JPH05226337A - Thin film wiring and its manufacture - Google Patents

Abstract

PURPOSE:To provide an Al wiring which can reduce the resistivity of wiring in a very thin film region like an SAW filter, improve migration resistance in a wiring having a film thickness larger than or equal to a specified value like an LSI, and a manufacturing method of the wiring. CONSTITUTION:Al or an Al alloy of amorphous state or fine grain texture is deposited on a substrate 1 and turned into a lower base layer 2. A two- layered film is formed by depositing an Al or Al alloy thin film 3 on the base layer 2. Thereby the orientation of the Al or Al alloy wiring is remarkably improved as compared with the case that Al or Al alloy is directly deposited, and the Al or Al alloy thin film wiring having low resistivity and high migration resistance can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film wiring and its manufacturing method.

[0002]

2. Description of the Related Art Surface acoustic wave (SAW) devices and LSIs
The metal wiring used for, for example, aluminum (Al), silicon (Si) and copper (Cu) in order to improve resistance to electromigration and stress migration.
When adding a trace amount, especially for LSI wiring,
A two-layer structure using a refractory metal such as titanium nitride (TiN) or tungsten (W) having a thickness of about 000Å as an underlayer is used.

[0003]

The film thickness of the wiring used for the SAW device in the high frequency band needs to be extremely thin as compared with that of the LSI, and is, for example, 500 Å or less in the GHz band. When Al or Al alloy is directly applied on a substrate for a SAW filter such as crystal, the resistance of the film increases extremely as the film thickness decreases. This is because in the initial stage of film growth, Al
Is grown in an island shape, and when the film thickness is thin, this is because the growth of crystal grains centering on the island is insufficient.

On the other hand, in the wiring of the LSI, in order to improve the reliability, an Al-based alloy in which Si or Cu is added in a trace amount to Al is used, and a refractory metal such as TiN of about 1000Å is used as an underlayer. However, even with such a laminated structure, it cannot be said that the reliability against electromigration is sufficient (eg, Proceeding of the 28th Reliability Physics Symposium, page 25, 1990).

It is known that a film having higher (111) orientation of Al has higher migration resistance (for example,
Shin Solid Films Vol. 75, p. 253 1
981). However, Al of (111) orientation is directly formed on the substrate.
Is not easy to deposit.

The object of the present invention is to reduce migration in a wiring having a low specific resistance even in an ultra-thin film region such as a SAW filter having a film thickness of about several hundred Å and having a film thickness of 5000 Å or more such as an LSI. Highly resistant Al
It is to provide a wiring and a manufacturing method thereof.

[0007]

In order to achieve the above object, the thin film wiring according to the present invention is a thin film wiring having an underlayer and a thin film, and the underlayer is made of aluminum having an amorphous or fine grain structure ( Al) to Al
An alloy thin film, the thin film being formed on the underlayer (1
11) An oriented Al or Al alloy thin film.

Further, the method of manufacturing a thin film wiring according to the present invention is a method of manufacturing a thin film wiring, which includes a base layer forming step and a thin film forming step, wherein the base layer forming step is cooled using liquid nitrogen. A step of depositing an Al or Al alloy on a substrate to form an Al or Al alloy thin film underlayer having an amorphous or fine grain structure. The thin film forming step is performed on the underlayer at a substrate temperature of room temperature or higher ( 11
1) A step of forming an oriented Al or Al alloy thin film.

A method of manufacturing a thin film wiring having an underlayer forming step and a thin film forming step, wherein the underlayer forming step performs ion implantation into an Al or Al alloy thin film to form an amorphous or fine grain structure. Al or A
This is a step of forming an l alloy thin film underlayer, and the thin film forming step is a step of forming an Al or Al alloy thin film of (111) orientation on the underlayer.

A method of manufacturing a thin film wiring having an underlayer forming step and a thin film forming step, wherein the underlayer forming step deposits an Al or Al alloy thin film on a piezoelectric substrate, and a piezoelectric film is formed during the deposition. This is a step of forming an Al or Al alloy thin film underlayer having an amorphous or fine grain structure by vibrating the substrate. In the thin film forming step, vibration of the piezoelectric substrate is stopped, and Al of (111) orientation is formed on the underlayer. Or a step of forming an Al alloy thin film.

[0011]

With Al deposited directly on the substrate, the interfacial energy between the substrate and Al is large, and therefore the smaller the surface area of the Al, the more advantageous in terms of energy.
Grain growth occurs in the initial stage of growth. The grain growth of Al in the initial stage of growth becomes polycrystalline because the crystal planes at that time are oriented randomly, and the (111) orientation does not improve no matter how much Al is deposited thereafter.

