KR20040103521A - method for forming of TFT - Google Patents

Abstract

PURPOSE: A method for forming a TFT(Thin Film Transistor) is provided to promote creation of nuclei by using a catalyst metal as a seed, thereby forming a micro crystalline layer, as an ohmic contact layer and simultaneously reducing a contact resistance between the ohmic contact layer and a semiconductor layer. CONSTITUTION: A source electrode(32) and a drain electrode(33) are formed on a transparent substrate(31) with a constant distance. A catalyst metal is formed on the transparent substrate including the source and drain electrodes. An ohmic contact layer(35) is formed on the transparent substrate by using the catalyst metal as a seed. Then the ohmic contact layer is selectively removed, thereby forming a semiconductor layer on the entire surface of the substrate including the ohmic contact layer. An active layer is formed by selectively removing the semiconductor layer. A gate insulation film(37) is formed on the entire surface of the substrate including the active layer. A gate electrode(38a) is formed on the gate insulation film.

Description

Method for forming of TFT

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a liquid crystal display device, and more particularly, to a method of forming a thin film transistor suitable for reducing contact resistance between an ohmic contact layer and a semiconductor layer.

As the information society develops, the demand for display devices is increasing in various forms, and in recent years, liquid crystal display devices (LCDs), plasma display panels (PDPs), electro luminescent displays (ELD), and vacuum fluorescent (VFD) Various flat panel display devices such as displays have been studied, and some of them are already used as display devices in various devices.

Among them, LCD is the most widely used as the substitute for CRT (Cathode Ray Tube) for mobile image display device because of its excellent image quality, light weight, thinness, and low power consumption. In addition to the use of the present invention has been developed in various ways such as a monitor of a television and computer for receiving and displaying broadcast signals.

A general liquid crystal display device may be largely divided into a liquid crystal panel displaying an image and a driving unit for applying a driving signal to the liquid crystal panel, wherein the liquid crystal panel includes first and second glass substrates bonded to each other with a predetermined space; It consists of a liquid crystal layer injected between the said 1st, 2nd glass substrate.

Here, the first glass substrate (TFT array substrate) has a plurality of gate lines arranged in one direction at regular intervals, a plurality of data lines arranged at regular intervals in a direction perpendicular to the gate lines, A plurality of pixel electrodes formed in a matrix form in each pixel region defined by crossing a gate line and a data line, and a plurality of thin film transistors switched by signals of the gate line to transfer the signal of the data line to each pixel electrode. Is formed.

In the second glass substrate (color filter array substrate), a light shielding layer for blocking light in portions other than the pixel region, an R, G, and B color filter layer for expressing color colors are common to implement an image. An electrode is formed.

The first and second substrates are bonded to each other by a seal material having a predetermined space by a spacer and having a liquid crystal injection hole to inject liquid crystal between the two substrates.

In the meantime, the thin film transistor uses a semiconductor film as an active layer. The semiconductor film is formed of amorphous silicon or crystalline silicon. The semiconductor film formed of amorphous silicon, which can be produced relatively easily by vapor deposition at low temperature and is suitable for mass production, was most widely used.

However, the thin film transistor including the semiconductor film formed of the crystalline silicon has sufficient driving capability for a large current to realize high speed operation, and allows the peripheral driving circuit of the LCD to be formed integrally with the display portion on the same substrate. For these reasons, thin film transistors containing crystalline silicon are attracting attention today.

1 is a plan view illustrating a general liquid crystal display device.

As shown in FIG. 1, a plurality of gate lines 11 are arranged in one direction at regular intervals to define the pixel region P on the lower substrate 10, and are perpendicular to the gate lines 11. The plurality of data lines 12 are arranged at regular intervals in the direction.

Each pixel region P defined by crossing the gate line 11 and the data line 12 is switched by a pixel electrode 16 formed in a matrix form and a signal of the gate line 11, A plurality of thin film transistors T for transmitting a signal of the data line 12 to the pixel electrodes 16 are formed.

The thin film transistor T may include a gate electrode 13 protruding from the gate line 11, a gate insulating film (not shown) formed on an entire surface thereof, and a gate above the gate electrode 13. A semiconductor layer 14 formed on the insulating film, a source electrode 15a protruding from the data line 12, and a drain electrode 15b formed at regular intervals on the source electrode 15a. Consists of.

The drain electrode 15b is electrically connected to the pixel electrode 16 through the contact hole 17.

Meanwhile, the lower substrate 10 configured as described above has a predetermined space and is bonded to the upper substrate (not shown).

