Film thickness estimation method, storage medium, and substrate processing apparatus

Abstract

To estimate a film thickness with high accuracy on the basis of reflected light from a substrate.SOLUTION: A film thickness estimation method comprises the steps of: radiating light toward an irradiation portion set so as to be overlapped with a front surface of a substrate in a rotational period when the substrate in a state where a processing liquid is supplied on the front surface is rotated so as to form a film of the processing liquid on the front surface of the substrate; acquiring a signal waveform indicating a periodical time change in strength of reflection light in the rotational period by receiving the reflection light in which light emitted via the film of the processing liquid after the light is reflected from the front surface of the substrate and light reflected from an outer front surface of the film of the processing liquid are synthesized; acquiring a feature amount at each of a plurality of times from the signal waveform; and calculating a thickness of the film of the processing liquid after the rotational period on the basis of the time change in the feature amount. The feature amount is defined by a time difference between optional one time in the signal waveform and a time deviated by n (n is one or more integer number) period from the one time.SELECTED DRAWING: Figure 12

Description

[Technical field]

[0001] The present disclosure relates to a film thickness estimation method, a storage medium, and a substrate processing apparatus. [Background technology]

[0002] Patent Document 1 discloses a substrate processing apparatus having a film thickness measuring means placed along the radial direction of a substrate having a film formed on its surface, and an arithmetic control unit that controls the amount of chemical discharged, the reciprocating speed of the chemical nozzle, and the substrate rotation speed based on the measurement results output from the film thickness measuring means. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 1-276722 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a film thickness estimation method, a storage medium, and a substrate processing apparatus that are capable of accurately estimating a film thickness based on light reflected from a substrate. [Means for solving the problem]

[0005] A film thickness estimation method according to one aspect of the present disclosure includes irradiating light toward an irradiation location set to overlap with the surface of the substrate during a rotation period during which a substrate with a treatment liquid supplied on its surface is rotated so that a film of the treatment liquid is formed on the surface of the substrate, receiving reflected light that is a combination of light reflected from the surface of the substrate and then emitted through the film of the treatment liquid and light reflected from the outer surface of the film of the treatment liquid, thereby obtaining a signal waveform indicating a periodic time change in the intensity of the reflected light during the rotation period, obtaining a feature amount at each of a plurality of times from the signal waveform, and calculating a thickness of the film of the treatment liquid after the rotation period based on the time change of the feature amount. The feature amount is defined as a time difference between an arbitrary one time in the signal waveform and a time shifted by n (n is an integer equal to or greater than 1) periods from the arbitrary one time. Effect of the Invention

[0006] According to the present disclosure, there are provided a film thickness estimation method, a storage medium, and a substrate processing apparatus capable of accurately estimating a film thickness based on light reflected from a substrate. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of a substrate processing system. [Diagram 2] FIG. 2 is a schematic diagram showing an example of a coating and developing apparatus. [Diagram 3] FIG. 3 is a schematic diagram showing an example of the liquid processing unit and the measuring section. [Figure 4] FIG. 4 is a schematic diagram showing an example of the irradiation position of light from the measurement unit. [Diagram 5] 5(a) and 5(b) are schematic diagrams for explaining the relationship between the film thickness and the reflected light when dry. [Figure 6] FIG. 6 is a block diagram illustrating an example of a functional configuration of the control device. [Figure 7] FIG. 7 is a graph showing an example of the change over time in intensity of reflected light. [Figure 8] FIG. 8 is a block diagram illustrating an example of a hardware configuration of the control device. [Figure 9] FIG. 9 is a flowchart showing an example of a method for generating a model equation for estimating a film thickness. [Figure 10] FIG. 10 is a flow chart showing an example of a liquid treatment and signal acquisition method. [Figure 11] FIG. 11 is a flow chart illustrating an example of a signal analysis method. [Figure 12] Fig. 12(a) is a graph showing an example of a signal waveform before normalization, and Fig. 12(b) is a graph showing an example of a signal waveform after normalization. [Figure 13] FIG. 13 is a graph showing an example of the transition of the film thickness reduction rate obtained when generating the model formula. [Figure 14] FIG. 14 is a graph showing an example of the model formula. [Figure 15] FIG. 15 is a flowchart showing an example of a substrate processing method. [Figure 16] FIG. 16 is a graph showing an example of the change in the film thickness reduction rate obtained when evaluating the film thickness. [Figure 17] FIG. 17 is a graph showing an example of the transition of the time lag obtained when the model formula is generated. [Figure 18] FIG. 18 is a graph showing an example of the transition of the time lag obtained when evaluating the film thickness. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment will be described with reference to the drawings. In the description, the same elements or elements having the same functions are designated by the same reference numerals, and duplicated description will be omitted.

[0009] [Substrate processing system] The substrate processing system 1 (substrate processing apparatus) shown in FIG. 1 is a system that forms a photosensitive coating on a workpiece W, exposes the photosensitive coating, and develops the photosensitive coating. The workpiece W to be processed is, for example, a substrate, or a substrate on which a film, circuit, or the like has been formed by performing a predetermined process. One example of the substrate is a silicon wafer. The workpiece W (substrate) may be circular. The workpiece W may also be a glass substrate, a mask substrate, or an FPD (Flat Panel Display), etc. The photosensitive coating is, for example, a resist film.

[0010] 1 and 2, the substrate processing system 1 includes a coating and developing apparatus 2, an exposure apparatus 3, and a control device 100 (control unit). The exposure apparatus 3 is an apparatus that exposes a resist film (photosensitive coating) formed on a workpiece W (substrate). Specifically, the exposure apparatus 3 irradiates an exposure target portion of the resist film with an energy beam by a method such as immersion exposure.

[0011] The coating and developing apparatus 2 applies a resist (chemical solution) to the surface of the workpiece W to form a resist film before the exposure process by the exposure device 3, and develops the resist film after the exposure process. The coating and developing apparatus 2 includes a carrier block 4, a processing block 5, and an interface block 6.

[0012] The carrier block 4 introduces the workpiece W into the coating and developing apparatus 2 and removes the workpiece W from the coating and developing apparatus 2. The carrier block 4 is capable of supporting, for example, a plurality of carriers C for the workpieces W and has a built-in transport device A1 including a delivery arm. The carrier C accommodates, for example, a plurality of circular workpieces W. The transport device A1 removes the workpiece W from the carrier C and delivers it to the processing block 5, and receives the workpiece W from the processing block 5 and returns it to the carrier C. The processing block 5 has processing modules 11, 12, 13, and 14.

[0013] The processing module 11 incorporates a liquid processing unit U1, a heat processing unit U2, and a transport device A3 that transports the workpiece W to these units. The processing module 11 forms an underlayer film on the surface of the workpiece W using the liquid processing unit U1 and the heat processing unit U2. An example of the underlayer film is a SOC (Spin On Carbon) film. The liquid processing unit U1 applies a processing liquid for forming the underlayer film onto the workpiece W. The heat processing unit U2 performs various heat treatments associated with the formation of the underlayer film.

[0014] The processing module 12 incorporates a liquid processing unit U1, a heat processing unit U2, and a transport device A3 that transports the workpiece W to these units. The processing module 12 forms a resist film on the underlayer film using the liquid processing unit U1 and the heat processing unit U2. The liquid processing unit U1 applies a processing liquid for forming a resist film onto the underlayer film, thereby forming a film of the processing liquid on the underlayer film (on the surface of the workpiece W). The heat processing unit U2 performs various heat treatments associated with the formation of the resist film.

