Plating device

Abstract

The present invention makes it possible to determine with high precision the film thickness of plating formed on a substrate in a plating device.　This plating device comprises: a plating tank for storing a plating solution; a substrate holder for holding a substrate; an anode arranged in the plating tank so as to face the substrate held by the substrate holder; a potential sensor arranged in the vicinity of the substrate held by the substrate holder and configured to measure the potential of the plating solution; a database for storing reference data regarding the distribution of the potential in the vicinity of the substrate, the reference data representing the potential distribution in the vicinity of the substrate in a predetermined reference state; a potential deviation calculation unit configured to calculate deviation of the potential distribution measured by the potential sensor with respect to the reference data; and a film thickness calculation unit configured to calculate deviation in the film thickness of the plating formed on the substrate from the film thickness of the plating in the reference state on the basis of the calculated deviation of the potential distribution.

Description

Plating Equipment

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

[0002] The plating apparatus includes a substrate holder for holding a substrate, a plating tank containing a plating solution, and an anode disposed in the plating tank so as to face the substrate held by the substrate holder.Technical developments have been made to improve the flatness of the film thickness of the plating formed on the substrate in the plating apparatus (see, for example, Patent Document 1).

[0003] Patent No. 7373684

[0004] In a plating apparatus, it is desirable to grasp the thickness of a plating film formed on a substrate with higher accuracy.

[0005] [Mode 1] According to mode 1, there is provided a plating apparatus including: a plating tank for containing a plating solution; a substrate holder for holding a substrate; an anode arranged in the plating tank so as to face the substrate held in the substrate holder; a potential sensor arranged near the substrate held in the substrate holder and configured to measure the potential of the plating solution; a database storing reference data of the potential distribution in the vicinity of the substrate, the reference data representing the potential distribution in the vicinity of the substrate in a predetermined reference state; a potential deviation calculation unit configured to calculate a deviation of the potential distribution measured by the potential sensor from the reference data; and a film thickness calculation unit configured to calculate a deviation of a plating film thickness formed on the substrate from a plating film thickness in the reference state based on the calculated deviation of the potential distribution.

[0006] [Form 2] According to form 2, in the plating apparatus of form 1, the reference data includes a plurality of reference data corresponding to different plating current values, and the potential deviation calculation unit is configured to calculate the deviation of the potential distribution using data interpolated from the plurality of reference data.

[0007] [Mode 3] According to mode 3, in the plating apparatus of mode 2, the interpolated data corresponds to the value of the plating current when the potential is measured by the potential sensor.

[0008] [Form 4] According to form 4, in the plating apparatus of form 1, the reference data includes a plurality of reference data corresponding to the micro-machined pattern on the substrate, and the potential deviation calculation unit is configured to calculate the deviation of the potential distribution using reference data from the plurality of reference data corresponding to the micro-machined pattern on the substrate during plating processing that is the target of potential measurement by the potential sensor.

[0009] [Mode 5] According to mode 5, in the plating apparatus of mode 1, the predetermined reference state is a state in which there is no power supply failure at least between the substrate and the substrate holder.

[0010] [Mode 6] According to Mode 6, in the plating apparatus of Mode 1, the predetermined reference state corresponds to a state in which a plating film is formed with a flatness higher than a predetermined threshold value.

[0011] [Mode 7] According to mode 7, the plating apparatus of mode 1 further includes a plating process control unit configured to perform control in accordance with the deviation in the plating film thickness calculated by the film thickness calculation unit.

[0012] [Form 8] According to Form 8, in the plating apparatus of Form 7, the control includes at least one of (i) issuing an alarm, (ii) controlling the rotation of the substrate holder, (iii) controlling the position of a shield for partially shielding the plating current in the plating solution, and (iv) controlling the agitation of the plating solution.

[0013] [Mode 9] According to Mode 9, the plating apparatus of Mode 1 further comprises: a state space model configured to estimate a current density flowing through an outer edge portion of the substrate using a state equation and an observation equation, wherein the state equation is an equation describing the time evolution of the current density flowing through the outer edge portion of the substrate, and the observation equation is an equation describing the relationship between the current density flowing through the outer edge portion of the substrate and the potential of the plating solution at the position of the potential sensor; and a current density calculation unit configured to calculate a plating current density in a region inside the outer edge portion of the substrate based on the current density estimated by the state space model, wherein an output from the potential deviation calculation unit is input to the state space model, and an output from the current density calculation unit is input to the film thickness calculation unit.

[0014] [Form 10] According to form 10, the plating apparatus of form 9 is provided with a plating module including at least the plating tank, the substrate holder, the anode, and the potential sensor, and the relationship between the current density and the potential of the plating solution is based on a function representing a 3D model of the plating module.

[0015] [Form 11] According to form 11, in the plating apparatus of form 9, the state space model further includes a Kalman filter configured to correct the estimated result of the current density flowing through the outer edge of the substrate based on the measurement value of the potential sensor.

[0016] [Mode 12] According to Mode 12, in the plating apparatus of Mode 9, the outer edge portion of the substrate is a portion of the substrate that is gripped by the substrate holder.

