CN102445144A - Calibrating method and device for online membrane thickness measuring system - Google Patents

Abstract

The invention discloses a calibration method for an online film thickness measurement system, comprising the following steps: detecting the polishing pressure on multiple wafers, and when the polishing pressure reaches a preset pressure value, respectively The circle is polished to a preset degree; after polishing, the on-chip voltage and the off-chip voltage of each wafer are respectively collected and the difference between the on-chip voltage and the off-chip voltage is calculated; each wafer after polishing is measured The coating thickness value of each wafer; the difference between the on-chip voltage and the off-chip voltage of each wafer is associated with the corresponding coating thickness value of each wafer after polishing to generate a voltage difference Value-film thickness calibration table; perform coating thickness calibration on the online film thickness measurement system according to the voltage difference-film thickness calibration table. The invention also discloses a calibration device for an online film thickness measurement system. The invention can realize rapid and accurate calibration of coating film thickness under different polishing processes.

Description

Calibration method and calibration device for online film thickness measurement system

technical field

The invention relates to the technical field of chemical mechanical polishing of integrated circuits, in particular to a calibration method and a calibration device for an online film thickness measurement system.

Background technique

In IC (Integrated Circuit, integrated circuit) manufacturing technology, with the continuous improvement of product performance, the requirements for surface quality are getting higher and higher. As the basic material of integrated circuit chips, silicon wafers have surface roughness and surface flatness as one of the important factors affecting the etching line width of integrated circuits. Polishing is an important means of surface planarization. The CMP (Chemical Mechanical Polishing) process is the most widely used global planarization technology and occupies an important position in IC manufacturing technology. CMP is a combined technology of mechanical grinding and chemical etching. The process is to rotate the workpiece to be polished relative to the polishing pad under a certain downforce and the presence of polishing fluid. The corrosive action of the oxidizing agent is used to complete the material removal on the surface of the workpiece and obtain a smooth surface.

With the development of integrated circuit manufacturing technology, new semiconductors, conductors and dielectric materials are widely used to overcome the problems of power consumption and signal delay caused by high integration. At present, the wafer size has reached a diameter of more than 300mm, and the characteristic line width has reached below 45nm. The delay of copper interconnection limits the development of IC to a higher speed. An effective way to improve low-k dielectric, small line width and multi-layer count. During the CMP polishing process, it is necessary to monitor the film thickness change and film thickness value of the wafer in real time, so as to adopt the corresponding polishing process to avoid over-polishing or incomplete polishing. As a non-contact measurement method, the eddy current method can measure the copper film thickness value during the polishing process without destroying the copper film. In the actual application process, it is necessary to convert the voltage value measured by the eddy current film thickness measurement system into a copper film thickness value, that is, the calibration of the thickness value is the key to whether the online film thickness measurement system can accurately provide the film thickness value. Therefore, how to realize the rapid and accurate calibration of the online film thickness measurement system is an important problem to be solved at present.

Contents of the invention

The purpose of the present invention is to solve at least one of the above-mentioned technical drawbacks.

Therefore, the first object of the present invention is to provide a calibration method for an online film thickness measurement system that uses fewer wafers to calibrate the coating thickness. The second object of the present invention is to provide a calibration device for an online film thickness measurement system.

In order to achieve the above purpose, the embodiment of the first aspect of the present invention proposes a calibration method for an online film thickness measurement system, including the following steps:

Detecting the polishing pressure on the plurality of wafers, and when the polishing pressure reaches a preset pressure value, respectively performing a preset degree of polishing on the plurality of wafers, wherein the coating thicknesses of the plurality of wafers are equal;

After polishing, the on-chip voltage and off-chip voltage of each wafer are respectively collected and the difference between the on-chip voltage and the off-chip voltage is calculated, wherein the on-chip voltage is the online film thickness measurement system The voltage signal output when the eddy current sensor of the eddy current sensor runs to the wafer, the off-chip voltage is the voltage signal output by the eddy current sensor of the online film thickness measurement system when it is no-load;

Measure the coating thickness value of each wafer after polishing;

Correlating the difference between the on-chip voltage and the off-chip voltage of each wafer with the corresponding coating thickness value of each wafer after polishing, to generate a voltage difference-film thickness calibration table; and

Perform coating thickness calibration on the online film thickness measurement system according to the voltage difference-film thickness calibration table.

