KR101060465B1 - Polysilicon liquid crystal display device manufacturing method and amorphous silicon crystallization method - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a polysilicon liquid crystal display device, and more particularly, to forming a high quality active layer through two crystallizations and manufacturing a polysilicon liquid crystal display device including the active layer. The present invention is a homogeneity by primary crystallization of amorphous silicon by the metal induced crystallization (MIC) method and alternating magnetic field crystallization (AMFC) method, and second crystallization of the crystallized amorphous silicon layer by excimer laser crystallization (ELC) method To form improved quality crystalline silicon. In addition, a polysilicon liquid crystal display device having high speed operation characteristics is manufactured using the crystallized silicon layer as an active layer.

MIC, AMFC, ELC, Polysilicon, Liquid Crystal Display

Description

Manufacturing Method of Polysilicon Liquid Crystal Display and Amorphous Silicon Crystallization Method {FABRICATION METHOD OF POLY SILICON LIQUID CRYSTAL DISPLAY DEVICE AND CRYSTALLIZATION METHOD OF AMORPHOUS SILICON}

1 is a graph showing the relationship between laser intensity and size of particles to be crystallized.

2 is a flowchart showing general MIC crystallization.

3A to 3J are flowcharts showing a method for manufacturing a polysilicon liquid crystal display device of the present invention.

***** Explanation of symbols for main parts of drawing *****

301; substrate 302: buffer layer

303: metal particle film 304: amorphous silicon layer

304a: Secondary Crystallized Amorphous Silicon Layer 304b: Secondary Crystallized Amorphous Silicon Layer

304c: active layer 305: first insulating layer

306; gate electrode 307: second insulating layer

The present invention relates to a method for manufacturing a polysilicon liquid crystal display device, and more particularly, to a method for manufacturing a polysilicon liquid crystal display device to which an alternating magnetic field crystallization (AMFC) method and an excimer laser crystallization (ELC) method are applied. will be.

Recently, the demand for low-temperature polysilicon thin film transistors as driving elements of display devices, such as active matrix liquid crystal display device (AMLCD) and active matrix organic light emitting diode (ALOLED), is increasing.

Thin film transistors (TFTs) are mainly used as switching elements for driving display devices, and amorphous silicon is mainly used as an active layer of the thin film transistors.

In particular, a liquid crystal display device using liquid crystals arranged in a certain direction according to an electric field as a component of a display device is employed as a switching element. Today, thin film transistors are employed to realize high response speed and low power consumption. Research into using polysilicon as an active layer is being actively conducted.

A process of manufacturing a liquid crystal display device using polysilicon as a channel is generally a process of forming amorphous silicon on a substrate such as glass by a plasma chemical vapor deposition method (PECVD) and crystallizing the deposited amorphous silicon. Proceed.

The method of crystallizing the amorphous silicon is a high temperature heating method for crystallization by heating and cooling the amorphous silicon for a long time in a high temperature furnace (funace), and a high-temperature laser energy is instantaneously irradiated and heated and cooled to crystallize An annealing method or the like is used.

Since the high temperature heating method of the crystallization method is because the amorphous silicon layer is heated at a high temperature above the glass transition temperature, it is not suitable for applying to a liquid crystal display device using glass or the like, so that various methods for crystallizing the amorphous silicon at low temperature are provided. Researched.

Among them, a crystallization method using a high energy laser has been studied. The laser crystallization method can be crystallized at a relatively low temperature and is suitable for the manufacture of a liquid crystal display device using glass as a substrate.

Laser crystallization methods include excimer laser crystallization (ELC) method using excimer laser, sequential lateral solidification method (SLS) where crystallization is sequentially performed horizontally, and metal induced crystallization method using metal metal as catalyst for crystallization ( metal induced crystallization (MIC) has been proposed.

The laser crystallization method is capable of crystallization at a lower temperature than the temperature at which the glass is melted. The principle of amorphous silicon crystallization by the laser crystallization method will be briefly described with reference to FIG. 1.

