JP2848071B2 - Thin film transistor and method of manufacturing the same - Google Patents

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 of manufacturing the same.

[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 a row direction and a column direction, respectively. Then, when the thin film transistor is turned on, display data is written in the form of electric charges in the capacitance portion of the pixel, and when the thin film transistor is turned off, the pixel is driven by the written electric charge 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 pattern-formed on an upper surface of an insulating substrate 1 made of glass or the like. A 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 formed of impurity regions. A gate insulating film 3 is formed on the entire surface of the semiconductor thin film 2 and the insulating substrate 1, and a channel region 2a
A gate electrode 4 is pattern-formed on the upper surface of the gate insulating film 3 at a portion corresponding to. An interlayer insulating film 5 is formed on all 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 portions corresponding to the source region 2b and the drain region 2c. A source electrode 8 made of aluminum is pattern-formed so as to be connected to the source region 2b in all of the source contact holes 6 and at predetermined locations on the upper surface of the interlayer insulating film 5. A thin transparent electrode 9 made of ITO is formed in a part of the drain contact hole 7 and at a predetermined position on the upper surface of the interlayer insulating film 5 so as to be connected to the drain region 2c and patterned. A drain electrode 10 made of aluminum is pattern-formed on the remaining portion in the drain contact hole 7 and on a predetermined portion of the upper surface of the interlayer insulating film 5, and the drain region is formed via the transparent electrode 9 in the drain contact hole 7. 2c.

FIG. 9 shows another example of a conventional thin film transistor in which the same reference numerals are given to the same parts as in FIG. In this thin film transistor, a drain electrode 10 is connected to the drain region 2c and formed in a pattern at all of the inside of the drain contact hole 6 and at predetermined locations on the upper surface of the interlayer insulating film 5, and a part of the surface of the drain electrode 10 and the interlayer A transparent electrode 9 is pattern-formed at a predetermined location on the upper surface of the insulating film 5.

[0005]

However, in the thin film transistor shown in FIG. 8, since the ITO for forming the transparent electrode 9 is uniformly deposited by a sputtering method using O ₂ gas, The surface of the drain region 2c in the portion of the drain contact hole 7 is easily oxidized, so that it is difficult to lower the contact resistance between the drain region 2c and the transparent electrode 9, and the thin transparent electrode 9 is formed in the deep drain contact hole 7. Due to the formation, there is a problem that the transparent electrode 9 may be disconnected. On the other hand, in the thin film transistor shown in FIG. 9, since the transparent electrode 9 made of ITO is connected not directly to the drain region 2c but through the drain electrode 10 made of aluminum, the transparent electrode 9 made of ITO is preferably connected to the drain region 2c. However, when ITO and aluminum are in contact with each other, the ITO is dissolved in a developing solution (alkali aqueous solution) of a positive photoresist used as a mask for etching the ITO. When patterning the transparent electrode 9 by etching the ITO deposited as described above, there is a problem that it is not possible to use a positive type photoresist which is easy to use and has high resolution. An object of the present invention is to provide a thin film transistor and a method of manufacturing the same, in which a transparent electrode made of ITO can be satisfactorily connected to a drain region, and a positive photoresist can be used as a mask when etching ITO. It is in.

[0006]

According to the first aspect of the present invention,
A transparent electrode made of ITO and a source region or a drain region of a semiconductor thin film are formed in a region other than a region where a portion of the relay electrode made of chrome is in contact with the transparent electrode and a region of the relay electrode other than the region where the transparent electrode is in contact. It is connected via an electrode made of aluminum that comes into contact. The invention according to claim 2 provides a relay electrode made of chromium in which a part of the region is in contact with the transparent electrode, between the semiconductor thin film having a source region and a drain region and the transparent electrode made of ITO . An electrode made of aluminum is provided in contact with a region other than the region where the transparent electrode contacts, and the transparent electrode is patterned using a positive photoresist.

[0007]

According to the present invention, the transparent electrode made of ITO is connected not directly to the drain region but via the relay electrode made of chromium and the drain electrode made of aluminum, so that the transparent electrode made of ITO is connected to the drain region. When a transparent electrode made of ITO is formed in a pattern, it can be prevented from coming into contact with aluminum even when it comes into contact with chromium, so that it can be used as a mask when etching ITO. ITO in a developing solution (alkali aqueous solution)
Does not dissolve, so that a positive-type photoresist that is easy to use and has high resolution can be used.