According to the calibration method for the online film thickness measurement system provided by the embodiment of the present invention, multiple wafers are polished according to a preset degree, and the difference between the on-chip voltage and the off-chip voltage of each polished wafer Correlate with the thickness of each wafer after polishing to obtain the voltage difference-film thickness calibration table, through which the accurate calibration of the coating thickness of the online film thickness measurement system can be realized, so as to achieve different polishing processes. , Fast and accurate calibration of coating thickness.

In one embodiment of the present invention, when it is detected that the polishing pressure of the current wafer does not reach the preset pressure value, the polishing pressure applied by the polishing head of the online film thickness measurement system to the current wafer is adjusted. pressure until the polishing pressure of the current wafer reaches the preset pressure value.

In one embodiment of the present invention, the plurality of wafers are polished to a preset degree by controlling the polishing time of each wafer by the polishing head of the online film thickness measurement system.

As a result, multiple wafers are polished to different degrees, so that the thickness of the coating film after polishing is also different.

In one embodiment of the present invention, the coating film of one wafer in the plurality of wafers is completely polished, wherein the polishing time is the first duration; the remaining wafers are (i-1)T according to the polishing time /n to perform the preset degree of polishing, where i is the number of the wafer, 2≤i≤n, and T is the first duration.

In one embodiment of the present invention, the on-chip voltage and off-chip voltage of each wafer are collected, and the collected on-chip voltage and off-chip voltage of each wafer are converted into digital signals to obtain The difference between the on-chip voltage and the off-chip voltage.

In one embodiment of the present invention, a four-probe probe is used to measure the coating thickness of each wafer after polishing.

In one embodiment of the present invention, the following step is further included: displaying the coating thickness value in the voltage difference-film thickness calibration table.

Thus, the operator can conveniently and timely obtain the coating thickness value of the wafer.

The embodiment of the second aspect of the present invention provides a calibration device for an online film thickness measurement system, including: a pressure detection module, the pressure detection module is respectively connected to multiple wafers, and is used to detect the multiple wafers The polishing pressure on the circle, when the polishing pressure reaches the preset pressure value, the polishing head of the online film thickness measurement system will respectively perform a preset degree of polishing on the multiple wafers, wherein the multiple wafers The coating thickness of the circle is equal; the data acquisition module is connected with the eddy current sensor of the online film thickness measurement system, and is used to polish the multiple wafers at the polishing head of the online film thickness measurement system After the end, collect the on-chip voltage and off-chip voltage of each wafer respectively and calculate the difference between the on-chip voltage and the off-chip voltage, wherein the on-chip voltage is the voltage of the online film thickness measurement system The voltage signal output when the eddy current sensor runs on the wafer, the off-chip voltage is the voltage signal output by the eddy current sensor of the online film thickness measurement system when it is no-load; the film thickness measurement module is used for After the polishing head of the online film thickness measurement system finishes polishing the multiple wafers, measure the coating thickness value of each wafer after polishing; a calibration module, the calibration module is respectively connected with the data acquisition module and the The film thickness measurement module is connected to correlate the difference between the on-chip voltage and the off-chip voltage of each wafer with the corresponding coating thickness value of each wafer after polishing to generate a voltage difference Value-film thickness calibration table to calibrate the coating thickness of the online film thickness measurement system.

According to the calibration device for the online film thickness measurement system provided by the embodiment of the present invention, multiple wafers are polished according to a preset degree, and the difference between the on-chip voltage and the off-chip voltage of each polished wafer Correlate with the thickness of each wafer after polishing to obtain the voltage difference-film thickness calibration table, through which the accurate calibration of the coating thickness of the online film thickness measurement system can be realized, so as to achieve different polishing processes. , Fast and accurate calibration of coating thickness.

