Test structure and test method

Abstract

The application discloses a test structure and a test method. The test structure comprises a substrate, a plurality of test metal layers, a first test electrode, a second test electrode and a third test electrode. The plurality of test metal layers comprise interleaved serpentine metal lines and comb-shaped structures. The first and second test electrodes are connected to the first and second ends of each serpentine metal line respectively, and the third test electrode is connected to each comb-shaped structure. A first test branch is formed between the first and second test electrodes, a second test branch is formed between the first and third test electrodes, and a third test branch is formed between the second and third test electrodes. First and second preset resistors are connected in series between the first and second test electrodes and the first and second ends of each serpentine metal line respectively. The preset resistors in different first test branches have different resistances, the first preset resistors in different second test branches have different resistances, and the second preset resistors in different third test branches have different resistances. The test structure of the application can save area and test times.

Description

Technical Field

[0001] This invention relates to the field of electrical testing technology in the design and fabrication of integrated circuits, and specifically to a test structure and test method. Background Technology

[0002] The most typical characteristics of integrated circuit development include the shrinking feature size of front-end devices and the increasing complexity of back-end metal interconnects. Back-end metal interconnects mainly provide power or signal paths for the various ports of front-end devices, making back-end metal interconnect processes crucial.

[0003] To monitor the stability of downstream metal interconnect processes, in addition to controlling production process data, various electrical properties of the metal, such as sheet resistance, wire connectivity, and short circuits between wires, must also be monitored. Since the primary function of metal wiring is as interconnect, short circuits between adjacent wires caused by process abnormalities or open circuits caused by the breakage of thin wires are among the most critical electrical test items.

[0004] Existing test structures for short circuits and open circuits in the back-end metal lines follow the principle of layered, separate setups, meaning each metal layer corresponds to a set of test patterns. This approach is highly targeted and facilitates easy problem tracing, but it also has significant drawbacks. Because nanoscale integrated circuit manufacturing processes typically involve 6 to 10 or even more metal layers, following the above principle for test structures would occupy a large area of ​​the wafer's dicing traces and would require electrical testing for each test pattern, wasting testing resources.

[0005] Therefore, how to reduce the test structure's occupation of test resources, improve test efficiency, and promptly determine the location of defects are technical problems that need to be solved by those skilled in the art. Summary of the Invention

[0006] In view of the above problems, the purpose of the present invention is to provide a test structure and test method, which can save wafer area and test number by a factor of two.

[0007] To achieve the above objectives, a first aspect of the present invention provides a test structure comprising:

[0008] Substrate;

[0009] At least two test metal layers are located on the substrate, each test metal layer including interlaced serpentine metal lines and comb-like structures;

[0010] The first test electrode to the third test electrode are respectively connected to the first end of the serpentine metal line in each test metal layer, the second test electrode is respectively connected to the second end of the serpentine metal line in each test metal layer, and the third test electrode is connected to the comb-shaped structure in each test metal layer, so as to form at least two first test branches between the first test electrode and the second test electrode, at least two second test branches between the first test electrode and the third test electrode, and at least two third test branches between the second test electrode and the third test electrode.

[0011] Among them, a first preset resistor is connected in series between the first test electrode and the first end of the serpentine metal line of each test metal layer, and a second preset resistor is connected in series between the second test electrode and the second end of the serpentine metal line of each test metal layer; the sum of the resistance values ​​of the first preset resistor and the second preset resistor in different first test branches is different, the resistance value of the first preset resistor in different second test branches is different, and the resistance value of the second preset resistor in different third test branches is different.

[0012] Preferably, the first preset resistor and the second preset resistor in the same first test branch have the same resistance value.

[0013] Preferably, the third test electrode is located between the first test electrode and the second test electrode;

[0014] The serpentine metal wire comprises two connected segments, one segment located between the first test electrode and the third test electrode, and the other segment located between the second test electrode and the third test electrode.

[0015] Preferably, the aforementioned comb-like structure includes a first comb-like structure and a second comb-like structure, wherein the first comb-like structure and the second comb-like structure are respectively inserted into the serpentine metal wire from both sides.

[0016] Preferably, the comb-like structure includes a comb handle and a plurality of toothed metal strips connected to the comb handle, wherein the comb handle of the first comb-like structure and the comb handle of the second comb-like structure are connected at one end around the serpentine metal wire.

[0017] Preferably, each test metal layer further includes a first sub-test pad, a second sub-test pad, and a third sub-test pad, wherein the first sub-test pad is connected between the first preset resistor and the first test electrode, the second sub-test pad is connected between the second preset resistor and the second test electrode, and the third sub-test pad is connected between the third test electrode and the comb-shaped structure.

[0018] Preferably, both the first preset resistor and the second preset resistor are diffusion resistors and are located in the substrate.

[0019] Preferably, the first preset resistor and the second preset resistor are formed independently by at least one of the following implantation methods: well implantation, turn-on voltage modulation implantation, light doping implantation, and source / drain implantation.

