KR101036749B1 - Fabrication method of liquid crystal display device using metal induced crystallization - Google Patents

Abstract

The present invention relates to a metal-induced crystallization method, comprising: forming an active layer on a substrate; Forming a gate electrode having a first insulating layer interposed on the active layer; Doping an impurity into the active layer using the gate electrode as a mask to form a source region and a drain region; Forming a metal film on the gate electrode including a source region and a drain region of the active layer; Forming a second insulating layer made of a silicon nitride film containing hydrogen ions on the metal film; A high temperature annealing method (RTA) using an ultraviolet lamp heats the second insulating layer formed on the active layer and the metal film to crystallize the active layer through metal induced crystallization and simultaneously contains hydrogen contained in the second insulating layer. Hydrogenating the active layer with ions; And forming a source and a drain electrode on the second insulating layer, wherein the second insulating layer heated by the ultraviolet lamp transfers absorbed heat into the active layer through a metal film below the crystallization layer. It is characterized in that to accelerate the process for manufacturing the liquid crystal display device, and when the crystallization proceeds by the RTA method, it is possible to achieve an efficient crystallization with a low heat source.

Silicon Nitride, Hydrogenation, RTA, Process Shortening

Description

Manufacturing method of liquid crystal display device by metal induction crystallization {FABRICATION METHOD OF LIQUID CRYSTAL DISPLAY DEVICE USING METAL INDUCED CRYSTALLIZATION}

1A to 1F are flow charts illustrating the steps of crystallizing a semiconductor layer by a general metal induction crystallization method.

2A to 2E are flowcharts showing a method of manufacturing a liquid crystal display device by the metal induction crystallization method of the present invention.

********** Explanation of symbols for the main parts of the drawings **********

201; Substrate 202: Buffer Layer

203: active layer 204: gate insulating film

205: gate electrode 206: metal film

207: interlayer insulating layer 208a, 208b: source, drain electrode

209: protective films 210a and 210b: source and drain regions

211 pixel electrodes

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to thin film transistors (TFTs) used in display devices, such as liquid crystal displays (LCDs) and organic light emitting diodes (OLEDs). The present invention relates to a method of manufacturing a thin film transistor in which an active layer is formed of crystalline silicone.

Thin film transistors used in display devices, such as LCDs, are usually formed by depositing silicon on a transparent substrate such as glass or quartz, forming a gate insulating layer and a gate electrode, and forming an active layer implanted with impurity ions in the source and drain regions. It is composed. The active layer constituting the source, drain region, and channel of the thin film transistor is usually formed by depositing a silicon layer using a chemical vapor deposition (CVD) method on a transparent substrate such as glass. However, the silicon layer deposited directly on the substrate by a method such as CVD has a low electron mobility as an amorphous silicon layer.

A display device using a thin film transistor as a switching element is required to have a high operating speed, and as the size of the display device decreases, the integration of the driving IC increases and the aperture ratio of the pixel region decreases. Therefore, the TFT increases the electron mobility of the silicon layer. It is necessary to form simultaneously with and increase the unit pixel aperture ratio. In order to achieve the above object, a technology of crystallizing a crystalline silicon layer having a crystalline structure having a high electron mobility by heat-treating the amorphous silicon layer has been introduced.

Various methods have been proposed to crystallize an amorphous silicon layer used as a channel of a thin film transistor into a crystalline silicon layer. The crystallization methods include solid phase crystallization (SPC) and excimer laser crystallization (ELC). Etc.

The SPC is a method of annealing an amorphous silicon layer over several hours to several tens of hours at a temperature of 600 ° C. or less, which is a deformation temperature of glass commonly used as a substrate. Since the SPC method requires a long time for heat treatment, when the productivity is low and the area of the substrate is large, there is a problem that deformation of the substrate may occur when the substrate is heat treated for a long time even at a temperature of 600 ° C. or less.

Excimer Laser Crystallization (ELC) is a method of scanning an excimer laser in a silicon layer for a very short time to generate a locally high temperature to crystallize the silicon layer instantaneously. The ELC method has a technical difficulty in precisely controlling the scanning of the laser light, and there is a problem in that productivity is lowered because only one substrate can be processed at a time.