In one embodiment of the present invention, when the pressure detection module detects that the current polishing pressure of the wafer has not reached the preset pressure value, it adjusts the polishing head of the online film thickness measurement system to apply the current The polishing pressure on the wafer until the polishing pressure of the current wafer reaches the preset pressure value.

In one embodiment of the present invention, the data acquisition card is an analog/digital acquisition card; the film thickness measurement module is a four-probe probe; the display module is connected to the calibration module for displaying the voltage Difference - coating thickness value from the film thickness calibration table.

Thus, the operator can conveniently and timely obtain the coating thickness value of the wafer.

Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and easy to understand from the following description of the embodiments in conjunction with the accompanying drawings, wherein:

1 is a schematic diagram of a calibration method for an online film thickness measurement system according to an embodiment of the present invention;

Fig. 2 is a flow chart of the calibration method for the online film thickness measurement system in Fig. 1;

Fig. 3 is voltage-time curve;

Figure 4 is the voltage difference-film thickness curve;

Fig. 5 is the schematic diagram that obtains coating thickness value according to voltage difference-film thickness calibration table; With

Fig. 6 is a schematic diagram of a calibration device for an online film thickness measurement system according to an embodiment of the present invention.

Detailed ways

Embodiments of the present invention are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals designate the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

In describing the present invention, it should be understood that the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", The orientation or positional relationship indicated by "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than Nothing indicating or implying that a referenced device or element must have a particular orientation, be constructed, and operate in a particular orientation should therefore not be construed as limiting the invention.

In the description of the present invention, it should be noted that unless otherwise specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a mechanical connection or an electrical connection, or it can be two The internal communication of each element may be directly connected or indirectly connected through an intermediary. Those skilled in the art can understand the specific meanings of the above terms according to specific situations.

The following describes a calibration method for an online film thickness measurement system according to an embodiment of the present invention with reference to FIG. 1 .

As shown in Figure 1, the calibration method for the online film thickness measurement system provided by the embodiment of the present invention includes the following steps:

S101: Detect the polishing pressure on multiple wafers, and when the polishing pressure reaches the preset pressure value, perform the preset degree of polishing on the multiple wafers, wherein the number of multiple wafers is greater than or equal to three, and each wafer Wafers are coated with equal thickness.

S102: After the polishing is finished, respectively collect the on-chip voltage and the off-chip voltage of each wafer and calculate the difference between the on-chip voltage and the off-chip voltage.

Among them, the on-chip voltage is the voltage signal output when the eddy current sensor of the online film thickness measurement system runs on the wafer, and the off-chip voltage is the voltage signal output by the eddy current sensor of the online film thickness measurement system when it is no-load.

S103: Measuring the coating thickness of each wafer after polishing.

S104: Generate a voltage difference-film thickness calibration table.

The difference between the on-chip voltage and the off-chip voltage of each wafer is correlated with the corresponding coating thickness value of each wafer after polishing, so as to generate a voltage difference-film thickness calibration table.

S105: Perform coating thickness calibration on the online film thickness measurement system according to the voltage difference-film thickness calibration table.

According to the calibration method for the online film thickness measurement system provided by the embodiment of the present invention, multiple wafers are polished according to a preset degree, and the difference between the on-chip voltage and the off-chip voltage of each polished wafer Correlate with the thickness of each wafer after polishing to obtain the voltage difference-film thickness calibration table, through which the accurate calibration of the coating thickness of the online film thickness measurement system can be realized, so as to achieve different polishing processes. , Fast and accurate calibration of coating thickness.

The calibration method for the online film thickness measurement system provided by the embodiment of the present invention will be described in detail below with reference to FIG. 2 and FIG. 3 . Wherein, the wafer may be a copper-plated silicon wafer, and the thickness of the coating film is the thickness of the copper film. It can be understood that the above-mentioned copper film is only for the purpose of illustration, rather than limiting the scope of the present invention. Silicon wafers can be plated with other materials such as silicon dioxide. The steps of implementing the calibration method for the online film thickness measurement system according to the embodiment of the present invention by using the above-mentioned wafer are the same.

