JPH07105486B2 - Electrode wiring material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an electrode wiring material used for various semiconductor elements and the like.

(Prior Art) In recent years, an active matrix type liquid crystal display element constituted by using a thin film transistor (TFT) using an amorphous silicon (a-Si) film as a switching element has been receiving attention. This is a large-area, high-definition, high-image-quality and inexpensive panel display (flat type television) by forming a TFT array using an a-Si film that can be formed at a low temperature using an amorphous glass substrate. ) May be realized. In order to make the display pixel of this active matrix type liquid crystal display element as small as possible and have a large area, it is necessary to make the gate wiring and the data wiring thin and long immediately to the signal line to the TFT. Moreover, the resistance must be sufficiently low in order to eliminate the waveform distortion of the pulse signal. For example, when a gate electrode wiring is formed on a glass substrate and an inverse stagger type TFT structure in which an insulating film or an a-Si film is stacked on the glass substrate to form a TFT, the gate electrode wiring is thin and sufficiently low. It is required to be a material that is resistant and can withstand subsequent chemical treatment.
Conventionally, as a gate electrode wiring material that meets such requirements,
Various metal films such as Ta and Ti are used, but in order to achieve a larger area and higher definition, a material with lower resistance, better workability, and excellent resistance to various chemical treatment processes is desired. It is rare. In the case of the staggered TFT structure in which the source / drain electrode wiring is provided on the substrate side, such characteristics are required for the source / drain electrode material. Similar problems also exist in the case of a liquid crystal display element that is not an active matrix type. On the other hand, a semiconductor integrated circuit using a single crystal Si substrate has the same problem. For example, memory integrated circuits represented by dynamic RAMs are becoming more and more integrated. Conventionally, an impurity-doped polycrystalline silicon film has been generally used for a gate electrode wiring of a MOS transistor used in such a memory integrated circuit. However, in order to further miniaturize and highly integrate the device, the polycrystalline silicon film has too high specific resistance. Mo is used as a material that has lower specific resistance than polycrystalline silicon films and can withstand high temperatures.
Si ₂ is known, but even if it is used, the resistance of the electrode wiring becomes a large problem when realizing a dynamic RAM of 1 Mbit or more, for example.

(Problems to be Solved by the Invention) As described above, in various conventional semiconductor elements, when an attempt is made to increase the area and the degree of integration, the resistance of the electrode wiring,
Workability and chemical resistance are major problems.

An object of the present invention is to provide an excellent electrode wiring material that solves such problems.

[Structure of the Invention] (Means for Solving the Problems) The electrode wiring material according to the present invention has a base metal film having a crystal structure of a body-centered cubic structure and a composition ratio of Ta formed on the base metal film. It is characterized by having a laminated structure of an alloy film of Mo and Ta of 84 atomic% or more.

The alloy film of Mo and Ta only needs to have a total amount of Mo and Ta of 95 atomic% or more, and it is permissible to include other elements such as C, O, Ar and N in the range of 5 atomic% or less. . V, Cr, Fe, Nb, Mo, W, Ta, etc. are used as the body-centered cubic metal used for the underlying metal film, and an alloy of Mo and Ta with a Ta composition ratio of 84 atomic% or less is used. You can also

(Function) The electrode material having a laminated structure in the present invention has a specific resistance lower than that of Ta, Mo, Ti or a single-layer Mo-Ta alloy film, and of course, a specific resistance far lower than that of the MoSi ₂ film. In addition, it has excellent workability, excellent resistance to various chemicals, and excellent ohmic contact with semiconductors such as Si.

The reason why the laminated structure electrode material of the present invention has low resistance is as follows. There are two types of Ta crystal structures, tetragonal and body-centered cubic. Tetragonal Ta is called β-Ta, and a thin film formed by ordinary vapor deposition, sputtering or the like has this crystal form. Body-centered cubic Ta is called α-Ta, and bulk metal takes this crystal form. In the Mo-Ta alloy, the thin film is usually tetragonal in the range where the composition ratio of Ta is large. However, when a Ta--Mo alloy film is formed on a body-centered cubic underlayer metal film as in the present invention, the alloy film reflects the crystal structure of the underlayer metal film even when the composition ratio of Ta is large. Becomes a cubic crystal.
As a result, low resistance electrode wiring can be realized despite the large Ta composition ratio.