[0015] The processing module 13 incorporates a liquid processing unit U1, a heat processing unit U2, and a transport device A3 that transports the workpiece W to these units. The processing module 13 forms an upper layer film on the resist film using the liquid processing unit U1 and the heat processing unit U2. The liquid processing unit U1 applies a processing liquid for forming the upper layer film onto the resist film. The heat processing unit U2 performs various heat treatments associated with the formation of the upper layer film.

[0016] The processing module 14 incorporates a liquid processing unit U1, a heat processing unit U2, and a transport device A3 that transports the workpiece W to these units. The processing module 14 uses the liquid processing unit U1 and the heat processing unit U2 to perform development processing of the resist film that has been subjected to exposure processing and heat processing associated with the development processing. The liquid processing unit U1 applies a developer to the surface of the exposed workpiece W, and then washes it away with a rinsing liquid to perform development processing of the resist film. The heat processing unit U2 performs various heat processing associated with the development processing. Specific examples of heat processing include a heat processing before development (PEB: Post Exposure Bake) and a heat processing after development (PB: Post Bake), etc.

[0017] A shelf unit U10 is provided on the carrier block 4 side in the processing block 5. The shelf unit U10 is divided into multiple cells arranged in the vertical direction. A transport device A7 including a lifting arm is provided near the shelf unit U10. The transport device A7 lifts and lowers the workpiece W between the cells of the shelf unit U10.

[0018] A shelf unit U11 is provided on the interface block 6 side in the processing block 5. The shelf unit U11 is partitioned into a plurality of cells arranged in the vertical direction.

[0019] The interface block 6 transfers the workpiece W between the exposure apparatus 3. The interface block 6 has a built-in transport device A8 including a transfer arm, for example, and is connected to the exposure apparatus 3. The transport device A8 transfers the workpiece W placed on the shelf unit U11 to the exposure apparatus 3. The transport device A8 receives the workpiece W from the exposure apparatus 3 and returns it to the shelf unit U11.

[0020] The control device 100 controls the coating and developing apparatus 2 to perform the coating and developing process, for example, in the following procedure. First, the control device 100 controls the transport device A1 to transport the workpiece W in the carrier C to the shelf unit U10, and controls the transport device A7 to place the workpiece W in a cell for the processing module 11.

[0021] Next, the control device 100 controls the transport device A3 to transport the workpiece W on the shelf unit U10 to the liquid treatment unit U1 and heat treatment unit U2 in the processing module 11. The control device 100 also controls the liquid treatment unit U1 and heat treatment unit U2 to form an underlayer film on the surface of the workpiece W. Thereafter, the control device 100 controls the transport device A3 to return the workpiece W on which the underlayer film has been formed to the shelf unit U10, and controls the transport device A7 to place the workpiece W in a cell for the processing module 12.

[0022] Next, the control device 100 controls the transport device A3 to transport the workpiece W on the shelf unit U10 to the liquid processing unit U1 and heat processing unit U2 in the processing module 12. The control device 100 also controls the liquid processing unit U1 and heat processing unit U2 to form a resist film on the underlying film of the workpiece W. Thereafter, the control device 100 controls the transport device A3 to return the workpiece W to the shelf unit U10, and controls the transport device A7 to place the workpiece W in a cell for the processing module 13.

[0023] Next, the control device 100 controls the transport device A3 to transport the workpiece W on the shelf unit U10 to each unit in the processing module 13. The control device 100 also controls the liquid processing unit U1 and the heat processing unit U2 to form an upper layer film on the resist film of the workpiece W. Thereafter, the control device 100 controls the transport device A3 to transport the workpiece W to the shelf unit U11.

[0024] Next, the control device 100 controls the transport device A8 to send the workpiece W on the shelf unit U11 to the exposure device 3. Thereafter, the control device 100 controls the transport device A8 to receive the workpiece W that has been subjected to the exposure process from the exposure device 3 and place it in a cell for the processing module 14 in the shelf unit U11.

[0025] Next, the control device 100 controls the transport device A3 to transport the workpiece W on the shelf unit U11 to each unit in the processing module 14, and controls the liquid processing unit U1 and the heat processing unit U2 to perform a developing process on the resist film of the workpiece W. Thereafter, the control device 100 controls the transport device A3 to return the workpiece W to the shelf unit U10, and controls the transport device A7 and the transport device A1 to return the workpiece W into the carrier C. This completes the coating and developing process for one workpiece W. The control device 100 controls the coating and developing apparatus 2 to perform the coating and developing process for each of the subsequent multiple workpieces W in the same manner as described above.

[0026] The specific configuration of the substrate processing apparatus is not limited to the above-described configuration of the substrate processing system 1. The substrate processing apparatus may be any type as long as it includes a liquid processing unit that supplies a processing liquid to a substrate to form a film of the processing liquid, and a control device that can control the liquid processing unit.

[0027] (Liquid processing unit) Next, an example of the liquid processing unit U1 of the processing module 12 will be described with reference to Fig. 3. The liquid processing unit U1 supplies the processing liquid Lp to the front surface Wa of the workpiece W, and then rotates the workpiece W with the processing liquid Lp supplied onto the front surface Wa so that a film of the processing liquid Lp is formed on the front surface Wa. The processing liquid Lp is a solution (resist) for forming a resist film.

[0028] Hereinafter, the liquid film of the processing liquid Lp immediately after the processing liquid Lp is supplied and the film of the processing liquid Lp before solidification in which volatilization has progressed with the rotation of the workpiece W are collectively referred to as the "coating film AF". After the rotation of the workpiece W for volatilization, the coating film AF is heated in the heat treatment unit U2, so that the coating film AF is solidified to form a resist film. In this disclosure, the film of the processing liquid Lp includes the coating film AF and the resist film after the coating film AF has solidified. In addition, in the liquid processing unit U1, the volatilization of the liquid film of the processing liquid Lp is progressed to a degree that does not solidify it is referred to as "drying". As shown in FIG. 3, the liquid processing unit U1 has a spinning and holding unit 30 and a processing liquid supply unit 40.

[0029] The rotating holding unit 30 holds and rotates the workpiece W. The rotating holding unit 30 has, for example, a holding unit 32, a shaft 34, and a rotation drive unit 36. The holding unit 32 (support unit) supports the workpiece W. The holding unit 32 supports, for example, the center of the workpiece W arranged horizontally with the surface Wa facing up, and holds the workpiece W by vacuum suction or the like. The upper surface of the holding unit 32 (the surface supporting the workpiece W) may be formed in a circular shape when viewed from above, and may have a radius of about 1 / 6 to 1 / 2 times the radius of the workpiece W. The rotating drive unit 36 ​​is connected to the lower part of the holding unit 32 via the shaft 34.

[0030] The rotation drive unit 36 ​​is an actuator including a power source such as an electric motor, and rotates the holder 32 around a vertical axis Ax. The rotation of the holder 32 by the rotation drive unit 36 ​​rotates the workpiece W held (supported) by the holder 32. The holder 32 may hold the workpiece W such that a center CP (see FIG. 4) of the workpiece W approximately coincides with the axis Ax.

[0031] The processing liquid supply unit 40 supplies the processing liquid Lp to the surface Wa of the workpiece W held by the spin holder 30. The processing liquid supply unit 40 has, for example, a nozzle 42, a supply source 44, an opening / closing valve 46, and a nozzle drive unit 48. The nozzle 42 ejects the processing liquid Lp onto the surface Wa of the workpiece W held by the holder 32 of the spin holder 30. The nozzle 42 is disposed, for example, above the workpiece W (vertically above the center CP of the workpiece W) and ejects the processing liquid Lp downward. The supply source 44 supplies the processing liquid Lp to the nozzle 42.

