JP3282204B2 - Method of forming aluminum-based alloy 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 for forming an aluminum alloy film by a sputtering apparatus.

[0002]

2. Description of the Related Art In general, the electrodes and wirings of a thin film element such as a thin film transistor or a multilayer wiring board in which wiring is formed in a plurality of layers with an insulating film interposed therebetween are generally made of Cr (chromium), Ta (tantalum), and Mo (molybdenum). Etc., but these high melting metals have high resistance,
There is a problem that the voltage drop at the electrode and the wiring is large.

Therefore, the use of inexpensive Al (aluminum) having a low resistance value for the electrodes and wirings of the thin film element and the multilayer wiring board has been studied. But,
Since this Al film has a problem that hillocks are generated on the surface when it is heated to several hundred degrees Celsius, if the lower electrode and the lower wiring of the thin film element or the multilayer wiring board are formed of Al, the thin film element or the multilayer wiring In the manufacturing process of the board, a defect occurs in the insulating film formed on the lower electrode and the lower wiring, and an interlayer short circuit occurs between the lower electrode and the lower wiring and the upper electrode and the lower wiring.

That is, for example, an inverted stagger type thin film transistor has a gate electrode and a gate wiring formed on an insulating substrate made of glass or the like, and a gate insulating film made of SiN (silicon nitride) is formed thereon. An i-type semiconductor layer made of -Si (amorphous silicon), an n-type semiconductor layer made of a-Si doped with an n-type impurity, and a metal film for source and drain are sequentially formed. A drain metal film and an n-type semiconductor layer thereunder;
The gate insulating film and the i-type and n-type semiconductor layers are formed at a substrate temperature of several hundred degrees centigrade by a plasma CVD apparatus. Therefore, hillocks are generated on the surfaces of the gate electrode and the gate wiring during the film formation. This hillock is considered to be due to a phenomenon of relaxation of stress generated in the Al film by heating.

When hillocks are generated on the surfaces of the gate electrode and the gate wiring, the hillocks penetrate the gate insulating film and generate defects such as cracks in the gate insulating film. The gate wiring is short-circuited with the upper source and drain electrodes and the data wiring.

On the other hand, it has been clarified that if Al contains a high melting point metal such as Ti (titanium) or Ta, the generation of hillocks during heating is suppressed. By forming the lower electrode and the lower wiring of the thin film element and the multilayer wiring board with the Al-based alloy,
The hillock can be prevented from being generated on the surface of the lower electrode and the lower wiring during the formation of an insulating film or the like in a later step.

By the way, the lower electrode and the lower wiring of the thin film element and the multilayer wiring board are formed by forming a metal film on a substrate by a sputtering apparatus and patterning the metal film by a photolithography method.

[0008] The formation of a metal film by the above sputtering apparatus is as follows.
Conventionally, after a substrate is placed in a sputtering chamber, air in the sputtering chamber is evacuated until the pressure in the sputtering chamber becomes 5 × 10 ⁻⁶ Torr or less, and the sputtering chamber is almost evacuated. ) A sputtering gas such as a gas is introduced, and a predetermined gas pressure (3 × 10 ⁻³ to 8 × 10 ⁻³
The method is performed by starting sputtering in r).

[0009]

However, in a thin film element or a multilayer wiring board in which a lower electrode and a lower wiring are formed by a metal film formed by the above-mentioned conventional film forming method, the metal film contains a high melting point metal. Even with the Al-based alloy film formed, an interlayer short circuit may occur between the lower electrode and the lower wiring and the upper electrode and the upper wiring.

Therefore, in order to know the cause of the occurrence of the interlayer short-circuit, as shown in FIGS. 2 and 3, an electrode 2 made of an Al-based alloy containing Ti as a refractory metal is formed on a glass substrate 1. When the substrate 1 was heated to about 250 ° C. and the change in the state of the surface of the electrode 2 was examined,
Although the hillocks described above do not occur, it has been found that the projections 3 as shown in the figure are locally generated on the side surfaces and edge portions of the electrode 2. Although the cause of the formation of the projections 3 is unknown, the stress relaxation phenomenon in a form different from the above-mentioned generation of hillocks, that is, the stress generated in the Al-based alloy film by heating is concentrated on the weak portions of the side surfaces and edges of the coating. However, it is presumed that local crystal growth occurs in this portion.

