Method and device for detecting surface of interconnection structure

Abstract

The invention discloses a method and device for detecting the surface of an interconnection structure. The interconnect structure includes a first metal layer, a second metal layer and a dielectric layer surrounding the second metal layer, the first metal layer and the dielectric layer are disposed over the second metal layer, and at least a portion of the first metal layer is exposed to a surface of the interconnect structure. A method of detecting a surface of an interconnect structure includes irradiating a surface of the interconnect structure with incident light having a first polarization state, receiving a plurality of optical signals having a second polarization state different from the first polarization state reflected via the interconnect structure, and judging a plane pattern of the first metal layer and a part of plane pattern of the second metal layer according to the intensity difference of the optical signals.

Description

Technical Field

[0001] This disclosure relates to a method for detecting the surface of an object, and particularly to a method for detecting the surface of an interconnect structure using polarized light. Background Art

[0002] When fabricating an integrated circuit, a redistribution layer (RDL) is often provided and the components or conductors at different positions in the integrated circuit are connected through the lines therein. For example, in a wafer-level packaging process, a redistribution layer is often provided on the integrated circuit to connect the input / output terminals with a relatively small distribution range on the integrated circuit to the solder pads or solder balls with a relatively large distribution range on the packaging wafer. Generally, the redistribution layer may include metal layers located in multiple planes, and each metal layer may include multiple metal lines, which are separated by dielectric layers.

[0003] In the process, in order to ensure the quality of the redistribution layer, it is necessary to detect the surface metal of the redistribution layer to determine whether there are short circuits, open circuits or deformations. However, when detecting the surface metal of the redistribution layer, due to the material of the dielectric layer, such as polyimide (PI), having a relatively high light transmittance, light often penetrates the dielectric layer and is incident on the underlying metal, resulting in the reflected light intensity of the underlying metal being comparable to that of the surface metal, making it difficult to distinguish the distribution of the surface metal from that of the underlying metal. Therefore, how to effectively distinguish the surface metal from the underlying metal so as to correctly detect the distribution of the surface metal has become a problem to be solved. Summary of the Invention

[0004] An embodiment of the present application provides a method for detecting the surface of an interconnect structure, where the interconnect structure includes a first metal layer, a second metal layer, and a dielectric layer surrounding the second metal layer, the first metal layer and the dielectric layer are disposed above the second metal layer, and at least a part of the first metal layer is exposed on the surface of the interconnect structure. The method for detecting the surface of the interconnect structure includes: irradiating the surface of the interconnect structure with incident light having a first polarization state, receiving a plurality of optical signals having a second polarization state different from the first polarization state reflected by the interconnect structure, and distinguishing at least one optical signal reflected from the first metal layer and at least one optical signal reflected from the second metal layer based on the intensity difference of the optical signals to obtain the planar pattern of the first metal layer.

[0005] Another embodiment of the present application provides a device for detecting the surface of an interconnect structure. The device includes a polarized light source, an analyzer, a sensor, and a controller. The polarized light source is used to generate incident light with a first polarization state to irradiate the surface of the interconnect structure, where the interconnect structure includes a first metal layer, a second metal layer, and a dielectric layer surrounding the second metal layer. The first metal layer and the dielectric layer are disposed above the second metal layer, and at least a portion of the first metal layer is exposed on the surface of the interconnect structure. The analyzer is used to receive the reflected light reflected by the interconnect structure and allow a plurality of optical signals with a second polarization state different from the first polarization state to pass through. The sensor is used to receive these optical signals. The controller is coupled to the sensor and is used to distinguish at least one optical signal reflected from the first metal layer and at least one optical signal reflected from the second metal layer based on the intensity difference of these optical signals, thereby obtaining the planar pattern of the first metal layer.

[0006] Another embodiment of the present application provides a method for detecting the surface of an interconnect structure, where the interconnect structure includes a first metal layer, a second metal layer, and a dielectric layer surrounding the first metal layer. The first metal layer and the dielectric layer are disposed above the second metal layer, and at least a portion of the first metal layer is exposed on the surface of the interconnect structure. The method for detecting the surface of the interconnect structure includes: adjusting the polarization angles of the polarizer and the analyzer, allowing the light source to pass through the polarizer to generate incident light to irradiate the interconnect structure, where the incident light has a first polarization state, receiving a plurality of optical signals reflected by the interconnect structure and passing through the analyzer, where these optical signals have a second polarization state different from the first polarization state, and distinguishing at least one optical signal reflected from the first metal layer and at least one optical signal reflected from the second metal layer based on the intensity difference of these optical signals, thereby obtaining a planar pattern of the first metal layer.