In this case, the upper substrate has an opening corresponding to the pixel region P formed in the lower substrate 10, and serves as a light blocking layer, and a red / green / color for implementing color. In addition to the blue (R / G / B) color filter layer and the pixel electrode (reflection electrode) 16, a common electrode for driving a liquid crystal is included.

The lower and upper substrates 10 and 10 have a predetermined space by a spacer and liquid crystal is injected between two substrates bonded by a seal material having a liquid crystal injection hole.

Hereinafter, a method of forming a conventional thin film transistor will be described with reference to the accompanying drawings.

2A through 2E are cross-sectional views illustrating a method of forming a conventional thin film transistor.

As shown in FIG. 2A, a metal film is deposited on the glass substrate 21, and selectively removed from the metal film through a photo and etching process, so that the source electrode 22 has a predetermined gap on the glass substrate 21. And a drain electrode 23 are formed.

Here, the source electrode 22 and the drain electrode 23 use a conductive metal film such as aluminum (Al), chromium (Cr), molybdenum (Mo), or the like.

As shown in FIG. 2B, an ohmic contact layer 24 made of amorphous silicon doped on the entire surface of the glass substrate 21 including the source electrode 22 and the drain electrode 23 is formed to a thickness of about 300 GPa. .

As illustrated in FIG. 2C, the ohmic contact layer 24 may be selectively removed and separated through photo and etching processes, and microcrystalline silicon may be disposed on the entire surface of the insulating substrate 21 including the ohmic contact layer 24. micro crystalline) layer 25 is formed.

As shown in FIG. 2D, a gate insulating film 26 is formed on the microcrystalline silicon layer 25, and a metal film 27 is deposited on the gate insulating film 26.

Here, the metal film 27 is selected from metals made of Al, Al-Pd, Al-Si, Al-Si-Ti, Al-Si-Cu, Al alloys, etc., and is 200 to 200 by sputtering or chemical vapor deposition. Deposit at a thickness of 4000 mm 3.

As shown in FIG. 2E, the metal layer 27 is selectively removed through photo and etching processes to form the gate electrode 27a.

Subsequently, the gate insulating layer 26 and the microcrystalline silicon layer may have a width wider than that of the gate electrode 27a and may expose portions of the surfaces of the source electrode 22 and the drain electrode 23 through photo and etching processes. Optionally remove 25).

Here, both ends of the gate electrode 27a overlap a predetermined portion of the source electrode 22 and the drain electrode 23.

However, in the conventional method of forming the thin film transistor as described above, there are the following problems.

First, in manufacturing TFT using microcrystalline silicon, the contact resistance of the ohmic contact layer and the microcrystalline silicon layer (semiconductor layer) increases, resulting in deterioration of the device.

Second, since the microcrystalline silicon layer usually grows from several hundreds of microseconds or more, it is difficult to grow a microcrystalline silicon layer having a desired thickness on an ohmic contact layer that usually uses about 300 microns or less.

The present invention has been made to solve the above-mentioned conventional problems, and promotes nucleation by using a catalyst metal as a seed to form a microcrystalline silicon layer as an ohmic contact layer and at the same time between the ohmic contact layer and the semiconductor layer. It is an object of the present invention to provide a method of forming a thin film transistor to reduce the contact resistance of the transistor.

1 is a plan view showing a general liquid crystal display device

2A through 2E are cross-sectional views illustrating a method of forming a conventional thin film transistor.

3A to 3E are cross-sectional views illustrating a method of forming a thin film transistor according to a first embodiment of the present invention.

4A through 4E are cross-sectional views illustrating a method of forming a thin film transistor according to a second embodiment of the present invention.

5A to 5F are cross-sectional views illustrating a method of forming a thin film transistor according to a third embodiment of the present invention.

Explanation of symbols for the main parts of the drawings

31 glass substrate 32 source electrode

33: drain electrode 34: catalytic metal

35: ohmic contact layer 36: semiconductor layer

37 gate insulating film 38a gate electrode

A method of forming a thin film transistor according to a first embodiment of the present invention for achieving the above object is to form a source electrode and a drain electrode having a predetermined interval on a transparent substrate, the transparent including the source electrode and the drain electrode Forming a catalyst metal on a substrate, forming and selectively removing the ohmic contact layer using the catalyst metal as a seed on the transparent substrate, and forming a semiconductor layer on the entire surface including the ohmic contact layer And selectively removing the semiconductor layer to form an active layer, forming a gate insulating film on the entire surface including the active layer, and forming a gate electrode on the gate insulating film. .