[0017] 1 is a perspective view showing the overall configuration of the plating apparatus of the present embodiment; FIG. 2 is a plan view showing the overall configuration of the plating apparatus of the present embodiment; FIG. 3 is a longitudinal sectional view showing the schematic configuration of a plating module in one embodiment; FIG. 4 is a plan view seen from the IV-IV direction in FIG. 3; FIG. 5 is a schematic view of a shield and a substrate seen from below; FIG. 6 is a block diagram showing the functional configuration of a control module according to one embodiment; FIG. 7 is a plan view of a substrate; FIG. 8 is a block diagram showing the functional configuration of a control module according to another embodiment; FIG. 9 is a diagram conceptually showing processing by a potential deviation calculation unit; FIG. 10 is a diagram showing an exemplary database storing a plurality of reference data; and FIG. 11 is a diagram explaining interpolation of reference data.

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings described below, the same or corresponding components are designated by the same reference numerals, and redundant description will be omitted.

[0019] <First Embodiment> Fig. 1 is a perspective view showing the overall configuration of a plating apparatus of this embodiment. Fig. 2 is a plan view showing the overall configuration of the plating apparatus of this embodiment. As shown in Figs. 1 and 2, a plating apparatus 1000 includes a load port 100, a transfer robot 110, an aligner 120, a pre-wet module 200, a pre-soak module 300, a plating module 400, a cleaning module 500, a spin rinse dryer 600, a transfer device 700, and a control module 800.

[0020] The load port 100 is a module for loading substrates stored in a cassette such as a FOUP (not shown) into the plating apparatus 1000 and unloading substrates from the plating apparatus 1000 to the cassette. In this embodiment, four load ports 100 are arranged horizontally, but the number and arrangement of the load ports 100 are optional. The transfer robot 110 is a robot for transporting substrates and is configured to transfer substrates between the load port 100, the aligner 120, and the transfer device 700. When transferring substrates between the transfer robot 110 and the transfer device 700, the transfer robot 110 and the transfer device 700 can transfer the substrates via a temporary stage (not shown).

[0021] The aligner 120 is a module for aligning the positions of the substrate's orientation flat, notch, and the like in a predetermined direction. In this embodiment, two aligners 120 are arranged horizontally, but the number and arrangement of the aligners 120 are optional. The prewet module 200 wets the surface of the substrate to be plated with a treatment liquid such as pure water or degassed water before plating, thereby replacing air within the pattern formed on the substrate surface with the treatment liquid. The prewet module 200 is configured to perform a prewet process that replaces the treatment liquid within the pattern with a plating liquid during plating, thereby making it easier to supply the plating liquid within the pattern. In this embodiment, two prewet modules 200 are arranged vertically, but the number and arrangement of the prewet modules 200 are optional.

[0022] The presoak module 300 is configured to perform a presoak process, which involves etching away, for example, an oxide film with high electrical resistance present on the surface of a seed layer formed on the surface of a substrate to be plated before plating, using a treatment solution such as sulfuric acid or hydrochloric acid to clean or activate the surface of the substrate to be plated. In this embodiment, two presoak modules 300 are arranged vertically, but the number and arrangement of the presoak modules 300 are optional. The plating module 400 performs plating on the substrate. In this embodiment, two sets of 12 plating modules 400 are arranged vertically, three vertically and four horizontally, for a total of 24 plating modules 400, but the number and arrangement of the plating modules 400 are optional.

[0023] The cleaning module 500 is configured to perform a cleaning process on the substrate to remove plating solution and the like remaining on the substrate after plating. In this embodiment, two cleaning modules 500 are arranged vertically, but the number and arrangement of the cleaning modules 500 are optional. The spin rinse dryer 600 is a module for drying the substrate after cleaning by rotating it at high speed. In this embodiment, two spin rinse dryers are arranged vertically, but the number and arrangement of the spin rinse dryers are optional. The transport device 700 is a device for transporting substrates between multiple modules within the plating apparatus 1000. The control module 800 is configured to control the multiple modules of the plating apparatus 1000 and can be configured, for example, as a general computer or a dedicated computer equipped with an input / output interface with an operator.

[0024] An example of a series of plating processes performed by the plating apparatus 1000 will be described. First, a substrate stored in a cassette is loaded into the load port 100. Next, the transfer robot 110 removes the substrate from the cassette in the load port 100 and transfers the substrate to the aligner 120. The aligner 120 aligns the positions of the orientation flat, notch, etc. of the substrate to a predetermined direction. The transfer robot 110 delivers the substrate, whose direction has been aligned by the aligner 120, to the transfer apparatus 700.

[0025] The transfer device 700 transfers the substrate received from the transfer robot 110 to the prewet module 200. The prewet module 200 performs a prewet process on the substrate. The transfer device 700 transfers the substrate that has been subjected to the prewet process to the presoak module 300. The presoak module 300 performs a presoak process on the substrate. The transfer device 700 transfers the substrate that has been subjected to the presoak process to the plating module 400. The plating module 400 performs a plating process on the substrate.

[0026] The transfer device 700 transfers the substrate that has been plated to the cleaning module 500. The cleaning module 500 performs a cleaning process on the substrate. The transfer device 700 transfers the substrate that has been cleaned to the spin rinse dryer 600. The spin rinse dryer 600 dries the substrate. The transfer device 700 delivers the substrate that has been dried to the transfer robot 110. The transfer robot 110 transfers the substrate received from the transfer device 700 to a cassette on the load port 100. Finally, the cassette containing the substrate is removed from the load port 100.

[0027] It should be noted that the configuration of the plating apparatus 1000 described in FIGS. 1 and 2 is merely an example, and the configuration of the plating apparatus 1000 is not limited to the configurations shown in FIGS.

