JP2022146515A - Film thickness estimation method, film thickness estimation device, and etching method - Google Patents

Abstract

To determine a film thickness of an uppermost layer of a substrate having a multilayer structure in real time at low cost.SOLUTION: A refractive index and an extinction coefficient of each layer constituting a multilayer structure at the wavelength λ, and a film thickness of each layer of the multilayer structure excluding the uppermost layer are stored in advance. When the film thickness of the uppermost layer of the processed substrate is obtained, the substrate is irradiated with observation light having a wavelength λ, and an image of the uppermost layer of the substrate is acquired by an imaging unit. Then, the film thickness of the uppermost layer is estimated from the luminance values of the pixels forming the image of the uppermost layer on the basis of a pre-stored refractive index, extinction coefficient, and film thickness, and the inverse function of the function (R(λ)=f(d1)) showing the relationship between the reflectance R(λ) of the substrate at the wavelength λ and the film thickness d1 of the uppermost layer.SELECTED DRAWING: Figure 4

Description

The present invention provides a film thickness estimation technique for estimating the film thickness of the uppermost layer of a substrate having a multilayer structure in which at least one or more thin films are laminated on a base material layer, and the The present invention relates to an etching method using a film thickness estimation technique. Examples of substrates include semiconductor wafers, glass substrates for liquid crystal displays, glass substrates for plasma displays, optical disk substrates, magnetic disk substrates, magneto-optical disk substrates, photomask glass substrates, solar cell substrates, and the like. (hereinafter simply referred to as “substrate”).

Techniques for measuring the film thickness of the uppermost layer formed on a substrate such as a semiconductor wafer include a stylus-type surface profile measurement method, a method using terahertz waves (see Patent Document 1), a spectroscopic ellipsometer, and an interferometric film thickness meter. is known (see Patent Document 2).

Patent No. 6589239 JP-A-2001-41713

If such a conventional film thickness measurement technique is applied to a substrate processing apparatus for processing a substrate, such as an etching apparatus, the following problems arise. The stylus-type surface profile measurement adds disadvantages such as contamination and damage to the substrate. Further, in the method using the terahertz wave, it is necessary to incorporate an expensive film thickness measuring device into the etching device, which causes an increase in the cost of the etching device. Furthermore, when a spectroscopic ellipsometer or an interferometric film thickness meter is used as a film thickness measuring device, it is necessary to equip it with spectroscopic optical components such as an acoustooptic spectral filter. As a result, the apparatus becomes expensive, and the wavelength of the observation light must be scanned within a certain band, making it difficult to measure the film thickness in real time.

The present invention has been made in view of the above problems, and provides a film thickness estimation technique capable of finding the film thickness of the uppermost layer of a substrate having a multilayer structure in real time at low cost, and an etching method using the film thickness estimation technique. intended to provide

A first aspect of the present invention is a film thickness estimation for estimating the film thickness of the uppermost layer of a substrate having a multilayer structure in which at least one or more thin films are laminated on a substrate layer after being processed. A method comprising the steps of: (a) irradiating a processed substrate with observation light of wavelength λ to acquire an image of the top layer of the substrate with an imaging unit; and (b) constructing a multilayer structure at wavelength λ. (c) storing the refractive index and extinction coefficient of each layer and the film thickness of each layer except for the uppermost layer in the multilayer structure; Constructing an image of the top layer based on the inverse function of the function (R(λ)=f(d1)) representing the relationship between the reflectance R(λ) of the substrate at λ and the film thickness d1 of the top layer and estimating the film thickness of the top layer from the luminance value of the pixel.

A second aspect of the present invention is film thickness estimation for estimating the film thickness of the uppermost layer of a substrate having a multilayer structure in which at least one or more thin films are laminated on a substrate layer after being processed. An apparatus comprising an illuminating unit that irradiates a processed substrate with observation light having a wavelength of λ, an imaging unit that captures an image of the substrate irradiated with the observation light to acquire an image of the top layer of the substrate, and a wavelength of λ. A storage unit for storing the refractive index and extinction coefficient of each layer constituting the multilayer structure in and the film thickness of each layer except for the uppermost layer in the multilayer structure, and the refractive index, extinction coefficient and film thickness stored in the storage unit , and the inverse function of the function (R(λ)=f(d1)) showing the relationship between the reflectance R(λ) of the substrate and the film thickness d1 of the top layer. and a film thickness estimating unit for estimating the film thickness of the uppermost layer from the luminance value of .

A third aspect of the present invention is an etching method for etching the uppermost layer of a substrate by supplying a processing liquid to a substrate having a multilayer structure in which at least one or more thin films are laminated on a base material layer, The method is characterized in that the film thickness of the uppermost layer of the substrate being processed with the processing liquid is obtained using the above film thickness estimation method, and the supply of the processing liquid is controlled according to the estimated value.

In the invention configured as described above, the refractive index and extinction coefficient of each layer constituting the multilayer structure at the wavelength λ, and the film thickness of each layer of the multilayer structure excluding the uppermost layer are stored in advance. When estimating the film thickness of the top layer of the processed substrate, the substrate is irradiated with observation light having a wavelength λ, and an image of the top layer of the substrate is acquired by the imaging unit. Then, a function (R(λ)=f(d1)) representing the relationship between the refractive index, the extinction coefficient, and the film thickness stored in advance, and the reflectance R(λ) of the substrate at the wavelength λ and the film thickness d1 of the uppermost layer ), the film thickness of the top layer is obtained from the luminance values of the pixels forming the image of the top layer.

According to the invention configured in this manner, the film thickness of the top layer can be obtained from the image of the top layer of the substrate obtained by imaging the substrate illuminated with the observation light of the specific wavelength λ. As described above, it is possible to estimate the film thickness of the uppermost layer using observation light of a specific wavelength λ without requiring wavelength scanning of the observation light as in the prior art. As a result, the film thickness of the uppermost layer of a substrate having a multilayer structure can be determined in real time at low cost.

1 is a diagram showing an example of a substrate processing apparatus equipped with a film thickness estimating mechanism, which is an embodiment of a film thickness estimating apparatus according to the present invention; FIG. 2 is a top plan view of the substrate processing apparatus shown in FIG. 1; FIG. FIG. 3 is a diagram showing the configuration of a film thickness estimation mechanism provided in the substrate processing apparatus shown in FIGS. 1 and 2; FIG. FIG. 3 is a flowchart showing an example of bevel etching operation by the substrate processing apparatus shown in FIGS. 1 and 2; FIG. 4 is a flow chart showing an example of a calibration value acquisition operation performed before bell etching processing. 5 is a flow chart showing an operation of estimating the film thickness of the uppermost layer; It is a figure for demonstrating the film-thickness estimation operation|movement of a top layer. It is a figure for demonstrating the film-thickness estimation operation|movement of a top layer. 5 is a flow chart showing a process of determining a film thickness candidate value;

FIG. 1 is a diagram showing an example of a substrate processing apparatus equipped with a film thickness estimating mechanism, which is an embodiment of a film thickness estimating apparatus according to the present invention. 2 is a top plan view of the substrate processing apparatus shown in FIG. 1. FIG. FIG. 3 is a diagram showing the configuration of a film thickness estimation mechanism provided in the substrate processing apparatus shown in FIGS. 1 and 2. In FIG. In the drawings referred to below, the dimensions and numbers of each part may be exaggerated or simplified for easy understanding. The up-down direction is the vertical direction, and the substrate side is up with respect to the spin chuck.