Here, the catalyst metal is nickel (Ni), iron (Fe), cobalt (Co), chromium (Cr), palladium (Pd), platinum (Pt), tin (Sn), indium (In), aluminum (Al) At least one material selected from the group consisting of gold (Au), silver (Ag), antimony (Sb), copper (Cu), arsenic (As) and phosphorus (P).

The source electrode and the drain electrode may be formed of a conductive metal film such as aluminum (Al), chromium (Cr), or molybdenum (Mo).

In addition, the gate electrode is selected from a metal made of Al, Al-Pd, Al-Si, Al-Si-Ti, Al-Si-Cu, Al alloy, or the like.

In addition, the semiconductor layer is formed of an amorphous silicon layer or a polycrystalline silicon layer.

A method of forming a thin film transistor according to a second embodiment of the present invention comprises the steps of forming a gate electrode on a transparent substrate, forming a gate insulating film on the entire surface of the transparent substrate including the gate electrode, a semiconductor layer on the gate insulating film Forming a catalyst metal on the semiconductor layer, forming an ohmic contact layer on the gate insulating layer using the catalyst metal as a seed, and selectively removing the ohmic contact layer and the semiconductor layer. And forming a source electrode and a drain electrode on the ohmic contact layer.

Here, the semiconductor layer is formed of an amorphous silicon layer or a polycrystalline silicon layer.

A method of forming a thin film transistor according to a third embodiment of the present invention comprises the steps of forming a gate electrode on a transparent substrate, forming a gate insulating film on the entire surface of the transparent substrate including the gate electrode, a semiconductor layer on the gate insulating film Forming a catalyst metal on the semiconductor layer; forming an ohmic contact layer on the gate insulating layer using the catalyst metal as a seed; forming a metal film on the ohmic contact layer; Applying photoresist on the film, diffractive exposure and developing to form photoresist patterns having different thicknesses, selectively removing the metal layer, ohmic contact layer, and semiconductor layer using the photoresist pattern as a mask; Ashing the photoresist pattern to selectively select the photoresist pattern of the portion having a thin thickness And removing the metal layer and the ohmic contact layer by using the ashed photoresist pattern as a mask to form a source electrode and a drain electrode.

Here, the semiconductor layer is formed of an amorphous silicon layer or a polycrystalline silicon layer.

Hereinafter, a method of forming a thin film transistor according to the present invention will be described with reference to the accompanying drawings.

3A to 3E are cross-sectional views illustrating a method of forming a thin film transistor according to a first embodiment of the present invention.

As shown in FIG. 3A, a metal film is deposited on the transparent glass substrate 31, and selectively removed from the metal film through a photo and etching process, so that the source electrode 32 has a predetermined gap on the glass substrate 31. ) And the drain electrode 33 are formed.

Here, the source electrode 32 and the drain electrode 33 use a conductive metal film such as aluminum (Al), chromium (Cr), and molybdenum (Mo).

As shown in FIG. 3B, the catalyst metal 34 is formed on the glass substrate 31 on which the source electrode 32 and the drain electrode 33 are formed.

Here, the catalyst metal 34 is nickel (Ni), iron (Fe), cobalt (Co), chromium (Cr), palladium (Pd), platinum (Pt), tin (Sn), indium (In), aluminum At least one material selected from the group consisting of (Al), gold (Au), silver (Ag), antimony (Sb), copper (Cu), arsenic (As) and phosphorus (P) is used.

As shown in FIG. 3C, the ohmic contact layer 35 is formed by using the catalyst metal 34 as a seed on the glass substrate 31 on which the catalyst metal 34 is formed, and through the photo and etching processes. After the ohmic contact layer 35 is selectively removed, the semiconductor layer 36 is formed on the entire surface including the ohmic contact layer 35.

Here, when the ohmic contact layer 35 is formed, the catalyst metal 34 acts as a seed to promote nucleation to initially form a microcrystalline silicon layer and simultaneously crystallize the microcrystalline silicon layer. It can improve sex.

In addition, the semiconductor layer 36 may use an amorphous silicon layer or a polycrystalline silicon layer.

As shown in FIG. 3D, a gate insulating film 37 is formed on the semiconductor layer 36, and a metal film 38 is deposited on the gate insulating film 37.

Here, the metal film 38 is selected from a metal made of Al, Al-Pd, Al-Si, Al-Si-Ti, Al-Si-Cu, Al alloy, etc., and has a thickness of 200 to 4000 kPa by the sputtering method. Deposit.