[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 is deposited on the entire upper surface of an insulating substrate 11 made of glass or the like to a thickness of about 500 ° by a plasma CVD method. Next, although not shown, using a photoresist as a mask, 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. Thereafter, the photoresist as an ion implantation mask is removed by etching. Next, by irradiating a 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.

Next, as shown in FIG. 2, unnecessary portions of the semiconductor thin film 13 are etched and removed by photolithography, thereby patterning the semiconductor thin film 13 only in the thin film transistor forming 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 formed of the impurity regions. Next, as shown in FIG. 3, a gate insulating film 14 made of silicon oxide is deposited on the entire surface to a thickness of about 1000 to 1500 ° using a sputtering apparatus.

Next, as shown in FIG.
On the upper surface of the gate insulating film 14 corresponding to the portion 3a, a gate electrode 15 made of chromium is patterned to a thickness of about 1000 ° using a sputtering apparatus, 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 formed at a predetermined position on the upper surface of the gate insulating film 14 in the vicinity of c at the same thickness by patterning.

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 at a predetermined position on the upper surface of the gate insulating film 14 by using a sputtering apparatus to a thickness of about 500 °. To form a pattern. In this case, after the ITO is uniformly deposited on the entire surface, an unnecessary portion of the ITO is etched and removed by a photolithography technique to form the transparent electrode 17 in a pattern. Since it is only in contact with the electrode 15 and the relay electrode 16) and not in contact with aluminum (a source electrode and a drain electrode to be formed later), even if a positive photoresist is used as a mask for etching the ITO. In addition, it is possible to prevent ITO from dissolving in the developer (alkali aqueous solution) of the 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 3000 °. Next, the interlayer insulating film 18 and the gate insulating film 1 in 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 pattern-formed at a predetermined location on the upper surface of the source contact hole 19 and the interlayer insulating film 18 by using a sputtering device to a thickness of about 5000 °,
At the same time, a drain electrode 23 of the same thickness is formed in a predetermined pattern on the upper surface of the drain contact hole 20, the relay contact hole 21, and the interlayer insulating film 18 in the same thickness. 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, a 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 but 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.
And can be connected well. Further, when the uniformly deposited ITO is etched to form a pattern of the transparent electrode 17, even if the ITO comes into contact with chromium, it does not come into contact with aluminum, so that a positive type as a mask for etching the ITO is used. Since the ITO does not dissolve in the photoresist developing solution (aqueous alkaline solution), it is possible to use a positive type 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, the number of manufacturing steps can be prevented from increasing.

[0015]

As described above, according to the present invention, 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. Since the transparent electrode made of ITO can be satisfactorily connected to the drain region, and when the transparent electrode made of ITO is formed in a pattern, it is possible to prevent ITO from coming into contact with chromium and not into contact with aluminum. ITO does not dissolve in a positive photoresist developing solution (aqueous alkaline solution) as a mask for etching,
Therefore, it is possible to use a positive type photoresist which is easy to use and has a high resolution.

[Brief description of the drawings]

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

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

FIG. 3 is a cross-sectional view showing a state where a gate insulating film is formed in manufacturing the thin film transistor.

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

FIG. 5 is a cross-sectional view showing a state where a transparent electrode is formed in manufacturing the thin film transistor.

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

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

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

[Explanation of symbols]

 Reference Signs List 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

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G02F 1/136 G02F 1/1343 G09F 9/30 H01L 29/786 H01L 21/70

Claims (2)

(57) [Claims] [Claim 1] A source region or a drain region of the transparent electrode and the semiconductor thin film made of ITO, a part of the area is the
Relay electrode made of chromium in contact with the transparent electrode, and the
The relay electrode is in contact with an area other than the area where the transparent electrode contacts.
A thin film transistor, wherein the thin film transistor is connected via an electrode made of aluminum to be touched . 2. A relay electrode made of chromium , a part of which is in contact with the transparent electrode, is provided between a semiconductor thin film having a source region and a drain region and a transparent electrode made of ITO .
A method of manufacturing a thin film transistor, comprising: providing an electrode made of aluminum in contact with a region of the relay electrode other than the region in contact with the transparent electrode; and patterning the transparent electrode using a positive photoresist.