Method, apparatus and storage medium for thickness-compensated eddy current testing

Abstract

This application provides a thickness-compensated eddy current detection method, apparatus, and storage medium, applied to a chemical mechanical polishing (CMP) apparatus. The method includes: acquiring a first sensing signal from the eddy current sensor when the wafer moves to the detection area of ​​the eddy current sensor, wherein the eddy current sensor is disposed within a polishing disk included in the CMP apparatus, and a polishing pad for polishing a metal layer on the wafer is disposed on the top surface of the polishing disk; acquiring a second sensing signal from the eddy current sensor when a dressing head included in the CMP apparatus sweeps across the detection area; determining a first thickness value of the area on the polishing pad opposite to the eddy current sensor based on the second sensing signal; and determining the thickness of the metal layer on the wafer based on the first sensing signal and the first thickness value. The thickness-compensated eddy current detection method provided in this application can improve the detection accuracy of the metal layer thickness on the wafer.

Description

[0001] This application is a divisional application of the invention patent application filed on November 15, 2024, with application number 202411628959X. Technical Field

[0002] This application relates to the field of semiconductor manufacturing technology, and in particular to a thickness-compensated eddy current detection method, apparatus, and storage medium. Background Technology

[0003] Integrated circuits (ICs) are the core and lifeline of the information technology industry. ICs are generally formed by successively depositing conductive layers, semiconductor layers, or insulating layers on a silicon wafer. This results in a thin film of filler layers deposited on the wafer surface. During the manufacturing process, the filler layers need to be continuously planarized until a patterned top surface is exposed, in order to form conductive paths between the raised patterns.

[0004] Chemical Mechanical Polishing (CMP) is the preferred planarization process in IC manufacturing. In CMP, excessive or insufficient material removal can lead to degraded electrical properties or even device failure. To improve the controllability of the CMP process, enhance product stability, reduce defect rates, and ensure uniform production across all wafers, Endpoint Detection (EPD) technology for CMP has been developed.

[0005] In CMP endpoint inspection of metals, eddy current testing is the most commonly used method. Its output is a voltage signal. Experiments have shown that the magnitude of this voltage signal is related to the thickness of the metal layer on the wafer being measured, as well as the distance between the eddy current sensor and the metal layer. This distance is called the lift-off distance, which is related to the thickness of the polishing pad in the chemical mechanical polishing equipment. The relationship between the metal layer thickness and the voltage value differs at different lift-off distances. In actual processing, the polishing pad is between the sensor and the wafer being polished; therefore, the thickness of the polishing pad is the lift-off distance. The thickness of the polishing pad decreases as processing progresses, meaning the lift-off distance decreases. This changes the relationship between the voltage value and the metal layer thickness, leading to increased measurement error and affecting the polishing effect. Summary of the Invention

[0006] In view of this, this application provides a thickness-compensated eddy current detection method, apparatus, and storage medium to at least partially solve the above-mentioned problems.

[0007] According to a first aspect of this application, a thickness-compensated eddy current detection method is provided, applied to a chemical mechanical polishing (CMP) apparatus. The method includes: acquiring a first sensing signal from the eddy current sensor when the wafer moves to the detection area of ​​the eddy current sensor, wherein the eddy current sensor is disposed within a polishing disk included in the CMP apparatus, and the top surface of the polishing disk is provided with a polishing pad for polishing a metal layer on the wafer; acquiring a second sensing signal from the eddy current sensor when a dressing head included in the CMP apparatus sweeps across the detection area; determining a first thickness value of the area on the polishing pad opposite to the eddy current sensor based on the second sensing signal; and determining the thickness of the metal layer on the wafer based on the first sensing signal and the first thickness value.

[0008] According to a second aspect of this application, a chemical mechanical polishing (CMP) apparatus is provided, comprising: a polishing disc, a polishing pad, a trimming head, a support head, a liquid supply module, and a control module. The support head is used to support a wafer so that the wafer abuts against the polishing pad. The polishing disc includes an eddy current sensor disposed within the polishing disc. A polishing pad for polishing a metal layer on the wafer is disposed on the top surface of the polishing disc. The liquid supply module is used to supply polishing liquid between the wafer and the polishing pad. The trimming head is used to trim the polishing pad. The control module is used to acquire a first sensing signal from the eddy current sensor when the wafer moves to the detection area of ​​the eddy current sensor, acquire a second sensing signal from the eddy current sensor when the trimming head sweeps across the detection area, and determine a first thickness value of the area on the polishing pad opposite to the eddy current sensor based on the second sensing signal.

[0009] According to a third aspect of this application, an eddy current detection device based on polishing pad thickness compensation is provided, comprising: a sensing signal acquisition module, configured to acquire a first sensing signal of the eddy current sensor when the wafer moves to the detection area of ​​the eddy current sensor, wherein the eddy current sensor is disposed within a polishing disk included in a chemical mechanical polishing apparatus, and a polishing pad for polishing a metal layer on the wafer is disposed on the top surface of the polishing disk; and to acquire a second sensing signal of the eddy current sensor when a dressing head included in the chemical mechanical polishing apparatus sweeps across the detection area; a first thickness value determination module, configured to determine a first thickness value of the area on the polishing pad opposite to the eddy current sensor based on the second sensing signal; and a metal layer thickness determination module, configured to determine the thickness of the metal layer on the wafer based on the first sensing signal and the first thickness value.

[0010] According to a fourth aspect of this application, an electronic device is provided, comprising: a processor, a memory, a communication interface, and a communication bus, wherein the processor, the memory, and the communication interface communicate with each other via the communication bus; the memory is used to store at least one executable instruction, the executable instruction causing the processor to perform an operation corresponding to the method described in the first aspect.