[0007] The method and device for detecting the surface of an interconnect structure provided by the embodiments of the present disclosure can utilize the depolarization effect when the surface metal layer and the inner metal layer of the interconnect structure reflect, so that the reflected light of both has a polarization state different from that of the incident light. Then, due to the different reflection environments of the two metal layers, there is a distinguishable difference in the intensity of the optical signals with the second polarization state in the reflected light of both, so as to judge based on this difference whether the optical signal is reflected from the metal on the surface or the metal layer inside. In this way, it is possible to judge the planar pattern of the metal layer located on the surface of the interconnect structure and reduce the problem of inaccurate judgment caused by the inability to distinguish the reflected light of the surface metal layer and the inner metal layer. Brief Description of the Drawings

[0009] Figure 1 is a flowchart of the steps of a method for detecting the surface of an interconnect structure according to an embodiment of the present application.

[0010] Figure 2 is a schematic diagram of the scenario of using the method to detect an interconnect structure according to an embodiment of the present application.

[0011] Figure 3 is the planar pattern of the surface metal layer of the interconnect structure in an embodiment of the present application. Figure 2

[0012] Figure 4 is the planar pattern of the inner metal layer of the interconnect structure in an embodiment of the present application. Figure 2

[0013] Figure 5 is a schematic diagram of an optical signal with a second polarization state reflected by the interconnect structure received when performing Figure 1

[0014] Figure 6 is another schematic diagram of an embodiment of the present application using Figure 1 to detect Figure 2

[0015] Figure 7 is another schematic diagram of an embodiment of the present application using Figure 1 to detect another interconnect structure.

[0016] Figure 8 is another schematic diagram of an embodiment of the present application using Figure 1 to detect another interconnect structure.

[0017] Figure 9 is a schematic diagram of a device for detecting the surface of an interconnect structure in an embodiment of the present disclosure. Embodiment

[0019] Figure 1 is a flowchart of the steps of method M1 for detecting the surface of an object in an embodiment of the present application, and Figure 2 is a schematic diagram of the scenario of using method M1 to detect the interconnect structure E1 in an embodiment of the present application. In this embodiment, method M1 may include steps S110 to S130 and can be applied to detect the surface of the interconnect structure E1. The interconnect structure E1 disclosed in the present disclosure includes but is not limited to printed circuit boards, semiconductor substrates or carriers, interposers, semiconductor wafers or redistributed layers (RDL) of packages, or other structures providing laminated wiring.

[0020] As Figure 2As shown, the interconnect structure E1 may include metal layers MT1, MT2 and a dielectric layer IL1. The metal layer MT2 may include a plurality of lines, and the dielectric layer IL1 may be disposed above the metal layer MT2 and may surround the metal layer MT2 to separate different lines in the metal layer MT2. In addition, the metal layer MT1 may include a plurality of lines, and at least a portion of the metal layer MT1 is exposed on the surface of the interconnect structure E1. The metal layer MT1 may be disposed above the metal layer MT2 and the dielectric layer IL1. That is, the lines in the metal layer MT1 may be separated from the lines in the metal layer MT2 by the dielectric layer IL1. In some embodiments, there may also be lines (not shown in Figure 2 ) that are longitudinally (e.g., in the Z direction) connected between the metal layer MT1 and the metal layer MT2, such that the metal layer MT1 can penetrate through the dielectric layer IL1 and be electrically connected to the metal layer MT2. In the present embodiment, the method M1 can be used to detect the surface of the interconnect structure E1.

[0021] In step S110, the interconnect structure E1 may be irradiated with incident light L1 having a first polarization state. As Figure 2 shown, some of the incident light L1 may be incident on the metal layer MT1, and some of the incident light L1 may be incident on the underlying metal layer MT2 after passing through the dielectric layer IL1. In the present embodiment, based on the depolarization characteristics of the metal, when the metal layer MT1 reflects the incident light L1 having the first polarization state, it will change the polarization state of some of the incident light L1. Therefore, the reflected light R1 will have a part with the first polarization state and a part with a second polarization state different from the first polarization state. Similarly, the reflected light R2 reflected by the metal layer MT2 will also have a part with the first polarization state and a part with the second polarization state.

