ITO) or indium zinc oxide (IZO). The common electrode 180 is formed by chemical vapor deposition, sputtering, or the like.

A protective layer 190 may be formed on the common electrode 180 to prevent penetration of moisture and / or oxygen. The protective layer 190 is formed of a transparent material so that light generated from the organic light emitting layer 170 may be transmitted.

The protective layer 190 may include an inorganic protective film made of silicon oxide and an organic protective film formed by applying an epoxy having a small moisture permeability.

As described above, the channel portion of the display substrate according to the present invention includes a first region formed corresponding to the source electrode and the drain electrode, and a second region corresponding to the spaced portion of the source electrode and the drain electrode. The first region has a structure in which an active layer made of amorphous silicon and an ohmic contact layer made of n + amorphous silicon are sequentially stacked, and the second region is formed by being connected to the active layer and made of polycrystalline silicon. Therefore, a low off leakage current of the amorphous silicon switching element and a high on current of the polycrystalline silicon switching element can be obtained. Accordingly, the on / off driving characteristic of the switching element is improved to reduce the leakage current, thereby improving the generation of afterimages on the display screen.

Although described above with reference to the embodiments, those skilled in the art can be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below. I can understand.

Claims (8)

Forming a gate electrode on the base substrate; Forming a channel part formed corresponding to the gate electrode and sequentially stacking an active layer made of amorphous silicon and an ohmic contact layer made of n + amorphous silicon; Forming a source electrode and a drain electrode spaced apart from the source electrode by a predetermined distance on the channel portion; And crystallizing an active layer corresponding to the separation portion of the source electrode and the drain electrode. The method of claim 1, wherein crystallizing the active layer Etching the ohmic contact layer corresponding to the spacer to expose the active layer; Applying a catalyst metal on the base substrate to which the active layer is exposed; And heating the base substrate to which the catalyst metal is applied. The method of claim 2, wherein the heat treatment is performed at a temperature of 300 to 550 degrees. The method of claim 2, wherein the catalytic metal is nickel. The method of claim 2, wherein the catalytic metal is applied to a thickness of 10 to 200 Angstroms. A switching element connected to the gate wiring extending in the first direction and the source wiring extending in the second direction crossing the first direction; A bias voltage wiring adjacent to the source wiring and extending in the second direction; A driving device including a source electrode connected to the bias voltage line and a gate electrode connected to the switching element; And A light emitting device connected to the drain electrode of the driving device; The first channel portion of the driving device includes a first region made of amorphous silicon corresponding to the source and drain electrodes and a second region made of polycrystalline silicon corresponding to the spaced portion of the source and drain electrodes. Board. The switching device of claim 6, wherein the switching element comprises a gate electrode connected to the gate line, a source electrode connected to the source line, and a drain electrode connected to the driving element. The second channel portion of the switching element includes a first region made of amorphous silicon corresponding to the source and drain electrodes, and a second region made of polycrystalline silicon corresponding to the separation portion of the source and drain electrodes. Board. The display substrate of claim 6, wherein the light emitting device comprises an anode electrode electrically connected to the drain electrode, a light emitting layer formed on the anode electrode to define a light emitting region, and a cathode electrode formed on the light emitting layer.

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