S201: Calibration starts;

S202: Apply polishing pressure to multiple wafers by the polishing head of the online film thickness measurement system. Wherein, the number of multiple wafers is n, and n=1, 2, 3...n. The coating thickness of each wafer is equal.

S203: Detect the polishing pressure on the multiple wafers.

Detect the polishing pressure exerted by the polishing head of the online film thickness measurement system on n wafers, and compare the current polishing pressure of each wafer with the preset pressure value. In one embodiment of the present invention, a pressure sensor is used to detect the polishing pressure on multiple wafers.

If the current polishing pressure of the wafer does not reach the preset pressure value, continue to adjust the polishing pressure exerted on the current wafer by the polishing head of the online film thickness measurement system until the above preset pressure value is reached; if the current polishing pressure of the wafer does not When the preset pressure value is reached, the process proceeds to subsequent corresponding steps to perform a preset degree of polishing on multiple wafers.

In one embodiment of the present invention, multiple wafers are polished to a predetermined degree, including performing complete polishing and incomplete polishing on multiple wafers, and different degrees of polishing of multiple wafers are achieved by controlling the polishing time. polishing. As a result, multiple wafers are polished to different degrees, so that the thickness of the coating film after polishing is also different.

S2041: Completely polish the coating film of one of the n wafers. Taking the first wafer among the n wafers as an example, the wafer is completely polished to completely remove the copper film on the silicon wafer, and the polishing time is the first duration, denoted as T. After the wafer is completely polished, go to step S205.

Steps S2042 to S204n respectively perform a preset level of polishing on the remaining wafers according to a polishing time of (i-1)T/n, where i is the serial number of each wafer, and 2≤i≤n.

S2042: Perform incomplete polishing on the coating film of the second wafer (i=2) among the n wafers, and the polishing time is T/n. After the above polishing time is reached, go to step S205.

S2043: Perform incomplete polishing on the coating film of the third wafer (i=3) among the n wafers, and the polishing time is 2T/n. After the above polishing time is reached, go to step S205.

By analogy, incomplete polishing is performed on other wafers until the nth wafer.

S204n: Perform incomplete polishing on the coating film of the nth wafer (i=n) among the n wafers, and the polishing time is (n−1)T/n. After the above polishing time is reached, go to step S205.

S205: Use the data acquisition card to collect the relationship between the on-chip and off-chip voltage values of each wafer as a function of time.

The on-chip voltage is the voltage signal output when the eddy current sensor of the online film thickness measurement system runs on the wafer, and the off-chip voltage is the output voltage signal when the eddy current sensor of the online film thickness measurement system leaves the wafer, that is, no-load. The on-chip voltage and off-chip voltage output by the online film thickness measurement system are collected by the data acquisition card and the corresponding relationship with time. In this way, n curves corresponding to the on-chip voltage and off-chip voltage and time can be obtained, corresponding to n wafers respectively.

Fig. 3 shows the relationship curves of on-chip voltage and off-chip voltage versus time. The abscissa is time in seconds, and the ordinate is voltage in millivolts. When the probe runs to the measurement position, that is, on-chip, the voltage signal has a peak value, and the voltage signal at this time is the on-chip voltage signal. When the probe leaves the measuring position, that is, when the chip is off, the voltage signal has a valley value, and the voltage signal at this time is the off-chip voltage signal.

S206: Using the signal processing module of the online film thickness measurement system to process the above-mentioned on-chip voltage signal and off-chip voltage signal to obtain a corresponding relationship between the difference between the on-chip voltage and the off-chip voltage and time.

The signal processing module of the online film thickness measurement system converts the collected on-chip voltage and off-chip voltage of the wafer into digital signals to obtain the difference between the on-chip voltage and the off-chip voltage, and then obtain the difference between the on-chip voltage and the off-chip voltage Correspondence between value and time.

