JPH0645606A - Manufacture of thin-film transistor matrix - Google Patents

Abstract

PURPOSE:To obtain a good TFT characteristic wherein a gate dielectric withstand voltage is not lowered even when a gate electrode composed of Al or a gate bus line is combined with a gate insulating film composed of an Al2O3 ALD film regarding the manufacturing method of a thin-film transistor matrix. CONSTITUTION:A gate electrode 2 at least the surface of which is constituted of Al and a gate bus line are formed on a transparent insulating substrate 1, a metal film having a thickness capable of befog changed into an insulator by oxidation is formed, the metal film is oxidized inside an atomic-layer deposition film formation apparatus or the metal film is oxidized inside an oxygen plasma ashing apparatus and the metal film is changed into an insulating metal oxide film. Then, an Al2O3 film IIB is laminated on it by an atomic-layer deposition method, a gate insulating film 11 is formed and, after that, an action semiconductor layer 4, a source electrode 7S, a drain electrode 7D, a drain bus line 8 and a pixel electrode 9 are formed sequentially.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a thin film transistor matrix suitable for use in a liquid crystal display panel driven by an active matrix driving method.

In a thin film transistor matrix used for active matrix driving of a liquid crystal display panel or the like, the gate insulating film has high density, high withstand voltage, high dielectric constant and low stress. And that the adhesion to the base electrode is good.

Therefore, atomic layer deposition (atomic la)
yer position (ALD) method,
Although a gate insulating film made of a laminated body of Al ₂ O ₃ atomic layers has been formed, many improvements still have to be made in order to use such a gate insulating film.

[0004]

2. Description of the Related Art For example, in a liquid crystal display panel driven by an active matrix driving method, thin film transistors are arranged in a matrix for individual pixels for dot display.
r: TFT) and each pixel has a memory function,
It has good contrast and enables display of multiple lines.

Such a liquid crystal display panel has a large number of gate bus lines and drain bus lines arranged in a matrix on a transparent insulating substrate such as glass so as to intersect in the X and Y directions, for example. Pixels corresponding to the selected TFTs are selectively driven by selectively applying a driving voltage to the TFTs arranged at the intersections of the gate bus lines and the drain bus lines. Is configured to display dots.

FIG. 3 is a cutaway side view of a main part for explaining a conventional TFT matrix. In the figure, 1 is a transparent insulating substrate made of, for example, glass, 2 is a gate electrode,
2A is, for example, a Ti film forming the gate electrode, 2B is, for example, an Al film forming the gate electrode, 3 is a gate insulating film, 3
A is a SiO ₂ film forming a gate insulating film, 3B is a SiN film forming a gate insulating film, 4 is an operating semiconductor layer made of amorphous silicon (a-Si), 5 is a channel protective film made of a SiN film, and 6S the n ⁺ source electrode contact layer made of -a-Si, 6D drain electrode contact layer composed of n ⁺ -a-Si, a source electrode 7S is made of Ti, 7D drain electrode made of Ti, the drain bus 8 Line, 8A is a Cr film forming a drain bus line, 8B is an Al film forming a drain bus line, and 9 is an indium tin oxide (ITO) film.
The pixel electrodes made of de) are respectively shown.

As is apparent from the figure, in this TFT matrix, a gate bus line connecting a large number of gate electrodes 2 and a drain bus line connecting a large number of drain electrodes 7D on the transparent insulating substrate 1. 8 are formed in a state of intersecting in the X direction and the Y direction via the gate insulating film 3 and the like, and TFTs are arranged in a matrix at a number of intersections thereof. The gate bus line connects a number of gate electrodes 2 and extends in the lateral direction of the drawing, that is, in the X direction, but it cannot be shown because of the cross section.

Drain bus line 8 through TFT
A pixel electrode 9 that contacts the source electrode 7S is formed on the opposite side. As the operating semiconductor layer 4, plasma chemical vapor deposition (plasma chemical vapor deposition) is performed.
In the case of using a-Si formed by applying the pour deposition (P-CVD) method, the gate insulating film 3
As such, a silicon nitride film, an oxynitride film, or the like, which is also formed by applying the P-CVD method, is used.