(Example) Prior to the description of the example applied to a specific device,
The basic characteristics of the electrode material film of the present invention will be described according to experimental data. Ta-Mo with various composition ratios on glass substrate
An alloy film was formed by sputtering and its specific resistance was measured. The results are shown in FIG. The specific resistance is also shown for the case where the Ta-Mo alloy film is formed as a single-layer film on the glass substrate and the case where the Mo film is formed as the underlayer and the Ta-Mo alloy film is formed on this as a laminated film. . In the case of a single layer film, the composition ratio of Ta is 84
When it exceeds atomic%, the specific resistance rapidly increases. On the other hand, in the case of the laminated film, the specific resistance decreases as the composition ratio of Ta increases, and a remarkable difference from the case of the single layer film is recognized.

FIG. 5 shows the results of X-ray diffraction of a single layer film of these Ta-Mo alloy (Ta 84% or more) and a laminated film of Mo / Ta-Mo alloy (Ta 84% or more). From this result, it is confirmed that the Mo-Ta alloy single layer film in which Ta is 84% or more is tetragonal, whereas the laminated film on which the Mo film is a base is body-centered cubic. This difference in crystal structure is the large difference in specific resistance described above.

The chemical resistance of the Mo / Ta-Mo laminated film is almost the same as that of Ta when the composition ratio of Ta is 84% or more. That is, it is not attacked by various strong acids other than HF, such as HNO ₃ , H ₂ SO ₄ , HCl, and H ₂ O ₂ . Further, this laminated film could be easily etched by plasma etching using CF ₄ and O ₂ , and taper etching was also easy by selecting the gas mixture ratio and the applied RF power.

In addition to the Mo film as the underlying metal film, the same result was obtained when a Ta-Mo alloy film having a Ta composition ratio of 84 atomic% or less was used and further when V, Cr, Je, Nb, and W films were used. Was obtained.

The film forming method is not limited to the sputtering method, and may be used for an electron beam evaporation method or the like. Further, since the underlying metal film is mainly for determining the crystal structure of the laminated Ta-Mo alloy film, its thickness may be, for example, about 100Å or more.

Next, examples of specific elements using the electrode material of the present invention will be described.

FIG. 1 is an equivalent circuit of the Agtiou matrix type liquid crystal display device of one embodiment. Address wiring on the glass substrate 11
(11 _1, 11 _2, ...) and data lines 12 (12 _1, 12 _2, ...) is disposed Matorisuku shape, TFT 13 is disposed on the respective intersections. In the TFT 13, the gate is connected to the address wiring 11, the drain is connected to the data wiring 12, and the source is connected to the liquid crystal cell 14 via the pixel electrode. Although the storage capacity is shown in the figure, this can be omitted. The gate electrode of the TFT 13 is actually formed integrally with the address wiring 11.

FIG. 2 is a cross-sectional view of the main parts of the active matrix substrate. Gate electrode integrated with address wiring on glass substrate 21
22 is Ta-Mo film (Ta80%) 22 ₁ and Ta-Mo film (Ta95%) 22 ₂
It is formed by the laminated film of and becomes a gate insulating film on this
The SiO ₂ film 23 is deposited. On top of this, non-doped a-Si
A film 24 and an n ⁺ -type a-Si film 25 are deposited and patterned in an island shape in the TFT region. A source electrode 26 and a drain electrode 27 made of an Al film are formed on the patterned a-Si film. The drain electrode 27 is formed integrally with the data wiring 12 described in FIG. Although not shown in the figure, after the island-shaped a-Si film is formed, the ITO pixel electrode is formed adjacent to the island-shaped a-Si film, and the source electrode 26 is electrically connected to this pixel electrode.

A liquid crystal display device having a display area of 19.2 cm × 25.6 cm and a pixel pitch of 400 μm was manufactured with the above structure. Explaining the specific numerical values of each part, the gate electrode 22 has a base Ta-Mo film 22 ₁ of 300 Å
₂ is 1700Å. The address wiring 11 is the gate electrode 22.
And the width thereof was 30 μm. The electrode wiring was tapered by plasma etching using CF ₄ and O ₂ .

The resistance of the address wiring 11 thus obtained is 12.8.
It was kΩ. By the way, numerical examples when forming similar address arrangements using other electrode materials are 200.5 kΩ for Ti, 55.4 kΩ for Cr, 22.6 kΩ for Mo, 110.9 kΩ for Ta, Ta60%. In the case of the Mo-Ta alloy of, it was 19.2 kΩ.

