KR20070031090A - Method For Fabricating Thin Film Transistor And Method For Fabricating Liquid Crystal Display Device - Google Patents

Abstract

The present invention provides a method of manufacturing a thin film transistor inserting an ohmic contact layer formed by oxidizing a source / drain electrode therebetween in order to lower ohmic contact between a source / drain electrode and a semiconductor layer, and manufacturing a liquid crystal display device using the same. In particular, a method of manufacturing a thin film transistor includes forming a source / drain electrode on a substrate, oxidizing the source / drain electrode to form an ohmic contact layer, and forming a semiconductor on the ohmic contact layer. Forming a layer, forming a gate insulating film on the entire surface including the semiconductor layer, and forming a gate electrode on the semiconductor layer on the gate insulating film.

TFT, ohmic contact layer, metal oxide, work function

Description

Method for manufacturing thin film transistor and method for manufacturing liquid crystal display device using the same {Method For Fabricating Thin Film Transistor And Method For Fabricating Liquid Crystal Display Device}

1A to 1D are cross-sectional views illustrating a method of manufacturing a thin film transistor according to the prior art.

2A and 2B are cross-sectional views illustrating a method of manufacturing a thin film transistor according to the present invention.

3A to 3C are cross-sectional views illustrating a method of manufacturing a liquid crystal display device according to the present invention.

* Explanation of symbols on the main parts of the drawings

111: insulating substrate 112: gate electrode

113: gate insulating film 114: channel layer

115a: source electrode 115b: source / drain electrode

116: protective film 117: pixel electrode

124: ohmic contact layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a thin film transistor and a method of manufacturing a liquid crystal display device. In particular, an ohmic contact layer formed by oxidizing a source / drain electrode therebetween to reduce ohmic contact between a source / drain electrode and a semiconductor layer. The present invention relates to a method of manufacturing a thin film transistor inserting and forming a liquid crystal display device using the same.

The thin film transistor may be classified into a staggered type in which a gate electrode is formed on the source / drain electrode, and an inverse-staggered type in which the gate electrode is formed under the source / drain electrode. Specifically, the staggered thin film transistor is also referred to as a top-gate thin film transistor, and is composed of a stacked layer of a source / drain electrode, a semiconductor layer, a gate insulating film, and a gate electrode, and the reverse staggered thin film transistor is a bottom-gate thin film transistor. It is also called a transistor and consists of a laminated film of a gate electrode, a gate insulating film, a semiconductor layer, and a source / drain electrode.

At this time, an ohmic contact layer is inserted between the source / drain electrode and the semiconductor layer to lower the contact resistance between the source / drain electrode and the semiconductor layer.

On the other hand, the liquid crystal display device includes a thin film transistor (TFT) for selectively applying a signal to the pixel electrode, and storage for maintaining a charging state until the unit pixel region is subsequently addressed. A TFT array substrate, a color filter substrate having a color filter layer for realizing color, a liquid crystal layer enclosed between the two substrates, and a driving circuit for driving the TFT array substrate are provided to display an image by various external signals. Display.

Accordingly, a thin film transistor for pixel driving is formed in each display pixel in the display area of the TFT array substrate, and the thin film transistor for driving the pixel is operated in a non-display area to operate a scan line and a signal line. A thin film transistor for a driving circuit that applies a signal to a data line is formed.

Hereinafter, referring to the accompanying drawings, a method of manufacturing a thin film transistor in which an ohmic contact layer is inserted is as follows.

1A to 1D are cross-sectional views illustrating a method of manufacturing a thin film transistor according to the prior art.

First, as shown in FIG. 1A, a metal film for source / drain electrodes made of an Al metal film or a laminated film of Mo / Al / Mo is deposited on a transparent insulating substrate, for example, a glass substrate 11, and The metal layer is patterned by an etching process to form a source electrode 15a and a drain electrode 15b on the glass substrate.

Next, an amorphous silicon layer (n ⁺ Si) 24a doped with n-type impurities is deposited on the glass substrate 11 on which the source / drain electrodes 15a and 15b are formed. Then, a back exposure process using the source / drain electrodes 15a and 15b as an exposure mask is performed on the photoresist with the photoresist 25a coated on the doped amorphous silicon layer.

Thereafter, as shown in FIG. 1B, the exposed photoresist is developed to form a photoresist pattern 25.

1C, the doped amorphous silicon layer is etched on the source / drain electrodes 15a and 15b by etching a portion of the doped amorphous silicon layer exposed through an etching process using the photoresist pattern as a mask. An ohmic contact layer 24 composed of layers is formed. Thereafter, the photoresist pattern used as an etching mask is removed.

