JPS5814069A - Acceleration test of electro-migration - Google Patents

Abstract

PURPOSE:To reduce the testing time and to enable more precise evaluation of wiring film under the condition close to actual use by supplying a sample metal wiring film formed on a substrate and holding that state. CONSTITUTION:A test sample with the wiring of multi-level crossing structure consists of a cilicon substrate 1, insulator films 2 and 3 of phosphor glass or cilicon nitrate formed on the substrate and an aluminum film 5 insulated from a test aluminum film 4 and crossing said film 4 at a different level. The acceleration test of this sample is carried out by supplying the aluminum film 4 with a certain current, supplying the aluminum film 5 with a certain voltage or current and by holding this state.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for accelerating electromigration testing of a metal wiring film formed on a semiconductor substrate. 2. Description of the Related Art Semiconductor integrated circuits have recently become highly integrated and densely packed, and circuit pattern dimensions are becoming smaller. With such miniaturization of the pattern size a, the structure, arrangement, processing process, etc. are undergoing major changes in relation to the electrical characteristics of circuit components and the like. Various problems have also arisen with the miniaturization of the dimensions of metal wiring films that electrically interconnect the constituent elements. In particular, an increase in wiring resistance or breakage due to so-called electromigration of a metal wiring film is one of the major problems that has come into focus as dimensions become finer. By the way, as we move towards higher integration, so-called multi-layer metal wiring films are being developed.
lk! Wire J117i structure is also required, and gold kJ' including multilayer wiring structure is also required! It is necessary to stabilize the electromigration phenomenon of wiring films. There is an accelerated electromigration test as a test to prevent such changes.

In the conventional electromicrage acceleration test,
Target gold 1ryl lli at high temperature: line tl, 11
A method is adopted in which a current is passed only through 4. In tests using such wiring configuration samples, not only does it take a relatively long time to reach disconnection, but it also takes a relatively long time to reach a disconnection. There were drawbacks such as significant differences.Unexpected [Month was not intended to eliminate the above drawbacks] Also, it was possible to shorten the test time of the electromicrometer iJ for wiring membranes and accelerate it to correspond to actual usage conditions. Test sample 1'l or If, J2, which has a wiring configuration that is not tested, is an innovation that captures a test method using a wiring part that actually has a specific relationship in a manufactured semiconductor device. It is.

The feature of the accelerated testing method for the Elect-17 migration silicon of the present invention is that a current is passed through a first metal wiring film to be tested formed on a substrate, and a metal wiring film placed close to the first metal wiring film is This state is maintained by applying a voltage to the second metal wiring film to cause a current to flow therethrough. By the way, when conducting such accelerated tests,
As described above, it is necessary to prepare a test sample having a wiring structure in which first and second metal wiring films are disposed close to each other on a substrate. For this purpose, it is sufficient to select either to manufacture a test sample in which such a relationship is established, or to use a semiconductor device in which such a relationship is established in the interconnection portion.

FIG. 1 is a diagram showing a test sample having a three-dimensional intersection wiring structure manufactured as an example of a test sample used in the present invention. In the figure, 1 is a silicon substrate, 2 and 3 are phosphor glass films or An insulating film such as a silicon nitride film, 4 is an aluminum (Aβ) film to be tested, and 5 is an A4 film which is insulated from the Aβ film 4 by the insulating film 3 and also three-dimensionally intersects with the Ajllll ring 4. .

In an accelerated test of the electromigration silicon of the present invention using a test specimen 1"l having the wiring 44/i structure as shown above, a predetermined constant current is applied to A l ll + J a, and This is done under the conditions of applying a predetermined voltage F or flowing a predetermined current to maintain this state.

FIG. 2 is a schematic diagram for qualitatively explaining the electromigration accelerated test method of the present invention. For example, a voltage is applied to A l l', '45, which is the second metal interconnection film disposed close to A (9).
) is affected by electric field effects due to the main part. This causes non-uniform movement of the A5 ion flow, such as uneven movement of the A5 ion flow within the body 4 or high ion density at specific locations. Two things about this.
Compared to the case where the ion flow is uniform, the time required to reach disconnection is shorter. In addition, the 6th line in the figure, the line of force that forms the stone at ApHL+ 4, is twisted, and the arrow 7 fqJ in Figure 2 (b):
A (l indicates the flux of 14 ions in 4 of If,
The flux of A/ions in the portion 8 facing the A/membrane 5 is affected.