S207: Generate and save n curves corresponding to the difference between the on-chip voltage and the off-chip voltage and time.

Using the difference between the on-chip voltage and the off-chip voltage in the calibration curve can avoid the drift of the zero point of the signal.

S208: Using a four-probe method to determine the thickness of the copper film after polishing.

A four-probe probe was used to measure the thickness of the remaining copper film on each wafer after polishing. Since the first wafer has been fully polished, the remaining copper film thickness is zero. The remaining wafers are numbered, and the polishing time increases, and the thickness of the remaining copper film decreases.

S209: Generate a curve corresponding to the difference between the on-chip voltage and the off-chip voltage and the thickness of the copper film.

The remaining copper film thickness of each wafer measured in step S208 is associated with the difference between the on-chip voltage and the off-chip voltage at the end of the polishing process of each piece recorded in step S207, and the on-chip voltage and the off-chip voltage are generated. The corresponding curve of the difference and the thickness of the copper film.

FIG. 4 shows the corresponding curves of the difference between the on-chip voltage and the off-chip voltage and the thickness of the copper film. The abscissa is the thickness of the copper film in nanometers, and the ordinate is the difference between the on-chip voltage and the off-chip voltage in millivolts. It can be seen from Figure 4 that as the difference between the on-chip voltage and the off-chip voltage decreases, the degree of polishing increases and the thickness of the copper film decreases.

S210: Calibrate the online film thickness measurement system.

Generate a voltage difference-film thickness calibration table according to the difference between the on-chip voltage and off-chip voltage and the corresponding curve of the copper film thickness, and input it into the online film thickness measurement system to complete the online film thickness measurement system for the calibration of the coating thickness.

S211: Calibration is completed.

The process of obtaining the copper film thickness value according to the voltage difference-film thickness calibration table is described below in conjunction with FIG. 5 .

When the chemical mechanical polishing machine is working, the probe and front-end circuit of the online film thickness measurement system input the on-chip voltage signal and the off-chip voltage signal of the current wafer to the signal processing unit of the online film thickness measurement system in real time, and the signal processing unit converts the above The voltage signal is converted into the difference between the on-chip voltage and the off-chip voltage, and is input into the voltage difference-film thickness calibration table. By looking up the table, the copper film thickness value of the wafer is obtained.

In one embodiment of the present invention, the voltage difference and coating thickness in the voltage difference-film thickness calibration table and the found copper film thickness value of the current wafer can be displayed through the display screen. Thus, the operator can conveniently and timely obtain the coating thickness value of the wafer.

According to the calibration method for the online film thickness measurement system provided by the embodiment of the present invention, multiple wafers are polished according to a preset degree, and the difference between the on-chip voltage and the off-chip voltage of each polished wafer Correlating with the thickness of each corresponding wafer after polishing, a voltage difference-film thickness calibration table is obtained, through which accurate calibration of the coating thickness of the online film thickness measurement system can be realized. Using the difference between the on-chip voltage and the off-chip voltage in the calibration curve can avoid the drift of the signal zero point and improve the calibration accuracy of the coating thickness. The present invention can realize accurate calibration of coating film thickness under different polishing processes, such as chemical mechanical polishing processes.

A calibration device 600 for an online film thickness measurement system according to an embodiment of the present invention will be described below with reference to FIG. 6 .

As shown in FIG. 6 , a calibration device 600 for an online film thickness measurement system according to an embodiment of the present invention includes a pressure detection module 610 , a data collection module 620 , a film thickness measurement module 630 and a calibration module 640 .

The pressure detection module 610 is connected to multiple wafers respectively, and is used to detect the polishing pressure on the multiple wafers. When the polishing pressure reaches the preset pressure value, the polishing head of the online film thickness measurement system will perform the polishing on the multiple wafers respectively. Preset level of polish. The number of multiple wafers is greater than or equal to three, and the coating thickness of each wafer is equal. The data acquisition module 620 is connected with the eddy current sensor of the online film thickness measurement system, and is used for the polishing head of the online film thickness measurement system to collect the on-chip voltage and the off-chip voltage of each wafer after polishing the multiple wafers and calculate The difference between the on-chip voltage and the off-chip voltage. Among them, the on-chip voltage is the voltage signal output when the eddy current sensor of the online film thickness measurement system runs on the wafer, and the off-chip voltage is the voltage signal output by the eddy current sensor of the online film thickness measurement system when it is no-load.