The substrate processing apparatus 1 includes a rotation holding mechanism 2, a scattering prevention unit 3, a surface protection unit 4, a processing unit 5, a nozzle moving mechanism 6, a heating mechanism 7, and a film corresponding to an embodiment of the film thickness estimation apparatus according to the present invention. A thickness estimation mechanism 8 and a control unit 10 are provided. These units 2 to 8 are electrically connected to the control unit 10 and operate according to instructions from the control unit 10 . As the control unit 10, for example, a device similar to a general computer can be adopted. That is, the control unit 10 stores, for example, a CPU that performs various arithmetic processing, a ROM that is a read-only memory that stores basic programs, a RAM that is a readable and writable memory that stores various information, control software, data, and the like. It has a magnetic disk, etc. In the control unit 10, each unit of the substrate processing apparatus 1 is controlled by the CPU as the main control unit performing arithmetic processing according to the procedure described in the program.

This substrate processing apparatus 1 performs an etching process on the peripheral portion of a substrate W having a q-layer structure in which at least one or more thin films are laminated on a substrate layer Lq as shown in FIG. Etching equipment. In the substrate processing apparatus 1, the film thickness estimating mechanism 8 obtains the film thickness d1 of the uppermost layer L1 of the peripheral portion of the substrate W at a predetermined sampling period. During the etching process, the control unit 10 detects the time when the film thickness d1 obtained by the film thickness estimating mechanism 8 becomes zero as an endpoint, and stops the etching process at the detection time. The film thickness sampling and bevel etching operation in the substrate processing apparatus 1 will be described in detail later.

The rotation holding mechanism 2 is a mechanism capable of rotating the substrate W while holding the substrate W in a substantially horizontal position with its surface facing upward. The rotation holding mechanism 2 rotates the substrate W around a vertical rotation axis a1 passing through the center c1 of the main surface. The rotation holding mechanism 2 includes a spin chuck (“substrate holder”) 21 that is a disk-shaped member smaller than the substrate W. As shown in FIG. The spin chuck 21 is provided such that its upper surface is substantially horizontal and its central axis coincides with the rotation axis a1. A cylindrical rotating shaft portion 22 is connected to the lower surface of the spin chuck 21 . The rotating shaft portion 22 extends vertically with its axis aligned with the rotating shaft a1. Further, a rotation driving section (for example, a motor) 23 is connected to the rotating shaft section 22 . The rotary drive unit 23 rotates the rotary shaft unit 22 around its axis in response to a rotation command from the control unit 10 . Therefore, the spin chuck 21 is rotatable around the rotation axis a1 together with the rotation shaft portion 22. As shown in FIG. The rotation drive section 23 and the rotation shaft section 22 constitute a rotation mechanism 231 that rotates the spin chuck 21 about the rotation axis a1. The rotary shaft portion 22 and the rotary drive portion 23 are housed in a tubular casing 24 .

A through hole (not shown) is provided in the central portion of the spin chuck 21 and communicates with the internal space of the rotating shaft portion 22 . A pump (not shown) is connected to the internal space via a pipe (not shown) and an on-off valve (not shown). The pump and on-off valve are electrically connected to the controller 10 . The control unit 10 controls the operations of the pump and the on-off valve. The pump can selectively supply negative pressure and positive pressure under the control of the control unit 10 . When the pump supplies a negative pressure while the substrate W is placed on the upper surface of the spin chuck 21 in a substantially horizontal posture, the spin chuck 21 sucks and holds the substrate W from below. The substrate W can be removed from the upper surface of the spin chuck 21 when the pump provides positive pressure.

In this configuration, when the spin chuck 21 sucks and holds the substrate W, when the rotation drive unit 23 rotates the rotation shaft unit 22, the spin chuck 21 rotates around the axis along the vertical direction. As a result, the substrate W held on the spin chuck 21 is rotated in the direction of the arrow AR1 about the vertical rotation axis a1 passing through the in-plane center c1.

The method of holding the substrate W is not limited to this, and may be a so-called mechanical chuck method in which a plurality of (for example, six) chuck pins are used to hold the substrate W.

The scattering prevention unit 3 receives the processing liquid and the like that scatter from the substrate W that is rotated together with the spin chuck 21 . The anti-scattering part 3 has a splash guard 31 . The splash guard 31 is a cylindrical member with an open upper end, and is provided so as to surround the rotation holding mechanism 2 . The splash guard 31 is connected to a guard driving mechanism (not shown) for moving the splash guard 31 up and down, and is driven according to a lifting command from the control unit 10 .

The surface protection unit 4 is a gas ejection mechanism that ejects a flow of inert gas so as to hit the peripheral edge of the upper surface of the substrate W held on the spin chuck 21 and rotating (symbol Wu in FIG. 4 later). It has The "inert gas" is a gas having poor reactivity with the material of the substrate W and the thin film formed on its surface, such as nitrogen (N2) gas, argon gas, and helium gas. In this embodiment, gas ejection mechanisms 41 and 42 are provided. The gas ejection mechanisms 41 and 42 eject an inert gas, for example, as a gas columnar gas flow. The gas discharge mechanism 42 discharges a gas flow of an inert gas so that the gas flow discharged by the gas discharge mechanism 41 hits a position on the upstream side of the substrate W in the rotational direction from the position where the gas flow hits the peripheral portion of the substrate W.

The surface protection unit 4 further includes a gas ejection mechanism 43 that ejects an inert gas flow toward the vicinity of the center of the upper surface of the substrate W held on the spin chuck 21 and rotating. The surface protection portion 4 is ejected so as to hit an annular processing area defined by the peripheral edge of the upper surface of the substrate W by ejecting a flow of inert gas from the gas ejection mechanisms 41 to 43 onto the upper surface of the substrate W. The non-processing region on the upper surface of the substrate W is protected from the processing liquid and the like.

The gas ejection mechanisms 41 and 42 each have a nozzle head 44 . The gas ejection mechanism 43 has a nozzle head 45 . The nozzle heads 44 and 45 are attached to the tips of arms 61 and 62 of the nozzle moving mechanism 6, respectively, which will be described later. Arms 61, 62 extend along a horizontal plane. The nozzle moving mechanism 6 moves the arms 61 and 62 to move the nozzle heads 44 and 45 between the treatment position (solid line position in FIG. 2) and the retracted position (two-dot chain line position in FIG. 2). to move.

