JP2009038284A - Thin film transistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin film transistor having excellent performances inexpensively with extremely little defective article generation. <P>SOLUTION: The thin film transistor is composed by forming a gate electrode film 2 on a glass substrate 1, forming a silicon nitride film 3 on the glass substrate 1 and the gate electrode film 2, forming an amorphous Si film 4 on the silicon nitride film 3, forming a drain electrode film 5 and a source electrode film 6 both composed of pure copper having the base layer of an oxygen-containing copper film 15 through a barrier film on the amorphous Si layer 4, and forming a silicon nitride film 3' on the amorphous Si film 4, the drain electrode film 5 and the source electrode film 6. In the thin film transistor, the barrier film is constituted of an oxygen-containing copper alloy film 19 consisting of copper, silicon and oxygen. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is a thin film transistor in which a barrier film is formed between an amorphous silicon film and a drain electrode film, and further a barrier film is formed between an amorphous silicon film and a source electrode. The present invention relates to a thin film transistor made of an oxygen-containing copper alloy film made of copper, silicon and oxygen.

As a flat panel display using a thin film transistor driven by an active matrix system, a liquid crystal display, a plasma display, an organic EL display, an inorganic EL display, and the like are known. In these flat panel displays using thin film transistors, wiring made of a metal film is formed in close contact with the surface of the glass substrate, and thin film transistors are provided at the intersections of the grid wiring made of the metal film.
In this thin film transistor, a gate electrode film 2 made of a metal film is formed on the surface of a glass substrate 1 as shown in the schematic sectional view of FIG. 7, and the gate electrode film 2 and the glass substrate 1 are formed on the gate electrode film 2. A silicon nitride (SiNx) film 3 is formed, and further an amorphous Si film 4 is formed on the silicon nitride (SiNx) film 3, both of which are formed on the amorphous Si film 4 via a barrier film 7. A drain electrode film 5 and a source electrode film 6 made of pure copper are formed, and a silicon nitride (SiNx) film 3 ′ is formed so as to cover the entire surface of the amorphous Si film 4, the drain electrode film 5 and the source electrode film 6. It has a laminated film structure.
In order to manufacture a thin film transistor having such a laminated film structure, first, a gate electrode film 2 made of pure copper is formed on the surface of a glass substrate 1 as shown in the sectional view of FIG. A silicon nitride (SiNx) film 3 is formed on the glass substrate 1, an amorphous Si film 4 is formed on the silicon nitride (SiNx) film 3, and a barrier film 7 is formed on the amorphous Si film 4. Then, a pure copper film 8 is formed so as to cover the entire surface of the silicon nitride (SiNx) film 3 and the barrier film 7 to produce a laminate 9.
Next, the barrier film 7 and the pure copper film 8 of the laminated body 9 are wet-etched by photolithography (photolithography) to expose a part of the amorphous Si film 4 covered with the barrier film 7 and the pure copper film 8, and the barrier film. 7. The conventional thin film transistor intermediate 10 shown in the cross-sectional view of FIG. 9 is formed by forming the drain electrode film 5 and the source electrode film 6, and then silicon nitride ( A conventional thin film transistor shown in the cross-sectional view of FIG. 7 is fabricated by chemical vapor deposition of a (SiNx) film 3 ′ at around 300 ° C. Although not illustrated in FIGS. 7 to 9, a copper film containing oxygen (oxygen-containing copper) is used as a base layer for the drain electrode film 5 and the source electrode film 6 in order to improve the adhesion between the drain electrode film 5 and the source electrode film 6. It is also known to form a film.
Since the silicon nitride (SiNx) film 3 ′ is generally formed by chemical vapor deposition at about 300 ° C., when the silicon nitride (SiNx) film 3 ′ is formed, the Si of the amorphous Si film 4 is a drain made of pure copper. Diffusion into the electrode film 5 and the source electrode film 6 causes the specific resistance of the drain electrode film 5 and the source electrode film 6 to increase greatly.
During the chemical vapor deposition of the silicon nitride (SiNx) film 3 ′, Si in the amorphous Si film 4 diffuses into the drain electrode film 5 and the source electrode film 6 to increase the specific resistance of the drain electrode film 5 and the source electrode film 6. In order to prevent this, a barrier film 7 is formed between the amorphous Si film 4 and the drain electrode film 5 and between the amorphous Si film 4 and the source electrode film 6. As this barrier film 7, a Mo or Mo alloy film or a Ti or Ti alloy film is usually used. Even if the thin film transistor is heated after that, the Si of the amorphous Si film 4 is drained. It also acts to prevent the specific resistance of the drain electrode film 5 and the source electrode film 6 from increasing by diffusing into the electrode film 5 and the source electrode film 6 (see Patent Document 1).
JP 2004-163901 A

