JPH0949041A - Semiconductor circuit material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a circuit material of a semiconductor integrated circuit excellent in electromigration resistance and having low electric resistance by alloying Al with a small amt. of Ta. SOLUTION: A thin Al-Ta alloy film of about 5,000Å thickness is formed on a thermally oxidized Si substrate by a sputtering method using a target made of an Al alloy contg. 0.003-0.1at.% Ta as a solid soln. strengthening element. The objective semiconductor circuit material excellent in electromigration resistance, having low electric resistivity, adaptable even to the narrowing of a circuit required by high integration of a semiconductor device and not causing breaking is produced with superior productivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wiring material suitable for use in electrodes of a semiconductor integrated circuit (MOS semiconductor device, etc.) and connection wiring between the electrodes.

[0002]

2. Description of the Related Art In recent years, semiconductor integrated circuits have tended to be miniaturized as semiconductor devices (semiconductor devices in which elements are formed on a Si wafer) are rapidly miniaturized and highly densified. Electrodes used in the integrated circuit of the semiconductor device
As the wiring material, a thin film type Al-based metal material is mainly used, and the material is roughly classified into pure Al and an Al-based alloy containing Si or Cu.

The reason why the Al-based metal material is frequently used as the electrode / wiring material in this manner is that an inexpensive and high-purity material is available, the electrical resistivity is low, and a good ohmic contact with Si can be formed. , A high selection ratio to a photoresist, easy microfabrication, good corrosion resistance, and the like.

The biggest problem with the Al-based metal wiring material is how to prevent the occurrence of electromigration (hereinafter abbreviated as EM) (that is,
It means that the EM resistance is improved). EM here
Is a phenomenon in which, under high current density, Al atoms obtain kinetic energy by friction with electrons and move in the electron moving direction, and as a result, voids (atomic vacancies) are formed between wirings.
Occurs, which causes an increase in electrical resistivity, and the voids eventually grow and eventually lead to disconnection.

Generally, in the case of Al-based metal wiring, since Al has a polycrystalline structure, the movement of Al atoms at the temperature (room temperature to 150 ° C.) at the actual operation level causes the grains to propagate through the grain boundaries of Al. World diffusion is dominant. Therefore, it is considered that blocking (covering) the grain boundary, which is the main diffusion path of Al atoms, with a precipitate or the like is a useful means for improving the EM resistance.

From this point of view, an Al-based alloy wiring material containing Si or Cu was developed to avoid problems such as voids and disconnection due to the EM phenomenon. That is, Al
Si and Cu added therein are precipitated as intermetallic compounds in the grain boundaries to block the grain boundary diffusion path of Al atoms.

However, according to the above concept, E
In order to completely prevent the M phenomenon, it is necessary to cover all the grain boundaries of polycrystalline Al, which is the parent phase, with precipitates, but in reality, it is extremely difficult to strictly control such a structure. Therefore, if all the grain boundaries are covered with precipitates, it becomes necessary to add a large amount of alloying elements, which causes a problem that the electrical resistivity increases in high Al alloy wiring. That is, in general, a metal tends to have an increased resistance value due to alloying, but on the other hand, the allowable upper limit value of the electric resistivity is reduced due to the miniaturization of wiring (narrowing of wiring width) accompanying the recent high integration of semiconductor devices. It is becoming lower and lower, and it is desired that the wiring resistance be about 3.5 μΩ · cm or less. Therefore, the addition of a large amount of alloying elements as described above is contrary to the recent required characteristics of semiconductor wiring materials such as reduction of wiring resistance value.

Therefore, a semiconductor wiring material using an alloy element which has a low solubility in Al as a matrix and which does not significantly increase the electrical resistivity of the Al alloy is disclosed in JP-A-62-235.
No. 451. Specifically, Al-Ti-
B-Me (Me is Cu, Cr, Co, Mn, Ni, H
(meaning at least one element selected from the group consisting of f, Sn, In, Ta, Au, and Ag)), and the metal element represented by Me is 0.0001. .About.0.02 wt%. That is, these metal elements are originally known to be effective in preventing voids and disconnection due to EM, and the intermetallic compound TiB ₂ particles formed by adding Ti and B similarly prevent grain boundary diffusion. Since the effect is excellent, it is intended to further enhance the grain boundary diffusion preventing effect by combining the two. However, even with such a material, sufficient EM resistance has not yet been obtained.

In addition, multi-layered wiring and alloying of the wiring surface portion by ion implantation (surface-alloyed wiring) have been proposed. Of these, the multilayer wiring has a laminated structure in which a refractory metal such as Ti or W, a refractory nitride, a refractory silicide, or the like is arranged on both sides (lower layer and upper layer) of the Al-based alloy material in the central portion, With such a configuration, even if the Al-based alloy wiring in the central portion is broken, the wiring failure in the lower layer and the upper layer is prevented by energizing the wiring in the lower layer and the upper layer to prevent the E-resistant wire.
It is intended to improve the M property. On the other hand, the surface-alloyed wiring is one in which a different element is ion-implanted into a low-resistance wiring material and an EM-resistant alloy layer is provided on the surface portion of the wiring material. It is a thing.

