Eddy current end point detection device and chemical mechanical polishing apparatus

Abstract

The application provides an eddy current end point detection device and a chemical mechanical polishing equipment comprising the same. The eddy current end point detection device comprises a shell, a PCB board and a control module. The PCB board is packaged in the shell and comprises a resonant circuit integrated therein, the resonant circuit comprising an induction coil; the control module is electrically connected with the PCB board, and the control module detects the thickness of a metal film of a wafer arranged towards the PCB board based on a current signal in the resonant circuit. According to the technical scheme of the application, the manufacturing precision and integration efficiency of the induction coil are improved by integrating the induction coil in the PCB board, the problems of large manufacturing error and large detection deviation of the traditional wound coil are avoided, and the accuracy and consistency of the end point detection are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of integrated circuit chemical mechanical polishing (CMP) process, in particular to an eddy current end point detection device and a chemical mechanical polishing equipment comprising the same. BACKGROUND

[0002] The chemical mechanical polishing process uses a polishing pad and a polishing liquid to grind a wafer, and realizes the planarization of the wafer surface through the combination of mechanical and chemical methods. In the process, the judgment of the polishing end point is very important, that is, whether the expected removal amount or the expected thickness is reached. Excessive polishing of the wafer will lead to deviation from the target film thickness, thereby reducing the device performance or yield; on the other hand, insufficient polishing will force the wafer to be reworked and increase the overall production cost of integrated circuits. The working principle of the end point detection (EPD) device in the chemical mechanical polishing system mainly includes optical end point detection, acoustic end point detection, electrical end point detection and the like, and the common one is the eddy current detection method, which tracks the process by detecting the eddy current size of the metal film of the wafer with different thicknesses to determine the process end point.

[0003] However, the winding processing precision of the inductive coil in the existing eddy current detection device is low, and the inductive coil consistency is poor, which is difficult to achieve the required detection precision and cannot accurately provide end point detection. In addition, the detection result of the eddy current detection device is easily affected by temperature, and as the polishing process proceeds, the ambient temperature near the eddy current detection device will change, thereby affecting the measurement result. SUMMARY

[0004] The present application provides an eddy current end point detection device and a chemical mechanical polishing equipment comprising the same to solve or alleviate at least some of the above problems.

[0005] According to one aspect of the present application, an eddy current end point detection device for a chemical mechanical polishing equipment is provided, which comprises a housing, a PCB board encapsulated in the housing and comprising a resonant circuit integrated therein, the resonant circuit comprising an inductive coil, and a control module electrically connected with the PCB board, the control module detecting the thickness of a metal film of a wafer arranged towards the PCB board based on a current signal in the resonant circuit.

[0006] In an optional or alternative embodiment, the eddy current end point detection device comprises a control board encapsulated in the housing, and the control module is arranged on the control board.

[0007] In an alternative or optional embodiment, the control module comprises an electrically connected signal acquisition module and a signal analysis module, the signal acquisition module is configured to acquire the current signal in the resonant circuit, and the signal analysis module is configured to obtain the thickness information of the metal film based on the current signal.

[0008] In an alternative or optional embodiment, the shell is configured in a cylindrical shape, the PCB plate is configured as a circular sheet or a part of a circular sheet matching the inner diameter size of the shell, and the induction coil is wrapped in a plane parallel to the PCB plate.

[0009] In an alternative or optional embodiment, the induction coil is wrapped in a circular shape, an elliptical shape, or a rectangular shape.

[0010] In an alternative or optional embodiment, the PCB plate is arranged at an end of the shell via a retaining ring, the retaining ring is configured with a positioning portion, and the PCB plate is mounted to the retaining ring based on the positioning portion.

[0011] In an alternative or optional embodiment, the shell comprises a fixing portion arranged at another end of the shell opposite to the PCB plate, and the fixing portion is configured to fix the shell to a preset position.

[0012] In an alternative or optional embodiment, the shell is filled with epoxy resin.

