JP3048858B2 - Method of manufacturing substrate having conductive thin film - 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 of manufacturing a substrate having a conductive thin film such as a thin film electrode and a wiring, which is used for, for example, an active matrix type liquid crystal large area display device or an ultra-high integrated circuit. is there.

[0002]

2. Description of the Related Art Integrated circuits (ICs)
In an active matrix type liquid crystal display device, tantalum (Ta: resistivity: 12.5 × 10 ⁻⁶ Ω) is used as a thin film electrode material constituting a device such as a transistor or a diode, and a wiring material for supplying a voltage or a signal thereto.・ C
m), molybdenum (Mo: resistivity 5.2 × 10 ⁻⁶ Ω · c
m), tungsten (W: resistivity 5.65 × 10 ⁻⁶ Ω · c)
m), titanium (Ti: resistivity: 42.0 × 10 ⁻⁶ Ω · c)
m), chrome (Cr: resistivity 12.9 × 10 ⁻⁶ Ω · cm)
Metal such as Ta, Mo, W, Ti, Cr
Silicide, which is an alloy of silicon and a high melting point metal, is widely used.

In general, as a wiring material, a material having the lowest possible resistivity is desired from the viewpoint of signal delay and power consumption. For example, aluminum (Al) has a resistivity of 2.66 ×
It is a material having a very low resistance of 10 ⁻⁶ Ω · cm and excellent conductivity, and also has excellent corrosion resistance and is one of the desirable materials as a wiring material. However, the melting point of Al is at most 6
60 ° C., which is much lower than the process temperature of today's integrated circuits (about 1000 ° C. for large-scale integrated circuits). When considering miniaturized devices in recent years, it is indispensable to integrate a thin film electrode and a wiring and omit a contact portion. Therefore, in order to use Al as a wiring material, it is essential to lower the temperature of the process, and at present, it is very difficult to use Al for thin-film electrodes and wiring.

On the other hand, large-scale integrated circuits (LSI: Large Sc
In the field of ale integrated circuits), Ta, Mo, W, Ti,
A wiring made of a high-melting point metal such as Cr or a silicide or the like still has a large resistivity, and developing a wiring having a lower resistance has become an important development task. Also in the active matrix type liquid crystal display device, the wiring made of the above-mentioned material has a large resistivity due to an increase in the wiring distance due to the increase in the area, which is also a development problem.

To cope with these problems, an attempt has been made to use copper (Cu: resistivity = 1.67 × 10 ⁻⁶ Ω · cm), which is a material having a lower resistance and higher conductivity than Al, as a wiring material. Has been made. However, since Cu is difficult to dry-etch, it has drawbacks such as inability to accurately pattern wiring with high resolution and poor corrosion resistance. Among them, the disadvantage of poor corrosion resistance is that, for example, a thin film of a high melting point metal having excellent corrosion resistance such as a Cr thin film is provided on a Cu thin film by a thin film forming method such as a sputtering method. Can be improved.

[0006]

However, no solution has yet been proposed for the problem that dry etching is difficult and patterning cannot be performed accurately with high resolution. It is currently not used.

The method for manufacturing a substrate having a conductive thin film according to the present invention has been made in view of the above-mentioned problems, and has the following objects.
An object of the present invention is to form a conductive thin film which is applicable to a large-scale integrated circuit or a large-area active matrix type liquid crystal display device, has low resistance, is excellent in corrosion resistance, and is accurately patterned with high resolution.

[0008]

According to the present invention, there is provided a method of manufacturing a substrate having a conductive thin film, the method comprising:
A base chrome thin film is formed on a substrate , and this chrome thin film
Forming a thin film made of copper and chromium above, these chromium
After patterning the thin film and the thin film composed of copper and chromium into a predetermined shape, the thin film composed of copper and chromium is heat-treated to be separated into a layer containing a large amount of copper and a layer containing a large amount of chromium. .

[0009]

[0010]

The inventors of the present invention have proposed copper (Cu) and chromium (Cr).
(Hereinafter referred to as Cu-Cr mixture)
When the thin film is heat-treated, the distribution of Cu atoms and Cr atoms in the Cu-Cr mixture changes in the film thickness direction, and the distribution of Cr atoms increases on the surface layer side, while the distribution of Cu atoms increases on the substrate side. In view of the change in the distribution ratio due to the heat treatment of the Cu—Cr mixture, the present inventors have proposed a method for manufacturing a substrate having a conductive thin film according to the present invention.

