Test Method

Abstract

The embodiment of the present application relates to the field of semiconductor, and provides a test method, at least comprising: providing a conductive substrate and a plurality of discrete contact structures to be tested, the bottom end of the contact structure to be tested is in contact with the conductive substrate, and the second contact structure and the third contact structure are located at different sides of the first contact structure; providing a first excitation probe to be in electrical contact with the top end of the first contact structure, and providing a second excitation probe to be in electrical contact with the top end of the second contact structure; providing a first detection probe to be in electrical contact with the top end of the first contact structure, and providing a second detection probe to be in electrical contact with the top end of the third contact structure; providing an excitation current flowing through the first contact structure and the second contact structure; and acquiring the contact resistance of the first contact structure and the conductive substrate according to the voltage difference of the first detection probe and the second detection probe and the value of the excitation current. The embodiment of the present application is beneficial to accurately measuring the contact resistance.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the field of semiconductor, and in particular, to a test method. BACKGROUND

[0002] In the manufacturing process of integrated circuit chips, the performance of the finished wafer or semi-finished wafer needs to be tested and verified. The wafer performance includes the path resistance of the conductive path, which is composed of the resistance of different conductive structures and the contact resistance between different conductive structures. In the past experience, it is often believed that the resistance of the conductive structure itself is much larger than the contact resistance, so that the calculation of the path resistance often ignores the contact resistance, which leads to low accuracy of the finally calculated path resistance.

[0003] In addition, when testing the performance of the wafer by using a nano-probe station, the use of the probe will also introduce a new contact resistance. If the accuracy requirement of the resistance measurement result is high, the influence of the contact resistance introduced by the probe also needs to be excluded. SUMMARY

[0004] Embodiments of the present application provide a test method, which is at least beneficial to accurately measuring the contact resistance.

[0005] According to some embodiments of the present application, a test method is provided, which can at least include: providing a conductive substrate and a plurality of discrete contact structures to be tested, the bottom end of the contact structure to be tested being in contact with the conductive substrate, the contact structure to be tested including a first contact structure, a second contact structure and a third contact structure, the second contact structure and the third contact structure being located on different sides of the first contact structure; providing a first excitation probe and a second excitation probe, the first excitation probe being in electrical contact with the top end of the first contact structure, and the second excitation probe being in electrical contact with the top end of the second contact structure; providing a first detection probe and a second detection probe, the first detection probe being in electrical contact with the top end of the first contact structure, and the second detection probe being in electrical contact with the top end of the third contact structure; providing an excitation current through the first excitation probe and the second excitation probe, the excitation current flowing through the first contact structure and the second contact structure to form a current loop, and the first detection probe and the second detection probe forming a voltage loop; and obtaining the contact resistance between the first contact structure and the conductive substrate according to the voltage difference between the first detection probe and the second detection probe and the value of the excitation current.

[0006] In some embodiments, the current loop is formed by applying the excitation current to the first contact structure through the first excitation probe, and controlling the top end voltage of the second contact structure to be lower than the top end voltage of the first contact structure through the second excitation probe, so that the excitation current flows to the top end of the second contact structure through the conductive substrate.

[0007] In some embodiments, the second contact structure and the third contact structure are located on opposite sides of the first contact structure.

[0008] In some embodiments, the material of the contact structure under test is different from the material of the conductive substrate.

[0009] In some embodiments, the cross-section of the contact structure under test is rectangular in the direction of the excitation current flow.

[0010] In some embodiments, the process steps of providing the conductive substrate and the contact structure under test include: providing a conductive substrate, a first passivation layer and a second passivation layer stacked sequentially, wherein the contact structure under test is located within the first passivation layer and penetrates the first passivation layer and is in contact with the conductive substrate, and the second passivation layer covers the top surface of the contact structure under test; and removing at least a portion of the second passivation layer to expose the top surface of the contact structure under test.

[0011] In some embodiments, a focused ion beam is used to remove a portion of the second passivation layer to form a plurality of discrete vias, each of which exposes the top surface of a corresponding contact structure under test.