The nozzle head 44 has two nozzles 46 and 47 and is attached to the tip of the arm 61 . The nozzles 46 and 47 project downward from the lower surface of the nozzle head 44 at their tips (lower ends) and upward from the upper surface of the nozzle head 44 . One end of a pipe 411 is connected to the upper end of one nozzle 46 . The other end of the pipe 411 is connected to a gas supply source 412 . In addition, a flow controller 413 and an on-off valve 414 are provided in order from the gas supply source 412 side along the path of the pipe 411 . One end of the pipe 421 is also connected to the other nozzle 47 . The other end of the pipe 421 is connected to a gas supply source 422 . In addition, a flow controller 423 and an on-off valve 424 are provided in order from the gas supply source 422 side along the path of the pipe 421 .

Here, when the nozzle moving mechanism 6 arranges the nozzle head 44 at the processing position, the ejection port of the nozzle 46 faces a part of the rotational locus of the peripheral portion of the substrate W rotated by the rotation holding mechanism 2, and the nozzle The outlet of 47 faces another part of the rotation trajectory.

With the nozzle head 44 positioned at the processing position, the nozzles 46 and 47 are supplied with an inert gas (nitrogen (N2) gas in the illustrated example) from the gas supply sources 412 and 422 . The nozzle 46 discharges the supplied inert gas flow from above so that it hits the position defined by the rotational trajectory of the peripheral portion of the substrate W. As shown in FIG. The nozzle 46 discharges the gas flow from the discharge port in a predetermined direction so that the discharged gas flow reaches the position and flows toward the peripheral edge of the substrate W from the position. The nozzle 47 discharges a gas flow from above so that the supplied gas flow of inert gas hits a position defined on the rotation locus. The nozzle 47 ejects the gas flow from the ejection port in a predetermined direction so that the ejected gas flow reaches the position and then flows from the position toward the peripheral edge of the substrate W. FIG.

The nozzle head 45 of the gas discharge mechanism 43 includes a cylindrical member 93 attached to the lower surface of the tip of the arm 62 , a disk-shaped blocking plate 90 attached to the lower surface of the cylindrical member 93 , and a cylindrical nozzle 48 . It has The axis of the columnar member 93 and the axis of the shielding plate 90 are aligned and run vertically. The lower surface of the blocking plate 90 is along the horizontal plane. The nozzle 48 vertically penetrates the cylindrical member 93 and the blocking plate 90 so that the axis of the nozzle 48 coincides with the axis of the blocking plate 90 and the cylindrical member 93 . The upper end of the nozzle 48 also penetrates the tip of the arm 62 and opens to the upper surface of the arm 62 . One end of a pipe 431 is connected to the upper opening of the nozzle 48 . The other end of the pipe 431 is connected to a gas supply source 432 . A flow controller 433 and an on-off valve 434 are provided in order from the gas supply source 432 side along the path of the pipe 431 . A lower end of the nozzle 48 opens to the lower surface of the blocking plate 90 . The opening is the outlet of the nozzle 48 .

When the nozzle moving mechanism 6 places the nozzle head 45 at its processing position, the ejection openings of the nozzles 48 face the upper surface of the substrate W near the center thereof. In this state, the nozzle 48 is supplied with an inert gas (nitrogen (N2) gas in the illustrated example) from a gas supply source 432 via a pipe 431 . The nozzle 48 discharges the supplied inert gas toward the vicinity of the center of the upper surface of the substrate W as a gas flow of the inert gas. The gas flow spreads radially from above the central portion of the substrate W toward the periphery of the substrate W. As shown in FIG. That is, the gas ejection mechanism 43 ejects an inert gas from above the central portion of the upper surface of the substrate W to generate a gas flow that spreads from above the central portion toward the periphery of the substrate W. As shown in FIG.

The processing section 5 performs processing on a processing region in the peripheral edge portion of the upper surface of the substrate W held on the spin chuck 21 . Specifically, the processing section 5 supplies the processing liquid to the processing region of the substrate W held on the spin chuck 21 . The processing section 5 includes a processing liquid ejection mechanism 51A. The processing liquid discharge mechanism 51A discharges a liquid flow of the processing liquid so that it hits part of the periphery of the upper surface (processing surface) of the substrate W held on the spin chuck 21 and rotating. The liquid flow is columnar. The treatment liquid ejection mechanism 51A has a nozzle head 50 . The nozzle head 50 is attached to the tip of a long arm 63 provided in the nozzle moving mechanism 6 . Arm 63 extends along a horizontal plane. The nozzle moving mechanism 6 moves the nozzle head 50 between its processing position (the solid line position in FIG. 2) and the retracted position (the two-dot chain line position in FIG. 2) by moving the arm 63 .

The nozzle head 50 has four nozzles 5 a to 5 d and is attached to the tip of the arm 63 . The nozzles 5a to 5d are arranged in a row along the direction in which the arm 63 extends. In the nozzle head 50, the tips (lower ends) of the nozzles 5a to 5d protrude downward, and the base ends (upper ends) protrude upward. A processing liquid supply unit 51, which is a piping system for supplying the processing liquid to the nozzles 5a to 5d, is connected to the nozzles 5a to 5d. Specifically, one ends of pipes 53a to 53d of the processing liquid supply unit 51 are connected to the upper ends of the nozzles 5a to 5d. The nozzles 5a to 5d are supplied with the processing liquid from the processing liquid supply unit 51, respectively, and eject the supplied processing liquid from ejection openings at the tips thereof. The treatment liquid ejection mechanism 51A ejects a flow of treatment liquid from one of the nozzles 5a to 5d determined by control information set in the controller 10 under the control of the controller 10. FIG.

Specifically, the treatment liquid supply unit 51 includes an SC-1 supply source 52a, a DHF supply source 52b, an SC-2 supply source 52c, a rinse solution supply source 52d, a plurality of pipes 53a, 53b, 53c, 53d, and It is configured by combining a plurality of on-off valves 54a to 54d. SC-1, DHF and SC-2 are chemical solutions. Accordingly, the processing liquid ejection mechanism 51A is a chemical liquid ejection section that ejects the chemical liquid onto the peripheral portion of the substrate W. As shown in FIG.

SC-1 source 52a is a source that supplies SC-1. The SC-1 supply source 52a is connected to the nozzle 5a via a pipe 53a in which an on-off valve 54a is inserted. Therefore, when the on-off valve 54a is opened, SC-1 supplied from the SC-1 supply source 52a is discharged from the nozzle 5a.

The DHF supply source 52b is a supply source that supplies DHF. The DHF supply source 52b is connected to the nozzle 5b via a pipe 53b in which an on-off valve 54b is inserted. Therefore, when the on-off valve 54b is opened, DHF supplied from the DHF supply source 52b is discharged from the nozzle 5b.