[0028] Next, the configuration of the plating module 400 will be described. Since the 24 plating modules 400 in this embodiment have the same configuration, only one plating module 400 will be described. FIG. 3 is a longitudinal cross-sectional view schematically showing the configuration of the plating module 400 according to one embodiment. The plating module 400 includes a plating tank for containing a plating solution. The plating tank includes a cylindrical inner tank 412 with an open top, and an outer tank (not shown) provided around the inner tank 412 to collect plating solution that overflows from the upper edge of the inner tank 412.

[0029] The plating module 400 includes a substrate holder 440 for holding the substrate Wf with its plating surface Wf-a facing downward. The substrate holder 440 includes a power supply contact for supplying power to the substrate Wf from a power source (not shown). The plating module 400 also includes a lifting mechanism 442 for raising and lowering the substrate holder 440. In one embodiment, the plating module 400 also includes a rotation mechanism 448 for rotating the substrate holder 440 about a vertical axis. The rotation mechanism 448 can rotate the substrate holder 440 in a forward direction (e.g., clockwise) and a reverse direction (e.g., counterclockwise), and the rotation speed can also be changed. Such rotation of the substrate holder 440 is controlled by the control module 800. The lifting mechanism 442 and the rotation mechanism 448 can be realized by known mechanisms, such as motors.

[0030] The plating module 400 includes a membrane 420 that vertically separates the interior of the inner tank 412. The interior of the inner tank 412 is divided by the membrane 420 into a cathode region 422 and an anode region 424. The cathode region 422 and the anode region 424 are each filled with a plating solution. Note that, although an example in which the membrane 420 is provided has been shown in this embodiment, the membrane 420 need not be provided.

[0031] An anode 430 is provided on the bottom surface of the inner tank 412 in the anode region 424. An anode mask 426 is also provided in the anode region 424 to adjust the electric field between the anode 430 and the substrate Wf. The anode mask 426 is, for example, a substantially plate-shaped member made of a dielectric material and is provided in front of the anode 430 (above the anode 430 in FIG. 3 ). The anode mask 426 has an opening through which a current flows between the anode 430 and the substrate Wf. The anode mask 426 is configured to have changeable opening dimensions, and the opening dimensions may be adjusted by the control module 800. The opening dimension refers to the diameter if the opening is circular, and to the length of one side or the longest opening width if the opening is polygonal. A known mechanism can be used to change the opening dimensions of the anode mask 426. Although the present embodiment illustrates an example in which the anode mask 426 is provided, the anode mask 426 need not be provided. Furthermore, the membrane 420 described above may be provided in the opening of the anode mask 426 .

[0032] A resistor 450 is disposed in the cathode region 422 so as to face the membrane 420. The resistor 450 is a member for achieving uniformity in the plating process on the plating surface Wf-a of the substrate Wf. In one embodiment, the resistor 450 is configured to be movable up and down within the plating tank by a drive mechanism 452, and the position of the resistor 450 is adjusted by the control module 800. However, the plating module 400 does not necessarily have to include the resistor 450. The specific material of the resistor 450 is not particularly limited, but as an example, a porous resin such as polyether ether ketone can be used.

[0033] A paddle (not shown) for stirring the plating solution is provided near the surface of the substrate Wf in the cathode region 422. The paddle is made of, for example, titanium (Ti) or resin. The paddle reciprocates parallel to the surface of the substrate Wf to stir the plating solution so that sufficient metal ions are uniformly supplied to the surface of the substrate Wf during plating of the substrate Wf. The paddle may be configured to move perpendicular to the surface of the substrate Wf. The movement of the paddle is controlled by the control module 800 using a drive mechanism (not shown). Note that the plating module 400 does not necessarily have a paddle.

[0034] A potential sensor 470 is also provided in the cathode region 422. If the cathode region 422 is provided with a resistor 450, the potential sensor 470 may be provided between the substrate Wf and the resistor 450. The potential sensor 470 is supported by a sensor support 468. The potential sensor 470 may be supported by the sidewall of the inner tank 412 or the resistor 450 instead of the sensor support 468. The sensor support 468 may also be a paddle for stirring the plating solution. Preferably, the paddle stirs the plating solution by moving parallel to the surface of the substrate Wf, but this is not a limitation. In this embodiment, multiple potential sensors 470 are provided along the radial direction of the substrate Wf. However, this is not a limitation, and at least one potential sensor 470 may be provided in the plating module 400.

[0035] 4 is a plan view seen from the direction IV-IV in FIG. 3. As shown in FIGS. 3 and 4, the potential sensor 470 is disposed at a first position in the region between the substrate Wf and the anode 430. That is, the potential sensor 470 is located between the substrate Wf and the anode 430 in a direction perpendicular to the surface of the substrate Wf, and is disposed at a position overlapping the substrate Wf when viewed from the direction perpendicular to the surface of the substrate Wf. The potential sensor 470 is preferably disposed close to the plating surface Wf-a. For example, the distance between the potential sensor 470 and the plating surface Wf-a is several hundred micrometers, several millimeters, or several tens of millimeters. The potential sensor 470 detects the potential at its location (first position) between the substrate Wf and the anode 430.

[0036] A second potential sensor 472a and a third potential sensor 472b may be provided in the plating tank 410. The second potential sensor 472a and the third potential sensor 472b are disposed in a location in the plating tank 410 where the potential change is relatively small. Specifically, the second potential sensor 472a and the third potential sensor 472b are disposed at a second position and a third position outside the area between the substrate Wf and the anode 430. That is, as shown in FIG. 4 , the second potential sensor 472a and the third potential sensor 472b are disposed at positions that do not overlap with the substrate Wf when viewed in a direction perpendicular to the surface of the substrate Wf. The second potential sensor 472a and the third potential sensor 472b detect the potential at positions (the second position and the third position) away from the area between the substrate Wf and the anode 430. The second and third potential sensors 472a and 472b are supported by sensor supports 469a and 469b. The second and third potential sensors 472a and 472b may be supported on the side wall of the inner tank 412 or the resistor 450 instead of the sensor supports 469a and 469b.