[0020] A second aspect of the present invention is to provide a testing method employing the testing structure described in the first aspect, the testing method comprising the following steps:

[0021] The resistance between the first test electrode and the second test electrode is detected to obtain the first test resistance value; the resistance between the first test electrode and the third test electrode is detected to obtain the second test resistance value; the resistance between the second test electrode and the third test electrode is detected to obtain the third test resistance value.

[0022] Defects are identified and located based on the first to third test resistance values.

[0023] Preferably, the testing method further includes: establishing a judgment comparison table, which includes the mapping relationship between different combinations of the first test resistance value to the third test resistance value and the defect;

[0024] Based on the comparison results between the first to third test resistance values ​​and the judgment reference table, the defects are judged and located.

[0025] The test structure provided by this invention includes multiple test metal layers, each corresponding to a metal interconnect layer, and each test metal layer includes an integrated composite test unit for testing short circuits and open circuits. By connecting a pair of resistors in series between the test metal layers and the test electrodes, a one-to-one mapping relationship is established between various short circuit or open circuit abnormalities and the resistance values. Since the wafer area occupied by the test structure provided by this invention is comparable to that of existing single-layer test structures, the wafer area occupied by the test structure of this invention is reduced to 1 / (N-1) of that of existing test structures, where N is the total number of metal interconnect layers, thereby effectively saving wafer area occupied by the test structure.

[0026] In actual testing, compared to existing layered test structures that require testing layer by layer, the test structure of this invention only requires a single test to identify the abnormal test metal layer and determine the specific anomaly. In particular, by using the determination lookup table provided by this invention, it is possible to quickly pinpoint which test metal layer(s) or which test metal layers the short-circuit or open-circuit problem occurs in, and it can also determine the relative positions of short-circuit and open-circuit anomalies within the same test metal layer. Therefore, compared to existing test structures and methods, the test structure and method of this invention can significantly reduce the number of tests, substantially improve test efficiency, and the obtained test results can provide important clues for subsequent failure analysis and localization. Attached Figure Description

[0027] The above and other objects, features, and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings. Furthermore, for clarity, the various parts in the drawings are not drawn to scale.

[0028] Figure 1 A top view of the existing layered test structure;

[0029] Figure 2 This is a three-dimensional schematic diagram of the test structure according to the first embodiment of the present invention;

[0030] Figure 3a This is a schematic diagram of the equivalent circuit of the test structure according to the first embodiment of the present invention;

[0031] Figure 3b This is a flowchart illustrating the testing method of the first embodiment of the present invention;

[0032] Figure 3c This is a judgment comparison table for the test structure of the first embodiment of the present invention;

[0033] Figure 4 This is a three-dimensional schematic diagram of the test structure according to the second embodiment of the present invention;

[0034] Figure 5a This is a schematic diagram of the equivalent circuit of the test structure according to the second embodiment of the present invention;

[0035] Figure 5b This is the first judgment comparison table for the test structure of the second embodiment of the present invention;

[0036] Figure 6a This is a schematic diagram of the equivalent circuit of the test structure in the second embodiment of the present invention when a short circuit anomaly occurs.

[0037] Figure 6b This is the second judgment comparison table for the test structure of the second embodiment of the present invention;

[0038] Figure 7a This is a schematic diagram of the equivalent circuit of the test structure in the second embodiment of the present invention when an open-circuit anomaly occurs.

[0039] Figure 7b Table 3 shows the determination comparison table for the test structure of the second embodiment of the present invention;

[0040] Figure 8a This is a schematic diagram of the equivalent circuit of the test structure of the second embodiment of the present invention, which simultaneously exhibits short-circuit and open-circuit anomalies.

[0041] Figure 8b Table 4 shows the determination comparison table for the test structure of the second embodiment of the present invention. Detailed Implementation

[0042] Various embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. However, the present invention is not limited to these embodiments. In the following detailed description of the invention, certain specific details are described in detail. Those skilled in the art will fully understand the invention even without these detailed descriptions. To avoid obscuring the essence of the invention, well-known methods, processes, and procedures are not described in detail.

[0043] As mentioned above, existing test structures for short circuits and open circuits in the back-end metal mostly follow the principle of layered setup, that is, in addition to the top metal layer, a set of test patterns is set for each metal interconnect layer. Figure 1 A top view of the existing layered test structure, such as Figure 1 As shown, the existing test structure includes a first sub-test pad 111, a second sub-test pad 121, and a third sub-test pad 131. According to general design rules, the distance between any two adjacent sub-test pads is the same. The first sub-test pad 111 and the second sub-test pad 121 are connected by a serpentine metal wire 160, thus forming a test unit capable of detecting open circuits. The third sub-test pad 131 is connected, for example, to a comb-like structure. Specifically, the comb-like structure includes, for example, a first comb-like structure 170 and a second comb-like structure 180 arranged opposite each other. The two comb-like structures are respectively interspersed with the serpentine metal wire 160 from both sides, forming a test unit capable of detecting short circuits.