[0011] According to a fifth aspect of this application, a computer storage medium is provided having a computer program stored thereon that, when executed by a processor, implements the method described in the first aspect.

[0012] According to a sixth aspect of this application, a computer program product is provided, including computer instructions that instruct a computing device to perform the method as described in the first aspect.

[0013] According to the thickness-compensated eddy current detection method provided in this application, when the wafer moves to the detection area of ​​the eddy current sensor, a first sensing signal of the eddy current sensor is acquired, and when the trimming head sweeps across the detection area, a second sensing signal of the eddy current sensor is acquired. The first thickness of the area on the polishing pad opposite to the eddy current sensor is determined based on the second sensing signal. Thus, the thickness of the metal layer on the wafer can be determined based on the first thickness and the first sensing signal. Since the thickness of the polishing pad is considered when determining the thickness of the metal layer, i.e., the wafer lift-off height is taken into account, the detected metal layer thickness on the wafer is more accurate compared to the prior art which does not consider the lift-off height. Furthermore, since the thickness of the polishing pad is detected based on the eddy current sensor mounted on the polishing pad, there is no need to install an additional eddy current sensor on the trimming head, preventing damage to the eddy current sensor by the polishing fluid. Also, since the detected area is the thickness of the area opposite to the eddy current sensor, the detected wafer lift-off height is more accurate compared to the average thickness of the polishing pad, thus determining the thickness of the metal layer on the wafer more accurately. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0015] Figure 1 This is a flowchart of a thickness-compensated eddy current detection method provided in this application;

[0016] Figure 2 This is a schematic diagram of a chemical mechanical polishing process for a wafer provided in this application;

[0017] Figure 3 This is a schematic diagram of a dressing head dressing and polishing pad provided in this application;

[0018] Figure 4 This is a schematic diagram of a mapping relationship provided in this application;

[0019] Figure 5 This is a schematic diagram of a detection area provided in this application;

[0020] Figure 6 This is a schematic diagram of a chemical mechanical polishing device provided in this application;

[0021] Figure 7 This is a schematic diagram of the structure of an electronic device provided in this application.

[0022] 200. Chemical mechanical polishing equipment; 201. Polishing pad; 202. Dressing head; 203. Polishing disc; 2031. Eddy current sensor; 204. Bearing head; 205. Liquid supply module; 206. Control module; 300. Wafer; 400. Annular area; 702. Processor; 704. Communication interface; 706. Memory; 708. Communication bus; 710. Program. Detailed Implementation

[0023] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art should fall within the scope of protection of this application.

[0024] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0025] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0026] The eddy current detection method for thickness compensation provided in this application is illustrated below through specific embodiments:

[0027] Figure 1 This is a flowchart of a thickness-compensated eddy current detection method provided in this application. This method is applied to chemical mechanical polishing equipment, such as... Figure 1 As shown, the eddy current detection method for polishing pad thickness compensation includes the following steps 101 to 104:

[0028] Step 101: When the wafer moves to the detection area of ​​the eddy current sensor, acquire the first sensing signal of the eddy current sensor.

[0029] An eddy current sensor is installed inside a polishing disc in a chemical mechanical polishing (CMP) device. The top surface of the polishing disc is provided with a polishing pad for polishing the metal layer on the wafer. Figure 2 This is a schematic diagram of a chemical mechanical polishing process for wafer 300 provided in this application, as shown below. Figure 2 As shown, when the chemical mechanical polishing (CMP) equipment polishes the wafer 300, the equipment body rotates, and the wafer 300 rotates under the action of the bearing head and moves radially along the polishing pad of the CMP equipment. This allows for CMP polishing of the wafer 300 via the polishing pad 201. Since the eddy current sensor is located within the polishing pad of the CMP equipment, and the polishing pad 201 is located on the top surface of the polishing pad, and the wafer 300 moves radially along the polishing pad 201, a first sensing signal from the eddy current sensor is acquired when the wafer 300 reaches the detection area of ​​the eddy current sensor. It should be noted that the surface of the wafer 300 has a layer of metallic material, such as copper, tungsten, aluminum, tantalum, or titanium. The thickness of the metallic layer on the wafer 300 can range from 0.01 μm to 50 μm.

[0030] It should also be noted that the detection principle of the eddy current sensor is that when the wafer moves to the detection area of ​​the eddy current sensor, the metal layer on the wafer surface will generate an eddy current effect, which will cause the magnetic field generated by the eddy current sensor to change. The thickness of the metal layer is then measured based on the change in the magnetic field.

[0031] Step 102: When the dressing head of the chemical mechanical polishing equipment sweeps across the detection area, acquire the second sensing signal of the eddy current sensor.

[0032] During chemical mechanical polishing of wafers, the polishing pads wear down, so a trimming head is needed to trim the polishing pads in real time. In one example, the wafer is polished on the left half of the polishing pad, and the trimming head trims the polishing pad on the right half. When the trimming head sweeps across the detection area, a second sensing signal from the eddy current sensor is acquired. Since there is metal inside the trimming head, the eddy current sensor can detect the metal inside the trimming head and generate a second sensing signal.

[0033] Step 103: Determine the first thickness value of the area on the polishing pad opposite to the eddy current sensor based on the second sensing signal.