[0013] In an alternative or optional embodiment, the shell is made of a heat-insulating material.

[0014] According to another aspect of the present application, a chemical mechanical polishing device is provided, comprising a polishing table for polishing a wafer and an eddy current end point detection device according to any one of the preceding aspects, the eddy current end point detection device being arranged in the polishing table to detect the thickness of a metal film of the wafer.

[0015] According to the eddy current end point detection device and the chemical mechanical polishing device of the present application, by integrating the induction coil in the PCB plate, the manufacturing precision and integration efficiency of the induction coil are improved, the problems of large manufacturing error and large detection deviation of the traditional wound coil are avoided, and the accuracy and consistency of the polishing process end point detection are improved. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiment or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art based on these drawings.

[0017] Figure 1 shows a perspective view of a chemical mechanical polishing apparatus according to an embodiment of the present application;

[0018] Figure 2 shows a perspective view of an eddy current end point detection device in Figure 1 ;

[0019] Figure 3 is a schematic view of a PCB board in the eddy current end point detection device of Figure 2 ;

[0020] Figure 4 shows a schematic view of an inductive coil in the PCB board in Figure 3 ;

[0021] Figure 5 shows a schematic view of another embodiment of an inductive coil in the PCB board in Figure 3 ;

[0022] Figure 6 shows a schematic view of another embodiment of an inductive coil in the PCB board in Figure 3 ;

[0023] Figure 7 shows a schematic view of a stop ring in the eddy current end point detection device of Figure 2 ;

[0024] Figure 8 shows a schematic view of another angle of the stop ring in Figure 7 ;

[0025] Figure 9 shows a schematic view of a circuit principle of the eddy current end point detection device in Figure 2 ;

[0026] Figure 10 shows a schematic view of a working principle of the eddy current end point detection device in Figure 2 ;

[0027] Figure 11 shows a flow chart of a method of polishing end point detection according to an embodiment of the present application.

[0028] Reference Signs List :

[0029] chemical mechanical polishing apparatus 10, polishing disc 11, polishing head 12, liquid supply device 13, dresser 14, polishing pad 15, transmission member 16;

[0030] The eddy current end point detection device 100, the shell 110, the blocking ring 111, the positioning part 1111, the fixing part 112, the PCB board 120, the resonance circuit 121, the induction coil 1211, the control module 130, the signal acquisition module 131, and the signal analysis module 132.

[0031] Equivalent impedance Z, parallel resonance capacitor C, signal generation driver M, high-precision sampling resistor R, current i1 of the driving circuit, current i2 of the resonance circuit 121, wafer W. DETAILED DESCRIPTION

[0032] In order to make the personnel in the art better understand the technical solutions in the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the embodiments of the present application shall belong to the scope of protection of the embodiments of the present application.

[0033] In the description of the present application, it should be understood that the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0034] In addition, in the description of the present application, unless otherwise specified and limited, it should be noted that the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be mechanical connection or electrical connection, it can be the communication between two elements, it can be directly connected, or indirectly connected through an intermediate medium, and those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0035] Figure 1A perspective view of a chemical mechanical polishing (CMP) apparatus 10 according to one embodiment of this application is shown. CMP is an ultra-precision surface processing technology for global planarization, enabling wafers to undergo CMP polishing through a combination of chemical and mechanical processes. The CMP apparatus 10 mainly includes a polishing disk 11 and a polishing head 12. A polishing pad 15 is disposed on the polishing disk 11. The wafer to be polished is loaded (e.g., by vacuum adsorption) onto the side of the polishing head 12 facing the polishing disk 11. The rotating polishing head 12 presses a metal film on the wafer against the polishing pad 15 with a certain pressure. The shaft of the polishing head 12 drives the polishing head 12 to move along the polishing disk 11, and a transmission component 16 below the polishing disk 11 drives the polishing disk 11 to rotate around its own axis. A liquid supply device 13 supplies flowing polishing slurry between the wafer surface and the polishing pad 15. The surface portion of the wafer can chemically react with the polishing slurry, and the reaction products can be removed by the mechanical polishing action of the polishing pad 15. Thus, wafer planarization is achieved through a coupled polishing process of chemical and mechanical film removal. In use, after polishing several wafers, the polishing pad 15 is ground very flat, which easily causes glazing. This causes the polishing pad 15 to lose some of its ability to retain polishing fluid. Therefore, the chemical mechanical polishing equipment 10 can also be equipped with a dresser 14, which is configured to move along the surface of the polishing pad 15 to dress the surface of the polishing pad 15, thereby extending the service life of the polishing pad 15 and making it easier to obtain wafers with better surface polishing quality.

