KR20090050431A - Apparatus for measuring electromigration - Google Patents

Abstract

An apparatus for measuring electromigration characteristics is disclosed. The electromigration measuring apparatus according to the present invention is a device capable of simultaneously performing electromigration measurement on a plurality of specimens (DUT1 to DUT20) because a plurality of specimens (DUT1 to DUT20) are connected in series, and a plurality of specimens (DUT1 to DUT20). Each of the switches (BPSW1 ~ BPSW20) and resistors (R1 ~ R20) is connected in parallel to prevent the opening of the entire circuit in the short circuit during the measurement process.

Electromigration, Measurement

Description

Electromigration Evaluation Apparatus {Apparatus For Measuring Electromigration}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the electromigration characteristics of a material, and more particularly, to an electromigration measuring apparatus that can measure electromigration characteristics for a plurality of specimens simultaneously and is low in manufacturing cost.

Electromigration is a phenomenon that occurs when a high current flows over a long period of time in a metal wiring such as aluminum or copper applied to a semiconductor integrated circuit.

Specifically, when a high-density current flows through the metal wiring over a long period of time, the metal atoms constituting the wiring are migrated in the opposite direction to the current direction by particles such as electrons, so that local vacancies are formed and opposite atoms are formed on the opposite side. The accumulation phenomenon is called electromigration.

In conclusion, electromigration can be understood as a phenomenon in which the resistance value of the metal wiring is changed by the migration of the metal atoms constituting the metal wiring by the influence of the current flowing through the metal wiring.

As a material in which electromigration is prominent, aluminum is a representative material applied to a semiconductor integrated circuit process. In addition, even in alloys such as indium-gold or tin-nickel, the low melting point elements of the alloy elements preferentially migrate to change the composition in the direction in which the current flows, and as a result, electromigration may occur in which the resistance value is changed.

On the other hand, in the field of semiconductor integrated circuits, it is desirable to prevent the electromigration phenomenon from occurring, because such electromigration increases the resistance value of the metal wiring and eventually causes disconnection of the metal wiring, thereby lowering the reliability of the semiconductor. Related research is being actively conducted.

For electromigration related research, accurate and rapid measurement of electromigration is essential. In general, the measurement of electromigration refers to measuring a voltage drop generated by applying a constant current to a predetermined material, for example, aluminum, and is usually measured until the resistance value of aluminum is above or below a certain threshold. Continue.

Therefore, the electromigration measurement requires a considerable time, and in order to solve this problem, a method of simultaneously measuring the electromigration of a plurality of specimens has been devised, but even in this case, a current-voltage tester is required for each of the plurality of specimens. There was a problem that the price of the measuring device is ridiculously high.

Accordingly, the present invention has been made to solve the problems of the prior art as described above, to provide an electromigration measuring apparatus capable of measuring the electromigration characteristics of a plurality of specimens at the same time, significantly reducing the measurement time Has its purpose.

In addition, an object of the present invention is to provide an electromigration measuring apparatus capable of simultaneously measuring electromigration characteristics of a plurality of specimens and having low manufacturing cost.

Another object of the present invention is to provide an electromigration measuring apparatus capable of simultaneously measuring electromigration characteristics of a plurality of specimens, and having improved measurement reliability.

In order to achieve the above object, the electromigration measuring apparatus according to the present invention is characterized in that the plurality of specimens for the electromigration measurement is configured to be connected in series with each other.

In order to achieve the above object, the electromigration measuring apparatus according to the present invention is a device capable of simultaneously measuring the electromigration of a plurality of specimens because a plurality of specimens are connected in series with each other, The switch and resistor are connected in parallel to prevent the opening of the entire circuit during the short circuit of the specimen.

In addition, the electromigration measuring apparatus according to the present invention includes a voltage source for applying a voltage to the plurality of specimens; And a current-voltage meter connected in parallel with the plurality of specimens to measure current-voltage characteristics.

The resistance may have a resistance value larger than that of the specimen.