That is, in the manufacturing method according to claim 1 of the present invention,
First, a thin film made of Cu and Cr is formed on a substrate, and the thin film is patterned into a predetermined shape. Conventionally, a thin film made of only Cu is difficult to dry-etch, and high-resolution and accurate patterning cannot be performed.
According to this, since Cu is a mixture with Cr, patterning by dry etching is possible, and high-resolution and accurate patterning is possible.

After the patterning of the Cu-Cr mixture in this manner, a heat treatment is performed to separate the thin film into a layer containing a large amount of Cu and a layer containing a large amount of Cr. The Cu-Cr mixture is subjected to heat treatment, so that the distribution ratio of Cu atoms and Cr atoms changes in the film thickness direction as described above, and the distribution ratio of Cr atoms increases on the surface layer side, while the distribution ratio of Cu atoms increases. The distribution ratio increases on the substrate side, and a Cu layer containing a large amount of Cu atoms is formed on the substrate side, and a Cr layer containing a large amount of Cr atoms is formed on the surface layer side. And by this Cu layer,
The resistivity as a whole of the Cu—Cr mixture is reduced to 650
At a relatively low heat treatment temperature of about ℃, the resistivity becomes equivalent to or lower than that of aluminum, while the Cr layer on the surface layer protects the Cu layer, which has poor corrosion resistance, and Is improved.

[0013] Cu by heat treatment of Cu-Cr mixture thin film
The degree of separation (distribution rate change) between Cr and Cr can be observed by measuring the resistivity of the Cu—Cr mixture thin film, and as shown in FIGS. The higher the heat treatment temperature or the longer the heat treatment time,
Two layers are separated.

By forming thin-film electrodes and wirings, which are conductive thin films, on a substrate by such a manufacturing method, even when Cu is used, the patterning becomes high-resolution and accurate, and corrosion is prevented. As a result, a low-resistance, high-corrosion-resistant, high-resolution, precisely-patterned conductive thin film that can be applied to large-scale integrated circuits and large-area active-matrix liquid crystal displays is improved. Can be.

[0015] Moreover, in the manufacturing method of the present invention, the Cr film for the base is formed on a substrate, on top of the Cr thin film Cu-
A thin film of a Cr mixture is formed. Therefore, Cu obtained by heat-treating a Cu—Cr mixture thin film
When the substrate is an oxide such as a glass substrate, the Cu layer containing a large number of atoms may be easily peeled off. And a conductive thin film that is more difficult to peel off can be formed.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. However, the present embodiment illustrates a process of forming a thin film electrode and a wiring, which are conductive thin films, on a glass substrate in a process of manufacturing a large-area active matrix type liquid crystal display device. The present invention is not limited to the example, but may be a large-scale integrated circuit (LSI).
Needless to say, the method can be applied to the process of manufacturing t).

FIG. 2 shows the wiring of the wiring portion of the substrate with thin film electrodes and wirings manufactured in the step of forming thin film electrodes and wirings using the method for manufacturing a substrate having a conductive thin film according to the present embodiment. A cross section along the longitudinal direction is schematically shown. On the glass substrate 1, a base Cr made of chromium (Cr)
A layer (thin film) 2 is formed as a thin film, and a mixture of copper (Cu) and chromium (hereinafter referred to as Cu-Cr) is further formed thereon.
A mixture of the underlayer Cr layer 2 and the Cu-Cr mixed layer 3 is called a mixture.
The wiring layer 4 is formed with the mixed layer 3.

In the Cu—Cr mixed layer 3 in the wiring portion 4, the distribution ratio of Cu atoms and Cr atoms changes in the film thickness direction, and the distribution ratio of Cr atoms increases on the surface side, while The distribution rate of Cu atoms is determined on the glass substrate 1 side (Cr for base).
Layer 2a), the Cu layer 3a containing many Cu atoms on the glass substrate 1 side, and the Cr layer 3 containing many Cr atoms on the surface layer side.
b is formed. That is, the wiring section 4 is a three-layered Cr / Cu / Cr thin film on the glass substrate 1.

By forming such a three-layered Cr / Cu / Cr laminated thin film, the wiring part 4 has excellent conductivity, excellent corrosion resistance, and excellent adhesion to the glass substrate 1. It is equipped. More specifically, the Cu layer 3a shows excellent conductivity, and the Cr layer 3b on the surface layer protects the copper layer 3a, which has poor corrosion resistance, to show excellent corrosion resistance. The layer 2 improves the adhesion to the glass substrate 1 which is an oxide. Moreover, since the wiring portion 4 is patterned by dry etching as described later, the wiring portion 4 is accurately patterned with high resolution.

A substrate with thin film electrodes and wiring provided with such a wiring portion 4 of a Cr / Cu / Cr three-layer laminated thin film is manufactured through the processes 1 to 4 shown in the process diagram of FIG.