In order to overcome the disadvantages of the conventional silicon layer crystallization method, a method of contacting metals such as nickel, gold and aluminum with amorphous silicon or injecting these metals into silicon has been introduced. This is to use the phenomenon that the phase change is induced to amorphous silicon by the element to crystalline silicon.

This phenomenon is called metal induced crystallization (MIC). In the case where a thin film transistor is manufactured using the MIC phenomenon, a metal remains in the crystalline silicon constituting the active layer of the thin film transistor. When applied to the channel portion of the problem occurs that leakage current occurs.

Recently, metal induced side crystallization (Metal Induced Lateral Crystallization) does not directly induce a phase change of silicon, but the silicide generated by the reaction between metal and silicon continues to propagate to the side as the MIC. A method of crystallizing a silicon layer using a MILC) phenomenon has been proposed.

Nickel (Ni) and palladium (Pd) are known as metals that cause the MILC phenomenon. The MILC phenomenon is a silicide interface including a metal that moves sideways as the phase change of the silicon layer propagates. In the case of crystallizing the silicon layer by using the crystallized silicon layer has almost no metal component used to induce crystallization has the advantage of forming a thin film transistor with improved current leakage and other operating characteristics.

In addition, in the case of using the MILC phenomenon, it is possible to induce crystallization of silicon at a relatively low temperature of 300 ° C to 500 ° C, so that it is possible to simultaneously crystallize several substrates without damaging the substrate than crystallization using a blast furnace. have.

1A to 1D are cross-sectional views showing prior art processes for crystallizing a silicon layer constituting a TFT using MIC and MILC phenomena.

As shown in FIG. 1A, an amorphous silicon layer is deposited on an insulating substrate 10 on which a buffer layer 11 is formed, and an active 12 is formed by patterning amorphous silicon by photolithography. Next, the gate insulating layer 13 and the gate electrode 14 are formed on the active layer 12 using a conventional method.

Next, as shown in FIG. 1B, the entire insulating substrate 10 is doped with a dopant using the gate electrode 14 as a mask, so that the source region 15a, the channel region 15c, and the drain are formed in the active layer 12. The area 15b is formed.

Then, as shown in FIG. 1C, the metal layer 16 is thinly deposited on the gate electrode 14, the active layer, and the entire substrate.

Next, when the entire substrate is annealed at a temperature of 300 ° C to 700 ° C, the source and drain regions 15a and 15b immediately below the remaining metal layer 16 are crystallized by MIC, and the metal layer 16 is not covered. The channel region 15c under the gate electrode is crystallized by a MILC phenomenon induced from the remaining metal layer 17.

FIG. 1D shows that the source and drain regions 15a and 15b of the active layer 12 are crystallized by MIC and the channel region 15c by MILC.

Next, as shown in FIG. 1E, an interlayer insulating layer 16 made of a silicon oxide film is formed on the gate electrode 14. After forming the interlayer insulating layer 16, as shown in FIG. 1F, contact holes are formed on the source and drain regions 15a and 15b, and source and drain electrodes 17a and 17b are formed. The protective film 18 is further formed.

The pixel electrode 19 is further formed on the protective film to complete the switching element of the liquid crystal display element.

However, in the MIC crystallization method, after the gate electrode is formed, a thin metal film is applied on the active layer including the gate electrode and warmed to proceed crystallization, and after the crystallization is completed, damaged during the process of forming an element. In order to stabilize the active layer or the like, a hydroprocessing step is further required. In addition, the MIC crystallization method is a metal film is formed directly on the amorphous silicon layer and the crystallization proceeds by heating, in particular, when heated by a fast annealing method (RTA) using an ultraviolet (ultra violet ray) lamp as a heat source Since the active layer is well heated in a specific wavelength band, energy is wasted in the remaining wavelength bands.

As mentioned above, when the crystallization is applied by the MIC crystallization method, the present invention removes the hydrogenation process of the crystalline silicon layer, and in particular, transfers heat effectively to the semiconductor layer that is crystallized when the crystallization is performed by the RTA method. It aims to promote crystallization.