The switch may be a solid state relay (SSR).

The voltage source may be a voltage source for constant current mode.

The current-voltage meter may be one.

A switch may be further installed between the current-voltage meter and the plurality of specimens.

According to the present invention, it is possible to simultaneously measure the electromigration characteristics of a plurality of specimens, thereby reducing the time required for the electromigration measurement.

In addition, according to the present invention, it is possible to measure the electromigration characteristics of a plurality of specimens at the same time, but only one current-voltage tester is required, thereby reducing the manufacturing, use, and management costs of the electromigration measuring apparatus.

DETAILED DESCRIPTION OF THE INVENTION The following detailed description of the invention refers to the accompanying drawings that show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that the various embodiments of the present invention are different but need not be mutually exclusive. For example, certain shapes, structures, and characteristics described herein may be embodied in other embodiments without departing from the spirit and scope of the invention with respect to one embodiment. In addition, it is to be understood that the location or arrangement of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention, if properly described, is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. do.

EM  Basic configuration of the measuring device

As described above, the present invention relates to an EM measuring apparatus 100 for measuring the electromigration (hereinafter abbreviated as 'EM') characteristics of a specimen, for example, a metal such as Al. Here, the basic characteristic of the EM characteristic is to evaluate the rise of the voltage required to flow a constant current due to the increase in resistance of the specimen over time while allowing a constant current to flow through the device under test (DUT).

1 is a block diagram showing the configuration of an EM measuring apparatus 100 according to an embodiment of the present invention. As shown, the EM measuring apparatus 100 is largely comprised of two parts, the host computer 110 and the test part 120.

Referring to FIG. 1, the host computer 110 is largely composed of three parts: a parameter value input unit 112, a recording unit 114, and a test unit 120.

First, the host computer 110 is responsible for all the operation and control of the EM measuring device 100, such as operating the components installed to measure the EM characteristics of the specimen (DUT), and stores the measured EM characteristic results. A predetermined program is mounted.

The parameter value input unit 112 inputs various basic parameter values necessary for the EM measurement process. Here, the basic parameter value may be, for example, an initial resistance value of the specimen (DUT), a fail determination range of the specimen that appears according to the EM phenomenon, and the like.

The recorder 114 records the EM measurement result of the specimen DUT and various information generated during the EM measurement process.

The control unit 116 controls the overall operation of the components constituting the EM measurement apparatus 100 according to a predetermined program mounted in the host computer 110.

The operation of the parameter value input unit 112, the recording unit 114, and the control unit 116 will be described in detail through the EM characteristic measurement process of the specimen (DUT) described below.

The test unit 120 actually measures the EM characteristics of the specimen (DUT) mounted on the EM measurement apparatus 100. EM measuring apparatus 100 provided by the present invention may be equipped with at least one specimen (DUT), and as a result can measure the EM characteristics for each of the plurality of specimen (DUT) at the same time.

EM  Of measuring device Test  Configuration

2 is an equivalent circuit diagram showing the configuration of the test unit 120 of the EM measurement apparatus 100 according to an embodiment of the present invention.

As shown, the test unit 120 is equipped with 20 specimens (DUT1 ~ DUT20) for measuring EM characteristics, 20 specimens (DUT1 ~ DUT20) are connected in series with each other, 20 specimens (DUT1 ~ DUT20) ), Bypass switches BPSW1 to BPSW20 and bypass resistors R1 to R20 are connected in parallel. That is, referring to FIG. 2, the test unit 120 includes a plurality of EM measurement specimens DUT1 to DUT20 in parallel with the bypass switches BPSW1 to BPSW20 and the bypass resistors R1 to R20. It can be understood as a connected configuration. In addition, the current-voltage measuring instrument 122 is connected in parallel with each of the plurality of specimens DUT1 to DUT20 connected in series, and the switch SW1 to the current-voltage measuring instrument 122 and the plurality of specimens DUT1 to DUT20. SW40) is connected. In addition, the voltage source 124 is connected to the test unit 120.

