JPH04309928A - Thin film transistor and manufacture thereof - Google Patents

Abstract

PURPOSE:To reduce the breaking and resistance value of a data line and to increase the aperture ratio by employing the two-layered structure of polycrystalline silicon and an aluminum layer, formed by selective chemical vapor-phase growth, for the data line. CONSTITUTION:The polycrystal silicon layer 304 with about 500Angstrom film thickness is formed as the wiring material of the data line, this polycrystalline silicon layer 304 is etched, and the aluminum film 303 with about 8000Angstrom film thickness is selectively grown on the polycrystalline silicon layer 304 by chemical vapor- phase growth to form the data line in the two-layered structure. After the data line is thus formed, an insulating film 306 is formed as a removal film for protecting the data line and removing DC components and a contact hole for a drain area 303 is bored. Then when a transparent conduction film ITO 310 for applying a voltage to liquid crystal is formed, the aluminum film is formed at the part of the ITO film 310 which contacts the drain area 303, so a step that the ITO film should have is made small. The plane interval between the data line and a picture element electrode is narrowed down to increase the aperture ratio.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film transistor for driving a liquid crystal display device and a method for manufacturing the same.

0002

[Prior Art] The conventional method for manufacturing thin film transistors is as follows:
After forming source and drain regions, a channel layer, a gate oxide film, and a gate electrode, an interlayer insulating film was formed, and a contact hole was opened in the interlayer insulating film for leading out wiring from the transistor portion.

In FIG. 4, an ITO film 402 is formed as a pixel electrode for applying a voltage to the liquid crystal, and an aluminum film containing silicon and copper as impurities is sputtered to become a data line on the same plane as the ITO film 402. FIG. The reason why the ITO film 402 is formed before the aluminum film 401 is that the ITO film 402 is not attacked by aluminum etching solution, but the aluminum film 401 is
This is because it is attacked by the hydrochloric acid contained in the TO etching solution.

When forming the aluminum film 401 by a normal sputtering method, when the aluminum film 401 is etched to include silicon and copper as impurities, the silicon in the aluminum film cannot be etched with an aluminum etching solution, so it is etched. The silicon remaining in the area other than the aluminum film 401 that will become the data line has been etched using a chemical dry etching method. 401
If you do not etch the silicon remaining in other areas,
This is because it causes a short circuit between the ITO film 402 and the aluminum film 401. Note that copper contained in the aluminum film 401 does not pose a problem because it is etched with an aluminum etchant. Furthermore, in order to maintain the insulation between the ITO film 402 and the aluminum film 401, it was necessary to set a distance 1 between the two films of 4 to 10 μm.

[0005]

[Problem to be Solved by the Invention] However, the data wiring formed by the above-mentioned conventional technique is formed by a sputtering method using an aluminum target to which several percent of silicon and copper impurities are added. Due to the influence of the impurities silicon and copper, the resistance value is 1.0% compared to pure aluminum.
Since the number of pixels increases by 5 to 2 times, as the liquid crystal display element becomes larger and more precise, vertical unevenness on the screen becomes noticeable. Here, the impurity silicon is used to make an ohmic contact between the source region of the thin film transistor and the aluminum and to lower the resistance, and the copper is used to prevent the aluminum wiring from forming a hillock and causing disconnection. be.

[0006] Furthermore, the data line formed by sputtering a single layer of aluminum containing impurities may break due to the influence of particles, or may be chemically etched to etch the silicon remaining in the area where the aluminum should be etched. It is necessary to carry out a dry etching method,
When the silicon is etched, the second silicon dioxide film forming the interlayer insulating film is also etched, which may lead to poor interlayer insulation or contact. especially,
Since the silicon dioxide film tends to be selectively etched in the thin portions of the interlayer insulating film, the defects are more likely to occur in the thin portions. If the scanning line under the interlayer insulating film is formed of a material that can be etched by a chemical dry etching method, it may be etched through the defect, leading to disconnection of the scanning line and causing line defects in the active matrix element. There was a problem that it also caused

Next, when an aluminum film is formed after forming the ITO film, the distance between the two films is set to several microns to avoid short circuits.
If there is a gap of m, it becomes difficult to miniaturize the active matrix element. In addition, in order to protect the aluminum film of the data line and to prevent the DC voltage component applied to the data line from being applied to the liquid crystal, a silicon dioxide film with a thickness of several thousand angstroms was formed after the above two films were formed. Then, there was a problem that only a voltage lower than the voltage applied to the ITO film was applied to the liquid crystal, resulting in waste.

[0008]

[Means for Solving the Problems] In an active matrix element using thin film transistors formed on a glass substrate, there are the following steps: a) forming a polycrystalline silicon layer with a thickness of about 500 Å as a data line wiring material; and b) the above-mentioned steps. c) etching the polycrystalline silicon layer to a thickness of 8000 Å on the polycrystalline silicon layer by chemical vapor deposition;
The data line has a two-layer structure by selectively growing a certain amount of aluminum film.

[0009] In claim 1, the data line is characterized in that aluminum selectively grown by chemical vapor deposition is used.