[0012] In some embodiments, the testing method further includes: forming an extension layer that fills the through-hole, the material of the extension layer being the same as the material of the contact structure under test, and a probe making electrical contact with the top surface of the contact structure under test through the extension layer.

[0013] In some embodiments, the process steps for forming the extended layer include: depositing a metal compound and reducing the metal atoms in the metal compound using a focused ion beam to form the extended layer.

[0014] In some embodiments, the contact structure under test includes a first portion and a second portion stacked from bottom to top, the first portion being located between the second portion and the conductive substrate, and the cross-sectional area of ​​the second portion being larger than the cross-sectional area of ​​the first portion in the direction of excitation current flow.

[0015] In some embodiments, in the direction of the excitation current flow, the cross-section of the first portion is circular, and the cross-section of the second portion is rectangular.

[0016] In some embodiments, the second part consists of an initial contact structure and a filling portion that are in contact with each other. The initial contact structure and the filling portion are independent and different structures. The filling portion surrounds the top of the initial contact structure. The filling portion and the surrounding portion of the initial contact structure constitute the second part, and the remaining portion of the initial contact structure serves as the first part.

[0017] In some embodiments, the process steps of providing the conductive substrate and the contact structures to be measured comprise: providing a conductive substrate and a passivation layer stacked in sequence, the passivation layer having a plurality of initial contact structures therein, the initial contact structures penetrating through the passivation layer; removing part of the passivation layer to form a plurality of discrete grooves, each of the grooves surrounding a top of a corresponding initial contact structure; forming a filling portion filling the grooves, the filling portion having a contact resistance to the initial contact structure smaller than a contact resistance of the initial contact structure to the conductive substrate, the filling portion and the initial contact structure constituting the contact structures to be measured.

[0018] In some embodiments, the material of the conductive substrate comprises a metal material, a metal compound, and a doped semiconductor.

[0019] In some embodiments, the grooves and the filling portions are formed in the same process step.

[0020] The technical solutions provided by the embodiments of the present application have at least the following advantages:

[0021] In the above technical solution, the path resistance of the voltage loop and the current loop both include the self-resistance of the first contact structure and the contact resistance of the first contact structure to the conductive substrate, and the voltage loop does not include the contact resistance of the first excitation probe to the first contact structure. Since the current of the voltage loop itself is very small, the voltage drop of the voltage loop is mainly caused by the first contact structure and the contact surface of the first contact structure to the conductive substrate, that is, the measurement of the voltage can exclude the influence of the contact resistance introduced by the probe. At the same time, by controlling the self-resistance of the first contact structure to be much smaller than the corresponding contact resistance, so that the voltage difference measured by the voltage loop is mainly caused by the contact resistance of the first contact structure, the contact resistance between the first contact structure and the conductive substrate can be accurately measured. BRIEF DESCRIPTION OF DRAWINGS

[0022] One or more embodiments are illustrated by way of example in the figures that are part of this disclosure and which are illustrative, but not limiting of the embodiments, unless otherwise specifically indicated. The figures of the accompanying drawings do not bear a ratio to each other.

[0023] Figures 1 to 6 The structure schematic diagram corresponding to each step of the test method provided by the embodiments of the present application. DETAILED DESCRIPTION

[0024] The embodiments of the present application will be described in detail below with reference to the drawings. However, those skilled in the art can understand that, in the embodiments of the present application, many technical details are presented in order to make the reader better understand the present application. However, the technical solutions claimed by the present application can be implemented even without these technical details and based on various changes and modifications of the following embodiments.

[0025] Figures 1 to 6 The structural schematic diagram corresponding to each step of the test method provided for the embodiments of the present application is shown in the following.