[0022] In the present embodiment, the first polarization state may have a polarization direction parallel to the plane of incidence (i.e., the plane formed by the incident light L1 and the reflected lights R1, R2, e.g., the X-Z plane) (in Figure 2 , the polarization direction parallel to the plane of incidence is represented by short lines), that is, the P polarization state (p-polarization); and the second polarization state may have a polarization direction perpendicular to the plane of incidence (in Figure 2 , the polarization direction perpendicular to the plane of incidence is represented by dots), that is, the S polarization state (s-polarization), however, the present disclosure is not limited thereto. In some embodiments, the first polarization state may also be the S polarization state, and the second polarization state may be the P polarization state.

[0023] Since the depolarization characteristics of the metal are related to factors such as the roughness of the metal surface, the incident angle of the incident light, and the wavelength, etc., the depolarization ratios of the metal layer MT1 and the metal layer MT2 will be different. That is to say, the intensity of the optical signal with the second polarization state in the optical signal reflected by the metal layer MT1 will be different from the intensity of the optical signal with the second polarization state in the optical signal reflected by the metal layer MT2. In this case, after receiving a plurality of optical signals with the second polarization state reflected by the interconnect structure E1 in step S120, in step S130, the optical signals can be distinguished as being reflected from the metal layer MT1 or the metal layer MT2 according to the received optical signal intensity difference, so that the planar pattern of the metal layer MT1 can be obtained.

[0024] For example, if the depolarization ratio of the metal layer MT1 is greater than the depolarization ratio of the metal layer MT2, it means that the intensity of the optical signal with the second polarization state reflected by the metal layer MT1 will be greater than the intensity of the optical signal with the second polarization state reflected by the metal layer MT2. For example Figure 2 As shown, the dots representing the second polarization state direction in the reflected light R1 are distributed more densely, while the dots representing the second polarization state direction in the reflected light R2 are distributed more sparsely.

[0025] In some embodiments, when the intensity of the first optical signal (for example, the part with the second polarization state in the reflected light R1) is greater than the intensity of the second optical signal (for example, the part with the second polarization state in the reflected light R2), it can be determined that the first optical signal is reflected from the metal layer MT1, and the second optical signal is reflected from the metal layer MT2. However, the present disclosure is not limited thereto. In some embodiments, the threshold can also be set according to the actual operation situation. In this case, when the first optical signal is greater than the threshold, it can be determined that the first optical signal is reflected from the metal layer MT1 on the surface of the interconnect structure E1, and when the second optical signal is less than the threshold, it can be determined that the second optical signal is reflected from the metal layer MT2 inside the interconnect structure E1.

[0026] Figure 3 is the planar pattern of the surface metal layer MT1 of the interconnect structure E1 according to an embodiment of the present disclosure, Figure 4 is the planar pattern of the inner metal layer MT2 of the interconnect structure E1 according to an embodiment of the present disclosure. In Figure 4 the dotted part is the planar pattern of the metal layer MT1. Comparing Figure 3 and Figure 4 it can be seen that the metal layer MT1 and the metal layer MT2 partially overlap, and a part of the planar pattern of the metal layer MT2 extends outward from the planar pattern of the metal layer MT1. Figure 5 is a schematic diagram of the optical signal with the second polarization state reflected by the interconnect structure E1 received in step S120. In this embodiment,Figure 2 It can be a cross-sectional view seen by cutting the detection interconnect structure E1 along the Figure 3 and Figure 4 tangent line AA'. In Figure 5 , the white area A1 indicates that the intensity of the received reflected light signal is relatively large (e.g., greater than the threshold). The bottom net area A2 indicates that the intensity of the received reflected light signal is relatively small (e.g., less than the threshold). In addition, in this embodiment, the light source of the incident light L1 can be a dark field light source. Therefore, in Figure 5 , the part where no reflected light is received is the black background.

[0027] In this case, since the light signal intensity in the white area A1 is higher than that in the bottom net area A2, it can be determined that the light signal in the white area A1 is reflected from the metal layer MT1, while the light signal in the bottom net area A2 is not reflected from the metal layer MT1. Therefore, in step S130, it can be determined that the white area A1 is the planar pattern of the metal layer MT1.