[0032] The opening / closing valve 46 is provided in the supply path between the nozzle 42 and the supply source 44. The opening / closing valve 46 switches the supply path between an open and closed state. The nozzle driving unit 48 moves the nozzle 42 between a discharge position above the workpiece W and a retracted position away from the discharge position. The discharge position is, for example, a position vertically above the center of rotation of the workpiece W (a position on the axis Ax). The standby position is, for example, set to a position outside the periphery of the workpiece W.

[0033] (Measuring section) The coating and developing apparatus 2 further includes a measuring section 60 for measuring reflected light from the surface Wa of the workpiece W on which the coating film AF is formed. The measuring section 60 is provided in the liquid processing unit U1. The measuring section 60 rotates the workpiece W after the processing liquid Lp is supplied, and irradiates light onto the rotating workpiece W during the period in which the coating film AF is formed. The measuring section 60 irradiates light capable of penetrating the coating film AF (processing liquid Lp) on the surface Wa onto the surface Wa of the workpiece W held by the holding section 32, and receives reflected light from the workpiece W that is generated in response to the irradiated light.

[0034] The measurement unit 60 has, for example, light emitting and receiving devices 70A to 70C. The light emitting and receiving devices 70A to 70C each irradiate light toward irradiation points P1 to P3 set to overlap with the surface Wa of the workpiece W on the holder 32, and receive the reflected light reflected from the irradiation points P1 to P3. The irradiation points P1 to P3 are fixed positions and do not change even if the workpiece W rotates. Each of the light emitting and receiving devices 70A to 70C irradiates laser light as irradiation light toward the surface Wa of the workpiece W. Each of the light emitting and receiving devices 70A to 70C irradiates laser light that can pass through a coating film AF of a processing liquid formed on the surface Wa.

[0035] Each of the light emitting and receiving devices 70A to 70C may irradiate the laser light downward along a direction perpendicular to the surface Wa of the workpiece W. Unlike the example shown in Fig. 3, each of the light emitting and receiving devices 70A to 70C may irradiate the laser light obliquely downward along a direction inclined with respect to the direction perpendicular to the surface Wa of the workpiece W.

[0036] The laser light emitted from each of the light emitting and receiving devices 70A to 70C may be visible light or infrared light. The wavelength of the laser light may be 500 nm to 1200 nm, 600 nm to 1100 nm, or 780 nm to 1000 nm. The wavelength of the laser light may be set according to the type of the treatment liquid Lp. For example, the wavelength of the laser light is set so as not to promote a reaction in the treatment liquid Lp and to reduce light absorption.

[0037] The frequencies (wavelengths) of the laser beams irradiated from the light emitting and receiving devices 70A to 70C may be different from each other. That is, the frequency of the light irradiated from the light emitting and receiving device 70A toward the irradiation point P1 may be different from the frequency of the light irradiated from the light emitting and receiving device 70B (light emitting and receiving device 70C) toward the irradiation point P2 (irradiation point P3). The light sources included in each of the light emitting and receiving devices 70A to 70C may be laser diodes or LEDs. The beam width of the laser beam may be about several mm to several tens of mm.

[0038] The irradiation points P1 to P3 of the light (laser light) from the light projecting and receiving devices 70A to 70C are set at different positions from each other as shown in FIG. That is, the measurement unit 60 irradiates the laser light toward the irradiation point P1 and the irradiation points P2 and P3 set to overlap the surface Wa of the workpiece W at a position different from the irradiation point P1. The distances between the irradiation point P1 of the light from the light projecting and receiving device 70A, the irradiation point P2 of the light from the light projecting and receiving device 70B, and the irradiation point P3 of the light from the light projecting and receiving device 70C and the center CP of the workpiece W are different from each other. In one example, the distance between the irradiation point P1 and the center CP of the workpiece W is smaller than the distance between the irradiation point P2 and the center CP of the workpiece W. The distance between the irradiation point P2 and the center CP of the workpiece W is smaller than the distance between the irradiation point P3 and the center CP of the workpiece W.

[0039] The irradiation point P1, the irradiation point P2, and the irradiation point P3 may be arranged in a line in this order from the center CP of the workpiece W along the radial direction of the workpiece W. The irradiation point P1, the irradiation point P2, and the irradiation point P3 may be arranged at approximately equal intervals. The irradiation point P1 is located at the center of the front surface Wa of the workpiece W. Specifically, the irradiation point P1 is set so as to overlap with the upper surface of the holding part 32 (the surface that supports the back surface of the workpiece W). The irradiation point P3 located on the outside is located in an area (peripheral area) near the periphery of the workpiece W. As described above, the light emitting and receiving devices 70A to 70C function as a light emitting part that irradiates light toward a predetermined area (irradiation point) set so as to overlap with the front surface Wa of the workpiece W.

[0040] The light projecting and receiving device 70A receives light emitted from the irradiation point P1. Specifically, the light projecting and receiving device 70A receives reflected light obtained by combining light emitted through the coating film AF after reflecting off the surface Wa of the workpiece W and light reflected off the outer surface Fa of the coating film AF at the irradiation point P1. At each of the irradiation points P2 and P3, the laser light is also reflected by the outer surface Fa of the coating film AF and the surface Wa located under the coating film AF. That is, the light projecting and receiving devices 70B and 70C also receive light emitted from the irradiation points P2 and P3, respectively, similar to the light projecting and receiving device 70A. More specifically, the light projecting and receiving devices 70B and 70C receive reflected light obtained by combining light emitted through the coating film AF after reflecting off the surface Wa of the workpiece W and light reflected off the outer surface Fa of the coating film AF at the irradiation points P2 and P3, respectively.

[0041] Each of the light projecting and receiving devices 70A to 70C may generate an electric signal according to the intensity of the reflected light received. The laser light can pass through the coating film AF on the surface Wa of the workpiece W. Therefore, the laser light is reflected by the outer surface Fa (upper surface) of the coating film AF, and is also reflected by the surface Wa of the workpiece W located under the coating film AF, and then emitted through the coating film AF. In the present disclosure, the surface Wa of the workpiece W on which a part of the laser light is reflected is the surface of the base material contained in the workpiece W, or the surface of another film that exists under the coating film AF and has already been solidified. The other film may be, for example, a film (for example, the above-mentioned underlayer film) that exists directly under the coating film AF. As described above, the light projecting and receiving devices 70A to 70C also function as a light receiving unit that receives reflected light that is a combination of light reflected by the outer surface Fa of the coating film AF of the processing liquid on the surface Wa and light reflected by the surface Wa.

[0042] Here, the change in the intensity of the reflected light over time will be described with reference to Fig. 5(a) and Fig. 5(b). The reflected light has an intensity according to the thickness of the coating film AF of the processing liquid during the period when the coating film AF of the processing liquid is formed on the surface Wa of the workpiece W. In Fig. 5(a) and Fig. 5(b), the part of any one of the light-emitting and receiving devices that emits the laser light is indicated as "light-emitting part 72", and the part that receives the reflected light is indicated as "light-receiving part 74". Note that Fig. 5(a) and Fig. 5(b) illustrate a case where light is incident on the surface Wa from an oblique direction, unlike Fig. 3.

[0043] The reflected light accompanying the laser light irradiated toward the surface Wa of the workpiece W includes, as described above, the light L1 that passes through the coating film AF of the processing liquid, reflects off the surface Wa, and is then emitted to the outside through the coating film AF, and the light L2 that does not enter the coating film AF and is reflected by the outer surface Fa of the coating film AF. The reflected light received by the light receiving unit 74 is the reflected light Lc obtained by combining the light L1 and the light L2. Depending on the thickness of the coating film AF, the phase of the light L2 relative to the light L1 changes, and there are cases where the light L1 and the light L2 strengthen each other or weaken each other. As shown in FIG. 5(a), when the peak portion of the amplitude of the light L1 and the peak portion of the amplitude of the light L2 overlap, the light L1 and the light L2 strengthen each other, and the intensity of the reflected light becomes large. On the other hand, as shown in FIG. 5(b), when the peak portion of the amplitude of the light L1 and the valley portion of the amplitude of the light L2 overlap, the light L1 and the light L2 weaken each other, and the intensity of the reflected light becomes small.

