JPH07130816A - Method and apparatus for evaluating electromigration and body under test - Google Patents

Abstract

PURPOSE:To prevent the deterioration of the reliability of evaluation caused by Joule heat of an aluminum wiring itself, which is the object to be measured, by maintaining the temperature of a conductor under evaluation constant, and suppressing the deterioration of workability and the change in circuit patterns and production process. CONSTITUTION:A conductor under evaluation 3 comprising an aluminum wiring, a monitor 4 and a heater 5 are formed at the neighboring positions one another in a test element group 2. A current is made to flow through the conductor under evaluation 3 at the specified current density. The electromigration life of the conductor under evaluation 3 is evaluated. Especially, the temperature change of the conductor under evaluation 3 is measured with the monitor 4 during the current conduction into the conductor under evaluation 3. The temperature of the conductor under evaluation 3 is kept constant with the heater 5 based on the measured temperature data. Only the electromigration phenomenon is made to occur in the conductor under evaluation 3 in this way. The current-density coefficient and the activated energy are obtained, and the evaluation can be performed accurately in a short time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromigration evaluation technique, and more specifically, a current is passed through a conductor to be evaluated having a predetermined current density to evaluate the electromigration life of the conductor to be evaluated. The present invention relates to an electromigration evaluation technique, for example, a technique effectively used to evaluate the electromigration life of aluminum (Al) wiring or alloy electrode wiring in a semiconductor device.

[0002]

2. Description of the Related Art Generally, when developing a semiconductor device,
The design is executed by estimating the service life and the failure rate at the design stage. Aluminum wiring is widely used in semiconductor devices, and the service life and failure rate of the aluminum wiring greatly affect the service life and failure rate of the semiconductor device. Here, the estimation of the life of the aluminum wiring will be described.

The life of aluminum wiring is J. K. Bla
The equation of ck can be expressed by equation (1). MTF = A × J ⁻ⁿ × exp (Ea / k × T) (1) where MTF is mean failure time, A and n are constants, J is current density, Ea is activation energy, and k is Boltzmann's constant, T is absolute temperature.

Practically, an aluminum wiring test pattern is used to evaluate the temperature and current density to find the constants A and n, and the values are reflected in the design of the aluminum wiring of the semiconductor device product. Will be. Then, the manufactured semiconductor device will be used as one that operates at the estimated failure rate until the useful life estimated by the design.

However, if the semiconductor device is unexpectedly or abnormally manufactured in the manufacturing stage, it may fail at a high rate before the estimated useful life is reached. When such a failure occurs in the market,
The target product with the abnormal manufacturing method will be investigated and replaced with a normal product. Then, not only enormous cost is required, but also the reliability of the semiconductor device product may be deteriorated.

It is difficult to detect a reliability-reduced product generated in this manufacturing stage in the finished product stage. for that reason,
Shipment of reliability-reduced products that occur during the manufacturing stage by responding with a process control method that does not carry out unexpected or abnormal manufacturing, does not manufacture abnormal products, and if they do not flow to the next process Is prevented.

In today's semiconductor device manufacturing plant,
PQC (Process Quality Controller)
ol) method and SPC (Static Proc)
Process control such as ess Control) method is generally performed. The SPC method is a method of statistically calculating the process capability of each manufacturing process and managing the manufacturing process with a capability index.
By improving this process capability, a high quality product will be manufactured. The items of process control will be decided according to the target failure mechanism. In manufacturing a semiconductor device, the method for evaluating electromigration of aluminum wiring is an important item for process control.

[0008] Recently, a method of controlling a process by forming a test pattern in a semiconductor wafer (hereinafter, referred to as a wafer) and performing an electromigration evaluation method using this test pattern has also been implemented.
SWEAT (Standard Waferlevel)
Electromigration Acceler
ation Test) is a process control method using a pattern method. A test pattern is formed by the diffusion resistance and aluminum wiring. Electromigration is evaluated by passing a current through the aluminum wiring.

