CN109742066B - Electromigration test structure and test method - Google Patents
Electromigration test structure and test method Download PDFInfo
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- CN109742066B CN109742066B CN201811654050.6A CN201811654050A CN109742066B CN 109742066 B CN109742066 B CN 109742066B CN 201811654050 A CN201811654050 A CN 201811654050A CN 109742066 B CN109742066 B CN 109742066B
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Abstract
The invention discloses an electromigration test structure, which comprises a metal test structure, wherein the metal test structure is provided with a head end and a tail end and comprises at least two metal test lines; the metal connection structure is electrically connected with the head end and the tail end of the metal test structure so as to enable metal test wires in the metal test structure to be connected in parallel, the metal connection structure is further provided with a loading current node and a measuring voltage node, the loading current node is used for applying currents of the first test metal wire and the second test metal wire, and the measuring voltage node is used for measuring the voltage of the first test metal wire and the second test metal wire after the first test metal wire and the second test metal wire are connected in parallel. The invention can improve the failure time judgment of the test system on each test sample and can improve the recommendation accuracy of the test life. The invention also discloses a testing method of the electromigration test structure.
Description
Technical Field
The present invention relates to the field of semiconductor circuit design, and more particularly, to an electromigration test structure. The invention also relates to a test method based on the structure.
Background
As technology nodes are scaled down, the reliability of electromigration of technology-updating metal interconnect lines becomes more and more important and challenging. Electromigration (EM) is one of the major failure mechanisms in microelectronic devices, which causes open and short circuits in the metallization, resulting in increased device leakage currents. After devices develop into submicron and deep submicron, the width of metal lines is continuously reduced, and the current density is continuously increased, so that the devices are more prone to failure caused by electromigration. Therefore, with the progress of the process, the evaluation of EM is receiving much attention.
The direct cause of electromigration is the movement of metal atoms. When a large current passes through the interconnection lead, electrons are driven by electrostatic field force to move from the cathode to the anode, the electrons moving at high speed exchange energy with metal atoms, and the atoms are subjected to violent electron impact force, namely electron wind force. However, in fact, the metal atoms are also subjected to electrostatic field forces in the opposite direction. When the current density in the interconnect is high, a large number of electrons moving towards the anode collide with atoms, so that the metal atoms are subjected to an electron wind force greater than the electrostatic field force. Therefore, the metal atoms are driven by the electron wind force to directionally diffuse from the cathode to the anode, so that electromigration occurs.
Electromigration in the front-end-of-line process is a commonly used reliability evaluation test method. The conventional EM test structure is shown in fig. 1 (Via Up or Via Down test, fig. 1 is Via Up structure, and vice versa).
The metal Critical Dimension (CD) of the back end becomes smaller and smaller after the current technology point in the industry is scaled to 28 nm and below. Without a corresponding reduction in the voltage and current density requirements of the device. Meanwhile, electromigration needs a certain length to obviously generate electromigration, and the length is generally greater than the length of the Blech length, for example, the electromigration line is greater than or equal to 400um (JEDEC standard) in FIG. 1. Thus, according to R ═ ρ L/S, the resistance value becomes larger and larger at the same test length. And the failure criterion of EM is
Therefore, under the conditions that the initial resistance is large and the size of the invalid physical cavity caused by the EM effect is almost the same, the detection of 10% resistance change becomes more and more difficult. Influences the correct judgment of the EM failure time point (TTF), thereby influencing the evaluation of the test life (life).
Meanwhile, as the technology node is reduced, the resistance may be changed due to the stress effect caused by the failure of the EM and the good or bad process of the via. This requires detecting where the failure point occurs in the wire (cathode or anode) to make a preliminary determination of the likely cause of the failure. For further FA authentication. Current test structures cannot determine where a change in resistance results.
Disclosure of Invention
The technical problem that this application will be solved is, design an electromigration test structure, can promote test system to judge and can promote the recommendation accuracy of test life-span to the dead time of every test sample.