However, Al deposited on an amorphous or fine-grained aluminum (Al) or Al alloy thin film underlayer has a small interfacial energy with the underlayer, and therefore does not become granular in the initial stage of growth. , Grows flat. Further, since the base has an amorphous or fine grain structure, it is not affected by the plane orientation of the base,
Al (111) having the smallest surface energy of Al
Will be a uniaxially oriented film.

This growth mode does not change even if the Al film thickness increases. As a result, the resistance value of the thin film does not increase even in the ultra-thin film wiring required for the high-frequency SAW filter. Further, since the Al (111) orientation is extremely strong, migration resistance is improved.

[0014]

EXAMPLES The present invention will be described below with reference to examples. FIG. 1 is a schematic sectional view of a thin film wiring according to the present invention. In the figure, an Al or Al alloy 2 having an amorphous or fine grain structure is deposited as a base layer on a substrate 1, and Al having a (111) orientation or an Al alloy containing a small amount of Si, Cu or the like is added to the base layer 2. The film 3 has been deposited.

Next, as a method for producing the thin film wiring of the present invention, an Al alloy underlayer having an amorphous or fine grain structure is formed by depositing an Al alloy on a substrate cooled with liquid nitrogen using an ion beam sputtering apparatus. An example of forming will be described.

The ion beam sputtering apparatus includes an ion beam source, a substrate, an Al or Al alloy target,
A shutter for opening and closing the sputtered particle flux protruding from the target, a crystal oscillator film thickness meter for monitoring the film thickness, and a reflection high-energy electron diffraction film for evaluating the surface structure of the film formed on the substrate. It is composed of an electron gun and a fluorescent screen, and the inside of the device is evacuated by a cryopump through a gate valve. Argon gas was used as the sputtering gas. First, the inside of the device is 1 × 10 ^-7
After exhausting to Torr, argon pressure is 2 × 10 ⁻⁴ Tor
Sputtering was performed as r. A pipe was passed through the substrate holder to introduce liquid nitrogen so that the substrate could be cooled to the liquid nitrogen temperature without breaking the vacuum.

First, the substrate temperature is set to liquid nitrogen temperature (77 K) and Al-0.5 wt. Deposit 10% of Cu alloy, R
After confirming that HEED has a halo pattern and Al has an amorphous or fine grain structure, the substrate temperature is set to room temperature and Al-0.5 wt. % Cu alloy was deposited at 200Å, and this was simply deposited on a room temperature substrate by Al-0.5 wt. % Cu alloy 200Å, reflection high-energy electron diffraction (RHEED) and Al (111) were compared by X-ray diffraction. A quartz substrate was used as the substrate.

The Al alloy film simply deposited on the room temperature substrate was polycrystalline, whereas when it was deposited on the Al alloy having an amorphous or fine grain structure, the [111] crystal axis of Al was formed. Were vertically aligned on the quartz substrate (11
1) The orientation was confirmed by RHEED. A comparison of the X-ray diffraction intensities of Al (111) is shown in FIG. As can be seen from FIG. 2, the orientation degree of the Al alloy thin film on the Al alloy having an amorphous or fine grain structure was extremely improved as compared with the case where it was simply deposited on the room temperature substrate. Further, this (111) highly oriented Al on Al having an amorphous or fine grain structure does not grow like islands even in an ultra-thin film region such as 200Å, and (111) which is the densest surface of Al grows. To do.

Therefore, the specific resistance of the film becomes smaller than that in the case where Al is directly grown on the substrate at room temperature. For example, with a 500Å Al film deposited directly on a quartz substrate,
While the specific resistance was 4.5 μΩ · cm, the specific resistance was 3.0 μΩ · cm in the Al film having the same thickness on the 10 Å amorphous or fine grain structure Al.

Next, in order to investigate the effect when the layer thickness of the Al alloy layer having an amorphous or fine grain structure is changed,
The thickness of the amorphous or fine grained Al alloy layer is varied within the range of 2 to 1000Å, and the film thickness is 30
0Å Al-0.5 wt. % Resistivity of Cu film deposited, and 300 Å, 1 μm Al-0.5w
t. The full width at half maximum (Δθ) of the rocking curve of the Al (111) peak of the% Cu film and the results of the electromigration test are shown in FIGS. 3, 4 and 1, respectively. As the substrate, silicon (100) with a thermal oxide film was used,
Al on an Al alloy with an amorphous or fine grain structure
The substrate temperature was 100 ° C. when depositing the alloy.