[0034] Based on the second induction signal generated by the eddy current sensor, the distance between the eddy current sensor and the dressing head is determined. It should be understood that since the dressing head dresses the polishing pad, the polishing pad is set on the polishing disk, and the eddy current sensor is set inside the polishing disk, the distance between the eddy current sensor and the dressing head is the first thickness value of the area on the polishing pad opposite to the eddy current sensor.

[0035] It should be understood that, since the eddy current sensor acquires a second sensing signal and determines a first thickness value of the area opposite the eddy current sensor based on the second sensing signal when the dressing head of the chemical mechanical polishing equipment sweeps across the detection area, the area opposite the polishing pad and the eddy current sensor is at least partially located within the detection area. The radius and angle of the detection area on the polishing pad can be predetermined.

[0036] Step 104: Determine the thickness of the metal layer on the wafer based on the first sensing signal and the first thickness value.

[0037] The thickness of the metal layer on the wafer is determined based on the first sensing signal and the first thickness value. In one example, the mapping relationship between the sensing signal and the metal layer thickness can be determined based on the first thickness value, and the thickness of the metal layer on the wafer can be determined based on the mapping relationship and the first sensing signal.

[0038] In this application, when the wafer moves to the detection area of ​​the eddy current sensor, a first sensing signal from the eddy current sensor is acquired, and a second sensing signal from the eddy current sensor is acquired when the trimming head sweeps across the detection area. The first thickness of the area on the polishing pad opposite to the eddy current sensor is determined based on the second sensing signal. Thus, the thickness of the metal layer on the wafer can be determined based on the first thickness and the first sensing signal. Since the thickness of the polishing pad, i.e., the wafer lift-off height, is considered when determining the metal layer thickness, compared to the prior art which does not consider the lift-off height, the detected metal layer thickness on the wafer is more accurate because the influence of the lift-off height on the sensing signal generated by the eddy current sensor is taken into account. Furthermore, since the thickness of the polishing pad is detected based on the eddy current sensor mounted on the polishing pad, there is no need to install an additional eddy current sensor on the trimming head, saving costs and preventing damage to the eddy current sensor by the polishing fluid. Moreover, since the thickness detection area is the thickness of the area on the polishing pad opposite to the eddy current sensor, the detected wafer lift-off height is more accurate compared to the average thickness of the polishing pad, thus determining a more accurate metal layer thickness on the wafer.

[0039] In one possible implementation, when determining the first thickness value of the area on the polishing pad opposite to the eddy current sensor based on the second sensing signal, the positional relationship between the dressing surface of the dressing head and the metal flange in the dressing head can be obtained, wherein the dressing surface is in contact with the polishing pad and is used to dress the polishing pad; the distance between the eddy current sensor and the metal flange is determined based on the second sensing signal; and the first thickness value is determined based on the distance and positional relationship between the eddy current sensor and the metal flange.

[0040] In one example, Figure 3 This is a schematic diagram of a dressing head dressing and polishing pad provided in this application, as shown. Figure 3 As shown, the trimming head 202 trims the polishing pad 201 through the trimming surface that contacts the polishing pad 201.

[0041] Obtain the positional relationship between the dressing surface and the metal flange on the dressing head. This positional relationship is fixed and will not change with the rotation of the polishing pad or the movement of the dressing head. The positional relationship between the dressing surface and the metal flange on the dressing head is a fixed property during the manufacturing of the dressing head.

[0042] The distance between the eddy current sensor and the metal flange of the dressing head is determined based on the signal strength of the second induction signal. It should be understood that the eddy current effect generated by the eddy current sensor and the metal flange in the dressing head causes a change in the magnetic field generated by the eddy current sensor. Based on the change in the magnetic field, i.e. the second induction signal, the distance between the eddy current sensor and the metal flange can be determined.

[0043] Based on the distance between the eddy current sensor and the metal flange and the positional relationship between the dressing surface and the metal flange on the dressing head, the first thickness of the area on the dressing pad opposite to the eddy current sensor is determined. Specifically, the order from the eddy current sensor to the metal flange on the dressing plate is: eddy current sensor, dressing pad, dressing surface in contact with the dressing pad, and metal flange. Therefore, knowing the positional relationship between the dressing surface and the metal flange, and knowing the relationship between the eddy current sensor and the metal flange, the first thickness of the area on the dressing pad opposite to the eddy current sensor can be determined.

[0044] It should be noted that the two steps of determining the distance between the eddy current sensor and the metal flange based on the second sensing signal and obtaining the positional relationship between the dressing surface of the dressing head and the metal flange in the dressing head are not in any particular order. Either step can be performed first, or the two steps can be performed simultaneously, which is not limited here.

[0045] Optionally, the positional relationship between the eddy current sensor and the dressing disc surface can also be obtained, and then the first thickness can be determined based on the positional relationship between the eddy current sensor and the dressing disc surface, the distance between the eddy current sensor and the metal flange, and the positional relationship between the dressing surface and the metal flange in the dressing head. This will not be elaborated further here.

[0046] In this application, the positional relationship between the dressing surface of the dressing head and the metal flange in the dressing head is obtained, and the distance between the eddy current sensor and the metal flange is determined based on the second sensing signal. Thus, based on the distance between the eddy current sensor and the metal flange and the positional relationship between the dressing surface and the metal flange, the first thickness of the area on the dressing pad opposite to the eddy current sensor is determined, realizing the detection of the thickness of the polishing pad by the eddy current sensor. Since the thickness of the polishing pad is detected by the eddy current sensor set on the polishing disk, there is no need to set an additional eddy current sensor on the dressing head, which can prevent the polishing fluid from damaging the eddy current sensor. Furthermore, since the detected area is the thickness of the area opposite to the eddy current sensor, the detected wafer lift-off height is more accurate compared to the average thickness of the polishing pad, and the thickness of the metal layer on the wafer is determined more accurately.