SC-2 source 52c is a source that supplies SC-2. The SC-2 supply source 52c is connected to the nozzle 5c via a pipe 53c in which an on-off valve 54c is inserted. Therefore, when the on-off valve 54c is opened, SC-2 supplied from the SC-2 supply source 52c is discharged from the nozzle 5c.

The rinse liquid supply source 52d is a supply source that supplies the rinse liquid. Here, the rinse liquid supply source 52d supplies, for example, pure water or DIW (deionized water) as the rinse liquid. The rinse liquid supply source 52d is connected to the nozzle 56 via a pipe 53d in which an on-off valve 54d is inserted. Therefore, when the on-off valve 54d is opened, the rinse liquid supplied from the rinse liquid supply source 52d is discharged from the nozzle 56. As shown in FIG. Pure water, warm water, ozonated water, magnetic water, reduced water (hydrogen water), various organic solvents (ionized water, IPA (isopropyl alcohol), functional water (CO2 water, etc.), etc. are used as rinsing liquids. may

The treatment liquid supply unit 51 selectively supplies SC-1, DHF, SC-2, and a rinse liquid. When the processing liquid (SC-1, DHF, SC-2, or rinsing liquid) is supplied from the processing liquid supply unit 51 to the corresponding one of the nozzles 5a to 5d, the peripheral edge of the upper surface of the rotating substrate W The nozzle ejects a stream of the processing liquid so as to impinge on the processing area of . However, each of the on-off valves 54 a to 54 d provided in the processing liquid supply unit 51 is opened and closed under the control of the control unit 10 by a valve opening/closing mechanism (not shown) electrically connected to the control unit 10 . In other words, the ejection mode of the treatment liquid from the nozzles of the nozzle head 50 (specifically, the type of treatment liquid to be ejected, the ejection start timing, the ejection end timing, the ejection flow rate, etc.) is controlled by the control unit 10. . That is, under the control of the control unit 10, the processing liquid discharge mechanism 51A discharges a flow of processing liquid so as to hit a position in the rotation locus of the upper surface peripheral edge of the substrate W rotating about the rotation axis a1.

The nozzle moving mechanism 6 is a mechanism that independently moves the nozzle heads 44, 45, 50 between their respective processing positions and retracted positions. The nozzle moving mechanism 6 includes horizontally extending arms 61-63, nozzle bases 64-66, and drive units 67-69. Nozzle heads 44, 45 and 50 are attached to the tip portions of arms 61-63, respectively.

Base ends of the arms 61 to 63 are connected to upper end portions of nozzle bases 64 to 66, respectively. The nozzle bases 64 to 66 are distributed around the casing 24 in such a posture that their axes extend along the vertical direction. The nozzle bases 64 to 66 extend vertically along their axes and each have a rotation shaft rotatable around the axes. The axis of the nozzle bases 64 to 66 and the axis of each rotating shaft coincide. The upper ends of the nozzle bases 64 to 66 are attached to the upper ends of the respective rotating shafts. As each rotating shaft rotates, each upper end portion of each of the nozzle bases 64-66 rotates about the axis of each rotating shaft, that is, the axis of the nozzle bases 64-66. The nozzle bases 64 to 66 are provided with drive units 67 to 69 for rotating the respective rotating shafts around the axis. The drive units 67 to 69 are each configured with, for example, a stepping motor or the like.

The drive units 67-69 rotate the upper end portions of the nozzle bases 64-66 via the rotation shafts of the nozzle bases 64-66, respectively. As each upper end portion rotates, the nozzle heads 44, 45, 50 also rotate about the axes of the nozzle bases 64-66. As a result, the drive units 67 to 69 horizontally move the nozzle heads 44, 45, 50 between their respective processing positions and retracted positions.

When the nozzle head 44 is placed at the processing position, the ejection openings of the nozzles 46 face a part of the rotational trajectory of the peripheral portion of the substrate W rotated by the rotation holding mechanism 2, and the ejection openings of the nozzles 47 face the rotation locus. Oppose another part of the trajectory.

When the nozzle head 45 is placed at the processing position, the nozzle 48 is positioned above the center c1 of the substrate W, and the axis of the nozzle 48 coincides with the rotation axis a1 of the spin chuck 21. FIG. A discharge port (opening on the lower side) of the nozzle 48 faces the central portion of the substrate W. As shown in FIG. In addition, the lower surface of the blocking plate 90 faces the upper surface of the substrate W in parallel. The blocking plate 90 approaches the upper surface of the substrate W in a non-contact state.

When the nozzle head 50 is placed at the processing position, the nozzles 5a-5d are placed at the processing position. The retracted positions of the nozzle heads 44, 45 and 50 are positions at which they do not interfere with the transport path of the substrate W and do not interfere with each other. Each retracted position is, for example, a position outside and above the splash guard 31 .

A heating mechanism 7 is provided below the peripheral portion of the lower surface of the substrate W. As shown in FIG. The heating mechanism 7 includes an annular heater (not shown) extending in the circumferential direction of the substrate W along the peripheral portion of the lower surface of the substrate W, and an electric heater (not shown) that supplies power to the heater under the control of the control unit 10 . has a circuit. When power is supplied to the heater in a state in which the heater is arranged directly below the peripheral portion of the lower surface of the substrate W, the heater generates heat to heat the peripheral portion of the substrate W. As shown in FIG.

The film thickness estimation mechanism 8 has an imaging head 81 . As shown in FIG. 3, the imaging head 81 includes an illumination unit 82 for illuminating the substrate W with observation light L(λ) having a wavelength λ at a predetermined incident angle θ (for example, 30°); An imaging unit 83 is provided for receiving the reflected light RL reflected by W and imaging the uppermost layer L1 of the substrate W to obtain an image of the uppermost layer L1 (symbol IM in FIG. 7). In this embodiment, the imaging unit 83 is configured by a monochrome two-dimensional camera. This imaging head 81 is attached to the tip of an arm 84 as shown in FIG. Arm 84 extends along a horizontal plane. A base end portion of the arm 84 is connected to an upper end portion of the head base 85 . The head base 85 is arranged around the casing 24 in such a posture that its axis extends along the vertical direction. The head base 85 extends vertically along its axis and has a rotation shaft rotatable around the axis. The axis of the head base 85 coincides with the axis of the rotating shaft. An upper end portion of a head base 85 is attached to the upper end of each rotating shaft. As each rotating shaft rotates, the upper end portion of the head base 85 rotates about the axis of the rotating shaft, that is, the axis of the head base 85 . The head base 85 is provided with a driving section 86 that rotates each rotating shaft around the axis. The drive unit 86 is configured with, for example, a stepping motor.