[0044] Immediately after the processing liquid Lp is supplied to the surface Wa, a liquid film of the processing liquid Lp is formed, and then, by rotating the workpiece W, the drying (volatilization) of the coating film AF gradually progresses. Therefore, while the workpiece W is being rotated, the thickness of the coating film AF gradually decreases. This causes the phase of the light L2 relative to the light L1 to change, and a mutually strengthening state and a mutually weakening state are alternately (periodically) repeated. As a result, a waveform showing the time change in the intensity of the reflected light is obtained, which changes periodically so that peaks and valleys are alternately repeated (see FIG. 7).

[0045] When a base (e.g., another already solidified film, a circuit pattern, etc.) is present directly below the coating film AF rather than the base material of the workpiece W, the reflected light accompanying the laser light may include, in addition to the above-mentioned light L1 and light L2, another light emitted through both the coating film AF and the base. Even in this case, since the intensity of the reflected light through the base is smaller than the light L1 and L2, the phase relationship between the light L1 and the light L2 changes periodically according to the time change in the thickness of the coating film AF, and a waveform that changes periodically such that peaks and valleys are alternately repeated is obtained. In the substrate processing system 1 of the present disclosure, such a periodically changing waveform is analyzed to estimate the thickness (film thickness) of the film of the processing liquid Lp after the rotation of the workpiece W to dry the coating film AF. Details of the film thickness estimation method will be described later.

[0046] (Control device) The control device 100 controls the coating and developing apparatus 2 partially or entirely, thereby causing the coating and developing apparatus 2 to perform processing on the workpiece W. As shown in Fig. 6, the control device 100 has, for example, a processing information storage unit 112, a liquid processing control unit 114, and a film thickness estimation unit 120 as functional configurations (hereinafter referred to as "functional modules"). The processing performed by these functional modules corresponds to the processing performed by the control device 100.

[0047] The processing information storage unit 112 stores processing information related to liquid processing for the workpiece W. Various conditions for performing liquid processing are set in the processing information. For example, the various conditions include the timing (time from a reference time point) for starting and stopping the discharge of the processing liquid, the rotation speed (number of rotations) of the workpiece W when the processing liquid Lp is discharged, the rotation speed of the workpiece W when drying the coating film AF on the surface Wa after the supply of the processing liquid Lp, and the rotation time of the workpiece W when drying the coating film AF, and the like, which are determined in advance.

[0048] The liquid treatment control unit 114 controls the liquid treatment unit U1 to perform liquid treatment on the workpiece W. The liquid treatment control unit 114 controls the spin holding unit 30 and the treatment liquid supply unit 40 to perform liquid treatment on the workpiece W according to various conditions stored in the treatment information storage unit 112. For example, the liquid treatment control unit 114 rotates the workpiece W using the spin holding unit 30 while supplying the treatment liquid Lp to the front surface Wa of the workpiece W using the treatment liquid supply unit 40. The liquid treatment control unit 114 rotates the workpiece W with the treatment liquid Lp supplied to its front surface Wa using the spin holding unit 30 so that a film of the treatment liquid Lp (a coating film AF in a state where solidification has progressed) is formed on the front surface Wa of the workpiece W.

[0049] The film thickness estimation unit 120 acquires a waveform (hereinafter referred to as a "signal waveform") indicating a periodic time change in the intensity of reflected light from the workpiece W from the measurement unit 60. The film thickness estimation unit 120 estimates the thickness of the film of the processing liquid Lp formed on the surface Wa after the rotation period for drying the coating film AF by analyzing the signal waveform obtained from the measurement unit 60. In this manner, the substrate processing system 1 has a film thickness estimation device 20 including the measurement unit 60 and the film thickness estimation unit 120 (see FIG. 4). Hereinafter, the thickness of the film of the processing liquid Lp after the rotation period for drying the coating film AF is referred to as the "film thickness after the rotation period". The film thickness after the rotation period may be the film thickness of the coating film AF after the rotation period and before the heat treatment is performed, or may be the film thickness of a resist film formed by solidifying the coating film AF by the heat treatment in the heat treatment unit U2.

[0050] The film thickness estimation unit 120 includes, as functional modules, for example, a light projection control unit 122, a signal acquisition unit 124, a feature amount acquisition unit 126, a film thickness calculation unit 128, a model information storage unit 132, and a model construction unit 134. The processes executed by these functional modules correspond to the processes executed by the film thickness estimation unit 120 or the control device 100.

[0051] The light projection control unit 122 controls the light projecting and receiving devices 70A-70C to irradiate light toward irradiation points P1-P3 set to overlap with the surface Wa of the workpiece W during a rotation period in which the workpiece W is rotated by the rotation holding unit 30 of the liquid processing unit U1 after the supply of the processing liquid Lp. The light projection control unit 122 may start the irradiation of light from the light projecting and receiving devices 70A-70C when starting drying of the coating film AF by rotation after stopping the discharge of the processing liquid Lp in the liquid processing on the workpiece W. The light projection control unit 122 may stop the irradiation of light from the light projecting and receiving devices 70A-70C after stopping the rotation for drying the coating film AF.

[0052] The signal acquisition unit 124 acquires, from each light-emitting and receiving device, a signal waveform indicating a periodic time change in the intensity of the reflected light Lc received by the light-emitting and receiving device during the above-mentioned rotation period. As described above, the reflected light Lc is light obtained by combining the light L1 reflected by the surface Wa of the workpiece W and then emitted through the coating film AF, and the light L2 reflected by the outer surface Fa of the coating film AF. The signal acquisition unit 124 may acquire the intensity of the reflected light Lc at a predetermined sampling period. The sampling period is set to a degree that allows the change in the interference state between the light L1 reflected by the surface Wa and the light L2 reflected by the outer surface Fa of the coating film AF to be observed by the signal waveform. The sampling period may be set to about several tens of ms to several hundreds of ms.

[0053] FIG. 7 shows an example of a signal waveform acquired by the signal acquisition unit 124. The signal waveform changes periodically, so that peaks and valleys are alternately repeated. In FIG. 7, a maximum P, which is the apex of a peak, is indicated by a black circle, and a minimum V, which is the apex of a valley, is indicated by a white circle. These maximums P and minimums V are points (extreme values) where the differential value is zero. The intensities at the multiple maximums P may be different from each other, and the intensities at the multiple minimums V may be different from each other. In the signal waveform shown in FIG. 7, rotation (drying) for drying the coating film AF is started at time t1, and rotation for drying the coating film AF is stopped at time t2.

[0054] The feature amount acquiring unit 126 acquires feature amounts at a plurality of times (a plurality of times in the signal waveform) from the signal waveform acquired by the signal acquiring unit 124. These plurality of times may correspond to a sampling period when acquiring the signal waveform. The feature amount is a value acquired from the signal waveform according to a predetermined condition. The feature amount is used to calculate the film thickness after a rotation period for drying the coating film AF, and the details thereof will be described later. For example, the feature amount acquiring unit 126 acquires feature amounts at a plurality of times from the signal waveform for each of the irradiation points P1 to P3.

[0055] The film thickness calculation unit 128 calculates the film thickness after the rotation period based on the change over time of the feature amount acquired by the feature amount acquisition unit 126. For example, the film thickness calculation unit 128 calculates the film thickness for each of the irradiation points P1 to P3 based on the change over time of the feature amount. The film thickness calculation unit 128 may calculate the film thickness after the rotation period based on the change over time of the feature amount and a model formula previously constructed for estimating the film thickness after the rotation period.