Meanwhile, in FIG. 2, all 20 specimens (DUT1 to DUT20) are mounted on the EM measuring apparatus 100, but the present disclosure is not limited thereto, and each of the specimens mounted by mounting more or less specimens may be used. EM measurement is possible at the same time. For reference, the circuit configuration of the specimens (DUT3 ~ DUT18) in Figure 2 is shown as a specimen (DUTx) for convenience of drawing.

The current-voltage meter 122 measures the EM characteristic of the specimen (DUT), i.e., the rise in voltage required to flow a constant current due to an increase in the resistance of the pure metal or alloy over time while passing a constant current through the specimen. It acts as a real measure. In general, since the voltage rise measured in the EM evaluation is a very small value, the current-voltage meter 122 used in the EM measuring device 100 should have high precision. Since the internal configuration and operating principle of the current-voltage measuring instrument 122 are well known technologies, details thereof will be omitted herein.

On the other hand, since the EM measuring device 100 can simultaneously measure EM for a plurality of specimens even using only one current-voltage tester 122, the manufacturing cost of the EM measuring device becomes low, and the use of the EM measuring device and Management becomes easy.

The voltage source 124 serves to supply power for flowing a constant current to the plurality of specimens (DUT1 to DUT20). Therefore, in the EM measuring apparatus 100, it is preferable to use a voltage source for constant current mode, and also to use a direct current (DC) power source. The voltage source 124 may be connected in series with an ammeter 126 to confirm whether a predetermined value of current is supplied to the specimen.

The material of the plurality of specimens DUT1 to DUT20 may be a pure metal such as aluminum or copper, or an alloy such as indium-gold or tin-nickel, in which EM phenomenon is expected to occur.

A plurality of specimens (DUT1 ~ DUT20) are connected in series with each other, the circuit configuration of such a test unit 120 can measure the EM characteristics of the plurality of specimens (DUT1 ~ DUT20) at the same time, reducing the EM measurement time There is an advantage.

In addition, in consideration of the fact that a high-density current should be flowed to the specimen for EM measurement, there is an advantage that a high-density current can be flowed to the plurality of specimens (DUT1 to DUT20). When a plurality of specimens are connected in series, a current having the same value as the current supplied by the voltage source flows in each of the plurality of specimens regardless of the number of specimens. However, when a plurality of specimens are connected in parallel, a current corresponding to a value obtained by dividing the current supplied by the voltage source by the number of specimens flows in each of the plurality of specimens, thereby providing a high density of current required for EM measurement. There are no drawbacks. Of course, if the capacity of the voltage source is increased, the above-mentioned disadvantages can be solved to some extent, but instead, the capacity of the voltage source is increased, which increases the manufacturing cost of the EM measuring device and causes the circuit breakage due to the high current supplied from the voltage source. There is a possibility that problems such as these may occur.

Both ends of the plurality of specimens DUT1 to DUT20 are connected to both ends of the current-voltage meter 122, respectively. At this time, as shown in Figure 2, the left end of each specimen (DUT1 ~ DUT20) is connected to the left end of the current-voltage measuring instrument 122, and the right end of each specimen (DUT1 ~ DUT20) is a current-voltage measuring instrument ( 122) is connected to the right end.

In addition, both ends of the plurality of specimens DUT1 to DUT20 are connected to both ends of the voltage source 124, respectively. At this time, as shown in Figure 2, the left end of each specimen (DUT1 ~ DUT20) is connected to the left end (+ pole) of the voltage source 124 and the right end of each specimen (DUT1 ~ DUT20) is a voltage source 124 It is connected to the right end (-pole) of).