[0026] Reference Figure 1 The test method comprises: providing a conductive substrate 10 and a plurality of discrete contact structures to be tested 11, the bottom end of the contact structure to be tested 11 being in contact with the conductive substrate 10, the contact structure to be tested 11 comprising a first contact structure 111, a second contact structure 112 and a third contact structure 113, the second contact structure 112 and the third contact structure 113 being located on different sides of the first contact structure 111; providing a first excitation probe 211 and a second excitation probe 212, the first excitation probe 211 being in electrical contact with the top surface of the first contact structure 111, and the second excitation probe 212 being in electrical contact with the top end of the second contact structure 112; providing a first detection probe 221 and a second detection probe 222, the first detection probe 221 being in electrical contact with the top end of the first contact structure 111, and the second detection probe 222 being in electrical contact with the top end of the third contact structure 113; providing an excitation current through the first excitation probe 211 and the second excitation probe 212, the excitation current flowing through the first contact structure 111 and the second contact structure 112 to form a current loop, and the first detection probe 221 and the second detection probe 222 forming a voltage loop; and obtaining the contact resistance of the first contact structure 111 and the conductive substrate 10 according to the voltage difference of the first detection probe 221 and the second detection probe 222 and the value of the excitation current.

[0027] In the above test method, the electrical contact between the probe and the top end of the contact structure to be tested 11 means that, in the voltage loop or the current loop, the current flowing through the probe flows from the bottom end to the top end of the contact structure to be tested 11 or from the top end to the bottom end. The probe and the top end of the contact structure to be tested 11 can be in direct contact or indirect contact. As the name implies, indirect contact means that the probe is electrically connected to the top end of the contact structure to be tested 11 through other conductive medium located at the top end of the contact structure to be tested 11.

[0028] In addition, the current in the current loop (i.e., the excitation current) is large, and the voltage drop caused by the current flowing through the conductive structure and the contact interface thereof is obvious; the current in the voltage loop is small, and the voltage drop caused by the current flowing through the conductive structure and the contact interface thereof can be ignored. In the voltage loop, the first detection probe 221 and the second detection probe 222 jointly function as a voltmeter, and the voltage difference between the first detection probe 221 and the second detection probe 222 is caused by the excitation current flowing through part of the path in the voltage loop, for example, caused by the first contact structure 111 and the contact interface thereof with the conductive substrate 10.

[0029] For the sake of brevity of expression, in the following, the "contact resistance of the first contact structure 111" refers to the contact resistance of the first contact structure 111 with the conductive substrate 10, and the "contact resistance of the probe" refers to the contact resistance between the excitation probe and the detection probe and the contact structure 11 to be measured. According to the above content, the excitation probe at least includes the first excitation probe 211 and the second excitation probe 212, and the detection probe at least includes the first detection probe 221 and the second detection probe 222.

[0030] In the above technical solution, by controlling the first excitation probe 211 and the first detection probe 221 to be in electrical contact with the top end of the first contact structure 111, and by controlling the second contact structure 112 and the third contact structure 113 to be located on different sides of the first contact structure 111, the path resistance of the current loop and the path resistance of the voltage loop only jointly include the self-resistance of the first contact structure 111 and the contact resistance of the first contact structure 111, and do not include the contact resistance of the probe and the resistance of the conductive substrate 10. In this way, it is beneficial to avoid the influence of the contact resistance of the probe on the final measurement result, and to accurately measure the sum of the self-resistance of the first contact structure 111 and the contact resistance of the first contact structure 111 according to the voltage difference of the voltage loop and the current value of the excitation current; under the condition of accurately measuring the above sum, by controlling the self-resistance of the first contact structure 111 to be much smaller than the contact resistance of the first contact structure 111, the above sum can be close to the contact resistance of the first contact structure 111, and thus the accurate measurement of the contact resistance of the first contact structure 111 is realized.

[0031] The embodiments of the present application will be described in more detail below with reference to the accompanying drawings.

[0032] In some embodiments, the current loop is formed by applying an excitation current to the first contact structure 111 through the first excitation probe 211, and controlling the voltage at the top end of the second contact structure 112 to be lower than the voltage at the top end of the first contact structure 111 through the second excitation probe 212, so that the excitation current flows to the top end of the second contact structure 112 through the conductive substrate 10. That is, the current is applied through the first excitation probe 211, and the potential is adjusted through the second excitation probe 212, so that the first contact structure 111 has a high potential and the second contact structure 112 has a low potential. Since the excitation current always tends to flow from a high potential to a low potential, a current loop containing the first contact structure 111 and the second contact structure 112 can be formed.

