JP3164756B2 - Method of forming multilayer thin film circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a multilayer thin film circuit, and more particularly to a method for forming a multilayer thin film circuit which does not cause a problem such as disconnection in the thin film circuit.

[0002]

2. Description of the Related Art A conventional multilayer thin film circuit is shown in FIG. FIG.
Among them, 1 is a substrate made of glass, ceramic, or the like, 2 is a first thin film layer formed on the substrate 1, and 4 is a resist film formed on the first thin film layer. In such a conventional multilayer thin film circuit, the first thin film layer 2 composed of a metal wiring pattern or the like is formed so that its cross-sectional shape becomes trapezoidal as shown in FIG.

The patterning of the first thin film layer 2 is performed by a dry etching method using a resist receding method. That is, the first thin film layer 2 composed of a metal wiring pattern or the like is etched with an etching gas such as SF ₆ or CF ₄ , and the resist film 3 is etched with an O ₂ gas added to the etching gas. The thin film layer 2 is formed so that the cross-sectional shape becomes trapezoidal. The taper angle θ formed between the side surface portion 2b of the first thin film layer 2 and the substrate 1
₁ is determined by the ratio between the etching rate of the material forming the first thin film layer 2 and the etching rate of the resist film 4. That is, when the etching rate of the resist film 4 becomes relatively large, the taper angle θ ₁ of the side surface portion 2b of the first thin film layer 2 becomes small, and when the etching rate of the resist film 4 becomes relatively small, the first taper angle theta ₁ of the side portion 2b of the thin-film layer 2 increases.

[0004]

In such a multilayer thin film circuit, it is desired to increase the taper angle θ ₁ in order to reduce the wiring width of the first thin film layer 2. _{When 1} is increased, the angle θ ₃ formed between the upper surface 2a and the side surface 2b of the thin film layer 2 becomes smaller and the corner becomes steeper. Therefore, as shown in FIG. When the insulating film 3 and the like are formed, there is a problem that the step coverage of the insulating film 3 is poor, and the breakdown voltage of the insulating film 3 is reduced.

Further, when an alignment film (not shown) made of, for example, polyimide used for a liquid crystal display device is formed on the insulating film 3 and rubbing is performed, there is a problem that the alignment film is peeled off. Was.

Further, when the first thin film layer 2 is formed of an insulating film and a conductive film 3 or the like is formed thereon, the step coverage of the conductive film 3 is poor, and disconnection of the conductive film 3 occurs. There was a problem of doing.

[0007] The present invention has been made in view of such problems of the prior art, and has been made to improve the step coverage of a second thin film layer formed on a first thin film layer.
It is an object of the present invention to provide a method of forming a multilayer thin film circuit in which a breakdown voltage of a second thin film layer is reduced, an upper layer film is peeled off, and disconnection is prevented.

[0008]

According to a first aspect of the present invention, there is provided a method for forming a multilayer thin film circuit, comprising: forming a second thin film circuit on a first thin film layer formed by patterning a substrate; In the method for forming a multilayer thin film circuit for forming a thin film layer, after forming a first thin film circuit material on the substrate, a resist film is formed on the first thin film circuit material,
The first thin film circuit is patterned by increasing the flow rate ratio of the etching gas for the resist film stepwise or continuously.

In the method for manufacturing a multilayer thin film circuit according to the first aspect, the flow rate ratio between the etching gas for the first thin film layer and the etching gas for the resist film is changed stepwise or continuously to form the first thin film layer. Because of the patterning,
The boundary formed by the upper surface and the upper side of the first thin film layer can be formed at gentle corners by a simple manufacturing process,
The step coverage of the second thin film layer formed on the first thin film layer is improved, and it is possible to prevent the breakdown voltage of the second thin film layer from being lowered, disconnection, and the like as much as possible.

[0010]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a diagram showing a multilayer thin film circuit formed by the method for forming a multilayer thin film circuit according to claim 1, wherein 1 is a substrate, and 2 is a first thin film layer.

The substrate 1 is formed of, for example, an insulating substrate such as glass or ceramic. On this substrate 1, for example, aluminum (Al), titanium (Ti), chromium (Cr),
A first thin film layer 2 made of a conductive film such as tantalum (Ta) or an insulating film such as silicon nitride (SiN _y ), silicon oxide (SiO ₂ ), or tantalum oxide (TaO _x ) is provided.

The first thin film layer 2 has a flat upper surface 2a.
And an upper side surface 2b formed continuously with the upper surface 2a
And a lower side surface 2 c formed continuously with the substrate 1 and a bottom surface 2 d in contact with the substrate 1. The upper side surface 2b is formed to have a gentler angle to the substrate 1 than the lower side surface 2c. That is, the angle between the extended line and the substrate 1 of the first aspect top 2b of the thin-film layer 2 and theta _1, when the angle between the lower side surface 2c and the substrate 1 of the first thin-film layer 2 and theta ₂ , Θ ₂ <θ ₁ <45 °, the upper side surface 2b and the lower side surface 2c are formed.

When formed in this manner, the first thin film layer 2 can be formed to have a small width, and the angle θ ₃ formed between the upper surface 2a and the upper side surface 2b of the first thin film layer 2 can be increased. As shown in FIG. 2, even if a second thin film layer 3 made of an insulating film or a conductive film is formed on the first thin film layer 2,
There is no dielectric breakdown or disconnection.