A qualitative formula for the disconnection life considering this mechanism is shown in the following formula.

Here MTBF: mean time between
nfailureJ: Current density (A/lU) ■ = Applied voltage to the interconnection film α: Distance between the interconnection film and the interconnection film ε: Dielectric constant of the intermediate material φ: Activation energy Figure 3 is as follows. FIG. 2 is a diagram showing the results of an experiment comparing the test time between the electromigration accelerated test method of the present invention and the conventional accelerated test method, which have been discussed in two ways. In this comparative experiment, a sample in the shape of a three-dimensional intersection shown in FIG. 1 was sealed and molded with epoxy resin and used as a test sample.

By the way, the manufacturing conditions such as the dimensions of the test sample are as follows.

AjllIri 4 (for exam) Sutou: Pure Aluminum Uno 1.11 Vri I? :2μ7n Membrane width: 15μm human e membrane 6 paulownia: 81 1-2 layers j71% IA 1. Aluminum film thickness: o, 8 μ? +1 IN 1lV1i;
15 p, n insulating film 3 Phosphorous glass (PSG) film with a film thickness of 1 μm. Accelerated test for comparison Q: 1. 20 test samples were placed in a high temperature of 1600 C, 1 q, of which 10 were The current density of A4+1 momme 4 was set to 3.6 x 105 A/-, and the electric current Ll: was not applied to the kl film 5 (conventional method), and the current density of A7!11944 was set to the same value for the remaining 10 films. At the same time, a DC voltage of 30 V was applied to the A4 film 6 (method of the present invention), and the time required for failure (disconnection) to occur in the pattern Fl was measured.

As is clear from FIG. 3, in the method of the present invention in which a voltage is applied to the Aj film 6, the time required for the test sample to fail is significantly reduced compared to the conventional method. For example, when a failure occurs during testing the number of rods (failure 60%), the test time is:
The method of the present invention takes about 250 hours, and the conventional method takes about 400 hours, which is a time reduction of about 150 hours.

As is clear from the above explanation, the accelerated test method for electromicrocation of the present invention can be performed in a condition P that is very close to that in actual use, and can significantly shorten the test time. In addition to the effect of dramatically improving work efficiency, λ- has the effect of greatly increasing the accuracy of wiring film evaluation.

In the above explanation, the test sample shown in FIG. 1 was shown, but the test sample is not limited to this example. For example, as shown in FIG. 4, the Al film 6 is A71! 5, the Al layers 4 and 5 are arranged in parallel on the insulating film 2, as shown in FIG. It is also possible to use the configuration shown in FIG. 4 with the A7J films 4 and 5 arranged in reverse order. Alternatively, two insulating films, which correspond to surface protective films, may be formed on these test samples as the second most layer.

[Brief explanation of drawings]

Figure 1, Figure 4 and Figure 6 are schematic diagrams for qualitatively explaining the electric test method of IJI, and Figure 3 is a schematic diagram for confirming the effect of the present invention. FIG. 2 is a diagram showing the results of a soft experiment. 1... Silicon substrate, 2, 3... Insulating film, 4゜6... A/j film, 6... Lines of electric force, 7... ...A6 ion flow rate. Name of agent: Patent attorney Masao Nakao and 1 other person No. 1
figure

Claims (5)

[Claims] (1) A current is passed through the first metal wiring film of a test sample in which a second metal wiring film is placed close to the first metal wiring film to be tested formed on the substrate, and the second metal wiring film is passed through the second metal wiring film. An accelerated electromigration test method characterized by applying a voltage or flowing a current and maintaining this state. (2) The electromigration accelerated testing method according to claim 1, wherein an insulating film is provided between the first metal wiring film and the second metal wiring film of the test sample. (3) The electromigration accelerated testing method according to claim 1, wherein the first metal wiring film and the second metal wiring film of the test sample intersect three-dimensionally. (4) The electromigration accelerated test method according to claim 1, wherein the first metal wiring film and the second metal wiring film of the test sample extend in parallel with an insulating film sandwiched therebetween. (5) The electromigration accelerated testing method according to claim 1, characterized in that the first metal wiring film and the second metal wiring film of the test sample are arranged side by side on the same plane.