The film thickness measurement module 630 is used for measuring the coating thickness value of each wafer after polishing by the polishing head of the online film thickness measurement system after polishing multiple wafers. The calibration module 640 is connected to the data acquisition module 620 and the film thickness measurement module 630 respectively, and is used to compare the difference between the on-chip voltage and the off-chip voltage of each wafer with the corresponding coating thickness value of each wafer after polishing. Associated to generate a voltage difference-film thickness calibration table to calibrate the coating thickness of the online film thickness measurement system.

According to the calibration device for the online film thickness measurement system provided by the embodiment of the present invention, multiple wafers are polished according to a preset degree, and the difference between the on-chip voltage and the off-chip voltage of each polished wafer Correlate with the thickness of each wafer after polishing to obtain the voltage difference-film thickness calibration table, through which the accurate calibration of the coating thickness of the online film thickness measurement system can be realized, so as to achieve different polishing processes. , accurate calibration of coating thickness.

The calibration process of the calibration device 600 for the online film thickness measurement system according to the embodiment of the present invention will be described below. Wherein, the wafer may be a copper-plated silicon wafer, and the thickness of the coating film is the thickness of the copper film. It can be understood that the above-mentioned copper film is only for the purpose of illustration, rather than limiting the scope of the present invention. Silicon wafers can be plated with other materials such as silicon dioxide. The structure and calibration process of the calibration device for the online film thickness measurement system of the embodiment of the present invention realized by using the above-mentioned wafer are the same.

First, the polishing head of the online film thickness measurement system applies polishing pressure to multiple wafers. Wherein, the number of multiple wafers is n, and n=1, 2, 3...n. Each wafer is coated with the same thickness. The pressure detection module 610 detects the polishing pressure exerted by the polishing head of the online film thickness measurement system on n wafers, and compares the current polishing pressure of each wafer with a preset pressure value. If the current polishing pressure of the wafer does not reach the preset pressure value, continue to adjust the polishing pressure applied on the current wafer by the polishing head of the online film thickness measurement system until the above preset pressure value is reached. If the pressure detection module 610 detects that the current polishing pressure of the wafer does not reach the preset pressure value, the polishing head of the online film thickness measurement system will perform a preset degree of polishing on multiple wafers.

In one embodiment of the present invention, multiple wafers are polished to a predetermined degree, including performing complete polishing and incomplete polishing on multiple wafers, and different degrees of polishing of multiple wafers are achieved by controlling the polishing time. polishing. As a result, multiple wafers are polished to different degrees, so that the thickness of the coating film after polishing is also different.

Specifically, the coating film of one of the n wafers is completely polished. Taking the first wafer among the n wafers as an example, the wafer is completely polished to completely remove the copper film on the silicon wafer, and the polishing time is the first duration, denoted as T. The remaining wafers are respectively polished to a preset degree according to a polishing time of (i-1)T/n, wherein, i is the serial number of each wafer, and 2≤i≤n.

Whenever a wafer is polished to a preset degree, the data collection module 620 is used to collect the relationship between the on-chip and off-chip voltage values of each wafer as a function of time. Among them, the on-chip voltage is the voltage signal output when the eddy current sensor of the online film thickness measurement system runs on the wafer, and the off-chip voltage is the output voltage signal when the eddy current sensor of the online film thickness measurement system leaves the wafer, that is, no-load . The on-chip voltage and off-chip voltage output by the online film thickness measurement system are collected by the data acquisition card and the corresponding relationship with time. Thus, the data acquisition module 620 can obtain n curves of on-chip voltage and off-chip voltage versus time, corresponding to n wafers respectively. The data acquisition module 620 converts the collected on-chip voltage and off-chip voltage of the wafer into digital signals to obtain the difference between the on-chip voltage and the off-chip voltage, and then obtain the correspondence between the difference between the on-chip voltage and the off-chip voltage and time relationship, thereby generating and saving n curves corresponding to the difference between the on-chip voltage and the off-chip voltage and time. Using the difference between the on-chip voltage and the off-chip voltage in the calibration curve can avoid the drift of the zero point of the signal.