[0047] In one possible implementation, the relative area between the polishing pad and the eddy current sensor is defined as a second thickness. A first mapping relationship between the thickness of the metal layer and the third sensing signal output by the eddy current sensor is determined based on multiple metal layers of different thicknesses. The thickness of the polishing pad is changed, and multiple second mapping relationships between the thickness of the metal layer and the fourth sensing signal output by the eddy current sensor are determined for different thicknesses of the polishing pad. A signal conversion formula is determined based on the first mapping relationship and the multiple second mapping relationships. Based on this, when determining the thickness of the metal layer on the wafer according to the first sensing signal and the first thickness value, the thickness of the metal layer can be determined according to the first sensing signal, the first thickness value, and the signal conversion formula.

[0048] Let the relative area between the polishing pad and the eddy current sensor be the second thickness. Multiple wafers with different metal layer thicknesses are placed in the detection area. Different third sensing signals are obtained from the eddy current sensors for wafers with different metal layer thicknesses. For example, when the relative area between the polishing pad and the eddy current sensor is of thickness m1 to mn, n wafers with metal layer thicknesses m1 to mn are placed in the detection area, and n third sensing signals are determined for each of the n wafers with metal layer thicknesses m1 to mn. This establishes a first mapping relationship between the metal layer thickness and the third sensing signal.

[0049] After determining the first mapping relationship, the size of the second thickness is changed to determine multiple second mapping relationships between the thickness of the metal layer and the fourth sensing signal output by the eddy current sensor when the polishing pad has different thicknesses. For example, when the thickness of the relative area between the polishing pad and the eddy current sensor is h2 to h(t+1), n ​​fourth sensing signals output by the eddy current sensor corresponding to n wafers with metal layer thicknesses of m1 to mn are determined. Thus, t second mapping relationships can be determined. Different second mapping relationships correspond to different thicknesses of the relative area between the polishing pad and the eddy current sensor.

[0050] In one example, Figure 4 This is a schematic diagram of a mapping relationship provided in this application. The first mapping relationship or the second mapping relationship, that is, the mapping relationship between the thickness of the metal layer on the wafer and the value of the induced signal output by the eddy current sensor (e.g., the intensity of the induced signal), can be as follows: Figure 4 As shown.

[0051] The signal conversion formula is determined based on the first mapping relationship and multiple second mapping relationships. The signal conversion formula can indicate the relationship between the polishing pad thickness, the eddy current sensor signal and the wafer metal layer thickness. Thus, when determining the thickness of the metal layer on the wafer, the thickness of the metal layer on the wafer can be determined based on the first sensing signal, the thickness of the area on the polishing pad opposite to the eddy current sensor and the signal conversion formula.

[0052] In this application, a second thickness is set on the polishing pad. A first mapping relationship between the metal layer thickness and the third sensing signal output by the eddy current sensor is determined. Then, the thickness of the polishing pad is changed multiple times, and multiple second mapping relationships between the metal layer thickness and the fourth sensing signal output by the eddy current sensor are determined for different polishing pad thicknesses. Thus, a signal conversion formula can be determined based on the first mapping relationship and the multiple second mapping relationships. The thickness of the metal layer on the wafer can be determined based on the signal conversion formula, the first sensing signal, and the first thickness, thereby realizing the detection of the metal layer thickness. Since the signal conversion is performed based on the determined signal conversion formula, it is not necessary to determine the signal conversion formula in real time for each detection, which can improve the efficiency of metal layer thickness detection.

[0053] In one possible implementation, when determining the signal conversion formula based on the first mapping relationship and multiple second mapping relationships, numerical fitting can be performed on the first mapping relationship and multiple second mapping relationships to determine the third mapping relationship between the mapping coefficients in the first mapping relationship and the thickness of the polishing pad. The mapping coefficients in the first mapping relationship can be corrected based on the third mapping relationship to obtain the signal conversion formula.

[0054] Numerical fitting is performed on the first mapping relationship and multiple second mapping relationships to determine the third mapping relationship between the mapping coefficients in the first mapping relationship and the thickness of the polishing pad. The first and second mapping relationships can be first-order, second-order, or third-order functions. The following explanation uses a second-order function as an example.

[0055] In one example, the first and second mapping relationships can be expressed as: T(x) = Ax^2 + Bx + C, where T(x) represents the induced signal output by the eddy current sensor, x represents the thickness of the metal layer on the wafer, and ABC represent the mapping coefficients. The first mapping relationship is the mapping relationship between the induced signal generated by the eddy current sensor when the second thickness is h1 and the thickness of the metal layer on the wafer, that is, T1(x) = A1x^2 + B1x + C1 when the second thickness is h1. Multiple second mapping relationships are respectively for the induced signals generated by the eddy current sensor when the second thickness is h2 to h(t+1) and the thickness of the metal layer on the wafer, that is, T2(x) = A2x^2 + B2x + C2 when the second thickness is h2, and T3(x) = A3x + C2 when the second thickness is h3. x^2+B3x+C3……,When the second thickness is h(t+1), T(t+1)(x)=A(t+1)x^2+B(t+1)x+C(t+1). By numerically fitting the first mapping relationship with multiple second mapping relationships, the third mapping relationship between the mapping coefficient and the polishing pad thickness h can be determined. For example: A=g1(h), B=g2(h), C=g3(h), where g(h) represents a function with h as the unknown. By correcting the mapping coefficients in the first mapping relationship through the third mapping relationship, the signal conversion formula is obtained. The signal conversion formula is: T(x)=g1(h)x^2+g2(h)x+g3(h). Thus, by substituting the first thickness h and the first induced signal T into the signal conversion formula, x in the formula can be obtained, that is, the thickness of the metal layer on the wafer can be determined.