In order to solve the above technical problem, the present invention discloses an electromigration test structure, which includes: a metal test structure having a head end and a tail end, the metal test structure comprising at least two metal test lines; the metal connection structure is electrically connected with the head end and the tail end of the metal test structure so as to enable metal test wires in the metal test structure to be connected in parallel, the metal connection structure is further provided with a loading current node and a measuring voltage node, the loading current node is used for applying currents of the first test metal wire and the second test metal wire, and the measuring voltage node is used for measuring the voltage of the first test metal wire and the second test metal wire after the first test metal wire and the second test metal wire are connected in parallel.
Preferably, the metal connection structure is provided with a cathode structure and an anode structure, one end of the metal connection structure is electrically connected with the cathode structure, and the other end of the metal connection structure is electrically connected with the anode structure.
Preferably, the load current node comprises a first load current node and a second load current node, the measurement voltage node comprises a first measurement voltage node and a second measurement voltage node, the first load current node and the first measurement voltage node are disposed on the anode structure, and the second load current node and the second measurement voltage node are disposed on the cathode structure.
Preferably, the metal test structure includes a first test metal line and a second test metal line, and the first test metal line and the second test metal line have the same resistance value.
Preferably, the metal test structure further comprises a redundant metal strip disposed between the first test metal line and the second test metal line.
Preferably, the metal test structure is located in an upper metal layer of the metal connection structure.
Preferably, the metal test structure is located in a top metal layer.
Preferably, a through hole is further provided, and the metal connecting structure is electrically connected with the first test metal line through the through hole.
Preferably, a through hole is further provided, and the metal connecting structure is electrically connected with the second testing metal line through the through hole.
Preferably, the loading current node is electrically connected to the pad, and the measuring voltage node is electrically connected to the pad.
Preferably, the metal test structure further comprises an intermediate position node electrically connected to the pad for measuring a voltage.
The invention also provides a testing method based on the electromigration test structure, which comprises the following steps: electrically connecting a loading current node of the electromigration test structure with a bonding pad, and electrically connecting the voltage measurement node with the bonding pad; step two, a node is arranged at the middle position of the metal test structure and connected to the bonding pad; and step three, monitoring the resistance value change in real time in the testing process.
Preferably, the method further comprises a fourth step, and the test is finished until the final resistance value reaches 10% change.
Drawings
FIG. 1 is a schematic diagram of a prior art electromigration test structure.
FIG. 2 is a schematic diagram of an electromigration test structure according to the present invention.
FIG. 3 is a schematic diagram of an equivalent circuit of the electromigration test structure according to the present invention.
Description of the reference numerals
10 metal test structure 11 first test metal line
12 second test metal line 20 metal connection structure
21 first load current node 22 second load current node
23 first measured voltage node 24 second measured voltage node
25 middle node 30 via
40 lower metal layer 50 upper metal layer
60 redundant Metal strips
Detailed Description
The following detailed description of specific embodiments of the invention refers to the accompanying drawings. It is to be understood that the invention is not limited to the particular embodiments described above, in that devices and structures not described in detail are understood to be implemented in a manner common in the art; those skilled in the art can make many possible variations and modifications to the disclosed embodiments, or modify equivalent embodiments, without affecting the spirit of the invention, using the methods and techniques disclosed above, without departing from the scope of the invention.
Embodiment one electromigration test structure
The electromigration test structure of the present invention comprises a metal test structure 10 and a metal connection structure 20; the metal test structure 10 has a head end and a tail end, and the metal test structure comprises at least two metal test lines; the metal connection structure 20 is electrically connected to the head end and the tail end of the metal test structure 10 to connect metal test lines in the metal test structure in parallel, and is further provided with a loading current node and a measuring voltage node, wherein the loading current node is used for applying currents of the first test metal line and the second test metal line, and the measuring voltage node is used for measuring voltages of the first test metal line and the second test metal line after being connected in parallel.
In this embodiment, the metal test structure includes a first test metal line 11 and a second test metal line 12, and the resistance values of the first test metal line 11 and the second test metal line 12 are the same. Because two same test metal wires are connected in parallel, the resistance value of the circuit is reduced, and the detection of 10% change of the resistance value is easy. The failure judgment of the test system for each test sample is promoted, and the recommendation accuracy of the test life is promoted.
The metal connecting structure is provided with a cathode structure and an anode structure, one end of the metal connecting structure is electrically connected with the cathode structure, and the other end of the metal connecting structure is electrically connected with the anode structure.