As shown in FIG. 3E, the metal film 38 is selectively removed to form a gate electrode 38a, and the source electrode 32 and the drain electrode 33 have a width wider than that of the gate electrode 38a. ), The gate insulating layer 37 and the semiconductor layer 36 are selectively removed so as to expose a predetermined portion of the surface thereof.

Here, both ends of the gate electrode 38a overlap a predetermined portion of the source electrode 32 and the drain electrode 33.

4A to 4E are cross-sectional views illustrating a method of forming a thin film transistor according to a second embodiment of the present invention.

As shown in FIG. 4A, a sputtering method is selected from a metal made of Al, Al-Pd, Al-Si, Al-Si-Ti, Al-Si-Cu, Al alloy, or the like on the transparent glass substrate 41. Thereby depositing a metal film at a thickness of 200 to 4000 kPa.

Subsequently, the metal film is selectively etched through a photo and etching process to form a gate electrode 42 on the glass substrate 41.

Here, when the gate electrode 42 is a metal capable of anodizing, the gate electrode 42 may be anodized to prevent hillock.

As shown in FIG. 4B, a gate insulating film 43 made of a silicon nitride film or a silicon oxide film is formed on the entire surface of the glass substrate 41 including the gate electrode 42.

Subsequently, a semiconductor layer (amorphous silicon layer or polycrystalline silicon layer) 44 is formed on the gate insulating layer 43, and a catalyst metal 45 is formed on the semiconductor layer 44.

Here, the catalyst metal 45 is nickel (Ni), iron (Fe), cobalt (Co), chromium (Cr), palladium (Pd), platinum (Pt), tin (Sn), indium (In), aluminum At least one material selected from the group consisting of (Al), gold (Au), silver (Ag), antimony (Sb), copper (Cu), arsenic (As) and phosphorus (P) is used.

As shown in FIG. 4C, the ohmic contact layer 46 made of a microcrystalline silicon layer is formed on the amorphous silicon layer 44 using the catalyst metal 44 as a seed.

When the ohmic contact layer 46 is formed, the catalyst metal 44 may act as a seed to promote nucleation to form a microcrystalline silicon layer initially.

As shown in FIG. 4D, the ohmic contact layer 46 and the semiconductor layer 44 are selectively removed through photo and etching processes to form an active layer.

Here, the selectively removed active layer is formed to cover the gate electrode 42 while covering the gate electrode 42.

As shown in FIG. 4E, a metal film is deposited on the entire surface of the glass substrate 41, and the source film 47 and the drain electrode 48 are electrically separated by selectively removing the metal film through a photo and etching process. To form.

Here, the source electrode 47 and the drain electrode 48 use a conductive metal film such as aluminum (Al), chromium (Cr), molybdenum (Mo), or the like.

5A to 5F are cross-sectional views illustrating a method of forming a thin film transistor according to a third embodiment of the present invention.

As shown in Fig. 5A, a sputtering method is selected from a metal made of Al, Al-Pd, Al-Si, Al-Si-Ti, Al-Si-Cu, Al alloy, or the like on the transparent glass substrate 51. Thereby depositing a metal film at a thickness of 200 to 4000 kPa.

Subsequently, the metal film is selectively etched through a photo and etching process to form a gate electrode 52 on the glass substrate 51.

Here, when the gate electrode 52 is an anodized metal, the gate electrode 52 may be anodized to prevent hillock.

As shown in FIG. 5B, a gate insulating film 53 made of a silicon nitride film or a silicon oxide film is formed on the entire surface of the glass substrate 51 including the gate electrode 52.

Subsequently, a semiconductor layer (amorphous silicon layer or polycrystalline silicon layer) 54 is deposited on the gate insulating layer 53, and a catalyst metal 55 is formed on the semiconductor layer 54.

Here, the catalyst metal 55 is nickel (Ni), iron (Fe), cobalt (Co), chromium (Cr), palladium (Pd), platinum (Pt), tin (Sn), indium (In), aluminum At least one material selected from the group consisting of (Al), gold (Au), silver (Ag), antimony (Sb), copper (Cu), arsenic (As) and phosphorus (P) is used.

As shown in FIG. 5C, an ohmic contact layer 56 made of a microcrystalline silicon layer is formed on the amorphous silicon layer 54 using the catalyst metal 55 as a seed.

Here, when the ohmic contact layer 56 forms a microcrystalline silicon layer, the catalyst metal 55 may act as a seed to promote nucleation to form a microcrystalline silicon layer initially.

As shown in FIG. 5D, a metal film 57 is formed on the ohmic contact layer 56.

The metal film 57 may be formed of a conductive metal film such as aluminum (Al), chromium (Cr), or molybdenum (Mo).

