JPH05259163A - Alumininum thin film - Google Patents

Abstract

PURPOSE:To increase or single-crystallize a crystal particle size of an Al film and decrease scattering of electrons in a grain boundary to obtain a wiring Al film having the long life by a method wherein a C-face orientation film composed of titanium or a thin film composed of gold is used as a ground layer or the like. CONSTITUTION:In a wiring aluminum thin film of a semiconductor device, a C-face orientation film composed of titanium, a thin film composed of gold, or a thin film composed of gold which is formed on a C-axis orientation film composed of ZnO is used as a ground layer. It is favorable that a thickness of the C-face orientation film composed of titanium or the thin film composed of gold is set at 500Angstrom or less. For instance, by using an RF sputter device, the C-face orientation film composed of Ti is formed so as to be 200Angstrom on a Si wafer and a thickness in an Al-Si(1%)-Cu(0.5%) is formed so as to be 6000Angstrom on a Ti film. Alternatively, by using vacuum vapor depositor, a thin film of Au is formed so as to be 100Angstrom on the Si wafer and next Al is vapor- deposited on the Au thin film in a condition of a substrate temperature 130 deg.C to form a film having a thickness 6000Angstrom .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum thin film widely used as a wiring material in semiconductor devices.

[0002]

2. Description of the Related Art Although an Al thin film used as a wiring material for a semiconductor device such as a semiconductor integrated circuit constitutes a polycrystalline film, it is considered that crystal grains should have a large life for wiring. There is data that lifespans are proportional (eg, S. Vaidyaand AK Sin
ha: Effect of texture and grain structure on electromigration in Al-0.
5% Cu thin films, Thin Solid Films,
vol. 75, no. 3 (1981) 253, especially the third
See figure).

In particular, when a film without grain boundaries is formed by using Al as a single crystal film, the film is free from electron scattering at the grain boundaries and has no defects (lattice defects or voids) in the film, so that the life is extended. To do. Then, in order to make a single crystal, a proposal is made such that heating is performed after manufacturing. Furthermore, in order to improve the durability of the Al film, Al-Si or Al-Si-Cu alloy may be used.

[0004]

The Al thin film, which is widely used as a wiring material in semiconductor devices, has become narrower in wiring width and thinner in film thickness with higher integration of devices. Therefore, a highly reliable and long-lifetime Al film is required. That is, it is required that the wire is not broken even if a current is applied for a long time. For this reason, there is data that the film has no defects, the crystal grain size is as large as possible, grain boundaries are reduced in the wiring, and the electron scattering is smaller, the life is longer.

According to the present invention, the crystal grain size of this Al film is increased, and even if it is made into a single crystal, the scattering of electrons at the grain boundaries is greatly reduced, and a long-lifetime Al film for wiring is obtained. The purpose is to

[0006]

[Means for Solving the Problems] The present invention has the following constitution in order to achieve the above object. That is, the first invention of the present invention is summarized as an aluminum thin film for wiring of a semiconductor device, which is characterized in that a C-plane orientation film of titanium is used as an underlayer, and
A second aspect of the present invention is a gist of an aluminum thin film for wiring in a semiconductor device, characterized in that a gold thin film is used as a base layer.

The components used in the aluminum thin film of the present invention will be described below. The lattice type of Al is f ・ c ・ c
And the lattice constant is 4.041Å and the electrical resistivity is 2.6.
It is 6 × 10 ⁻⁸ Ω · cm (20 ° C.). The lattice spacing of the (111) plane is 2.338Å, and that of the (220) plane is 1.43.
It is 1 Å. By the way, when this Al is formed as a thin film on a substrate such as a Si wafer, the Al (111) and Al (220) grow parallel to the substrate surface. When the intensity ratios of the two peaks are compared by the X-ray diffraction method, it is (220) / (111) = 1 / 10-10 / 1 /
40, and Al (111) is stronger. That is, Al makes a slight angle with the (220) plane parallel to the substrate,
The (111) plane grows parallel to the substrate. The smaller the value of (220), the smaller the electron scattering at grain boundaries and the longer the life.

The reason why the plane parallel to the substrate surface is determined in this way is that the (111) plane in the Al crystal plane has the highest atomic density, the lowest surface energy, and the second (220). ). That is, it can be said that (111) is the most stable at the time of film formation and is easy to grow. This ratio changes depending on film forming conditions such as substrate heating.