The load current nodes include a first load current node 21 and a second load current node 22, the measurement voltage nodes include a first measurement voltage node 23 and a second measurement voltage node 24, the first load current node and the first measurement voltage node are disposed on the anode structure, and the second load current node and the second measurement voltage node are disposed on the cathode structure.
The first loading current node 21 and the second loading current node 22 are connected with a pad (pad) for loading (force) current; the first measurement voltage node 23 and the second measurement voltage node 24 are connected to a pad (pad) for measuring (sense) voltage.
The metal test structure further includes a redundant (dummy) metal strip 60 disposed between the first test metal line and the second test metal line. Because the metal distribution density is kept in a certain range, the key effect on the process preparation is realized, and the redundant (dummy) metal strip 60 is required to be used for filling when the metal density is less than the specified area, so that the metal distribution of the layer of the whole chip is relatively uniform.
The metal test structure is located in an upper metal layer of the metal connection structure. Preferably, the first metal layer is a top metal layer.
The electromigration test structure is also provided with a through hole 30, the metal connecting structure is electrically connected with the first test metal wire through the through hole 30, and the metal connecting structure is electrically connected with the second test metal wire through the through hole 30.
The metal test structure further comprises a mid-position node 25, the mid-position node 25 being electrically connected to the pad for measuring a voltage. Therefore, the resistance value change of the four equivalent circuits shown in the third part of the figure can be monitored in real time in the test process until the change of 10% is finally achieved, and the test is finished. The resistance of each part can be further analyzed to know where the cavity part causing the EM failure resistance variation is in the test structure, such as the cathode part or the anode part, to preliminarily judge the process problem and provide the FA analysis position.
Second embodiment test method based on electromigration test structure
And step one, electrically connecting a loading current node of the electromigration test structure with a bonding pad, and electrically connecting the measurement voltage node with the bonding pad. The electromigration test structure comprises: a metal test structure 10 and a metal connection structure 20; the metal test structure 10 has a head end and a tail end, and the metal test structure comprises at least two metal test lines; in this embodiment, the metal test structure includes a first test metal line 11 and a second test metal line 12, and the resistance values of the first test metal line 11 and the second test metal line 12 are the same. The metal connection structure 20 is electrically connected to the head end and the tail end of the metal test structure 10 to connect metal test lines in the metal test structure in parallel, and is further provided with a loading current node and a measuring voltage node, wherein the loading current node is used for applying currents of the first test metal line and the second test metal line, and the measuring voltage node is used for measuring voltages of the first test metal line and the second test metal line after being connected in parallel. The metal connecting structure is provided with a cathode structure and an anode structure, one end of the metal connecting structure is electrically connected with the cathode structure, and the other end of the metal connecting structure is electrically connected with the anode structure. The load current nodes include a first load current node 21 and a second load current node 22, the measurement voltage nodes include a first measurement voltage node 23 and a second measurement voltage node 24, the first load current node and the first measurement voltage node are disposed on the anode structure, and the second load current node and the second measurement voltage node are disposed on the cathode structure. The first loading current node 21 and the second loading current node 22 are connected with a pad (pad) for loading (force) current; the first and second measurement voltage nodes 23 and 24 are connected to a pad (pad) for measuring voltage. The metal test structure still includes redundant (dummy) metal strip, redundant metal strip sets up between first test metal line and the second test metal line. The metal test structure is located in an upper metal layer of the metal connection structure. Preferably, the first metal layer is a top metal layer.
The electromigration test structure is further provided with a through hole 30, the metal connecting structure 20 is electrically connected with the first test metal wire through the through hole 30, and the metal connecting structure is electrically connected with the second test metal wire through the through hole 30.
Because this test structure connects two the same test metal lines and through-hole in parallel, calculate according to parallel circuit's resistance:
r1 and R2 are the resistances of the first test metal line and the second test metal line on the parallel circuit, respectively, so that the total resistance after parallel connection is halved, and detection of a change in resistance of 10% becomes easy. Therefore, the failure time judgment of the test system on each test sample is improved, and the recommendation accuracy of the test life is improved.