[0037] For example, the potential sensor 470, the second potential sensor 472a, and the third potential sensor 472b may each be configured with electrodes of the same material and / or the same shape, and the electrode material may be at least one of platinum (Pt), gold (Au), carbon (C), and copper (Cu).

[0038] Detection signals from the potential sensor 470, the second potential sensor 472 a, and the third potential sensor 472 b are input to the control module 800. The control module 800 can estimate the film thickness of the plating formed on the substrate Wf based on the potential detection value from the potential sensor 470 or based on the detection signals from the potential sensor 470, the second potential sensor 472 a, and the third potential sensor 472 b. As an example, the control module 800 can estimate the distribution of the plating current within the surface of the substrate during the plating process based on the detection signal from the potential sensor 470, and estimate the film thickness distribution of the plating film on the substrate based on the estimated plating current distribution.

[0039] Furthermore, the control module 800 may detect the end point of the plating process or may predict the time until the end point of the plating process based on the detection value of the potential sensor 470. As an example, the control module 800 may terminate the plating process when the thickness of the plating film estimated based on the detection value of the potential sensor 470 reaches a desired thickness. As another example, the control module 800 may calculate a film thickness increase rate from the film thickness of the plating film estimated based on the detection value of the potential sensor 470, and predict the time until the plating film reaches the desired thickness, i.e., the time until the end point of the plating process, based on the obtained film thickness increase rate.

[0040] Returning to FIG. 3 , in one embodiment, a shield 480 is provided in the cathode region 422 to partially or locally shield the current flowing from the anode 430 to the substrate Wf. The shield 480 is, for example, a substantially plate-shaped member made of a dielectric material. FIG. 5 is a schematic diagram of the shield 480 and the substrate Wf of this embodiment, viewed from below. Note that FIG. 5 does not illustrate the substrate holder 440 that holds the substrate Wf. The shield 480 is configured to be movable between a shielding position (position indicated by a dashed line in FIGS. 3 and 5 ) interposed between the plating surface Wf-a of the substrate Wf and the anode 430, and a retracted position (position indicated by a solid line in FIGS. 3 and 5 ) retracted from between the plating surface Wf-a and the anode 430. In other words, the shield 480 is configured to be movable between a shielding position below the plating surface Wf-a and a retracted position away from the plating surface Wf-a. The position of the shield 480 is controlled by the control module 800 using a drive mechanism (not shown). The movement of the shield 480 can be achieved by a known mechanism such as a motor or solenoid. In the examples shown in FIGS. 3 and 5, the shield 480 shields a portion of the circumferential direction of the outer peripheral region of the plating surface Wf-a of the substrate Wf when in the shielding position. In addition, in the example shown in FIG. 5, the shield 480 is formed in a tapered shape that narrows toward the center of the substrate Wf. However, the shield 480 is not limited to this example, and any shape predetermined by experiment or the like can be used.

[0041] The plating process in the plating module 400 will now be described. The substrate Wf is exposed to the plating solution by immersing it in the plating solution in the cathode region 422 using the lifting mechanism 442. In this state, the plating module 400 applies a voltage between the anode 430 and the substrate Wf, thereby plating the surface Wf-a of the substrate Wf to be plated. In one embodiment, the plating process is performed while the substrate holder 440 is rotated using the rotation mechanism 448. A conductive film (plating film) is deposited on the surface Wf-a of the substrate Wf to be plated by the plating process. During the plating process, the potential sensor 470 measures the potential. By performing measurements using the potential sensor 470 while the substrate holder 440 (substrate Wf) is rotated, the measurement position of the potential sensor 470 can be changed, allowing the potential to be measured at multiple points around the circumference of the substrate Wf or across the entire circumference. The control module 800 then estimates the thickness of the plating film based on the potential detected by the potential sensor 470. This makes it possible to grasp in real time the change in the thickness of the plating film formed on the plating surface Wf-a of the substrate Wf during the plating process.

[0042] 6 is a block diagram showing the functional configuration of a control module 800 according to one embodiment of the plating apparatus 1000. The control module 800 is configured to estimate the distribution of current density flowing through the substrate Wf during plating processing using a state space model 804. The state space model 804 includes a state estimation unit 806, an observation value calculation unit 808, and a Kalman filter 810. In addition to the state space model 804, the control module 800 also includes a 3D model creation unit 802, a current density calculation unit 812, a film thickness calculation unit 814, and an endpoint determination unit 816. The control module 800 can be configured as a computer including an input / output device, an arithmetic unit, a storage device, and the like. For example, the control module 800 is configured to realize the functions of each unit 802, 806, 808, 810, 812, 814, and 816 by having the arithmetic unit (e.g., a processor) read and execute a computer program stored in the storage device.