[0056] In this application, numerical fitting is performed on the first mapping relationship and multiple second mapping relationships to determine the third mapping relationship between the mapping coefficients in the first mapping relationship and the thickness of the polishing pad. The mapping coefficients are corrected according to the third mapping relationship, thereby obtaining the signal conversion formula. Since the third mapping relationship between the mapping coefficients and the thickness of the polishing pad is relatively accurate due to the numerical fitting of multiple mapping relationships, different mapping coefficients can be determined according to the thickness of the polishing pad during use. This allows the thickness of the polishing pad to be considered when detecting the thickness of the metal layer on the wafer. Because the influence of the thickness of the polishing pad on the sensing signal of the eddy current sensor is taken into account, the detected thickness of the metal layer on the wafer is more accurate.

[0057] In one possible implementation, the eddy current sensor includes a first induction coil and a second induction coil. When the eddy current sensor rotates with the polishing disk to below the moving wafer, a first induction signal is acquired through the first induction coil, and when the eddy current sensor rotates with the polishing disk to below the dressing head that sweeps across the detection area, a second induction signal is acquired through the second induction coil.

[0058] The eddy current sensor may include a first induction coil and a second induction coil. The sensing ranges of the first induction coil and the second induction coil may be different. It should be understood that the eddy current sensor rotates together with the polishing disc. Since the distance between the metal layer on the wafer and the eddy current sensor is smaller than the distance between the eddy current sensor and the metal flange on the dressing head, when the eddy current sensor rotates to below the wafer, a first sensing signal is obtained through the first induction coil with a smaller range. When it rotates to below the dressing surface of the dressing head, a second sensing signal is obtained through the second induction coil with a larger range.

[0059] In this application, the eddy current sensor includes a first induction coil and a second induction coil, thereby obtaining a first induction signal through the first induction coil and a second induction signal through the second induction coil. Thus, the first induction signal and the second induction signal can be obtained simultaneously through different induction coils. Furthermore, since the first induction coil and the second induction coil can be set with different ranges, it can be applied to signal sensing at different distances.

[0060] In one possible implementation, the eddy current sensor includes a third induction coil, and the method further includes: acquiring a first induction signal or a second induction signal generated by the third induction coil according to a pre-set measurement timing sequence, wherein the measurement timing sequence is set at least according to the rotational speed of the polishing disc.

[0061] The eddy current sensor may also include only a third induction coil. The induction signal generated by the third induction coil can be collected according to a preset measurement sequence. For example, when the eddy current sensor rotates to the position below the moving wafer as the polishing disk rotates, the first induction signal generated by the third induction coil is collected. When the eddy current sensor rotates to the position below the dressing head that sweeps through the detection area as the polishing disk rotates, the second induction signal generated by the third induction coil is collected.

[0062] It should be noted that the rotation speed determines the time it takes for the eddy current sensor to rotate to the corresponding position each time (e.g., to rotate to the underside of the moving wafer, or to rotate to the underside of the trimming head that sweeps across the detection area). In other words, the faster the rotation speed, the shorter the time required to rotate to the corresponding position. Therefore, the measurement timing can be set at least according to the rotation speed of the polishing pad.

[0063] In one example, the currently acquired induction signal can also be determined as either the first or second induction signal based on the signal strength of the induction signal generated by the third induction coil. It should be understood that since the distance between the metal layer on the wafer and the eddy current sensor is less than the distance between the eddy current sensor and the metal flange on the trimming head, the signal strength of the second induction signal is less than that of the first induction signal for the third induction coil. Therefore, the induction signal generated by the eddy current sensor can be continuously acquired, and the induction signal with higher intensity can be identified as the first induction signal, while the induction signal with lower intensity can be identified as the second induction signal.

[0064] In this application, the eddy current sensor includes a third induction coil. By means of a pre-set measurement timing sequence, the first induction signal or the second induction signal generated by the third induction coil is acquired. Since it only includes one induction coil, the cost is lower compared with the scheme of setting two induction coils in the above embodiments.

[0065] In one possible implementation, the trimming head is controlled to sweep across the detection area based on the movement trajectory of the wafer on the polishing pad, so that the trimming head is located in the detection area when the wafer is located in the detection area, wherein the detection area is a ring-shaped area, and the wafer and the trimming head are located in different areas of the ring-shaped area.

[0066] Because the eddy current sensor is mounted on the polishing pad and rotates with it during operation, a ring-shaped detection area is formed on the polishing pad. Figure 5 This is a schematic diagram of a detection area provided in this application, such as... Figure 5 As shown, the detection area is an annular region 400. When the wafer 300 moves to the annular region 400, the trimming head 202 is controlled to sweep across the annular region 400. The control logic is to control the trimming head 202 to sweep across the annular region according to the movement trajectory of the wafer 300 on the polishing pad 201. This way, the trimming head 202 is also located in the annular region 400 every time the wafer 300 moves to the annular region 400. Thus, the second sensing signal can be collected after the first sensing signal is collected, so that the acquisition time of the first sensing signal and the second sensing signal is short.