First, in process 1 (P1), FIG.
As shown in (a), a Cr layer 2 for a base is formed on a glass substrate 1.
Is formed with a thickness of 100 nm by a sputtering method.

Next, in process 2 (P2), FIG.
As shown in (b), the underlayer Cr layer 2 on the glass substrate 1
On top of this, a Cr—Cu mixed layer 3 having a mixing ratio of Cr: Cu of 2: 3 is formed as a thin film with a thickness of 240 nm by a sputtering method. For sputtering, for example, Ar ⁺ ion gas is used, and the argon pressure is set to 0.3 torr.

On a glass substrate 1, an underlayer Cr layer 2 and a Cr layer
-Cu mixed layer 3 is formed, then process 3
At (P3), as shown in FIG.
The r-Cu mixed layer 3 is patterned into a predetermined thin film electrode and wiring shape by a photolithography technique.
In this case, for example, CCl ₄ plasma etching at a substrate temperature of 350 ° C. is used. still,
Since patterning using photolithography is a well-known technique, its description is omitted here.

Subsequently, in a process 4 (P4), this is heat-treated. The heat treatment is performed, for example, in an N ₂ atmosphere at 650 ° C. for 1 hour. By performing the heat treatment under such conditions, the Cr—Cu mixed layer 3 formed on the underlayer Cr layer 2 on the glass substrate 1 becomes, as shown in FIG. The distribution ratio of atoms changes in the film thickness direction, and the Cr / Cu2 layer is separated into a Cr layer 3b containing a large amount of Cr atoms on the surface layer side and a Cu layer 3a containing a large amount of Cu atoms on the glass substrate 1 side. Thus, the substrate with thin-film electrodes and wirings shown in FIG. 2 is formed. At this time, the distribution ratio of Cr atoms always increases on the surface side, and the Cr layer 3b is formed.

Here, the mechanism of the separation of the Cr—Cu mixed layer 3 into two layers will be described. It is known from experience that Cu and Cr do not alloy with each other. At 800 ° C., Cu has the property that softening proceeds at a temperature much lower than the melting point. For this reason, Cr-
When the Cu mixed layer 3 is heat-treated, the Cu molecules become 650 ° C.
Even in the following, the particles move actively in the solid phase and undergo molecular bonding, and as a result, layer separation occurs such as the Cr layer 3b and the Cu layer 3a. At this time, since the Cu molecules on the surface side are sucked from only one side, they are only sucked into the inside as the moving direction, and therefore, Cu is
A difference in atomic concentration occurs. When this progresses macroscopically, the Cu atoms aggregate at the center and push up the Cr atoms in the center. As a result, the distribution rate of Cr atoms always increases on the surface side, and the Cr layer 3b is formed. It will be.

Cr-Cu by heat treatment in the above P4
The degree of the Cr / Cu bilayer separation of the mixed layer 3 can be observed from the change in the resistivity of the Cr—Cu mixed layer 3, and the degree is determined by the heat treatment temperature and the heat treatment time.

That is, as shown in a graph a of FIG. 4 showing the dependence of the resistivity of the Cr—Cu mixed layer 3 on the heat treatment temperature, the higher the heat treatment temperature, the lower the resistivity of the Cu—Cr mixed layer 3; Separation of the Cu—Cr mixed layer 3 proceeds. This graph a
Is the same Cu-Cr mixture as in the case of the present example 240n
The graph shows heat treatment temperature dependency when a Cu—Cr mixed thin film formed with a thickness of m is heat-treated for one hour.

As shown in a graph b of FIG. 5 showing the dependence of the resistivity of the Cr—Cu mixed layer 3 on the heat treatment time, the longer the heat treatment time, the lower the resistivity of the Cu—Cr mixed layer 3. ,
Separation of the Cu—Cr mixed layer 3 proceeds. This graph b shows that a Cu—Cr mixed thin film in which the same Cu—Cr mixture as in the present embodiment was formed with a thickness of 240 nm was subjected to a heat treatment at 400 ° C.
It shows the heat treatment time dependency when heat treatment is performed at ℃.

As apparent from the graph a in FIG. 4, when the heat treatment is performed at 650 ° C. for 1 hour as in the present embodiment, the resistivity is about 5.8 × 10 ⁻⁶ Ω · cm, It has a resistivity equivalent to that of (Al).

As described above, in this embodiment, the Cu—Cr mixed layer 3 is formed on the glass substrate 1 (P2),
-Cr mixed layer 3 is patterned into a predetermined shape (P
3) Heat treatment is performed to change the distribution ratio of Cu atoms and Cr atoms (P4), so that the surface layer is separated into a Cr layer 3b, and the glass substrate 1 is separated into a Cu layer 3a and a Cu / Cr2 layer. .