As a comparative example, a case where an Al alloy was directly grown on a substrate at a substrate temperature of 100 ° C. was also examined. The electromigration test was performed using a test pattern in which the total length of the current flowing portion was 2 cm, the line width was 1.0 μm, and the distance between the lines was 2.0 μm. Temperature 250 ℃, current density 2.0 × 10 ⁶
A test was performed on 100 samples each under the condition of A / cm ² , and it was examined how long it took for 50% of the samples to break.

[0022]

[Table 1]

From the above results, regardless of the thickness of the Al layer having an amorphous or fine grain structure, the resistivity of the 300 Å film is extremely lower than that when the Al alloy is directly deposited on the substrate. In general, the thicker the film, the more Al
Although the orientation of (111) is high and the electromigration resistance is high, the orientation of Al (111) is extremely high in both cases of 300 Å and 1 μm as compared with the case where there is no Al layer having an amorphous or fine grain structure. It is high, and it can be seen that the electromigration resistance becomes extremely large.

Next, the same experiment was carried out in the case of changing the method for forming the amorphous or fine-grained Al layer and forming the amorphous or fine-grained Al by ion implantation. In this example, a vacuum vapor deposition apparatus was used.

The vacuum vapor deposition apparatus used in this embodiment is pure Al.
Electron beam evaporation source filled with, a shutter for opening and closing the molecular beam flux from the evaporation source, a crystal oscillator film thickness meter for monitoring the film thickness, for evaluating the surface structure of the film formed on the substrate It consists of an electron gun for reflection high-energy electron diffraction and a fluorescent screen. A glass substrate was used as the substrate.

The inside of the apparatus is evacuated by a turbo molecular pump through a gate valve. First, the inside of the device is 1 × 10
After evacuation to ^-7 Torr, Al was vapor-deposited.
The degree of vacuum during vapor deposition was 1 to 8 × 10 ^-6 Torr.

When Ar ions were implanted at an accelerating voltage of 10 kV after 100 Å vapor deposition of Al, it was confirmed by RHEED that the polycrystal Al thin film changed to an amorphous state or a fine grain structure immediately after vapor deposition.

After that, Al was vapor-deposited again at 300 Å. When deposited on Al having an amorphous or fine grain structure, RHEED indicates that the [111] crystal axes of Al are vertically aligned on the quartz substrate.
Was confirmed by.

FIG. 5 shows a comparison of the X-ray diffraction intensities of Al (111) obtained by simply depositing 300 Å Al on the substrate. Also by this manufacturing method, it is found that the Al (111) orientation is extremely high in the Al thin film on the amorphous or fine grained Al.

Next, by depositing Al on the piezoelectric substrate and then depositing the Al alloy on the vibrating substrate, Al having an amorphous or fine grain structure was produced, and the same experiment was conducted. A magnetron sputtering apparatus was used as the film forming method. The magnetron sputtering apparatus used in the present example was made of Al-2.0 wt.
% Si alloy, LiNbO ₃ substrate, a shutter provided between the substrate and the target, and a quartz oscillator film thickness meter for monitoring the film thickness. It is evacuated by a cryopump through the gate valve. Argon gas was used as the sputtering gas.

First, the inside of the apparatus was evacuated to 1 × 10 ^-7 Torr and then sputtered at an argon pressure of 3 to ⁷ mTorr. While vibrating the substrate at a frequency of 800 MHz, Al
An alloy was deposited and it was confirmed by X-ray diffraction that this Al alloy thin film had no diffraction peak.

Therefore, while vibrating the substrate at a frequency of 800 MHz, Al of amorphous or fine grain structure is used.
Deposit alloy 10Å, then stop the vibration of the substrate
1 Å alloy was deposited. Simply Al 5000 Å
FIG. 6 shows a comparison of the Al (111) X-ray diffraction intensity with that of the deposited case. Even by this manufacturing method, the Al thin film on Al having an amorphous or fine grain structure is Al (111)
It can be seen that the orientation is extremely high.

It was examined what happens to the film resistivity and migration resistance when an amorphous or fine grained Al alloy is produced by ion implantation or substrate vibration. According to the method described above, each of Al-0.5 wt. After depositing 10Å% Cu alloy, Al-0.5 with a film thickness of 300Å
wt. % Film resistivity when a Cu film is deposited, and
300 Å, 1 μm Al-0.5 wt. % Cu film Al
Full width at half maximum (Δθ) of rocking curve of (111) peak
Table 2 shows the results of the electromigration test.