As a method for evaluating electromigration of aluminum wiring, a BEM (Breakdown Ene) for evaluating a total amount of energy until a breakdown is applied by applying a lamp current to the aluminum wiring at room temperature.
rgy of Metal) method or Jram of the same method
The p method has been developed.

These evaluation methods have been centered on relative evaluation methods for evaluating whether the electromigration life level of wiring is good or bad. However, methods that improve these methods and can evaluate temperature acceleration are also being developed.

As described above, in the manufacturing process of a semiconductor device, as a means for testing the reliability of the aluminum wiring of the integrated circuit built in the semiconductor device, the electromigration life of the aluminum wiring to be tested is determined. Evaluation methods are widely practiced. The width of the aluminum wiring in the semiconductor device has been reduced in accordance with the higher integration and miniaturization of the semiconductor device, and the current density of the aluminum wiring tends to increase. Therefore, the electromigration life of aluminum wiring has become an important item for reliability evaluation, failure analysis, and research and development, as compared with the past.

By the way, the electromigration life has a temperature acceleration property, and its activation energy is Ea.
= 0.5 to 1.2 eV is known.
Therefore, in the conventional method of evaluating the electromigration life, the life until the electromigration failure (disconnection failure) occurs by energizing the aluminum wiring of the semiconductor device at a constant current density in a constant-temperature constant temperature bath. I am evaluating. In that case, the high temperature in the constant temperature bath is kept constant, but the temperature of the aluminum wiring to be evaluated is unknown.

In particular, in the case of the accelerated evaluation method of the electromigration life, the current density (about 1
Current larger than 0 ⁵ A / cm ² (10 ⁶ A / cm ²
Since the electromigration life is evaluated by flowing the above), thermal runaway occurs due to Joule heat generation of the aluminum wiring, and an accurate test cannot be secured.

Therefore, conventionally, the following electromigration evaluation method has been proposed.

Japanese Unexamined Patent Publication (Kokai) No. 2-90646 proposes a technique of providing a temperature measuring element near a metal wiring of a semiconductor device as a device under test and measuring the temperature of an aluminum wiring to be evaluated. There is.

Japanese Patent Laid-Open No. 64-86077 discloses that
It has an electrode for directly applying a current to the aluminum wiring to be evaluated, and further, a heater for heating this wiring,
A jig has been proposed that incorporates a temperature sensor (thermocouple) that adjusts the electric power applied to the heater in order to keep the temperature of the wiring constant.

Japanese Patent Laid-Open No. 61-70472 discloses that
After an insulating film is provided on the polycrystalline silicon wiring, an aluminum wiring to be evaluated is provided so as to intersect this polycrystalline silicon wiring, and a heating current is applied to the polycrystalline silicon wiring to generate Joule heat of the polycrystalline silicon wiring. Has proposed a method of accelerating the electromigration life by raising the temperature of an aluminum wiring portion which is an evaluation target and intersects with it.

[0018]

However, the above conventional techniques have the following problems to be solved.

In the technique proposed in Japanese Patent Application Laid-Open No. 2-90646, a method of using the measured temperature of the aluminum wiring to keep the temperature of the aluminum wiring to be evaluated at a predetermined temperature has been studied. Absent.

In the technique proposed in Japanese Patent Laid-Open No. 64-86077, it is necessary to bring the jig into direct contact with the desired aluminum wiring to be evaluated, and therefore the workability of the evaluation method is low.

In the technique proposed in Japanese Patent Application Laid-Open No. 61-70472, a polycrystalline silicon wiring for heating needs to be laid in advance just under the aluminum wiring to be evaluated. It is necessary to change the production process, etc. Further, a method for keeping the temperature of the wiring at a predetermined temperature has not been studied.

A first object of the present invention is to prevent deterioration of reliability of evaluation due to Joule heat generation of aluminum wiring itself which is an object of evaluation while suppressing deterioration of workability and change of circuit pattern and production process. An object of the present invention is to provide an electromigration evaluation method and device capable of performing the above.