[0067] It should be noted that, as Figure 2 As shown, the wafer 300 moves radially along the polishing pad 201. Therefore, the time it takes for the wafer to pass through the detection area (ring area) can be determined based on the wafer's movement trajectory. This allows the trimming head to be controlled to sweep across the detection area, ensuring that the trimming head is simultaneously located in the detection area when the wafer is in the detection area.

[0068] In this application, the trimming head is controlled to sweep across the detection area according to the movement trajectory of the wafer on the polishing pad, so that the trimming head is located in the detection area when the wafer is located in the detection area. This allows the second sensing signal to be acquired after the first sensing signal is acquired, making the acquisition time of the first sensing signal and the second sensing signal shorter. Therefore, after determining the first thickness based on the second sensing signal, the thickness of the metal layer on the wafer can be determined more accurately based on the first thickness and the first sensing signal.

[0069] Figure 6 This is a schematic diagram of a chemical mechanical polishing apparatus 200 provided in this application, as shown below. Figure 6 As shown, the chemical mechanical polishing (CMP) equipment 200 may include: a polishing disc 203, a polishing pad 201, a dressing head 202, a support head 204, a liquid supply module 205, and a control module 206. The support head 204 is used to support the wafer 300 so that the wafer 300 abuts against the polishing pad 201. The polishing disc 203 includes an eddy current sensor 2031, which is disposed within the polishing disc 203. The top surface of the polishing disc 203 is provided with a polishing pad 201 for polishing the metal layer on the wafer 300. The liquid supply module 205... Module 205 is used to supply polishing fluid between wafer 300 and polishing pad 201. Dressing head 202 is used to dress polishing pad 201. Control module 206 is used to acquire a first sensing signal of eddy current sensor 2031 when wafer 300 runs to the detection area of ​​eddy current sensor 2031, acquire a second sensing signal of eddy current sensor 2031 when dressing head 202 sweeps across the detection area, and determine a first thickness value of the area on polishing pad 201 opposite to eddy current sensor 2031 based on the second sensing signal.

[0070] The control module 206 is used to obtain the positional relationship between the dressing surface of the dressing head 202 and the metal flange in the dressing head 202, wherein the dressing surface is in contact with the polishing pad 201 and the dressing surface is used to dress the polishing pad 201. Based on the second sensing signal, the distance between the eddy current sensor 2031 and the metal flange is determined, and based on the distance and positional relationship between the eddy current sensor 2031 and the metal flange, the first thickness is determined.

[0071] In one possible implementation, the control module 206 is configured to, when the relative area between the polishing pad 201 and the eddy current sensor 2031 is at a second thickness, determine a first mapping relationship between the thickness of the metal layer and the third sensing signal output by the eddy current sensor 2031 based on multiple metal layers of different thicknesses, change the thickness of the polishing pad 201, determine multiple second mapping relationships between the thickness of the metal layer and the fourth sensing signal output by the eddy current sensor 2031 at different thicknesses of the polishing pad 201, determine a signal conversion formula based on the first mapping relationship and the multiple second mapping relationships, and determine the thickness of the metal layer based on the first sensing signal, the first thickness value and the signal conversion formula.

[0072] In one possible implementation, the control module 206 is used to perform numerical fitting on the first mapping relationship and multiple second mapping relationships, determine the third mapping relationship between the mapping coefficients in the first mapping relationship and the thickness of the polishing pad 201, and correct the mapping coefficients in the first mapping relationship according to the third mapping relationship to obtain the signal conversion formula.

[0073] In one possible implementation, the eddy current sensor includes a first induction coil and a second induction coil. The control module 206 is used to acquire a first sensing signal through the first induction coil when the eddy current sensor 2031 rotates with the polishing disk 203 to below the moving wafer 300, and to acquire a second sensing signal through the second induction coil when the eddy current sensor 2031 rotates with the polishing disk 203 to below the trimming head 202 that sweeps through the detection area.

[0074] In one possible implementation, the eddy current sensor 2031 includes a third induction coil and a control module 206 for acquiring a first induction signal or a second induction signal generated by the third induction coil according to a preset measurement timing sequence, wherein the measurement timing sequence is set at least according to the rotational speed of the polishing disc 203.

[0075] In one possible implementation, the control module 206 is used to control the trimming head 202 to sweep across the detection area according to the movement trajectory of the wafer 300 on the polishing pad 201, so that the trimming head 202 is located in the detection area when the wafer 300 is located in the detection area, wherein the detection area is an annular area, and the wafer 300 and the trimming head 202 are located in different areas of the annular area.

[0076] Another embodiment of this application provides an eddy current detection device based on polishing pad thickness compensation, comprising: a sensing signal acquisition module, configured to acquire a first sensing signal of the eddy current sensor when the wafer moves to the detection area of ​​the eddy current sensor, wherein the eddy current sensor is disposed within a polishing disk included in a chemical mechanical polishing (CMP) apparatus, and the top surface of the polishing disk is provided with a polishing pad for polishing a metal layer on the wafer; and a second sensing signal of the eddy current sensor when a dressing head included in the CMP apparatus sweeps across the detection area; a first thickness value determination module, configured to determine a first thickness value of the area on the polishing pad opposite to the eddy current sensor based on the second sensing signal; and a metal layer thickness determination module, configured to determine the thickness of the metal layer on the wafer based on the first sensing signal and the first thickness value.

[0077] Reference Figure 7 The diagram shows a structural schematic of an electronic device according to this application. The specific embodiments of this application do not limit the specific implementation of the electronic device.

[0078] like Figure 7 As shown, the electronic device may include: a processor 702, a communications interface 704, a memory 706, and a communications bus 708.