[0044] The first comb-shaped structure 170 is similar to the second comb-shaped structure 180. Taking the first comb-shaped structure 170 as an example, the first comb-shaped structure 170 includes a comb handle 171 and multiple toothed metal strips 172. One end of each of the multiple toothed metal strips 172 is connected to the comb handle 171 on the same side. The comb handle 171 passes around the second sub-test pad 121 and is connected to the comb handle of the second comb-shaped structure 180 to achieve same-layer connection. Of course, the first comb-shaped structure 170 can also pass around the first sub-test pad 111 and be connected to the second comb-shaped structure 180.

[0045] Specifically, in Figure 1 In this design, the serpentine metal wire 160 is divided into two connected segments, which are connected by a layer of metal wire. A third sub-test pad 131 is located between the two segments of the serpentine metal wire 160, and also between the first sub-test pad 111 and the second sub-test pad 121. The third sub-test pad 131 is connected to the comb handle 171 of the first comb-like structure 170. Alternatively, the third sub-test pad 131 can be positioned in other locations, such as to the right of the second test pad 121, connected to the comb-like structure.

[0046] Figure 1In the existing test structure shown, a dielectric layer (not shown in the figure) is provided between all the toothed metal strips and between the toothed metal strips and the serpentine metal wire, which insulates and separates the adjacent conductive structures.

[0047] This test structure is actually a composite test unit that can be used to detect short circuit and open circuit conditions. During the test, a first voltage can be applied between the first sub-test pad 111 and the second sub-test pad 121, a second voltage can be applied between the first sub-test pad 111 and the third sub-test pad 131, and a third voltage can be applied between the second sub-test pad 121 and the third sub-test pad 131. By detecting whether there is a path between each pair of the first sub-test pad 111, the second sub-test pad 121, and the third sub-test pad 131, feedback can be given on whether the manufacturing process of the metal interconnect layer corresponding to the test structure is normal.

[0048] Under normal circumstances, there should be a conductive path between the first sub-test pad 111 and the second sub-test pad 121, meaning current should flow through them. Conversely, there should be no conductive path between the first sub-test pad 111 and the third sub-test pad 131, and no conductive path should exist between the second sub-test pad 121 and the third sub-test pad 131, meaning no current should flow through them. If the actual test results differ from the above, it indicates a defect in the test structure, suggesting a potential problem with the manufacturing process of the corresponding metal interconnect layer.

[0049] It's easy to understand that the length of the serpentine metal line, and the number and length of the toothed metal strips in the comb-like structure, are positively correlated with the sensitivity of the test structure to open and short circuit anomalies in the metal interconnects. Given the allowable dicing width and test pad spacing, the longer the serpentine metal line and the more teeth in the comb-like structure, the greater the probability of capturing short / open circuit defects. To further increase the sensitivity of the test unit, the width of the toothed metal strips, the spacing between adjacent toothed metal strips, and the spacing between the toothed metal strips and the serpentine metal line should be selected to the minimum values ​​that satisfy the physical design rules of the corresponding process platform. Because this test structure is formed synchronously with the same layer of metal interconnects in the device area, when an open / short circuit occurs in this test structure, it indicates that a similar defect has likely occurred in the manufacturing process of the corresponding metal interconnect layer in the wafer. This allows feedback on the stability and normality of the manufacturing process of the metal interconnect layer in the device area, enabling timely detection of problems and reducing the generation of defective products.

[0050] As explained above, to monitor the downstream metal interconnect process, existing technologies require a separate test unit for each metal interconnect layer. Generally, the top layer metal lines are thicker and have larger spacing, so no monitoring pattern is needed. Therefore, a total of N-1 test units are required for the downstream process. Figure 1The test structure shown is N, where N is the total number of metal interconnect layers. Assuming each test structure occupies a wafer area of ​​S, the total wafer area occupied by all test structures is S × (N-1). Furthermore, each test structure needs to be tested individually, requiring N-1 tests. Therefore, using the existing test structure requires a large amount of wafer area and has low testing efficiency. Optimizing the test structure to reduce the wafer area occupied and improve testing efficiency while ensuring the accuracy of the test results is a crucial step in integrated circuit design and manufacturing.

[0051] Figure 2 This is a three-dimensional structural diagram of the test structure according to the first embodiment of the present invention; as shown. Figure 2 As shown, the test structure includes a substrate 100, two test metal layers M1 and M2 located above the substrate 100, and a first test electrode 110, a second test electrode 120, and a third test electrode 130 located above the test metal layers. Both test metal layers M1 and M2 include serpentine metal lines, comb-like structures, and three sub-test pads. The specific structure and electrical connections of test metal layers M1 and M2 can be found in [reference needed]. Figure 1 The content regarding the existing test structure mentioned earlier will not be repeated here. And for clarity, Figure 2 The dielectric layers between test metal layers M1 and M2, between test metal layer M1 and substrate 100, and between test metal layer M2 and test electrode are omitted.