By the way, the electromigration life of the aluminum wiring is as shown in the above equation (1).
Affected by current density and temperature. Therefore, if the current density acceleration coefficient n and the activation energy Ea of the aluminum wiring which is the conductor to be evaluated can be obtained in a short time using the test pattern, the layout design of the semiconductor device product, the life prediction of the finished product, the process control, etc. Can be used for. This also applies to conductors made of other metals.

A second object of the present invention is to provide an electromigration evaluation technique capable of performing electromigration evaluation under conditions of high current density and high temperature, using a test pattern as simple as possible. Especially.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0026]

The typical ones of the inventions disclosed in the present application will be outlined below.

That is, in the electromigration evaluation method in which an electric current is applied to a conductor to be evaluated made of metal with a predetermined current density to evaluate the electromigration life of the conductor to be evaluated, a current is applied to the conductor to be evaluated. The temperature change of the conductor to be evaluated is measured while the temperature of the conductor to be evaluated is controlled by energization to keep the temperature of the conductor to be evaluated constant based on the temperature measurement data. Characterize.

[0028]

According to the above-mentioned means, the temperature change of the conductor to be evaluated whose electromigration life is to be evaluated is measured during the test, and the temperature of the conductor to be evaluated is maintained at the predetermined test temperature based on the measured data. It will be. In other words, the conductor under evaluation is maintained at a constant temperature,
Since the evaluation work of the electromigration life is executed, the evaluation of the electromigration life is accurately executed. As a result, the current density can be set to a large value, and the electromigration life can be evaluated in a short time.

Then, for example, when an abnormality is found in the wiring material or the wafer manufacturing process, the electromigration life of the product can be determined in a short time. Therefore, when the abnormal wafer is actually used, It can be clearly determined whether it will be a problem. As a result, abnormal measures can be taken promptly, and the productivity as a whole can be improved.

[0030]

EXAMPLE FIG. 1 is a schematic view showing an electromigration evaluation apparatus which is an example of the present invention. 2A and 2B show a test object that is an embodiment of the present invention, FIG. 2A is a plan view showing a semiconductor wafer, and FIG. 2B is an enlarged partial plan view of a TEG thereof.

In this embodiment, the electromigration evaluation apparatus according to the present invention is an aluminum wiring formed in a test element group (TEG) of a semiconductor wafer (hereinafter referred to as a wafer) in a semiconductor device manufacturing process. Is configured to be performed on-line or off-line.

In the present embodiment, a test element group (TEG) 2 is formed in a suitable number of locations on a wafer 1 as a subject, as shown in FIG. Aluminum wiring (hereinafter referred to as the conductor to be evaluated) 3 as the conductor to be evaluated is provided in the TEG 2.
A temperature measurement wiring (hereinafter referred to as a monitor) 4 and a heating wiring (hereinafter referred to as a heater) 5 are formed adjacent to each other. The conductor 3 to be evaluated is formed so as to be equal to the aluminum wiring to be evaluated built in the wafer 1. The monitor 4 is made of a material having a good positive temperature characteristic, and is set so that the temperature change of the conductor 3 to be evaluated can be accurately measured. The heater 5 is made of a material having a good resistance heating characteristic, and is set so that the temperature of the conductor 3 to be evaluated can be precisely controlled.
The monitor 4 and the heater 5 can be formed by aluminum wiring equivalent to that of the conductor 3 to be evaluated. In this case, the evaluated conductor 3, the monitor 4, and the heater 5 can be formed at the same time. Further, the evaluated conductor 3, the monitor 4, and the heater 5 are provided with pads 6 on both ends thereof, which are brought into contact with contacts described later.

In this embodiment, the electromigration evaluation apparatus 10 is equipped with a thermostatic chamber 11 capable of maintaining a constant temperature inside the chamber, and the thermostatic chamber 11 has a loading / unloading port 12 and a wafer as a test object. It is opened so that 1 can be put in and taken out. A first contactor 14 is arranged in the constant temperature bath 11, and the first contactor 14 is configured so as to be able to contact the conductor 3 to be evaluated on the wafer 1. An electromigration measuring device 13 having a constant current source is connected to the first contactor 14, and the constant current source of the measuring device 13 has a large current density several orders of magnitude higher than the current density normally used. It is configured so that it can be energized.