  However, when a Mo film, a Mo alloy film, or a Ti or Ti alloy film is used as the barrier film 7, the barrier film 7 made of Mo, Ti, or an alloy film thereof and the pure copper film 8 are made of different metals, and thus When wet etching is performed on a composite metal film in contact with different metals, a local battery is formed when wet etching is performed, and a contact end portion between the barrier film 7 and the drain electrode film 5 and a contact end portion between the barrier film and the source electrode film 6 are formed. As shown in FIG. 10, which is a partially enlarged view of FIG. 9, the etching is performed preferentially, and the contact end portion between the barrier film 7 and the drain electrode film 5 and the contact end portion between the barrier film 7 and the source electrode film 6 are deep. A recess 11 is formed, and the recess 11 is formed deep along the boundary between the barrier film 7 and the drain electrode film 5 and the boundary between the barrier film 7 and the source electrode film 6. The wet etching solution penetrates into the recess 11, and the wet etching solution penetrated into the recess 11 during the wet etching is not discharged even if it is washed and dried, and silicon nitride (SiNx is not discharged from the recess 11. ) When the film 3 ′ is chemically vapor deposited at around 300 ° C., the wet etching solution is evaporated during the chemical vapor deposition, and the silicon nitride (SiNx) film 3 ′ is swollen to partially adhere to the silicon nitride (SiNx) film 3 ′. This may cause the thin film transistor to be defective.

Therefore, the present inventors have studied to produce a thin film transistor by preventing the formation of recesses during the wet etching. as a result,
(A) A two-layer composite film composed of a silicon oxide film and an oxygen-containing copper film (hereinafter referred to as oxygen-containing copper film) is a Mo film or Mo alloy film or Ti or Ti alloy conventionally known as a barrier film. In the thin film transistor intermediate body, which has the same effect as the film, a laminated body in which a pure copper film is coated on the oxygen-containing copper film in the two-layer composite film, and this laminated body is wet-etched. A recess as shown in FIG. 10 is not generated.
(B) In addition, a silicon nitride film (SiN) is formed on a thin film transistor intermediate obtained by wet etching after forming a pure copper film on the oxygen-containing copper film in the two-layer composite film composed of the silicon oxide film and the oxygen-containing copper film. When the chemical vapor deposition of the SiNx) film 3 ′ is performed at around 300 ° C., an oxygen-containing copper alloy film (hereinafter referred to as an oxygen-containing copper alloy film) made of Cu, Si and oxygen is formed between the amorphous Si film and the oxygen-containing copper film during the chemical vapor deposition. And the Si of the amorphous Si film diffuses and reaches the drain electrode film and the source electrode film during chemical vapor deposition and does not increase the specific resistance of the drain electrode film and the source electrode film.
(C) The oxygen-containing copper alloy film made of Cu, Si and oxygen formed between the amorphous silicon film and the oxygen-containing copper film during the chemical vapor deposition is a conventional Mo film or Mo alloy film or Ti or Ti alloy film. Even if the thin film transistor has the same barrier property, the Si of the amorphous Si film diffuses into the drain electrode film and the source electrode film and the specific resistance of the drain electrode film and the source electrode film Will not increase,
(D) The oxygen-containing copper alloy film composed of copper, silicon and oxygen acting as the barrier film is oxygen: 20 atomic% or more, and the thickness is preferably in the range of 1 to 15 nm. The research results were obtained.

This invention was made based on the above research results,
(1) A gate electrode film is formed on a glass substrate, a silicon nitride film is formed on the glass substrate and the gate electrode film, an amorphous Si film is formed on the silicon nitride film, and the amorphous Si film A drain electrode film and a source electrode film made of pure copper each having an underlayer of an oxygen-containing copper film are formed on a silicon nitride film on the amorphous Si film, the drain electrode film, and the source electrode film. In a thin film transistor formed by coating a film,
The barrier film is a thin film transistor composed of an oxygen-containing copper alloy film made of copper, silicon and oxygen,
(2) The thin film transistor according to (1), wherein the oxygen-containing copper alloy film made of copper, silicon, and oxygen contains oxygen: 20 atomic% or more,
(3) The thin film transistor according to (2), wherein the oxygen-containing copper alloy film made of copper, silicon, and oxygen has a thickness of 1 to 15 nm.
(4) A gate electrode film is formed on the glass substrate, a silicon nitride film is formed on the glass substrate and the gate electrode film, an amorphous silicon film is formed on the silicon nitride film, and the amorphous silicon film A thin film transistor intermediate formed by forming a silicon oxide film on the silicon oxide film, forming an oxygen-containing copper film on the silicon oxide film, and forming a drain electrode film and a source electrode film on the oxygen-containing copper film; It has the characteristics.