[0043] The 3D model creation unit 802 creates a three-dimensional (3D) model of the plating module 400. The 3D model of the plating module 400 is data that model and describe the shapes, arrangements, physical properties, etc. of various components in the plating module 400. This 3D model incorporates at least components that affect the electric field inside the plating tank (inner tank 412) of the plating module 400. Such components include, for example, the anode 430, the anode mask 426, the membrane 420, the resistor 450, the substrate Wf, the seed layer provided on the substrate Wf, the plating solution contained in the plating tank, and the potential sensor 470. The 3D model of the plating module 400 can be configured using information on the shape, arrangement, and physical properties (e.g., conductivity, dielectric constant, etc.) of each of these components. As an example, the information may be input to the control module 800 by an operator of the plating apparatus 1000 via an input / output interface of the control module 800, and the 3D model creation unit 802 may create a 3D model of the plating module 400 based on the input information. Some of the information, for example, some physical property values, may be pre-stored in a storage device of the control module 800, and the operator may select appropriate values ​​from among them.

[0044] The state estimation unit 806 is configured to use a state equation to estimate the "state" of the plating module 400. Specifically, the state estimation unit 806 estimates the current density of the plating current at the outer edge of the substrate Wf as the "state" of the plating module 400.

[0045] Fig. 7 shows a plan view of the substrate Wf. The outer edge 62 of the substrate Wf is the portion where the substrate Wf is held by the substrate holder 440 and is not exposed to the plating solution. As shown in Fig. 7, the substrate Wf has one or more electrical contacts 441 on the outer edge 62. In the example of Fig. 7, the substrate Wf has six electrical contacts 441 spaced equally apart on the outer edge 62. The electrical contacts 441 are connected to the negative terminal of a power source (not shown) via electrical wiring (not shown) built into the substrate holder 440, and a plating current flows through the electrical contacts 441 to the substrate Wf.

[0046] Hereinafter, the current density of the plating current at the outer edge 62 of the substrate Wf will be referred to as the "outer edge current density," and the outer edge current density at time t will be referred to as j ｔ (θ), where θ indicates the position within the outer edge 62 of the substrate Wf measured as an angle around the center of the substrate Wf (see FIG. 7). Here, the outer edge current density j ｔ (θ) is expressed as a Fourier series as follows:

[0047]

[0048] Outer edge current density j ｔ (θ) is estimated using the Fourier coefficients a ｉ，ｔ and b ｉ，ｔ In one embodiment, the state estimation unit 806 estimates the outer edge current density j at time t−1 using the following state equation: ｔ－１ (θ) to the outer edge current density j at time t ｔ Estimate (predict) (θ).

[0049]

[0050] Here, the matrix F is given by the following equation and represents the rotation of the substrate Wf using the rotation mechanism 448. ｔ is noise. This model assumes that the outer edge current density at time t is given by the outer edge current density at time t-1 rotated in accordance with the rotation of the substrate Wf. In the following equation, ω is the angular velocity of the rotation of the substrate Wf, and Δt is the time step (i.e., the time difference between time t and time t-1).

[0051]

[0052] It should be noted that a state equation different from the above equation may be used to estimate the outer edge current density.

[0053] The observation value calculation unit 808 is configured to estimate an "observation value" from the "state" of the plating module 400 using an observation equation. Specifically, the observation value calculation unit 808 calculates, as the "observation value" of the plating module 400, the potential of the plating solution in the plating tank that is expected to be measured by the potential sensor 470, as the outer edge current density jｔ Hereinafter, the value calculated by the observation value calculation unit 808 is referred to as the "estimated potential value," and the estimated potential value at time t is referred to as φ ｔ It is written as follows.

[0054] As described above, the potential measured by the potential sensor 470 is the potential in the vicinity of the plating surface Wf-a of the substrate Wf undergoing plating processing. This potential is determined by the distribution of the plating current flowing from the plating solution in the plating tank to the substrate Wf. This plating current distribution depends on the physical structure of the plating module 400. Therefore, the estimated potential value φ ｔ can be calculated using the 3D model of the plating module 400 created in the 3D model creation unit 802. That is, the estimated potential value φ ｔ can be expressed as follows:

[0055]

[0056] where F is a function representing the 3D model of the plating module 400, and a ｉ，ｔ , b ｉ，ｔ etc. are the above-mentioned outer edge current density j ｔ The function F can be numerically determined based on the 3D model obtained from the 3D model creation unit 802. The function F in the above formula can be further defined as follows: ｉ，ｔ = 0 and b ｉ，ｔ = 0. Note that the following equation is an approximation up to the first order terms, but second order or higher terms may also be taken into consideration.

[0057]

[0058] In one embodiment, the observation value calculation unit 808 calculates the outer edge current density j at time t using the following observation equation: ｔ (θ) to obtain the estimated potential value φ at time t ｔ Calculate the value. ｔ is noise.

[0059]

[0060] This observation equation is based on the Taylor expansion equation of the function F that represents the 3D model of the plating module 400 shown above. ｔ A different observation equation may be used to obtain .times. ...

[0061] The Kalman filter 810 is configured to correct the "state" of the plating module 400 estimated by the state estimation unit 806 using actual measurement results in the plating module 400. Specifically, the Kalman filter 810 uses the actual potential measurement value obtained from the potential sensor 470 for the correction. In one embodiment, the Kalman filter 810 uses the potential measurement value obtained from the potential sensor 470 and the potential estimate value φ calculated by the observation value calculation unit 808. ｔ The outer edge current density j estimated by the state estimation unit 806 is calculated based on the difference between ｔ (θ) (i.e., the Fourier coefficient a ｉ，ｔ and b ｉ，ｔ ) is corrected.

[0062] As described above, since the substrate Wf is rotated by the rotation mechanism 448, potential measurements at a large number of measurement points along the circumferential direction of the substrate Wf can be obtained from the potential sensor 470. Therefore, correction is made using the measurements at these multiple measurement points, making it possible to obtain an accurate outer edge current density.