Subsequently, after the photoresist is applied onto the metal film 57, the photoresist pattern 58 is formed by an exposure and development process using a mask (half-tone mask). In this case, the mask (half-tone mask) is composed of a blocking region that completely blocks the light, a transmission region through which light is transmitted, and a slit region where only a predetermined amount of light is irradiated.

Therefore, the developed photoresist pattern 58 is formed to have a different thickness.

As shown in FIG. 5E, the metal layer 57, the ohmic contact layer 56, and the semiconductor layer 54 are removed by wet or dry etching using the photoresist pattern 58 as a mask.

As shown in FIG. 5F, the photoresist pattern 58 is ashed to remove portions of the photoresist pattern 58 having a relatively thin thickness.

In this case, the photoresist pattern 58 is thinner as a whole.

Subsequently, the metal layer 57 and the ohmic contact layer 56 corresponding to the channel region of the thin film transistor are etched using the ashed photoresist pattern 58 as a mask, so that the source electrode 57a and the drain electrode ( 57b).

Since the drawings are not shown in the drawings, the photoresist pattern 58 is peeled off.

On the other hand, the present invention described above is not limited to the above-described embodiment and the accompanying drawings, it is possible that various substitutions, modifications and changes within the scope without departing from the technical spirit of the present invention. It will be apparent to those of ordinary skill in Esau.

As described above, the method of forming the thin film transistor according to the present invention has the following effects.

First, a microcrystalline silicon layer may be initially formed by forming a microcrystalline silicon layer for an ohmic contact layer using a catalyst metal as a seed.

Second, the contact resistance between the ohmic contact layer and the active layer can be reduced.

Claims (10)

Forming a source electrode and a drain electrode at regular intervals on the transparent substrate; Forming a catalyst metal on the transparent substrate including the source electrode and the drain electrode; Forming and selectively removing the ohmic contact layer using the catalyst metal as a seed on the transparent substrate; Forming a semiconductor layer on an entire surface including the ohmic contact layer; Selectively removing the semiconductor layer to form an active layer; Forming a gate insulating film on the entire surface including the active layer; And forming a gate electrode on the gate insulating film. The method of claim 1, wherein the catalyst metal is nickel (Ni), iron (Fe), cobalt (Co), chromium (Cr), palladium (Pd), platinum (Pt), tin (Sn), indium (In), Thin film using at least one material selected from the group consisting of aluminum (Al), gold (Au), silver (Ag), antimony (Sb), copper (Cu), arsenic (As) and phosphorus (P) Method of forming a transistor. The method of claim 1, wherein the source electrode and the drain electrode are formed of a conductive metal film such as aluminum (Al), chromium (Cr), or molybdenum (Mo). The thin film transistor of claim 1, wherein the gate electrode is selected from a metal made of Al, Al-Pd, Al-Si, Al-Si-Ti, Al-Si-Cu, Al alloy, or the like. Formation method. The method of claim 1, wherein the semiconductor layer is formed of an amorphous silicon layer or a polycrystalline silicon layer. The method of claim 1, wherein the ohmic contact layer is a microcrystalline silicon layer. Forming a gate electrode on the transparent substrate; Forming a gate insulating film on an entire surface of the transparent substrate including the gate electrode; Forming a semiconductor layer on the gate insulating film; Forming a catalyst metal on the semiconductor layer; Forming an ohmic contact layer on the gate insulating layer using the catalyst metal as a seed; Selectively removing the ohmic contact layer and the semiconductor layer; And forming a source electrode and a drain electrode on the ohmic contact layer. 8. The method of claim 7, wherein the semiconductor layer is formed of an amorphous silicon layer or a polycrystalline silicon layer. Forming a gate electrode on the transparent substrate; Forming a gate insulating film on an entire surface of the transparent substrate including the gate electrode; Forming a semiconductor layer on the gate insulating film; Forming a catalyst metal on the semiconductor layer; Forming an ohmic contact layer on the gate insulating layer using the catalyst metal as a seed; Forming a metal film on the ohmic contact layer; Applying photoresist on the metal film, diffraction exposure and developing to form photoresist patterns having different thicknesses; Selectively removing the metal layer, the ohmic contact layer, and the semiconductor layer using the photoresist pattern as a mask; Ashing the photoresist pattern to selectively remove the photoresist pattern of the portion having a thin thickness; And removing the metal layer and the ohmic contact layer by using the ashed photoresist pattern as a mask to form a source electrode and a drain electrode. 10. The method of claim 9, wherein the semiconductor layer is formed of an amorphous silicon layer or a polycrystalline silicon layer.