The film thickness estimation mechanism 8 determines the film thickness d1 of the uppermost layer L1 of the substrate W by controlling the illumination unit 82, the imaging unit 83 and the driving unit 86 according to the film thickness estimation command from the control unit 10. It has a film thickness estimation controller 87 that outputs information about d1 to the controller 10 . Like the control unit 10, the film thickness estimation control unit 87 includes a CPU 871 that performs various arithmetic processing, and a storage unit 872 that stores a film thickness estimation program and various information. Then, the CPU 871 cooperates with the control unit 10 according to the film thickness estimation program to obtain related information necessary for estimating the film thickness before the bevel etching process, the calibration value, and the film thickness of the uppermost layer L1 immediately before the bevel etching process. The film thickness d1 of the uppermost layer L1 being processed is estimated. That is, the CPU 871 and the storage section 872 function as the "film thickness estimation section" and the "storage section" of the present invention, respectively. In this embodiment, the film thickness estimation control unit 87 is provided independently of the control unit 10, but the function of the film thickness estimation control unit 87 is incorporated into the control unit 10, and the CPU and the magnetic disk of the control unit 10 are They may function as the "film thickness estimation section" and the "storage section" of the present invention, respectively.

Next, a bevel etching operation by the substrate processing apparatus 1 configured as described above will be described with reference to FIGS. 4 to 9. FIG. FIG. 4 is a flow chart showing an example of bevel etching operation by the substrate processing apparatus shown in FIGS.

In the substrate processing apparatus 1, before executing the bevel etching process, related information of the substrate W to be processed which is the target of the bevel etching process is acquired and stored in the storage unit 872 (step S1). Here, the relevant information is the refractive index n(λ, 1), n(λ, 2), . . . , n(λ, q) and the extinction coefficient k(λ, 1), k(λ, 2), . The main purpose of acquiring such related information in advance and storing it in the storage unit 872 is closely related to the principle of film thickness estimation in this embodiment.

The film thickness estimation in the present embodiment is based on the reflectance measurement described in "Simulation of spectral characteristics of optical thin films", Keiji Kuriyama, Surface Technology Vol. 48, No. 9, 1997 (hereinafter referred to as "non-patent document"). Based on the calculation method. That is, in non-patent literature, the reflectance R(λ) of an arbitrary multilayer film at a certain wavelength λ is expressed by the number of layers q in the multilayer structure and the refractive index n(λ, 1), n(λ,2), . determined by the thicknesses d1, d2, . . . , dq and the incident angle .theta. At this time, if the relationship between the reflectance R(λ) and the film thickness d1 of the top layer L1 is defined as a function R(λ)=f(d1), then the film thickness d1 of the top layer L1 is acquired by the imaging unit 83. The inverse function of the above function, more specifically, the following formula d1=f ⁻¹ (I(λ)−Ioff)/A) (1 ) where A is the gain of the imaging unit 83,
Ioff is the luminance value offset;
can be obtained by Here, the luminance value offset Ioff corresponds to the luminance value of the pixels forming the image acquired by the imaging unit 83 in an environment in which illumination by the illumination unit 82 is not performed, that is, in a dark environment. Further, for a substrate W having a two-layer structure in which a silicon oxide film is formed on a silicon wafer, for example, the gain A can be obtained as follows. A bare silicon substrate is used as a reference sample (corresponding to the “calibration substrate” of the present invention), and while this is illuminated with observation light L(λ), the luminance value I(λ , Bare-Si) and the reflectance R (λ, Bare-Si) of the bare silicon substrate,
A=(I(λ, Bare-Si)−Ioff)/R(λ, Bare-Si) (2).

Therefore, in the present embodiment, it is determined in step S2 whether or not the calibration values have already been acquired. Here, if the calibration values of the substrate to be processed W to be subjected to the bevel etching process have already been obtained, the process proceeds to step S4 without executing the calibration value obtaining process (step S3). On the other hand, when the calibration value has not been obtained ("NO" in step S2), the process proceeds to step S4 after the calibration value obtaining process is executed.

FIG. 5 is a flow chart showing an example of a calibration value acquisition operation performed before the bell etching process. Here, in order to facilitate understanding of the calibration value acquisition operation, the substrate W to be processed will be described by exemplifying a two-layer structure substrate in which a silicon oxide film is laminated on a silicon wafer as described above. In the calibration value acquisition operation (step S3), the image capturing unit 83 captures an image while the illumination unit 82 is turned off. Accordingly, acquisition of an image in a dark environment is executed (step S31). Then, the CPU 871 of the film thickness estimation control section 87 calculates the average value of the luminance values of the pixels forming the image, and stores it in the storage section 872 as the luminance value offset Ioff (step S32).

Subsequently, a reference sample of the substrate W on which only the uppermost layer L1 is not formed is placed on the spin chuck 21 . Here, a substrate having no uppermost layer (SiO2) L1 among the two-layer structure substrates, that is, a bare silicon substrate is used as a reference sample. The reference sample may be placed by a transfer robot (not shown) accessed from the outside of the substrate processing apparatus 1, or may be manually operated by an operator. Then, when the reference sample is placed on the spin chuck 21 , the pump supplies negative pressure onto the spin chuck 21 . As a result, the reference sample is adsorbed and held on the spin chuck 21 . Thus, the loading of the reference sample is completed (step S33).

Next, the illumination unit 82 is turned on to irradiate the surface of the reference sample with the observation light L(λ) having the wavelength λ, and the imaging unit 83 receives the light reflected by the surface of the reference sample. An image (for example, symbol IM in the lower left drawing of FIG. 7 described later) is acquired (step S34). Then, the CPU 871 acquires the average value of the luminance values of the pixels forming the image of the reference sample as the luminance value I (λ, Bare-Si) (step S35). In parallel with this, the CPU 871 reads from the storage unit 872 the refractive index n(λ, 2) of silicon at the wavelength λ, the extinction coefficient k(λ, 2) at the wavelength λ, the number of layers of the reference sample=1, and the The thickness d2 of the two layers L2 (here, the thickness of the bare silicon substrate) is read. The CPU 871 also calculates the reflectance R(λ, Bare-Si) of the reference sample based on these values and the incident angle θ (for example, 30°) of the observation light L(λ) with respect to the reference sample ( Step S36) Then, these are substituted into the above equation (1), and the CPU 871 calculates the gain A (step S37).

After the brightness value offset Ioff and gain A obtained in this manner are stored in the storage unit 872 as calibration values, the suction holding by the spin chuck 21 is released. Then, the reference sample (bare silicon substrate) is unloaded from the spin chuck 21 by a transfer robot, an operator, or the like (step S38). This completes the calibration value acquisition process.

Returning to FIG. 4, the description continues. At the stage when the calibration values used for estimating the film thickness of the uppermost layer L1 are prepared, the spin chuck 21 is in an empty state, and the substrate W to be processed is loaded there by transport means such as a transport robot and placed thereon. placed. Then, the pump supplies a negative pressure onto the spin chuck 21 , whereby the reference sample is attracted and held on the spin chuck 21 . Thus, the loading of the reference sample is completed (step S4). Meanwhile, the transfer robot retreats from the substrate processing apparatus 1 .