[0063] In this way, the outer edge current density j is estimated and corrected using the state space model 804. ｔ(θ) is output to the current density calculation unit 812. The current density calculation unit 812 calculates the current density of the plating current in a region 64 (see FIG. 7) inside the outer edge 62 of the substrate Wf based on the outer edge current density obtained from the state space model 804. Unlike the outer edge 62 of the substrate Wf, the region 64 is not held by the substrate holder 440 and is exposed to the plating solution. A current flows into the region 64 from the plating solution in the plating tank. That is, the current density calculation unit 812 calculates the current density of the current flowing from the plating solution in the plating tank to the substrate Wf via the interface between the plating solution and the substrate Wf. The film thickness of the plating formed on the substrate Wf depends on this current density. Hereinafter, this current density will be simply referred to as the "plating current density," and the plating current density at position k and time t on the substrate Wf (region 64) will be referred to as j. ｋ，ｔ It is written as follows.

[0064] Plating current density j ｋ，ｔ is the outer edge current density j ｔ (θ) in a specific relationship. Specifically, the plating current density is determined by the edge current density and the physical structure of the plating module 400. Therefore, the plating current density j ｋ，ｔ is the estimated potential value φ ｔ Similarly, it can be expressed as follows using a 3D model of the plating module 400:

[0065]

[0066] Here, G ｋ is a function representing the 3D model of the plating module 400, and a ｉ，ｔ , b ｉ，ｔ etc. is the outer edge current density j ｔ (θ) are the Fourier coefficients of the function G ｋ can be numerically determined based on the 3D model of the plating module 400 obtained from the 3D model creation unit 802. ｋ Further, as follows, a ｉ，ｔ = 0 and b ｉ，ｔ = 0. Note that the following equation is an approximation up to the first order terms, but second order or higher terms may also be taken into consideration.

[0067]

[0068] In one embodiment, the current density calculation unit 812 calculates the plating current density j using the above formula. ｋ，ｔ can be calculated.

[0069] The film thickness calculation unit 814 calculates the plating current density j obtained from the current density calculation unit 812. ｋ，ｔ In one embodiment, the film thickness calculation unit 814 is configured to calculate the film thickness of the plating formed on the substrate Wf based on the following equation: ｋ，ｔ and film thickness w ｋ，ｔ Calculate.

[0070]

[0071] where M and ρ are the molecular weight and density of the plating deposited on the substrate Wf, z is the valence of the plating reaction, and F is the Faraday constant. The film thickness calculation unit 814 predicts the future plating current density and film formation rate using the state equation described above, thereby calculating the current film thickness w ｋ，ｔ Instead, the film thickness w at the end of the plating process (time t = T) ｋ，Ｔ may be calculated.

[0072] The end point determination unit 816 determines the end point of the plating process on the substrate Wf based on the plating film thickness obtained by the film thickness calculation unit 814. For example, the end point determination unit 816 determines the end point of the plating process on the substrate Wf based on the estimated current film thickness w ｋ，ｔ The plating process may be terminated when the desired thickness is reached, or the estimated current film thickness w ｋ，ｔ and the predicted future deposition rate v ｋ，ｓ Based on (s=t, . . . , T), the time to the end point of the plating process may be predicted.

[0073] As described above, according to the plating apparatus 1000 of this embodiment, by using a state space model, it is possible to estimate the thickness of the plating film based on the measurement value of the potential sensor 470. This makes it possible to grasp in real time the change in the thickness of the plating film formed on the plating surface Wf-a of the substrate Wf during the plating process.

[0074] Second Embodiment FIG. 8 is a block diagram showing the functional configuration of a control module 801 according to another embodiment. The control module 801 of this embodiment is configured to calculate a deviation of the thickness distribution of a plating film formed on a substrate Wf from a reference state based on the deviation of the potential distribution measured by the potential sensor 470 from a predetermined reference state. For example, if plating is performed on the substrate Wf under non-ideal conditions, such as a power supply failure between some of the electrical contacts 441 (see FIG. 7 ) provided on the substrate Wf and the substrate holder 440, the signal representing the potential distribution near the substrate obtained from the potential sensor 470 may show irregularities (concave and / or convex portions) due to the power supply failure or the like. On the other hand, if the substrate Wf to be plated has a micro-machined pattern on its plating surface Wf-a, the potential distribution signal from the potential sensor 470 may show irregularities corresponding to the micro-machined pattern, even if plating is performed under ideal conditions. Therefore, as described in detail below, the control module 801 of this embodiment can calculate the deviation of the film thickness distribution actually formed on the substrate Wf from the film thickness distribution obtained when plating is performed under ideal conditions by using the difference between the potential distribution obtained from the potential sensor 470 and the potential distribution under ideal conditions (reference conditions).

[0075] The plating apparatus 1000 may be provided with a control module 801 according to this embodiment in place of or in addition to the control module 800 of the first embodiment (FIG. 6) described above.

[0076] 8 , the control module 801 includes a 3D model creation unit 802, a state space model 804, a current density calculation unit 812, a film thickness calculation unit 814, a database 818, a potential deviation calculation unit 820, and a plating process control unit 822. The state space model 804 includes a state estimation unit 806, an observation value calculation unit 808, and a Kalman filter 810. The 3D model creation unit 802, the state space model 804, the state estimation unit 806, the observation value calculation unit 808, the Kalman filter 810, the current density calculation unit 812, and the film thickness calculation unit 814 in the control module 801 are the same as the corresponding units in the control module 800 of the first embodiment described above. Like the control module 800, the control module 801 can be configured as a computer including an input / output device, an arithmetic unit, a storage device, etc. For example, the control module 801 is configured to realize the functions of each of the units 802, 806, 808, 810, 812, 814, 820, and 822 by having an arithmetic unit (e.g., a processor) read and execute a computer program stored in a storage device.

