JPH02114185A - Measuring apparatus of semiconductor - Google Patents

Abstract

PURPOSE:To shorten a time for measurement of a lifetime and to make the measurement precise by providing a semiconductor substrate heating means at the time of measurement of a wiring lifetime parameter and an activating energy, a constant current supplying means and a step current supplying means. CONSTITUTION:An activating energy is determined from an inclination formed when measuring points for a lifetime at each temperature determined with a current fixed are connected together, while a wiring lifetime parameter is determined from an inclination formed when measuring points at the time of the amplitude of a current being changed with the temperature fixed are connected together. Values obtained by these determinations are stored in ROM or the like in a personal computer 11. After the wiring lifetime parameter and the activating energy are determined, a semiconductor substrate 16 is subjected under a room temperature, a power switch 10c is changed over onto the step current side 10b, a step current is supplied and it is increased until a metal wiring in a semiconductor is disconnected. A voltage at each current value is measured by an ammeter 14 and a voltmeter 13 being interpositioned in a line of a power source 10. Thereby a wiring resistance can be determined, and these data are inputted to the personal computer 11, wherein computation for estimating the lifetime of the wire is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor measuring device that measures the lifetime of a semiconductor by performing an accelerated test on metal wiring formed in the semiconductor.

(Prior art) When measuring metal wiring in a semiconductor substrate by an accelerated test, it is first necessary to obtain the wiring life parameter n and the activation energy Ea (hereinafter referred to as parameter). The measurement was carried out using a measuring device as shown in the figure, which includes a heater 1 that heats the semiconductor substrate.
, a prober 2 and a constant current source 3.

By the way, these parameters can be determined by applying a constant current at a constant temperature (150 to 200° C.). That is, the lifespan at each temperature is determined with the current constant, and the activation energy Ea can be determined from the slope when these measurement points are connected. Further, the wiring life parameter n can be determined from the slope when connecting the measurement points when the temperature is constant and the magnitude of the current is changed. To determine these parameters, it takes several days to measure because there are many measurement points and it is necessary to increase the number of samples to reduce errors. Generally, a lot of effort is required because parameter measurements have to be taken at the same time.

Once the above parameters are determined, the semiconductor substrate 4 is then placed on the heater 1, and the heater 1 is
It is heated to 0° C. and a constant current is applied from the power source 3 using a prober. The lifespan is determined when the current flowing through the circuit becomes 0, that is, when the wiring is disconnected.

(Problem to be solved by the invention) However, in such conventional measuring devices,
The heating temperature is up to 300℃, and the current density that can be applied is 3X in relation to the cross-sectional area of the wiring.
There is a restriction that it can only flow up to 106A/cJ. This is because the disconnection mode that determines the life span is due to the movement of metal atoms along the grain boundaries.If the heating temperature exceeds 300°C, the atomic movement passes through the crystal grains and diffuses, resulting in different disconnection modes. This is because it becomes .

Also, if the current density is increased, the wiring life CCJ
−' Therefore, there were problems such as the life span measurement of the metal wiring took several days and the measurement results varied widely.

(Object of the invention) This invention was made in view of the problems as described in -.
Although the wire life parameter n and activation energy Ea of metal wires in a semiconductor are determined by the conventional method, the wire life can be determined by applying a step current without heater heating, and applying each data to the wire life equation. The purpose of this study is to calculate the wiring life by substituting , and thereby solve the problems mentioned in 2.

(Means for Solving the Problems) In order to achieve the above objects, the present invention is constructed as shown in FIG. 1.

The heating means a heats the semiconductor substrate when measuring the wiring life parameter n and the activation energy Ea.

The power source includes constant current supply means b2 for applying a constant current to the semiconductor substrate when measuring the wiring life parameter n and activation energy Ea, and step current supply means b2 for applying a step current to the semiconductor substrate when measuring the wiring life. It is equipped with

In the arithmetic processing section C, heating means a and constant current supply means S,
The wiring life parameter n and activation energy E obtained from
Life prediction is calculated based on data such as current value, voltage value, resistance value, etc. obtained from step current supply means b2 as well as step current supply means b2.

(Function) In the device of the present invention, the wire life parameter n and the activation energy Ea are measured by the same means as in the conventional method, and when measuring the wire life, the wire life is predicted by only applying a step current without heating the heater.