The substrate W held by the spin chuck 21 is basically manufactured with a value designed in advance for each layer, and the film thickness of the uppermost layer L1 of the substrate W immediately after loading is the design value d1d or a value approximate thereto. It is highly possible that there is. However, the substrate processing apparatus 1 does not have information about the history of the substrate, such as the elapsed time from the formation of the uppermost layer L1 and the processing steps. Therefore, at this point, it is desirable to determine the film thickness d1 of the uppermost layer L1 by "estimating the film thickness of the uppermost layer", which is a feature of the present invention. Therefore, in the present embodiment, as will be described later, the film thickness of the top layer L1 immediately after loading is estimated in the same sequence as the film thickness estimation of the top layer L1 performed at regular time intervals (sampling period) during the bevel etching process. I am looking for d1. More specifically, the design value d1d is set as the film thickness of the uppermost layer L1 immediately before the film thickness estimation (hereinafter referred to as "immediate film thickness d1_pre") (step S5), and the CPU 871 uses this to determine the film thickness shown in FIG. An estimation process is executed to estimate the film thickness d1 of the uppermost layer L1 (step S6). Then, the film thickness d1 obtained in step S6 is set as the previous film thickness d1_pre immediately before the start of the bevel etching process (step S7).

FIG. 6 is a flow chart showing the operation of estimating the film thickness of the uppermost layer. 7 and 8 are diagrams for explaining the operation of estimating the film thickness of the uppermost layer. The substrate processing apparatus 1 is an apparatus for performing bevel etching processing, and the peripheral portion of the uppermost layer L1 is selectively etched away. Therefore, the portion where the film thickness d1 of the top layer L1 should be accurately obtained is also the peripheral portion and its periphery. Therefore, during the film thickness estimation operation of the uppermost layer L1, the imaging head 81 is arranged above the peripheral portion of the substrate W held by the spin chuck 21 as shown in FIG. After that, the illumination unit 82 is turned on to emit observation light L(λ) of wavelength λ. Observation light L(λ) is applied at an incident angle θ (FIG. 3) to the periphery and surroundings of the substrate W as shown in FIG. 7, thereby illuminating a portion of the top layer L1.

The imaging unit 83 receives light multiple-reflected by the uppermost layer L1 to the substrate layer Lq. As a result, for example, a two-dimensional image IM as shown in the lower left enlarged view of FIG. 7 is obtained (step S61). Note that the lower right enlarged view in the same figure shows an example of a two-dimensional image IM acquired during the bevel etching process, which will be described later. Further, in the figure, the hatched areas indicate the areas not subjected to the etching process, and the dotted areas indicate the areas subjected to the etching process. Furthermore, in the same figure, x-coordinates and y-coordinates are added to specify the pixels PX that form the two-dimensional image. That is, a two-dimensional image is composed of a group of pixels from pixel PX(0,0) to pixel PX(m,n). Then, steps S62 to S66 are executed for each pixel to obtain the film thickness estimated value d1(x, y).

In step S62, the CPU 871 derives the film thickness d1(x, y) of the top layer L1 at the pixel PX(x, y) based on the above equation (1). However, the inverse function in equation (1) can have multiple solutions. That is, the reflectance R(λ) and the film thickness d1 have the relationship shown by the curve in FIG. and is obtained as a film thickness candidate (hereinafter referred to as a “film thickness candidate value”).

Here, in order to stably obtain a probable film thickness d1, it is necessary to efficiently narrow down a solution from a plurality of film thickness candidate values. For example, in an ellipsometer, the solution is narrowed down by measuring the luminance value at multiple wavelengths and predicting and fitting the reflectance. However, this embodiment does not have a mechanism for changing the wavelength λ of the observation light L. FIG. Therefore, such an algorithm cannot be applied in this embodiment.

の範囲に含まれる膜厚候補値を抽出し、これを解とすることができる（ステップＳ６３）。ただし、上記範囲に膜厚候補値が１個のみ含まれる場合と、２個含まれる場合とが存在する。そこで、ＣＰＵ８７１は、上記範囲に含まれる膜厚候補値が１個であるか、２個であるかを判定する。そして、膜厚候補値が１個である場合（ステップＳ６４で「１個（ｄ１ａ）」）、ＣＰＵ８７１は当該膜厚候補値を膜厚推定値ｄ１（ｘ，ｙ）と認定する（ステップＳ６５）。一方、膜厚候補値が２個である場合（ステップＳ６４で「２個（ｄ１ａ、ｄ１ｂ）」）、ＣＰＵ８７１は膜厚候補値の決定処理を実行する（ステップＳ６６）。 Therefore, in this embodiment, the CPU 871 narrows down the solution by using the previous film thickness d1_pre. More specifically, when the phase difference φ (=4·π·n(λ, 1)·d1·cos θ/λ) of the interference fringes in the uppermost layer L1 has a half period π, d1=λ/(4·n (λ, 1) cos θ), as shown in FIG.

can be extracted and used as a solution (step S63). However, there are cases where only one film thickness candidate value is included in the above range and there are cases where two are included. Therefore, the CPU 871 determines whether the number of film thickness candidate values included in the range is one or two. Then, when there is one film thickness candidate value ("1 (d1a)" in step S64), the CPU 871 recognizes the film thickness candidate value as the film thickness estimated value d1 (x, y) (step S65). . On the other hand, if there are two film thickness candidate values ("two (d1a, d1b)" in step S64), the CPU 871 executes film thickness candidate value determination processing (step S66).

FIG. 9 is a flow chart showing the process of determining the film thickness candidate value. In this determination process (step S66), one of the two film thickness candidate values is set as the film thickness candidate value d1a, and the other is set as the film thickness candidate value d1b. Also, the film thickness estimated value d1 one loop before in the estimation loop is set as the previous estimated value d1_pre(x, y). A design value d1d is set as the initial value of the immediately preceding estimated value d1_pre(x, y) in the estimation loop.

In step S661, the following formula,
d1a′=d1a−d1_pre(x, y)
d1b′=d1b−d1_pre(x, y)
Differential amounts d1a' and d1b' of the film thickness candidate values are calculated based on (step S661). Then, the amounts of change Ca and Cb of the differential amounts are given by the following equations, respectively:
Ca = d1a'-d1'(x, y)
Cb=d1b'-d1'(x, y)
(step S662). Here, d1'(x, y) is the differential amount of the film thickness estimated value d1 one loop before in the estimation loop (hereinafter referred to as the "previous differential amount"), and the previous differential amount d1'(x, y ) is set to zero as an initial value.

In the next step S663, the amounts of change Ca and Cb are compared. If the change amount Ca is smaller (“NO” in step S663), the film thickness estimated value d1(x, y) is determined as the film thickness candidate value d1a (step S664). Also, for the next loop, the immediately preceding estimated value d1_pre(x, y) and the immediately preceding differential amount d1'(x, y) are respectively d1_pre(x, y)=d1a
d1′(x,y)=d1a′
and stored in the storage unit 872 (step S665).