[0028] That is to say, the method M1 can utilize the depolarization effect during the surface reflection of the metal layers MT1 and MT2, so that some of the light signals in the reflected lights R1 and R2 have a polarization state different from that of the incident light L1. Then, due to the difference between the reflection environment of the metal layer MT1 and the reflection environment of the metal layer MT2, there is a distinguishable difference in the light signal intensity of the reflected lights R1 and R2 with the second polarization state. Thus, based on this difference, it can be determined whether the light signal is reflected from the metal layer MT1 on the surface or the metal layer MT2 inside. In this way, it is possible to determine the planar pattern of the metal layer MT1 on the surface of the interconnect structure E1, and the problem of inaccurate judgment caused by the inability to distinguish the reflected lights of the metal layers MT1 and MT2 can be reduced.

[0029] In some embodiments, the refractive index of the dielectric layer IL1 can be greater than the refractive index of the environment in contact with the surface of the interconnect structure E1. For example, if the interconnect structure E1 is disposed in air, the refractive index of the dielectric layer IL1 can be greater than the refractive index of air, that is, the refractive index of the dielectric layer IL1 can be greater than 1. In this case, since the incident light L1 will be refracted by the dielectric layer IL1 before entering the metal layer MT2, the incident angle θ2 of the incident light L1 entering the metal layer MT2 will be smaller than the incident angle θ1 of the incident light L1 entering the metal layer MT1. In this case, the difference in the incident angles of the incident metal layers MT1 and MT2 can further expand the difference between the depolarization ratio of the metal layer MT1 and the depolarization ratio of the metal layer MT2, making the judgment of the planar pattern of the surface metal layer MT1 more accurate.

[0030] In some embodiments, the material of the dielectric layer IL1 may include, for example, polyimide, but the present application is not limited thereto. In some other embodiments, other suitable materials may also be selected to fabricate the dielectric layer IL1 in order to increase the difference in the intensity of the light signal with the second polarization state reflected from the metal layer MT1 and the intensity of the light signal with the second polarization state reflected from the metal layer MT2, thereby increasing the accuracy in obtaining the planar pattern of the metal layer MT1.

[0031] In some embodiments, the materials of the metal layers MT1 and MT2 may include, for example, copper, but the present application is not limited thereto. In some other embodiments, other suitable metals may also be selected according to requirements, such as any one of gold, silver, aluminum, nickel, tin, and platinum or their alloys, to fabricate the metal layers MT1 and MT2, in order to increase the difference in the intensity of the light signal with the second polarization state reflected from the metal layer MT1 and the intensity of the light signal with the second polarization state reflected from the metal layer MT2, thereby increasing the accuracy in obtaining the planar pattern of the metal layer MT1.

[0032] In some embodiments, the dark field light source for generating the incident light L1 may include one or more wavelengths, such as visible light or ultraviolet light, and the interconnect structure E1 may be irradiated by means of mixing light at multiple angles. In some embodiments, the difference in the intensity of the light signal with the second polarization state reflected from the metal layer MT1 and the intensity of the light signal with the second polarization state reflected from the metal layer MT2 can be further increased by adjusting the wavelength and incident angle of the incident light L1, so that the determination of the planar pattern of the surface metal layer MT1 can be more accurate.

[0033] For example, in some embodiments, after experimental tests, an appropriate wavelength of the incident light L1 may be selected to maximize the difference in the intensity of the light signal with the second polarization state reflected from the metal layer MT1 and the intensity of the light signal with the second polarization state reflected from the metal layer MT2, so as to increase the accuracy of using the method M1 to determine the planar pattern of the metal layer MT1.

[0034] In addition, in some embodiments, the characteristics of the Brewster angle may be used to weaken the intensity of the incident light entering the dielectric layer IL1, thereby increasing the difference in the intensity of the light signal with the second polarization state reflected from the metal layer MT1 and the intensity of the light signal with the second polarization state reflected from the metal layer MT2. When the incident light enters the second medium at the Brewster angle, a part of the light signal with the polarization direction perpendicular to the incident plane formed by the incident light and the reflected light will be significantly reflected on the surface of the second medium, so only part of the light signal with this perpendicular polarization state can enter the second medium.