After forming the data line as claimed in claim 1, there are the following steps: a) forming an insulating film as a protection film for the data line and a film for removing DC components; and b) opening a contact hole to the drain region. , c) When forming the transparent conductive film ITO for applying voltage to the liquid crystal, since an aluminum film is formed in the process of claim 1(c) also at the contact portion of the ITO film to the drain region, the ITO It is characterized in that the step difference to be taken in the film is reduced, thereby reducing the disconnection of the film, and in that the planar interval between the data line and the pixel electrode is narrowed to increase the aperture ratio.

According to the first and third aspects, the pixel electrode is formed after the data line is formed, and the insulating film on the pixel electrode is eliminated.

0012

EXAMPLES The present invention will be explained in detail below based on examples.

FIG. 1 shows a top view of the present invention.
Reference numeral 1 denotes a source and drain region and a channel region formed of primary polycrystalline silicon, and 102 a multilayer wiring structure formed of phosphorus-doped polycrystalline silicon, metal silicide, pure metal, or a combination of multiple layers of the above three layers. 104 is a scanning line in which second polycrystalline silicon is formed in the first layer to a thickness of about 500 Å, and then dimethylaluminum hydride gas shown by the following formula is formed.

The data line has a two-layer structure in which an aluminum film is selectively formed by chemical vapor deposition using [Chemical 1], and 105 is an ITO film (indium-tin oxide film) that becomes a pixel electrode.
3 is a contact hole. Further, the distance between the data line 104 and the pixel electrode 105 is assumed to be l.

In FIG. 1, a cross-sectional view taken along a dashed line A is shown in FIG.
becomes. 201 is a second silicon dioxide layer formed by chemical vapor deposition or sputtering to become an interlayer insulating film;
02 is a second polycrystalline silicon layer, 203 is a second polycrystalline layer 202 treated with diluted hydrofluoric acid using the dimethylaluminum hydride gas to an extent that does not damage the second silicon dioxide layer 201, and then washed with water. The aluminum film has a thickness of about 8000 Å and is grown by selective chemical vapor deposition with hydrogen atoms terminated on the surface, and the two layers 202 and 203 form the data line. 204 is formed by chemical vapor deposition or sputtering to protect the data line, cut the DC voltage component, and planarize the active matrix element by making the film thickness about 0.5 to 1 μm. 205 is an ITO film serving as a pixel electrode.

FIG. 3 is a sectional view taken along a dashed-dotted line B that crosses the thin film transistor portion in FIG. 301, 302
, 303 are a source region, a channel layer, and a drain region formed of first polycrystalline silicon, 304 is a first silicon dioxide layer which becomes a gate insulating film formed by thermal oxidation, etc., and 305 is a first polycrystalline silicon layer. A gate electrode formed of a multilayer structure of crystalline silicon, metal silicide, pure metal, or the above materials, 306 is a second silicon dioxide layer serving as an interlayer insulating film, 307 is a second polycrystalline silicon layer, and 308 is a selected layer. The grown aluminum layer, 309 is a third silicon dioxide layer, and 310 is an ITO film that becomes a pixel electrode.

The thin film transistor having the above structure has a data line with a two-layer structure and the second layer wiring is formed by selective chemical vapor deposition.
Even if there is a disconnection with a length within twice the thickness of the aluminum layer 03, the selective growth will proceed not only perpendicular to the surface of the film but also in the plane, so the aluminum layer 203 will short-circuit and repair the disconnection. enable. Aluminum layer 203, 308
As shown in FIGS. 2 and 3, the state before forming the second silicon dioxide layers 201, 306 and the second polycrystalline silicon layers 202, 30
Since only 7 is exposed on the surface, the dimethylaluminum hydride, which grows on polycrystalline silicon but not on silicon dioxide, is thermally decomposed at a temperature of about 270° C. to convert aluminum into polycrystalline silicon layer 202. , 307, there is no need to etch the aluminum, thereby preventing resist exposure due to dust and disconnections and short circuits resulting in poor etching, thereby greatly reducing the number of disconnections.

Aluminum film 20 forming a data line
3 is made of pure aluminum, so the wiring resistance value of the line is lower than that of a film formed by sputtering mixed with impurities, so even if the LCD panel becomes large in area and high definition, the upper and lower parts of the screen It can reduce unevenness. Furthermore, when an aluminum film that can become a data line is formed and etched by a sputtering method using aluminum containing silicon and copper as impurities as a target as usual, silicon remains in the place where it should be etched, so as shown in FIG. In order to prevent a short circuit between the data line 104 and the pixel electrode 105, a chemical dry etching method was used to remove silicon, which causes defects in the interlayer insulating film and contact holes, but selective chemical vapor deposition method By forming the aluminum layer, it is not necessary to use a dry etching method, so the above-mentioned defects can be eliminated. Furthermore, the contact resistance value between pure aluminum, which becomes the data line, and the source region is large enough to affect the characteristics of the thin film transistor, since the chemical vapor deposition of aluminum on silicon using the dimethylaluminum hydride gas is epitaxial growth. Must not be.