1 is a graph showing the relationship between the laser energy density irradiated to amorphous silicon and the size of particles to be crystallized.

As shown in the graph of FIG. 1, the crystallization of amorphous silicon may be divided into first and second regions according to the intensity of laser energy to be irradiated.                         

The first region is a partial melting region, in which laser energy is irradiated to the amorphous silicon layer at an intensity such that only the surface of the amorphous silicon layer is melted. In the first region, only the surface of the amorphous silicon is partially melted by laser irradiation, and small crystal particles are formed on the surface of the amorphous silicon layer through a solidification process.

The second region is a near-complete melting region, which irradiates the amorphous silicon with stronger laser energy than the first region so that the amorphous silicon layer is almost melted. However, although not completely melted, small nuclei that remain unmelted act as seeds and grow crystals, thereby obtaining large crystal grains compared to the first region. However, crystals growing in the second region are not uniform and the second region is considerably smaller in width than the first region.

The third region is a complete melting region, in which the intensity of the irradiated laser energy is higher than that of the second region to melt all of the amorphous silicon layer. The fully molten silicon layer undergoes cooling and undergoes solidification. The crystals formed are homogeneous nucleation, but the particles are very fine.

The laser intensity range used in the process of producing polycrystalline silicon is crystallized by adjusting the number of times of irradiation of the laser beam and the overlap ratio to obtain uniform and coarse crystals in the second region.

Usually, the crystallization method in which the intensity of the laser used while using the excimer laser as the laser light source is the laser intensity of the second region is called an excimer laser annealing (ELA).

In particular, the crystallization process by the ELA method is as follows. Strong laser energy is irradiated on the surface of the amorphous silicon film directly exposed to the laser beam, but relatively weak laser energy is irradiated on the lower part of the amorphous silicon film, so that the surface is completely melted, but the silicon in the lower part is not completely melted. The silicon, which is not completely melted, acts as a seed and crystallizes around the seed to grow crystals to form large and small crystals. The silicon to be crystallized forms a polycrystalline silicon layer bordering grains having the same crystal direction.

On the other hand, the sequential horizontal crystallization method (SLS) uses the laser energy of the third region in which the silicon layer is completely melted. In the SLS crystallization method, a part of the amorphous silicon is not covered by the mask and melted, and the other part is completely melted by irradiating with laser light, and then the molten silicon layer is grown by seeding the unmelted silicon during cooling. By doing this, there is an advantage that grains that grow large horizontally can be obtained. However, the SLS crystallization method has a disadvantage in that crystallization must be performed using a mask, and the distance of horizontal crystallization is extremely limited to 1 μm to 2 μm.

However, in the above-described ELC and SLS crystallization method, the crystallization proceeds at a lower temperature than the high temperature heating crystallization method, but the crystallization proceeds at a relatively high temperature of 700 ° C. to 800 ° C., thereby further lowering the crystallization temperature.

As a result, a MIC crystallization method is proposed in which crystallization proceeds below 500 ° C.

The MIC crystallization method is a crystallization method in which metals such as nickel, gold, aluminum, etc. are contacted with amorphous silicon, or these metals are injected into silicon, and the metal particles are used as catalysts for crystallization. It is a phenomenon that the phase change is induced to amorphous silicon by crystalline silicon by the element.

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 a leakage current occurs.

In recent years, 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, leading to crystallization of silicon to the side. MILC) method 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, the crystallization of silicon can be induced at relatively low temperatures of 300 ° C to 500 ° C, so that several substrates can be crystallized at the same time without damaging the substrate than crystallization using a blast furnace. have.

2A to 2D are cross-sectional views showing a prior art process of crystallizing a silicon layer constituting a TFT using MIC and MILC phenomenon.

As shown in FIG. 2A, 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, a gate insulating layer 13 and a gate electrode 14 are formed on the active layer 12 using a conventional method.