Further, a temperature medium supply device 15 for supplying a temperature medium to the inside of the constant temperature bath 11 is fluidly connected to the constant temperature bath 11, and the supply device 15 has a high temperature for blowing out high temperature air or nitrogen gas. A tank 16 and a low temperature tank 17 that blows out low-temperature air or liquid nitrogen are provided. The high temperature tank 16 and the low temperature tank 17 are provided so as to communicate with each other, and an air duct 18 is connected to the communication portion and extends to the storage position of the wafer 1 in the constant temperature tank 11. Then, the gas blown into the constant temperature chamber 11 through the air duct 18 is controlled by the damper 19 installed in the communication part so that the flow rates of the high temperature gas on the high temperature chamber 16 side and the low temperature gas on the low temperature chamber 17 side are controlled. It is configured. A wafer stage 25 on which a wafer is placed is installed in the constant temperature bath 11.
A heater (not shown) is built in the wafer stage 25, and the temperature of the heater is controlled by a temperature controller 26. Then, normally, the temperature control of the wafer stage 25 enables the evaluation described later to be executed.

A second contact 20 is arranged in the constant temperature bath 11 so that the second contact 20 can contact the monitor 4 on the wafer 1. Second contactor 2
A temperature measuring device 21 is connected to 0, and the temperature measuring device 21 measures the resistance value of the monitor 4 to measure the ambient temperature of the monitor 4, that is, the temperature of the conductor 3 to be evaluated. ing. A controller 22 constructed from a computer or the like is connected to the temperature measuring device 21.

Furthermore, the third contact 23 is provided in the constant temperature bath 11.
Is provided, and the third contact 23 is configured to be able to contact the heater 5 on the wafer 1. A temperature controller 24 is connected to the third contact 23, and the temperature controller 24 controls the power supplied to the heater 5 to control the ambient temperature of the heater 5, that is, the temperature of the conductor 3 to be evaluated. It is designed to be controlled. The temperature control device 24 is connected to the output end of the controller 22. The controller 22 is configured to control the temperature of the conductor 3 to be evaluated to a predetermined constant value (target value) by controlling the temperature control device 24 based on the temperature measurement data from the temperature measurement device 21. ing.

Next, the operation of the electromigration evaluation apparatus having the above-described structure will be described to explain an electromigration evaluation method which is an embodiment of the present invention.

When the wafer 1 as a test object constructed as described above is placed on the wafer stage 25 in the constant temperature bath 11, the temperature of the wafer stage 25 is kept constant at a predetermined temperature. After that, the temperature inside the bath may be kept constant by using the temperature medium supply device. Then, the TE of the wafer 1
Electric power is supplied to the heater 5 formed in G2 via the third contact 23, and the conductor 5 to be evaluated wired near the heater 5 by the heater 5 has a predetermined temperature (target value).
The temperature is maintained at a constant temperature (evaluation temperature) by feedback control described later.

At the same time, the conductor 3 to be evaluated on the wafer 1
A test current is supplied from the constant current source of the electromigration measuring device 13 with a large current density. The electromigration measuring device 13 passes a test current having a predetermined large current density to the conductor 3 to be evaluated on the wafer 1, and the conductor 3 to be evaluated is disconnected or the resistance value becomes a predetermined value (for example, 50% of the initial value). Measure the time to reach. The electromigration life is evaluated based on the time from the start of energization of the conductor 3 to be evaluated to the break or a predetermined value.

At this time, the temperature change of the conductor 3 to be evaluated is measured by the monitor 4 arranged near the conductor 3 to be evaluated. For example, when the temperature of the conductor 3 to be evaluated rises, the temperature of the monitor 4 arranged in the vicinity thereof also rises.
The resistance value of the monitor 4 increases. The temperature measuring device 21 uses the monitor 4, based on the change in the resistance value of the monitor 4,
That is, the present actual temperature of the conductor 3 to be evaluated is obtained and the result is transmitted to the controller 22.