Subsequently, as shown in FIG. 1D, an amorphous silicon layer (a-Si: H) and an insulating film undoped on the entire surface of the resultant product. A metal film for a gate electrode such as MoW is sequentially deposited, and a photolithography process is applied to form the semiconductor layer 14, the gate insulating film 13, and the gate electrode 12.

As a result, a stagger is formed of a laminated film of the source / drain electrodes 15a and 15b, the ohmic contact layer 24, the semiconductor layer 14, the gate insulating film 13, and the gate electrode 12 at a predetermined portion of the glass substrate. The staggered type TFT is completed.

However, the manufacturing method of the thin film transistor according to the related art and the manufacturing method of the liquid crystal display device using the same have the following problems.

That is, in order to form an ohmic contact layer between the source / drain electrodes and the semiconductor layer, a complex process of depositing a doped amorphous silicon layer and applying a photoetch process is performed. At this time, the photo-etching process is coated with a photoresist, a material that is photosensitive with ultraviolet rays to the substrate on which the pattern is to be formed, the photoresist is exposed and developed, the desired etching layer is etched using the developed photoresist as a mask and then the photo It consists of a series of complex steps of stripping the register.

Therefore, there is a problem that by forming the ohmic contact layer, the overall number of steps for forming the thin film transistor increases and the process becomes complicated.

In addition, the addition of a photo etching process to form an ohmic contact layer, the research on the "low-mask technology" is actively being conducted to increase the productivity and to secure a process margin by reducing the number of photo etching process to a minimum It is against the recent trend.

In order to solve the above problems, the ohmic contact layer is formed by oxidizing the surface of the source / drain electrode to form a metal oxide layer (omic contact layer) capable of lowering the ohmic contact between the source / drain electrode and the semiconductor layer. It is an object of the present invention to provide a method of manufacturing a thin film transistor and a method of manufacturing a liquid crystal display device using the same, which does not need to add a separate process for forming.

Method of manufacturing a thin film transistor of the present invention for achieving the above object is the step of forming a source / drain electrode on the substrate, the step of oxidizing the source / drain electrode to form an ohmic contact layer, the ohmic Forming a semiconductor layer on the contact layer, forming a gate insulating film on the entire surface including the semiconductor layer, and forming a gate electrode on the semiconductor layer on the gate insulating film.

On the other hand, the manufacturing method of the liquid crystal display device of the present invention for achieving another object of the present invention comprises the steps of forming a source / drain electrode and data wiring on the substrate, and oxidizing the source / drain electrode to form an ohmic contact layer Forming a semiconductor layer on the ohmic contact layer, forming a gate insulating film on the entire surface including the semiconductor layer, and simultaneously forming a gate electrode on the semiconductor layer on the gate insulating film. Forming a gate line crossing the data line, forming a passivation layer on the entire surface including the gate electrode, and forming a pixel electrode contacting the drain electrode through the gate insulating layer and the passivation layer; Characterized in that made.

At this time, the work function value of the ohmic contact layer formed by oxidizing the source / drain electrode may be a middle value between the work function value of the source / drain electrode and the work function value of the semiconductor layer. Select to oxidize.

The method of oxidizing the source / drain electrodes includes a method of injecting oxygen gas at the time of depositing the material for the source / drain electrodes, a method of plasma surface treatment using oxygen gas to the patterned source / drain electrodes, and a patterning method. Heat treatment of the source / drain electrodes under an oxygen atmosphere.

Hereinafter, a method of manufacturing a thin film transistor and a method of manufacturing a liquid crystal display device using the same according to the present invention will be described in detail with reference to the accompanying drawings.

2A and 2B are cross-sectional views illustrating a method of manufacturing a thin film transistor according to the present invention, and FIGS. 3A to 3C are cross-sectional views illustrating a method of manufacturing a liquid crystal display device according to the present invention.

First, as shown in FIG. 2A, copper (Cu), aluminum (Al), aluminum alloy (AlNd), molybdenum (Mo), and chromium (Cr) on a transparent insulating substrate 111, for example, a glass substrate. Source / drain electrodes spaced apart by channel width by depositing titanium (Ti), tantalum (Ta), molybdenum-uranium (MoW), copper (Cu), etc. by sputtering and applying a photoetch process 115a and 115b are formed.

Next, the ohmic contact layer 124, which is a metal oxide layer, is formed on the surfaces of the source / drain electrodes 115a and 115b by oxidizing the source / drain electrodes.

