[0036] Example 2, such as image 3 As shown, the interconnect failure detection method of Embodiment 2 of the present invention includes the following steps:
[0037] In step s10, at least two interconnection line units with the same interconnection line scale are connected in series to form a failure detection circuit. Because the aforementioned electromigration phenomenon can only be found in interconnects up to a certain length, the size of the selected interconnection unit is actually based on the research needs of the electromigration phenomenon of interconnects of a specific length. . In order to facilitate the description, the second embodiment of the present invention still adopts such as figure 1 Copper interconnect line unit shown. For example, suppose figure 1 The resistance value of each copper interconnection line with a length of 400 microns shown is 500Ωm, then as figure 1 The minimum interconnection line unit composed of 5 copper interconnections in parallel is equivalent to an equivalent resistance with a resistance value of 100Ωm. However, by equating the interconnection line unit to a resistance, the interconnection line failure phenomenon can be quantitatively analyzed based on simple voltage and current measurement.
[0038] Such as image 3 As shown, in the second embodiment, the 16 copper interconnection line units are connected in series to form a failure detection circuit. As mentioned above, the resistance value of the interconnection line unit in Embodiment 2 of the present invention is 100Ωm, and the total resistance value of the failure detection circuit formed by connecting 16 interconnection line units in series is 16*100Ωm=1600Ωm. In fact, the purpose of using a plurality of interconnection line units connected in series to form a failure detection circuit is also to form an equivalent large resistance. Because as mentioned earlier, when the electromigration causes the interconnection line to fail, the two ends of the interconnection line will form an open circuit, and the resistance value of the equivalent resistance formed at this time will be higher than the resistance of the interconnection line under normal conditions. The value is greatly increased. The equivalent large resistance formed by the failure detection circuit will make the increase of the resistance value more significant, so as to find the phenomenon of interconnection failure earlier.
[0039] Step s20, input a test current to the failure detection circuit, and measure the voltage across the failure detection circuit to determine whether the interconnection line fails. According to step s10, the failure of the interconnection line caused by electromigration will greatly increase the resistance of the interconnection line. Then, by inputting the test current and measuring the voltage across the failure detection circuit, it can be found that the increase in resistance is caused The voltage changes.
[0040] In Embodiment 2 of the present invention, a test current Iin of 0.5 mA is input to the failure detection circuit. When the interconnection line has not failed, since the interconnection line units in the entire failure detection circuit are connected in series, they pass through each interconnection. The current of the line unit is equal to the test current. The voltage measured at the input and output ends of the failure detection circuit should be the product of the test current and the total resistance of the failure detection circuit, that is, the voltage across the failure detection circuit U=0.5mA*1600Ωm=0.8 V, use this voltage value U as the standard voltage value. When the interconnection line fails, the resistance value of the interconnection line generally increases by at least 20%, so the entire failure detection circuit will increase the resistance value by at least ΔR=1600Ωm*20%=320Ωm. In addition, multiplying the increased resistance ΔR with the input test current Iin can obtain the minimum voltage increase due to interconnection failure ΔU=ΔR*Iin=320Ωm*0.5mA=0.16V, and ΔU is used as the setting When the voltage measured at both ends of the failure detection circuit is greater than U+ΔU=0.8+0.16=0.96V, it is determined that there is an interconnection failure in the failure detection circuit.
[0041] As mentioned above, theoretically, the more interconnection line units are connected in series, the more significant the voltage change caused by the failure of the interconnection line can be measured. Therefore, the number of interconnection line units connected in series can also be determined according to the actual size of the chip to be tested, and especially for larger-scale chips, the failure detection circuit of Embodiment 2 of the present invention can quickly detect Failure of interconnection lines.
[0042] In step s30, if the measured voltage is less than the set voltage value, the interconnection line has not failed. According to step s20, when the voltage measured at both ends of the failure detection circuit is less than 0.96V, since the test current is stable, it means that there is no abnormal increase in the total resistance in the failure detection circuit, so the failure detection circuit No interconnection failures occurred in the.
[0043] In step s40, if the measured voltage is greater than or equal to the set voltage value, the interconnection line fails. According to step s20, when the voltage measured at both ends of the failure detection circuit is greater than or equal to 0.96V, since the test current is stable, it means that an abnormal increase in the total resistance has occurred in the failure detection circuit, and the resistance The increase in value exceeds 20%, so it can be considered that an interconnection failure has occurred in the failure detection circuit.