Since the thin film element and the multilayer wiring board are manufactured by the above-described manufacturing method, the lower electrode and the lower wiring are heated when an insulating film or the like is formed on the lower electrode and the lower wiring, so that the protrusions 3 are formed. And defects such as cracks occur in the insulating film due to the influence of the projections 3, causing an interlayer short circuit.

It is an object of the present invention to provide a highly reliable Al-based alloy film which does not generate hillocks or local protrusions on the side and edge portions of the coating film even when heated to several hundred degrees centigrade. An object of the present invention is to provide a method of forming an Al-based alloy film that can be formed.

[0013]

According to the present invention, after a substrate is inserted into a sputtering chamber, air in the sputtering chamber is evacuated until the pressure in the sputtering chamber becomes 5 × 10 ^{-5 to} 5 × 10 ^-4 Torr.
After that, a sputtering gas is introduced into the sputtering chamber and 3 × 10
^-3 to 8 × 10 ^-3 Torr gas pressure.
To a target made of an aluminum alloy
By supplying electric current and performing sputtering, nitrogen
Containing metals, oxygen, hydrogen, etc. and containing high melting point metals.
It is characterized by forming a film of a luminium-based alloy .

[0014]

That is, according to the present invention, the exhaust gas in the sputter chamber after the substrate is charged into the sputter chamber is discharged at a pressure of 5 sputter chamber.
Only until it reaches x10 ^{-5 to} 5x10 ^-4 Torr,
A small amount of air is left in the sputtering chamber.If a small amount of air is left in the sputtering chamber, the remaining air is mixed into the sputtering gas introduced into the sputtering chamber thereafter. Since the nitrogen, oxygen, hydrogen and the like in the remaining air are deposited on the substrate together with the sputtered particles, the formed Al-based alloy film becomes a film containing a trace amount of nitrogen, oxygen, hydrogen and the like. The Al-based alloy film containing nitrogen, oxygen, hydrogen and the like does not generate hillocks or local projections on the side and edge portions even when heated to several hundred degrees Celsius.

[0015]

An embodiment of the present invention will be described below.

FIG. 1 shows a sputtering apparatus. This sputtering apparatus is used for forming various metal films, and is provided with openable and closable doors 11 a and 11 b at a substrate loading / unloading entrance and an exit of the sputtering chamber 10. An exhaust pipe 12 connected to an exhaust pump (not shown) and a sputter gas introduction pipe 13 for introducing a sputter gas such as Ar gas are connected to the sputter chamber 10. Reference numerals 14 and 15 are a flow rate controller and an on-off valve provided in the gas introduction pipe 13. At the bottom of the sputtering chamber 10, there is provided a substrate transfer device mechanism 16 for transferring the substrate 20 loaded from the substrate loading / unloading port toward the exit. Further, a heater 17 for heating the substrate 20 and a target 18 are arranged side by side in the substrate transfer direction in an upper part in the sputtering chamber 10, and a sputtering power supply 19 is connected to the target 18.

[0017] A
The l-based alloy film is deposited on the target 18 by Ti or T
The procedure is as follows using an Al-based alloy plate containing a high melting point metal such as a.

First, a substrate 20 for forming an Al-based alloy film is loaded into the sputtering chamber 10 from the substrate loading / unloading port.
The substrate 20 is supported by the substrate transfer device mechanism 16 with its film formation surface facing upward.

Next, the sealing door 11a is closed and the sputtering chamber 1 is closed.
After sealing 0, the air in the sputtering chamber 10 is exhausted until the pressure in the sputtering chamber becomes 5 × 10 ^{−5 to} 5 × 10 ⁻⁴ Torr. This sputter chamber pressure is one or two or more digits higher than the pressure (5 × 10 ⁻⁶ Torr or less) in the conventional film forming method. Therefore, the air in the sputter chamber 10 is not completely exhausted. A small amount of air remains in the sputtering chamber 10.