[0056] The model information storage unit 132 stores a model formula that is constructed in advance to estimate the film thickness after a rotation period. This model formula is constructed so as to indicate the relationship between an index (to be described in detail later) obtained from the time change of the feature amount at each of a plurality of times of the signal waveform and the estimated value of the film thickness after the rotation period.

[0057] The model construction unit 134 generates a model formula for estimating the film thickness after the rotation period. For example, the model construction unit 134 performs a liquid treatment (a test liquid treatment) by changing the rotation speed in multiple steps when drying the coating film AF for each of a plurality of test workpieces W. Then, the model construction unit 134 acquires an index obtained from a time change in a feature amount based on a signal waveform and a measurement value indicating a film thickness after the rotation period (for example, a film thickness of a resist film after a heat treatment) for each test liquid treatment. Then, the model construction unit 134 generates a model formula indicating a relationship between the index and the film thickness after the rotation period based on the value of the index obtained in multiple test liquid treatments and the measurement value of the film thickness. The model construction unit 134 may generate a model formula for each irradiation location, or may generate one model formula for multiple irradiation locations.

[0058] The control device 100 is composed of one or more control computers. For example, the control device 100 has a circuit 150 shown in FIG. 8. The circuit 150 has one or more processors 152, a memory 154, a storage 156, an input / output port 158, and a timer 162. The storage 156 has a computer-readable storage medium such as a hard disk. The storage medium stores a program for causing the control device 100 to execute a film thickness estimation method described below. The storage medium may be a removable medium such as a non-volatile semiconductor memory, a magnetic disk, or an optical disk.

[0059] The memory 154 temporarily stores the programs loaded from the storage medium of the storage 156 and the results of calculations by the processor 152. The processor 152 configures the above-mentioned functional modules by executing the above-mentioned programs in cooperation with the memory 154. The input / output port 158 ​​inputs and outputs electrical signals between the spin holder 30, the processing liquid supply unit 40, the measurement unit 60, etc., in accordance with instructions from the processor 152. The timer 162 measures the elapsed time, for example, by counting reference pulses at a constant cycle.

[0060] When the control device 100 is configured with a plurality of control computers, each functional module may be realized by an individual control computer. Alternatively, each of these functional modules may be realized by a combination of two or more control computers. The control device 100 may be configured with a control computer including a functional module for performing liquid processing by the liquid processing unit U1, and a control computer including a functional module for estimating the film thickness after a rotation period (the above-mentioned film thickness estimation unit 120). In these cases, the multiple control computers may be connected to each other so as to be able to communicate with each other and cooperate to execute a film thickness estimation method to be described later. Note that the hardware configuration of the control device 100 is not necessarily limited to one in which each functional module is configured by a program. For example, each functional module of the control device 100 may be configured by a dedicated logic circuit or an ASIC (Application Specific Integrated Circuit) that integrates the dedicated logic circuit.

[0061] [Thickness estimation method] Next, an example of a series of processes executed by the control device 100 will be described as an example of a film thickness estimation method. The series of processes executed by the control device 100 includes a series of processes at a stage of constructing a model formula (hereinafter referred to as a "preparation stage") and a series of processes at a stage of evaluating the film thickness after constructing the model formula (hereinafter referred to as a "production stage"). In the preparation stage, a resist film is formed on a test workpiece W by the liquid processing unit U1 and the heat processing unit U2, and a process for constructing a model formula is executed in parallel with the formation process. In the production stage, a resist film is formed on a production workpiece W by the liquid processing unit U1 and the heat processing unit U2. Then, a process for estimating a film thickness after a rotation period of the workpiece W, whose film thickness is unknown, is executed in parallel with the formation process.

[0062] (Preparation stage) First, a method for constructing a model formula in the preparation stage will be described. In the preparation stage, a test process is performed for each of a plurality of test workpieces W while changing the set value of the rotation speed in a plurality of stages. That is, a plurality of test processes are performed with the rotation speeds set to different values. In the test process, a resist film formation process (liquid processing in the liquid processing unit U1 and heat processing in the heat processing unit U2) is performed under the same processing conditions as in the production stage, except for the set value of the rotation speed. The test workpiece W (hereinafter referred to as the "test workpiece WT") is of the same type as the workpiece W to which liquid processing, etc. is performed in the production stage.

[0063] 9 is a flowchart showing an example of a series of processes executed by the control device 100 in the method for constructing a model formula. In this series of processes, the control device 100 executes step S11 while the test workpiece WT is held by the spin holding part 30. In step S11, for example, the control device 100 sets to an initial value the setting value of the rotation speed when drying the coating film AF after the processing liquid Lp is supplied to the test workpiece WT (test substrate).

[0064] The set value of the rotation speed when drying the coating film AF (hereinafter referred to as the "rotation speed during drying") is preset in multiple stages by a user such as an operator, and is stored in the processing information storage unit 112. Here, a case will be described where the set value of the rotation speed during drying is set to three stages. In the following, the set values ​​of the rotation speed during drying are represented as "ω1", "ω2", and "ω3", with ω1, ω2, and ω3 having smaller values ​​in that order. In one example, the control device 100 sets the smallest value (ω1) as the set value of the initial rotation speed.

[0065] Next, the control device 100 executes step S12. In step S12, for example, the control device 100 controls the liquid treatment unit U1 to perform liquid treatment on the test workpiece WT under the same conditions as in the production stage, except for the set value of the rotation speed during drying. In parallel with the liquid treatment performed by the liquid treatment unit U1, the control device 100 controls the measurement section 60 to acquire the above-mentioned signal waveform under the same conditions as in the production stage. As a result, a coating film AF is formed on the test workpiece WT, and a signal waveform based on the reflected light from the surface Wa of the test workpiece WT is acquired. Details of step S12 will be described later.

[0066] Next, the control device 100 executes step S13. In step S13, for example, the film thickness estimation unit 120 executes analysis of the signal waveform obtained in the immediately preceding step S12. In step S12, the film thickness estimation unit 120 acquires feature amounts at each of a plurality of times of the signal waveform, and acquires an index (index value) for estimating the film thickness after the rotation period from the time change of the plurality of feature amounts. The details of step S13 will be described later.

[0067] Next, the control device 100 executes step S14. In step S14, for example, the control device 100 controls the heat treatment unit U2 to perform heat treatment on the test workpiece WT under the same conditions as in the production stage. As a result, the coating film AF formed on the test workpiece WT is solidified, and a resist film is formed.

[0068] Next, the control device 100 executes step S15. In step S15, for example, the control device 100 acquires a measurement value indicating the thickness of the resist film formed on the surface Wa of the test workpiece WT. The measurement value of the resist film thickness may be a value measured by any method (using any type of film thickness measuring device) other than calculation of the film thickness based on a signal waveform. The measurement value of the resist film thickness may be, for example, a film thickness measured based on the spectrum obtained by dispersing light reflected from the resist film.

[0069] Next, the control device 100 executes step S16. In step S16, for example, the control device 100 determines whether or not the series of processes in steps S12 to S15 has been completed in all stages where the set value of the rotation speed is changed. If it is determined in step S16 that the series of processes has not been completed in all stages where the setting value of the rotation speed is changed (step S16: NO), the process executed by the control device 100 proceeds to step S17.

[0070] In step S17, for example, the control device 100 changes the setting value of the rotation speed when drying the coating film AF. This sets the rotation speed in the test process for the next test workpiece WT. The test workpiece WT used next may be the same individual as the test workpiece WT that was subjected to the series of processes (test processes) of steps S12 to S15 before step S17, or it may be a different individual. If the same individual is used, a process of peeling off the resist film on the surface Wa may be further performed. In one example, the control device 100 sets the setting value of the rotation speed during drying of the next test workpiece WT to ω2.