By the way, although the crystal type of Ti is h.cp.p, the lattice spacing of the C plane is very close to that of Al above 2.34.
It is 2Å. The mismatch is only 0.2%. For this reason, when a C-axis oriented film of Ti is formed as a base layer and Al is formed thereon, only the Al (111) plane is the base Ti layer.
Epitaxial growth is performed along the (002) plane. Moreover, Ti is a film that is easily oriented, and a high-quality oriented film can be easily manufactured. A for the Al film formed on the Ti orientation film
l (220) decreases, and the (220) / (111) X-ray intensity ratio becomes almost zero. Further, since the film is epitaxially grown, the number of defects in the film is small and the occurrence of voids is greatly reduced. Also, the crystal grain size of Al becomes large, and a film almost like a single crystal is formed. Conventional particle size is 0.1
It becomes 3 μm or more for 2 μm. However, since the physical properties of Al and Ti are different in some cases, it is better to reduce the thickness of Ti. In the present invention, it can be adjusted according to the purpose between 50 and 500Å. By improving the film quality (decreasing defects), increasing the grain size, etc., a wide and long life wiring can be obtained. The thickness of Al is generally 0.1 to 1 μm. In the present invention, the substrate material is not a problem and there is no limitation. Even in the case of glass, a C-axis oriented film of Ti can be easily obtained.
The Ti and Al films may be formed under general film forming conditions, and the vacuum deposition method, sputtering method, ion plating method, and CVD method are used.

As described above, the lattice type of Al is f · c · c, the lattice constant is 4.041Å, and the electrical resistivity is 2.66.
× 10 ⁻⁸ Ω · cm (20 ° C.). A used in the present invention
u (gold) is similar to this Al and has f · c · c, a lattice constant of 4.070Å, and an electric resistivity of 2.44 × 10.
^{At -8} Ω · cm (20 ° C), the thermal conductivity and linear expansion coefficient are also close. By the way, when a film is formed on a substrate such as Si (silicon) in order to use Al as a thin film, a plane parallel to the substrate becomes Al (111) or Al (220). Al (1
11) and Al (220) X-ray diffraction intensity is (220) /
(111) = 1/10 to 1/40 Al (11
1) is strong. The reason why Al (111) is oriented parallel to the substrate is considered to be because the (111) crystal plane of Al has the highest atomic density, and therefore the energy when the plane is grown becomes the minimum. .. The (220) plane has the second highest atomic density. The ratio of (220) / (111) changes depending on film forming conditions such as substrate heating.

As described above, Au has the same crystal type as Al, and the lattice spacing of the (111) plane is 2.3 for Al.
38Å and Au is 2.355Å. (220) is Al
Is 1.431Å and Au is 1.442Å. Therefore,
For the above reason, when Au is provided on the substrate as a thin film similarly to Al, (111) is oriented parallel to the substrate.
In the case of Au, the X-ray diffraction intensity is (220) / (111) ≈0
Therefore, the orientation is greatly improved as compared with Al. This is true even if the substrate is amorphous such as glass.

The present invention has been made on the basis of the above points. When providing Al for wiring, an Au film is previously provided as a base layer on the surface of a substrate or a film to be provided, and then Al (or generally used) is provided. Al-Si, Al-S
When a thin film (which may be an i-Cu alloy or the like) is provided, the Al thin film is (111) oriented and (220) does not grow, or (220) is greatly reduced compared to the conventional case. This phenomenon is generally called epitaxial growth, in which Al atoms are affected by the arrangement of Au atoms and undergo similar orientation to grow.

For this reason, the particle size is 0.1 to several .mu.m of the conventional one.
However, the electron scattering at the grain boundaries is reduced and the life is extended. In this case, since Al and Au are close to each other in terms of characteristics, no particular problem occurs. The Al thin film is generally used in a thickness of 0.1 to 1 μm, whereas the Au thin film is 500 Å or less, preferably 100 Å.
Used below. It may be less than this, but it should be noted that the unevenness of the film becomes large.

If a C-axis orientation film of ZnO is further provided under Au if there is no particular influence, (220) / (11) of Au is formed.
1) becomes 0, so that (220) cannot be seen in the Al thin film either. The film forming method may be a general film forming method such as a vacuum vapor deposition method, a sputtering method, an ion plating method, a CV method.
The D method or the like is used.

[0015]

EXAMPLES The present invention will be described in detail below with reference to examples.

Example 1 A Ti thin film having a thickness of 200 Å was formed on a Si wafer by using an RF sputtering apparatus. The manufacturing conditions were as follows. Base pressure 6 × 10 ⁻⁷ Torr Target Ti (99.99%) Target substrate distance 50 mm Substrate temperature 400 ° C. Introduced gas pressure Ar 5 × 10 ⁻³ To
The X-ray diffraction peak of rr high-frequency power 150 W Ti was only from the C plane of (002) and (004), and the full width at half maximum of the (002) peak was 1.7 degrees, indicating a good alignment film. A on this Ti film
l-Si (1%)-Cu (0.5%) with a thickness of 6000Å
It was manufactured so that The production conditions are shown below. Base pressure 6 × 10 ^-7 Torr target Al-Si (1%)-C
u (0.5%) Distance between target substrates 45 mm Substrate temperature 130 ° C. Introduced gas pressure Ar 5 × 10 ⁻³ To
The X-ray diffraction peaks of rr high-frequency power 120 W Al were only Al (111) and (222). The average crystal grain size of Al measured by the TEM method was 4 μm. Then, the wiring with a width of 2 μm is etched to obtain MTF (Time to fail
When re) was measured, it was 1400 hours.