In order to form the ohmic contact layer, a method of plasma surface treatment using oxygen gas may be applied to the patterned source / drain electrodes. Specifically, the substrate on which the source / drain electrodes are patterned may be introduced into the plasma apparatus and oxygen may be applied. The gas is plasmalated to oxidize the surface of the source / drain electrodes. The oxygen plasma treatment step is performed at a pressure of 1500 mT and a temperature range of 60 to 80 ° C., applying a power of 800 W, flowing the amount of oxygen about 500 sccm, and performing about 20 to 40 minutes.

In addition, the ohmic contact layer may be oxidized on the patterned source / drain electrode surface to form an ohmic contact layer, in which a substrate on which the source / drain electrode is patterned is oxidized by being introduced into a high-temperature furnace filled with oxygen.

On the other hand, as described above, there is a method of injecting the oxygen gas at the end of the deposition of the material for the source / drain electrode, without the surface oxidation treatment on the patterned source / drain electrode, the oxidation treatment by a method such as sputtering During deposition of the metal material for the drain electrode, oxygen is simultaneously added to deposit the metal material and simultaneously oxidize the metal material. As a result, the metal material deposited by the sputtering method becomes a metal oxide layer on the surface thereof, and then the metal material having the metal oxide layer on the surface is patterned by photolithography to form a source / drain electrode. As a result, a metal oxide layer is provided on the patterned source / drain electrode surface, and the metal oxide layer becomes an ohmic contact layer.

That is, the ohmic contact layer according to the present invention focuses on the principle that the work function value changes during metal oxidation and the resistance value decreases, and the work function value during metal oxidation becomes high.

However, the work function value of the ohmic contact layer should be lower than the work function value of the semiconductor layer to be formed in a later step. As a result, the work function value of the ohmic contact layer formed by oxidizing the source / drain electrode should be the middle value between the work function value of the source / drain electrode and the work function value of the semiconductor layer.

For example, when the semiconductor layer is formed using ZnO in a later step, the work function of ZnO is 5.0 eV or less, and therefore the work function of the source / drain electrode and the ohmic contact layer should be smaller than that.

First, in the case of depositing titanium (Ti) with a source / drain electrode, a work function value of Ti is 4.3 eV or less, and a work function value of titanium oxide (TiOx) formed by oxidizing the source / drain electrode is 4.6. Since it is ˜4.7 eV, it is suitable to use titanium as a source / drain electrode when forming a semiconductor layer using ZnO.

In addition, molybdenum (Mo) and copper (Cu) may be used as the material for the source / drain electrodes. The work function of Mo is 4.2 to 4.7 eV, and the work function of molybdenum oxide (MoOx) is 4.8 eV or less, and Cu is used. The work function of is below 4.3 eV and the work function of CuOx is 4.0 ~ 4.5 eV. Thus, even in the case of molybdenum oxide and copper oxide, since the work function value becomes the intermediate value between the work function value of molybdenum and copper and the work function value of the semiconductor layer ZnO, it is suitable for the source / drain electrode material according to the present invention.

Meanwhile, in addition to ZnO, amorphous silicon or polysilicon may be used as the semiconductor layer to be formed in a later process, and in this case, when the material for the source / drain electrode is selected, the material for the source / drain electrode The work function value of the oxide is selected to be a value between the work function value of the material for the source / drain electrodes and the work function value of the material for the semiconductor layer.

As described above, after forming the ohmic contact layer by oxidizing the material for the source / drain electrodes, as shown in FIG. 2B, ZnO, amorphous silicon, or polysilicon is formed on the entire surface including the ohmic contact layer 124. The semiconductor layer 114 is formed by depositing and patterning the photo-etched process.

Next, an inorganic insulating material such as silicon oxide (SiOx) or silicon nitride (SiNx) is deposited on the entire surface including the semiconductor layer 114 by a plasma enhanced chemical vapor deposition method to form a gate insulating layer 113.

 After that, copper (Cu), aluminum (Al), aluminum alloy (AlNd), molybdenum (Mo), chromium (Cr), titanium (Ti), tantalum (Ta), and molybdenum-tungsten on the gate insulating layer 113. (MoW) and the like are deposited and patterned to form the gate electrode 112. The gate electrode 112 is formed in a region corresponding to the channel layer of the semiconductor layer 114.

Thus, a predetermined layer of the insulating substrate 111 is formed of a laminated film of the source / drain electrodes 115a and 115b, the ohmic contact layer 124, the semiconductor layer 114, the gate insulating film 113, and the gate electrode 112. A staggered type TFT that is a top-gate TFT is completed. The TFT thus formed does not have to perform a separate photo etching process for forming an ohmic contact layer, thereby simplifying the process.