[0071] Thereafter, the control device 100 repeats the processing of steps S12 to S16 (S17) until processing is completed for all stages in which the rotation speed setting value is changed. As a result, a series of processing (test processing) of steps S12 to S15 is executed on the test workpiece WT for each stage of the rotation speed setting value. In one example, the rotation speed during drying is set to ω1, ω2, and ω3, respectively, and a series of processing of steps S12 to S15 is executed on the test workpiece WT. As a result, a measurement value indicating the film thickness of the resist film after heat treatment and an analysis result of the signal waveform in step S13 (the above-mentioned index for film thickness estimation) are obtained for each rotation speed setting value.

[0072] Next, the control device 100 executes step S18. In step S18, for example, the model constructing unit 134 generates a model formula for estimating a film thickness in the production stage based on the measured values ​​and the analysis results of the signal waveform obtained in the test process repeatedly executed before step S18. The details of the method for generating the model formula will be described later. An example of step S12, an example of step S13, and an example of step S18 will be described in detail below.

[0073] <Liquid processing and signal waveform acquisition> 10 is a flow chart showing an example of step S12. In step S12, the control device 100 first executes step S21. In step S21, for example, the liquid processing control unit 114 controls the rotation drive unit 36 ​​of the spin holder 30 so that the workpiece W rotates at a predetermined rotation speed set for when the processing liquid Lp is supplied. The rotation speed at this time may be approximately the same as the set value of the rotation speed during drying, or may be lower than the set value.

[0074] Next, the control device 100 executes step S22. In step S22, for example, the liquid treatment control unit 114 controls the treatment liquid supply unit 40 to discharge the treatment liquid Lp from the nozzle 42 onto the front surface Wa of the test workpiece WT rotated by the spin holding unit 30. The liquid treatment control unit 114 may cause the treatment liquid supply unit 40 to start discharging the treatment liquid Lp from the nozzle 42 by transitioning the opening / closing valve 46 provided in the supply path that leads the treatment liquid Lp to the nozzle 42 from a closed state to an open state. This causes the treatment liquid supply unit 40 to start supplying the treatment liquid Lp to the front surface Wa of the test workpiece WT.

[0075] Next, the control device 100 executes steps S23 and S24. In step S23, for example, the liquid processing control unit 114 waits until a predetermined discharge time has elapsed since the start of discharge of the processing liquid in step S22. The discharge time is determined in advance and is set to a time that is long enough for a liquid film of the processing liquid Lp to be formed on the surface Wa. In step S24, for example, the liquid processing control unit 114 controls the processing liquid supply unit 40 to stop discharging the processing liquid Lp from the nozzle 42. The liquid processing control unit 114 may cause the processing liquid supply unit 40 to stop discharging the processing liquid Lp from the nozzle 42 by transitioning the opening / closing valve 46 from an open state to a closed state. This stops the supply of the processing liquid Lp from the processing liquid supply unit 40 to the surface Wa of the test workpiece WT, and a coating film AF before drying (volatilization) progresses is formed on the surface Wa of the test workpiece WT.

[0076] Next, the control device 100 executes step S25. In step S25, for example, the liquid processing control unit 114 controls the rotation holder 30 so that the test workpiece WT rotates at the set value of the rotation speed during drying that was set before the execution of step S12 started. By rotating the test workpiece WT at the set value of the rotation speed during drying, drying of the coating film AF formed on the front surface Wa of the test workpiece WT starts.

[0077] Next, the control device 100 executes step S26. In step S26, for example, the film thickness estimating unit 120 waits until a predetermined measurement start timing is reached. The predetermined measurement start timing is, for example, a time from a start point of the liquid processing when the start point is set as a reference point, and is set in advance by an operator or the like so that a periodic change appears in the signal waveform.

[0078] Next, the control device 100 executes step S27. In step S27, for example, the film thickness estimation unit 120 controls the measurement unit 60 to start measuring the intensity of the reflected light Lc. In one example, the light projection control unit 122 controls the light projecting and receiving devices 70A-70C to start irradiating the irradiation points P1-P3 with laser light, respectively. At the same timing, the signal acquisition unit 124 starts acquiring the intensity of the reflected light Lc accompanying the irradiation of the laser light from each of the light projecting and receiving devices 70A-70C. In the subsequent processing, the irradiation of the laser light and the acquisition of the intensity of the reflected light Lc are continued.

[0079] Next, the control device 100 executes steps S28 and S29. In step S28, for example, the liquid processing control unit 114 waits until a predetermined drying time has elapsed after execution of step S25. The drying time is preset to a degree that allows the drying of the coating film AF to progress, and may be longer than the discharge time in step S23. In step S29, for example, the liquid processing control unit 114 controls the rotation holding unit 30 to stop the rotation of the test workpiece WT. By executing the above steps S28 and S29, the test workpiece WT in a state in which the processing liquid Lp has been supplied rotates for a predetermined drying time, and a film of the processing liquid (the coating film AF in a state in which drying has progressed) is formed on the surface Wa of the test workpiece WT after the drying time has elapsed.

[0080] Next, the control device 100 executes step S30. In step S30, for example, the film thickness estimation unit 120 controls the measurement unit 60 to stop measuring the intensity of the reflected light Lc. In one example, the light projection control unit 122 controls the light projecting and receiving devices 70A-70C to stop irradiating the irradiation points P1-P3 with the laser light, respectively. Then, the signal acquisition unit 124 stops acquiring the intensity of the reflected light Lc accompanying the irradiation of the laser light. By executing the above processes of steps S26-S30, a signal waveform (waveform showing periodic time changes in the intensity of the reflected light) as shown in FIG. 7 is acquired for each of the irradiation points P1-P3. With the above, the control device 100 ends the process of step S12.

[0081] <Signal Waveform Analysis> Fig. 11 is a flow chart showing an example of step S13. In step S13, the control device 100 first executes step S51. In step S51, for example, the feature acquisition unit 126 extracts extreme values ​​contained in the signal waveform obtained in the immediately preceding step S12. Specifically, the feature acquisition unit 126 extracts multiple minimums V and multiple maximums P contained in the signal waveform as multiple extreme values. Fig. 12(a) shows a part of the signal waveform acquired by the signal acquisition unit 124 during execution of step S12, and the part of the waveform includes some of the extracted minimums V and maximums P.

[0082] Next, the control device 100 executes step S52. In step S52, for example, the feature acquisition unit 126 identifies data (one section of the waveform) included in the half cycle to be processed in the next step S53 from the signal waveform. This half cycle means the period from an arbitrary extreme value to the next extreme value in the signal waveform. These arbitrary extreme values ​​and the next extreme value are adjacent to each other on the time axis. The half cycle can be rephrased as a half wavelength in the signal waveform. In the following, the half cycle will be described assuming that a signal waveform in which a minimum V first appears is obtained in step S12, and that the signal waveform includes k minimums V and k maximums P. k is an integer equal to or greater than 1. In addition, the minimum that appears at the kth position among the multiple minimums V included in the signal waveform is referred to as the minimum V. k and the kth maximum among multiple maxima P is denoted as maxima P k It is written as follows.

[0083] The kth maximum P that appears counting from the reference point in time k is the kth minimum V k The (k+1)th minimum V k+1 The signal waveform has a minimum V k From maximum P k (hereinafter, "period T1 k ") and the half period corresponding to the maximum P k From minimum V k+1 (hereinafter, "period T2k In this case, the signal waveform includes a half period corresponding to the period T1. k and period T2 k In step S52 which is executed first, the feature amount acquiring section 126 specifies, for example, waveform (intensity) data included in the period T11 as the processing target.