COMPARATIVE EXAMPLE 1 S was prepared in the same manner as in Example 1 except that the Ti underlayer was not provided.
An Al-Si-Cu film was formed on the i-wafer. X-ray diffraction peaks are Al (111), (222) and Al (220)
Was observed and the intensity ratio of (220) / (111) was about 1 /
It was 30. The average crystal grain size was 0.6 μm, which was smaller than that in Example 1, and the MTF was as short as 650 hours.

Example 2 An Au thin film was formed on a Si wafer by using a vacuum vapor deposition apparatus.
The film was formed so as to be 00Å. The substrate is heated to 300 ° C,
The base pressure was 3 × 10 ⁻⁷ Torr. The film forming speed was 5 Å / min. When measured by X-ray diffractometry, the diffraction peaks from Au show Au (111), Au
Only (222) was observed. Then, Al was vapor-deposited on the Au thin film at a substrate temperature of 130 ° C.
The film-forming speed was 8 Å / min and the film was formed to a thickness of 6000 Å. X-ray diffraction peaks are Al (111), Al (222)
I could only observe it. When the crystal grain size of Al was measured using the TEM method, it was 3.3 μm on average. Then, the wiring with a width of 2 μm is etched to obtain MTTF (media).
It was 1,500 hours when n time to failure was measured.

Example 3 Using a RF sputtering apparatus, a ZnO film having a thickness of 500 Å was formed on a Si wafer under the following conditions. Base pressure 7 × 10 ⁻⁷ Torr Target substrate distance 50 mm High frequency power 200 W Target Zn (99.999%) Substrate temperature 250 ° C. Inlet gas pressure O ₂ 2 × 10 ⁻³ Tor
The X-ray diffraction peak of the r Ar 5 × 10 ⁻³ Torr ZnO film is only from the C-plane of (002) and (004), and the half-width of the (002) peak is 1.5 degrees, which is a good orientation film. Met. An Au film was formed on this ZnO film in the same manner as in Example 2. The X-ray diffraction peaks were only Au (111) and (222). Al-Si (1%)-Cu (0.5%) as in Example 2.
Was prepared. The substrate temperature was 130 ° C. The X-ray diffraction peaks were only Al (111) and (222).
The average crystal grain size of Al was 4.2 μm. MTTF was 1920 hours.

Comparative Example 2 An Al thin film (6000 Å thickness) was produced on a Si wafer in exactly the same manner as in Examples 2 and 3 except that no Au layer or ZnO layer was provided. The X-ray diffraction peaks of both samples were Al (11
1), (222) and Al (220) were observed,
0) / (111) was 1/26. The average crystal grain size is 0.8 μm, which is smaller than those in Examples 2 and 3, and MT
TF was 790 hours and 960 hours, which was short.

[0021]

According to the aluminum thin film of the first invention, a thin C-axis oriented film of Ti is provided as an underlayer in the production of an Al thin film for wiring, so that a high quality epitaxially grown Al thin film can be obtained, and the grain size can be increased. Becomes large and becomes a single crystal, and therefore the life is greatly extended. According to the aluminum thin film of the second invention, since the Au oriented thin film is provided as the underlayer in the production of the Al thin film for wiring, the crystal grain size of the Al film is increased, and the crystal film becomes a high quality crystalline film for epitaxial growth. A film having no defects or voids can be produced, and therefore the life is greatly extended.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI Technical display location H01B 5/14 Z H01L 29/46 R 7738-4M L 7738-4M H05K 3/38 B 7011-4E

Claims (7)

[Claims] 1. An aluminum thin film for wiring of a semiconductor device, wherein a C-plane orientation film of titanium is used as an underlayer. 2. The titanium C-plane alignment film has a thickness of 500.
The aluminum thin film according to claim 1, wherein the thickness is Å or less. 3. The aluminum thin film according to claim 1, having an Al (111) / Ti (002) crystal structure. 4. An aluminum thin film for wiring in a semiconductor device, wherein a gold thin film is used as a base layer. 5. The aluminum thin film according to claim 4, wherein the thickness of the gold thin film is 500 Å or less. 6. The aluminum thin film according to claim 4, wherein a C-axis alignment film of ZnO is further used as the underlayer. 7. The aluminum of the underlayer is Au.
The aluminum thin film according to claim 4, which is epitaxially grown on the (111) plane.