When the P-CVD method is applied, both the gate insulating film 3 and the operating semiconductor layer 4 can be continuously formed in the same growth chamber, so that the manufacturing process is simple, but the existence of the gate electrode 2 exists. For example, there is a problem that cracks are likely to occur due to insufficient step coverage of the underlying step, and sufficient insulation breakdown voltage or insulation resistance cannot be obtained.

Therefore, a technique using an ALD film as the gate insulating film 3 has been developed. The withstand voltage of the ALD film is higher than that of the silicon nitride film, and even when a high voltage is applied,
There is an advantage that the dielectric breakdown is unlikely to occur, and the dielectric constant is higher than that of the silicon nitride film, so that it is possible to form a thicker film, so that the withstand voltage can be increased.

[0011]

Generally, the gate electrode and the gate bus line are made of Al, and the ALD film forming the gate insulating film is made of Al ₂ O _3. Many. This is due to the good compatibility with Al and Al ₂ O _3, In this way, Al ₂ O ₃
Is superior in terms of withstand voltage as compared with the case where the gate insulating film made of the ALD film and the gate electrode made of another metal are combined.

However, when Al and Al ₂ O ₃ are used, Al abnormally grows in a protruding shape at the edge of the gate electrode or the gate bus line, and the gate insulating film becomes substantially thin at that portion. As a result, the withstand voltage decreases. Therefore, it is very difficult to realize a defect-free TFT matrix, and eventually a defect-free liquid crystal display panel, with good reproducibility.

According to the present invention, even if the gate electrode or gate bus line made of Al and the gate insulating film made of the ALD film of Al ₂ O ₃ are combined, the gate withstand voltage does not decrease and good TFT characteristics are obtained. Get it.

[0014]

According to many experiments conducted by the present inventors, a thin insulating metal oxide film is formed in advance after forming a gate electrode and a gate bus line and before forming an ALD film. It has been confirmed that by forming the above, the abnormal protrusion growth of Al can be suppressed during the formation of the ALD film.

As the insulating metal oxide film, Al, T
i, Ni, Cr, Ti containing Al, Ni containing Al, A
An oxide such as Cr containing 1 can be used. For example, when Ti containing Al, Ni containing Al, or the like is used, when the material film is formed by the ALD method, the substrate is heated to form H ₂ O while forming the film. Etc., a metal oxide film of Al, etc. can be obtained, and in the case of a metal not containing Al, it can be obtained by performing an oxidation treatment using an oxygen plasma ashing device. According to the experiments conducted by the present inventors, it has been found that the oxygen plasma ashing treatment of Al promotes abnormal growth of Al.

From the above, in the thin film transistor matrix and the manufacturing method thereof according to the present invention, (1) at least the surface is made of Al on the transparent insulating substrate (for example, the transparent insulating substrate 1 made of glass). Forming a configured gate electrode (eg gate electrode 2) and gate bus line, then forming a metal film of a thickness that can be made into an insulator by oxidation, and then said The metal film is oxidized in the atomic layer deposition film forming apparatus to form an insulating metal oxide film (for example, Al ₂ O ₃ film 11).
A) step, and subsequently, laminating an Al ₂ O ₃ thin film by the atomic layer deposition method in the atomic layer deposition film forming apparatus (for example, Al ₂ O ₃ film 11B).
To form a gate insulating film (for example, the gate insulating film 11), and then, an operating semiconductor layer (for example, the operating semiconductor layer 4), a source electrode (for example, the source electrode 7S), a drain electrode (for example, the drain electrode 7D), and a drain. ·bus·
Forming a line (for example, a drain bus line 8) and a pixel electrode (for example, a pixel electrode 9) in that order and completing the process.

(2) In the above (1), the metal film having a thickness that can be made into an insulator by oxidation contains Al and is converted into an insulating metal oxide film by thermal oxidation. Or

(3) In the above (1), the metal film having a thickness that can be made into an insulator by oxidation does not contain Al and is converted into an insulating metal oxide film by oxidation according to the oxygen plasma ashing method. Is characterized by being

(4) In the above (2), the thickness of the metal film containing Al is 50 [Å] or less, or

(5) In the above (3), the metal film not containing Al has a thickness of 300 [Å] or less.