[0052] Four parallel and isolated resistors are formed in the substrate 100. These four resistors are, for example, diffusion resistors, formed by ion implantation in the substrate. Among these four resistors, resistors 141 and 142 are collectively referred to as the first preset resistor 140, located between the first test electrode 110 and the third test electrode 130. Resistor 141 is connected in series between the first test electrode 110 and the first end of the serpentine metal line in the test metal layer M1, and resistor 142 is connected in series between the first test electrode 110 and the first end of the serpentine metal line in the test metal layer M2. Resistors 151 and 152 are collectively referred to as the second preset resistor 150, located between the third test electrode 130 and the second test electrode 120. Resistor 151 is connected in series between the second test electrode 120 and the second end of the serpentine metal line in the test metal layer M1, and resistor 152 is connected in series between the second test electrode 120 and the second end of the serpentine metal line in the test metal layer M2.

[0053] The test structure of the first embodiment includes two test metal layers, corresponding to two parallel first test branches located between the first test electrode 110 and the second test electrode 120, two parallel second test branches located between the first test electrode 110 and the third test electrode 130, and two parallel third test branches located between the second test electrode 120 and the third test electrode 130. One of the first test branches includes a serpentine metal wire in the test metal layer M1 and resistors 141 and 151 connected to both ends of the serpentine metal wire; the other first test branch includes a serpentine metal wire in the test metal layer M2 and resistors 142 and 152 connected to both ends of the serpentine metal wire. One second test branch includes a comb-shaped structure and a serpentine metal line interspersed between the first test electrode 110 and the third test electrode 130 in the test metal layer M1, and a resistor 141; the other second test branch includes a comb-shaped structure and a serpentine metal line interspersed between the first test electrode 110 and the third test electrode 130 in the test metal layer M2, and a resistor 142. One third test branch includes a comb-shaped structure and a serpentine metal line interspersed between the second test electrode 120 and the third test electrode 130 in the test metal layer M1, and a resistor 151; the other third test branch includes a comb-shaped structure and a serpentine metal line interspersed between the second test electrode 120 and the third test electrode 130 in the test metal layer M2, and a resistor 152.

[0054] In the above test structure, the resistance values ​​of the first preset resistor 140 in different test metal layers are different, that is, the resistance values ​​of resistor 141 and resistor 142 are different; the resistance values ​​of the second preset resistor 150 in different test metal layers are different, that is, the resistance values ​​of resistor 151 and resistor 152 are different. Furthermore, the sum of the resistance values ​​of the first preset resistor and the second preset resistor connected in series in different test metal layers is different, that is, the sum of the resistance values ​​of resistor 141 and resistor 151 is different from the sum of the resistance values ​​of resistor 142 and resistor 152.

[0055] The resistance values ​​of the four resistors mentioned above can, in principle, be different for each other. 。 However, in actual operation, in order to simplify the judgment process, preferably, the resistors connected in series at both ends of the same test metal layer have the same resistance value, that is, the two resistors in the same first test branch have the same resistance value; that is, in the preferred embodiment of this example, the resistance values ​​of resistor 141 and resistor 151 are the same, and the resistance values ​​of resistor 142 and resistor 152 are the same, which can also realize the setting of an inherent mapping relationship between a specific resistance value and a specific test metal layer.

[0056] The aforementioned first preset resistor 140 and second preset resistor 150 can both be implemented using ion implantation processes in existing integrated circuit manufacturing processes. Alternatively, under the same ion implantation process, the resistance value can be adjusted by changing the length and / or width of the resistor. Specifically, the resistors can be formed using methods including N / P-type well implantation, voltage modulation (Vt) implantation, lightly doped drain (LDD) implantation, and source / drain implantation. Their resistance value can also be adjusted by whether or not silicide is applied. Of course, the formation methods of each resistor can be the same or different; this embodiment does not impose any particular limitation. It is easy to understand that, in order to increase the sensitivity and resolution of the test structure to various abnormal conditions, within the measurable range, the greater the difference in resistance values ​​between resistors connected in series with different test metal layers, the better.

[0057] Further reference Figure 2 The test metal layer M1 also includes a first sub-test pad 111, a second sub-test pad 121, and a third sub-test pad 131. One end of the serpentine metal wire in the test metal layer M1 is connected to one end of a resistor 141 via a longitudinal metal plug, and the other end of the resistor 141 is connected to the first sub-test pad 111 via a longitudinal metal plug. Similarly, the other end of the serpentine metal wire in the test metal layer M1 is connected to one end of a resistor 151 via a longitudinal metal plug, and the other end of the resistor 151 is connected to the second sub-test pad 121 via a longitudinal metal plug. The comb handle of the comb-like structure in the test metal layer M1 is connected to the third sub-test pad 131.