[0035] Figure 6It is another schematic diagram of the usage scenario of method M1 for detecting the interconnect structure E1 in an embodiment of the present application. In Figure 6 , the incident light L2 has an S polarization state (represented by dots in Figure 6 ), that is, its polarization direction is perpendicular to the plane formed by the incident light L2, the reflected lights R1 and R2. In this case, when the incident light L2 is incident at the Brewster angle θ3 of the dielectric layer IL1, a considerable part of the incident light L2 will be reflected by the dielectric layer IL1 (such as the reflected light R3). Therefore, the intensity of the incident light actually incident on the metal layer MT2 will be weakened. In this case, the optical signal with a P polarization state (represented by short lines in Figure 6 ) generated due to the depolarization characteristic during the reflection of the metal layer MT2 will also be weakened accordingly. In this way, the intensity of the optical signal with a P polarization state in the reflected light R4 reflected from the metal layer MT1 will be significantly greater than the intensity of the optical signal with a P polarization state in the reflected light R5 reflected from the metal layer MT2. That is to say, the difference between the intensity of the optical signal with a P polarization state reflected from the metal layer MT1 and the intensity of the optical signal with a P polarization state reflected from the metal layer MT2 can be further enlarged, making it possible to judge the planar pattern of the surface metal layer MT1 more accurately.

[0036] Figure 7 It is a schematic diagram of a usage scenario of method M1 for detecting the interconnect structure E2 in an embodiment of the present application. In Figure 7 's embodiment, the difference between the interconnect structure E2 and the interconnect structure E1 is that the interconnect structure E2 further includes another dielectric layer IL2 disposed on the dielectric layer IL1 and surrounding the metal layer MT1 to separate multiple lines in the metal layer MT1. In Figure 7 's embodiment, the surface of the dielectric layer IL2 can be flush with the surface of the metal layer MT1, and part of the metal layer MT1 is still exposed on the surface of the interconnect structure E2. In this case, the method M1 can still be used to detect the surface pattern of the metal layer MT1. As Figure 7 shows, the incident light L1 with the first polarization state can irradiate the surface of the interconnect structure E2 (step S110). At this time, some of the incident light L1 will be incident on the metal layer MT1, and some of the incident light will penetrate the dielectric layers IL1 and IL2 and be incident on the metal layer MT2. In this case, the optical signal with a second polarization state different from the first polarization state in the reflected lights R1' and R2' reflected by the metal layer MT1 and the metal layer MT2 can be received (step S120), and then based on the intensity of the optical signal, it can be judged whether the optical signal is reflected from the metal layer MT1 or the metal layer MT2, so as to judge the planar pattern of the metal layer MT1 on the surface of the interconnect structure E2 (step S130).

[0037] In some embodiments, since method M1 can detect the planar pattern of the metal layer on the surface of the interconnect structure, when multiple metal layers need to be fabricated, method M1 can also be used to detect whether the planar pattern of the newly formed metal layer meets the requirements each time a new metal layer is formed. After confirming that the planar pattern of the newly formed metal layer meets the requirements, the subsequent manufacturing process can be carried out to increase the yield of the final product. Figure 8 is a schematic diagram of a scenario using method M1 to detect interconnect structure E3 in an embodiment of the present application. In Figure 8 the embodiment, after forming a dielectric layer IL2 on the surface of the interconnect structure E1, another metal layer MT3 is formed on the interconnect structure E3. That is, the metal layer MT3 is disposed on the surface of the interconnect structure E3 and above the metal layer MT1 and the dielectric layer IL2. In this case, method M1 can still be used to determine the planar pattern of the metal layer MT3 on the surface of the interconnect structure E2.

[0038] For example, incident light L1 with a first polarization state can be used to irradiate the surface of the interconnect structure E3 (step S110), and an optical signal with a second polarization state different from the first polarization state in the reflected lights R6 and R7 reflected by the metal layer MT1 and the metal layer MT3 can be received (step S120). Then, based on the intensity of the optical signal, it can be determined whether the optical signal is reflected from the metal layer MT1 or the metal layer MT3, thereby determining the planar pattern of the metal layer MT3 on the surface of the interconnect structure E3 (step S130).

[0039] Figure 9 is a schematic diagram of a device 100 for detecting the surface of an interconnect structure in an embodiment of the present disclosure. The device 100 may include a polarization light source 110, an analyzer 120, a sensor 130, and a controller 140. In some embodiments, the device 100 can be used to perform the steps of method M1 to determine the planar pattern of the metal layer MT1 on the surface of the interconnect structure E1.