[0021]

By adopting the above means, the gate electrode and the gate bus line made of Al are formed on the transparent insulating substrate, and the gate insulating film made of Al ₂ O ₃ is formed by the ALD method to cover the gate electrode and the gate bus line. Even if the film is formed, the protruding abnormal growth of Al does not appear at the edges of the gate electrode and the gate bus line. Therefore, the gate electrode and the gate insulating film on the gate bus line can maintain a predetermined thickness, that is, can maintain the required withstand voltage, and the withstand voltage locally decreases to reduce the TFT. There is no fear that the gyro will not operate normally. As a result, a defect-free TFT matrix, and consequently a defect-free liquid crystal display panel, can be obtained with a high yield.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a T made according to an embodiment of the present invention.
FIG. 4 is a cutaway side view of a main part for explaining an FT matrix,
The same symbols as those used in FIG. 3 represent the same parts or have the same meanings.

The TFT matrix shown is different from the conventional example described with reference to FIG. 3 in that the conventional gate insulating film 3 shown in FIG. The film 11 is an Al ₂ O ₃ film obtained by oxidizing an Al film formed by a sputtering method.
Film 11A and Al ₂ O ₃ film 11B formed directly by ALD method
It consists of

To manufacture the TFT matrix shown in FIG. 1, the following steps can be taken, for example. (1) By applying the sputtering method, T having a thickness of 50 [nm] is formed on the transparent insulating substrate 1 made of glass.
An i film 2A and an Al film 2B having a thickness of 50 nm are sequentially formed. (2) Patterning of the Al film 2B formed in step (1) is performed by applying a resist process in the lithography technique and a wet etching method using an etchant of phosphoric acid, nitric acid, or acetic acid as a solution. To do.

(3) Reactive ion etching using a CCl ₄ gas as an etching gas while leaving the mask used in the step (3).
The Ti film 2A formed in the step (1) is patterned by applying the tching: RIE method. By going through the steps (2) and (3), the gate electrode 2
And gate bus lines (not shown) are formed.
Although the gate bus line cannot be shown in the drawing because of the cross section, it extends in the lateral direction of the drawing, that is, in the X direction.

(4) An Al film having a thickness of 4 nm is formed on the entire surface by applying the sputtering method. (5) In the ALD film forming apparatus, while supplying H ₂ O, the transparent insulating substrate 1 is heated at a temperature of 500 for about 20 minutes.
Heat to [° C]. As the ALD film forming apparatus, the one disclosed in JP-A-3-234025 may be used. By this treatment, the Al film formed in the step (4) is converted into the Al ₂ O ₃ film 11A which is an insulating metal oxide film.

(6) Similarly, in the ALD film forming apparatus, by applying the ALD method, a thickness of, for example, 400
An Al ₂ O ₃ film 11B of [nm] is formed. ALD
The film formation by the method will be described later in detail. Al ₂ O ₃ film 11 formed in steps (5) and (6)
It goes without saying that B and 11A become the gate insulating film 11.

(7) In the P-CVD film forming apparatus,
An operating layer 4 made of a-Si having a thickness of 10 nm, for example.
A channel protective film 5 made of SiN and having a thickness of 100 nm, for example, is sequentially formed. (8) The channel protection film 5 formed in the step (7) is patterned by applying a resist process in the lithography technique and a wet etching method using a buffer hydrofluoric acid as an etchant. Leaving only the portion facing the gate electrode 2.

(9) In the P-CVD film forming apparatus,
An n ⁺ -a-Si film having a thickness of, for example, 50 [nm] is grown. (10) A Ti film having a thickness of, for example, 100 [nm] is formed by applying the sputtering method.

(11) The Ti film formed in the step (10) is patterned by applying a resist process in the lithography technique and an RIE method using a CCl ₄ gas as an etching gas. Then, the source electrode 7S and the drain electrode 7D are formed.

(12) By leaving the mask used in the step (11) as it is and applying the RIE method using the etching gas CF ₄ type gas, the n ⁺ -a- formed in the step (9) is applied. Operation layer 4 made of Si film and a-Si
Patterning is performed. By going through this step, the source electrode contact layer 6S and the drain electrode contact layer 6 made of n ⁺ -a-Si
D is formed, and the operating layer 4 made of a-Si is TF.
It becomes independent for each T.

(13) A Cr film 8A having a thickness of 100 nm and an Al film 8B having a thickness of 200 nm are formed by applying the sputtering method. (14) The resist process and etchant used in lithography technology are phosphoric acid, nitric acid, acetic acid-based solution (Al
) And (ammonium nitrate + perchloric acid) type solution (C
The drain bus line 8 is formed by patterning the Al film 8B and the Cr film 8A by applying a wet etching method (for r).