[0058] The test metal layer M2 also includes a first sub-test pad 112, a second sub-test pad 122, and a third sub-test pad 132. One end of the serpentine metal wire in the test metal layer M2 is connected to one end of a resistor 142 via a longitudinal metal plug, and the other end of the resistor 142 is connected to the first sub-test pad 112 via a longitudinal metal plug. The other end of the serpentine metal wire in the test metal layer M2 is connected to one end of a resistor 152 via a longitudinal metal plug, and the other end of the resistor 152 is connected to the second sub-test pad 122 via a longitudinal metal plug. The comb-like structure in the test metal layer M2 is connected to the third sub-test pad 132.

[0059] The first sub-test pads 111 and 112 are connected to the first test electrode 110 of the top layer via longitudinal metal plugs. The second sub-test pads 121 and 122 are connected to the second test electrode 120 of the top layer via longitudinal metal plugs. The third sub-test pads 131 and 132 are connected to the third test electrode 130 of the top layer via longitudinal metal plugs.

[0060] Of course, although Figure 2The example shown only has two test metal layers, and a resistor is connected in series at each end of the serpentine metal line. Based on the design of this example, the resistor at one end of the serpentine metal line can also be omitted, or more test metal layers can be set, and more preset resistors can be set accordingly.

[0061] Although the above describes a specific test unit and the test units in each test metal layer are arranged in the same direction, other common test units of other shapes can also be set according to actual needs, and the test units in each of the above test metal layers can also be different.

[0062] The directions of the test units in different test metal layers can also be perpendicular to each other or at a certain angle. That is, the connection relationship of the test units in each test metal layer remains unchanged, but the arrangement direction can be perpendicular to each other. Specifically, the test units in adjacent test metal layers are perpendicular to each other, which means that the extension direction of the serpentine metal line in test metal layer M2 is perpendicular to the extension direction of the serpentine metal line in test metal layer M1. Correspondingly, the directions of the multiple toothed metal strips of the comb-like structure in test metal layers M1 and M2 are also perpendicular to each other.

[0063] Figure 3a This is a schematic diagram of the equivalent circuit of the test structure in the first embodiment of the present invention. In order to make the subsequent defect analysis more concise, resistors 141 and 151 are both set as resistors R1, and resistors 142 and 152 are both set as resistors R2. The resistance values ​​of resistors R1 and R2 are different, and the comb-like structure on both sides of the serpentine metal wire is simplified to a single-sided form for illustration.

[0064] from Figure 3a As can be seen in the figure, one end of the serpentine metal wire in the test metal layer M1 is connected to the first test electrode 110 through a resistor R1 on one side, and the other end is connected to the second test electrode 120 through a resistor R1 on the other side. The comb-shaped structure in the test metal layer M1 is connected to the third test electrode 130. One end of the serpentine metal wire in the test metal layer M2 is connected to the first test electrode 110 through a resistor R2 on one side, and the other end is connected to the second test electrode 120 through a resistor R2 on the other side. The comb-shaped structure in the test metal layer M2 is connected to the third test electrode 130.

[0065] Figure 3b This is a flowchart illustrating the testing method of the first embodiment of the present invention, which includes the following steps:

[0066] In step S10, the resistance between the first test electrode 110 and the second test electrode 120 is detected to obtain a first test resistance value Rx; the resistance between the first test electrode 110 and the third test electrode 130 is detected to obtain a second test resistance value Ry; and the resistance between the second test electrode 120 and the third test electrode 130 is detected to obtain a third test resistance value Rz. Specifically, a first voltage can be applied between the first test electrode 110 and the second test electrode 120, a second voltage can be applied between the first test electrode 110 and the third test electrode 130, and a third voltage can be applied between the first test electrode 110 and the third test electrode 130. By detecting the current between each test electrode, the first test resistance value Rx, the second test resistance value Ry, and the third test resistance value Rz can be obtained. This embodiment does not particularly limit the values ​​of the first, second, and third voltages, as long as it is ensured that the obtained Rx, Ry, and Rz do not adversely affect the defect determination result.

[0067] In step S20, defects are determined and located based on the first test resistance value Rx, the second test resistance value Ry, and the third test resistance value Rz. Specifically, based on the test structure of the first embodiment, the first test resistance value Rx, the second test resistance value Ry, and the third test resistance value Rz corresponding to different situations can be obtained through its equivalent circuit diagram. Based on the mapping relationship between different combinations and defects, a judgment comparison table can be drawn. During detection and analysis, the actual detected Rx, Ry, and Rz values ​​are compared with the values ​​in the judgment comparison table to determine the defects in each test metal layer. In some cases, the relative positional relationship between short-circuit defects and open-circuit defects in the same test metal layer can also be determined.