Next, as shown in FIG. 2B, the entire insulating substrate 10 is doped with a dopant using the gate electrode 14 as a mask to form a source region 15a, a channel region 15c, and a drain in the active layer 12. The area 15b is formed.

Then, as illustrated in FIG. 2C, the metal layer 16 is deposited thinly 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.

2D 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.                         

On the other hand, studies on lowering the crystallization temperature further based on the MIC crystallization method have been conducted, and a field enhanced metal induced cryatallization (FEMIC) method and an alternating magnetic field cryatallization (AMFC) method are proposed to promote MIC crystallization by applying an electric field. .

The FEMIC crystallization method is a method of promoting crystallization by applying metal particles such as nickel to amorphous silicon, and then forming an electrode on the amorphous silicon and heating in a furnace to form an electric field in the amorphous silicon layer through the electrode.

In the AMFC crystallization method, an alternating magnetic field is applied to amorphous silicon to form an induced electromotive force in the silicon layer to promote crystallization. By FEMIC and AMFC crystallization, the silicon layer may be crystallized at 500 ° C. or less and about 430 ° C.

Amorphous silicon has a very high resistivity value of 10 ⁶ Ω-cm ~ 10 ¹⁰ Ω-cm at room temperature. It is known to promote crystallization during FEMIC and AMFC crystallization.

As described above, the present invention proposes a new method for manufacturing a polysilicon liquid crystal display device by applying the AMFC and ELC crystallization method in manufacturing a polysilicon liquid crystal display device. In addition, through the AMFC and ELC crystallization method and to improve the crystallization at low temperature and to form a high-quality crystalline silicon.

In particular, an object of the present invention is to manufacture a liquid crystal display without additional process by performing crystallization by AMFC in the dehydrogenation process before crystallization which is essentially used in the conventional polysilicon liquid crystal display device manufacturing method.

Polysilicon liquid crystal display device manufacturing method of the present invention comprises the steps of forming a metal particle film on the substrate; Forming an amorphous silicon layer on the metal particle film; Applying an alternating magnetic field perpendicular to the amorphous silicon layer at a temperature of 400 ° C. to 500 ° C. to form a first crystallized silicon layer; Crystallizing the first crystallized silicon layer through irradiation with an excimer laser to form a second crystallized silicon layer; Patterning the second crystallized silicon layer to form an active layer; Forming a first insulating layer on the active layer; Forming the gate electrode on the first insulating layer; And forming a source and a drain electrode on the gate electrode with a second insulating layer interposed therebetween, and forming a pixel electrode on the source and drain electrode with a third insulating layer interposed therebetween. .

Hereinafter, a method of manufacturing a polysilicon liquid crystal display device according to an exemplary embodiment of the present invention will be described with reference to FIGS. 3A to 3J.

As shown in Fig. 3A, a buffer layer 302 made of a silicon oxide film is formed on a transparent substrate 301 such as glass. The buffer layer 302 prevents impurity ions contained in the substrate 301 from penetrating into the silicon layer crystallized by diffusion in the process of crystallizing amorphous silicon that is deposited and crystallized on the substrate 301 in the future. It can be formed to a predetermined thickness by the plasma chemical vapor deposition method (PECVD) method.

Subsequently, a metal particle film 303 is formed on the buffer layer 302. The metal particle film is formed by dispersing or depositing a very small amount of a metal such as nickel (Ni) on the buffer layer 302 and serves as a catalyst for promoting crystallization of amorphous silicon.

The concentration of the metal particle film 303 to be applied may be about 1 × 10 ¹³ atoms / cm 2 to 1 × 10 ¹⁵ atoms / cm 2. Instead of nickel, palladium (Pd), titanium (Ti), silver (Ag), gold (Au), aluminum (Al), tin (Sn), antimony (Sb), and copper (Cu) may be applied. , Cobalt (Co), chromium (Cr), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), cadmium (Cd), platinum (Pt) and the like.

