Metal film thickness online measurement compensation method, film thickness sensor and device

Abstract

The application discloses a metal film thickness online measurement compensation method, a film thickness sensor and equipment, and the method comprises the following steps: obtaining the nth output quantity S of the film thickness sensor for measuring the metal film thickness in a polishing process n ; calculating a sensor temperature drift compensation quantity ΔS sn by using the film thickness sensor temperature t sn and a self temperature drift function at this time; calculating a wafer temperature drift compensation quantity ΔS wn by using the wafer temperature t n‑1 , the (n-1)th measured film thickness d wn and a wafer temperature compensation function at this time; calculating a compensated output quantity S' n , S' n =S n -ΔS sn -ΔS wn ; and obtaining the (n)th measured film thickness d n according to a sensor output function and the compensated output quantity S' n .

Description

[0001] This application is a divisional application of the invention patent application with application number 202310410608.0, filed on April 17, 2023. TECHNICAL FIELD

[0002] The present application relates to the technical field of chemical mechanical polishing, in particular to a metal film thickness online measurement compensation method, a film thickness sensor and equipment. BACKGROUND

[0003] Chemical mechanical polishing (CMP) technology is the preferred planarization process in IC manufacturing process. In chemical mechanical polishing, too much or too little material removal will lead to the degradation of device electrical properties or even failure for the manufacturing process of semiconductor devices. In order to improve the controllability of chemical mechanical polishing process, improve the stability of products, reduce the defect rate of products, and make each wafer achieve uniform production, endpoint detection technology (EPD) of chemical mechanical polishing emerges as the times require.

[0004] In the CMP process, a large amount of heat is generated due to mechanical friction and chemical reaction. On the one hand, this heat is transmitted to the wafer, causing the temperature of the wafer to rise and the electrical conductivity of the metal film to change; on the other hand, the heat is conducted to the eddy current sensor through the polishing disc, causing the working temperature of the eddy current sensor to change. The change of the electrical conductivity of the wafer metal film and the working temperature of the eddy current sensor causes the error of the eddy current sensor measuring the thickness of the wafer metal film, which ultimately affects the detection of the polishing endpoint. SUMMARY

[0005] The embodiments of the present application provide a metal film thickness online measurement compensation method, a film thickness sensor and equipment, which are designed to at least solve one of the technical problems existing in the prior art.

[0006] The first aspect of the embodiments of the present application provides a metal film thickness online measurement compensation method, comprising:

[0007] In the polishing process, the nth output quantity S n of the film thickness sensor measuring the metal film thickness is acquired.

[0008] The sensor temperature t sn at this time and the self-temperature drift function are used to calculate the sensor temperature drift compensation quantity AS sn .

[0009] The wafer temperature t wn at this time, the (n-1)th measured film thickness d n-1 , and the wafer temperature compensation function are used to calculate the wafer temperature drift compensation quantity AS wn .

[0010] calculating the compensated output S' n , S' n = S n - ΔS sn - ΔS wn ;

[0011] obtaining the film thickness d n of the n n th measurement according to the sensor output function and the compensated output S' s .

[0012] In one embodiment, the sensor output function is calibrated by mapping the output of the film thickness sensor and the actual film thickness at normal temperature, and the sensor output function is expressed as d = f1(S), wherein d is the film thickness of the wafer, and S is the output of the film thickness sensor.

[0013] In one embodiment, the self-temperature drift function is calibrated by mapping the output of the film thickness sensor and the temperature at different temperatures, and the self-temperature drift function is expressed as ΔS s = f2(t s ), wherein ΔS s is the sensor temperature drift compensation, and t s is the temperature of the film thickness sensor.

[0014] In one embodiment, the wafer temperature compensation function is calibrated by mapping the output of the film thickness sensor corresponding to different film thicknesses of the wafer at different temperatures, and the wafer temperature compensation function is expressed as ΔS w = f3(t w , d), wherein ΔS w is the wafer temperature drift compensation, t w is the temperature of the wafer, and d is the film thickness of the wafer.

[0015] In one embodiment, the specific calculation process includes:

[0016] ΔS sn = f2(t sn )

[0017] ΔS wn = f3(t wn , d n-1 )

[0018] S' n = S n - ΔS sn - ΔS wn

[0019] d n = f1(S' n )

[0020] wherein f2 is the self temperature drift function, f3 is the wafer temperature compensation function, and f1 is the sensor output function.