[0033] It can be understood that when the second contact structure 112 is controlled to be at a low potential by the second excitation probe 212, other contact structures 11 to be tested, including the first contact structure 111, are all at a high potential. Thus, it is beneficial to avoid the excitation current flowing to other contact structures 11 to be tested (for example, the third contact structure 113), ensuring that V≈I×(R m +R c ), where V refers to the voltage difference detected by the first detection probe 221 and the second detection probe 222, I refers to the preset value of the excitation current, R m refers to the self-resistance of the first contact structure 111, and R c refers to the contact resistance of the first contact structure 111. The preset value of the excitation current can be controlled by the technician or limited by the specifications of the current source.

[0034] In some embodiments, the second contact structure 112 and the third contact structure 113 are located on opposite sides of the first contact structure 111. Thus, it is beneficial to maximize the avoidance of the excitation current flowing through the part of the conductive substrate 10 between the first contact structure 111 and the third contact structure 113, avoiding the voltage difference detected by the first detection probe 221 and the second detection probe 222 containing the resistance of the conductive substrate 10, so as to accurately measure the sum of the self-resistance of the first contact structure 111 and the contact resistance of the first contact structure 111, which can be obtained by dividing the voltage difference detected by the first detection probe 221 and the second detection probe 222 by the preset value of the excitation current.

[0035] In some embodiments, the material of the contact structure 11 to be tested is different from the material of the conductive substrate 10. The sum of the self-resistance of the first contact structure 111 and the self-resistance of the first contact structure 111 is equal to R m +R c It can be understood that only when R m <<R c , can R m +Rc ≈R c , i.e. the resistance value calculated according to the voltage difference and the preset value of the excitation current can only be approximately taken as the contact resistance of the first contact structure 111. If the R m <<R c , on the one hand, the cross section of the first contact structure 111 can be made larger, the resistivity can be made smaller, and the length can be made shorter, so as to reduce the R m , on the other hand, the material difference between the contact structure 11 to be measured and the conductive base 10 can be made larger or the contact area can be made smaller, so as to increase the R c . That is, by setting the material of the contact structure 11 to be measured different from the material of the conductive base 10, it is beneficial to increase the R c , so that the R m +R c ≈R c , i.e. the contact resistance R c of the first contact structure 111 is accurately measured by the voltage difference and the current value of the excitation current.

[0036] Wherein, the materials and sizes of different contact structures 11 to be measured can be the same or different, and the sizes include but are not limited to the average cross-sectional area, the contact area with the conductive base 10, and the length in the direction of current extension. When the sizes and materials of different contact structures 11 to be measured are the same, the contact resistance of the contact structure 11 to be measured can be obtained by measuring the contact resistance of any specific contact structure 11 to be measured, for example, by measuring the first contact structure 111. The materials of the contact structure 11 to be measured and the conductive base 10 can be metal, metal compound, doped semiconductor, etc. For example, the metal includes copper, silver, aluminum, gold and tungsten, the metal compound includes titanium nitride and indium tin oxide, and the doped semiconductor includes doped polysilicon, doped monocrystalline silicon, doped microcrystalline silicon, and doped silicon carbide, etc.

[0037] In the actual process manufacturing process, the contact structure 11 to be measured generally refers to an intermediate structure such as a conductive plug connecting different wiring layers. Taking the conductive plug as an example, the contact structure 11 to be measured has the characteristics of shorter length and smaller resistance relative to the long wire in the wiring layer, which is beneficial to realize R m <<R c ; in other words, since the resistance test is based on the actual structure, the measurement result of the R c can be more effectively applied to the resistance calculation of the actual structure, so as to accurately calculate the path resistance of the conductive path.