[0077] The database 818 stores reference data of the potential distribution near the substrate Wf. The reference data is data representing the potential distribution near the substrate Wf in a predetermined reference state. In this specification, the term "predetermined reference state" refers to a state in which plating can be ideally performed on the substrate Wf. For example, the predetermined reference state may be a state in which there is no power supply failure between the electrical contacts 441 on the substrate Wf and the substrate holder 440, or more generally, a state in which each component of the plating module 400 is appropriately configured so that a plating film can be formed on the substrate Wf with a certain degree of flatness. The reference data of the potential distribution near the substrate in such a reference state can be obtained in advance by performing plating on the substrate Wf in the reference state and measuring the potential near the substrate Wf using the potential sensor 470 during plating, and the data can be stored in the database 818.

[0078] The potential distribution of the reference data may be, for example, the distribution of potential near the substrate Wf along the circumferential direction of the substrate Wf. As described above, by performing a plating process while rotating the substrate Wf by the rotation mechanism 448, the potential sensor 470 can obtain measured potential values ​​at multiple points along the circumferential direction of the substrate Wf (or across the entire circumferential direction). A series of potential measurements in the reference state obtained in this manner can be stored in the database 818 as reference data representing the potential distribution along the circumferential direction of the substrate Wf. Furthermore, the potential distribution near the substrate Wf depends on factors such as the magnitude of the plating current and the micro-machined pattern formed or present on the plating surface Wf-a of the substrate Wf. Therefore, reference data for each of these various conditions may be stored in the database 818.

[0079] The potential deviation calculation unit 820 is configured to calculate the deviation of the potential distribution measured by the potential sensor 470 from reference data. FIG. 9 is a diagram conceptually illustrating the processing by the potential deviation calculation unit 820. In each graph in FIG. 9, the horizontal axis represents the circumferential position (angle) of the substrate Wf (see FIG. 7), and the vertical axis represents the potential. Graph 901 in FIG. 9 shows an example of the potential distribution measured by the potential sensor 470. This potential distribution includes a peak 904 caused by a power supply failure between the electrical contact 441 on the substrate Wf and the substrate holder 440, and peaks 905 and 906 caused by the micro-machined pattern on the plating surface Wf-a of the substrate Wf. Graph 902 in FIG. 9 shows an example of reference data. As described above, the reference data is a potential distribution in a reference state, and therefore the potential distribution in graph 902 includes peaks 905 and 906 corresponding to the micro-machined pattern, but does not include a peak corresponding to the power supply failure. 9 shows the deviation of the potential distribution calculated by the potential deviation calculation unit 820, and is obtained by subtracting the potential distribution (reference data) of the graph 902 from the potential distribution of the graph 901 (the potential distribution measured by the potential sensor 470). As a result of the subtraction, the graph 903 has only a peak 904 corresponding to a power supply failure.

[0080] Before subtracting the potential distribution of graph 902 from the potential distribution of graph 901, the reference data may be offset so that the average levels of the two are the same. Furthermore, the database 818 may store a plurality of reference data corresponding to a plurality of plating current values ​​and a plurality of micromachining patterns, as shown in FIG. 10 , for example. The potential deviation calculation unit 820 may select from the database 818 the reference data corresponding to the plating process currently being performed and use the selected reference data to calculate the deviation of the potential distribution. Furthermore, the potential deviation calculation unit 820 may generate reference data corresponding to the current plating current by interpolating the reference data stored in the database 818 and use the selected reference data to calculate the deviation of the potential distribution. For example, as shown in FIG. 11 , the potential deviation calculation unit 820 may use the reference data corresponding to a plating current of 3 amperes and the reference data corresponding to a plating current of 5 amperes to generate reference data corresponding to a plating current of 4 amperes, which is not stored in the database 818, by interpolation.

[0081] As described above, the control module 801 according to this embodiment uses the potential deviation calculation unit 820 to calculate the deviation of the potential distribution (i.e., graph 903 in FIG. 9 ) caused by plating being performed under non-ideal conditions (e.g., a state of poor power supply). The deviation of the potential distribution calculated by the potential deviation calculation unit 820 is input to the state space model 804. The state space model 804, the current density calculation unit 812, and the film thickness calculation unit 814 in the control module 801 according to this embodiment are configured in the same manner as the corresponding units in the control module 800 according to the first embodiment. Therefore, the film thickness calculation unit 814 outputs a film thickness (distribution) corresponding to the deviation of the potential distribution calculated by the potential deviation calculation unit 820, i.e., a deviation (distribution) of the film thickness formed on the substrate Wf currently undergoing plating processing from the film thickness formed on the substrate Wf under the reference conditions. In other words, the film thickness calculation unit 814 in the control module 801 according to this embodiment can calculate the deviation (distribution) of the film thickness formed on the substrate Wf caused by plating being performed under non-ideal conditions (e.g., a state of poor power supply). This makes it possible to grasp the thickness of the plating formed on the substrate Wf with high accuracy, and also makes it possible to easily determine whether the plating process is being performed under ideal conditions in the plating apparatus 1000.

