JPH0629238A - Formation method of electrode interconnection - Google Patents

Abstract

PURPOSE:To obtain the formation method, of an electrode wiring, wherein a special process is not required to be added, generation of whiskers are restrained and the covering property of a protective film is improved. CONSTITUTION:A semiconductor layer such as a phosphorus-doped amorphous silicon film layer 7 or the like is formed on an insulating substrate 1; a high- melting-point metal film layer 8 and an aluminum film layer 9 are laminated and formed as an electrode wiring which comes into contact with the semiconductor layer; the weight density of the high-melting-point metal layer 8 is set at 70 to 85% of the true density of its metal. Generation of whiskers from the aluminum film layer 9 is thereby restrained even at a high temperature when a protective film 10 is formed.

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 semiconductor element such as an electrode wiring of a thin film transistor for a matrix type display device.

[0002]

2. Description of the Related Art FIG. 3 is a cross section of an electrode wiring formed by a conventional method for forming an electrode wiring disclosed in, for example, Japanese Patent Application Laid-Open No. 2-188922. In FIG. 3, 1 is an insulating substrate and 6 is an insulating substrate. Silicon nitride film layer, 8 is a refractory metal (Ti
W) film layer, 11 is an aluminum alloy film layer.

In FIG. 3, silicon (Si) and copper (C) are contained in the aluminum alloy film layer 11 which constitutes the electrode wiring.
An impurity such as u) is added. When this electrode wiring is formed of only an aluminum film, when heat treatment is applied after the formation of the electrode wiring, aluminum atoms in the electrode wiring cause migration and grain growth such as whiskers (needle-shaped crystals) occurs. The grain growth breaks through the protective film on the electrode wiring and causes problems such as insulation failure and signal leakage.

As shown in FIG. 3, silicon (Si), copper (C
When u) is added to the aluminum alloy film layer 11, silicon and copper are precipitated at grain boundaries of aluminum and the like, and thus have a function of suppressing the migration of aluminum as described above. Therefore, grain growth such as whiskers is also suppressed, and the above obstacles are alleviated.

FIG. 4 is a cross section of an electrode wiring formed by the conventional method of forming an electrode wiring disclosed in, for example, Japanese Patent Laid-Open No. 2-85826. In FIG. 4, 1 is an insulating substrate and 3 is a transparent electrode. A layer, 6 is a silicon nitride film layer, 9 is an aluminum film layer, and 12 is an aluminum oxide film layer.

In FIG. 4, an aluminum oxide film layer 12 obtained by anodizing the aluminum film layer 9 is formed on the electrode wiring. The aluminum oxide film layer 12 suppresses grain growth from the aluminum film layer 9 caused by the heat treatment after the electrode wiring is formed, and thus has an effect of reducing insulation failure due to whiskers and the like.

As described above, in order to suppress abnormal protrusions such as whiskers caused by heat treatment of the aluminum electrode wiring and to reduce obstacles such as defective insulation of the protective film on the electrode wiring, There are conventional examples such as a method of adding impurities such as silicon and copper, and a method of forming aluminum oxide on aluminum electrode wiring.

[0008]

Since the conventional method for forming the electrode wiring is as described above, when added impurities such as silicon and copper are added to aluminum, these added impurities cause etching residue when patterning the aluminum alloy electrode wiring. Therefore, there is a problem that the number of removing steps must be increased.

Further, the method of forming an aluminum oxide film on the electrode wiring has a problem that the number of steps of anodic oxidation is increased or the control of anodic oxidation is relatively difficult. Furthermore, when anodization is performed after patterning the electrode wiring, isolated pattern portions such as the electrode portions cannot be anodized. Further, when anodization is performed only on the entire electrode wiring portion before patterning the electrode wiring, a selective etching technique of aluminum and aluminum oxide is required at the time of patterning, which causes a problem that wiring resistance increases. .

The present invention has been made in order to solve the above problems, and it is possible to remove aluminum from aluminum without adding an additive impurity such as silicon or copper or forming an aluminum oxide film on an aluminum electrode wiring. It is an object of the present invention to provide an electrode wiring forming method capable of significantly suppressing abnormal protrusions such as whiskers and improving the coverage of the protective film on the electrode wiring.