However, in the case of the multi-layer wiring, it is necessary to form the film a plurality of times during the manufacturing, and it is necessary to perform the etching for forming the wiring pattern in a separate step depending on the combination of the lower layer and the upper layer. It causes problems such as increase and decrease of production efficiency. On the other hand, in the case of surface alloyed wiring, a complicated process of ion implantation is required,
Moreover, since it is difficult to control the surface alloy layer, there are problems such as an increase in the number of manufacturing steps and a decrease in production yield.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to have excellent EM resistance, low electric resistivity, and without impairing productivity. It is an object of the present invention to provide a novel semiconductor wiring material capable of coping with the situation such as narrowing of the wiring width due to the high integration of semiconductor devices in recent years.

[0012]

The semiconductor wiring material of the present invention which can solve the above problems has a Ta value of 0.00
The gist is that the content is 3 at% or more and less than 0.1 at% and the balance is Al and inevitable impurities. Such a wiring material is preferably produced by a sputtering method using an Al-based alloy having the above-mentioned composition as a target material. By applying the sputtering method, grain boundary diffusion of Al atoms by solid solution strengthening described later is achieved. Can be efficiently suppressed, and the EM resistance can be further enhanced.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION As a method for avoiding the problems such as voids and disconnection due to EM, in addition to the method of blocking the grain boundary, which is the main diffusion path of Al atoms, with a precipitate or the like, solid solution is also available. A method of suppressing grain boundary diffusion of Al atoms by strengthening or the like can be considered. That is, if the grain boundary diffusion of Al atoms is suppressed by adding a solid solution strengthening element to the Al alloy, the self-diffusion activation energy of Al in each diffusion path is increased, and as a result, the diffusion transfer of Al atoms is suppressed. You can do it.

Based on such an idea, the present applicant has conducted extensive studies, and as a result, Ti and Ta are effective as the solid solution strengthening elements, and the total amount of these elements is 0.1 to 5a.
A semiconductor device material made of an Al-based alloy containing t% is resistant to E
We obtained the knowledge that it has excellent M resistance and corrosion resistance, and low electrical resistance, and filed an application for it in advance (Japanese Patent Application No. 3-92).
250). That is, in this publication, Ti and / or Ta are used for the purpose of obtaining a material having the above various characteristics.
As a result of conducting an experiment by changing the concentration of the element within the range of 0 to 10 at%, the concentrations of these elements were determined, and detailed examination was added particularly in the region of 0.1 at% or more. However, as a result of further investigations conducted by the present inventors after the above-mentioned application, it was surprisingly found that the Ta concentration was extremely low (that is, the detailed study was not performed in the above publication.
In a region of less than 1 at%), it has been found that it has particularly excellent EM resistance, and as a result of repeated studies on EM resistance and electric resistivity at a Ta concentration of less than 0.1 at%,
The present invention has been completed.

That is, the semiconductor wiring material of the present invention is characterized in that it contains Ta in an amount of 0.003 at% or more and less than 0.1 at%, with the balance being Al and inevitable impurities, as described above.

In the present invention, the Ta content is 0.003.
It is necessary to be at% or more. 0.003at%
When it is less than EM resistance, EM resistance is insufficient. A preferred lower limit value is 0.01 at%, more preferably 0.02 at%
It is. Although the EM resistance improves as the Ta content increases, if it becomes 0.1 at% or more, the electrical resistivity becomes larger than the allowable upper limit value of 3.5 μΩ · cm, and the intended purpose cannot be achieved. . Therefore, the Ta content is 0.1 at
It must be less than%. The upper limit is 0.1 at%
The closer to, the better, and the more preferred is 0.0
It is 8 at%.

In producing the wiring material of the present invention, various methods (for example, sputtering method) can be applied as in the case of the conventional Al-based alloy material containing Si, Cu, etc., among which sputtering is used. The method is the most recommended method in that nonequilibrium solid solution strengthening by vapor phase quenching can be obtained.

That is, the solid solubility of Ta in Al is 0.036 at% at the maximum, but in the case of a Ta-added Al-based alloy formed by the sputtering method, a higher concentration of Ta is obtained by vapor-phase quenching. Ta is Al even in the added region
It can be solid-solved in. In addition, T is higher than the maximum solid solubility.
Even when a is added, Ta in a solid solution state is stably present in the Al matrix, and Ta precipitation is hardly observed even when heat treatment is performed. And, even after the alloying process usually performed on the Al-based metal wiring (heat treatment at 400 ° C. for about 30 minutes performed in the process after forming the wiring pattern), most of the added Ta remains in a solid solution state. However, it can be an extremely effective means for preventing EM of Al atoms by solid solution strengthening.