On the other hand, if the change amount Cb is smaller ("YES" in step S663), the film thickness estimated value d1(x, y) is determined as the film thickness candidate value d1b (step S666). Also, for the next loop, the immediately preceding estimated value d1_pre(x, y) and the immediately preceding derivative d1'(x, y) are respectively d1_pre(x, y)=d1b
d1′(x,y)=d1b′
and stored in the storage unit 872 (step S667).

By executing the above-described film thickness candidate value determination process (step S66), even when there are two film thickness candidate values, it is possible to stably obtain a probable film thickness estimated value d1.

Returning to FIG. 6, the description continues. The film thickness estimation loop is executed for all pixels PX. As a result, the following data is obtained and stored in the storage unit 872.
―――――――――――――――――――――――――――
Pixel PX (0,0) Luminance value I (0,0) Estimated film thickness d1 (0,0)
Pixel PX (1,0) Luminance value I (1,0) Estimated film thickness d1 (1,0)
…
Pixel PX (m, p) Brightness value I (m, p) Estimated film thickness d1 (m, p)
…
Pixel PX (m, n) Brightness value I (m, n) Estimated film thickness d1 (m, n)
―――――――――――――――――――――――――――

The CPU 871 extracts estimated film thickness values d1(0,0) to d1(m,p) for the pixels PX(0,0) to PX(m,p) corresponding to the bevel etching area from the data. Then, the CPU 871 determines the film thickness d1 from those estimated film thickness values d1(0, 0) to d1(m, p) (step S67). For example, the film thickness d1 may be the average value of the film thickness estimated values d1 (0, 0) to d1 (m, p), and the film thickness estimated value d1 (0, 0) may be obtained by assigning a weighting coefficient to each pixel. A weighted average value of ˜d1(m, p) may be used as the film thickness d1. Further, since the bevel etching process has not started at this time, the film thickness d1 may be determined from the film thickness estimated values d1(0, 0) to d1(m, n) of all the pixels.

Furthermore, returning to FIG. 4, the description is continued. When the film thickness d1 of the top layer L1 is obtained immediately before the bevel etching process as described above, the CPU 871 sets the estimated film thickness d1 as the previous film thickness d1_pre of the top layer L1 and stores it in the storage unit 872. (Step S7).

After setting the previous film thickness d1_pre, the bevel etching process is started (step S8). That is, the nozzle heads 44, 45 and 50 are arranged at the processing position by the nozzle moving mechanism 6, and the splash guard 31 is arranged at the upper position by the guard driving mechanism. When preparation for substrate processing is thus completed, the rotation mechanism 231 of the substrate processing apparatus 1 starts rotating the spin chuck 21 holding the substrate W. FIG. Further, power is supplied to the heater of the heating mechanism 7 at an appropriate timing, and heating of the peripheral portion of the substrate W is started. Further, the gas discharge mechanisms 41 and 42 start discharging the inert gas flow from the nozzles 46 and 47 of the nozzle head 44, and the gas discharge mechanism 43 starts the inert gas flow from the nozzle 48 of the nozzle head 45. to start discharging. After the temperature of the peripheral portion of the substrate W rises with the lapse of time, the processing liquid ejection mechanism 51A ejects the liquid flow of the processing liquid (chemical liquid) so as to hit the peripheral portion of the upper surface of the substrate W, thereby increasing the temperature of the peripheral portion of the upper surface. Start processing.

After the start of the bevel etching process, the film thickness d1 of the uppermost layer L1 is obtained by the same process as in step S6 (step S10) each time it is confirmed in step S9 that a certain period of time has elapsed. In other words, the thickness of the top layer L1 decreases moment by moment as the bevel etching process progresses, and the thickness d1 of the top layer L1 is sampled by the thickness estimating mechanism 8 at regular intervals. Therefore, in the present embodiment, it is determined whether the sampled film thickness d1 has reached zero (step S11). This determination is made by the control unit 10, and while the film thickness d1 has not reached zero, that is, the bevel etching process has not been completed ("NO" in step S11), the previous film thickness d1_pre was obtained in step S10. After rewriting to the film thickness d1 (step S12), the process returns to step S9. The bevel etching process is continued while obtaining the film thickness d1 of the uppermost layer L1 at regular intervals in this manner.

On the other hand, when it is confirmed in step S11 that the film thickness d1 has reached zero and the peripheral portion of the uppermost layer L1 has been completely removed by etching, the controller 10 controls each part of the device to end the bevel etching process (step S13). . That is, the heating of the substrate W is stopped by stopping the power supply to the heater, and the discharge of the gas flow is also stopped. Furthermore, the rotation of the spin chuck 21 is stopped. After that, when the hand of the transfer robot (not shown) enters the substrate processing apparatus 1 and receives the processed substrate W, the substrate W is released from the spin chuck 21 . Then, the transport robot unloads the received substrate W to the next substrate processing apparatus (step S14: unloading).

As described above, in the present embodiment, an image of the uppermost layer L1 of the substrate W (for example, symbol IM ), the film thickness d1 of the uppermost layer L1 is estimated. As described above, the film thickness d1 of the uppermost layer L1 is determined using only the observation light L(λ) of the specific wavelength λ without requiring wavelength scanning of the observation light as in the prior art. As described above, according to the present embodiment, the film thickness d1 of the uppermost layer L1 of the substrate W having a multilayer structure can be determined in real time at low cost.

In the above embodiment, the thin film estimation process (step S6) of the uppermost layer L1 is executed immediately before the start of the bevel etching process to set the previous film thickness d1_pre (step S7). Therefore, the film thickness d1 of the top layer L1 immediately before the bevel etching process can be determined with high accuracy, and the film thickness d1 of the top layer L1 can be stably determined even during the bevel etching process. As a result, it is possible to accurately detect the end timing of the bevel etching process, and to effectively prevent the occurrence of excessive or insufficient bevel etching.

The present invention is not limited to the above-described embodiments, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the embodiments, the film thickness estimation method and film thickness estimation device according to the present invention are applied to the substrate processing apparatus 1 that performs bevel etching processing, but the scope of application of the present invention is not limited to this. The present invention can also be applied to an etching apparatus for etching all or part of the uppermost layer L1 of the substrate W. FIG. Besides detecting the etching end, the etching rate of the uppermost layer L1 may be calculated by dividing the amount of change in the film thickness d1 by the sampling period. It is also possible to use the etching rate to maintain the etching rate and to predict and estimate the etching end point. Furthermore, the present invention can also be applied to a substrate processing apparatus that grows the top layer L1 to increase the film thickness d1.