[0011]

A method of forming an electrode wiring according to the present invention comprises two layers of an aluminum film layer or an aluminum alloy film layer and a refractory metal film layer thereunder, and the weight of the refractory metal film layer. Density 70 to 85% of true density of high melting point metal
It is the one.

[0012]

The electrode wiring forming method according to the present invention includes the steps of forming a refractory metal film layer and an aluminum film layer or an aluminum alloy film layer, and then performing heat treatment such as film formation.
The weight density of the refractory metal film layer is 70 to 85 of its true density.
%, The lattice constant and the coefficient of thermal expansion are large. Therefore, the function of the refractory metal film layer to reduce the difference in the coefficient of thermal expansion between the aluminum film layer or the aluminum alloy film layer and the insulating substrate. By suppressing the film stress on the aluminum film layer or the aluminum alloy film layer at high temperature, occurrence of abnormal protrusions such as whiskers is suppressed.

[0013]

EXAMPLES Example 1. FIG. 1 shows a cross section of a thin film transistor manufactured by using a method for forming an electrode wiring according to an embodiment of the present invention. Hereinafter, a method of manufacturing this thin film transistor will be described.

First, chromium is deposited on the insulating substrate 1 as the gate electrode wiring layer 2 to a film thickness of 2000 to 3000 Å by an electron beam heating vapor deposition method or a sputtering method and patterned. Next, a transparent electrode layer 3 made of indium oxide is deposited on the insulating substrate 1 to a film thickness of 500 to 1500Å and patterned to form a pixel electrode. As the gate insulating film layer 4, a silicon nitride film having a film thickness of 1000 to 4000 Å is deposited on the entire surface by, for example, a plasma CVD method.

Further, the amorphous silicon film layer 5 has a film thickness of 50.
The thickness of the silicon nitride film layer 6 is 1000 to 0 to 1000Å
It deposits up to 3,000Å. After that, the silicon nitride film layer 6 is patterned to locally remove a portion which becomes a channel of the thin film transistor and a portion on the transparent electrode layer 3. Next, after depositing an amorphous silicon film layer 7 doped with phosphorus of 0.5 to 3% to a film thickness of 500 to 1000Å, the gate insulating film layer 4 and the amorphous silicon film 4 are formed on the contact portion of the transparent electrode layer 3. The film layer 5 and the phosphorus-doped amorphous silicon film layer 7 are locally removed to form contact holes.

Next, as the refractory metal film layer 8 for preventing the reaction between aluminum and silicon, for example, a chromium film having a film thickness of 500 to 1000Å and an aluminum film layer 9 having a film thickness of 20 are formed.
After being sequentially deposited by an electron beam heating vapor deposition method or a sputtering method in the range of 00 to 6000 Å, patterning is performed in the shape of the electrode wiring. At this time, the refractory metal film layer 8 electrically contacts the transparent electrode layer 3. The weight density of the chromium film at this time is 70 to 85% of its true density. After that, the portion of the phosphorus-doped amorphous silicon film layer 7 whose surface is exposed and the portion of the amorphous silicon film layer 5 below it are removed. At this time, the surface of the silicon nitride film layer 6 on the gate electrode wiring layer 2 is exposed.

Finally, as the protective film 10, for example, a silicon nitride film is formed from 6000 to 10000 by a plasma CVD method.
After depositing to a film thickness of Å, the protective film 10 portion on the terminal portion is removed to complete the thin film transistor array substrate.

The operation of this embodiment will be described below. When the protective film layer 10 is deposited, heating is usually performed at about 300 ° C. At this time, grain growth from the aluminum film layer 9 occurs, and it is assumed that a defect such as a defective coating of the protective film layer 10 occurs. . Among the grain growth, abnormal projections such as whiskers are difficult to cover even with the protective film layer 10, and have a serious influence.

FIG. 2 shows the relationship between the density of whiskers generated from the aluminum film layer at this time and the ratio of the weight density to the chromium density of the chromium film layer which is the refractory metal film layer. Also,
The density of whiskers when there is no chromium film layer under the aluminum wiring film layer is also shown by the broken line. As shown by the solid line in the figure, when the ratio of the weight density of the chromium film layer is 90% or more, the whisker generation density also increases with the increase of the weight density, reaching a maximum of 1000 wires / cm ² .

On the other hand, when the weight density ratio of the chromium film layer is 70 to 85% as in this embodiment, whiskers are hardly generated. In this case, the protective film 10 on the electrode wiring of the thin film transistor is not generated. It is possible to significantly reduce the defective coating.