[0040] For example, the polarization light source 110 may perform step S110 to generate incident light L1 with a first polarization state to irradiate the surface of the interconnect structure E1. Furthermore, the analyzer 120 and the sensor 130 may perform step S120. That is, the analyzer 120 may receive the reflected lights R1 and R2 reflected by the interconnect structure E1, and allow a plurality of optical signals with a second polarization state different from (e.g., but not limited to, orthogonal to) the first polarization state to pass through. The sensor 130 may receive these optical signals passing through the analyzer 120. Then, the controller 140 may perform step S130. That is, the controller 140 may determine whether the optical signal is reflected from the metal layer MT1 or the metal layer MT2 according to the intensity of the optical signal received by the sensor 130, so as to obtain the planar pattern of the metal layer MT1. In some embodiments, the sensor 130 may convert the received optical signal into an electrical signal related to the intensity of the optical signal, such as a digital signal representing the intensity of the optical signal. The controller 140 may know the intensity of the optical signal received by the sensor 130 according to the electrical signal transmitted by the sensor 130, thereby performing corresponding judgments and calculations, and obtaining the planar pattern of the metal layer MT1, that is, completing step S130.

[0041] In some embodiments, the polarization light source 110 may include a dark field light source 112 and a polarizer 114. The dark field light source 112 may include one or more wavelengths and can mix light at multiple angles. The polarizer 114 may receive the light generated by the dark field light source 112 and allow the light with the first polarization state to pass through. In this way, the polarization light source 110 can use the dark field light source 112 and the polarizer 114 to generate incident light L1 with the first polarization state to irradiate the interconnect structure E1.

[0042] In some embodiments, the device 100 may further include an objective lens 150. As Figure 8 shown, the objective lens 150 may be disposed between the polarization light source 110 and the analyzer 120. In this embodiment, the polarization light source 110 may have a hollow structure, and the optical signal reflected by the interconnect structure E1 may enter the objective lens 150 through the hollow structure. The objective lens 150 may guide the reflected optical signal to the analyzer 120. The analyzer 120 may allow the reflected light with a second polarization state different from (e.g., but not limited to, orthogonal to) the first polarization state to pass through, so that the sensor 130 can receive the reflected optical signal with the second polarization state. In some embodiments, the objective lens 150 may include at least one lens and can adjust the traveling route of the reflected optical signal.

[0043] In some embodiments, the sensor 130 may include a photosensitive element, such as a charge-coupled device (CCD) or a complementary metal-oxide-semiconductor active pixel sensor (CMOS Active pixel sensor). In this case, the sensor 130 can convert an optical signal into an electrical signal, such as a digital signal, and the controller 140 can be implemented by a general-purpose processor or an application-specific integrated circuit that executes software corresponding to method M1. In some embodiments, when the controller 140 receives a first electrical signal corresponding to a first optical signal and a second electrical signal corresponding to a second optical signal, the controller 140 can determine the intensity magnitudes of the first optical signal and the second optical signal based on the first electrical signal and the second electrical signal. When the intensity of the first optical signal is greater than the intensity of the second optical signal, the controller 140 can determine that the first optical signal is reflected from the metal layer MT1 located on the surface of the interconnect structure, and can determine that the second optical signal is reflected from the metal layer MT2 located inside the interconnect structure. Alternatively, when the intensity of the first optical signal is greater than a threshold value, the controller 140 can determine that the first optical signal is reflected from the metal layer MT1, and when the intensity of the first optical signal is less than the threshold value, the controller 140 can determine that the first optical signal is reflected from the metal layer MT2. In this way, even when observing from a top view angle, although a part of the planar pattern of the metal layer MT2 overlaps with the planar pattern of the metal layer MT1, the controller 140 can still distinguish the boundary between the metal layers MT1 and MT2, and thus determine the planar pattern of the metal layer MT1.

[0044] In some embodiments, the controller 140 may also be coupled to the polarization light source 110, and can adjust the wavelength and the incident angle of the incident light L1 emitted by the polarization light source 110. For example, for different detection items, the controller 140 can control the polarization light source 110 to emit light with different wavelengths or different incident angles. For example, when detecting copper oxidation defects, the controller 140 can control the polarization light source 110 to emit incident light with a short wavelength. In addition, in some embodiments, the controller 140 can also adjust the incident angle when the polarization light source irradiates the interconnect structure E1, for example, making the incident angle of the incident light L1 be the Brewster angle corresponding to the air medium and the dielectric layer IL1, so as to increase the difference in the intensity of the optical signal with the second polarization state reflected from the metal layer MT1 and the intensity of the optical signal with the second polarization state reflected from the metal layer MT2, making it possible to be more accurate when determining the planar pattern of the surface metal layer MT1.