In order to achieve the above object, a liquid crystal display device manufacturing method of the present invention comprises the steps of forming an active layer on a substrate; Forming a gate electrode having a first insulating layer interposed on the active layer; Doping an impurity into the active layer using the gate electrode as a mask to form a source region and a drain region; Forming a metal film on the gate electrode including a source region and a drain region of the active layer; Forming a second insulating layer made of a silicon nitride film containing hydrogen ions on the metal film; A high temperature annealing method (RTA) using an ultraviolet lamp heats the second insulating layer formed on the active layer and the metal film to crystallize the active layer through metal induced crystallization and simultaneously contains hydrogen contained in the second insulating layer. Hydrogenating the active layer with ions; And forming a source and a drain electrode on the second insulating layer, wherein the second insulating layer heated by the ultraviolet lamp transfers absorbed heat into the active layer through a metal film below the crystallization layer. It is characterized by promoting.

The metal-induced crystallization method can effectively perform crystallization at a low temperature below the transition temperature of the glass, and it has advantages in many aspects over the laser crystallization method that requires the use of expensive equipment and can crystallize only one substrate at a time.

Metal-induced crystallization is a method of crystallizing amorphous silicon by using a metal element as a catalyst for crystallization, the theoretical mechanism is various, among which the metal ion is combined with the silicon element to form silicide and the silicide by heating It is known that the metal elements forming the crystallized later silicon crystallized.

In the metal-induced crystallization method, crystallization is promoted by a metal element which acts as a catalyst, but the metal ion acting as a catalyst has a problem of becoming an impurity in the silicon layer in which crystallization is completed. Therefore, in the metal-induced crystallization method, the main problem is that doping the metal element on the semiconductor layer to be crystallized with a very weak dose.

In addition, according to the crystallization method, since the active layer is first patterned and then purified, there is a problem that the active layer is deformed according to the deformation of the substrate during the heating process.

The metal-induced crystallization method is a crystallization at a temperature of 200 ℃ ~ 700 ℃, the heating method used for crystallization is a method of heating in a furnace (furnace), a high speed annealing method using a UV lamp or the like as a heat source (RTA) And laser annealing methods may be applied, but among them, an RTA method that enables efficient crystallization at low cost is used.                     

The RTA method is a method of crystallizing a target while heating and cooling the target using an ultraviolet (UV) lamp or the like as a heat source. In this case, the amorphous silicon layer applied as the target has a characteristic of mainly absorbing light in a predetermined wavelength band among the ultraviolet wavelengths applied as the heat source, and thus, ultraviolet rays in the remaining wavelength band may be wasted.

In view of the above phenomenon, the present invention first forms an amorphous silicon layer and an insulating layer of a silicon nitride film having different ultraviolet absorption wavelength bands on an amorphous silicon layer to be crystallized, and then heats it with an ultraviolet lamp to crystallize the amorphous silicon layer. Promote

The silicon nitride film has an absorption wavelength different from that of amorphous silicon. In particular, the main absorption wavelength band of the silicon nitride film is shorter than the absorption wavelength band of amorphous silicon.

Therefore, after the silicon nitride film is formed on the silicon layer and irradiated with ultraviolet rays, the silicon nitride film and the amorphous silicon layer are heated at the same time, and the heated silicon nitride film can transfer heat containing to the contacting amorphous silicon layer to promote crystallization.

In addition, the silicon nitride film contains about 20% of hydrogen as an impurity. The hydrogen ions are hydrogenated to stabilize the silicon layer to be crystallized during the crystallization process, so that the silicon nitride film is formed on the active layer. In the case of post-crystallization, there is an advantage that the crystallization and hydrogenation can be performed at the same time.

Therefore, in order to crystallize the active layer, the present invention forms an amorphous silicon layer on the active layer and then warms it to proceed with metal induced crystallization.

Hereinafter, a metal induction crystallization method according to an embodiment of the present invention will be described in detail with reference to FIGS. 2A to 2E.