(Example) What is shown in FIG. 2 is a schematic configuration diagram of the present device.
is a power supply that incorporates a constant current generator and a step current generator, and has a switch 10c that can be switched between a constant current side 10a and a step current side 10b, and this power supply 10
A personal computer 11 (hereinafter referred to as a personal computer) is connected to. This personal computer 11 includes a CPU,
ROM.

It has a built-in RAM, etc., and is configured so that the magnitude and time interval of the step current as shown in the figure can be arbitrarily controlled, and the computer 11 stores the voltage V and current A until the wiring breaks as data at certain time intervals. It is structured so that it can be imported into the computer, stored, and calculated.

Also, the wiring life parameter n and the activation energy Ea
The value is stored in the ROM or the like in the personal computer 11.

Further, a nichrome wire 15a is built in the heater 15,
Power is applied from the power supply 10 above to a constant temperature (150 to 200
℃), a thermometer 15b is stored in the heater 15, and the temperature data T is also imported into the personal computer 11.

Further, a voltmeter 13 and an ammeter 14 are interposed between the line between the power source 10 and the prober 12, and these meters 13
．． Data measured by the computer 14 is configured to be imported into the personal computer 11 at certain time intervals.

Furthermore, a semiconductor 16 is placed on the heater 15,
It is configured to be heated by this heater 15 and to be able to apply a constant current or step current to the metal wiring of the semiconductor substrate 16 via the second prober 12.

Next, an example of use and operation of the device of the present application will be explained.

In order to determine the wiring life, first, as a premise, the wiring parameter n and the activation energy Ea are measured.

In that case, similarly to the conventional example above, the semiconductor substrate 16 is placed on the heater 15 and kept at a constant temperature (150 to 200°C).
At the same time, the switch 10c is set to the constant current side 10a.
Then, a constant current is applied to the metal wiring of the semiconductor substrate 16 via the prober 12.

In other words, the lifespan at each temperature is determined by keeping the current constant, and the activation energy Ea is determined from the slope when connecting these measurement points.
Also, the wiring life parameter n is determined from the slope when connecting the measurement points when the temperature is kept constant and the magnitude of the current is changed, and these values are stored in the ROM or the like in the personal computer 11.

These parameters obtained in this way do not need to be measured again unless the type of wiring is different, and can be continued to be used in subsequent measurements.

After determining the wiring life parameter n and the activation energy Ea, the semiconductor substrate 16 is brought to room temperature, the switch 10c of the power supply 10 is switched to the step current side 10b, and a step current is supplied until the metal wiring in the semiconductor is disconnected. I'm going to make it bigger. By measuring the voltage at each current value with an ammeter 13 and a voltmeter 14 interposed in the line of the power supply 10, the wiring resistance R at that time is determined, and these data are stored manually in the personal computer 11. is,
In this personal computer 11, a calculation process for predicting the lifespan of the wiring is performed based on a formula as described later.

Next, the operation of the apparatus of the present invention will be explained based on the flowchart of FIG.

Starting with heater heating and constant current application, the wiring life parameter n and activation energy Ea are measured by conventional means (step 100), and then the resistance at the initial temperature is measured at room temperature (step 102).
, a step current is applied and increased until the wire breaks (steps 104 and 106), and the resistance value, current value, and time data until the wire breaks are manually entered into the personal computer at certain time intervals. Step 10
If NO in step 6, the process returns to step 104 to continue supplying the step current. If YES in step 106, that is, if the wiring is disconnected, the measurement ends there (
Step 108). When the measurement is completed, the wiring life is calculated by estimating the wiring effective temperature from the resistance value based on the above parameters and data, and the first wiring life S is calculated (step 11o).

That is, in the device of the present application, prediction of the wiring life is performed by the following means.

By applying a step current, the temperature and current change over time, and the temperature is caused by Joule heat due to the current and depends on the step current value.

In addition, the wiring effective temperature T (t) is the initial (room temperature) temperature T.

, initial resistance Ro, then R(t) = ROX [1+β(T (t) −To
] R(t) is measured using a digital multimeter β: Temperature coefficient 3.7×10 −3° C. −1 Therefore, from the above measured values, the wiring effective temperature T(1) can be found as follows.

T U) =To+R(t) -RO β Therefore, the empirical formula 1-'xEXP(Ea
/Rt), the wiring life due to the step current is determined by the following formula.

By the way, the wiring life is measured at a certain current value (2) and temperature (T).

n and Ea are parameters determined by conventional methods.

