JPH0677299A - Wiring test of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a method for testing wirings of a semiconductor device which preferably evaluates resistivity to electro-migration without receiving influence of Joule heat. CONSTITUTION:Only electro-migration can be evaluated by providing dummy wirings 2, 3 in both sides of a test wiring 1 on a wafer and radiating the Joule heat generated by stress applied to the test wiring 1 through the dummy wirings 2, 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring test method for semiconductor devices.

[0002]

2. Description of the Related Art Conventionally, the life of wiring provided at the wafer stage in the process of manufacturing a semiconductor device has been evaluated by an electromigration test. For this electromigration test, for example, the SWEAT method,
There are BEM method, J-lamp method and the like.

To briefly explain these test methods, first, the SWEAT method is a method of performing an acceleration test by changing the structure of the wiring through which a current flows (for example, Japanese Examined Patent Publication No. 1-24271). 61-70472). The wiring structure that is often used in this test method is a structure in which portions with different wiring widths are provided in the test wiring, and when a high-current-density test current (hereinafter referred to as stress) is applied to the wiring structure, it is extremely Although a large amount of Joule heat is generated, the Joule heat is not generated from the thick wiring portion, so that a temperature gradient is formed on the wiring. When a temperature gradient is generated on the wiring in this way, the electromigration phenomenon is accelerated, and the electromigration resistance test can be performed quickly.

Next, the BEM method is a method of applying a constant high current density and calculating the energy required for cutting the wiring from the time and the current density at which the wiring is broken (for example, JP-A-60-80236). Bulletins and References JM Tower, Solid State Tec
hnol (27 (10), 197 (1984))) and is often used to compare process advantages. The J-Ramp method is a method of increasing the current density stepwise (for example,
JP-A-2-292839, Proceedings of the Japan Society of Applied Physics (1991, S
29-W-1)). This method is similar to the BEM method described above, in that the energy required to break the wiring is calculated from the time when the wiring is broken.

[0005]

However, all of the above-mentioned conventional methods can quickly evaluate the electromigration resistance, but since high current density stress is applied, Joule heat and electromigration can be prevented. Since both phenomena were seen, it was unsuitable to evaluate only the electromigration phenomenon.

By the way, in consideration of the Joule heat from such wiring, a method of cooling a test sample with water, air, liquid nitrogen or the like has been devised. The test apparatus used for this is very large scale. However, there are many disadvantages in terms of cost. The present invention has been made in order to solve the above-mentioned problems of the conventional technique, and reduces Joule heat generated in a wafer level test, and is a very simple device that only causes an electromigration phenomenon of wiring. It is an object of the present invention to provide a wiring test method for a semiconductor device, which can be evaluated in 1.

[0007]

SUMMARY OF THE INVENTION The present invention provides a method of performing an electromigration test of a wiring applied at a wafer stage in a semiconductor device manufacturing process, wherein dummy wirings are provided on both sides of the wiring to be tested, The semiconductor device wiring test method is characterized in that the Joule heat generated by the stress applied to the wiring to be tested is radiated through the dummy wiring.

[0008]

[Operation] First, the wiring structure used in the present invention will be described. As shown in FIG. 1, a space b is provided on both sides of a wiring 1 to be tested (hereinafter referred to as test wiring) having a line width a.
The dummy wirings 2 and 3 having the line width c are provided. Therefore, when a high current density stress is applied to the test wiring 1 by the electromigration test, a very large Joule heat generated in the test wiring 1 can be radiated to the silicon substrate having a large thermal conductivity through the dummy wirings 2 and 3. Therefore, it is possible to evaluate only the electromigration phenomenon in the test wiring 1.

[0009]

EXAMPLE An electromigration test was conducted using the wiring structure of the present invention. Test wiring used for the test 1
Is made of Al alloy and its line width a is 1.2 μm and is 6000 μm.
Dummy wirings 2 and 3 made of Al alloy are formed on the wafer at a distance b of 1.2 μm on both sides of the test wiring 1 with a line width c using photolithography. Patterned to 1.2 μm. On the other hand, for comparison, as shown in FIG. 2, a conventional wiring structure without dummy wiring was prepared by applying a test wiring 4 having a line width d of 1.2 μm, an interval e of 10 μm and the same length of 6000 μm. The thickness of both films was 1 μm.

Both the test wiring 1 and the test wiring 4 having these wiring structures have an environmental temperature of 170 ° C. and a current density of 4 × 10 ^6.
A stress of A / cm ² was applied and their temperature rise was examined. No current is passed through the dummy wirings 2 and 3. The Joule heat of each wiring at this time was calculated from the resistance value. As a result, the temperature rise due to Joule heat of the conventional wiring structure without dummy wiring was 80.5 ° C, while the Joule heat of the wiring structure of the present invention with dummy wiring was 20.3 ° C, which is about 1 / It was about 4.

Usually, the Al alloy has a secondary recrystallization temperature around 200 ° C., and there is a possibility that the physical properties will change. For this reason, when conducting an electromigration test (reliability test) in the state of being assembled in a package, generally, a test at 201 ° C or higher is not performed. This is
This means that it is necessary to keep the wiring temperature below 200 ° C, which is the result of this experiment.
It can be seen that 170 + 20.3) sufficiently satisfies the above conditions of 200 ° C or lower.

In the above experiment, the environmental temperature is 170 ° C., but if the environmental temperature is lowered to about room temperature, the current density can be further increased and the electromigration is performed. It is fully expected that only the phenomenon can be evaluated quickly. Further, in the above embodiment, the structure of the test wiring 1 is 1.2 μm with a line width of 1.2 μm.
The description has been made assuming that the space between the dummy wirings and the dummy wirings 2 and 3 have a line width of 1.2 μm.
For example, as shown in FIG. 3, there is no problem even if the Al alloy-based metals 5 and 6 serving as dummies are left as radiator plates on both sides of the test wiring 1A. In this case, the heat dissipation effect becomes very large, and in a high current density test,
More Joule heat generated from the wiring can be dissipated.

[0013]

As described above, according to the present invention, the dummy wiring is provided on both sides of the test wiring to be subjected to the electromigration test, so that the joule generated when a high current density stress is applied to the test wiring. Since the generated heat can be dissipated to the dummy wiring that does not pass the current, it is possible to evaluate only the electromigration phenomenon.

This solves the problem that the activation energy obtained by the conventional electromigration test shows a big difference from the activation energy obtained by the wiring reliability acceleration test performed in the state of being assembled in the package. It is fully predictable that it is possible. Further, since the heat dissipation pattern can also be produced by a commonly used technique such as photography and dry etching by simply depositing a metal film, it can be performed by an existing electromigration test method at the wafer stage, It is also effective in terms of cost.

[Brief description of drawings]

FIG. 1 is a plan view schematically showing an example of a wiring structure used in the present invention.

FIG. 2 is a plan view schematically showing an example of a conventional wiring structure.

FIG. 3 is a plan view schematically showing another example of the wiring structure used in the present invention.

[Explanation of symbols]

 1 Test wiring 2 Dummy wiring 3 Dummy wiring 4 Test wiring 5 Metal 6 Metal

Claims (1)

[Claims] 1. A method for conducting an electromigration test of a wiring applied at a wafer stage in a semiconductor device manufacturing process, wherein dummy wirings are provided on both sides of the wiring to be tested, and stress applied to the wiring to be tested. A method for testing a wiring of a semiconductor device, characterized in that Joule heat generated by the method is radiated through the dummy wiring.