By adopting such a manufacturing method, even when Cu is used, the patterning becomes high-resolution and accurate, and the corrosion resistance of the Cu layer 3a is improved by the Cr layer 3b formed on the surface side. As a result, low-resistance, high-corrosion-resistant, high-resolution, accurately-patterned thin-film electrodes and wirings applicable to large-scale integrated circuits and large-area active-matrix liquid crystal displays are formed. be able to. Moreover, the temperature required for the heat treatment is 650
It is possible at a low temperature of about ° C.

Further, in this embodiment, in process 1,
An underlayer Cr layer 2 is formed on a glass substrate 1, and a Cu—Cr mixed layer 3 is formed on the Cr layer 2.
The Cu layer 3a formed on the side has a possibility of being easily peeled off when the base is an oxide like the glass substrate 1, but by being formed on the Cr layer 2 for the base, Also, a good adhesion can be obtained between the glass substrate 1 and the glass substrate 1, and a structure that is difficult to peel off can be obtained.

The mixing ratio between Cu and Cr in the above-mentioned Cu-Cr mixed layer 3, the thickness of the Cu-Cr mixed layer 3, the method of forming the thin film, and various conditions at that time are not limited thereto. Absent. Further, in the present embodiment, in the N ₂ atmosphere, 65
Although heat treatment was performed at 0 ° C. for 1 hour, as shown in FIGS. 4 and 5, as the heat treatment temperature is increased and the heat treatment time is increased, low-resistance wiring and thin-film electrodes can be formed. The processing conditions may be adjusted and set in accordance with the desired resistivity.

[0034]

As described above, the method for manufacturing a substrate having a conductive thin film according to the present invention comprises the steps of:
Formed, to form a thin film made of copper and chromium in this chromium on the thin film composed of these chromium thin film and a copper and chromium
After patterning the thin film into a predetermined shape, the above copper and chromium are separated to separate the layer containing a large amount of copper and the layer containing a large amount of chromium.
And heat treating the thin film comprising

As a result, even when copper is used, the patterning is performed with high resolution and accuracy, and the corrosion resistance is improved. As a result, a large scale integrated circuit or a large area active matrix type liquid crystal display device is obtained. This has the effect of being able to form thin-film electrodes, wirings, and the like, which can be applied with low resistance, have excellent corrosion resistance, and are accurately patterned with high resolution.

[0036]

Further, the copper layer having a lot of copper atoms obtained by heat-treating a thin film made of copper and chromium, if the substrate is an oxide such as a glass substrate, has the possibility of easily peeling By being formed on the chromium thin film for the base, good adhesion can be obtained even with the oxide substrate, and an effect that a structure that is difficult to peel off can be obtained is exerted.

[Brief description of the drawings]

FIG. 1 is a process diagram showing a manufacturing process of a substrate with thin-film electrodes and wiring, employing a manufacturing method according to an embodiment of the present invention.

FIG. 2 is a sectional view of a principal part schematically showing a wiring portion of the substrate with thin film electrodes and wiring.

3 (a) to 3 (d) are explanatory views for explaining each process of the manufacturing process shown in FIG. 1, and FIG. 3 (a) shows a process 1 in which a base Cr layer is formed on a glass substrate. (B) shows a state in which Cu-
3C shows a state in which a Cr mixed layer is formed, FIG. 3C shows a state in which an underlayer Cr layer and a Cu—Cr mixed layer are patterned in process 3, and FIG. This shows a state in which the Cr layer for use and the Cu-Cr mixed layer are heat-treated and separated into two layers.

FIG. 4 is a graph showing the heat treatment temperature dependence of the resistivity of a Cu—Cr mixed layer.

FIG. 5 is a graph showing the heat treatment time dependency of the resistivity of a Cu—Cr mixed layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass substrate (substrate) 2 Cr layer for base (chrome thin film for base) 3 Cu-Cr mixed layer (thin film composed of copper and chromium) 3a Cu layer 3b Cr layer

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-170043 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01B 13/00 503 H05K 1/09 H05K 3 / 22 C23C 14/00-14/58

Claims (1)

(57) [Claims] A chromium thin film for a base is formed on a substrate.
Forming a thin film composed of copper and chromium on the chromium thin film of
After patterning the chromium thin film and the thin film composed of copper and chromium into a predetermined shape, the thin film composed of copper and chromium is subjected to heat treatment so as to be separated into a layer containing a large amount of copper and a layer containing a large amount of chromium. A method for manufacturing a substrate having a conductive thin film.