The thin film transistor of the present invention can be produced by the following method. First, as shown in the sectional view of FIG. 1, a gate electrode film 2 made of pure copper is formed on the surface of a glass substrate 1, and a silicon nitride (SiNx) film 3 is formed on the gate electrode film 2 and the glass substrate 1. Then, an amorphous Si film 4 is formed on the silicon nitride (SiNx) film 3 to produce a first stacked body 13.
Next, as shown in the cross-sectional view of FIG. 2, a silicon oxide film 12 is formed on the amorphous Si film 4 of the first stacked body 13 to produce a second stacked body 14. This silicon oxide film 12 is placed in a sputtering apparatus using the first laminate 13 of FIG. 1 as a substrate, and is sputtered while holding the atmosphere in the sputtering apparatus to be an inert gas atmosphere containing oxygen. Can be formed.
Next, as shown in the cross-sectional view of FIG. 3, an oxygen-containing copper film 15 containing oxygen is formed on the second stacked body 14 to produce a third stacked body 16. This oxygen-containing copper film 15 uses a pure copper target, is placed in a sputtering apparatus using the second laminated body 13 of FIG. 2 as a substrate, and is sputtered while holding the atmosphere in an inert gas atmosphere containing oxygen. Can be formed.
Further, as shown in FIG. 4, a pure copper film 8 is formed on the third stacked body 16 to produce a fourth stacked body 17. The pure copper film 8 can be formed by using a pure copper target, placing the third laminated body 16 of FIG. 3 as a substrate in a sputtering apparatus, and performing sputtering in an inert gas atmosphere.
A part of the silicon oxide film 12 on the amorphous Si film 4 covered with the oxygen-containing copper film 15 and the pure copper film 8 of the fourth laminated body 17 thus obtained is exposed, and the drain electrode film 5 and the source are exposed. By forming the electrode film 6, the thin film transistor intermediate body 18 shown in the cross-sectional view of FIG. In order to form the drain electrode film 5 and the source electrode film 6 by exposing a part of the silicon oxide film 12, the oxygen-containing copper film 15 and the pure copper film 8 are prepared by wet etching using photolithography. Can do. A thin film transistor of the present invention can be manufactured by forming a silicon nitride (SiNx) film 3 ′ on the thin film transistor intermediate 18. The formation of the silicon nitride (SiNx) film 3 ′ is achieved by chemical vapor deposition of the silicon nitride (SiNx) film 3 ′ at around 300 ° C. in the same manner as in the prior art. During the chemical vapor deposition of the silicon nitride (SiNx) film 3 ′, an oxygen-containing copper alloy film 19 made of Cu, Si and oxygen is formed at the boundary between the amorphous Si film 4 and the oxygen-containing copper film 15, and silicon nitride (SiNx) During the chemical vapor deposition of the film 3 ′, Si of the amorphous Si film does not diffuse into the drain electrode film 5 and the source electrode film 6 to increase the specific resistance of the drain electrode film 5 and the source electrode film 6. In addition, the oxygen-containing copper alloy film 19 made of Cu, Si and oxygen formed during the chemical vapor deposition of the silicon nitride (SiNx) film 3 ′ is excellent even if the thin film transistor is heated thereafter. The barrier property is exhibited and Si of the amorphous Si film 4 is prevented from diffusing into the drain electrode film 5 and the source electrode film 6, and the specific resistance of the drain electrode film 5 and the source electrode film 6 is not increased.

  The reason why the oxygen and the film thickness contained in the oxygen-containing copper alloy film composed of Cu, Si and oxygen that act as a barrier film of the thin film transistor of the present invention are limited as described above will be described.

(A) Oxygen content of oxygen-containing copper alloy film:
Even if oxygen contained in an oxygen-containing copper alloy film made of Cu, Si and oxygen is contained in an amount of less than 20 atomic%, it is not preferable because diffusion of Si cannot be sufficiently prevented. Therefore, the oxygen contained in the oxygen-containing copper alloy film made of Cu, Si and oxygen formed in the thin film transistor of the present invention is determined to be 20 atomic% or more (preferably 20 to 66 atomic%).