Step two, a node is arranged at the middle position of the metal test structure and connected to the bonding pad;
two connecting wires are additionally arranged at the middle positions of the first testing metal wire and the second testing metal wire and are connected to a bonding pad (pad) for measuring (sense) voltage, so that the resistance value change of the four parts of equivalent circuits shown in the third part of the figure can be monitored in real time in the testing process until the resistance value change finally reaches 10%, and the testing is finished. The resistance of each part can be further analyzed to know where the cavity part causing the EM failure resistance variation is in the test structure, such as the cathode part or the anode part, to preliminarily judge the process problem and provide the FA analysis position.
And step three, monitoring the resistance value change in real time in the testing process.
And step four, until the final resistance value reaches 10% change, ending the test.
According to the design method of the electromigration EM test circuit, the circuit resistance is reduced by connecting two same test metal wires in parallel, and the detection resistance change of 10% is easy to detect. The failure judgment of the test system for each test sample is promoted, and the recommendation accuracy of the test life is promoted. The invention is suitable for new technical nodes of 28 nanometers and below.
While the preferred embodiments of the present invention have been described, it is to be understood that the invention is not limited to the precise embodiments disclosed herein, and that various changes and modifications may be effected therein without departing from the scope of the invention.
Claims (12)
1. An electromigration test structure, comprising:
a metal test structure having a head end and a tail end, the metal test structure comprising at least two metal test lines;
the metal connecting structure is electrically connected with the head end and the tail end of the metal testing structure so as to enable metal testing wires in the metal testing structure to be connected in parallel, the metal connecting structure is further provided with a loading current node and a measuring voltage node, the loading current node is used for applying current of the metal testing wires, and the measuring voltage node is used for measuring voltage after the metal testing wires are connected in parallel;
the metal test structure also includes an intermediate site node electrically connected to the pad for measuring a voltage.
2. The electromigration test structure of claim 1 wherein said metal interconnect structure is provided with a cathode structure and an anode structure, one end of said metal interconnect structure being electrically connected to said cathode structure and the other end of said metal interconnect structure being electrically connected to said anode structure.
3. The electromigration test structure of claim 2 wherein said load current node comprises a first load current node and a second load current node, and said measurement voltage node comprises a first measurement voltage node and a second measurement voltage node, said first load current node and first measurement voltage node being disposed on said anode structure, said second load current node and said second measurement voltage node being disposed on said cathode structure.
4. The electromigration test structure of claim 1 wherein said metal test structure comprises a first test metal line and a second test metal line, said first test metal line and said second test metal line having the same resistance value.
5. The electromigration test structure of claim 2, wherein said metal test structure further comprises a redundant metal strip, said redundant metal strip being disposed between said first test metal line and said second test metal line.
6. The electromigration test structure of claim 1 wherein said metal test structure is located in an upper metal layer of said metal connection structure.
7. The electromigration test structure of claim 1 wherein said metal test structure is located in a top metal layer.
8. The electromigration test structure of claim 1 further comprising a via, said metal connection structure being electrically connected to said first test metal line through said via.
9. The electromigration test structure of claim 1 further comprising a via, said metal connection structure being electrically connected to said second test metal line through said via.
10. The electromigration test structure of claim 1 wherein said load current node is electrically connected to a pad and said measure voltage node is electrically connected to a pad.
11. A method of testing based on an electromigration test structure as set forth in one of the claims 1 to 10, comprising the steps of:
electrically connecting a loading current node of the electromigration test structure with a bonding pad, and electrically connecting the voltage measurement node with the bonding pad;
step two, a node is arranged at the middle position of the metal test structure and connected to the bonding pad;
and step three, monitoring the resistance value change in real time in the testing process.
12. The method according to claim 11, further comprising a fourth step of ending the test until a final resistance value reaches 10% variation.
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| CN110620058B (en) * | 2019-09-23 | 2022-02-11 | 上海华力微电子有限公司 | Electromigration reliability test structure and electromigration reliability test method |
| CN112864131B (en) * | 2021-01-27 | 2024-04-16 | 武汉新芯集成电路制造有限公司 | Electromigration test structure and electromigration test method |
| CN113030685A (en) * | 2021-05-24 | 2021-06-25 | 晶芯成(北京)科技有限公司 | Semiconductor electromigration test circuit and test method |
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