JPH05142576A - Thin-film transistor and production thereof - Google Patents

Abstract

PURPOSE:To well connect a transparent electrode consisting of ITO to a drain region and to form the transparent electrode as a pattern by using a positive type photoresist. CONSTITUTION:The transparent electrode 17 consisting of the ITO and the drain region 13c of a semiconductor thin film 13 is connected via a junction electrode 16 consisting of chromium and a drain electrode 23 consisting of aluminum. Namely, he transparent electrode 17 is connected to the drain region 13c not directly but via the junction electrode 16 and the drain electrode 23. Then, the transparent electrode 17 can be well connected to the drain region 13c. In addition, the transparent electrode 17 can be so formed as not to come into contact with the aluminum in spite of the contact of the ITO with the chromium at the time of forming the pattern of the transparent electrode even if the uniformly deposited ITO is etched and, therefore, the dissolution of the ITO in a developer (aq. alkaline soln.) of a positive type photoresist is obviated even if the positive type photoresist is used as the mask at the time of etching the ITO.

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 having a transparent electrode made of ITO and a method for manufacturing the thin film transistor.

[0002]

2. Description of the Related Art For example, in an active matrix type liquid crystal display device, a thin film transistor is provided for each pixel (liquid crystal) corresponding to each intersection of transparent electrodes (scanning electrodes and display electrodes) provided in the row direction and the column direction. Then, when the thin film transistor is turned on, display data is written in the electrostatic capacity portion of the pixel in the form of electric charge, and when the thin film transistor is turned off, the written electric charge drives the pixel for a predetermined time.

FIG. 8 shows an example of a thin film transistor in such a conventional liquid crystal display device. In this thin film transistor, a semiconductor thin film 2 is patterned on an upper surface of an insulating substrate 1 made of glass or the like. The central portion of the semiconductor thin film 2 is a channel region 2a, and both sides thereof are a source region 2b and a drain region 2c which are impurity regions. The gate insulating film 3 is formed on the entire surface of the semiconductor thin film 2 and the insulating substrate 1, and the channel region 2a is formed.
A gate electrode 4 is pattern-formed on the upper surface of the gate insulating film 3 corresponding to. An interlayer insulating film 5 is formed on the entire surfaces of the gate electrode 4 and the gate insulating film 3. A source contact hole 6 and a drain contact hole 7 are formed in the interlayer insulating film 5 and the gate insulating film 3 in the portions corresponding to the source region 2b and the drain region 2c. A source electrode 8 made of aluminum is connected to the source region 2b and pattern-formed in the entire source contact hole 6 and at a predetermined position on the upper surface of the interlayer insulating film 5. A thin transparent electrode 9 made of ITO is connected to the drain region 2c to form a pattern in a part of the drain contact hole 7 and at a predetermined position on the upper surface of the interlayer insulating film 5. A drain electrode 10 made of aluminum is pattern-formed on the remaining portion in the drain contact hole 7 and a predetermined portion on the upper surface of the interlayer insulating film 5, and the drain region is formed through the transparent electrode 9 in the drain contact hole 7 portion. 2c is connected.

Next, FIG. 9 in which parts having the same names as those in FIG. 8 are given the same reference numerals shows another example of a conventional thin film transistor. In this thin film transistor, the drain electrode 9 is connected to the drain region 2c at a predetermined position on the entire surface of the drain contact hole 6 and on the upper surface of the interlayer insulating film 5 to form a pattern. A transparent electrode 8 is patterned on a predetermined portion of the upper surface of the insulating film 5.

[0005]

However, in the thin film transistor shown in FIG. 8, the ITO for forming the transparent electrode 8 is uniformly deposited by the sputtering method using O ₂ gas. The surface of the drain region 2c in the contact contact hole 7 portion is easily oxidized, so that it is difficult to reduce the contact resistance between the drain region 2c and the transparent electrode 9, and a thin transparent electrode 9 is formed in the deep drain contact hole 7. Due to the formation relationship, there is a problem that the transparent electrode 9 may be broken. On the other hand, in the thin film transistor shown in FIG. 9, since the transparent electrode 8 made of ITO is connected to the drain region 2c not directly but via the drain electrode 9 made of aluminum, the transparent electrode 8 made of ITO is well connected to the drain region 2c. However, if the ITO and aluminum are in contact with each other, the ITO dissolves in the developer (alkaline aqueous solution) of the positive photoresist as a mask for etching the ITO. There is a problem that a positive photoresist which is easy to use and has high resolution cannot be used when the transparent electrode 8 is patterned by etching the ITO thus deposited. An object of the present invention is to provide a thin film transistor which can well connect a transparent electrode made of ITO to a drain region and can use a positive photoresist as a mask when etching ITO, and a manufacturing method thereof. Especially.