[0036] Figure 2 This is a perspective view of an eddy current endpoint detection device 100 according to one embodiment of this application. The eddy current endpoint detection device 100 can be used for... Figure 1 The chemical mechanical polishing (CMP) equipment 10, which can be set in the polishing disc 11, is used to determine the polishing endpoint, i.e., whether the expected removal amount or expected thickness has been reached, thereby determining whether the polishing process has reached its endpoint and avoiding the negative effects of under-polishing (no polishing effect) and over-polishing (loss of underlying material). Specifically, the eddy current endpoint detection device 100 mainly includes a housing 110 and a PCB board 120 (Printed Circuit Board) and a control module 130 encapsulated in the housing 110. Figure 3 As can be seen, the PCB board 120 mainly includes the resonant circuit 121 disposed therein (see...). Figure 9), the resonant circuit 121 includes an induction coil 1211, which can be integrally manufactured in the PCB board 120 in the process of manufacturing the PCB board 120. In alternative or replaceable embodiments, the induction coil 1211 can be integrally manufactured between the opposite two surface layers of the PCB board (for example, between one surface layer and the inner layer adjacent thereto) in the process of layer-by-layer manufacturing of the PCB board, so that the surface of the PCB board is overall flat to protect the coil structure from external damage and ensure the stability of its function. Due to the high precision of the manufacturing equipment of the PCB board 120, the manufacturing and integration of the induction coil 1211 are carried out by means of the manufacturing equipment in the process of manufacturing the PCB board, so that the manufacturing precision of the induction coil 1211 is improved, the manufacturing error caused by the winding machine winding the induction coil 1211 is avoided, and the standardization and consistency of the manufacturing of the induction coil 1211 are improved, thereby ensuring the manufacturing precision and functional consistency of the eddy current end point detection device 100.

[0037] Figure 3 The PCB board 120 shown in the figure is a circular sheet, and in alternative or replaceable embodiments, the PCB board 120 can also be designed as a semicircular sheet, or a part of a circular sheet larger or smaller than a semicircular sheet obtained by cutting along a chord smaller than the diameter of a circle. In addition, it can be understood that the circular sheet, semicircular sheet or part of the circular sheet referred to herein refers to a sheet structure whose axial dimension (or thickness) is smaller than the radial dimension, and the cross section is circular, semicircular or circular. Figures 4-6 Three embodiments of the induction coil 1211 are shown respectively, and it can be seen that the induction coil 1211 can be designed as a circularly wrapped induction coil 1211, an elliptically wrapped induction coil 1211 or a rectangularly wrapped induction coil 1211, or other suitable wrapped shapes according to actual manufacturing requirements or arrangement needs.