If the bypass switches (BPSW1 to BPSW20) cannot measure any of the plurality of specimens (DUT1 to DUT20) connected in series with each other, for example, the resistance value of the specimen exceeds the initial setting value, For example, when the EM measurement itself is not required or when the specimen is not mounted from the beginning (that is, in the present embodiment, EM measurement is possible for up to 20 specimens, but only fewer specimens are mounted). The entire circuit of) is opened to prevent operation. That is, when the bypass switch BPSW1 to BPSW20 has a defect in any one of the plurality of specimens DUT1 to DUT20, a circuit is connected instead of the specimen.

In the EM measuring apparatus 100, it is preferable that one bypass switch BPSW is installed per one specimen DUT. Therefore, when the 20 specimens DUT1 to DUT20 are mounted, all 20 bypass switches BPSW1 to BPSW20 may be installed.

The bypass switches BPSW1 to BPSW20 may use an SSR (Solid State Relay) that can be turned on and off by a control signal of the controller 116 and that can be used even at a large current capacity. SSR is a relay in which switching is performed using a switching semiconductor element without a mechanical contact structure. The SSR isolates an input from an output using an optical element, and blocks noise from the load side from being fed back to the input side. In addition, the SSR can operate under low voltage or low current, and can be directly driven by DTL, TTL, C-MOS, and LINEAR ICs, and also has advantages in phase control. In addition, SSR has the advantage of high reliability, long life, strong against noise and shocks such as electromagnetic waves, small signal operation, and fast response speed.

When the bypass resistors R1 to R20 are suddenly shorted (that is, disconnected) as the EM phenomenon progresses in any of the plurality of specimens DUT1 to DUT20 connected in series with each other, the entire circuit of the test unit 120 Is opened so that the operation becomes impossible. That is, when an unexpected sudden short circuit occurs in any one of the plurality of specimens DUT1 to DUT20 with the bypass resistors R1 to R20 (that is, the sudden switch (BPSW) does not operate suddenly). If a short circuit occurs, connect the circuit in place of the specimen.

In order for the bypass resistors R1 to R20 to perform the roles as described above, the bypass resistors R1 to R20 should be connected to the plurality of specimens DUT1 to DUT20 in parallel. In addition, the bypass resistors R1 to R20 have a resistance value that is much larger than the resistance value of the specimen, for example, a resistance of 1000 kV, because the current must flow only to the specimen when the specimen is not shorted. desirable.

In the EM measuring apparatus 100, it is preferable that one bypass resistor R is installed per one specimen DUT. Therefore, when the 20 specimens DUT1 to DUT20 are mounted, all 20 bypass resistors R1 to R20 may be installed.

The switches SW1 to SW40 installed between the current-voltage meter 122 and the plurality of specimens DUT1 to DUT20 serve to determine the specimen DUT to which the EM characteristic is measured through on / off operation. As a result, it is possible to measure the EM characteristics of the plurality of specimens DUT1 to DUT20 using only one expensive current-voltage meter 122 requiring high precision.

In the EM measuring apparatus 100, it is preferable that a pair of switches SW are installed per one specimen DUT. Therefore, when mounting 20 specimens DUT1 to DUT20, all 40 switches SW1 to SW40 may be installed. At this time, a pair of switches (for example, SW1 and SW21) is used to connect the current-voltage measuring instrument 122 and the specimen (DUT1), it is preferable to close and open at the same time.

EM  Characterization process

3A and 3B are flowcharts illustrating an EM measuring process of the EM measuring apparatus 100 according to an exemplary embodiment of the present invention.

As shown, the EM characteristic measurement process for a plurality of specimens (DUT1 ~ DUT20) can be largely divided into two parts, STEP1 and STEP2.

FIG. 3A is a flow chart for STEP1 (S001 to S009), in which a resistance value for each of the specimens DUT1 to DUT20 is tested. In this step, if the resistance of the specimens DUT1 to DUT20 is too low or too high than the reference voltage, it is determined to be defective.

FIG. 3B is a flowchart of STEP2 (S010 to S018) executed after STEP1, in which an EM characteristic is tested on a specimen except for a specimen determined to be defective in STEP1.

Referring to Figure 3a to be described in detail with respect to the STEP1 process.