(B) Thickness of oxygen-containing copper alloy film:
If the thickness of the oxygen-containing copper alloy film made of Cu, Si and oxygen is less than 1 nm, it is not preferable because Si of the amorphous Si film cannot be prevented from diffusing into the drain electrode film and the source electrode film. Even if the thickness exceeds 15 nm, no particular effect can be obtained. Therefore, the thickness of the oxygen-containing copper alloy film made of Cu, Si and oxygen is set to 1 to 15 nm.

  The thin film transistor of the present invention uses a single pure copper target and can be formed with a barrier film, a drain electrode film, and a source electrode film only by changing the sputtering atmosphere. A flat panel that has excellent performance at low cost with very few defects in the thin film transistor produced because there is no formation of a recess at each junction end of the electrode film and the barrier film and the source electrode film. It is possible to provide an excellent effect such as providing a display.

Example An amorphous Si film having a thickness of 200 nm was formed on the entire surface of a glass substrate (Corning 1737 glass substrate having dimensions of 50 mm in length, 50 mm in width, and 0.7 mm in thickness). This amorphous Si film deposited to a thickness of 200 nm is set as a substrate in a sputtering apparatus, and a 6-inch diameter target made of oxygen-free copper with a purity of 4N is set in the sputtering apparatus as a power source for the sputtering apparatus. A direct current method was employed, and the vacuum vessel of the sputtering apparatus was evacuated until the ultimate vacuum was 4 × 10 ⁻⁵ Pa. Next, Ar gas containing oxygen in the ratio shown in Table 1 was flowed into the vacuum vessel to set the sputtering atmosphere pressure to 0.67 Pa, and then the output: 600 W with the shutter installed between the target and the substrate closed. The silicon oxide film was formed by discharging for the time shown in FIG.
Next, the shutter was opened while maintaining the atmosphere, and sputtering was continued to form an oxygen-containing copper film having a width of 20 mm and a length of 40 mm on the silicon oxide film.
Next, the supply of oxygen is stopped, and an oxygen-free copper film is formed with Ar gas alone at a pressure of 0.67 Pa until a thickness of 250 nm is reached, thereby forming a width: 20 mm, length on the oxygen-containing copper film. The present invention thin film transistor intermediate test pieces 1 to 7 and the comparative thin film transistor intermediate test piece 1 were prepared by forming an oxygen-free copper film having a size of 40 mm.

Oxygen-containing copper film in the thin film transistor intermediate test pieces 1 to 7 and comparative thin film transistor intermediate test piece 1 of the present invention by wet etching the thin film transistor intermediate test pieces 1 to 7 of the present invention and the comparative thin film transistor intermediate test piece 1 And an oxygen-free copper film with a window of 10 mm in length and 10 mm in width, and the cross section of the interface between the wet-etched oxygen-containing copper film and the oxygen-free copper film is magnified 5 million times with TEM Table 1 shows the results of the observation of the presence or absence of recesses formed on the surface.

Next, plasma CVD is performed while maintaining the wet-etched thin film transistor intermediate test pieces 1 to 7 of the present invention and the comparative thin film transistor intermediate test piece 1 at a temperature of 300 ° C., and a SiNx insulating film having a thickness of 200 nm. After that, the SiNx insulating film was peeled off by dry etching, and this peeled portion was observed with a TEM (transmission electron microscope). As a result, Cu, Si, and oxygen were formed at the boundary between the silicon oxide film and the oxygen-containing copper film. It was found that an oxygen-containing copper alloy film made of The maximum oxygen content and thickness of the oxygen-containing copper alloy film made of Cu, Si and oxygen were measured, and the results are shown in Table 1.
The maximum oxygen content of the oxygen-containing copper alloy film made of Cu, Si and oxygen is an energy dispersive X-ray analyzer manufactured by Nolan Co., Ltd., which is mounted on a transmission electron microscope (TEM) manufactured by JEOL Ltd. It was measured with (EDS) Voyager. The acceleration voltage was 200 kV.
Further, the oxygen content is measured by an EDS attached to the TEM in the film thickness direction of the oxygen-containing copper alloy film made of Cu, Si and oxygen, and the oxygen content is made of Cu, Si and oxygen having an oxygen content of 20 atomic% or more. The thickness of the containing copper alloy film was the thickness of the oxygen-containing copper alloy film made of Cu, Si and oxygen.
Further, the barrier property of the composite film made of silicon oxide and oxygen-containing copper film was evaluated by measuring the specific resistance of the oxygen-free copper film after forming the SiNx insulating film by a four-probe method.