[0038] Figure 3 The control module 130 is also shown in the figure, which is electrically connected with the PCB board 120, and the control module 130 can detect the thickness of the metal film of the wafer arranged towards the PCB board 120 based on the current signal (or eddy current signal) in the resonant circuit 121 in the PCB board 120. The control module 130 can be configured to control the chemical mechanical polishing equipment 10 to stop polishing operation when the thickness of the metal film reaches a preset thickness, or send an end point signal to other operation controllers in communication connection with the control module 130 to make the chemical mechanical polishing equipment 10 stop polishing operation. Alternatively, the control module 130 can be integrated into the PCB board 120, or can be arranged on another control board (not shown), and the control board and the PCB board 120 can be both packaged in the shell 110, for example, the control board is arranged in the cavity of the shell 110, and the PCB board 120 is arranged on the side of the control board facing the wafer Figure 2It is located on the upper side of the housing 110 and near the end of the housing 110. In a specific embodiment, the control module 130 may include a signal acquisition module 131 and a signal analysis module 132 that are electrically connected to each other. The signal acquisition module 131 may be configured to acquire the current signal in the resonant circuit 121, and the signal analysis module 132 may be configured to obtain the thickness change information of the metal film based on the change of the current signal, so as to determine whether the polishing endpoint has been reached.

[0039] Figure 7 and Figure 8 They are shown respectively Figure 2 A schematic diagram of the retaining ring 111 at different angles in the eddy current endpoint detection device 100. The retaining ring 111 can be nested and fixed to the inner wall of the housing 110, for example, by snap-fit ​​or threaded connection. The PCB board 120 is disposed at the end of the housing 110 via the retaining ring 111, for example... Figure 2 At the upper end of the PCB board, when the eddy current endpoint detection device 100 is installed in the polishing stage, this end faces the wafer, thereby bringing the resonant circuit 121 in the PCB board closer to the metal film of the wafer, so that the metal film interacts with the resonant circuit 121, causing a change in the induced current in the resonant circuit 121. In a specific embodiment, the retaining ring 111 may have an annular groove adapted to the size of the PCB board along its inner wall (e.g., integrally formed), so that the PCB board 120 can be snapped onto the retaining ring 111 via the annular groove. Figure 7 As shown, the retaining ring 111 can be configured with a positioning part 1111. The PCB board 120 can determine the angle or position to be installed on the retaining ring 111 based on the positioning part 1111, thereby facilitating installation and positioning, ensuring the accuracy of the installation orientation, and improving assembly efficiency. Furthermore, to further secure the PCB board 120, in a preferred embodiment, a fastening part (not shown) can be constructed on the retaining ring 111. For example, a structure with fastening holes can be provided (or integrally formed) on the inner side of the retaining ring 111, so that the PCB board 120 can be fastened to the retaining ring 111 via screws or pins. The design of the retaining ring 111 structure according to this application makes the disassembly and fixing of the PCB board 120 more convenient, improves the assembly efficiency of the eddy current endpoint detection device 100, ensures the stable positioning of the PCB board 120 in the housing 110, and thus improves the manufacturing efficiency and operational stability of the eddy current endpoint detection device.

[0040] In a preferred embodiment, after the PCB board 120 is installed into the housing 110, the side of the PCB board 120 facing the outside of the housing 110 is further sealed with adhesive to protect the PCB board 120 from external contamination or damage, improve the stability of the PCB board 120's operation, and extend its service life. On the other hand, the sealed housing 110 can have a closed, flat upper structure. After it is installed into the polishing pad 11, the upper surface of the housing 110 can be flush with the upper surface of the polishing pad 11, thereby avoiding damage to the surface flatness of the polishing pad 11 by the eddy current endpoint detection device and facilitating the smooth progress of the polishing process.