First, an initial condition is input to the host computer 110 and a file name is set (S001). The input initial condition may include a resistance value range of the specimens DUT1 to DUT20, a voltage increase limit value of the specimens DUT1 to DUT20, and the like. For example, the range of the resistance value is 0.001 kV to 100 kV, and the voltage rise limit can be set to 10% (when the voltage rise value when the specimen is cut off by the EM phenomenon is set to 100%).

Subsequently, power is supplied to the SSR used as the bypass switches BPSW1 to BPSW20 (S002). The power supplied can be, for example, a DC voltage of 5V.

In STEP1, the resistance test is performed in the same procedure from DUT1 to DUT20 in the order of serial connection for each specimen. This is a process of determining whether the resistance value of the measured specimen is within the range of the initially set resistance value, and on / off of the bypass switches BPSW1 to BPSW20 connected in parallel with the specimens DUT1 to DUT20 according to the determination result. Is determined.

Next, the DUT1 is selected to start the resistance value test (S003). Since the DUT1 and the current-voltage meter 122 need to be connected for the resistance value test, SW1 and SW21 installed between the DUT1 and the current-voltage meter 122 are turned on (S004). At this time, since only the resistance value of the DUT1 should be measured, all of SW2 to SW20 and SW22 to SW40 other than SW1 and SW21 connected to the DUT1 are turned off.

Subsequently, the resistance value of the DUT1 is measured using the current-voltage meter 122 (S005), and then a pass or fail determination is performed according to the result (S006). The pass judgment is a case where the resistance values of the measured specimens DUT1 to DUT20 are included in the range of the initially set resistance values, and the fail judgment is a resistance value of the measured specimens DUT1 to DUT20 is included in the range of the initially set resistance values. If not, it is possible to determine whether or not the specimen (DUT1 ~ DUT20) is defective by such a resistance value determination.

Next, when the DUT1 is determined to fail, the BPSW1 connected in parallel with the DUT1 is turned on (S007), and after the fail information is stored (S008), the SW1 and SW21 which were turned on at S004 are turned off. (S009) Bypass switches BPSW1 to BPSW20 that are initially turned off are all controlled to be turned on when the resistance values of the specimens DUT1 to DUT20 fail.

If the pass is judged in S006, the flow advances to S009 to turn off the SW1 and SW21 which were turned on in S004. The bypass switches BPSW1 to BPSW20 that are initially turned off are all controlled to remain off when the resistance values of the specimens DUT1 to DUT20 pass.

Next, the resistance test of the specimens DUT2 to DUT20 is repeated (S009a / S009b).

The resistance test in STEP1 is subjected to the same process of S003 to S009 once in sequence for each specimen (DUT1 to DUT20). That is, in this embodiment, since 20 specimens DUT1 to DUT20 are connected, the processes of S003 to S008 may be repeated up to 20 times.

This completes the resistance test of STEP1, followed by the EM characteristic test of STEP2.

The process of STEP2 will be described in detail with reference to FIG. 3B.

First, DC power is supplied to the test unit 120 through the voltage source 124 (S010). At this time, the voltage source 124 may supply a constant DC current in the range of 1 to 5A.

In STEP2, the EM characteristics (voltage values) are tested in the same procedure from DUT1 to DUT20 in the order of serial connection for each specimen. This is the process of measuring the rise of the voltage that must be applied to flow the same current through the specimen over time.

Next, the DUT1 is selected to start the voltage value test (S011).

Next, the bypass switch BPSW1 for the DUT1 is checked (S012). At this time, if BPSW1 is on (this is because a fail determination is made for DUT1 in STEP1), the selection of DUT2 is made immediately (S011), and if BPSW1 is off (this is because a pass decision is made for DUT1 in STEP1). ) EM test of DUT1 continues.

Assuming that BPSW1 is off, the following test procedure will be described.