After the metal particle film 303 is formed, as shown in FIG. 3B, an amorphous silicon layer 304 is formed on the metal particle film 303 by PECVD.

Next, as shown in FIG. 3C, crystallization of amorphous silicon formed on the substrate 301 is performed.

Crystallization of the amorphous silicon layer 304 is formed by simultaneously performing metal induced crystallization (MIC) and alternating magnetic field crystallization (AMFC).

First, an alternating magnetic field acting perpendicular to the amorphous silicon layer 304 is applied. The alternating magnetic field is applied in a chamber heated to a temperature of about 400 ° C to 500 ° C. In this case, an induced electromotive force is generated in the amorphous silicon by the magnetic field, and the value of E = I ² × R is reduced by Ohm's law. Joule heat is generated to promote crystallization.

In addition, the crystallization in the above is heated while the metal particle film is formed and crystallization proceeds, so that the metal induced crystallization is also performed at the same time. That is, the metal particle film 303 formed on the buffer layer 302 is activated while being heated to crystallize amorphous silicon, and serves as a catalyst.

It is known that the metal particle film, particularly nickel metal, forms nickel silicide and forms silicide during MIC crystallization, and then promotes crystallization while forming silicide while moving to another region. In particular, the nickel silicide forms a diamond structure like silicon crystals, which contribute to crystallization of amorphous silicon.

In particular, since the metal particle film 303 is formed on the bottom of the amorphous silicon layer 304 in the MIC crystallization process, crystallization proceeds from the bottom of the amorphous silicon.

While the MIC crystallization is in progress, AMFC crystallization by alternating magnetic field is performed at the same time, so that the crystallization rate can be further improved and crystallization can be carried out while keeping the crystallization temperature low.

On the other hand, since the crystallization process is made in a heated state at 400 ℃ ~ 500 ℃, a dehydrogenation process for removing the hydrogen ions contained in the amorphous silicon layer 304 is also performed at the same time. In other words, a conventional dehydrogenation process is performed to excimer laser crystallization of amorphous silicon. In the laser crystallization process, hydrophobic ions contained in the amorphous silicon are exploded by the high energy laser to damage the crystalline silicon and damage the crystalline silicon. Degrades the quality.

Therefore, the dehydrogenation process is essentially performed. In the present invention, the dehydrogenation process is automatically performed in the MIC crystallization and AMFC crystallization process.

Through the process, the amorphous silicon layer 304 is changed into a crystalline silicon layer 304a. However, the crystallized silicon layer 304a has a problem that the quality of crystallization is somewhat deteriorated.

What we want to get through crystallization is to get large grains with the smallest possible grain boundaries. Grain boundaries are known as barriers to the movement of electrons or holes, minimizing the grain boundaries through crystallization of amorphous silicon. Therefore, it is most desirable to grow complete single crystals, but growing single crystals is technically and equipment-limited, and methods for obtaining polycrystalline silicon with as large grains as possible are developed.

The present invention crystallizes once again the crystalline silicon formed through the MIC and AMFC crystallization.

As the second crystallization method, an excimer laser crystallization method is performed, and the excimer laser crystallization method is a crystallization at a temperature at which near complete melting of silicon is performed.

Therefore, the excimer laser crystallization method does not completely melt the silicon, in particular, the silicon layer on the upper surface directly irradiated with the laser is completely melted and not completely melted on the silicon layer below which is not directly irradiated with laser energy. The remaining silicon particles are present. The silicon particles that do not melt act as seeds of crystallization during cooling to achieve crystallization.

In the present invention, crystallization is relatively easy because the silicon layer 304a that has already been crystallized through MIC and AMFC crystallization is relatively easy, and in particular, crystallization is promoted by the metal particle film 303 formed at the bottom of the amorphous silicon layer 304. Therefore, the bottom of the amorphous silicon layer 304 is crystallized better than the top.