Thickness: 50 nm by sputtering on the Si thin film on the glass substrate (vertical: 50 mm, horizontal: 50 mm, thickness: 0.77 glass substrate having dimensions of 0.7 mm) produced in the conventional example. Conventionally, a composite film composed of a Mo thin film and an oxygen-free copper film is formed by depositing an oxygen-free copper film having a thickness of 250 nm on the Mo thin film under the same conditions as in the embodiment. A thin film transistor intermediate test piece 1 was prepared. The obtained composite film of the conventional thin film transistor intermediate test piece 1 was wet-etched so as to open a window having dimensions of 10 mm in length and 10 mm in width, and the cross section of the interface between the oxygen-containing Cu film and the oxygen-free copper film was measured with TEM. As a result of observing the image by magnifying it 5 times, it was found that a concave portion was formed at the contact end portion of the composite film, and the result is shown in Table 1.
Next, this wet-etched conventional thin film transistor intermediate test piece 1 was used as a substrate, and plasma CVD was performed while maintaining the substrate at a temperature of 300 ° C. to form a SiNx insulating film having a thickness of 200 nm.

From the results shown in Table 1, the specific resistance of the oxygen-free copper film after the formation of the SiNx insulating film of the thin film transistor intermediate test pieces 1 to 7 of the present invention is as follows. Since the specific resistance of the oxygen-free copper film after film formation is almost the same, the composite film composed of the silicon oxide film and the oxygen-containing copper film is the same as the Mo, Ti and their alloy films of the conventional thin film transistor intermediate test piece 1. Although it has the same barrier property, it can be seen that the conventional thin film transistor intermediate test piece 1 is formed with a recess during wet etching. Further, it can be seen that the comparative thin film transistor intermediate test piece 1 having a value outside the range of the present invention increases the specific resistance due to the diffusion of Si into the oxygen-free copper film.

It is a section schematic explanatory view of the 1st layered product. It is a section schematic explanatory view of the 2nd layered product. It is a cross-sectional schematic explanatory drawing of a 3rd laminated body. It is a section schematic explanatory view of the 4th layered product. It is a cross-sectional schematic explanatory drawing of the thin-film transistor intermediate body of this invention. It is a cross-sectional schematic explanatory drawing of the thin-film transistor of this invention. It is a cross-sectional schematic explanatory drawing for demonstrating the principal part of the conventional thin-film transistor. It is a cross-sectional schematic explanatory drawing for demonstrating the principal part of the conventional laminated body. It is a cross-sectional schematic explanatory drawing of the conventional thin-film transistor intermediate body. FIG. 10 is a partially enlarged schematic sectional explanatory view of FIG. 9.

Explanation of symbols

1: glass substrate, 2: gate electrode, 3: SiNx film, 3 ′: SiNx film, 4: amorphous Si film, 5: drain electrode, 6: source electrode, 7: barrier layer, 8: pure copper film, 9: laminated , 10: conventional thin film transistor intermediate, 11: recess, 12: silicon oxide film, 13: first laminate, 14: second laminate, 15: oxygen-containing copper film, 16: third laminate, 17 : 4th laminated body, 18: Thin-film transistor intermediate body of this invention, 19: Oxygen-containing copper alloy film which consists of copper, silicon, and oxygen, 20: Thin-film transistor of this invention

Claims (4)

Forming a gate electrode film on the glass substrate; forming a silicon nitride film on the glass substrate and the gate electrode film; forming an amorphous Si film on the silicon nitride film; and A drain electrode film and a source electrode film made of pure copper each having an underlayer of an oxygen-containing copper film are formed through a barrier film, and a silicon nitride film is coated on the amorphous Si film, the drain electrode film, and the source electrode film In the formed thin film transistor,
The thin film transistor according to claim 1, wherein the barrier film is composed of an oxygen-containing copper alloy film made of copper, silicon and oxygen. 2. The thin film transistor according to claim 1, wherein the oxygen-containing copper alloy film made of copper, silicon, and oxygen contains oxygen: 20 atomic% or more. 2. The thin film transistor according to claim 1, wherein the oxygen-containing copper alloy film made of copper, silicon and oxygen has a thickness in a range of 1 to 15 nm. Forming a gate electrode film on the glass substrate; forming a silicon nitride film on the glass substrate and the gate electrode film; forming an amorphous silicon film on the silicon nitride film; and A thin film transistor intermediate comprising a silicon oxide film, an oxygen-containing copper film formed on the silicon oxide film, and a drain electrode film and a source electrode film formed on the oxygen-containing copper film body.

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