In such a multilayer thin film circuit, the first thin film layer 2 is formed of a conductive layer made of aluminum or the like, and the second thin film layer 3 is formed of an insulating film made of silicon nitride, silicon oxide, tantalum oxide or the like. After being formed, it can be used as, for example, a multilayer thin film circuit for forming a gate electrode and a gate insulating film of a thin film transistor or various signal lines and a protective film.

Next, a method for forming the multilayer thin film circuit will be described. First, as shown in FIG. 1, a first thin film layer 2 is formed on a substrate 1 by a vacuum evaporation method, a sputtering method, or the like. Next, a resist film 4 is applied on the first thin film layer 2 by a spin coating method or the like and patterned. Examples of such a resist film 4 include a film containing polyisoprene as a main component and a film combining quinonediazide and a novolak resin.

Next, the first thin film layer 2 is etched and patterned along the resist film 4 by a reactive ion etching method such as a resist receding method. In the reactive ion etching method, an etching gas to be used is slightly different depending on a material to be etched. Typical etching gases include CF ₄ , CCl ₄ , SF ₆ , and O _2.
and so on. CF ₄ , SF ₆ or CCl ₄ can be used simultaneously with O ₂ . The taper angle θ of the side surface of the first thin film layer 2 is determined by the ratio between the etching rate of the first thin film layer 2 and the etching rate of the resist film 4. The plane forms a predetermined angle with respect to the plane. By increasing the flow rate of the O ₂ gas and increasing the etching rate of the resist film 4 during such a reactive ion etching process, the taper angle θ ₂ above the first thin film layer ₂ is reduced. The flow rate of the O ₂ gas may be increased stepwise or may be increased continuously.

[0017]

EXAMPLE On a glass substrate 1 made of non-alkali glass, niobium nitride (NbN) having a thickness of 300.degree.
A first thin film layer 2 made of tantalum (Ta) having a thickness of 2,000 mm is formed by a sputtering method, a positive resist film 4 is applied, and the inside of the chamber is 0.2 Torr.
Under reduced pressure, the discharge density of 1.0 W / cm ^2, 27 sccm of SF ₆ gas, O ₂ where gas was first etching a thin film layer 2 for 80 seconds while flowing at a flow rate of 13 sccm, the taper angle theta ₁ is 18 °. A second thin film 3 made of a silicon nitride film having a thickness of 3000 ° is formed on the first thin film layer 2, and a polyimide film is further formed on the second thin film layer 3 to a thickness of 1000 °. When rubbing was performed under the conditions of a speed of 50 mm / sec, a rotation speed of 500 rpm, and a pressing length of 0.3 mm, peeling occurred in the polyimide film near the boundary between the upper surface 2a and the side surface 2b of the first thin film layer 2.

Next, on a glass substrate 1 made of non-alkali glass, niobium nitride (Nb) having a thickness of 300.degree.
N) and a first thin film layer 2 made of tantalum (Ta) having a thickness of 3000 ° are formed by a sputtering method, a positive resist film 4 is applied, and the inside of the chamber is 0.2 mm.
When the pressure was reduced to Torr and the discharge density was 1.0 W / cm ² ,
After etching the first thin film layer 2 for 60 seconds while flowing SF ₆ gas at a flow rate of 27 sccm and O ₂ gas at a flow rate of 13 sccm, the flow rate of the O ₂ gas was increased to 27 sccm and the etching was further performed for 20 seconds. ₁ is 13
° and the taper angle θ ₂ were 7 °. This first thin film layer 2
A second thin film 3 made of a silicon nitride film having a thickness of 3000 ° is formed thereon, and a polyimide film is further formed to a thickness of 1000 ° on the second thin film layer 3; a moving speed of 50 mm / sec; When rubbing was performed under the conditions of 500 rpm and the indentation length of 0.3 mm, no peeling or the like occurred in the polyimide film.

[0019]

As described above, in the method for forming a multilayer thin film circuit according to the first aspect, after a first thin film layer material is formed on a substrate, a resist film is formed on the first thin film layer material. Is formed, and the flow rate ratio of the etching gas of the resist film is increased stepwise or continuously to pattern the first thin film layer, so that the upper surface portion and the upper side surface of the first thin film layer can be formed in a simple process. Can be formed at gentle corners, and the step coverage of the second thin film layer formed on the first thin film layer can be improved.
Therefore, when the second thin film layer is formed of an insulating material, the breakdown voltage of the insulating film can be increased, and peeling of the upper film formed on the insulating film can be prevented. And disconnection can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a method for forming a thin film multilayer circuit according to the present invention.

FIG. 2 is a diagram showing a thin film multilayer circuit formed by a method according to the present invention.

FIG. 3 is a diagram illustrating a conventional method for forming a thin film multilayer circuit.

FIG. 4 is a diagram showing a conventional thin film multilayer circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... 1st thin film layer, 3 ... 2nd thin film layer, 4 ... Resist film

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/1368 H01L 21/88 G02F 1/1333 505

Claims (1)

(57) [Claims] In a method for forming a multilayer thin film circuit, wherein a second thin film layer is formed on a first thin film layer formed by patterning on a substrate, a first thin film circuit material is coated on the substrate. After deposition, a resist film is formed on the first thin film circuit material, and the flow rate ratio of the etching gas for the resist film is increased stepwise or continuously to pattern the first thin film circuit. A method for forming a multilayer thin film circuit, characterized by the following.