The controller 22 calculates the difference between the present actual temperature and the target temperature set in the temperature control device 24, obtains a control value to fill this difference, and controls the temperature control device 24. The feedback control is executed so as to keep the temperature of the conductor 3 to be evaluated constant. For example, when the temperature is higher than the predetermined test temperature (for example, 300 ° C.), the power of the temperature control device 24 is reduced. On the contrary, when the temperature is lower than the predetermined test temperature, the temperature control device 2
4 power up. By the above feedback control, the temperature of the conductor 3 to be evaluated on the wafer 1 is maintained constant (for example, 300 ° C.). Therefore, in the electromigration evaluation method described above,
The conductor 3 to be evaluated is always kept constant.

In carrying out the above electromigration evaluation method, the temperature characteristics of the conductor 3, the monitor 4, and the heater 5 to be evaluated can be obtained by the following equation. Evaluated conductor: R _E = α _E + β _E × T (2) Monitor: R _M = α _M + β _M × T (3) Heater: R _H = α _H + β _H × T ... (4) Here, R _E , R _M , and R _H are resistance values, and α _E ,
α _M and α _H are constants (initial values), β _E , β _M and β _H are temperature coefficients, and T is temperature. Then, the constant of each wiring (α _E ,
α _M , α _H ) and temperature coefficient (β _E , β _M , β _H ). If known, known values can be used.

The conditions for evaluating electromigration are set by the following equation. Current density: J = I _E / W _E × t _E (5) where I _E is the value of current flowing in the conductor 3 to be evaluated, W _E is the line width of the conductor 3 to be evaluated, and t _E is the target to be evaluated. The thickness of the conductor 3. Evaluation _{Temperature: T E = Ta + θja ×} I E 2 × R E + θj EH × I H 2 × R H + θj ME × I M 2 × R M ··· (6) where, θja, θj _EH, θj _ME thermal Resistance value, I _H
Is the value of the current passed through the heater, I _M is the value of the current passed through the monitor, and Ta is the temperature in the constant temperature bath.

In the above expression (6), Ta (in this embodiment, it is kept constant by the temperature medium supply device) and θj _EH × I _H ² × _RH are controlled to evaluate. While the temperature T _E is maintained constant, the electromigration evaluation method described above is performed.
Incidentally, θj _ME × I _M ² × R _M can be ignored because the power consumption and current of the monitor 4 are almost zero. Then, the time point when the resistance value R _E of the evaluated conductor 3 reaches a predetermined value (for example, 50% or more of the initial value) is determined to be a failure. That is, the failure is determined by the following formula. R _E '≧ R _E + γR _E (7) Here, R _E ' is the resistance value of the conductor to be evaluated that is determined to be a failure, R _E is the initial resistance value of the conductor to be evaluated, and γ is a failure determination coefficient. is there.

According to the above-mentioned embodiment, the following effects can be obtained. (1) By maintaining the temperature of the conductor to be evaluated constant, it is possible to prevent occurrence of so-called runaway such as disconnection or burnout due to resistance heat generation due to energization of the conductor to be evaluated. Only the electromigration phenomenon can be caused, and as a result, the current density coefficient n and the activation energy Ea can be reduced in a short time, and
It can be accurately determined, and the electromigration lifetime can be accurately evaluated in a short time.

(2) Since the current density can be set large by preventing runaway due to self-heating of the conductor to be evaluated, the time required for electromigration evaluation can be further shortened.

(3) A conductor to be evaluated is formed on the wafer,
By performing the electromigration evaluation method on the conductor to be evaluated, the electromigration evaluation can be performed on the semiconductor device (product) built into the wafer as the test object, so that the process control of the wafer is executed. At the same time, it is possible to ensure the lot guarantee of the wafer and thus the quality guarantee of the semiconductor device.

(4) For example, in the case of being used for process control of a wafer, when a rejected evaluation or a low evaluation is given to a conductor to be evaluated, the process is performed on the lot of the wafer as the test object. Since management and other countermeasures against abnormalities can be taken promptly, it is possible to prevent deterioration of the quality of the semiconductor device as a product. In addition, since the wafer that has been evaluated as rejected can be stopped from being put into the post-process, it is possible to prevent the shipment of the semiconductor device having a short electromigration life and low reliability to the market. .