As shown in FIG. 2A, a buffer layer 202 is deposited on a transparent substrate 201 such as glass. The buffer layer 202 may be a silicon oxide film or a double layer of a silicon oxide film and a silicon nitride film, and may include plasma-enhanced chemical vapor deposition (PECVD), low-pressure chemical vapor deposition (LPCVD), atmosphere pressure chemical vapor deposition (APCVD), and ECR CVD. It may be formed using a deposition method such as (Electron Cyclotron Resonance CVD).

The buffer layer 202 prevents impurities contained in the substrate 201 from diffusing into the active layer during the crystallization process. In addition, some heat may be stored in the crystallization process to help crystallization.

After the buffer layer 202 is formed, an amorphous silicon layer is formed on the buffer layer 202. The amorphous silicon layer may be formed by depositing a thickness of 100 to 3,000 Å and preferably 500 to 1,000 Å using PECVD, LPCVD, or sputtering.

After forming an amorphous silicon layer, a mask is applied to the amorphous silicon layer and the active layer 203 is patterned as shown in FIG. 2A using a photolithography method.

Next, as shown in FIG. 2B, a gate insulating layer 204 and a gate electrode 205 are formed on the substrate 201 and the patterned active layer 203. The gate insulating layer 204 may be formed using a deposition method such as PECVD, LPCVD, APCVD, ECR CVD, and the like to form a silicon oxide (SiO 2), silicon nitride (SiN x), silicon oxynitride (SiO x Ny), or a composite layer thereof in a range of 300 to 3,000 Å. For example, it is formed by depositing a thickness of 500 to 1,000 Å, and the gate electrode is formed by sputtering, evaporation, PECVD, LPCVD, a conductive material such as a metal material or doped polysilicon on the gate insulating layer 204. It is formed by depositing and patterning the gate electrode layer to a thickness of 1,000 to 8,000 Å, preferably 2,000 to 4,000 Å, using methods such as APCVD, ECR CVD, and the like. The gate insulating layer 204 and the gate electrode 205 are formed by patterning using one mask.

Next, the source layer 210a and the drain region 210b are formed by doping impurities into the active layer 203 using the gate electrode 205 as a mask.

In the case of manufacturing an N-type TFT, dopants such as PH3, P, and As are doped using ion shower doping or ion implantation. In the case of manufacturing a P-MOS TFT, dopants such as B2H6, B, and BH3 are doped. .

Next, as shown in Fig. 2C, a metal film 206 such as nickel (Ni) is formed thin. Instead of nickel, palladium (Pd), titanium (Ti), silver (Ag), gold (Au), aluminum (Al), tin (Sn), antimony (Sb), copper (Cu), cobalt (Co), chromium Metals such as (Cr), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), cadmium (Cd) and platinum (Pt) may be used, and one or more of these metals may be used.

The thickness of the applied metal layer 206 may be arbitrarily selected within the limits necessary to induce crystallization of the amorphous silicon layer, but may be formed to a thickness of about 1 to 10,000 mW, preferably 10 to 200 mW.

After the metal film 206 is formed, a second insulating layer 207 including hydrogen ions is continuously formed. The second insulating layer 207 may be a silicon nitride film, and the silicon nitride film contains about 20% hydrogen ions.

After forming the second insulating layer 207 composed of the silicon nitride film containing the hydrogen ions, a process of crystallizing the active layer 203 is performed.

In this embodiment, for the crystallization, ultraviolet rays having a wavelength of 10 to 4000 GHz are used and crystallization is performed by a high speed annealing method (RTA).

The ultraviolet rays are irradiated on the laminated structure of the active layer 203 and the silicon nitride film 207, and both the silicon nitride film 207 and the active layer 203 are heated.

During the heating, the metal element of the metal film 206 formed on the active layer 203 penetrates into the active layer 203 to form metal induced crystallization to crystallize the active layer 203 and at the same time the silicon nitride film 207. The active layer 203 is hydrogenated by hydrogen ions contained therein.

Meanwhile, the silicon nitride film 207 heated by the ultraviolet lamp transfers absorbed heat into the active layer 203 to help crystallization.

By the above method, energy applied to crystallization can be saved, and deformation of the active layer due to heat can be suppressed. In addition, crystallization and hydrogenation of the active layer are also possible.