[0038] In some embodiments, the cross section of the contact structure 11 to be tested is rectangular in the direction of the flow of the excitation current. Continuing to take the conductive plug as an example of the contact structure, the cross section of the conductive plug is generally circular or rectangular in the direction of the flow of the excitation current, the circular generally has a smaller cross-sectional area, and the rectangular generally has a larger aspect ratio to achieve a larger cross-sectional area. In the embodiments of the present application, the cross section of the contact structure 11 to be tested is set to be rectangular, which is conducive to ensuring that the cross-sectional area of the first contact structure 111 is large and the self-resistance is small, so as to achieve R m +R c ≈R c ; in addition, it is also conducive to ensuring that the first excitation probe 211 and the first detection probe 221 have enough space to be inserted into different positions on the top end of the first contact structure 111, so as to ensure that the test method provided by the embodiments of the present application can be effectively executed, that is, to avoid the excitation current applied by the first excitation probe 211 from flowing into the first detection probe 211, to ensure that the current value in the current loop is equal to the preset value of the excitation current, and to ensure that the voltage drop caused by the current in the voltage loop can be ignored.

[0039] In some embodiments, referring to Figure 2 and Figure 3 , the process steps of providing the conductive substrate 10 and the contact structure 11 to be tested include: providing a conductive substrate 10, a first passivation layer 101 and a second passivation layer 102 which are sequentially stacked, the contact structure 11 to be tested is located in the first passivation layer 101 and penetrates through the first passivation layer 101 and contacts the conductive substrate 10, the top surface of the contact structure 11 to be tested is flush with the top surface of the first passivation layer 101, and the second passivation layer 102 covers the top surface of the contact structure 11 to be tested and the top surface of the first passivation layer 101; and at least part of the second passivation layer 102 is removed to expose the top surface of the contact structure 11 to be tested.

[0040] In the embodiments shown in Figure 3 , the second passivation layer 102 is partially removed to form a plurality of discrete through holes 102a, each through hole 102a exposes the top surface of a corresponding contact structure 11 to be tested. When the cross-sectional area of the contact structure 11 to be tested is small, the cross-sectional area of the through hole 102a can be larger than that of the contact structure 11 to be tested, so as to facilitate the first excitation probe and the first detection probe to directly contact the top end of the contact structure 11 to be tested through the through hole 102a, and to avoid the first excitation probe and the first detection probe from being electrically contacted. The through hole 102a can be formed by a focused ion beam (FIB).

[0041] In some embodiments, referring to Figure 4 , the test method further includes: filling the through hole 102a (referring to Figure 3The extension layer 12 is made of the same material as the contact structure 11 to be tested, and the probe is in electrical contact with the top surface of the contact structure 11 to be tested through the extension layer 12. By arranging the extension layer 12, the probe can have a larger placement space without removing the second passivation layer 102 as a whole, thereby avoiding interference between different probes in electrical contact with the top end of the same contact structure 11 to be tested, i.e., avoiding electrical contact between the first excitation probe and the first detection probe and thereby shunting part of the excitation current.

[0042] In addition, the extension layer 12 is made of the same material as the contact structure 11 to be tested, which is conducive to minimizing the contact resistance between the extension layer 12 and the contact structure 11 to be tested, so that m +R c +R a +R ac ≈R c , R a is the self-resistance of the extension layer 12, and R ac is the contact resistance between the extension layer 12 and the contact structure 11 to be tested, thereby ensuring that the voltage difference measured by the first detection probe and the second detection probe can be approximately regarded as the voltage drop caused by the contact resistance of the contact structure 11 to be tested, and thus the contact resistance of the contact structure 11 to be tested can be accurately obtained; in addition, the extension layer 12 is made of the same material as the contact structure 11 to be tested, which is more in line with the actual production and manufacturing cost. When a component is missing and needs to be filled or the length is not enough and needs to be extended, the same material is generally selected for filling or extension to ensure the continuity and uniformity of the structural performance.

[0043] In some embodiments, the process steps for forming the extension layer 12 include depositing a metal compound and reducing metal ions in the metal compound by using a focused ion beam to form the extension layer 12. The deposition of the metal compound and the reduction by the focused ion beam can be performed simultaneously to ensure that the material of the extension layer 12 has a high purity, thereby reducing the self-resistance of the extension layer 12 and the contact resistance between the extension layer 12 and the contact structure 11 to be tested.