Silicon (100) with a thermal oxide film was used as the substrate, and the substrate temperature was 100 ° C. when the Al alloy was deposited on the Al alloy having an amorphous or fine grain structure. As a comparative example, a case where an Al alloy was directly grown on the substrate at a substrate temperature of 100 ° C. was also examined. In the electromigration test, the total length of the current flowing part is 2 cm, the line width is 1.0 μm,
The test pattern was performed such that the distance between the lines was 2.0 μm. Temperature 250 ℃, current density 2.0 × 1
A test was conducted on 100 samples under the condition of 0 ⁶ A / cm ^{2 and} it was examined how long it took for 50% of the samples to break.

[0035]

[Table 2]

From the above results, the resistivity of the film of 300 Å was obtained by directly depositing the Al alloy on the substrate, as in the case where the amorphous or fine grained Al alloy was deposited on the liquid nitrogen temperature substrate. It becomes extremely lower than that of time, and generally, the thicker the film, the higher the orientation of Al (111) and the higher the electromigration resistance. However, even in the case of 300 Å or 1 μm, the amorphous or fine grain structure of Al It can be seen that the orientation of Al (111) is extremely high and the electromigration resistance is extremely high as compared with the case without the layer.

In the above embodiments, quartz, thermally oxidized silicon,
I mentioned LiNbO ₃ or glass substrate, but L
Similar effects were observed on other substrates such as iTaO ₃ , ZnO, Si and GaAs.

[0038]

As described in the above embodiments, according to the present invention, the crystal orientation of Al or Al alloy-based wiring is remarkably improved, and the electrical characteristics and migration resistance are greatly improved. In a wave device, particularly in a high frequency band filter, loss is reduced by lowering wiring resistance, and product yield is improved. Also,
As wiring for LSI and the like, reliability against electromigration and the like is improved. This effect is similarly exhibited when the Al or Al alloy thin film is deposited after depositing the metal film or when both are simultaneously deposited.

[Brief description of drawings]

FIG. 1 is a schematic view of a thin film wiring according to the present invention.

FIG. 2 Al (111) deposited on a liquid nitrogen temperature substrate with or without an amorphous or fine-grained underlayer.
It is a graph which shows the comparison of X-ray diffraction intensity.

FIG. 3 is a diagram showing an Al alloy layer thickness dependence of an amorphous or fine grain structure of a film resistivity.

FIG. 4 is a diagram showing the Al alloy layer thickness dependence of the amorphous or fine grain structure of the rocking curve full width at half maximum of Al (111).

FIG. 5: Al (11) with or without an Al underlayer having an amorphous or fine grain structure generated by ion implantation
1) A diagram showing a comparison of X-ray diffraction intensities.

FIG. 6 Al (111) depending on the presence or absence of an Al alloy underlayer having an amorphous or fine grain structure deposited on a vibrating substrate.
It is a figure which shows the comparison of X-ray diffraction intensity.

[Explanation of symbols]

1 substrate 2 Al or A having an amorphous or fine grain structure
l Alloy underlayer 3 Al or Al alloy film

─────────────────────────────────────────────────── ───Continued from the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H03H 9/145 Z 7259-5J

Claims (4)

[Claims] 1. A thin film wiring having an underlayer and a thin film, wherein the underlayer is an aluminum (Al) or Al alloy thin film having an amorphous or fine grain structure, and the thin film is formed on the underlayer. Al with (111) orientation
Or a thin film wiring comprising an Al alloy thin film. 2. A method of manufacturing a thin film wiring comprising an underlayer forming step and a thin film forming step, wherein the underlayer forming step comprises depositing Al or Al alloy on a substrate cooled with liquid nitrogen. Is a step of forming an Al or Al alloy thin film underlayer having an amorphous or fine grain structure. In the thin film forming step, an Al or Al alloy thin film of (111) orientation is formed on the underlayer at a substrate temperature of room temperature or higher. A method of manufacturing a thin film wiring, which is characterized by the following steps. 3. A method of manufacturing a thin film wiring comprising an underlayer forming step and a thin film forming step, wherein the underlayer forming step carries out ion implantation into an Al or Al alloy thin film to form an amorphous or fine grain structure. Is a step of forming an Al or Al alloy thin film underlayer, wherein the thin film forming step is a step of forming an Al or Al alloy thin film of (111) orientation on the underlayer. Method. 4. A method of manufacturing a thin film wiring comprising an underlayer forming step and a thin film forming step, wherein the underlayer forming step deposits an Al or Al alloy thin film on a piezoelectric substrate, and a piezoelectric film is formed during the deposition. This is a process of forming an Al or Al alloy thin film underlayer having an amorphous or fine grain structure by vibrating the substrate. In the thin film forming process, vibration of the piezoelectric substrate is stopped, and (111) -oriented Al is formed on the underlayer. Or a step of forming an Al alloy thin film, a method of manufacturing a thin film wiring.