[0041] Back Figure 2 It can be seen that the housing 110 also includes a fixing part 112, which is disposed at the other end of the housing 110 opposite to the PCB board 120 (e.g., Figure 2 The lower end of the housing 110 (e.g., protruding outward along the axial direction of the housing 110 away from the PCB board 120) can be configured to fix the housing 110 to a preset position, such as fixing it to a preset recessed mounting hole in the polishing table, so that the wafer-facing surface of the eddy current endpoint detection device 100 is flush with the wafer-facing surface of the polishing table, so as not to interfere with the polishing operation. In a more specific embodiment, the recessed mounting hole can be set as a stepped hole recessed from the wafer-facing surface of the polishing table, or other mounting holes that can appropriately accommodate the eddy current endpoint detection device 100. In a preferred embodiment, the housing 110 can be filled with epoxy resin, which has good insulation, mechanical properties and chemical stability, and can help reduce the noise of the eddy current endpoint detection device 100 and improve its resolution, thereby making effective and accurate endpoint judgment. In optional or alternative embodiments, other suitable noise reduction materials can also be filled into the housing 110. In addition, the housing 110 can be made of heat-insulating material to reduce the impact of changes in the external ambient temperature on the measurement results of the eddy current endpoint detection device 100, further reduce detection noise, and improve the accuracy of endpoint detection.

[0042] Figure 9 It shows Figure 2 A schematic diagram of the circuit principle of the eddy current endpoint detection device 100. Figure 10 It shows Figure 2 The working principle diagram of the eddy current endpoint detection device. Figure 9In the middle, the dashed box is a schematic diagram of the principle of the resonant circuit 121, which includes the inductive coil inductance L, the equivalent impedance Z of the inductive coil 121 and the conductive metal film on the wafer when resonant mutual inductance, and the parallel resonant capacitor C. The dashed box outside is the driving circuit, which includes the signal generating driver M and the high-precision sampling resistor R. The signal generating driver M can generate an alternating current signal to drive the resonant circuit 121. i1 is the current of the driving circuit, and i2 is the current of the resonant circuit 121. In combination Figure 10 It can be seen that when the resonant circuit 121 resonates, the eddy current end point detection device 100 is close to the wafer W, which can excite an alternating induction magnetic field in the metal film on the wafer W (as shown by the dashed arrow at the wafer W). The mutual inductance effect caused by the metal film of different thicknesses makes the inductive current i2 of the resonant circuit 121 change and energy loss occurs. The real-time thickness of the conductive metal film can be measured or monitored by collecting the measurement signal representing the change information or energy loss value of the current i2 of the resonant circuit 121, and then judging whether the polishing endpoint is reached based on the size of the real-time thickness of the metal film. The conductive metal film may, for example, be a film of a metal such as cobalt, tungsten, etc. with low resistivity.

[0043] Figure 11 A flowchart of a method of polishing endpoint detection according to an embodiment of the present application is shown, which can be performed by the eddy current end point detection device 100. Figure 2 Specifically, the method can include:

[0044] S1: collecting a measurement signal in real time by using the eddy current end point detection device, which may, for example, be the current i2 of the resonant circuit 121;

[0045] S2: calculating and monitoring the real-time thickness of the metal film on the wafer during the polishing process based on the collected measurement signal; and

[0046] S3: judging whether the real-time thickness of the metal film reaches a preset thickness. If yes, controlling the chemical mechanical polishing device 10 to stop the polishing operation. If no, continuing to perform step S1.

[0047] The process of collecting the measurement signal in step S1 can be performed by the signal collection module 131 of the control module 13. The measurement signal can be communicated to the signal analysis module 132. The preset thickness in step S3 can be set in advance in the signal analysis module 132, and the judgment process is performed via the signal analysis module 132.

[0048] In addition, in step S3, when it is determined that the real-time thickness of the metal film reaches the preset thickness, the chemical mechanical polishing device 10 can be directly controlled to stop the polishing operation via the control module 130, or an end point signal can be sent to other operation controllers in communication connection with the control module 130 via the control module 130, and the other operation controllers control the chemical mechanical polishing device 10 to perform the action of stopping the polishing operation.

[0049] In an optional or alternative embodiment, the end point judgment criterion in step S3 can also adopt the thickness difference value, for example, a measurement step of the initial thickness of the metal film on the wafer can be added before step S1, and in step S3, whether the polishing end point is reached is determined by whether the difference between the initial thickness of the metal film and the real-time thickness of the metal film reaches the preset thickness difference. By monitoring the thickness difference of the metal film, the error in the measurement process can be eliminated to some extent, thereby improving the accuracy of the end point judgment.