[0006]

The invention according to claim 1 is
The transparent electrode made of ITO and the drain region of the semiconductor thin film are connected via a relay electrode made of chromium and a drain electrode made of aluminum. According to a second aspect of the invention, in manufacturing the thin film transistor according to the first aspect, the transparent electrode is patterned by etching the uniformly deposited ITO using a positive photoresist as a mask. ..

[0007]

According to the present invention, since the transparent electrode made of ITO is connected to the drain region not directly but via the relay electrode made of chromium and the drain electrode made of aluminum, the transparent electrode made of ITO is connected to the drain region. Good contact can be made, and when the transparent electrode made of ITO is patterned, it can be prevented from coming into contact with aluminum even if the ITO comes into contact with chrome. In a developing solution (alkali aqueous solution) for mold photoresist
Therefore, it is possible to use a positive photoresist which does not dissolve and is easy to use and has high resolution.

[0008]

1 to 7 show respective steps of manufacturing a thin film transistor according to an embodiment of the present invention. Therefore, the structure of the thin film transistor will be described together with its manufacturing method with reference to these drawings in order.

First, as shown in FIG. 1, an amorphous silicon film 12 having a thickness of about 500 Å is deposited on the entire upper surface of an insulating substrate 11 made of glass or the like by a plasma CVD method. Next, although not shown, an impurity is implanted into the amorphous silicon film 12 in a portion where the source region 13b and the drain region 13c are to be formed by an ion implantation device using a photoresist as a mask. Then, the photoresist serving as the ion implantation mask is removed by etching. Next, by irradiating XeCl excimer laser, the amorphous silicon film 12 is crystallized into a semiconductor thin film 13 made of a polysilicon film, and the implanted impurities are activated.

Then, as shown in FIG. 2, the semiconductor thin film 13 in the unnecessary portion is etched and removed by a photolithography technique, so that the semiconductor thin film 13 is patterned only in the thin film transistor formation region. In this state, since the impurities have already been implanted, the central portion of the semiconductor thin film 13 is a channel region 13a, and both sides thereof are a source region 13b and a drain region 13c which are impurity regions. Next, as shown in FIG. 3, a gate insulating film 14 made of silicon oxide is deposited on the entire surface by a sputtering apparatus to a thickness of about 1000 to 1500Å.

Next, as shown in FIG. 4, the channel region 1
A gate electrode 15 made of chromium is patterned on the upper surface of the gate insulating film 14 corresponding to the portion 3a using a sputtering device to a thickness of about 1000Å, and at the same time, the drain region 13 is formed in a portion other than the portion corresponding to the semiconductor thin film 13.
A relay electrode 16 also made of chromium is patterned in the same thickness at a predetermined position on the upper surface of the gate insulating film 14 in the vicinity of c.

Next, as shown in FIG. 5, a transparent electrode 17 made of ITO is formed on a part of the surface of the relay electrode 16 and a predetermined portion of the upper surface of the gate insulating film 14 with a sputtering device to a thickness of about 500 Å. To form a pattern. In this case, the transparent electrode 17 is patterned by depositing ITO uniformly on the entire surface and then removing the unnecessary portion of the ITO by etching using a photolithography technique. Since it is only in contact with the electrode 15 and the relay electrode 16) and not with aluminum (source electrode and drain electrode to be formed later), even if a positive photoresist is used as a mask when etching ITO. It is possible to prevent ITO from being dissolved in the developer (alkali aqueous solution) of this positive photoresist.