[0045] In some embodiments, when the polarization directions of the polarizer 114 and the analyzer 120 are changed, the difference in the intensities of the optical signals that pass through the analyzer 120 after being reflected by the metal layer MT1 and the metal layer MT2 may also change accordingly. Therefore, in some embodiments, after experimental testing, the polarizer 114 and the analyzer 120 can be configured to maximize the difference in the intensities of the optical signals that pass through the analyzer 120 after being reflected by the metal layer MT1 and the metal layer MT2, enabling the controller 140 to more accurately determine the planar pattern of the surface metal layer MT1.

[0046] In summary, the method and apparatus for detecting the surface of an interconnect structure provided by the embodiments of the present disclosure can utilize the depolarization effect during the reflection of the surface metal layer and the inner metal layer of the interconnect structure, such that the reflected lights of both have polarization states different from the incident light. Then, due to the differences in the reflection environments of the two metal layers, there is a distinguishable difference in the intensities of the optical signals with the second polarization state in the reflected lights of both, thereby determining based on this difference whether the optical signal is reflected from the metal on the surface or the inner metal layer. In this way, it is possible to determine the planar pattern of the metal layer located on the surface of the interconnect structure and reduce the problem of inaccurate judgment caused by the inability to distinguish the reflected lights of the surface metal layer and the inner metal layer.

[0047] Symbol Description

[0048] 100: Apparatus

[0049] 110: Polarized light source

[0050] 112: Dark field light source

[0051] 114: Polarizer

[0052] 120: Analyzer

[0053] 130: Sensor

[0054] 140: Controller

[0055] 150: Objective lens

[0056] A1, A2: Region

[0057] E1, E2, E3: Interconnect structure

[0058] IL1, IL2: Dielectric layer

[0059] L1, L2: Incident light

[0060] M1: Method

[0061] MT1, MT2, MT3: Metal layer

[0062] R1, R2, R1', R2', R3, R4, R5, R6, R7: Reflected light

[0063] S110, S120, S130: Steps

[0064] θ1, θ2, θ3: Incident angles

Claims

1. A method for inspecting a surface of an interconnect structure, wherein the interconnect structure comprises a first metal layer, a second metal layer and a dielectric layer surrounding the second metal layer, the first metal layer and the dielectric layer are disposed above the second metal layer, and at least a portion of the first metal layer is exposed to the surface of the interconnect structure, the method comprising: irradiating a surface of an interconnect structure with an incident light having a first polarization state; receiving a plurality of optical signals having a second polarization state different from the first polarization state reflected by the interconnect structure; and At least one light signal reflected from the first metal layer and at least one light signal reflected from the second metal layer are distinguished according to the intensity difference of the light signals, so as to obtain a plane pattern of the first metal layer. 2 . The method of claim 1 , wherein a polarization direction of the first polarization state is orthogonal to a polarization direction of the second polarization state. 3 . The method of claim 1 , wherein an intensity of the optical signal reflected from the first metal layer is greater than an intensity of the optical signal reflected from the second metal layer.

4. The method of claim 1 further comprises selecting a wavelength of the incident light to maximize a difference between an intensity of a first light signal having a second polarization state after being reflected by the first metal layer and an intensity of a second light signal having a second polarization state reflected from the second metal layer.

5. The method of claim 1, wherein a polarization direction of the first polarization state is perpendicular to an incident plane formed by the incident light and the optical signals, and the incident light enters the interconnect structure at a Brewster angle to weaken the intensity of the incident light entering the dielectric layer.

6. The method of claim 1 , wherein the step of distinguishing the at least one light signal reflected from the first metal layer and the at least one light signal reflected from the second metal layer according to the intensity difference of the light signals to obtain the planar pattern of the first metal layer comprises: When the intensity of a first optical signal is greater than a threshold, determining that the first optical signal is reflected from the first metal layer; or When the intensity of the first optical signal is greater than the intensity of a second optical signal, it is determined that the first optical signal is reflected from the first metal layer, and it is determined that the second optical signal is reflected from the second metal layer.