As described above, when the electrode wiring on the silicon-based semiconductor layer is formed of two layers of the aluminum film layer and the refractory metal film layer, and then heat treatment such as film formation is performed, the aluminum film layer and the high-melting-point metal film layer are formed. A compressive stress is generated in the aluminum film layer due to the difference in coefficient of thermal expansion between the melting point metal film layer and the insulating substrate (for example, glass). It is known that such film stress at a high temperature causes aluminum atoms to move in the aluminum film layer to cause abnormal protrusions such as whiskers.

At this time, when the refractory metal film layer under the aluminum film layer is close to the true density, the coefficient of thermal expansion is smaller than the coefficient of thermal expansion of the aluminum film layer and is almost the same as that of an insulating substrate such as glass. Become.

However, as in the above embodiment, the weight density of the refractory metal film layer 8 is 70 to 85% of the true density of the metal.
In the refractory metal film layer 8 characterized by
Both the lattice constant and the coefficient of thermal expansion are large, so in this case,
The refractory metal film layer 8 is formed of the aluminum film layer 9 and the insulating substrate 1.
And has a function of alleviating the difference in the coefficient of thermal expansion from the above, and suppresses the generation of whiskers and the like in the aluminum film layer 9 when the protective film 10 is formed. In the above weight density range, the refractory metal film layer 8 can effectively prevent the eutectic reaction between aluminum and silicon in the semiconductor layer.

[0024]

As described above, according to the present invention, in a semiconductor element on an insulating substrate, a refractory metal such as a chromium film which is in contact with the semiconductor layer and has a weight density of 70 to 85% of the true density. Since the electrode wiring is formed by two layers of the film layer and the aluminum film layer or the aluminum alloy film layer, it is possible to remove the electrode wiring from the aluminum film layer at the time of heat treatment after forming the electrode wiring without adding steps or adding impurities. Whisker density can be reduced. In addition, faults such as insulation failure and signal leakage due to poor coverage of the protective film on the electrode wiring are significantly reduced, which has the effect of improving the reliability of the device.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a thin film transistor to which an electrode wiring forming method according to an embodiment of the present invention is applied.

FIG. 2 is a diagram showing a relationship between a whisker generation density from an aluminum film layer and a ratio of a weight density and a chromium density of a chromium film layer which is a refractory metal.

FIG. 3 is a cross-sectional view showing an electrode wiring formed by an example of a conventional electrode wiring forming method.

FIG. 4 is a cross-sectional view showing an electrode wiring formed by another example of a conventional electrode wiring forming method.

[Explanation of symbols]

 1 Insulating Substrate 2 Gate Electrode Wiring Layer 3 Transparent Electrode Layer 4 Gate Insulating Film Layer 5 Amorphous Silicon Film Layer 6 Silicon Nitride Film Layer 7 Phosphorus Doped Amorphous Silicon Film Layer 8 Refractory Metal Film Layer 9 Aluminum Film Layer 10 Protection Membrane layer

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[Procedure amendment]

[Submission date] December 4, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

Further, the method of forming an aluminum oxide film on the electrode wiring has a problem that the number of steps of anodic oxidation is increased or the control of anodic oxidation is relatively difficult. Furthermore, when anodization is performed after patterning the electrode wiring, isolated pattern portions such as the electrode portions cannot be anodized. Further, when anodization is performed only on the entire surface of the electrode wiring before patterning the electrode wiring, a selective etching technique of aluminum and aluminum oxide is required at the time of patterning, and in addition , there is a problem that wiring resistance increases. was there.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

[0011]

A method of forming an electrode wiring according to the present invention comprises two layers of an aluminum film layer or an aluminum alloy film layer and a refractory metal film layer thereunder, and the weight of the refractory metal film layer. The density is 70 to 8 of the weight density of the high melting point metal.
5%.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

[0012]

The electrode wiring forming method according to the present invention includes the steps of forming a refractory metal film layer and an aluminum film layer or an aluminum alloy film layer, and then performing heat treatment such as film formation.
The weight density of the refractory metal film layer is the same as that of the refractory metal.
In the refractory metal film layer having 70 to 85% of the degree , both the lattice constant and the coefficient of thermal expansion are large. Therefore, the refractory metal film layer has a coefficient of thermal expansion between the aluminum film layer or the aluminum alloy film layer and the insulating substrate. It acts to reduce the difference, reduces film stress on the aluminum film layer or aluminum alloy film layer at high temperature, and suppresses abnormal protrusions such as whiskers.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