(5) By disposing a monitor and a heater in the vicinity of the conductor to be evaluated, it is possible to accurately monitor the temperature change of the conductor to be evaluated, and
Since the temperature of the conductor to be evaluated can be feedback-controlled constantly by the heating operation of the heater based on the measurement result, the electromigration evaluation can be performed accurately and the time required for the evaluation can be further shortened. You can

Although the invention made by the present inventor has been specifically described based on the embodiments, the invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say.

For example, the conductor to be evaluated, the monitor and the heater may be wired as shown in FIGS. 3 (a) and 3 (b).
In FIG. 3A, the conductor 3A to be evaluated, the monitor 4A, and the heater 5A are formed to meander in a concave shape so that the entire length thereof becomes long. As the total length of these components becomes longer, the temperature control range becomes wider, so that the evaluation accuracy can be further improved. In FIG. 3B, the heater 5B is formed in a zigzag shape in a lower layer or an upper layer of the conductor 3 to be evaluated and the monitor 4 which are linearly wired. When the heater 5B becomes long, the heating efficiency can be improved.

As shown in FIG. 4, two wirings may be formed on the wafer, one of which may be used as a conductor to be evaluated and a monitor, and the other of which may be used as a heater. . Also, using one as the conductor to be evaluated,
The other may be used for both the monitor and the heater. When two wirings are used, the conductor to be evaluated and the monitor are the same wiring so that the heater has a larger resistance value and cross-sectional area than the conductor to be evaluated so that the controllable temperature range can be widened. It is desirable to configure. In FIG. 4A, two wirings are formed in a straight line, the first wiring 3C is used as a conductor to be evaluated and a monitor, and the second wiring 5C is used as a heater. . In FIG. 4B, the two wirings are formed by meandering in a concave shape, and the first wiring 3D is formed.
Is also used as the conductor to be evaluated and the monitor, and the second wiring 5
D is used for the heater. Figure 4
In (c), the first wiring 3E is formed in a linear shape and is also used as a conductor to be evaluated and a monitor, and the second wiring 5E is meandered in a zigzag shape in a lower layer or an upper layer of the first wiring 3E. Formed and ready to be used for heaters. In each of the cases (a), (b) and (c), the first wiring is used as the conductor to be evaluated, and the second wiring is used as both a monitor and a heater. Good.

Incidentally, the temperature characteristic in the case of two wirings can be obtained by the following equation. Evaluated conductor: R _E = α _E + β _E × T (8) Monitor: R _M = α _M + β _M × T or heater: R _H = α _H + β _H × T (9) The evaluation temperature, which is a condition for electromigration evaluation, is set by the following formula. Evaluation _{Temperature: T E = Ta + θja ×} I E 2 × R E + θj ME × I M 2 × R M or evaluation _{temperature: T E = Ta + θja ×} I E 2 × R E + θj EH × I H 2 × R H ·· · (10) where j _E > j _M or j _E > j _H (11)

As shown in FIG. 5, one wiring may be formed on the wafer, and the wiring may be used for the conductor to be evaluated, the monitor and the heater. In FIG. 5A, one wiring 3F is formed in a linear shape.
Is also used for the conductor to be evaluated, monitor and heater. In FIG. 5B, one wiring 3
G is formed by meandering, and this wiring 3G is a conductor to be evaluated,
It is designed to be used as both a monitor and a heater. FIG. 5C shows a case where the wiring 3H actually formed inside the wafer 1 is used for the conductor to be evaluated, the monitor and the heater. Contact 14 is attached to this wiring 3H.
When contacting the wiring 3H, the contactor 14 is inserted into the passivation film 7 deposited on the surface of the wafer 1.
A hole 8 for making contact with is opened.

When the number of wirings is one, one wiring serves three roles. In this case, the evaluation temperature is determined only by self-heating, so the evaluation current density is slightly changed in order to control the temperature constant.