[0050] The eddy current end point detection device and the chemical mechanical polishing device according to the present application have at least the following beneficial effects:

[0051] (1) By integrating the induction coil in the PCB, the manufacturing precision and integration efficiency of the induction coil are improved by using precise equipment or fine manufacturing methods in the PCB manufacturing process, the manufacturing error and detection deviation of the traditional winding coil are avoided, and the accuracy and consistency of the eddy current end point detection device are improved;

[0052] (2) Through the matching structure design of the PCB and the blocking ring for positioning the PCB, the positioning accuracy, assembly efficiency and use stability of the PCB are improved, and the manufacturing efficiency and action stability of the eddy current end point detection device are improved;

[0053] (3) By using epoxy resin for packaging, the influence of external environmental factors on the eddy current end point detection device is reduced, the detection noise of the eddy current end point detection device is reduced, the resolution capability is improved, and the effectiveness and accuracy of the end point detection are improved;

[0054] (4) The use of thermal insulation materials to manufacture the shell reduces the influence of the self-heating of the eddy current end point detection device and the change of the environmental temperature on the detection result, further improves the stability and detection precision of the eddy current end point detection device; and

[0055] (5) The improvement of the detection precision of the eddy current end point detection device is conducive to the timely and accurate stop of the polishing operation of the chemical mechanical polishing device, the accurate and effective wafer planarization operation, the improvement of the working efficiency of the chemical mechanical polishing device, and the improvement of the wafer planarization quality.

[0056] The above embodiments are only used for describing the present application, and are not intended to limit the present application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application. Therefore, all equivalent technical solutions belong to the scope of the present application, and the patent protection scope of the present application should be defined by the claims.

Claims

1. An eddy current endpoint detection device for use in chemical mechanical polishing equipment for processing wafers, characterized in that, The eddy current endpoint detection device includes: A housing, the housing being made of thermal insulation material and filled with epoxy resin; A PCB board, which is encapsulated in the housing, includes a resonant circuit integrated therein, the resonant circuit including an induction coil integrated between two opposing surface layers of the PCB board; A retaining ring is nested and fixed to the inner wall of the housing. The retaining ring has a positioning part. The PCB board is mounted to the retaining ring based on the positioning part and is disposed at the end of the housing via the retaining ring; and A control module, which is electrically connected to the PCB board, detects the thickness of the metal film on the wafer facing the PCB board based on the change information of the current signal in the resonant circuit or the energy loss value.

2. The eddy current endpoint detection device according to claim 1, characterized in that, The eddy current endpoint detection device includes a control board encapsulated in the housing, and the control module is disposed on the control board.

3. The eddy current endpoint detection device according to claim 2, characterized in that, The control module includes a signal acquisition module and a signal analysis module that are electrically connected. The signal acquisition module is configured to acquire the current signal in the resonant circuit, and the signal analysis module is configured to obtain the thickness information of the metal film based on the current signal.

4. The eddy current endpoint detection device according to claim 1, characterized in that, The housing is constructed in a cylindrical shape, the PCB board is constructed as a circular plate or a portion of a circular plate that matches the inner diameter of the housing, and the induction coil is wound in a plane parallel to the PCB board.

5. The eddy current endpoint detection device according to any one of claims 1-4, characterized in that, The induction coil is wound in a circular, elliptical, or rectangular shape.

6. The eddy current endpoint detection device according to claim 5, characterized in that, The housing includes a fixing part disposed at the other end of the housing opposite to the PCB board, and the fixing part is configured to fix the housing to a preset position.

7. A chemical mechanical polishing apparatus, characterized in that, The chemical mechanical polishing equipment includes a polishing table for polishing wafers and an eddy current endpoint detection device according to any one of claims 1-6, wherein the eddy current endpoint detection device is disposed in the polishing table to detect the thickness of the metal film on the wafer.

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