[0044] In some embodiments, the contact structure 11 to be tested includes a first portion and a second portion stacked from bottom to top, the first portion is located between the second portion and the conductive substrate 20, and in the flow direction of the excitation current, the cross-sectional area of the second portion is greater than that of the first portion. The cross section of the first portion can be circular, and the cross section of the second portion can be rectangular.

[0045] For example, with reference to Figure 5The to-be-tested contact structure 21 is composed of the initial contact structure 21a and the filling part 21b, and the initial contact structure 21a and the filling part 21b are independent and different structures, that is, the initial contact structure 21a and the filling part 21b are formed by different process steps respectively, the filling part 21b surrounds the top of the initial contact structure 21a, the filling part 21b and the surrounded part of the initial contact structure 21a form a second part, and the remaining part of the initial contact structure 21a serves as a first part.

[0046] In some embodiments, with reference to Figure 5 and Figure 6 , the process steps of providing the conductive substrate 20 and the to-be-tested contact structure 21 include: providing the conductive substrate 20 and the passivation layer 201 which are stacked in sequence, and the passivation layer 201 has a plurality of discrete initial contact structures 21a, the initial contact structures 21a penetrate through the passivation layer 201 and are in contact with the conductive substrate 20; removing part of the passivation layer 201 to form a plurality of discrete grooves 201a, each groove 201a surrounds the top of the corresponding initial contact structure 21a; forming the filling part 21b which fills the groove 201a, the contact resistance of the filling part 21b and the initial contact structure 21a is smaller than the contact resistance of the initial contact structure 21a and the conductive substrate 20, and the filling part 21b and the initial contact structure 21a constitute the to-be-tested contact structure 21. Similarly, as described above, the contact resistance of the filling part 21b and the initial contact structure 21a is controlled to be smaller than the contact resistance of the initial contact structure 21a and the conductive substrate 20, which is beneficial to ensure that the voltage difference measured by the first detection probe and the second detection probe can be approximately regarded as the voltage drop caused by the contact resistance of the to-be-tested contact structure 21, and thus the contact resistance of the to-be-tested contact structure 21 can be accurately obtained.

[0047] In some embodiments, the groove 201a and the filling part 21b are formed in the same process step. For example, the focused ion beam and the deposition of the metal compound can be formed at the same time, the focused ion beam is used for etching the passivation layer 201 and reducing the metal ions in the metal compound, and the groove 201a and the filling part 21b are formed at the same time, thereby shortening the forming time of the to-be-tested contact structure 21.

[0048] In the embodiments of the present application, the path resistance of the voltage loop and the current loop both include the self-resistance of the first contact structure and the contact resistance between the first contact structure and the conductive substrate, and the voltage loop does not include the contact resistance between the first excitation probe and the first contact structure. Since the current of the voltage loop itself is very small, the voltage drop of the voltage loop is mainly caused by the first contact structure and the contact surface between the first contact structure and the conductive substrate through which the excitation current flows, that is, the measurement of the voltage can exclude the influence of the contact resistance introduced by the probe. Meanwhile, by controlling the self-resistance of the first contact structure to be much smaller than the corresponding contact resistance, so that the voltage difference measured by the voltage loop is mainly caused by the contact resistance of the first contact structure, the contact resistance between the first contact structure and the conductive substrate can be accurately measured.

[0049] Those skilled in the art can understand that the above-mentioned embodiments are specific embodiments for implementing the present application, and in actual application, various changes can be made in form and details without departing from the spirit and scope of the present application. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application, therefore the protection scope of the present application should be limited by the scope defined in the claims.