[0021] In one embodiment, the output quantity of the film thickness sensor is a resonant frequency.

[0022] A second aspect of the embodiment of the present application provides a film thickness sensor which uses the metal film thickness online measurement compensation method as described above to measure film thickness; the film thickness sensor comprises an eddy current module, a detection circuit and a temperature measurement module.

[0023] A third aspect of the embodiment of the present application provides a chemical mechanical polishing device, comprising:

[0024] A polishing disc for covering a polishing pad for polishing a wafer;

[0025] A carrier head for holding and pressing the wafer against the polishing pad, the carrier head being provided with a temperature detection unit;

[0026] A film thickness sensor as described above for measuring the film thickness of the wafer during polishing;

[0027] A control device for implementing the metal film thickness online measurement compensation method as described above.

[0028] A fourth aspect of the embodiment of the present application provides a control device, comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the metal film thickness online measurement compensation method as described above when executing the computer program.

[0029] A fifth aspect of the embodiment of the present application provides a computer readable storage medium, which stores a computer program, wherein the computer program is executable on a processor to implement the steps of the metal film thickness online measurement compensation method as described above.

[0030] The beneficial effects of the embodiment of the present application include: the influence of temperature change on film thickness measurement can be compensated, and the accuracy and precision of film thickness measurement are significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0031] The advantages of the present application will become more apparent and more readily appreciated when considered in connection with the following detailed description, taken in conjunction with the accompanying drawings, which are merely illustrative and not restrictive, wherein:

[0032] Figure 1 A chemical mechanical polishing device provided by an embodiment of the present application is shown;

[0033] Figure 2A film thickness sensor provided by an embodiment of the present application is shown;

[0034] Figure 3 A relationship curve of film thickness and film thickness sensor output is shown;

[0035] Figure 4 A relationship curve of film thickness sensor output and temperature change is shown;

[0036] Figure 5 A binary change curve of film thickness sensor output, film thickness and temperature is shown;

[0037] Figure 6 A metal film thickness online measurement compensation method provided by an embodiment of the present application is shown;

[0038] Figure 7 A comparison chart of film thickness sensor before and after temperature compensation is shown. DETAILED DESCRIPTION

[0039] The technical solutions of the present application will be described in detail below with reference to specific embodiments and the accompanying drawings. The embodiments described herein are specific specific embodiments of the present application, which are used to illustrate the concept of the present application; these descriptions are all explanatory and exemplary, and should not be understood as limiting the embodiments of the present application and the protection scope of the present application. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. In addition to the embodiments described herein, those skilled in the art can also employ other technical solutions that are obvious based on the content disclosed in the claims and the description of the present application, which include technical solutions that make any obvious replacement and modification to the embodiments described herein. It should be understood that, unless specifically stated, the following description of the specific embodiments of the present application is based on the natural state of the related equipment, devices, components, etc. in the original static state without external control signals and driving forces for the purpose of understanding.

[0040] In addition, it should also be noted that the terms indicating the orientation used in the present application, such as front, back, up, down, left, right, top, bottom, front, back, horizontal, vertical, etc. are only for the purpose of description, to help understand the relative position or direction, and are not intended to limit the orientation of any device or structure.

[0041] In order to illustrate the technical solutions of the present application, the following will be described with reference to the accompanying drawings and in conjunction with the embodiments.

[0042] In this application, the chemical mechanical polishing (CMP) is also called chemical mechanical planarization (CMP), the wafer is also called wafer, silicon wafer, substrate or substrate, etc., which has the same meaning and actual effect.

[0043] As shown in Figure 1 The main components of the chemical mechanical polishing equipment provided by the embodiment of the application include a carrier head 10 for holding and rotating a wafer w, a polishing disc 20 covered with a polishing pad 21, a dresser 30 for dressing the polishing pad 21, and a liquid supply part 40 for supplying polishing liquid.

[0044] In the chemical mechanical polishing process, the carrier head 10 sucks the wafer w by negative pressure, and presses the wafer w with a metal film on the polishing pad 21, and the carrier head 10 rotates and reciprocates along the radial direction of the polishing disc 20 to make the wafer w surface in contact with the polishing pad 21 gradually polished, while the polishing disc 20 rotates, and the liquid supply part 40 sprays the polishing liquid to the surface of the polishing pad 21. Under the chemical action of the polishing liquid, the wafer w is rubbed with the polishing pad 21 by the relative motion of the carrier head 10 and the polishing disc 20 to polish. During polishing, the dresser 30 is used to dress and activate the surface topography of the polishing pad 21. The dresser 30 can remove impurity particles remaining on the surface of the polishing pad 21, such as abrasive particles in the polishing liquid and waste falling from the wafer w surface, etc., and can also flatten the surface deformation of the polishing pad 21 caused by grinding.