Further, in the above embodiment, a bare silicon substrate is used as a reference sample (corresponding to the "calibration substrate" of the present invention) in response to the example of the substrate W having a two-layer structure in which a silicon oxide film is formed on a silicon wafer. is used as However, the multilayer structure is not limited to the (SiO2/Si) structure and is arbitrary. For example, the present invention can be applied to a substrate processing apparatus for processing a substrate provided with an oxide film, a nitride film, a metal film, an organic film, etc. other than silicon as the uppermost layer L1.

Also, a calibration substrate suitable for a multilayer structure can be used. For example, as in the above embodiment, a reference sample composed only of the material that constitutes the second layer L2 may be used as the "calibration substrate" of the present invention. Also, a reference sample obtained by removing only the uppermost layer from a substrate having a multilayer structure may be used as the "calibration substrate" of the present invention.

In the above embodiment, the thin film estimation process (step S6) of the uppermost layer L1 is executed immediately before the start of the bevel etching process to set the previous film thickness d1_pre (step S7). good too. In this case, the design value d1d of the uppermost layer L1 is the previous film thickness d1_pre immediately before the bevel etching process.

Further, in the above embodiment, the imaging unit 83 is composed of a monochrome two-dimensional camera, but other cameras can be used. For example, a two-dimensional image may be obtained by imaging the rotating substrate W using a monochrome line camera. Alternatively, a color two-dimensional camera may be used. In this case, if the illumination unit 82 is configured with a light source that emits observation light having light components of a plurality of wavelengths, such as a white light source, an image for each wavelength can be acquired by the imaging unit 83 . By executing the above process for each wavelength, the film thickness can be obtained at different wavelengths. Therefore, by comparing and correcting these multiple film thickness estimation results, simple spectroscopic measurement becomes possible, and measurement accuracy and reliability can be improved.

The present invention provides general film thickness estimation techniques for estimating the film thickness of the uppermost layer of a substrate having a multilayer structure in which at least one or more thin films are laminated on a base material layer, and It can be applied to all etching methods using the film thickness estimation technique.

DESCRIPTION OF SYMBOLS 1... Substrate processing apparatus 8... Film thickness estimation mechanism (film thickness estimation apparatus)
82... Illumination unit 83... Imaging unit 87... Film thickness estimation control unit 871... CPU
872... Storage unit A... Gain d1... (top layer) film thickness d1a, d1b... Candidate film thickness value d1d... Design film thickness IM... Image (top layer) k... Extinction coefficient L... Observation light L1... (substrate ) Uppermost layer L2 Second layer (of substrate) Lq Substrate layer n Refractive index PX Pixel q Number of layers R Reflectance RL Reflected light W Substrate λ Wavelength θ Incident angle

Claims (9)

A film thickness estimation method for estimating the film thickness of the uppermost layer of a substrate having a multilayer structure in which at least one or more layers of thin films are laminated on a base material layer, after the substrate is processed, comprising: (a) (b) a refractive index of each layer constituting the multilayer structure at the wavelength λ by irradiating the processed substrate with observation light having a wavelength λ to acquire an image of the uppermost layer of the substrate with an imaging unit; (c) the refractive index, the extinction coefficient and the film thickness stored in step (b); based on the inverse function of the function (R(λ)=f(d1)) showing the relationship between the reflectance R(λ) of the substrate at the wavelength λ and the film thickness d1 of the top layer. estimating the film thickness of the top layer from the luminance values of the pixels forming the image;
A film thickness estimation method comprising: 2. The film thickness estimation method according to claim 1, comprising the step of (d) obtaining a calibration value for performing the step (c),
The step (d) comprises: (d-1) a step of capturing an image with the imaging unit in a dark environment in which the observation light is not emitted; (d-3) irradiating the observation light onto a calibration substrate, the uppermost layer of which is made of a material that constitutes the second layer second from the top in the multilayer structure; (d-4) obtaining the image of the calibration substrate by the imaging unit, and and obtaining a gain A based on
The inverse function is d1=f ⁻¹ ((I(λ)−Ioff)/A),
where I(λ) is the luminance value of the pixels forming the image obtained in step (a);
A film thickness estimation method. The film thickness estimation method according to claim 2,
The gain A is obtained by the following formula A = (I (λ, d-3) - Ioff) / R (λ, d-3))
However, I (λ, d-3) is the luminance value of the pixels constituting the image obtained in the step (d-3),
R(λ, d−3) is the reflectance of the calibration substrate at wavelength λ;
Film thickness estimation method obtained by. 4. The film thickness estimation method according to any one of claims 1 to 3, comprising the step of: (e) acquiring the film thickness of the top layer before processing as the immediately preceding film thickness;
(c-1) for each pixel constituting the image of the top layer, the refractive index, the extinction coefficient, and the film thickness stored in the step (b), and the inverse function; obtaining the film thickness candidate value of the uppermost layer from the luminance value of the pixel based on the above, and then obtaining the film thickness from the film thickness candidate value based on the previous film thickness;
(c-2) determining the film thickness of the top layer from the film thickness estimated value for each pixel;
A film thickness estimation method comprising: The film thickness estimation method according to claim 4,
The step (e) comprises: (e-1) obtaining design values of the top layer of the substrate before processing; and (e-2) irradiating the substrate before processing with observation light to determine obtaining an image; and (e-3) obtaining the previous film thickness based on the refractive index, the extinction coefficient and the film thickness stored in step (b) and the inverse function;
A film thickness estimation method comprising: 2. The film thickness estimation method according to claim 1, wherein said step (a) is a step of irradiating said observation light with light having light components of mutually different wavelengths and acquiring an image for each said wavelength by said imaging unit. and
A film thickness estimation method, wherein the step (b) and the step (c) are performed for each wavelength. A film thickness estimating device for estimating the film thickness of the uppermost layer of a substrate having a multilayer structure in which at least one or more thin films are laminated on a base material layer after the substrate is processed,
an illumination unit that irradiates the processed substrate with observation light having a wavelength λ;
an imaging unit that captures an image of the substrate irradiated with the observation light to obtain an image of the top layer of the substrate;
a storage unit for storing the refractive index and extinction coefficient of each layer constituting the multilayer structure at the wavelength λ, and the film thickness of each layer of the multilayer structure excluding the top layer;
A function (R(λ)=f (d1)) and the inverse function, a film thickness estimating unit for estimating the film thickness of the top layer from the luminance values of the pixels forming the image of the top layer;
A film thickness estimation device comprising: An etching method for etching the uppermost layer of a substrate by supplying a processing liquid to a substrate having a multilayer structure in which at least one or more thin films are laminated on a base material layer,
A film thickness of the uppermost layer of the substrate being treated with the treatment liquid is obtained using the film thickness estimation method according to any one of claims 1 to 6, and the thickness of the treatment liquid is determined according to the film thickness. An etching method characterized by controlling supply. The etching method according to claim 8,
selectively etching the peripheral edge of the top layer by supplying the processing liquid to the peripheral edge of the substrate;
An etching method comprising stopping the supply of the processing liquid to the peripheral portion of the substrate when the estimated film thickness becomes zero.

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