[0044] In step s50, the input and output of the failure detection circuit where the interconnection line fails are connected to form a Wheatstone bridge. As described in step s40, if the failure of the interconnection line is detected by the failure detection circuit, the input and output of the failure detection circuit are connected to form as Figure 5 The failure location circuit shown. The failure location circuit is actually a Wheatstone bridge (wheatstone bridge), the bridge includes such as Figure 5 Groups of 4 interconnection line units shown. Figure 5 The interconnection line unit group shown in is actually a combination of a plurality of the minimum interconnection line units. In the embodiment of the present invention, 16 interconnection line units are selected, and each interconnection line unit group includes 4 interconnection line units. The equivalent circuit of the Wheatstone bridge is as Figure 6 As shown, the interconnection line unit group 21 and the interconnection line unit group 24 are connected in series, the interconnection line unit group 23 and the interconnection line unit group 22 are connected in series, and the two groups of interconnection line unit groups are connected in parallel.
[0045] Step s60, input current to the Wheatstone bridge, measure the current direction at the midpoint of the Wheatstone bridge, and locate the position of the failed interconnection line according to the current direction. The working principle of the failure locating circuit formed by the Wheatstone bridge is as follows, combined Figure 5 with Figure 6 As shown, the first end point is taken between the interconnection line unit group 21 and the interconnection line unit group 22, the second end point is taken between the interconnection line unit group 23 and the interconnection line unit group 24, and the first end is taken between the interconnection line unit group 21 and the interconnection line unit group 22. An ammeter is set between the end point and the second end point. When the interconnection line has not failed, when the current Isin is input to the Wheatstone bridge, the interconnection line unit group 21, the interconnection line unit group 22, the interconnection line unit group 23, and the interconnection line unit group 24 are all It is composed of 4 interconnection line units with the same interconnection line scale. The resistance value of the 4 interconnection line unit groups is the same, so the voltage of the first terminal and the second terminal should be the same, so the ammeter No current can be detected. When the interconnection line fails, for example, assuming that the interconnection line unit group 21 fails, the resistance value of the equivalent resistance formed by the interconnection line unit group 21 will increase, so that when the current Isin is input to the Wheatstone bridge , The voltage drop on the interconnection line unit group 21 is greater than the voltage drop on the interconnection line unit group 23, so the voltage at the first terminal will be lower than the voltage at the second terminal, and the current will flow from the second terminal Flow to the first end. At this time, the pointer on the ammeter will indicate that the direction of the current is from the interconnection line unit group 23 to the interconnection line unit group 22. Of course, it is found that the current direction is from the interconnection line unit group 23 to the interconnection line unit group 22, and the interconnection line unit group 24 may fail. Here, the failure of the interconnection line unit group 21 is taken as an example for the convenience of description.
[0046] Therefore, as described above, according to the current direction indicated by the pointer on the ammeter, it is possible to quickly locate the interconnection line unit group in which the failed interconnection line is the interconnection line unit group 21. The interconnection line unit group of Embodiment 2 of the present invention is composed of four interconnection line units. According to the method of constructing a failure locating circuit, the four interconnection line units of the interconnection line unit group 21 are connected end to end. A Wheatstone bridge is formed, and an ammeter is also set between the two midpoints of the bridge, and current is input to the Wheatstone bridge. By observing the direction of current indicated by the pointer on the ammeter, the failure of the interconnection line can be finally located After finding the interconnection line unit that caused the failure of the interconnection line, you can find the 5 copper interconnection lines in the interconnection line unit through conventional inspection methods, such as microscope observation. There is a copper interconnection line with interconnection failure phenomenon.
[0047] Therefore, through the above-mentioned positioning method, it is possible to perform rapid positioning for a large-scale interconnection structure. As mentioned above, the Wheatstone bridge is constructed by connecting the interconnection structure end to end, measuring the current at the center point of the Wheatstone bridge, and quickly positioning the resistance value on the Wheatstone bridge according to the current direction indicated by the ammeter pointer The location of the abnormally changed interconnection line unit group, and by continuing to construct the Wheatstone bridge by the interconnection line unit group, the method of measuring the current direction will further reduce the positioning range of the interconnection line failure, so that it can be quickly located after several times. It is possible to finally find the location of the interconnection line unit where the interconnection line fails, and find the copper interconnection line where the interconnection line failure phenomenon eventually occurs through conventional inspection methods, such as microscope observation. Therefore, the interconnection line failure detection method of the present invention can not only quickly detect the phenomenon of interconnection line failure, but also quickly locate the location of the interconnection line where the failure occurs.