Therefore, when the excimer laser crystallization proceeds to the crystallized silicon layer 304a, the crystallization quality which can act as a seed during the excimer laser crystallization may remain in the non-melt state where the crystallization proceeds relatively well.

That is, crystallization is usually crystallized depending on the uniformity of the seed, and the closer the seed is to the single crystal, the higher quality crystals can be grown.

Therefore, the present invention can form crystalline silicon 304b of higher quality than crystallizing amorphous silicon by crystallizing once again crystallized through MIC and AMFC crystallization once more.

Subsequently, a process of patterning the crystalline silicon layer 304b crystallized by the excimer laser crystallization method into an active layer is performed.

First, as shown in FIG. 3F, the active layer 304c is formed of the crystalline silicon layer 304b using a photolithography process.

That is, applying a photoresist film on the crystalline silicon layer 304c, arranging and exposing a mask including an active pattern on the photoresist film, developing the photoresist film to form a photoresist pattern, the photoresist pattern Is applied as a mask to form the active layer 304c by etching the crystalline silicon layer, stripping the photoresist pattern, and cleaning.

Next, as illustrated in FIG. 3G, the first insulating layer 305 and the conductive metal film (not shown) are sequentially deposited on the entire surface of the substrate 301 on which the active layer 304c is formed.

The first insulating layer 305 may be a silicon oxide film or a silicon nitride film as a gate insulating layer, and the metal film may be a gate electrode, and a conductive metal film may be used.

Next, as shown in FIG. 3H, the conductive metal film is patterned using a photolithography process to form the gate electrode 306 with the first insulating film 305 interposed therebetween.

Subsequently, source / drain regions 330a and 330b are formed by implanting a high concentration of impurity ions of p + or n + into a predetermined region of the active layer 304c by applying the gate electrode 306 as a mask. The source / drain regions 330a and 330b are formed for ohmic contact with the source / drain electrodes.

Next, as shown in FIG. 3I, the second insulating film 307 is deposited as an interlayer insulating film on the entire surface of the substrate 301 on which the gate electrode 306 is formed, and then the first insulating film 305 is formed through a photolithography process. The second insulating layer 307 is partially removed to form the first contact hole 320a and the second contact hole 320b for electrical connection between the source / drain regions 330a and 330b and the source / drain electrode.

Thereafter, as illustrated in FIG. 3J, a source electrode connected to the source region 330a through the first contact hole 320a using a photolithography process after depositing a conductive metal on the entire surface of the substrate 301. 308a is formed and a drain electrode 308b connected to the drain region 330b is formed through the second contact hole 320b. At this time, a portion of the conductive metal constituting the source electrode 308a is extended to form a data line (not shown).

Next, after depositing a third insulating film 309, which is an organic insulating film such as acrylic, on the entire surface of the substrate 301, a third contact hole exposing a part of the drain electrode 308b using a photolithography process ( 320c).

Lastly, a transparent conductive material such as indium tin oxide (ITO) is deposited on the entire surface of the substrate 301 on which the third insulating layer 320c is formed, and then the third contact hole is formed using a photolithography process. The pixel electrode 310 connected to the drain electrode 308c is formed through 320b.

As a result of this process, a polysilicon liquid crystal display device including an active layer in which primary crystallization is performed by MIC and AMFC crystallization and secondary crystallization is performed by ELC crystallization is completed.

However, the present invention is not limited to the above embodiments and includes various primary crystallization steps of amorphous silicon formed by MIC and AMFC crystallization and secondary crystallization steps of crystallizing the primary crystallized silicon layer by an excimer laser crystallization method. A polysilicon liquid crystal display device can be manufactured by the method.

As described above, the first crystallization may be performed by MIC and AMFC crystallization and the second crystallization may be obtained by ELC crystallization to obtain high quality crystalline silicon. In addition, by performing crystallization from the bottom of the amorphous silicon crystallized in the MIC crystallization process, it is possible to improve the regularity of crystals grown during ELC crystallization.