[0045] In the chemical mechanical polishing process, the wafer w is pressed on the polishing pad 21 by the carrier head 20, and reciprocates along the radial direction of the polishing disc 10 with the carrier head 20, at the same time, the carrier head 20 rotates synchronously with the polishing disc 10, so that the wafer w surface in contact with the polishing pad 21 is gradually polished.

[0046] As shown in Figure 2 The chemical mechanical polishing equipment further includes a film thickness sensor 50 for measuring the film thickness of the wafer w on line and a control device. The film thickness sensor 50 is installed in the polishing disc 20 and located below the polishing pad 21. The film thickness sensor 50 rotates with the polishing disc 20 to realize the film thickness on-line measurement while polishing. The film thickness sensor 50 is arranged next to the polishing pad 21, and the wafer w is placed on the polishing pad 21, so that the distance between the film thickness sensor 50 and the wafer w is the thickness of the polishing pad 21.

[0047] In the CMP polishing process, the film thickness change of the wafer w and the film thickness value need to be monitored in real time so that the corresponding polishing process is taken to avoid over-polishing or incomplete polishing. The metal film thickness on the wafer w surface is measured on line in the polishing process, so that the removal rate of the metal film is accurately controlled by adjusting the pressure of the carrier head 10 to achieve better global planarization. The film thickness sensor 50 can adopt eddy current detection. The principle of the eddy current detection is that when the film thickness sensor 50 sweeps across the wafer w, the metal film layer on the wafer w surface will induce eddy current to change the magnetic field generated by the film thickness sensor 50, so that when the metal film layer is removed by polishing, the film thickness sensor 50 measures the change of the eddy current to measure the film thickness of the metal film layer.

[0048] Because a large amount of heat is generated in the CMP polishing process, the temperature of the wafer w rises, the working temperature of the film thickness sensor 50 is inconsistent with the calibrated temperature, and temperature drift occurs. Therefore, the output change of the film thickness sensor 50 in the polishing process is composed of three parts: one is the output change caused by the film thickness change of the measured metal film, the change curve is as shown in Figure 3 ; the second is the output change of the film thickness sensor 50 caused by the temperature change, the change curve is as shown in Figure 4 ; and the third is the output change caused by the change of the conductivity of the measured metal film due to the temperature change, the change curve is as shown in Figure 5 . Finally, the output of the film thickness sensor 50 is coupled together by the three parts.

[0049] In order to accurately measure the temperature change in the polishing process, as shown in Figure 1 and Figure 2 , in an embodiment of the present application, a temperature detection unit 11 is arranged on the carrier head 10 to obtain the temperature of the wafer w or the surface temperature of the polishing pad near the wafer w, so that wafer temperature compensation can be achieved. As shown in Figure 2 , the film thickness sensor 50 includes an eddy current module 51, a detection circuit and a temperature measurement module 52. The eddy current module 51 is used to realize metal film thickness detection, and the temperature measurement module 52 is used to detect the temperature change of the film thickness sensor 50 itself to realize self-temperature drift compensation of the film thickness sensor 50.

[0050] Based on the above chemical mechanical polishing equipment and the composition structure of the film thickness sensor 50, as shown in Figure 6 , an embodiment of the present application further provides a metal film thickness on-line measurement compensation method, which comprises the following steps:

[0051] Step S1, in the polishing process, the nth output S n of the film thickness sensor 50 measuring the metal film thickness is obtained. The output of the film thickness sensor 50 is the resonant frequency. The sampling frequency and the output frequency of the film thickness sensor 50 are generally fixed, and the output Sn It is data directly outputted by the film thickness sensor 50 at the nth time, where n is a natural number.

[0052] Step S2: Using the film thickness sensor temperature t sn And its own temperature drift function, calculate the sensor temperature drift compensation ΔS sn The temperature measurement module 52 is used to collect the film thickness sensor temperature t sn The self-temperature drift function is obtained by calibrating the mapping relationship between the output of the film thickness sensor 50 at different temperatures and the temperature. The self-temperature drift function can be expressed as ΔS s =f2(t s ), ΔS s is the sensor temperature drift compensation, t s is the temperature of the film thickness sensor.