Incidentally, the temperature characteristic when there is one wiring can be obtained by the following equation. Evaluated conductor: R _E = α _E + β _E × T (12) That is, monitor: R _M = α _M + β _M × T The evaluation temperature, which is the condition for electromigration evaluation, is set by the following formula. . Evaluation temperature: T _E = Ta + θja × (I _E ± aI _E ) ² × R _E (13) Here, a is a range for controlling the evaluation current (for example, 10%).
By increasing or decreasing the control range a, the temperature of one wiring as the conductor to be evaluated is maintained constant.

As described above, it is possible to evaluate from three wirings to one wiring. However, as the number of wirings increases, the electromigration evaluation can be executed under various evaluation conditions. Further, if there are three or more adjacent wirings, they can be connected in series or in parallel outside and used.

The conductor to be evaluated, the monitor and the heater are T
Not limited to the EG, it may be directly formed in the pellet portion 2A of the wafer 1 as shown in FIG. In this case, it can be used for process control, life prediction of finished products, lot guarantee, and the like. Further, as shown in FIG. 6B, it may be formed in the scribe line 9 of the wafer 1. In this case, T
It can be used for process control in the same way as when it is built in EG.

The conductor to be evaluated, the monitor and the heater are not limited to being formed on the actual wafer, but may be formed on a so-called dummy wafer which undergoes a manufacturing process together with the actual wafer. Furthermore, in the case of off-line evaluation, it may be built in a subject other than the wafer.

The conductors to be evaluated, the monitor and the heater are basically arranged in the same layer, but in the case of a multi-layer wiring structure, these can be appropriately arranged in different layers or the same layer.
However, it is desirable that the conductor to be evaluated and the monitor are as close as possible. Even when the wiring formed in the wafer is used, not only the wiring shown in FIG. 5C but also the wiring of all layers can be used.

When the through-hole conductor is the conductor to be evaluated, the through-hole can be formed and evaluated.

Further, the material forming the conductor to be evaluated is not limited to aluminum, but may be another metal. Also,
The conductor to be evaluated is not limited to one formed in a linear shape, and may be one formed in a thin film shape. In short, a conductor formed of a metal that causes an electromigration phenomenon in a state where the electromigration phenomenon is likely to occur is an object for electromigration evaluation.

Further, it is desirable that the specific constitution of the temperature medium supply device, the constant temperature bath, the contactor, etc. is appropriately selected according to the usage situation and conditions such as on-line or off-line use. Further, the temperature medium supply device and the constant temperature bath may be omitted.

[0064]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.

By maintaining the temperature of the conductor to be evaluated constant, it is possible to avoid occurrence of so-called thermal runaway such as disconnection or burnout due to resistance heat generation due to energization of the conductor to be evaluated. In the above, only the electromigration phenomenon can be caused, and as a result, the current density coefficient n and the activation energy Ea can be obtained accurately in a short time, and the electromigration life can be evaluated in a short time and accurately. Can be done.

By preventing runaway due to self-heating of the conductor to be evaluated, the current density can be set large, and therefore the time required for electromigration evaluation can be further shortened.

A conductor to be evaluated is formed on a wafer, and an electromigration evaluation method is performed on the conductor to be evaluated, thereby performing electromigration evaluation on a semiconductor device (product) formed on a wafer as a test object. Therefore, the process control of the wafer can be executed, and the lot guarantee of the wafer and the quality guarantee of the semiconductor device can be ensured. Further, when adopting a new material, it becomes possible to acquire design data in a short time.

For example, in the case of being used for wafer process control, when the conductor to be evaluated is evaluated as rejected or low, process control or other Since it is possible to promptly take measures against the abnormal condition, it is possible to prevent the deterioration of the quality of the semiconductor device as a product. In addition, since the wafer that has been evaluated as rejected can be stopped from being put into the post-process, it is possible to prevent the shipment of the semiconductor device having a short electromigration life and low reliability to the market. .