Next, as the refractory metal film layer 8 for preventing the reaction between aluminum and silicon, for example, a chromium film having a film thickness of 500 to 1000Å and an aluminum film layer 9 having a film thickness of 20 are formed.
After being sequentially deposited by an electron beam heating vapor deposition method or a sputtering method in the range of 00 to 6000 Å, patterning is performed in the shape of the electrode wiring. At this time, the refractory metal film layer 8 electrically contacts the transparent electrode layer 3. The weight density of the chromium film at this time is 70 to 85% of the weight density of the refractory metal.
So that After that, the portion of the phosphorus-doped amorphous silicon film layer 7 whose surface is exposed and the portion of the amorphous silicon film layer 5 below it are removed. At this time, the surface of the silicon nitride film layer 6 on the gate electrode wiring layer 2 is exposed.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

FIG. 2 shows the relationship between the density of whiskers generated from the aluminum film layer at this time and the ratio of the weight density to the chromium density of the chromium film layer which is the refractory metal film layer. Also,
The density of whiskers when there is no chromium film layer under the aluminum wiring film layer is also shown by the broken line. As shown by the solid line in the figure , when the ratio of the weight density of the chromium film layer to the weight density of chromium is 90% or more, the whisker generation density increases with the increase of the weight density, and the maximum whisker density is 1000 (au). Reach

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

On the other hand, when the ratio of the weight density of the chromium film layer to the weight density of chromium is 70 to 85% as in the present embodiment, whiskers are hardly generated. In this case, the electrode wiring of the thin film transistor is formed. Poor coating of the upper protective film 10 can be greatly reduced.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

At this time, when the weight density of the refractory metal film layer below the aluminum film layer is close to the weight density of the refractory metal , the coefficient of thermal expansion is small as compared with the coefficient of thermal expansion of the aluminum film layer. It is almost equivalent to such an insulating substrate.

[Procedure Amendment 9]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

However, as in the above embodiment, the weight density of the refractory metal film layer 8 is 70 to 85 that of the weight density of the metal.
%, The lattice constant and the coefficient of thermal expansion are large. Therefore, in this case, the refractory metal film layer 8 has a high thermal melting point between the aluminum film layer 9 and the insulating substrate 1. The protective film 10 has a function of relaxing the difference in expansion coefficient.
Generation of whiskers and the like of the aluminum film layer 9 during formation is suppressed. In the above weight density range, the refractory metal film layer 8 can effectively prevent the eutectic reaction between aluminum and silicon in the semiconductor layer.

[Procedure Amendment 10]

[Document name to be amended] Statement

[Name of item to be corrected] 0024

[Correction method] Change

[Correction content]

[0024]

As described above, according to the present invention, in the semiconductor element on the insulating substrate, the semiconductor element is in contact with the semiconductor layer and
Since the electrode wiring is formed by two layers of a high melting point metal film layer such as a chromium film having a weight density of 70 to 85% of the weight density of a high melting point metal such as chromium and an aluminum film layer or an aluminum alloy film layer, It is possible to reduce the density of whiskers generated from the aluminum film layer during the heat treatment after the formation of the electrode wiring, without adding a metal oxide or adding impurities. In addition, faults such as insulation failure and signal leakage due to poor coverage of the protective film on the electrode wiring are significantly reduced, which has the effect of improving the reliability of the device.

[Procedure Amendment 11]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Figure 2] and generation density of whiskers from aluminum film layer is a diagram showing the relationship between the ratio of the weight density and chromium weight density of the chromium film layer is a refractory metal film layer.

[Procedure Amendment 12]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

Claims (1)

[Claims] 1. A method of manufacturing a semiconductor element, comprising forming a semiconductor layer on an insulating substrate and forming electrode wiring in contact with the semiconductor layer, wherein a refractory metal film layer and an upper portion of the refractory metal film layer are used as the electrode wiring. A method for forming electrode wiring, wherein an aluminum film layer or an aluminum alloy film layer is laminated on and the weight density of the refractory metal film layer is set to 70 to 85% of the true density of the refractory metal. .