[0084] Next, the control device 100 executes step S53. In step S53, for example, the feature acquisition unit 126 normalizes the signal waveform intensity for the half cycle data identified in step S52. In normalizing the signal waveform intensity, the feature acquisition unit 126 performs normalization by converting only the intensity without converting the value on the time axis for the half cycle data.

[0085] More specifically, the feature acquisition unit 126 calculates a conversion value In for each half cycle using the following equation (1), and converts the intensity of the signal waveform based on the conversion value In to generate a normalized waveform (hereinafter referred to as the "normalized waveform"). In=(Ix-Imin) / (Imax-Imin) ···(1) In equation (1), the parameters Ix, Imin, Imax, and In are defined as follows, respectively. Ix: Signal waveform intensity at any time x included in the half cycle Imin: The minimum value of the signal waveform in the corresponding half cycle (intensity at minimum V) Imax: Maximum value in the signal waveform during the half cycle (intensity at the local maximum P) In: Transform value of signal waveform intensity at time x

[0086] The feature acquisition unit 126 may generate a normalized waveform by converting the intensity of the signal waveform so that the intensity in the normalized waveform coincides with the conversion value In obtained by the formula (1). In this case, the intensity at the minimum V is converted to 0, the intensity at the maximum P is converted to 1, and the intensity between the minimum V and the maximum P in the half cycle data is converted to a value according to the ratio to the difference in intensity between the minimum V and the maximum P. Converting the intensity of the signal waveform based on the conversion value In calculated by the formula (1) includes converting the intensity to a range other than the range of 0 to 1. For example, the feature acquisition unit 126 may generate a normalized waveform by doubling the formula (1) and subtracting 1 from it so that the range of the intensity after conversion is -1 to 1. The feature acquisition unit 126 converts the intensity of the signal waveform based on the conversion value In obtained by the formula (1) at each of a plurality of calculation time points in the half cycle data. At this time, a plurality of calculation time points (intervals between calculation time points) may coincide with a sampling period when acquiring the signal waveform.

[0087] Next, the control device 100 executes step S54. In step S54, for example, the feature acquisition unit 126 judges whether normalization has been completed for all half cycles. If it is judged in step S54 that normalization has not been completed for all half cycles (step S54: NO), the feature acquisition unit 126 repeats steps S52 to S54. In step S52, the feature acquisition unit 126 may specify, as the processing target, the half cycle next to the half cycle that was the processing target in the previous step S52. In one example, in the second step S52, the feature acquisition unit 126 specifies the waveform (intensity) data included in the period T21 as the processing target. Then, in the second step S53, the feature acquisition unit 126 normalizes the intensity of the waveform data included in the period T21 by calculation using the above-mentioned formula (1).

[0088] If it is determined in step S54 that normalization has been completed for all half cycles (step S54: YES), the process executed by the control device 100 proceeds to step S55. By repeating the series of processes from steps S52 to S54, the signal waveform is normalized in units of half cycles, and a normalized waveform such as that shown in Fig. 12(b) is obtained. In the normalized waveform exemplified in Fig. 12(b), the intensity at each of the multiple maxima P is normalized to 1, and the intensity at each of the multiple minima V is normalized to 0.

[0089] In step S55, for example, the feature acquisition unit 126 acquires feature amounts from the normalized waveform at each of a plurality of time points of the normalized waveform. The feature amount is defined as the time difference between any one time point in the normalized waveform and a time shifted by n periods from the time point. n is an integer equal to or greater than 1. n may be 1, in which case the feature amount is defined as the time difference between any one time point in the normalized waveform and a time shifted by one period from the time point. The plurality of times (plurality of sampling time points) at which the feature amounts are acquired may coincide with the sampling period when the signal waveform is acquired.

[0090] Here, a variable representing the time difference between an arbitrary time and a time shifted by one cycle from the arbitrary time is denoted as "delta time Dt". At a time shifted by one cycle from an arbitrary time in a normalized waveform, its intensity matches the intensity at the arbitrary time. And, between the arbitrary time and the time shifted by one cycle, one maximum P and one minimum V are included (two or more maximum Ps are not included, and two or more minimum Vs are not included). The time shifted by one cycle may be a time one cycle before that has an intensity matching the intensity at the arbitrary time, or may be a time one cycle after that. It is known that the tendency of change in a signal waveform is different between a half cycle in which the signal changes from the maximum P to the minimum V and a half cycle in which the signal changes from the minimum V to the maximum P. Therefore, by acquiring the time difference before and after one cycle as a feature, it is possible to obtain a signal waveform for a period T1. k and period T2 k It is possible to obtain feature values ​​without being affected by differences in trends between the two.

[0091] In Fig. 12(b), any time within one half cycle in which the normalized waveform changes from a minimum V to a maximum P is called "t i The time one period ahead that matches the intensity at time ti is indicated by "t i+2π At time t i and time t i+2π The intensities at time t and t t t coincide with each other, and the waveform advances by one wavelength (one period) between these times. i Delta time Dt i is calculated by the following formula (2). i+2π is contained in another half-period that goes from a minimum V to a maximum P. Dt i =t i+2π -t i (2)

[0092] In Fig. 12(b), any time within one half cycle in which the normalized waveform changes from maximum P to minimum V is called "t j " Also, at this time t j The time one period ahead that matches the intensity at is "t j+2π At time t j and time t j+2π The intensities at time t and t t t coincide with each other, and the waveform advances by one wavelength (one period) between these times. j Delta time Dt j is calculated by the following formula (3). j+2π is contained in another half-period that goes from a maximum P to a minimum V. Dt j =t j+2π -t j (3)

[0093] Next, the control device 100 executes step S56. In step S56, for example, the feature acquisition unit 126 calculates a film thickness reduction speed Ds from the delta time Dt calculated in step S55 at each of the multiple time points. The film thickness reduction speed Ds is a variable indicating the reduction width of the film thickness of the coating film AF per unit time while the rotation for drying the coating film AF is continued. The film thickness reduction speed Ds at each of the multiple time points is calculated by the following formula (4). Ds = d / Dt (4)

[0094] In the above formula (4), "d" is a constant indicating the amount of film thickness reduction when the signal intensity in the signal waveform changes by one wavelength, and is acquired in advance. One wavelength corresponds to, for example, a waveform between adjacent maximums and maximums, or a waveform between adjacent minimums and minimums. In a signal waveform indicating a periodic change in reflected light over time, the amount of film thickness change between adjacent maximums and maximums (between minimums and minimums) changes depending on the wavelength of the laser light and the type of the processing liquid Lp. In other words, when the wavelength of the laser light and the type of the processing liquid Lp are determined, the amount of film thickness reduction corresponding to the change of one wavelength is determined regardless of the rotation speed during drying. In one example, the constant d is acquired by a user or the like acquiring through an experiment the difference in film thickness of the coating film AF that results in signal waveforms that are shifted by one wavelength from each other.

[0095] From equation (4), it can be seen that the film thickness reduction rate Ds is a variable that depends on the delta time Dt. When the dryness state of the coating film AF changes, it is considered that the time it takes for the signal waveform to advance by one wavelength changes, so the film thickness reduction rate Ds and delta time Dt are also variables that represent the dryness state of the coating film AF formed on the surface Wa. Figure 13 shows a curve that represents the transition (time change) of the film thickness reduction rate Ds. Hereinafter, the curve that represents the transition of the film thickness reduction rate Ds is referred to as the "state transition curve."

[0096] In Fig. 13, "ω1", "ω2", and "ω3" each represent the set value of the rotation speed during drying. For example, when the set value of the rotation speed during drying is set to ω1 in step S11, the state transition curve indicated by ω1 is obtained by the calculation in step S56. The curve illustrated in Fig. 13 has a tendency that the value of the film thickness reduction rate Ds becomes smaller as drying progresses. In this case, the degree of progress of drying per unit time (degree of volatilization) is greater in the early stage of the drying time than in the later stage of the drying time.