(15) An ITO film having a thickness of, for example, 200 [nm] is formed by applying the sputtering method. (16) The ITO film formed in the step (15) is patterned by applying a resist process in the lithography technique and a wet etching method using an etchant as a mixed solution of (HCl + HNO ₃ ). 9 is formed.

In the TFT matrix thus produced, no abnormal protrusion growth of Al occurs at the edges of the gate electrode 2 and the gate bus line, and therefore, the gate withstand voltage is practically sufficient. It goes without saying that it is extremely expensive.

Now, by applying the ALD method here, Al ₂ O
_{3 The} process of forming the film 11B will be described in detail. FIG. 2 is a perspective view of a main part of the ALD film forming apparatus disclosed in JP-A-3-234025.

In the figure, 21 is a fan-shaped reaction chamber, 2
2 is a barrier gas inlet pipe, 23 is a trimethylaluminum (TMA: Al (CH ₃ ) ₃ ) vapor inlet pipe, 24 is a steam (H ₂ O) + Ar gas inlet pipe, 25 to 27 are valves, 28 is a TMA container, 29 is heater, 30 is orifice valve, 31 is turbo molecular pump, 32 is barrier gas flow, 33 is TMA vapor flow, 34 is steam + Ar gas flow, 35 is substrate, 36 is thin film forming region Are shown respectively.

As is apparent from the figure, in this ALD film forming apparatus, an air supply port of the barrier gas supply pipe 22 is provided at the approximate center of the fan-shaped curved surface of the reaction chamber 21, and it is opposite to the air supply port. An intake port of a turbo molecular pump 31 for exhaust is provided on the side, and the substrate 35 is a barrier layer made of Ar gas, for example.
It can be moved left and right over the gas flow 32. Therefore, the surface of the substrate 35 can be selectively exposed to either TMA vapor supplied from the inlet pipe 23 or water vapor + Ar gas supplied from the inlet pipe 24.

When forming a film, the atmosphere is first set to 5 × 10 ⁻⁷ [Tor] by the turbo molecular pump 31.
After evacuation to about [r], the valve 27 is opened while the substrate 35 arranged in the thin film formation region 36 is heated to a temperature of 500 [° C.], and steam is flown from the inlet pipe 24 to preliminarily form it. A metal thin film, for example, an Al film is oxidized. At this time, the pressure is adjusted to about 1 [Tor] by the orifice valve 30.
r]. Next, after closing the valve 27, the valve 25 is opened to allow a steady flow of the barrier gas of Ar to flow and the orifice valve 30 to be adjusted so that the pressure in the reaction chamber 21 becomes 0.01 [Torr]. To

Next, the TMA container 28 is heated by the heater 29 to generate TMA vapor, and the valve 26 is opened to open the TMA.
The TMA vapor is fed into the reaction chamber 21 via the vapor feed pipe 23. Next, with the water container (not shown) kept at 20 [° C.], the valve 27 was opened to open the steam + Ar gas inlet pipe 24.
Water vapor is fed into the reaction chamber 21 via. Since the TMA vapor and the water vapor are separated by the steady flow of the barrier gas, they are not mixed with each other. Also, the reaction chamber 21 at this time
The degree of vacuum inside is maintained at 0.01 [Torr].

Next, the substrate 35 is rocked to the left and right at a speed that does not disturb the steady flow of the barrier gas, for example, a cycle of reciprocation of 1 second, and the substrate 35 is alternately exposed to the TMA vapor atmosphere and the vapor atmosphere. This reciprocation is repeated 5400 times, and an Al ₂ O ₃ film having a thickness of 400 nm and obtained by the ALD method is obtained under the conditions of the film formation temperature of 500 ° C. and the film formation rate of about 45 [Å]. In this case, the flow rate ratio of both vapors was TMA vapor flow rate: water vapor flow rate = 2: 5.

In the present embodiment, the reason why the thickness of the Al film grown at one time is 45 [Å] is that the Al film is converted into an Al ₂ O ₃ film by oxidation in the ALD film forming apparatus, The film thickness of the Al film that can make the sheet resistance infinite is about 50.
[Å] It depends on the following. Also, when oxygen plasma ashing was performed to make Ni an insulating metal oxide film, the film thickness at which the sheet resistance becomes infinite is about 300 [Å].
It was below.