Next, in FIG. 1, the data line 104 and the pixel electrode 1
Shortening the interval 05 brings about an increase in the aperture ratio, but in order to achieve this, it is desirable to form the pixel electrode 105 through an insulating film after forming the data line 104. However, when etching the ITO film 310 in FIG. 3, the aluminum layer 308 forming the data line is not etched by the hydrochloric acid contained in the ITO etching solution, and as a protective film and a film for cutting the DC component of the voltage applied to the data line. The thickness of the third silicon dioxide layer 309 is 0.5 to 1 μm, and the thickness of the second silicon dioxide layer 306 which becomes the interlayer insulating film and the first silicon dioxide layer 304 which becomes the gate insulating film is 0.5 to 1 μm. The total thickness of the layers is 1 μm, and the step difference between the drain region 303 and the ITO film 310 is 2 μm at maximum.
Since the ITO film is difficult to etch, it is desirable to keep the film thickness to 2000 Å or less as much as possible, so the above-mentioned step may cause disconnection of the ITO in the contact hole.

Here, in order to selectively grow aluminum, polycrystalline silicon is formed on the entire surface of the substrate and then etched. It cannot be etched because it contains silicon. Therefore, if the second polycrystalline silicon formed in the contact hole opened in the drain region 303 is covered with a resist during etching to prevent it from being etched, the contact hole is filled with aluminum, and the ITO film 310 is Aluminum film 308 covers the 1 μm step that occurs in the silicon sesquioxide layer.
Since it is only necessary to make contact with the wire, it also prevents disconnection. Note that since ohmic contact cannot be made between aluminum and ITO, the contact resistance increases when the voltage applied to the contact portion is low, but this does not need to be a problem because it is not as large as the on-resistance of a thin film transistor. However, if the contact resistance is large and becomes a problem, the resistance value can be reduced by opening the contact hole so large that the aluminum film remains.

Furthermore, since the thin film transistor manufactured through the process of the present invention does not require the formation of an insulating film on the pixel electrode, the voltage applied to the pixel electrode does not drop and the thin film transistor becomes a display element, such as a liquid crystal. It is also possible to reduce the driving voltage of the thin film transistor.

[0021]

[Effects of the Invention] According to the present invention described above, the data line has a two-layer structure of polycrystalline silicon and aluminum formed by selective chemical vapor deposition, thereby reducing disconnection of the data line. Yields can be increased in manufacturing thin film transistors, and wiring resistance of data lines can be reduced to about half, making it possible to respond to larger areas and higher definition of active matrix elements. In addition to the above effects, if the pixel electrode is formed after the data line is formed, disconnection of the ITO film is eliminated, the aperture ratio is increased, and the device can be planarized and the driving voltage of the thin film transistor can be reduced.

[Brief explanation of drawings]

[Figure 1] Top view of an active matrix element using the thin film transistor of the present invention

[Figure 2] Cross-sectional view at chain point A in Figure 1

[Figure 3
] Cross-sectional view at chain point B in Figure 1

[Figure 4] Positional relationship diagram of data lines and pixel electrodes of an active matrix element using conventional thin film transistors

[Explanation of symbols]

101 First polycrystalline silicon layer 102 Gate electrode and gate line 103 Contact hole 104 Data line 105 Pixel electrode 201 Interlayer insulation film 202 Second polycrystalline silicon layer 203 Aluminum layer 204 Silicon dioxide layer 205 Pixel electrode 301 Source area 302 Channel layer 303 Drain region 304 First silicon dioxide layer 305 Gate electrode 306 Interlayer insulation film 307 Second polycrystalline silicon layer 308 Aluminum layer 309 Silicon dioxide layer 310 Pixel electrode

Claims (4)

[Claims] 1. An active matrix element using thin film transistors formed on a glass substrate, comprising: a) forming a polycrystalline silicon layer with a thickness of about 500 Å as a data line wiring material; and b) forming the polycrystalline silicon layer. c) forming a film with a thickness of 8000 Å on the polycrystalline silicon layer by chemical vapor deposition;
A thin film transistor and a method for manufacturing the same, characterized in that a data line has a two-layer structure by selectively growing a moderate amount of aluminum film. 2. The thin film transistor and method for manufacturing the same according to claim 1, wherein aluminum selectively grown by chemical vapor deposition is used for the data line. 3. After forming the data line as in claim 1, a) forming an insulating film as a protection film for the data line and a film for removing direct current components, and b) opening a contact hole to the drain region. and c) forming an aluminum film in the step of claim 1(c) also at the contact portion of the ITO film to the drain region when forming the transparent conductive film ITO for applying voltage to the liquid crystal; and a thin film transistor and its manufacturing method, characterized in that the two-dimensional distance between the data line and the pixel electrode is narrowed. 4. A thin film transistor and method for manufacturing the same, characterized in that a pixel electrode is formed after forming a data line as claimed in claims 1 and 3, and an insulating film on the pixel electrode is eliminated.