After the second insulating layer 207 is formed, a contact hole is formed by removing the interlayer insulating layer formed on the source and drain regions 210a and 210b, as shown in FIG. 2D. Source and drain electrodes 208a and 208b are connected to the active layer 203 through the active layer 203.

After forming the contact hole, a sputtering, evaporation, PECVD, LPCVD, APCVD metal material or conductive material such as doped polysilicon to be used as the source and drain electrodes 208a and 208b is formed on the interlayer insulating layer. And source and drain electrodes 208a and 208b as shown in FIG. 2D by forming and patterning using a method such as ECR CVD.

In particular, when the element formed by the above method is to be applied as the pixel portion thin film transistor of the liquid crystal display device, as shown in FIG. 2E, a protective film of an inorganic film or an organic film is formed on the source and drain electrodes 208a and 208b. 209 and a contact hole where a pixel electrode is connected to the drain electrode 208b on the passivation layer 209 and a pixel electrode material formed of indium tin oxide (ITO) or the like on the passivation layer 209. The pixel electrode 211 is formed by applying and patterning.

Through the above process, the thin film transistor of the pixel portion may be completed.

If the hydrogenation treatment is already performed in the crystallization process, but the hydrogenation treatment is considered insufficient, a protective film may be formed on the source and drain electrodes, and then hydrogenation treatment may be further performed. However, the hydrogenation can be completed even with limited heating and hydrogen ion implantation since the hydrogenation has already been performed.

As described above, in the method of forming a metal film on the active layer and immediately crystallizing the metal, the crystallization process and the hydrogenation process are performed by first forming an insulating layer containing hydrogen ions on the active layer and performing crystallization. The process can be carried out at the same time, which shortens the process. In addition, when metal-induced crystallization is performed by the RTA method, crystallization may be promoted due to the heat insulating effect and the heating effect of the insulating layer formed on the active layer.

Claims (10)

Forming an active layer on the substrate; Forming a gate electrode having a first insulating layer interposed on the active layer; Doping an impurity into the active layer using the gate electrode as a mask to form a source region and a drain region; Forming a metal film on the gate electrode including a source region and a drain region of the active layer; Forming a second insulating layer made of a silicon nitride film containing hydrogen ions on the metal film; A high temperature annealing method (RTA) using an ultraviolet lamp heats the second insulating layer formed on the active layer and the metal film to crystallize the active layer through metal induced crystallization and simultaneously contains hydrogen contained in the second insulating layer. Hydrogenating the active layer with ions; And And forming source and drain electrodes on the second insulating layer, wherein the second insulating layer heated by the ultraviolet lamp transfers absorbed heat through the lower metal film into the active layer to crystallize. Method of manufacturing a liquid crystal display device by metal-induced crystallization, characterized in that to promote. The method of claim 1, wherein forming the active layer Forming a semiconductor layer on a substrate and patterning the semiconductor layer comprising a method of manufacturing a liquid crystal display device by metal-induced crystallization characterized in that it comprises. The method of claim 1, wherein the forming of the gate electrode Forming a first insulating layer on the active layer; Forming a conductive layer on the first insulating layer; And And patterning the conductive layer and the first insulating layer at the same time. delete The method of claim 1, wherein the high-speed annealing method heats both the active layer and the second insulating layer by irradiating ultraviolet rays onto the laminated structure of the active layer and the second insulating layer using an ultraviolet lamp as a heat source. Method of manufacturing a liquid crystal display device by metal induced crystallization. The method of claim 1, wherein the second insulating layer is a silicon nitride film containing 20% of hydrogen ions. The method of claim 1, wherein the metal film is nickel (Ni), palladium (Pd), titanium (Ti), silver (Ag), gold (Au), aluminum (Al), tin (Sn), antimony (Sb), copper (Cu), cobalt (Co), chromium (Cr), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), cadmium (Cd), platinum (Pt) Liquid crystal display device manufacturing method. delete 6. The method of claim 5, wherein the second insulating layer and the active layer have different main absorption wavelength bands of ultraviolet light. The method of claim 1, wherein the method of manufacturing the liquid crystal display device further comprises forming a pixel electrode having an insulating layer interposed on the source and drain electrodes.

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