By disposing the monitor and the heater close to the conductor to be evaluated, the temperature change of the conductor to be evaluated can be accurately monitored, and the heating operation of the heater based on the measurement result allows the conductor to be evaluated to be heated. Since the temperature can be feedback-controlled to be constant, the electromigration evaluation can be accurately executed, and the time required for the evaluation can be further shortened.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an electromigration evaluation apparatus according to an embodiment of the present invention.

FIG. 2 shows a subject that is an example of the present invention,
(A) is a plan view showing a semiconductor wafer, (b) is its TE
It is an enlarged partial top view of G.

3 (a) and 3 (b) are enlarged partial plan views showing another embodiment of a conductor to be evaluated, a monitor and a heater.

4 (a), (b), and (c) are enlarged partial plan views showing an embodiment in which two wirings are formed on the wafer.

5 (a), (b), and (c) are enlarged partial plan views showing an embodiment in which one wiring is formed on the wafer.

FIG. 6A is a plan view showing an embodiment in which a conductor to be evaluated, a monitor and a heater are built in a pellet portion of a wafer, and FIG. 6B is a conductor, a monitor and a heater to be evaluated are formed in a scribe line of a wafer. It is a top view showing the inserted example.

[Explanation of symbols]

1 ... Wafer (subject), 2 ... TEG, 3 ... Aluminum wiring (conductor to be evaluated), 4 ... Monitor, 5 ... Heater, 6
... pad, 10 ... electromigration evaluation device, 11 ... thermostat, 12 ... semiconductor wafer loading / unloading port, 1
3 ... Electromigration measuring device, 14 ... 1st
Contactor, 15 ... Temperature medium supply device, 16 ... High temperature tank, 17
... low temperature tank, 18 ... air duct, 19 ... damper, 20 ... second contactor, 21 ... temperature measuring device, 22 ... controller, 23 ... third contactor, 24 ... temperature control device, 25 ... wafer stage, 26 ... wafer Stage temperature controller.

Claims (6)

[Claims] 1. An electromigration evaluation method in which an electric current is caused to flow through a conductor to be evaluated made of metal with a predetermined current density to evaluate the electromigration life of the conductor to be evaluated. The temperature change of the conductor to be evaluated is measured while the temperature of the conductor to be evaluated is controlled by energization to keep the temperature of the conductor to be evaluated constant based on the temperature measurement data. Characteristic electromigration evaluation method. 2. The change in the resistance value of the evaluated conductor itself is measured to measure the temperature change of the evaluated conductor itself, and the energization to the evaluated conductor itself is controlled based on the measured data. The electromigration evaluation method according to claim 1, wherein the temperature control of the conductor to be evaluated is performed by the above. 3. An electromigration evaluation apparatus for applying a current with a predetermined current density to a conductor to be evaluated made of metal to evaluate the electromigration life of the conductor to be evaluated, wherein current is passed through the conductor to be evaluated. At this time, a temperature measuring device for measuring the temperature change of the conductor to be evaluated, and a temperature control device for maintaining a constant temperature of the conductor to be evaluated by controlling energization based on the measurement data An electromigration evaluation device characterized by. 4. The temperature measuring device is configured to measure the temperature change by measuring the change in resistance value, and the temperature control device is configured to control the temperature by changing the supply power. The electromigration evaluation apparatus according to claim 3, wherein: 5. A body having a conductor to be evaluated formed of a metal is provided, and a current is caused to flow through the conductor to be evaluated at a predetermined current density to evaluate the electromigration life of the conductor to be evaluated. In an electromigration evaluation subject, a conductor for temperature measurement that indirectly measures a temperature change of the conductor to be evaluated is laid in the main body close to the conductor to be evaluated and electrically insulated. An electromigration evaluation subject characterized by the above. 6. A body having a conductor to be evaluated formed of a metal is provided, and a current is caused to flow through the conductor to be evaluated with a predetermined current density to evaluate the electromigration life of the conductor to be evaluated. In the electromigration evaluation subject, a heating resistor that indirectly heats the conductor to be evaluated by energizing the main body is placed close to the conductor to be evaluated and electrically insulated. An electromigration evaluation subject characterized by.