[0068] Figure 3c A judgment comparison table of the test structure of the first embodiment of the present invention is shown. For example... Figure 3c As shown in scenarios 1-4, when neither of the serpentine metal lines in test metal layers M1 and M2 is open-circuited, the resistance values ​​of the two first test branches are approximately 2R1 and 2R2, respectively. Since the two first test branches are connected in parallel, the first test resistance value Rx = 1 / 2R1 + 1 / 2R2 is obtained. In scenario 1, if the serpentine metal lines in test metal layers M1 and M2 are not short-circuited with the comb-like structure, the two second test branches and the two third test branches are open-circuited, so the measured second test resistance value Ry and the third test resistance value Rz are both infinite. In scenario 2, if only the serpentine metal lines in test metal layer M1 are short-circuited with the comb-like structure, the second test branch corresponding to test metal layer M1 is conductive, and the resistance value of this second test branch is approximately R1. The resistance value of the second test branch corresponding to test metal layer M2 is still infinite, thus the second test resistance value Ry is R1.

[0069] The analysis process for other scenarios will not be elaborated here. Without considering the simultaneous occurrence of multiple short circuits and open circuits in the same test metal layer (i.e., at most one short circuit point and at most one open circuit point in the same test metal layer), the situation of each test metal layer and each metal interconnect layer in the device area can be determined by comparing against this judgment table. Of course, if two or more short circuit points and / or two or more open circuit points appear in the same test metal layer, the relevant abnormal situations and the specific details of the corresponding first, second, and third current values ​​can be further expanded based on this judgment table.

[0070] Figure 4 This is a three-dimensional schematic diagram of the test structure according to the second embodiment of the present invention. The second embodiment is similar to the first embodiment, except that the test structure of the second embodiment has three test metal layers, M1, M2, and M3. Correspondingly, the first sub-test pads 111, 112, and 113 in the three test metal layers are all connected to the first test electrode 110 of the top layer, the second sub-test pads 121, 122, and 123 in the three test metal layers are all connected to the second test electrode 120 of the top layer, and the third sub-test pads 131, 132, and 133 in the three test metal layers are all connected to the third test electrode 130 of the top layer. Six resistors are provided in the substrate 100, namely resistors 141-143 and resistors 151-153, wherein resistors 141-143 are collectively referred to as the first preset resistors 140, and resistors 151-153 are collectively referred to as the second preset resistors 150. Furthermore, the resistance values ​​of the three resistors 141-143 of the first preset resistor 140 are all different, and the resistance values ​​of the three resistors 151-153 of the second preset resistor 150 are also different. The sum of the resistance values ​​of the first preset resistor 140 and the second preset resistor 150 connected in series across different test metal layers is different. Preferably, the resistance values ​​of the resistors connected in series with the same test metal layer are all the same, that is, the resistance values ​​of resistors 141 and 151 are the same, the resistance values ​​of resistors 142 and 152 are the same, and the resistance values ​​of resistors 143 and 153 are the same.

[0071] Figure 5a This is a schematic diagram of the equivalent circuit of the test structure in the second embodiment of the present invention. To make the subsequent defect analysis simpler, resistors 141 and 151 are both set as resistors R1, resistors 142 and 152 are both set as resistors R2, resistors 143 and 153 are both set as resistors R3, and the comb-like structure on both sides of the serpentine metal wire is simplified to a single-sided form for illustration.

[0072] Since the test structure of the second embodiment includes three test metal layers, there are many corresponding abnormal situations. A complete judgment comparison table would be too lengthy. Therefore, some situations are selected for explanation and detail. Figure 5b, Figure 6b , Figure 7b and Figure 8b These are portions of the complete judgment comparison table.

[0073] according to Figure 5a The equivalent circuit diagram shows that when all test metal layers are normal, i.e., test metal layers M1, M2, and M3 are free from short circuits and open circuits, the first test electrode 110 and the second test electrode 120 are equivalent to three resistors 2R1, 2R2, and 2R3 connected in parallel in the circuit. There is no bridging (short circuit) between the three comb-shaped structures and the serpentine metal wires. There are no conductive loops between the first test electrode 110 and the third test electrode 130, or between the second test electrode 120 and the third test electrode 130. Since the resistivity of a typical metal resistor is on the order of mΩ / square, the resistance of the metal wires in the equivalent circuit can be ignored.

[0074] A first voltage is applied between the first test electrode 110 and the second test electrode 120. At this time, the resistance values ​​of the three first test branches are 2R1, 2R2, and 2R3, respectively, and the three first test branches are connected in parallel. Therefore, the first test resistance value Rx of the circuit is approximately:

[0075]

[0076] A second voltage is applied between the first test electrode 110 and the third test electrode 130, creating a third voltage between the second test electrode 120 and the third test electrode 130. At this time, the resistance values ​​of the three second test branches and the three third test branches are all infinite. Therefore, the second test resistance Ry and the third test resistance Rz are both infinite. Specifically, as follows... Figure 5b As shown.