7. The method of claim 1, wherein a refractive index of the dielectric layer is greater than a refractive index of an environment in contact with the surface of the interconnect structure. 8 . The method of claim 1 , wherein a depolarization ratio of the first metal layer when reflecting a light signal is greater than a depolarization ratio of the second metal layer when reflecting a light signal.

9. A device for detecting a surface of an interconnect structure, comprising: A polarized light source for generating an incident light having a first polarization state to illuminate a surface of an interconnect structure, wherein the interconnect structure comprises a first metal layer, a second metal layer and a dielectric layer surrounding the second metal layer, the first metal layer and the dielectric layer are disposed above the second metal layer, and at least a portion of the first metal layer is exposed to the surface of the interconnect structure; an analyzer, for receiving the reflected light reflected by the interconnect structure and allowing a plurality of optical signals having a second polarization state different from the first polarization state to pass through; a sensor, for receiving the optical signals; and A controller is coupled to the sensor and is used to distinguish at least one light signal reflected from the first metal layer and at least one light signal reflected from the second metal layer according to the intensity difference of the light signals so as to obtain a planar pattern of the first metal layer.

10. The device of claim 9, wherein a polarization direction of the first polarization state is orthogonal to a polarization direction of the second polarization state.

11. The device as claimed in claim 9, wherein the polarized light source and the polarizer are configured to maximize the difference between the intensity of a first light signal passing through the polarizer after being reflected by the first metal layer and the intensity of a second light signal passing through the polarizer after being reflected by the second metal layer. 12 . The device of claim 11 , wherein an intensity of the optical signal reflected from the first metal layer is greater than an intensity of the optical signal reflected from the second metal layer.

13. The device of claim 9, wherein the polarized light source comprises: a dark field light source comprising one or more wavelengths; and A polarizer is used to receive the light generated by the dark field light source and allow the light with the first polarization state to pass through.

14. The device of claim 13, wherein the polarizer is configured to maximize the difference between the intensity of a first light signal having the second polarization state after being reflected by the first metal layer and the intensity of a second light signal having the second polarization state reflected from the second metal layer.

15. The device of claim 9, wherein the first polarization state is a polarization state perpendicular to a plane formed by the incident light and the optical signals, and the device is configured to cause the incident light to enter the interconnect structure at a Brewster angle to reduce the intensity of the incident light entering the dielectric layer.

16. A method for inspecting a surface of an interconnect structure, wherein the interconnect structure comprises a first metal layer, a second metal layer, and a dielectric layer surrounding the second metal layer, the first metal layer and the dielectric layer are disposed above the second metal layer, and at least a portion of the first metal layer is exposed to the surface of the interconnect structure, the method comprising: Adjust the polarization angles of a polarizer and an analyzer; Allow a light source to pass through the polarizer to generate an incident light to illuminate the interconnect structure, wherein the incident light has a first polarization state; receiving a plurality of optical signals reflected by the interconnect structure and passing through the analyzer, wherein the optical signals have a second polarization state different from the first polarization state; and At least one light signal reflected from the first metal layer and at least one light signal reflected from the second metal layer are distinguished according to the intensity difference of the light signals, so as to obtain a plane pattern of the first metal layer.

17. The method of claim 16, wherein the step of distinguishing the at least one light signal reflected from the first metal layer and the at least one light signal reflected from the second metal layer according to the intensity difference of the light signals to obtain the planar pattern of the first metal layer comprises: When the intensity of a first optical signal is greater than a threshold, determining that the first optical signal is reflected from the first metal layer; or When the intensity of the first optical signal is greater than the intensity of a second optical signal, it is determined that the first optical signal is reflected from the first metal layer, and it is determined that the second optical signal is reflected from the second metal layer.

18. The method of claim 16, wherein a polarization direction of the first polarization state is orthogonal to a polarization direction of the second polarization state.

19. The method as claimed in claim 16, wherein the step of adjusting the polarization angles of the polarizer and the analyzer includes adjusting the polarization angles of the polarizer and the analyzer to maximize the difference between the intensity of a first light signal passing through the analyzer after being reflected by the first metal layer and the intensity of a second light signal passing through the analyzer after being reflected by the second metal layer.

20. The method of claim 16, wherein a polarization direction of the first polarization state is perpendicular to an incident plane formed by the incident light and the optical signals, and the incident light enters the interconnect structure at a Brewster angle to reduce the intensity of the incident light entering the dielectric layer.

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