Next, as shown in FIG. 6, an interlayer insulating film 18 made of silicon nitride is formed on the entire surface by plasma CVD.
Is deposited to a thickness of about 3000Å. Next, the interlayer insulating film 18 and the gate insulating film 1 in the portions corresponding to the source region 13b, the drain region 13c and the relay electrode 16 are formed.
4, a source contact hole 19, a drain contact hole 20 and a relay contact hole 21 are formed. Next, as shown in FIG. 7, a source electrode 22 made of aluminum is patterned at a predetermined position on the upper surfaces of the source contact hole 19 and the interlayer insulating film 18 using a sputtering device to a thickness of about 5000 Å.
At the same time, a drain electrode 23, which is also made of aluminum, is patterned to have the same thickness at predetermined positions on the upper surface of the drain contact hole 20, the relay contact hole 21, and the interlayer insulating film 18. In this state, the source electrode 22 is connected to the source region 13b and the drain electrode 23
Is connected to the drain region 13c and the relay electrode 16,
The transparent electrode 17 is connected to the drain region 13c via the relay electrode 16 and the drain electrode 23. Thus, the thin film transistor is manufactured.

Thus, in this thin film transistor,
Since the transparent electrode 17 made of ITO is connected not directly to the drain region 13c via the relay electrode 16 made of chromium and the drain electrode 23 made of aluminum, the transparent electrode 17 made of ITO is connected to the drain region 13c.
Can be connected well with. Further, when the transparent electrode 17 is patterned by etching the uniformly deposited ITO, the ITO does not come into contact with aluminum even if it comes into contact with chrome. Therefore, the positive type as a mask when etching the ITO is used. Since ITO does not dissolve in the photoresist developing solution (alkali aqueous solution), it is possible to use a positive photoresist which is easy to use and has high resolution. Furthermore, since the relay electrode 16 is formed simultaneously with the formation of the gate electrode 15, it is possible to prevent the number of manufacturing steps from increasing.

[0015]

As described above, according to the present invention, since the transparent electrode made of ITO is connected to the drain region not directly but through the relay electrode made of chromium and the drain electrode made of aluminum, the ITO is made. The transparent electrode made of ITO can be satisfactorily connected to the drain region, and when the transparent electrode made of ITO is patterned, it can be prevented from coming into contact with aluminum even if the ITO comes into contact with chrome. ITO is not dissolved in the developer (alkali aqueous solution) of the positive photoresist as a mask for etching,
Therefore, a positive photoresist which is easy to use and has high resolution can be used.

[Brief description of drawings]

FIG. 1 is a view showing a state in which impurities are implanted into an amorphous silicon film formed on an entire upper surface of an insulating substrate and then the amorphous silicon film is crystallized and implanted impurities are activated in manufacturing a thin film transistor according to an embodiment of the present invention. Sectional view.

FIG. 2 is a cross-sectional view showing a state in which an unnecessary portion of the semiconductor thin film is removed by etching when manufacturing the same thin film transistor.

FIG. 3 is a cross-sectional view of a state in which a gate insulating film is formed in manufacturing the same thin film transistor.

FIG. 4 is a cross-sectional view of a state in which a gate electrode and a relay electrode are formed in manufacturing the same thin film transistor.

FIG. 5 is a cross-sectional view of a state in which a transparent electrode is formed in manufacturing the same thin film transistor.

FIG. 6 is a cross-sectional view showing a state in which a contact hole is formed after forming an interlayer insulating film in manufacturing the same thin film transistor.

FIG. 7 is a cross-sectional view showing a state where a source electrode and a drain electrode are formed in manufacturing the same thin film transistor.

FIG. 8 is a cross-sectional view showing an example of a conventional thin film transistor.

FIG. 9 is a cross-sectional view showing another example of a conventional thin film transistor.

[Explanation of symbols]

 13 semiconductor thin film 13c drain region 14 gate insulating film 15 gate electrode 16 relay electrode 17 transparent electrode 18 interlayer insulating film 23 drain electrode

Claims (2)

[Claims] 1. A thin film transistor characterized in that a transparent electrode made of ITO and a source region or a drain region of a semiconductor thin film are connected via a relay electrode made of chromium and an electrode made of aluminum. 2. The method of manufacturing a thin film transistor according to claim 1, wherein the transparent electrode is patterned by etching the uniformly deposited ITO by using a positive photoresist as a mask. ..