In one embodiment of the present invention, the data acquisition module 620 is an analog-digital acquisition card. It can be understood that the data acquisition module 620 can also be a signal processing module of the online film thickness measurement system.

The film thickness measurement module 630 measures the thickness of the remaining copper film on each wafer after polishing. Since the first wafer has been fully polished, the remaining copper film thickness is zero. The remaining wafers are numbered, and the polishing time increases, and the thickness of the remaining copper film decreases.

In one embodiment of the present invention, the film thickness measurement module 630 may be a four-probe probe.

The calibration module 640 correlates the remaining copper film thickness of each wafer obtained in the film thickness measurement module 630 with the difference between the on-chip voltage and the off-chip voltage recorded in the data acquisition module 620 at the end of the polishing process, Generate a plot of the difference between on-chip and off-chip voltages versus copper film thickness. Generate a voltage difference-film thickness calibration table according to the difference between the on-chip voltage and off-chip voltage and the corresponding curve of the copper film thickness, and input it into the online film thickness measurement system to complete the online film thickness measurement system for the calibration of the coating thickness.

When the chemical mechanical polishing machine is working, the probe and front-end circuit of the online film thickness measurement system input the on-chip voltage signal and the off-chip voltage signal of the current wafer to the signal processing unit of the online film thickness measurement system in real time, and the signal processing unit converts the above The voltage signal is converted into the difference between the on-chip voltage and the off-chip voltage, and is input into the voltage difference-film thickness calibration table. By looking up the table, the copper film thickness value of the wafer is obtained.

In an embodiment of the present invention, the calibration device 600 for the online film thickness measurement system of the embodiment of the present invention further includes a display module. The display module is connected with the calibration module 640, and is used for displaying the voltage difference and the coating thickness in the voltage difference-film thickness calibration table and the found copper film thickness value of the current wafer. Thus, the operator can conveniently and timely obtain the coating thickness value of the wafer.

According to the calibration device for the online film thickness measurement system provided by the embodiment of the present invention, multiple wafers are polished according to a preset degree, and the difference between the on-chip voltage and the off-chip voltage of each polished wafer Correlating with the thickness of each corresponding wafer after polishing, a voltage difference-film thickness calibration table is obtained, through which accurate calibration of the coating thickness of the online film thickness measurement system can be realized. Using the difference between the on-chip voltage and the off-chip voltage in the calibration curve can avoid the drift of the signal zero point and improve the calibration accuracy of the coating thickness. The present invention can realize accurate calibration of coating film thickness under different polishing processes, such as chemical mechanical polishing processes.

In the description of this specification, descriptions referring to the terms "one embodiment", "some embodiments", "example", "specific examples", or "some examples" mean that specific features described in connection with the embodiment or example , structure, material or characteristic is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although the embodiments of the present invention have been shown and described, those skilled in the art can understand that various changes, modifications and substitutions can be made to these embodiments without departing from the principle and spirit of the present invention. and modifications, the scope of the invention is defined by the appended claims and their equivalents.

Claims (10)

1. A calibration method for on-line film thickness measurement system, is characterized in that, comprises the steps: Detecting the polishing pressure on the plurality of wafers, and when the polishing pressure reaches a preset pressure value, respectively performing a preset degree of polishing on the plurality of wafers, wherein the coating thicknesses of the plurality of wafers are equal; After polishing, the on-chip voltage and off-chip voltage of each wafer are respectively collected and the difference between the on-chip voltage and the off-chip voltage is calculated, wherein the on-chip voltage is the online film thickness measurement system The voltage signal output when the eddy current sensor of the eddy current sensor runs to the wafer, the off-chip voltage is the voltage signal output by the eddy current sensor of the online film thickness measurement system when it is no-load; Measure the coating thickness value of each wafer after polishing; Correlating the difference between the on-chip voltage and the off-chip voltage of each wafer with the corresponding coating thickness value of each wafer after polishing, to generate a voltage difference-film thickness calibration table; and Perform coating thickness calibration on the online film thickness measurement system according to the voltage difference-film thickness calibration table. 2. The calibration method for an online film thickness measurement system according to claim 1, wherein when it is detected that the polishing pressure of the current wafer does not reach the preset pressure value, the online film thickness is adjusted measuring the polishing pressure applied by the polishing head of the system on the current wafer until the polishing pressure of the current wafer reaches the preset pressure value. 3. the calibration method for on-line film thickness measurement system as claimed in claim 1, is characterized in that, by controlling the polishing head of described on-line film thickness measurement system to the polishing time of described each wafer to the described Multiple wafers are polished to a preset level. 4. The calibration method for an online film thickness measurement system according to claim 3, wherein the coating of a wafer in the plurality of wafers is completely polished, wherein the polishing time is the first duration ; The remaining wafers are polished to a preset degree according to a polishing time of (i-1)T/n, wherein i is the number of the wafer, 2≤i≤n, and T is the first duration. 5. the calibration method that is used for online film thickness measurement system as claimed in claim 1, is characterized in that, collects the on-chip voltage and off-chip voltage of described each wafer, and the described each wafer of described collection The on-chip voltage and the off-chip voltage of the wafer are converted into digital signals to obtain the difference between the on-chip voltage and the off-chip voltage. 6. The calibration method for an online film thickness measurement system according to claim 1, wherein a four-probe probe is used to measure the coating thickness value of each wafer after polishing. 7. The calibration method for an online film thickness measurement system according to claim 1, further comprising the step of: displaying the coating thickness value in the voltage difference-film thickness calibration table. 8. A calibration device for an online film thickness measurement system, characterized in that it comprises: A pressure detection module, the pressure detection module is connected to multiple wafers respectively, and is used to detect the polishing pressure on the multiple wafers. When the polishing pressure reaches a preset pressure value, the online film thickness measurement The polishing head of the system respectively performs a predetermined degree of polishing on the multiple wafers, wherein the coating thicknesses of the multiple wafers are equal; A data acquisition module, the data acquisition module is connected to the eddy current sensor of the online film thickness measurement system, and is used to respectively collect the Describe the on-chip voltage and off-chip voltage of each wafer and calculate the difference between the on-chip voltage and the off-chip voltage, wherein the on-chip voltage is the operation of the eddy current sensor of the online film thickness measurement system to the The voltage signal output when on the wafer, the off-chip voltage is the voltage signal output when the eddy current sensor of the online film thickness measurement system is no-load; The film thickness measurement module is used to measure the coating thickness value of each wafer after polishing after the polishing head of the online film thickness measurement system finishes polishing the multiple wafers; and A calibration module, the calibration module is respectively connected with the data acquisition module and the film thickness measurement module, and is used to compare the difference between the on-chip voltage and the off-chip voltage of each wafer with the corresponding post-polishing The coating thickness value of each wafer is correlated, and a voltage difference-film thickness calibration table is generated to calibrate the coating thickness of the online film thickness measurement system. 9. The calibration device for an online film thickness measurement system according to claim 8, wherein when the pressure detection module detects that the polishing pressure of the current wafer does not reach the preset pressure value, adjust The polishing head of the online film thickness measurement system applies a polishing pressure on the current wafer until the polishing pressure of the current wafer reaches the preset pressure value. 10. The calibration device for online film thickness measurement system as claimed in claim 8, wherein the data acquisition card is an analog/digital acquisition card; the film thickness measurement module is a four-probe probe; The display module is connected with the calibration module, and is used for displaying the coating thickness value in the voltage difference-film thickness calibration table.

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