[0077] Figure 6a This is an equivalent circuit diagram of the test structure of the second embodiment of the present invention where only a short-circuit anomaly occurs; specifically, for example, both test metal layer M1 and test metal layer M2 are short-circuited simultaneously, without an open-circuit anomaly (corresponding to...). Figure 6b In scenario 4), a first voltage is applied between the first test electrode 110 and the second test electrode 120, and a second voltage is applied between the first test electrode 110 and the third test electrode 130, resulting in a third voltage between the second test electrode 120 and the third test electrode 130. At this time, the first test resistance Rx is... Figure 5b The same applies as shown; due to the short circuit between test metal layers M1 and M2, when detecting the second test resistance value Ry and the third test resistance value Rz, their equivalent circuits are equivalent to resistors R1 and R2 connected in parallel in the circuit. At this time, the second test resistance value Ry is:

[0078]

[0079] Similarly, the third test resistance value Rz is:

[0080]

[0081] Similarly, when only a short-circuit anomaly is detected in the tested metal layer, it can be handled according to... Figure 6b The judgment comparison table shown in Part 2 determines the specific short-circuit anomaly, or in other words, it is based on the test results and references... Figure 6b This allows for a quick determination of the actual short circuit situation and an inference of whether a similar anomaly has occurred in the corresponding metal interconnect layer of the device area.

[0082] Figure 7a This is an equivalent circuit diagram of the test structure of the second embodiment of the present invention where only an open-circuit anomaly occurs; specifically, for example, both test metal layer M1 and test metal layer M2 are simultaneously open-circuited (corresponding to...). Figure 7b In scenario 4), among the three first test branches between the first test electrode 110 and the second test electrode 120, the resistance values ​​of the two first test branches corresponding to test metal layers M1 and M2 are considered infinite, and the resistance value of the other first test branch corresponding to test metal layer M3 is 2R3. This is equivalent to only two resistors R3 connected in series in the circuit, i.e., the resistance value of the first test resistor Rx = 2R3; while the test resistance values ​​between the first test electrode 110 and the third test electrode 130, and between the second test electrode 120 and the third test electrode 130, are both infinite, i.e., Ry = ∞, Rz = ∞. Similarly, when there is only an open circuit abnormality, it can be determined according to... Figure 7b The judgment comparison table shown in Table 3 and the test results can determine the actual situation of an open circuit and infer whether a similar anomaly has occurred in the metal layer of the device area.

[0083] Figure 8a This is a schematic diagram of the equivalent circuit when the test structure of the second embodiment of the present invention simultaneously exhibits short-circuit and open-circuit anomalies. Specifically, test metal layer M1 exhibits both short-circuit and open-circuit anomalies simultaneously, and test metal layer M2 also exhibits both short-circuit and open-circuit anomalies simultaneously. Analyzing such cases also requires considering the relative positions of the short-circuit and open-circuit anomalies within the same layer in the test structure, for example... Figure 8aIn the equivalent circuit diagram shown, the short-circuit point in test metal layer M1 is located to the left of the open-circuit point. Due to the open-circuit anomaly, neither resistor R1 is connected to the circuit between the first test electrode 110 and the second test electrode 120. Because of the short-circuit anomaly and the short-circuit point being located to the left of the open-circuit point, when a second voltage is applied between the first test electrode 110 and the third test electrode 130, the left-hand resistor R1 is connected in parallel to the circuit between the first test electrode 110 and the third test electrode 130. However, between the second test electrode 120 and the third test electrode 130, neither of the two resistors R1 can be connected to the circuit. The anomaly situation of test metal layer M2 is similar to that of test metal layer M1, only the relative positions of the open-circuit point and the short-circuit point are different. In this case, the first test resistance value Rx, the second test resistance value Ry, and the third test resistance value Rz are as follows:

[0084] Rx=2R3; Ry=R1; Rz=R2.

[0085] Similarly, in cases where both short circuits and open circuits occur simultaneously in the same test metal layer, the following can be used as a basis for determining the cause: Figure 8b The judgment comparison table shown in section four identifies the specific circumstances of the anomalies. In particular, based on this test structure, not only can the corresponding test resistance values ​​be given under different abnormal conditions, but the relative positions of short-circuit and open-circuit anomalies can also be qualitatively given, which is very helpful for failure analysis and localization.

[0086] The above embodiments do not consider the situation where multiple short-circuit and open-circuit points occur simultaneously in the same test metal layer. Furthermore, although the aforementioned judgment comparison tables only show some abnormal situations, a complete judgment comparison table can be obtained by analogy based on the above embodiments. During actual testing, the test resistance value can be directly compared with the complete judgment comparison table to obtain the short-circuit and open-circuit abnormalities of each test metal layer. Based on this, it can be determined whether an abnormality has occurred in the corresponding metal interconnect layer (or metal wiring layer) of the device area and to infer the specific location of the abnormality. In addition, when short-circuit and open-circuit abnormalities occur simultaneously in the test unit, the test structure provided by this invention can also provide the relative positions of the short-circuit and open-circuit abnormal points. This positional information is of great guiding significance for subsequent failure analysis.