After the address wiring is formed, the substrate is subjected to organic matter removal by a mixed solution of H ₂ SO ₄ + H ₂ O ₂ , washed, and the SiO ₂ film 23 is deposited by CVD to 1500Å, and then a-Si
The film 24 and the n ⁺ -type a-Si film 25 were deposited at 3000 Å and 500 Å, respectively. After patterning these a-Si films as described above,
A pixel electrode was formed, and a data line also serving as the drain electrode 26 of the TFT and a source electrode 27 were formed.

In the liquid crystal display element formed in this manner, almost no short circuit between the data wiring and the address wiring was observed. On the other hand, when Mo film was used as the address wiring, many short circuit accidents were observed. This is because the treatment with a strong acid such as H ₂ SO ₄ + H ₂ O ₂ cannot be performed, so that the adhered dust such as organic substances on the address wiring cannot be removed. Also
When Ti or Cr was used for the address wiring, taper etching was not possible, so the SiO ₂ film became thin at the wiring edge, and again many short-circuit accidents between the address wiring and the data wiring occurred.

The active matrix liquid crystal display device using the a-Si TFT has been described above.
The present invention is similarly applied to a liquid crystal display element using an M element, which is effective.

FIG. 3 shows a MOS transistor portion of an embodiment in which the electrode wiring material of the present invention is used for a gate electrode wiring portion of a MOS integrated circuit. The gate oxide film 32 of 30nm was formed by thermal oxidation isolation region of the p-type Si substrate 31 of resistivity several Omega · cm, MoSi film 33 ₁ of 200Å on this, 200Å of the Mo film 33 _2, followed 2000 Å
Mo-Ta alloy (Ta95 atomic%) were sequentially deposited film 33 _3, 900 ℃, ₃
Heat treatment for 0 minutes. As a result, the intermediate layer changes to a MoSi film. Then, this laminated film was taper-etched by plasma etching of CF ₄ and O ₂ to form a gate electrode wiring. Next, using the gate electrode as a mask, P ions were implanted at 100 keV at 1 × 10 ¹⁵ / cm ² and heat-treated at 1000 ° C. for 30 minutes to form source / drain regions 34 and 35. Finally, a CVD oxide film 36 was formed on the entire surface, contact holes were opened, and Al wirings 37 and 38 were formed.

The gate electrode wiring according to this example had a specific resistance of 1/5 as compared with the case where only the MoSi ₂ film was used, and a short gate delay time was obtained.

[Effects of the Invention] As described above, according to the present invention, by laminating a Mo-Ta alloy film on a base metal film having a body-centered cubic structure, the crystal structure of this alloy film has an extremely large Ta composition ratio. Also in this case, a very low resistance electrode wiring can be obtained as a body-centered cubic structure. Moreover, this electrode wiring material is easy to perform taper etching and the like, has excellent workability, and has excellent chemical resistance.

[Brief description of drawings]

FIG. 1 is an equivalent circuit diagram of an active matrix type liquid crystal display device according to an embodiment of the present invention, FIG. 2 is a sectional view of an essential part of the active matrix substrate, and FIG. 3 is a MOS transistor according to another embodiment of the present invention. FIG. 4 is a diagram showing the resistivity characteristics of the electrode wiring material of the laminated structure according to the present invention in comparison with a single layer film, and FIG. 5 is a diagram showing X-ray diffraction data similarly. 11 …… Address wiring, 12 …… Data wiring, 13 …… TFT, 1
4 …… Liquid crystal cell, 21 …… Glass substrate, 22 …… Gate electrode, 22 ₁ …… Ta-Mo (Ta80%) film, 22 ₂ …… Ta-Mo (Ta95
%) Film, 23 ... SiO ₂ film, 24 ... a-Si film, 25 ... n ⁺ type a
-Si film, 26 ... Source electrode, 27 ... Drain electrode, 31 ...
… P-type Si substrate, 32 …… Gate oxide film, 33 ₁ …… MoSi ₂ film,
33 ₂ …… Mo film, 33 ₃ …… Ta-Mo alloy film, 34 …… Source region, 35 …… Drain region, 36 …… SiO ₂ film, 37,38 …… Al
wiring.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 29/78 301 F 21/88 M

Claims (2)

[Claims] 1. A laminated structure comprising a base metal film having a crystal structure of a body-centered cubic structure and a Mo / Ta alloy film having a composition ratio of Ta of 84 atomic% or more formed thereon. An electrode wiring material characterized by. 2. The underlying metal film has a Ta composition ratio of 84 atomic%.
The electrode wiring material according to claim 1, which is the following alloy film of Mo and Ta.