Here, I (t) Nistep current T(t);
Wiring effective temperature R(t) when step current is applied; wiring resistance value when the wiring temperature rises due to step current application In the present device, the above I (t) and T (t
) and R(t) over time, and substitute the values into the above integral equation, and under certain usage conditions 1. By substituting the value for T (denominator formula), the wiring life can be found.

According to the processing method described above, since the life can be calculated using the above formula, it is possible to change the stress over time, and therefore an accelerated test that is three to four orders of magnitude faster than the conventional method is possible.

The first wiring life S1 is calculated as follows,
The result is stored in memory as S (step 112).

The above test is then repeated 5-10 times and the average value is calculated. That is, if 81≦5 in step 114, the process returns to step 102 and the test is repeated, and S,≧
5, in step 116 the average value So
is calculated, the wiring life is determined based on this, and the test is terminated. The above measurement time is 2 minutes or less per time, and even if the average value is calculated by repeating 5 times, the measurement can be performed in about 10 minutes.

The methods shown in Figure 4 (a) and (b) utilize the fact that the length of the wiring life is correlated with the step current value I at the time of disconnection, and are used to detect defects in the metal wiring in the semiconductor substrate. It shows the measured quantity of. That is, in the semiconductor process, the metal wiring 16a formed on the substrate 16'' may have a wiring width narrowed at a certain point or a film thickness reduced due to deterioration of step coverage. However, the narrowing of the wiring width occurs during the etching process when forming the wiring pattern, and the deterioration of step coverage occurs during the metal deposition process.

By the way, when a device to be measured with such wiring defects is measured using the apparatus of the present invention as shown in FIG.
As shown in b), it was found that wiring without defects shows an electrical distribution as shown by the solid line, whereas wiring with defects shows a highly variable electrical distribution as shown by the broken line. .

In addition, the above example measures the disconnection failure life due to electromigration, which causes atomic movement caused by heat and current. Migration, in which atoms move due to stress, can also be used to evaluate defects caused by heat or stress generated in fine interconnects with a width of 3 μm or less. In other words, the test period for heat and stress migration would take 2 to 4 months using conventional equipment, but when measuring with the device of the present invention, the wiring is placed in a high-temperature bath for several days and heated. However, if defects due to migration are generated to some extent and then measurements are made using step current, the fourth
A variation distribution as shown in figure (b) can be obtained,
The reliability of the wiring can be evaluated from the results of the variation distribution.

(Effects of the Invention) As is clear from the following explanation, the device of the present application only heats the object to be measured and supplies a constant current when measuring the wiring life parameters and activation energy. A step current is supplied for the measurement 2 judgment of the lifespan, and it is possible to predict the lifespan based on the equation of the wiring lifespan based on the obtained data such as current value, voltage value, resistance value, etc. It is possible to measure the lifespan in an extremely short time of less than 2 minutes, and since data with small measurement variations can be obtained, highly accurate lifespan measurement is possible.

[Brief explanation of the drawing]

Fig. 1 is a diagram corresponding to the claims of the device of the present invention, Fig. 2 is a schematic configuration diagram of the device of the present invention, Fig. 3 is a flowchart 1 showing the operation of the device of the present invention, and Fig. 4 (a) and (b) are the device of the present invention. FIG. 2 is an explanatory diagram showing the measurement ρ when there is a defect in the measured object using the method, in which (a) is a cross-sectional view of the measured object, and (b) is the maximum value of the step current during measurement. FIG. 5 is a schematic configuration diagram of a conventional device. a... Heating means b... Power supply b B... Constant current supply means b2... Step current supply means C... Arithmetic processing unit 10... Power supply 11... Personal computer 12... Prober 13 ... Ammeter 14 ... Voltmeter 15 ... Heater 16 ... Semiconductor substrate patent applicant Nissan Motor Co., Ltd.

Claims (1)

[Claims] 1. In a measuring device for measuring the accelerated life of a metal wiring formed in a semiconductor using a prober, a heating means for heating a semiconductor substrate when measuring a wiring life parameter n and activation energy Ea. and constant current supply means for applying a constant current to the semiconductor substrate when measuring the wiring life parameter n and activation energy Ea, and step current supply means for applying a step current to the semiconductor substrate when measuring the wiring life. A calculation for predicting the lifespan based on the power supply, the wiring lifespan parameter n obtained from the heating means and the constant current supplying means, the activation energy Ea, and the current value, voltage value, and resistance value data obtained from the step current supplying means. A semiconductor measuring device comprising a processing section.