[0087] The test structure provided by this invention includes multiple test metal layers, each corresponding to a metal interconnect layer, and each test metal layer includes short-circuit and open-circuit test units as found in conventional layered test structures. By connecting a pair of resistors in series between the test unit and the test electrode, a one-to-one mapping relationship is established between various short-circuit or open-circuit abnormalities and the resistance values. Compared with the prior art, the wafer area occupied by the test structure of this invention is comparable to that of a conventional single-layered test structure, and the area occupied by the test structure is reduced to 1 / (N-1) of the total area of ​​conventional layered test structures, where N is the total number of metal interconnect layers, thereby effectively saving wafer area occupied by the test structure.

[0088] In actual testing, existing layered test structures require testing layer by layer, resulting in N-1 test runs. In contrast, the test structure of this invention requires only one test to determine and accurately locate the anomaly. Specifically, the judgment table provided by this invention quickly pinpoints which test metal layers or layers contain short circuits or open circuits, and also qualitatively determines the relative positions of short circuits and open circuits within the same test metal layer. Therefore, compared to existing methods, this testing method significantly reduces the number of tests, greatly improves testing efficiency, and provides crucial clues for subsequent failure analysis and localization.

[0089] It should be noted that in the description of this invention, terms such as "first" and "second" are used only to facilitate the description of different orientations, parts, components, and components, and should not be construed as indicating or implying sequential relationships, relative importance, or implicitly indicating the number of technical features indicated.

[0090] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can be modified and varied in various ways. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of protection of the present invention.

Claims

1. A test structure, characterized in that, include: Substrate; At least two test metal layers are located on the substrate, each test metal layer including interlaced serpentine metal lines and comb-like structures; The first test electrode to the third test electrode are respectively connected to the first end of the serpentine metal line in each test metal layer, the second test electrode is respectively connected to the second end of the serpentine metal line in each test metal layer, and the third test electrode is connected to the comb-shaped structure in each test metal layer, so as to form at least two first test branches between the first test electrode and the second test electrode, at least two second test branches between the first test electrode and the third test electrode, and at least two third test branches between the second test electrode and the third test electrode. Among them, a first preset resistor is connected in series between the first test electrode and the first end of the serpentine metal line of each test metal layer, and a second preset resistor is connected in series between the second test electrode and the second end of the serpentine metal line of each test metal layer; the sum of the resistance values ​​of the first preset resistor and the second preset resistor in different first test branches is different, the resistance value of the first preset resistor in different second test branches is different, and the resistance value of the second preset resistor in different third test branches is different.

2. The test structure according to claim 1, characterized in that, The first preset resistor and the second preset resistor in the same first test branch have the same resistance value.

3. The test structure according to claim 1 or 2, characterized in that, The third test electrode is located between the first test electrode and the second test electrode; The serpentine metal wire comprises two connected segments, one segment located between the first test electrode and the third test electrode, and the other segment located between the second test electrode and the third test electrode.

4. The test structure according to claim 3, characterized in that, The comb-like structure includes a first comb-like structure and a second comb-like structure, wherein the first comb-like structure and the second comb-like structure are respectively inserted into the serpentine metal wire from both sides.

5. The test structure according to claim 4, characterized in that, The comb-like structure includes a comb handle and a plurality of toothed metal strips connected to the comb handle. The comb handles of the first comb-like structure and the comb handles of the second comb-like structure are connected at one end around the serpentine metal wire.

6. The test structure according to claim 1 or 2, characterized in that, Each of the test metal layers further includes a first sub-test pad, a second sub-test pad, and a third sub-test pad, wherein the first sub-test pad is connected between the first preset resistor and the first test electrode, the second sub-test pad is connected between the second preset resistor and the second test electrode, and the third sub-test pad is connected between the third test electrode and the comb-shaped structure.

7. The test structure according to claim 1 or 2, characterized in that, Both the first preset resistor and the second preset resistor are diffusion resistors and are located in the substrate.

8. The test structure according to claim 7, characterized in that, The first preset resistor and the second preset resistor are formed independently by at least one of the following implantation methods: well implantation, voltage modulation implantation, light doping implantation, and source / drain implantation.

9. A testing method, characterized in that, The test method, employing the test structure as described in any one of claims 1-8, comprises the following steps: The resistance between the first test electrode and the second test electrode is detected to obtain the first test resistance value; the resistance between the first test electrode and the third test electrode is detected to obtain the second test resistance value; the resistance between the second test electrode and the third test electrode is detected to obtain the third test resistance value. Based on the first test resistance value, the second test resistance value, and the third test resistance value, the defect is determined and located.

10. The test method according to claim 9, characterized in that, Also includes: Establish a judgment comparison table, which includes the mapping relationship between different combinations of the first test resistance value to the third test resistance value and the defect; Based on the comparison results between the first to third test resistance values ​​and the judgment reference table, the defects are judged and located.

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