Claims

1. A testing method, characterized in that, include: A conductive substrate and a plurality of discrete contact structures to be tested are provided. The bottom end of the contact structure to be tested is in contact with the conductive substrate. The contact structure to be tested includes a first contact structure, a second contact structure and a third contact structure. The second contact structure and the third contact structure are located on different sides of the first contact structure. A first excitation probe and a second excitation probe are provided, wherein the first excitation probe is in electrical contact with the top end of the first contact structure, and the second excitation probe is in electrical contact with the top end of the second contact structure; A first detection probe and a second detection probe are provided, wherein the first detection probe is in electrical contact with the top end of the first contact structure, and the second detection probe is in electrical contact with the top end of the third contact structure; Excitation current is provided through the first excitation probe and the second excitation probe, the excitation current flows through the first contact structure and the second contact structure to form a current loop, and the first detection probe and the second detection probe constitute a voltage loop; The contact resistance between the first contact structure and the conductive substrate is obtained based on the voltage difference between the first and second detection probes and the value of the excitation current. Wherein, the self-resistance of the first contact structure is much smaller than the contact resistance between the first contact structure and the conductive substrate.

2. The test method according to claim 1, characterized in that, Forming the current loop includes: applying the excitation current to the first contact structure through the first excitation probe, and controlling the top voltage of the second contact structure to be lower than the top voltage of the first contact structure through the second excitation probe, so that the excitation current flows through the conductive substrate to the top of the second contact structure.

3. The test method according to claim 1, characterized in that, The second contact structure and the third contact structure are located on opposite sides of the first contact structure.

4. The test method according to claim 1, characterized in that, The material of the contact structure to be tested is different from the material of the conductive substrate.

5. The test method according to claim 1, characterized in that, In the direction of the excitation current flow, the cross-section of the contact structure under test is rectangular.

6. The test method according to claim 1, characterized in that, The process steps for providing the conductive substrate and the contact structure to be tested include: A conductive substrate, a first passivation layer, and a second passivation layer are provided in sequence. The contact structure to be tested is located within the first passivation layer, penetrates the first passivation layer, and is in contact with the conductive substrate. The second passivation layer covers the top surface of the contact structure to be tested. At least a portion of the second passivation layer is removed to expose the top surface of the contact structure under test.

7. The test method according to claim 6, characterized in that, A portion of the second passivation layer is removed using a focused ion beam to form a plurality of discrete vias, each of which exposes the top surface of a corresponding contact structure to be tested.

8. The test method according to claim 7, characterized in that, Also includes: An extension layer is formed to fill the through-hole. The material of the extension layer is the same as that of the contact structure under test. The probe makes electrical contact with the top surface of the contact structure under test through the extension layer.

9. The test method according to claim 8, characterized in that, The process steps for forming the extended layer include: depositing a metal compound and reducing the metal atoms in the metal compound using a focused ion beam to form the extended layer.

10. The test method according to claim 1, characterized in that, The contact structure under test includes a first part and a second part stacked from bottom to top. The first part is located between the second part and the conductive substrate. In the direction of the excitation current flow, the cross-sectional area of ​​the second part is larger than that of the first part.

11. The test method according to claim 10, characterized in that, In the direction of the excitation current flow, the cross-section of the first part is circular, and the cross-section of the second part is rectangular.

12. The test method according to claim 10, characterized in that, The second part consists of an initial contact structure and a filling part that are in contact with each other. The initial contact structure and the filling part are independent and different structures. The filling part surrounds the top of the initial contact structure. The filling part and the surrounding part of the initial contact structure constitute the second part, and the remaining part of the initial contact structure serves as the first part.

13. The test method according to claim 12, characterized in that, The process steps for providing the conductive substrate and the contact structure to be tested include: A conductive substrate and a passivation layer are provided in sequence, wherein the passivation layer has a plurality of discrete initial contact structures that penetrate the passivation layer; A portion of the passivation layer is removed to form a plurality of discrete grooves, each groove surrounding the top of the corresponding initial contact structure; The filling portion is formed to fill the groove, and the contact resistance between the filling portion and the initial contact structure is less than the contact resistance between the initial contact structure and the conductive substrate. The filling portion and the initial contact structure constitute the contact structure to be tested.

14. The test method according to claim 13, characterized in that, The conductive substrate is made of metallic materials, metallic compounds, and doped semiconductors.

15. The test method according to claim 13, characterized in that, The groove and the filling portion are formed in the same process step.

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