Next, since the DUT1 and the current-voltage meter 122 need to be connected for the EM characteristic test of the DUT1, the SW1 and the SW21 installed between the DUT1 and the current-voltage meter 122 are turned on (S013). At this time, since the EM characteristic test should be performed only for DUT1, all of SW2 to SW20 and SW22 to SW40 except SW1 and SW21 are turned off.

Next, the voltage value for the EM characteristic test of the DUT1 is measured (S014). At this time, tens of voltage values are measured for a very short time at very small time intervals, and the average value becomes the voltage value of DUT1.

Next, a pass or fail determination is made on the voltage value of the DUT1 measured in S015 (S015). At this time, the specific voltage value initially input is the reference for the pass or fail determination. The fail determination is a case where the voltage value of the DUT1 reaches the reference value, and when the DUT1 receives the fail determination, the BPSW1 connected in parallel with the DUT1 is turned on (S016) and the fail information is stored (S017). Next, SW1 and SW21 which were turned on in S013 are turned off (S018).

When the pass is determined in S015, the measured voltage value is displayed on the monitor and data is stored (not shown). When the storage of the data is completed, the process immediately proceeds to S018 and turns off the SW1 and SW21 which were turned on in S013.

Next, the voltage value test of the specimens DUT2 to DUT20 is repeated (S012a to S012c). That is, the voltage value test in STEP2 is subjected to the same process of S011 to S018 sequentially for each specimen (DUT1 to DUT20). However, since the repetition of steps S011 to S018 in STEP2 is repeated until the specimen (DUT) is determined to fail in S015, the number of repetitions of S011 to S018 may vary for each specimen according to the state of each specimen.

On the other hand, since all the specimens in which the EM characteristic test is started in STEP2 are measured until the failure is determined, the bypass switches BPSW1 to BPSW20 connected in parallel to all the specimens DUT1 to DUT20 are turned on. As such, when all of the bypass switches BPSW1 to BPSW20 are turned on, the power supply of the voltage source 126 is stopped and the EM characteristic test process for the specimens DUT1 to DUT20 is terminated.

In the present invention as described above has been described by the specific embodiments, such as specific components and limited embodiments and drawings, but this is provided to help a more general understanding of the present invention, the present invention is not limited to the above embodiments. For those skilled in the art, various modifications and variations are possible from these descriptions. Accordingly, the spirit of the present invention should not be limited to the above-described embodiments, and all of the equivalents or equivalents of the claims, as well as the appended claims, belong to the scope of the present invention. something to do.

1 is a block diagram showing the configuration of an electromigration measuring apparatus according to an embodiment of the present invention.

2 is an equivalent circuit diagram showing the configuration of a test unit of the electromigration measuring apparatus according to an embodiment of the present invention.

3A and 3B are flowcharts illustrating an electromigration measuring process of an electromigration measuring apparatus according to an exemplary embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100: electromigration measuring device

110: host computer

112: parameter value input unit

114: record book

116: control unit

120: test unit

122: current-voltage meter

124: voltage source

126: ammeter

Claims (8)

An electromigration measuring apparatus, characterized in that a plurality of specimens for electromigration measurement are configured to be connected in series with each other. A device in which a plurality of specimens are connected in series to each other to simultaneously perform electromigration measurement on a plurality of specimens. And a switch and a resistor connected to each of the plurality of specimens in parallel to prevent the opening of the entire circuit during the short circuit of the specimen during the measurement process. The method of claim 2, A voltage source for applying a voltage to the plurality of specimens; And And a current-voltage meter connected in parallel with the plurality of specimens to measure current-voltage characteristics. The method according to claim 2 or 3, And the resistance has a resistance value greater than that of the specimen. The method according to claim 2 or 3, The switch is an electromigration measuring device, characterized in that the solid state relay (SSR). The method of claim 3, The voltage source is an electromigration measuring apparatus, characterized in that the voltage source (Voltage Source for Constant Current Mode). The method of claim 3, And said current-voltage meter is one. The method of claim 7, wherein And a switch is further provided between the current-voltage meter and the plurality of specimens.

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