Meanwhile, referring to a method of manufacturing a liquid crystal display device according to the present invention, first, as shown in FIG. 3A, on a transparent insulating substrate 111, for example, a glass substrate, copper (Cu), aluminum (Al), Aluminum alloy (AlNd), molybdenum (Mo), chromium (Cr), titanium (Ti), tantalum (Ta), molybdenum-uranium (MoW), copper (Cu), etc. are deposited by sputtering method and the photoetch process Patterning is performed to form source / drain electrodes 115a and 115b and data lines (not shown). The data line is integrally formed with the source electrode, and the drain electrode is formed to be spaced apart from the source electrode by a channel width.

Next, the ohmic contact layer 124, which is a metal oxide layer, is formed on the surfaces of the source / drain electrodes 115a and 115b by oxidizing the source / drain electrodes.

In order to form the ohmic contact layer, a method in which a source / drain electrode patterned substrate is introduced into a plasma apparatus and oxygen gas is plasma-oxidized to oxidize the surface of the source / drain electrode, and a substrate in which the source / drain electrode patterned is used. There is a method in which a source / drain electrode surface is oxidized by being introduced into a high-temperature furnace filled with oxygen and heat-treated under an oxygen atmosphere.

On the other hand, there is a method of injecting oxygen gas at the end of the deposition of the material for the source / drain electrode without oxidation of the surface of the patterned source / drain electrode, and the oxidation of the source / drain electrode by sputtering or the like. At the time of material deposition, oxygen is simultaneously supplied to deposit a metal material and simultaneously oxidize the metal material. As a result, the metal material deposited by the sputtering method has a metal oxide layer (omic contact layer) on the surface thereof, and is then patterned by a photoetch process to form a source / drain electrode.

In this case, the work function value of the ohmic contact layer should be a value between the work function value of the semiconductor layer to be formed in a later process and the work function value of the source / drain electrodes.

For example, when the semiconductor layer is formed by using ZnO in a later step, the work function of ZnO is 5.0 eV or less, so the work function of the source / drain electrode and the ohmic contact layer should be smaller than that of titanium (Ti), Molybdenum (Mo) and copper (Cu) are suitable. For reference, the work function value of titanium is 4.3 eV or less, the work function value of titanium oxide (TiOx) is 4.6 to 4.7 eV, the work function value of molybdenum is 4.2 to 4.7 eV, and the work function value of molybdenum oxide (MoOx) is It is 4.8 eV or less, the work function value of copper is 4.3 eV or less, and the work function value of copper oxide (CuOx) is 4.0-4.5 eV.

Meanwhile, in addition to ZnO, amorphous silicon or polysilicon may be used as the semiconductor layer to be formed in a later process, and in this case, the work function value of the oxide of the material for the source / drain electrode may be the source / drain. The material for the source / drain electrodes is selected to be a value between the work function of the electrode material and the work function of the semiconductor layer material.

As described above, after forming the ohmic contact layer by oxidizing the material for the source / drain electrodes, as shown in FIG. 3B, ZnO, amorphous silicon, or polysilicon is formed on the entire surface including the ohmic contact layer 124. The semiconductor layer 114 is formed by depositing and patterning the photo-etched process.

Next, an inorganic insulating material such as silicon oxide (SiOx) or silicon nitride (SiNx) is deposited on the entire surface including the semiconductor layer 114 by a plasma enhanced chemical vapor deposition method to form a gate insulating layer 113.

 After that, copper (Cu), aluminum (Al), aluminum alloy (AlNd), molybdenum (Mo), chromium (Cr), titanium (Ti), tantalum (Ta), and molybdenum-tungsten on the gate insulating layer 113. (MoW) and the like are deposited and patterned to form a gate electrode 112 and a gate wiring (not shown). The gate electrode 112 is formed in a region corresponding to the channel layer of the semiconductor layer 114, and a gate wiring integrally formed with the gate electrode is formed to intersect the data wiring to define a unit pixel region.

As a result, a staggered type composed of a stacked film of the source / drain electrodes 115a and 115b, the ohmic contact layer 124, the semiconductor layer 114, the gate insulating layer 113, and the gate electrode 112 is formed. The TFT is completed, and the TFT is formed at the intersection of the gate wiring and the data wiring to control the turn-on or turn-off of the voltage.

Thereafter, as shown in FIG. 3C, an inorganic insulating material such as silicon nitride or silicon oxide is deposited on the entire surface including the gate electrode 112, or an organic insulating material such as benzocyclobutene (BCB) or an acrylic material is coated to form a protective film. 1116 is formed.