[0082] The plating process control unit 822 is configured to perform control in accordance with the deviation in plating film thickness calculated by the film thickness calculation unit 814. For example, if the deviation in film thickness calculated by the film thickness calculation unit 814 is greater than a predetermined threshold, the plating process control unit 822 may issue an alarm to the operator of the plating apparatus 1000 using voice, text, images, sound, light, or the like. The plating process control unit 822 may also control the rotation mechanism 448 to change or adjust the direction and speed of rotation of the substrate holder 440 in accordance with the magnitude of the deviation in film thickness calculated by the film thickness calculation unit 814. The plating process control unit 822 may also control the position of the shield 480 to switch between the shielding position and the retracted position, or control whether or not to agitate the plating solution with a paddle or the agitation strength in accordance with the distribution of the deviation in film thickness calculated by the film thickness calculation unit 814. These controls can improve the flatness of the plating film formed on the substrate Wf.

[0083] Although the embodiments of the present invention have been described above based on several examples, the above-described embodiments of the invention are intended to facilitate understanding of the present invention and are not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit thereof, and the present invention naturally includes equivalents thereof. Furthermore, any combination or omission of the components described in the claims and specification is possible within the scope of solving at least part of the above-described problems or achieving at least part of the effects.

[0084] 1000 Plating apparatus 100 Load port 110 Transfer robot 120 Aligner 200 Pre-wet module 300 Pre-soak module 400 Plating module 500 Cleaning module 600 Spin rinse dryer 700 Transfer device 800 Control module 412 Inner tank 420 Membrane 422 Cathode region 424 Anode region 426 Anode mask 430 Anode 440 Substrate holder 441 Electrical contact 442 Lifting mechanism 448 Rotation mechanism 450 Resistor 452 Drive mechanism 468 Sensor support 470 Potential sensor 480 Shield 801 Control module 802 3D model creation unit 804 State space model 806 State estimation unit 808 Observation value calculation unit 810 Kalman filter 812 Current density calculation unit 814 Film thickness calculation unit 816 End point determination unit 818 Database 820 Potential deviation calculation unit 822 Plating process control unit 62 Outer edge portion

Claims

1. A plating apparatus comprising: a plating tank for containing a plating solution; a substrate holder for holding a substrate; an anode arranged in the plating tank so as to face the substrate held in the substrate holder; a potential sensor arranged near the substrate held in the substrate holder and configured to measure the potential of the plating solution; a database storing reference data of the potential distribution in the vicinity of the substrate, the reference data representing the potential distribution in the vicinity of the substrate in a predetermined reference state; a potential deviation calculation unit configured to calculate a deviation of the potential distribution measured by the potential sensor from the reference data; and a film thickness calculation unit configured to calculate a deviation of the plating film thickness formed on the substrate from the plating film thickness in the reference state based on the calculated deviation of the potential distribution.

2. The plating apparatus according to claim 1, wherein the reference data includes a plurality of reference data corresponding to different plating current values, and the potential deviation calculation unit is configured to calculate the deviation of the potential distribution using data interpolated from the plurality of reference data.

3. The plating apparatus according to claim 2, wherein the interpolated data corresponds to a plating current value when the potential is measured by the potential sensor.

4. The plating apparatus of claim 1, wherein the reference data includes a plurality of reference data corresponding to a micro-machined pattern on the substrate, and the potential deviation calculation unit is configured to calculate the deviation of the potential distribution using reference data from the plurality of reference data corresponding to the micro-machined pattern on the substrate during plating processing that is the target of potential measurement by the potential sensor.

5. A plating apparatus according to any one of claims 1 to 4, wherein the predetermined reference state is at least a state in which there is no power supply failure between the substrate and the substrate holder.

6. A plating apparatus according to any one of claims 1 to 4, wherein the predetermined reference state corresponds to a state in which a plating film is formed with a flatness higher than a predetermined threshold value.

7. A plating apparatus according to any one of claims 1 to 4, further comprising a plating process control unit configured to perform control in accordance with the deviation in the plating film thickness calculated by the film thickness calculation unit.

8. The plating apparatus of claim 7, wherein the control includes at least one of: (i) issuing an alarm; (ii) controlling the rotation of the substrate holder; (iii) controlling the position of a shield to partially shield the plating current in the plating solution; and (iv) controlling the agitation of the plating solution.

9. The plating apparatus according to any one of claims 1 to 4, further comprising: a state space model configured to estimate the current density flowing through the outer edge of the substrate using a state equation and an observation equation, wherein the state equation is an equation that describes the time evolution of the current density flowing through the outer edge of the substrate, and the observation equation is an equation that describes the relationship between the current density flowing through the outer edge of the substrate and the potential of the plating solution at the position of the potential sensor; and a current density calculation unit configured to calculate the plating current density in a region inside the outer edge of the substrate based on the current density estimated by the state space model, wherein the output from the potential deviation calculation unit is input to the state space model, and the output from the current density calculation unit is input to the film thickness calculation unit.

10. The plating apparatus according to claim 9, comprising a plating module including at least the plating tank, the substrate holder, the anode, and the potential sensor, wherein the relationship between the current density and the potential of the plating solution is based on a function representing a 3D model of the plating module.

11. The plating apparatus of claim 9, wherein the state space model further comprises a Kalman filter configured to correct the estimated result of the current density flowing through the outer edge of the substrate based on the measurement value of the potential sensor.

12. The plating apparatus according to claim 9, wherein the outer edge of the substrate is the portion of the substrate that is gripped by the substrate holder.

Images