Next, the heating of the substrate 20 by the heater 17 is started, a sputtering gas is introduced into the sputtering chamber 10, the temperature of the substrate 20 is set to a predetermined film forming temperature, and the sputtering gas in the sputtering chamber 10 is heated. After the pressure is stabilized at a predetermined gas pressure (3 × 10 ⁻³ to 8 × 10 ⁻³ Torr), the transfer of the substrate 20 by the substrate transfer device mechanism 15 is started, and at the same time, the discharge current from the sputtering power source 19 to the target 18 is discharged. To start sputtering.

The principle of this sputtering is well known. When a discharge current is supplied from a sputtering power supply 19 to a target 18 to generate plasma, sputter particles are sputtered from the target (Al-based alloy plate) 18 by the plasma. The sputtered particles are deposited on the surface of the substrate 20.

In this film forming method, the sputtering chamber 1
After the substrate 21 is charged into the chamber 0, the inside of the sputtering chamber 10 is evacuated only slightly until the pressure in the sputtering chamber becomes 5 × 10 ^{−5 to} 5 × 10 ⁻⁴ Torr. Since the air is left, the air remaining in the sputtering chamber 10 is mixed with the sputtering gas introduced into the sputtering chamber 10 thereafter, and nitrogen, oxygen, hydrogen, etc. in the remaining air are sputtered together with sputter particles. Deposit on the substrate. Therefore, the Al-based alloy film 21 formed by the above-described film forming method becomes a film containing trace amounts of nitrogen, oxygen, hydrogen and the like.

Even when this Al-based alloy film containing nitrogen, oxygen, hydrogen, etc. is heated to several hundreds of degrees Celsius, not only hillocks but also the side and edge portions of the film as shown in FIGS. No local protrusion occurs.

In this method, an Al-based alloy film is formed on a glass substrate by the above-described film forming method, and after patterning the Al-based alloy film into an electrode shape as shown in FIGS. 2 and 3,
This was also confirmed by heating the substrate to 250 to 300 ° C. and examining the change in the state of the surface of the Al-based alloy film.

[0025]

According to the present invention, the evacuation of the sputter chamber after loading the substrate into the sputter chamber is performed only until the pressure in the sputter chamber becomes 5 × 10 ^{-5 to} 5 × 10 ^-4 Torr. Since a small amount of air is left in the sputtering chamber and nitrogen, oxygen, hydrogen, etc. in the remaining air are deposited together with the sputtered particles, even if heated to several hundred degrees Celsius, hillocks as well as side surfaces and edge portions of the coating will of course remain. Thus, a highly reliable Al-based alloy film which does not cause local projections in the step can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a sputtering apparatus.

FIG. 2 is a plan view after heating an electrode formed of an Al-based alloy containing only a high melting point metal.

FIG. 3 is an enlarged sectional view taken along the line III-III in FIG. 2;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Sputter chamber, 11a, 11b ... Closed door, 12 ... Exhaust pipe, 13 ... Sputter gas introduction pipe, 16 ... Substrate transfer mechanism, 17 ... Heater, 18 ... Target, 19 ... Sputter power supply, 20 ... Substrate, 21 ... Al-based alloy film.

Claims (1)

(57) [Claims] In forming an aluminum-based alloy film by a sputtering apparatus, after inserting a substrate into a sputtering chamber, air in the sputtering chamber is blown until the pressure in the sputtering chamber becomes 5 × 10 ^{−5 to} 5 × 10 ⁻⁴ Torr. After exhausting, a sputtering gas is introduced into the sputtering chamber and adjusted to a gas pressure of 3 × 10 ⁻³ to 8 × 10 ⁻³ Torr,
Aluminum alloy containing high melting point metal
Sputtering by supplying discharge current to the target.
Depending on the content of nitrogen, oxygen, hydrogen, etc.
A method for forming an aluminum alloy film, comprising forming an aluminum alloy film containing :