In addition, since the dehydrogenation process of the amorphous silicon can be performed simultaneously in the MIC and AMFC crystallization process, it is possible to manufacture a high quality polysilicon liquid crystal display without additional process.

Claims (17)

Forming a metal particle film on the substrate; Forming an amorphous silicon layer on the metal particle film; Applying an alternating magnetic field perpendicular to the amorphous silicon layer at a temperature of 400 ° C. to 500 ° C. to form a first crystallized silicon layer; Crystallizing the first crystallized silicon layer through irradiation with an excimer laser to form a second crystallized silicon layer; Patterning the second crystallized silicon layer to form an active layer; Forming a first insulating layer on the active layer; Forming the gate electrode on the first insulating layer; Forming a source and a drain electrode on the gate electrode with a second insulating layer interposed therebetween; And forming a pixel electrode on the source and drain electrodes with a third insulating layer interposed therebetween. The method of manufacturing a polysilicon liquid crystal display device according to claim 1, wherein the metal particle film is a nickel particle film and is doped at a concentration of 1 x 10 ¹³ atoms / cm 2 to 1 x 10 ¹⁵ atoms / cm 2. delete The method of claim 1, wherein the forming of the second crystallized silicon layer by crystallizing the first crystallized silicon layer through irradiation with an excimer laser is performed by seeding the crystalline material of the bottom of the first crystallized silicon layer. Polysilicon liquid crystal display device manufacturing method characterized in that made. The method of claim 1, wherein the metal particle film is palladium (Pd), titanium (Ti), silver (Ag), gold (Au), aluminum (Al), tin (Sn), antimony (Sb), copper (Cu), A method for manufacturing a polysilicon liquid crystal display device, characterized in that selected from cobalt (Co), chromium (Cr), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), cadmium (Cd), platinum (Pt). The method of claim 1, wherein the dehydrogenation of the amorphous silicon layer is performed simultaneously in the step of applying an alternating magnetic field perpendicular to the amorphous silicon layer at a temperature of 400 ° C to 500 ° C to form a first crystallized silicon layer. Polysilicon liquid crystal display device manufacturing method characterized in that. The method of manufacturing a polysilicon liquid crystal display device according to claim 1, further comprising forming a buffer layer comprising a silicon oxide film on the substrate. The method of claim 1, wherein the source and drain electrode forming step Forming a second insulating layer on the gate electrode; Forming a contact hole exposing the active layer; Forming a source and a drain region in the active layer; and And forming source and drain electrodes connected to the source and drain regions through the contact hole. The method of claim 8, wherein the source and drain region forming step And implanting high concentration impurity ions into the active layer through the contact hole. The method of claim 8, wherein the forming of the contact hole is performed. And removing the first insulating layer and the second insulating layer over the source and drain regions, thereby exposing the active layer. The method of claim 1, wherein the forming of the pixel electrode is performed. Forming a third insulating layer on the source and drain electrodes; Forming a contact hole exposing the drain electrode on the third insulating layer, and forming a pixel electrode connected to the drain electrode through the contact hole. Way. Forming a metal particle film on the substrate; Forming an amorphous silicon layer on the metal particle film; Applying an alternating magnetic field perpendicular to the amorphous silicon layer at a temperature of 400 ° C. to 500 ° C. to form a first crystallized silicon layer; And, And crystallizing the first crystallized silicon layer through laser irradiation. delete delete The amorphous silicon crystallization method of claim 12, wherein the second crystallization is performed by an excimer laser crystallization method. 13. The amorphous silicon crystallization method according to claim 12, wherein the metal particle film is made of nickel and is doped at a concentration of 1 x 10 ¹³ atoms / cm 2 to 1 x 10 ¹⁵ atoms / cm 2. 13. The amorphous silicon crystallization method of claim 12, wherein dehydrogenation of the amorphous silicon layer occurs in the first crystallization step.

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