As the sputtering target material, it is desirable to use an Al-based alloy produced by a melting / casting method or a powder sintering method (hereinafter referred to as a molten Al alloy target material). That is, since such a molten Al alloy target material is histologically extremely uniform and the sputtering rate and the emission angle are uniform, an Al-based wiring material that is more excellent in terms of EM resistance and the like can be obtained. As a result, it becomes possible to provide a more reliable semiconductor device. Among them, the oxygen content of the target material manufactured by the melting / casting method can be suppressed to 100 ppm or less, so that the electrical resistivity of the Al-based alloy material can be further reduced.

As described above, the wiring material of the present invention has the conventional S
Since it can be produced by a method similar to that of the i-based, Cu-containing, Al-based alloy material, it does not cause a decrease in productivity as in the case of composite wiring or surface alloyed wiring by ion implantation.

Hereinafter, the present invention will be described in detail with reference to examples.
However, the following examples do not limit the present invention,
All modifications and alterations without departing from the spirit of the preceding and following descriptions are included in the technical scope of the present invention.

[0022]

【Example】

Example 1: Measurement of electrical resistivity Using melted Al alloy target materials having different Ta contents, DC magnetron sputtering method was used to form a 5000 Å thick Al- film on a thermally oxidized Si substrate.
A Ta alloy thin film was formed. Next, the thin film was processed into a stripe pattern (electrical resistivity measurement pattern) having a width of 10 μm and a length of 10 mm by performing photolithography and wet etching, and this was used as a test material.

In measuring the electrical resistivity, the sample material was alloyed (vacuum heat treatment at 400 ° C. for 1 hour), and then the electrical resistivity of the Al—Ta alloy thin film was measured. The electrical resistivity was measured at room temperature by the four-point probe method.

The results are shown in FIG. As shown in FIG.
The electric resistivity tends to increase linearly with the increase of the Ta addition amount, but if the concentration is kept below 0.1 at%, the allowable upper limit of the electric resistivity is 3.5 μΩ.
cm or less can be achieved.

Example 2: Evaluation of EM resistance (1) Al-0.1 at% Ta alloy target material as an example of the present invention, and pure Al and Al-0.1 at% S as a comparative example.
c alloy and Al-0.2 at% Cu-1.0 at% S
Using the i alloy target material, an Al-Ta alloy thin film having a film thickness of 5000 angstrom was formed on the thermally oxidized Si substrate by the same sputtering method as in Example 1. Next, the thin film was processed into a EM evaluation pattern having a stripe shape with a width of 2 μm and a length of 1 mm by performing photolithography and dry etching, and this was used as a test material.

In evaluating the EM resistance, after the alloy treatment as in Example 1 was applied to the above-mentioned test material, Isothe
The rmal test method was performed. In addition, the evaluation of the EM resistance in the present example was carried out by applying the current density 2 ×
A current of 10 ⁶ A / cm ² was applied, and the time (breakdown time) until disconnection was measured at a sample temperature of 175 ° C. and the measurement was performed.

FIG. 2 shows the relationship between the failure time of various wiring materials thus obtained and the cumulative failure rate. As is clear from the figure, for all the test materials, the distributions that are almost linear are shown on the vertical axis (cumulative failure rate) on the normal probability logarithmic scale and on the horizontal axis (failure time) on the logarithmic scale. It was found to have a Gaussian distribution. Here, when the failure time at which the cumulative failure rate becomes 50% is defined as the average failure time,
Pure Al, Al-0.1 at% Sc alloy, Al-0.2a
t% Cu-1.0 at% Si alloy, Al-0.1 at%
The failure time of Ta alloy wiring is 4380 and 2870, respectively.
It was 0,176000,841000 seconds, and it can be seen that the Al-0.1 at% Ta alloy wiring of the present invention example has the best EM resistance.

Example 3: Evaluation of EM resistance (2) An EM resistance evaluation pattern was prepared in the same manner as in Example 2 using molten Al-based alloy target materials having different Ta contents. The EM property was evaluated. The result is shown in FIG. As is clear from the figure, the EM resistance of the Al—Ta alloy wiring increases with an increase in the Ta addition amount, and in the Ta addition range of the present invention, the EM resistance of each is the comparative example used in Example 2. (Pure Al, Al-0.1 at% Sc alloy,
Al-0.2at% Cu-1.0at% Si alloy wiring)
It can be seen that the EM resistance is superior to that of.

[0029]

Since the semiconductor wiring material of the present invention is constructed as described above, it is excellent in EM resistance and low in electrical resistivity, so that productivity is not lowered, and moreover, the semiconductor device of recent years has high performance. It is possible to cope with the situation such as narrowing of wiring width due to integration.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the Ta addition amount and electric resistivity in Example 1.

FIG. 2 is a graph showing the relationship between failure time and cumulative failure rate in Example 2.

FIG. 3 is a graph showing the relationship between the amount of Ta added and the mean failure time in Example 3.

Claims (1)

[Claims] 1. Ta of 0.003 at% or more and 0.1 at
%, With the balance being Al and unavoidable impurities, a semiconductor wiring material.