[0079] in:

[0080] The processor 702, communication interface 704, and memory 706 communicate with each other via communication bus 708.

[0081] Communication interface 704 is used to communicate with other electronic devices or servers.

[0082] The processor 702 is used to execute program 710, which can specifically execute the relevant steps in the above-described embodiment of the eddy current detection method for thickness compensation.

[0083] Specifically, program 710 may include program code that includes computer operation instructions.

[0084] The processor 702 may be a central processing unit (CPU), a graphics processing unit (GPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement this application. The one or more processors included in the intelligent device may be processors of the same type, such as one or more CPUs; one or more GPUs; or they may be processors of different types, such as one or more CPUs, one or more GPUs, and one or more ASICs.

[0085] Memory 706 is used to store program 710. Memory 706 may include high-speed RAM memory, and may also include non-volatile memory, such as at least one disk storage device.

[0086] Specifically, program 710 can be used to cause processor 702 to execute the thickness-compensated eddy current detection method in any of the foregoing embodiments.

[0087] The specific implementation of each step in program 710 can be found in the corresponding steps and units described in any of the aforementioned embodiments of the eddy current detection method with thickness compensation, and will not be repeated here. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the devices and modules described above can be referred to the corresponding process descriptions in the aforementioned method embodiments, and will not be repeated here.

[0088] In this application, when the wafer moves to the detection area of ​​the eddy current sensor, a first sensing signal from the eddy current sensor is acquired, and a second sensing signal from the eddy current sensor is acquired when the trimming head sweeps across the detection area. The first thickness of the area on the polishing pad opposite to the eddy current sensor is determined based on the second sensing signal. Thus, the thickness of the metal layer on the wafer can be determined based on the first thickness and the first sensing signal. Since the thickness of the polishing pad, i.e., the wafer lift-off height, is considered when determining the metal layer thickness, compared to the prior art which does not consider the lift-off height, the detected metal layer thickness on the wafer is more accurate because the influence of the lift-off height on the sensing signal generated by the eddy current sensor is taken into account. Furthermore, since the thickness of the polishing pad is detected based on the eddy current sensor mounted on the polishing pad, there is no need to install an additional eddy current sensor on the trimming head, preventing damage to the eddy current sensor by the polishing fluid. Also, since the detected area is the thickness of the area opposite to the eddy current sensor, the detected wafer lift-off height is more accurate compared to the average thickness of the polishing pad, thus resulting in a more accurate determination of the metal layer thickness on the wafer.

[0089] This application also provides a computer program product, including computer instructions that instruct a computing device to perform an operation corresponding to any of the methods in the above-described plurality of method embodiments.

[0090] It should be noted that, depending on the implementation needs, the various components / steps described in this application can be broken down into more components / steps, or two or more components / steps or parts of the operation of a component / step can be combined into a new component / step to achieve the purpose of this application.

[0091] The methods described above according to this application can be implemented in hardware, firmware, or as software or computer code that can be stored in a recording medium (such as a CD-ROM, RAM, floppy disk, hard disk, or magneto-optical disk), or as computer code originally stored on a remote recording medium or a non-transitory machine-readable medium and subsequently stored on a local recording medium, downloaded via a network. Thus, the methods described herein can be processed by software stored on a recording medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware (such as an ASIC or FPGA). It is understood that the computer, processor, microprocessor controller, or programmable hardware includes storage components (e.g., RAM, ROM, flash memory, etc.) capable of storing or receiving software or computer code that, when accessed and executed by the computer, processor, or hardware, implements the thickness-compensated eddy current detection method described herein. Furthermore, when a general-purpose computer accesses code used to implement the thickness-compensated eddy current detection method shown herein, the execution of the code transforms the general-purpose computer into a dedicated computer for executing the thickness-compensated eddy current detection method shown herein.

[0092] Those skilled in the art will recognize that the units and method steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0093] The above embodiments are only used to illustrate this application and are not intended to limit this application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this application. Therefore, all equivalent technical solutions also fall within the scope of this application, and the patent protection scope of this application should be defined by the claims.

Claims

1. A thickness-compensated eddy current detection method, applied to chemical mechanical polishing equipment, characterized in that, The method includes: When the wafer moves to the detection area of ​​the eddy current sensor, the first sensing signal of the eddy current sensor is acquired. The eddy current sensor is disposed in the polishing disk of the chemical mechanical polishing equipment. The top surface of the polishing disk is provided with a polishing pad for polishing the metal layer on the wafer. When the dressing head included in the chemical mechanical polishing equipment sweeps across the detection area, a second sensing signal from the eddy current sensor is acquired. A first thickness value of the region on the polishing pad opposite to the eddy current sensor is determined based on the second sensing signal; Let the relative area between the polishing pad and the eddy current sensor be the second thickness, and determine the first mapping relationship between the thickness of the metal layer and the third sensing signal output by the eddy current sensor based on the multiple metal layers of different thicknesses. By changing the thickness of the polishing pad, multiple second mapping relationships are determined between the thickness of the metal layer and the fourth sensing signal output by the eddy current sensor when the polishing pad is at different thicknesses. Numerical fitting is performed on the first mapping relationship and multiple second mapping relationships to determine a third mapping relationship between the mapping coefficients in the first mapping relationship and the thickness of the polishing pad; Based on the third mapping relationship, the mapping coefficients in the first mapping relationship are corrected to obtain the signal conversion formula; The thickness of the metal layer is determined based on the first sensing signal, the first thickness value, and the signal conversion formula. The signal conversion formula is: T(x)=g1(h)x^2+g2(h)x+g3(h), where h is the first thickness, T is the first sensing signal, g1(h), g2(h), and g3(h) are the corrected mapping coefficients, and x is the thickness of the metal layer on the wafer.