[0053] Step S3, using the wafer temperature t wn , the film thickness d measured for the n-1th time n-1 And the wafer temperature compensation function, calculate the wafer temperature drift compensation ΔS wn The temperature detection unit 11 is used to collect the wafer temperature t wn The wafer temperature compensation function is obtained by calibrating the output of the film thickness sensor 50 corresponding to different film thicknesses at different wafer temperatures. The wafer temperature compensation function can be expressed as ΔS w =f3(t w , d), ΔS w is the wafer temperature drift compensation, t w is the wafer temperature, and d is the film thickness of the wafer.

[0054] Step S4, calculate the output after compensation S' n , S′ n =S n -ΔS sn -ΔS wn .

[0055] Step S5: Based on the sensor output function and the compensated output S' n Get the film thickness d measured for the nth time n The sensor output function is obtained by calibrating the mapping relationship between the output of the film thickness sensor at room temperature and the actual film thickness. The sensor output function can be expressed as d=f1(S), where d is the film thickness of the wafer and S is the output of the film thickness sensor.

[0056] It is understandable that the sensor output function f1, the sensor temperature drift function f2 and the wafer temperature compensation function f3 mentioned above can all be represented by a relationship curve, a data calibration table or a fitting function.

[0057] In one embodiment, when executingFigure 6 Before the metal film thickness online measurement compensation method shown, a calibration process is also needed, which specifically includes:

[0058] Calibrate the mapping relationship between the output of the film thickness sensor and the actual film thickness at room temperature to obtain the output function d = f1(S) of the film thickness sensor. For example, at an ambient temperature of 24°C and a fixed lift-off height, place Cu film wafers of different thicknesses on the film thickness sensor 50 to obtain the sensor output function f1(S) at the calibration temperature, as shown in Figure 3 The relationship curve between the film thickness and the output of the sensor output function f1(S) is shown.

[0059] Calibrate the mapping relationship between the output of the film thickness sensor at different temperatures and the temperature to obtain the self-temperature drift function ΔS s = f2(t s ) of the film thickness sensor. Specifically, place the film thickness sensor 50 in a precise temperature control device to calibrate the relationship between the output of the film thickness sensor and the temperature, and then obtain the self-temperature drift function f2(t s ), as shown in Figure 4 The relationship curve between the output of the film thickness sensor and the temperature under no-load condition is shown.

[0060] Calibrate the output of the film thickness sensor corresponding to different film thicknesses of the wafer at different temperatures to obtain the wafer temperature compensation function ΔS w = f3(t w , d). Specifically, place the film thickness sensor 50 and Cu film wafers of different thicknesses in a precise temperature control device, and keep the lift-off height between the film thickness sensor 50 and the Cu film wafer unchanged to obtain the wafer temperature compensation function f3(t w , d) at different film thicknesses and different temperatures. Since the electrical conductivity of the metal changes with temperature, the output of the film thickness sensor also changes with temperature under the same thickness of the metal film, as shown in Figure 5 The binary change curve of the film thickness sensor output and the metal film thickness and temperature is shown.

[0061] In a specific application, when compensating the nth output S n of the film thickness sensor, the film thickness d n-1 measured in the last time, i.e., the (n-1)th time, is needed, and the specific calculation process includes:

[0062] (1) Calculate the self-drift of the film thickness sensor: ΔS sn = f2(t sn );

[0063] (2) Calculate the drift caused by the temperature change of the wafer: ΔS wn = f3(t wn , dn-1

[0064] (3) Eliminate the drift to get the compensated output: S' n = S n - ΔS sn - ΔS wn

[0065] (4) Using the compensated output to calculate the real film thickness: d n = f1(S' n ).

[0066] In the polishing process, the chemical mechanical polishing equipment has not yet occurred a violent chemical reaction, the temperature has not risen, at this time the temperature is consistent with the calibration temperature, the output of the film thickness sensor S1 is correct and does not need temperature compensation, and the film thickness d1 can be directly obtained. Subsequently, due to the chemical reaction in the polishing process, the temperature detection unit 11 is used to obtain the real-time change of the wafer surface temperature, and the temperature change of the film thickness sensor is collected in real time through the temperature measurement module 52, so that the temperature compensation calculation is performed according to the above calculation process.