[0042]

In the method of manufacturing a thin film transistor matrix according to the present invention, a gate electrode and a gate bus line having at least a surface made of Al are formed on a transparent insulating substrate, and oxidation is performed by oxidation. An insulating metal oxide film is formed by forming a metal film having a thickness that can be used as an insulator and oxidizing the metal film in an atomic layer deposition film forming apparatus or by oxygen plasma ashing treatment. Then, in the atomic layer deposition film forming apparatus, an Al ₂ O ₃ thin film is laminated by an atomic layer deposition method to form a gate insulating film, and an operating semiconductor layer, a source electrode and a drain electrode, The drain bus line and the pixel electrode are sequentially formed and completed.

By adopting the above structure, the gate electrode and the gate bus line made of Al are formed on the transparent insulating substrate, and the gate insulating film made of Al ₂ O ₃ is formed by the ALD method to cover the gate electrode and the gate bus line. Even if the film is formed, the protruding abnormal growth of Al does not appear at the edges of the gate electrode and the gate bus line. Therefore, the gate electrode and the gate insulating film on the gate bus line can maintain a predetermined thickness, that is, can maintain the required withstand voltage, and the withstand voltage locally decreases to reduce the TFT. There is no fear that the gyro will not operate normally. As a result, a defect-free TFT matrix, and consequently a defect-free liquid crystal display panel, can be obtained with a high yield.

[Brief description of drawings]

FIG. 1 is a cutaway side view of a main part for explaining a TFT matrix formed according to an embodiment of the present invention.

FIG. 2A disclosed in Japanese Patent Application Laid-Open No. 3-234025
It is a principal part slope explanatory drawing showing an LD film-forming apparatus.

FIG. 3 is a cutaway side view of a main part for explaining a conventional TFT matrix.

[Explanation of symbols]

1 Transparent Insulating Substrate Made of, for example, Glass 2 Gate Electrode 2A Gate Electrode Constituting Ti Film 2B Gate Electrode Comprising Al Film 3 Gate Insulating Film 3A Gate Insulating SiO ₂ Film 3B Comprising Gate Insulating Film SiN film 4 Operation semiconductor layer made of amorphous silicon (a-Si) 5 Channel protection film made of SiN film 6S n ⁺ -a-Si source electrode contact layer 6D n ⁺ -a-Si drain electrode contact Layer 7S Source electrode made of Ti 7D Drain electrode made of Ti 8 Drain bus line 8A Cr film forming a drain bus line 8B Al film forming a drain bus line 9 Pixel electrode made of ITO 11 Gate insulation Al obtained by oxidizing the film 11A Al film ₂ O ₃ film 1 Al ₂ O ₃ film directly formed by B ALD method

Claims (5)

[Claims] 1. A transparent insulating substrate having at least a surface made of Al.
A step of forming a gate electrode and a gate bus line, which are composed of, and a step of forming a metal film having a thickness capable of becoming an insulator by oxidation, and then forming the metal film into an atomic layer. A step of oxidizing and converting into an insulating metal oxide film in a deposition film forming apparatus, and subsequently, an Al ₂ O ₃ thin film is formed in the atomic layer deposition film forming apparatus by an atomic layer deposition method. A step of forming a gate insulating film by laminating, an operation semiconductor layer, a source electrode and a drain electrode,
A method of manufacturing a thin film transistor matrix, comprising the steps of sequentially forming and completing a drain bus line and a pixel electrode. 2. The thin film transistor matrix according to claim 1, wherein the metal film having a thickness capable of being made into an insulator by oxidation contains Al and is converted into an insulating metal oxide film by thermal oxidation. Production method. 3. A metal film having a thickness that can be made into an insulator by oxidation is free of Al and is converted into an insulating metal oxide film by oxidation by an oxygen plasma ashing method. 1. A method of manufacturing a thin film transistor matrix according to 1. 4. The method of manufacturing a thin film transistor matrix according to claim 2, wherein the thickness of the metal film containing Al is 50 [Å] or less. 5. The thickness of the metal film containing no Al is 300.
[Å] The method of manufacturing a thin film transistor matrix according to claim 3, wherein: