Grinding device

Abstract

To provide a polishing apparatus that can efficiently monitor film thickness for various types of workpieces. [Solution] The polishing apparatus comprises a polishing head, a polishing table, and a film thickness measuring system, wherein the film thickness measuring system comprises a plurality of sensor heads arranged on the polishing table, each sensor head consisting of an eddy current sensor, and a control unit, wherein the control unit comprises an oscillator that generates a common clock signal for driving the eddy current sensors, and a plurality of control circuits provided corresponding to each of the plurality of sensor heads, each control circuit configured to generate a drive signal to the eddy current sensor of the sensor head based on the clock signal from the oscillator, and to process the measurement signal received from the eddy current sensor of the sensor head.

Description

Technical Field

[0006] , ,

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[0001] The present invention relates to a polishing apparatus.

Background Art

[0002] Conventionally, for example, a polishing apparatus has been used to polish an object to be polished such as a semiconductor substrate. The polishing apparatus includes a polishing table to which a polishing pad is attached and a polishing head to which a substrate to be polished is attached. In the polishing apparatus, a polishing liquid is supplied to the polishing pad, and at least one of the polishing table and the polishing head is rotated while the polishing pad and the substrate are in contact with each other, whereby the substrate is polished.

[0003] A film thickness sensor for monitoring the polishing amount of the substrate or the film on the substrate is provided on the polishing table. As the film thickness sensor, an eddy current sensor capable of measuring the thickness of the conductive film on the substrate can be used (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0007] According to one embodiment, a polishing apparatus for polishing an object to be polished is provided, comprising: a polishing head configured to be able to attach the object to be polished; a polishing table arranged to face the object to be polished attached to the polishing head and configured to be rotatable; and a film thickness measuring system for measuring the film thickness of a conductive film on the object to be polished by the polishing apparatus, wherein the film thickness measuring system comprises a plurality of sensor heads arranged on the polishing table, each sensor head comprising an eddy current sensor; and a control unit, wherein the control unit comprises an oscillator that generates a common clock signal for driving the eddy current sensors; and a plurality of control circuits provided corresponding to each of the plurality of sensor heads, each control circuit configured to generate a drive signal to the eddy current sensor of the sensor head based on the clock signal from the oscillator and to process a measurement signal received from the eddy current sensor of the sensor head.

[0008] In the above embodiment, the eddy current sensors in some of the plurality of sensor heads may have different sensor characteristics from the eddy current sensors in other parts of the plurality of sensor heads.

[0009] In the above embodiment, the eddy current sensor in a portion of the plurality of sensor heads is The sensor may correspond to a different film type than the eddy current sensor in some of the other sensor heads.

[0010] In the above embodiment, the eddy current sensors in some of the plurality of sensor heads may be sensors corresponding to different film thicknesses than the eddy current sensors in other parts of the plurality of sensor heads.

[0011] In the above embodiment, the eddy current sensors in some of the plurality of sensor heads may be sensors having a different spatial resolution than the eddy current sensors in other parts of the plurality of sensor heads.

[0012] In the above embodiment, the control unit may include a switching unit that switches the sensor head so that an eddy current sensor with optimal sensor characteristics is used according to the polishing recipe. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram showing the configuration of a polishing apparatus according to one embodiment of the present invention. [Figure 2] This is a schematic diagram showing the configuration of a film thickness measurement system mounted on a polishing apparatus according to one embodiment of the present invention. [Figure 3] This is a schematic diagram showing the configuration of a conventional film thickness measurement system. [Figure 4A] This figure shows an example configuration of multiple sensor heads in a film thickness measurement system according to one embodiment of the present invention. [Figure 4B] This figure shows an example configuration of multiple sensor heads in a film thickness measurement system according to one embodiment of the present invention. [Figure 5] This figure shows an example of arranging multiple sensor heads on a polishing table in a film thickness measurement system according to one embodiment of the present invention. [Modes for carrying out the invention]

[0014] Embodiments of the present invention will be described below with reference to the drawings. In the drawings described below, the same or corresponding components are denoted by the same reference numerals, and redundant descriptions are omitted.

[0015] Figure 1 is a schematic diagram showing the configuration of a polishing apparatus 10 according to one embodiment of the present invention. As shown in the figure, the polishing apparatus 10 includes a polishing table 30 for holding a polishing pad 31, and a top ring 40 (polishing head) for holding a substrate (wafer Wf), which is the object to be polished, so as to face the polishing pad 31 and pressing it against the polishing surface of the polishing pad 31.

[0016] The polishing table 30 is connected via a table shaft 32 to a table drive motor (not shown) located below it. The rotational drive of the table drive motor allows the polishing table 30 to rotate around the axis of the table shaft 32. A polishing pad 31 is attached to the upper surface of the polishing table 30. The surface 311 of the polishing pad 31 constitutes the polishing surface for polishing the wafer Wf. A polishing liquid supply nozzle (not shown) is installed above the polishing table 30, and polishing liquid is supplied from the polishing liquid supply nozzle to the polishing pad 31 on the polishing table 30.

[0017] An eddy current sensor 80 is provided inside the polishing table 30. The eddy current sensor 80 is positioned so that it passes through the center of the wafer Wf as the polishing table 30 rotates during polishing. The eddy current sensor 80 is connected to the control unit 100 via a signal cable 81. The eddy current sensor 80 is configured to induce eddy currents in the conductive film on the surface of the wafer Wf. The eddy current sensor 80 further responds to the change in impedance caused by the magnetic field generated by the eddy currents, and the thickness of the conductive film on the surface of the wafer Wf It is configured to output a corresponding signal. By using the output signal from this eddy current sensor 80, the thickness of the conductive film on the surface of the wafer Wf can be determined. Although only one eddy current sensor 80 is shown in Figure 1, multiple eddy current sensors 80 may be provided inside the polishing table 30, as shown in Figures 2 and 5 below.

[0018] The top ring 40 is supported by an arm 50 via a top ring shaft 42. The top ring shaft 42 can move up and down with respect to the arm 50 by a vertical movement mechanism (not shown). By moving the top ring shaft 42 up and down, the top ring 40 can be raised and lowered with respect to the arm 50 and positioned. The top ring 40 is configured to hold the wafer Wf on its lower surface. Specifically, as shown in FIG. 1, the top ring 40 includes a retainer ring 41A that holds the outer peripheral edge of the wafer Wf so that the wafer Wf does not protrude from the top ring 40, and a top ring body 41B that presses the wafer Wf against the polishing surface 311.

[0019] A top ring drive motor 43 is fixed to the arm 50 that supports the top ring 40. Also, as shown in FIG. 1, the top ring shaft 42 is connected to a rotating cylinder 61, and a timing pulley 62 provided on the outer peripheral portion of the rotating cylinder 61 is connected to a timing pulley 64 provided on the top ring drive motor 43 via a timing belt 63. Thus, when the top ring drive motor 43 rotates, the rotating cylinder 61 and the top ring shaft 42 rotate integrally via the timing pulley 64, the timing belt 63, and the timing pulley 62, and the top ring 40 rotates around the axis of the top ring shaft 42.

[0020] The arm 50 is connected to an arm drive motor 53 fixed to an arm shaft 52. By driving the arm drive motor 53, the arm 50 and the top ring 40 supported by the arm 50 can pivot around the axis of the arm shaft 52.

[0021] When the polishing apparatus 10 operates, first, the wafer Wf conveyed by a conveyance mechanism (not shown) is received and held by the top ring 40 at a predetermined receiving position. The top ring 40 that has received the wafer Wf at the receiving position is moved from the receiving position above the polishing table 30 by the turning of the arm 50. Next, the top ring shaft 42 and the top ring 40 descend, and the wafer Wf is pressed against the polishing surface 311 of the polishing pad 31. Then, when the table drive motor and the top ring drive motor 43 are rotationally driven, the polishing table 30 and the top ring 40 rotate respectively, and at the same time, polishing liquid is supplied onto the polishing pad 31 from a polishing liquid supply nozzle provided above the polishing table 30. Thereby, the wafer Wf is in sliding contact with the polishing surface 311 of the polishing pad 31, and the surface of the wafer Wf is polished. During the polishing of the wafer Wf, the arm drive motor 53 may periodically swing the arm 50 left and right to polish while swinging the top ring 40 with respect to the polishing pad 31 (that is, while reciprocating on the polishing pad 31).

[0022] FIG. 2 is a schematic diagram showing the configuration of a film thickness measurement system 20 mounted on a polishing apparatus 10 according to an embodiment of the present invention. The film thickness measurement system 20 is a system for measuring the film thickness of a conductive film on a wafer Wf polished by the polishing apparatus 10, and includes a plurality of sensor heads (eddy current sensors) 80 and a control unit 100 for controlling these plurality of sensor heads 80.

[0023] Each of the plurality of sensor heads (eddy current sensors) 80 includes a sensor coil 81 and an impedance matching resistor 82 respectively. Each sensor head (eddy current sensor) 80 is installed inside the polishing table 30 as described above. The sensor coil 81 of each sensor head 80 generates a magnetic field in response to a drive signal from the control unit 100<{ to generate eddy currents in the conductive film on the surface of the wafer Wf, and generates a signal corresponding to the thickness of the conductive film on the surface of the wafer Wf in response to a change in the circuit impedance caused by the eddy currents.

[0024] The control unit 100 includes a drive circuit 100A and a detection circuit 100B. The drive circuit 100A includes an oscillator 110, a distributor 120, a plurality of frequency multiplier circuits 130, a plurality of phase shifters 140, a switching circuit 150, a plurality of variable attenuators 160, a plurality of fixed amplifiers 170, and a plurality of impedance matching resistors 180. The detection circuit 100B includes a plurality of impedance matching resistors 185, a plurality of AD (analog-to-digital) converters 190, and a signal processing circuit 195. The frequency multiplier circuits 130, phase shifters 140, variable attenuators 160, fixed amplifiers 170, impedance matching resistors 180 and 185, and AD converters 190 are provided corresponding to each of the plurality of sensor heads 80.

[0025] Each element constituting the drive circuit 100A (oscillator 110, distributor 120, multiplier circuit 130, etc.) may be housed in a single enclosure (e.g., a metal enclosure). Similarly, each element constituting the detection circuit 100B (signal processing circuit 195, AD converter 190, impedance matching resistor 185) may be housed in a single enclosure (e.g., a metal enclosure). All elements constituting the drive circuit 100A and the detection circuit 100B may be housed in a single enclosure (e.g., a metal enclosure).

[0026] The oscillator 110 generates a common clock signal (for example, a high-frequency signal with a frequency of 1 MHz) to drive multiple eddy current sensors 80. The distributor 120 distributes the clock signal from the oscillator 110 to multiple frequency multiplier circuits 130. Each frequency multiplier circuit 130 multiplies the clock signal distributed from the distributor 120 to a frequency that matches the operating frequency band of the eddy current sensor 80 corresponding to that frequency multiplier circuit 130. Each phase shifter 140 applies a phase shift for synchronous detection to the signal from the corresponding frequency multiplier circuit 130.

[0027] The switching circuit 150 is a circuit for selecting and activating the drive signal for the eddy current sensor 80 that will actually be used from among the multiple eddy current sensors 80 provided on the polishing table 30. Specifically, the switching circuit 150 supplies a signal from the phase shifter 140 to the variable attenuator 160 corresponding to the eddy current sensor 80 that will actually be used, and does not supply a signal from the phase shifter 140 to the variable attenuator 160 corresponding to the eddy current sensor 80 that will not be used. The number of drive signals to be activated may be one or multiple. The selection of drive signals may be performed, for example, according to a pre-created recipe.

[0028] One or more drive signals activated by the switching circuit 150 are adjusted to a predetermined signal strength via the variable attenuator 160 and the fixed amplifier 170 and supplied to the corresponding eddy current sensor 80. In response to the magnetic field generated from the sensor coil 81 of the eddy current sensor 80 and the generation of eddy currents in the conductive film on the wafer Wf, a detection signal corresponding to the thickness of the conductive film is output from the eddy current sensor 80. The signal from the eddy current sensor 80 is input to the signal processing circuit 195 via the AD converter 190. The signal processing circuit 195 calculates the thickness of the conductive film on the surface of the wafer Wf by performing calculations on the detection signal from the eddy current sensor 80.

[0029] Figure 3 is a schematic diagram showing the configuration of a conventional film thickness measurement system 21. The film thickness measurement system 21 comprises a plurality of sensor units 80'. Each sensor unit 80' comprises a distributor 120, a multiplier circuit 130, a phase shifter 140, a variable amplifier 170, a sensor coil 81, a buffer circuit 186, an AD converter 190, and a signal processing circuit 195. In addition, one of the sensor units 80' further comprises an oscillator 110. Each element in the sensor unit 80' corresponds to the film thickness measurement described in Figure 2 above. This is similar to the one in System 20.

[0030] In the film thickness measurement system 21 shown in Figure 3, the elements constituting each sensor unit 80' are housed in a separate housing (e.g., a metal housing) for each sensor unit. Therefore, the signal line 122 for transmitting the clock signal distributed from the distributor 120 to another sensor unit 80' passes outside the housing. Consequently, there is a possibility that noise from the external environment may be introduced into the clock signal in the portion of the signal line 122 outside the housing.

[0031] In contrast, in the film thickness measurement system 20 with the configuration shown in Figure 2 according to one embodiment of the present invention, the signal line through which the clock signal is transmitted is prevented from being exposed to external environmental noise. Therefore, it is possible to avoid a decrease in clock signal quality due to noise interference and improve the accuracy of film thickness measurement in the film thickness measurement system 20 using the eddy current sensor 80.

[0032] Furthermore, the sensor head 80 in the film thickness measurement system 20 according to one embodiment of the present invention has fewer parts than the sensor unit 80' in the conventional film thickness measurement system 21, so the sensor head 80 is smaller than the sensor unit 80'. Therefore, in the polishing apparatus 10 shown in Figure 1, which is equipped with the film thickness measurement system 20 according to one embodiment of the present invention, more sensor heads (eddy current sensors) 80 can be installed on the polishing table 30.

[0033] Figures 4A and 4B show examples of configurations of multiple sensor heads 80 in a film thickness measurement system 20 according to one embodiment of the present invention. In the example in Figure 4A, a control unit 100 is connected to a type 1 sensor head 80A, a type 2 sensor head 80B, a type 3 sensor head 80C, and a type 4 sensor head 80D. Each type of sensor head (eddy current sensor) 80A, 80B, 80C, and 80D has different sensor characteristics. Specifically, the type 2 sensor head 80B has sensor characteristics suitable for measuring thick films of film type 1 (e.g., Cu (copper)). The type 3 sensor head 80C has sensor characteristics suitable for measuring thin films of film type 1. The type 1 sensor head 80A is suitable for measuring films of film type 1 with a wide range of thicknesses from thin films to thick films, and has sensor characteristics that provide high spatial resolution for measurement (i.e., a small spot diameter of the magnetic field emitted from the sensor coil 81) and excellent detection performance of film edges. The Type 4 sensor head 80D has sensor characteristics suitable for measuring films of film type 2 (e.g., W (tungsten)) with a wide range of thicknesses, from thin films to thick films.

[0034] With the configuration of multiple sensor heads 80 shown in Figure 4A, it becomes possible to flexibly measure the film thickness of various types of films by switching the sensor head 80 to be used in the switching circuit 150 according to a pre-prepared recipe depending on the type of wafer Wf to be polished.

[0035] In the example shown in Figure 4B, the control unit 100 is connected to three Type 1 sensor heads 80A and two Type 3 sensor heads 80C. In this example, the accuracy of the film thickness calculation can be improved by using multiple sensor heads 80 of the same type simultaneously and having the signal processing circuit 195 calculate the film thickness based on the signals from these multiple sensor heads 80.

[0036] Figure 5 shows examples of arrangements of multiple sensor heads 80 on a polishing table 30 in a film thickness measurement system 20 according to one embodiment of the present invention. In arrangement example 1, one sensor head 80A of type 1 and one sensor head 80B of type 2 are installed on the polishing table 30. In arrangement example 2, two sensor heads 80A of type 1 and one sensor head 80C of type 3 are installed on the polishing table 30. In arrangement example 3, The polishing table 30 is equipped with three Type 1 sensor heads 80A and one Type 2 sensor head 80B. In addition, in arrangement example 3, a pressure sensor 85 may be installed on the polishing table 30. The pressure sensor 85 is for detecting the pressing force of the wafer Wf held by the top ring 40 against the polishing table 30. In addition to the pressure sensor 85, or in place of the pressure sensor 85, a temperature sensor may be installed to measure the temperature of the wafer Wf during polishing. In arrangement example 4, the polishing table 30 is equipped with three Type 1 sensor heads 80A, one Type 2 sensor head 80B, and three Type 3 sensor heads 80C. In arrangement example 5, the polishing table 30 is equipped with four Type 1 sensor heads 80A, four Type 3 sensor heads 80C, and four Type 4 sensor heads 80D. In this way, by installing multiple types of sensor heads 80 (sensor heads 80A, 80B, 80C, and 80D) with different sensor characteristics on the polishing table 30 and using the switching circuit 150 to select and use them as appropriate (for example, according to a pre-prepared recipe depending on the wafer Wf to be polished), film thickness measurement can be flexibly performed on various types of wafer Wf.

[0037] While embodiments of the present invention have been described above based on several examples, the embodiments described above are intended to facilitate understanding of the present invention and do not limit it. The present invention can be modified and improved without departing from its spirit, and of course, its equivalents are included. Furthermore, any combination or omission of the components described in the claims and specification is possible to the extent that at least some of the above-mentioned problems can be solved or at least some of the effects can be achieved. [Explanation of symbols]

[0038] 10 Polishing equipment 20 Film Thickness Measurement System 30 polishing tables 31 polishing pads 311 Polished surface 32 Table shaft 40 Top Ring 41A Retainer Ring 41B Top Ring Body 42 Top Ring Shaft 43 Top ring drive motor 50 Arm 52 Arm Shaft 53 Arm drive motor 61 Rotating Cylinder 62 Timing Pulley 63 Timing belt 64 Timing Pulley 80 Eddy current sensor (sensor head) 81 Sensor coil 82 Impedance matching resistors 100 control units 100A drive circuit 100B detection circuit 110 Oscillator 120 Distributor 130 Multiplier Circuit 140 Phase Shifter 150 switching circuit 160 Variable Attenuator 170 Fixed Amplifier 180 Impedance matching resistor 185 Impedance matching resistor 190 AD Converter 195 Signal Processing Circuits

Claims

1. A polishing apparatus for polishing an object to be polished, A polishing head configured to be able to attach the workpiece to be polished, A polishing table is positioned opposite the workpiece to be polished, which is attached to the polishing head, and is configured to be rotatable. A film thickness measuring system for measuring the film thickness of a conductive film on an object to be polished by the polishing apparatus, Equipped with, The aforementioned film thickness measurement system is A plurality of sensor heads arranged on the polishing table, each sensor head consisting of an eddy current sensor, Control unit and Equipped with, The control unit is An oscillator that generates a common clock signal for driving the eddy current sensor, A plurality of control circuits provided corresponding to each of the plurality of sensor heads, each control circuit configured to generate a drive signal to the eddy current sensor of the sensor head based on the clock signal from the oscillator, and to process the measurement signal received from the eddy current sensor of the sensor head, A polishing device equipped with the following features.

2. The polishing apparatus according to claim 1, wherein the eddy current sensor in a portion of the plurality of sensor heads has different sensor characteristics from the eddy current sensor in another portion of the plurality of sensor heads.

3. The polishing apparatus according to claim 2, wherein the eddy current sensor in a portion of the plurality of sensor heads is a sensor corresponding to a different film type than the eddy current sensor in another portion of the plurality of sensor heads.

4. The polishing apparatus according to claim 2, wherein the eddy current sensor in a portion of the plurality of sensor heads is a sensor corresponding to a different film thickness than the eddy current sensor in another portion of the plurality of sensor heads.

5. The polishing apparatus according to claim 2, wherein the eddy current sensor in a portion of the plurality of sensor heads is a sensor having a different spatial resolution than the eddy current sensor in another portion of the plurality of sensor heads.

6. The polishing apparatus according to any one of claims 2 to 5, wherein the control unit includes a switching unit that switches the sensor head so that an eddy current sensor with optimal sensor characteristics is used according to the polishing recipe.

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