[0067] In order to facilitate understanding, the following will illustrate the specific execution process:

[0068]

[0069] According to the calculation rule in the above table, the accurate film thickness after each compensation can be obtained.

[0070] As shown in Figure 7 , the applicant verifies the technical effect of the metal film thickness online measurement compensation method provided by the embodiment of the application through experiments. The cu film thickness of the sample piece is measured by using a four-probe instrument As shown in Figure 7 , in the range of temperature change from 15 to 35℃, if there is no temperature compensation, the measurement accuracy of the film thickness sensor is After increasing the temperature compensation, the measurement accuracy of the film thickness sensor is The measurement accuracy is improved by 10 times. In addition, the above metal film thickness online measurement compensation method is also applicable to the CMP wafer surface planarization and end point stopping of W and AL processes.

[0071] The above, the metal film thickness online measurement compensation method provided by the embodiment of the application can compensate the influence of temperature change on film thickness measurement, and significantly improve the accuracy and precision of film thickness measurement.

[0072] The embodiment of the application also provides a control device, which comprises a processor, a memory and a computer program stored in the memory and executable on the processor. The processor implements the method as Figure 6 ​​The method steps are shown. The control device refers to a terminal with data processing capability, including but not limited to a computer, a workstation, a server, and even some high-performance smart phones, palm computers, tablet computers, personal digital assistants (PDAs), smart TVs (Smart TVs), etc. The operating system is generally installed on the control device, including but not limited to: Windows operating system, LINUX operating system, Android operating system, Symbian operating system, Windows mobile operating system, and iOS operating system, etc. The above lists specific examples of control devices. Those skilled in the art can realize that the control device is not limited to the above listed examples.

[0073] The embodiment of the present application also provides a computer readable storage medium, which stores a computer program. The computer program is executed by a processor to realize the method as Figure 6 The computer program can be stored in a computer readable storage medium. The computer program is executed by a processor to realize the steps of the above method embodiments. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or some intermediate forms, etc. The computer readable medium can include any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc.

[0074] Those skilled in the art can realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be realized by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are realized 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 the present application.

[0075] The above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A chemical mechanical polishing apparatus characterized by comprising: The application relates to a polishing device for polishing a wafer, comprising: a polishing disc for covering a polishing pad for polishing the wafer; a carrier head for holding the wafer and pressing the wafer on the polishing pad, wherein a temperature detecting unit is arranged on the carrier head for detecting the wafer surface temperature; a film thickness sensor installed in the polishing disc for measuring the wafer film thickness during polishing, wherein the film thickness sensor comprises an eddy current module, a detecting circuit and a temperature detecting module for detecting the film thickness sensor temperature; a control device for The wafer temperature compensation amount ΔS is calculated from a wafer temperature compensation function obtained by calibrating the output of the film thickness sensor corresponding to different film thicknesses of the wafer at different temperatures, the wafer surface temperature, and the film thickness measured n-1 times wn ; According to the self temperature drift function of the film thickness sensor obtained through the mapping relationship between the output of the film thickness sensor at different temperatures and the temperature and the film thickness sensor temperature, a sensor temperature drift compensation quantity ΔS is calculated sn ; According to the nth output S of the film thickness sensor n , the wafer temperature compensation amount ΔS wn and the sensor temperature drift compensation ΔS sn , determine the output S′ after compensation n , S′ n =S n -ΔS sn -ΔS wn ; According to the compensated output quantity S' n The film thickness of the wafer of the n-th measurement is determined.

2. The chemical mechanical polishing apparatus of claim 1, wherein the film thickness sensor is located below and close to the polishing pad.

3. The chemical mechanical polishing apparatus of claim 1, wherein The wafer temperature compensation function is expressed as ΔS w = f3(t w , d), where t w is wafer temperature and d is film thickness of the wafer.

4. The chemical mechanical polishing apparatus of claim 1, wherein The self temperature drift function is expressed as ΔS s = f2(t s ), where t s is the temperature of the film thickness sensor.

5. The chemical mechanical polishing apparatus according to any one of claims 1 to 4, wherein the film thickness of the wafer is determined according to the compensated output quantity, comprising: calibrating the mapping relationship between the film thickness sensor output and the actual film thickness at normal temperature to obtain an output function d=f1(S) of the film thickness sensor; The compensated output quantity S' is used to calculate the film thickness d n and the output function of the sensor to calculate the film thickness d n .

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