Subsequently, the protective layer 116 and the gate insulating layer 113 are patterned by a photolithography process to form a contact hole to expose the drain electrode 115b, and then contact the drain electrode 115b through the contact hole. ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide) is deposited and patterned by photolithography to form pixel electrodes 117 in each unit pixel region.

As described above, although the array substrate on which the TFT is formed is not shown, an opposite substrate on which the color filter layer and the common electrode are formed is bonded to the array substrate, and then a liquid crystal layer is formed between the two substrates and the liquid crystal inlet is sealed. A liquid crystal display device can be completed.

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.

The method of manufacturing the thin film transistor of the present invention as described above and the method of manufacturing the liquid crystal display device using the same have the following effects.

In other words, by oxidizing the surface of the source / drain electrodes to form a metal oxide layer (omic contact layer) capable of lowering the ohmic contact between the source / drain electrodes and the semiconductor layer, a separate process for forming the ohmic contact layer is not required. do.

As described above, the method of manufacturing the thin film transistor and the liquid crystal display device according to the present invention does not have to perform a separate photo-etching process for forming the conventional ohmic contact layer, which simplifies the process, reduces the manufacturing cost, and reduces the process time. Effective for mass production

Claims (17)

Forming a source / drain electrode on the substrate; Oxidizing the source / drain electrodes to form an ohmic contact layer; Forming a semiconductor layer on the ohmic contact layer; Forming a gate insulating film on the entire surface including the semiconductor layer; And forming a gate electrode over the semiconductor layer on the gate insulating film. The method of claim 1,  And forming a material for the source / drain electrodes so that the work function of the ohmic contact layer is a middle value between the work function of the source / drain electrodes and the work function of the semiconductor layer. Manufacturing method. The method of claim 2, The semiconductor layer is formed using ZnO, and the source / drain electrodes are formed using titanium (Ti), copper (Cu) or molybdenum (Mo). The method of claim 1, The semiconductor layer is a method of manufacturing a thin film transistor, characterized in that formed using ZnO, amorphous silicon or polysilicon. The method of claim 1, Method of manufacturing a thin film transistor, characterized in that formed using titanium (Ti), copper (Cu) or molybdenum (Mo) as the material for the source / drain electrode. The method of claim 1, Oxidizing the source / drain electrodes to form an ohmic contact layer, When depositing the source / drain material, a method of manufacturing a thin film transistor, characterized in that to inject the oxygen gas in the final step to oxidize the surface of the source / drain electrode. The method of claim 6, The material for the source / drain electrodes is deposited by a sputtering method. The method of claim 1, Oxidizing the source / drain electrodes to form an ohmic contact layer may include: And forming the source / drain electrodes by performing oxygen plasma treatment on the surface of the source / drain electrodes. The method of claim 1, Oxidizing the source / drain electrodes to form an ohmic contact layer may include: And forming the source / drain electrodes by heat-treating the source / drain electrodes in an oxygen atmosphere. Forming a source / drain electrode and a data wiring on the substrate; Oxidizing the source / drain electrodes to form an ohmic contact layer; Forming a semiconductor layer on the ohmic contact layer; Forming a gate insulating film on the entire surface including the semiconductor layer; Forming a gate electrode over the semiconductor layer on the gate insulating film and simultaneously forming a gate wiring crossing the data wiring; Forming a protective film on the entire surface including the gate electrode; And forming a pixel electrode contacting the drain electrode through the gate insulating film and the protective film. The method of claim 10,  And a work function value of the ohmic contact layer is a middle value between a work function value of a source / drain electrode and a work function value of a semiconductor layer. The method of claim 11, The semiconductor layer is formed using ZnO, and the source / drain electrodes are formed using titanium (Ti), copper (Cu) or molybdenum (Mo). The method of claim 10, The semiconductor layer is a method of manufacturing a liquid crystal display device, characterized in that formed using ZnO, amorphous silicon or polysilicon. The method of claim 11, And forming titanium (Ti), copper (Cu), or molybdenum (Mo) as the material for the source / drain electrodes. The method of claim 10, Oxidizing the source / drain electrodes to form an ohmic contact layer, When depositing the source / drain material, injecting oxygen gas in a final step to oxidize the source / drain electrode surface. The method of claim 10, Oxidizing the source / drain electrodes to form an ohmic contact layer, And forming the source / drain electrodes by oxygen plasma treatment on the surface of the source / drain electrodes. The method of claim 10, Oxidizing the source / drain electrode surface to form an ohmic contact layer, And after the forming of the source / drain electrodes, performing heat treatment on the source / drain electrodes under an oxygen atmosphere.

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