2. The method according to claim 1, characterized in that, Determining the first thickness value of the region on the polishing pad opposite to the eddy current sensor based on the second sensing signal includes: Obtain the positional relationship between the dressing surface of the dressing head and the metal flange in the dressing head, wherein the dressing surface is in contact with the polishing pad and the dressing surface is used to dress the polishing pad; The distance between the eddy current sensor and the metal flange is determined based on the second sensing signal; The first thickness value is determined based on the distance between the eddy current sensor and the metal flange and the positional relationship.

3. The method according to claim 1, characterized in that, The eddy current sensor includes a first induction coil and a second induction coil, and the method further includes: When the eddy current sensor rotates with the polishing disk to below the moving wafer, the first sensing signal is acquired through the first induction coil, and when the eddy current sensor rotates with the polishing disk to below the dressing head that sweeps across the detection area, the second sensing signal is acquired through the second induction coil.

4. The method according to claim 1, characterized in that, The eddy current sensor includes a third induction coil, and the method further includes: According to a pre-set measurement timing sequence, the first induction signal or the second induction signal generated by the third induction coil is acquired, wherein the measurement timing sequence is set at least according to the rotational speed of the polishing disc.

5. The method according to claim 1, characterized in that, The method further includes: The trimming head is controlled to sweep across the detection area according to the movement trajectory of the wafer on the polishing pad, so that the trimming head is located in the detection area when the wafer is located in the detection area, wherein the detection area is an annular area, and the wafer and the trimming head are located in different areas of the annular area.

6. A chemical mechanical polishing apparatus, characterized in that, include: The system includes a polishing disc, a polishing pad, a trimming head, a support head, a liquid supply module, and a control module. The support head is used to support the wafer so that the wafer abuts against the polishing pad. The polishing disc includes an eddy current sensor disposed within the polishing disc. The top surface of the polishing disc is provided with a polishing pad for polishing the metal layer on the wafer. The liquid supply module is used to supply polishing liquid between the wafer and the polishing pad. The trimming head is used to trim the polishing pad. The control module is used to acquire a first sensing signal of the eddy current sensor when the wafer runs to the detection area of ​​the eddy current sensor, acquire a second sensing signal of the eddy current sensor when the trimming head sweeps across the detection area, and determine a first thickness value of the area on the polishing pad opposite to the eddy current sensor based on the second sensing signal. Let the relative area between the polishing pad and the eddy current sensor be the second thickness. A first mapping relationship is determined between the thickness of the metal layer and the third sensing signal output by the eddy current sensor based on multiple metal layers of different thicknesses. The thickness of the polishing pad is changed, and multiple second mapping relationships are determined between the thickness of the metal layer and the fourth sensing signal output by the eddy current sensor for different thicknesses of the polishing pad. The first mapping relationship and the multiple second mapping relationships are numerically fitted to determine a third mapping relationship between the mapping coefficients in the first mapping relationship and the thickness of the polishing pad. The mapping coefficients in the first mapping relationship are corrected based on the third mapping relationship to obtain a signal conversion formula. The thickness of the metal layer is determined based on the first sensing signal, the first thickness value, and the signal conversion formula. The signal conversion formula is: T(x) = g1(h)x^2 + g2(h)x + g3(h), where h is the first thickness, T is the first sensing signal, g1(h), g2(h), and g3(h) are the corrected mapping coefficients, and x is the thickness of the metal layer on the wafer.

7. The device according to claim 6, characterized in that, The control module is used to obtain the positional relationship between the dressing surface of the dressing head and the metal flange in the dressing head, wherein the dressing surface contacts the polishing pad and is used to dress the polishing pad; the distance between the eddy current sensor and the metal flange is determined according to the second sensing signal; and the first thickness is determined according to the distance between the eddy current sensor and the metal flange and the positional relationship.

8. The device according to claim 6, characterized in that, The eddy current sensor includes a first induction coil and a second induction coil; The control module is configured to acquire the first sensing signal via the first induction coil when the eddy current sensor rotates with the polishing disk to below the moving wafer, and to acquire the second sensing signal via the second induction coil when the eddy current sensor rotates with the polishing disk to below the trimming head that sweeps across the detection area.

9. The device according to claim 6, characterized in that, The eddy current sensor includes a third induction coil; The control module is used to acquire the first induction signal or the second induction signal generated by the third induction coil according to a preset measurement timing sequence, wherein the measurement timing sequence is set at least according to the rotation speed of the polishing disc.

10. The device according to claim 6, characterized in that, The control module is used to control the trimming head to sweep across the detection area according to the movement trajectory of the wafer on the polishing pad, so that the trimming head is located in the detection area when the wafer is located in the detection area, wherein the detection area is an annular area, and the wafer and the trimming head are located in different areas of the annular area.

11. An electronic device, characterized in that, include: The processor, memory, communication interface, and communication bus are provided, wherein the processor, memory, and communication interface communicate with each other via the communication bus. The memory is used to store at least one executable instruction that causes the processor to perform the thickness-compensated eddy current detection method as described in any one of claims 1-5.

12. A computer storage medium, characterized in that, It stores a computer program that, when executed by a processor, implements the eddy current detection method for thickness compensation as described in any one of claims 1-5.

13. A computer program product, characterized in that, Includes computer instructions that instruct a computing device to perform the thickness-compensated eddy current detection method as described in any one of claims 1-5.

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