[0097] Returning to FIG. 11, next, the control device 100 executes step S57. In step S57, for example, the feature acquisition unit 126 acquires a solidification time ST as an index for evaluating the film thickness after the rotation period from a state transition curve (test transition curve) representing the transition of the film thickness reduction speed Ds calculated in step S56. The solidification time ST is a variable defined as the time at which the film thickness reduction speed Ds coincides with a predetermined trigger value Tr in the curve representing the transition of the film thickness reduction speed Ds. The trigger value Tr is a value set to a value (film thickness reduction speed) that is evaluated as having progressed to a certain degree in the process of drying the coating film AF, and is set by, for example, an operator. The trigger value Tr is a value that is set in advance so that the correlation between the solidification time ST and the film thickness after the rotation period becomes strong.

[0098] The trigger value Tr is set so as to be included in the range between the maximum and minimum values ​​of the reduction rate Ds at any time (any one time) of the trigger setting period Ptr defined below in a plurality of state transition curves obtained by the test process executed for each of the plurality of test workpieces WT. The trigger setting period Ptr is a period that satisfies the condition that the difference dd between the maximum and minimum values ​​of the film thickness reduction rate Ds at one time in the plurality of state transition curves is greater than a predetermined value. That is, at any time included in the trigger setting period Ptr, the difference dd between the maximum and minimum values ​​of the film thickness reduction rate Ds is greater than a predetermined value. This predetermined value is set in advance so that the correlation between the solidification time ST and the film thickness after the rotation period becomes strong. The predetermined value may be 5 nm / s, 10 nm / s, or 15 nm / s.

[0099] Depending on the type of processing liquid Lp or the timing of acquiring the signal waveform, the state transition curve may include a period during which the film thickness reduction rate Ds increases. In this case, the trigger setting period Ptr is set to a period during which the film thickness reduction rate Ds has a tendency to consistently decrease and the difference between the maximum and minimum values ​​of the film thickness reduction rate Ds at each time is greater than a predetermined value. The trigger value Tr may be set near the center of the range between the maximum and minimum values ​​of the reduction rate Ds at any time during the trigger setting period Ptr (for example, a range of 1 / 3 including the center of the range).

[0100] In FIG. 13, "st1" is a value acquired as the solidification time ST in the state transition curve obtained when the set value of the rotation speed during drying is ω1. Similarly, "st2" is a value acquired as the solidification time ST in the state transition curve obtained when the set value of the rotation speed during drying is ω2. "st3" is a value acquired as the solidification time ST in the state transition curve obtained when the set value of the rotation speed during drying is ω3. Since ω3 is larger than ω1 and ω2, drying proceeds faster. Therefore, in the state transition curve when the rotation speed during drying is set to ω3, the film thickness reduction rate Ds decreases at an earlier timing than in other curves. As a result, when the rotation speed during drying is ω3, the value of the solidification time ST is smaller than the other set values.

[0101] As described above, the test process is performed on each of the multiple test workpieces WT while changing the set value of the rotation speed in multiple stages. Each test process includes steps S12 to S15. In this case, each test process includes the following first to sixth processes. The first process is a process of irradiating light from the light emitting and receiving devices 70A to 70C toward each of the irradiation points P1 to P3 during a rotation period (test rotation period) during which the test workpiece WT, with the treatment liquid Lp supplied onto its surface Wa, is rotated at the set value of the rotation speed in the test process so that a film of the treatment liquid Lp is formed on the surface Wa of the test workpiece WT.

[0102] The second process is a process of acquiring a signal waveform (test signal waveform) showing a periodic time change in the intensity of the reflected light during the test rotation period by receiving a reflected light (synthetic reflected light) that is a combination of the light that is reflected by the surface Wa of the test workpiece WT and then emitted through the coating film AF and the light that is reflected by the outer surface of the coating film AF on the test workpiece WT. The third process is a process of acquiring a delta time Dt (corresponding feature amount) at each of a plurality of times from the signal waveform acquired in the second process.

[0103] The fourth process is a process for acquiring a state transition curve (test transition curve) showing the transition of the film thickness reduction rate Ds (test variable) indicating the drying state of the coating film AF on the surface Wa of the test workpiece WT based on the time change of the delta time Dt acquired in the third process. The fifth process is a process for acquiring a solidification time ST (test solidification time) at which the value of the film thickness reduction rate Ds becomes a trigger value Tr in the state transition curve acquired in the fourth process. The sixth process is a process for acquiring a measurement value indicating the film thickness formed on the test workpiece WT after a rotation period.

[0104] <Construction of model formula> In the preparation stage, the control device 100 executes a test process including steps S12 and S13 for each of a plurality of test workpieces WT while changing the set value of the rotation speed during drying in a plurality of stages. In step S18, the model construction unit 134 generates a model formula based on the execution results of these test processes. It has been found that there is a strong correlation between the solidification time ST obtained in step S13 and the film thickness after the rotation period obtained in step S15. Therefore, the model construction unit 134 constructs a model formula based on the acquired values ​​of the solidification time ST obtained by executing the test process multiple times and the measured values ​​of the film thickness.

[0105] In detail, the model construction unit 134 generates a model formula showing the relationship between the solidification time ST and the film thickness after the rotation period. As shown in FIG. 14, the model construction unit 134 may generate a linear formula (linear approximation formula) showing the relationship between the solidification time ST and the film thickness after the rotation period based on a plurality of acquired values ​​of the solidification time and a plurality of measured values ​​of the film thickness for each irradiation location. In one example, the model construction unit 134 calculates the coefficient a and the constant b that satisfy the relationship of the following formula (5) by the least squares method when the film thickness after the rotation period is "Th", the coefficient is "a", and the constant is "b" for each irradiation location. The model construction unit 134 stores the generated model formula in the model information storage unit 132. Th = a × ST + b (5)

[0106] In the above-mentioned multiple test processes, the set value of the rotation speed during drying of the coating film AF is set to at least a first rotation speed and a second rotation speed different from the first rotation speed. In this case, the film thickness estimation unit 120 acquires a signal waveform (first signal waveform) indicating a periodic time change in the intensity of the reflected light (first reflected light) during a rotation period (first rotation period) during which the test work WT (first test substrate) is rotated at the first rotation speed. The film thickness estimation unit 120 acquires a delta time Dt (first feature amount) at each of a plurality of times from the signal waveform acquired in the test process at the first rotation speed, and acquires a state transition curve (first state transition curve) indicating the transition of the film thickness reduction speed Ds (first variable) indicating the drying state of the coating film AF. Then, the film thickness estimation unit 120 acquires a solidification time ST (first solidification time) at which the value of the reduction speed Ds becomes a trigger value Tr from the state transition curve.

[0107] The film thickness estimation unit 120 also acquires a signal waveform (second signal waveform) indicating a periodic time change in the intensity of the reflected light (second reflected light) during a rotation period (second rotation period) during which the test work WT (second test substrate) is rotated at the second rotation speed. The film thickness estimation unit 120 acquires a delta time Dt (second feature amount) at each of a plurality of times from the signal waveform acquired in the test process at the second rotation speed, and acquires a state transition curve (second state transition curve) indicating the transition of the film thickness reduction rate Ds (second variable) indicating the drying state of the coating film AF. Then, the film thickness estimation unit 120 acquires from the state transition curve the solidification time ST (second solidification time) at which the value of the reduction rate Ds becomes the trigger value Tr.

[0108] The film thickness estimation unit 120 at least acquires a film thickness measurement value (first measurement value) after a rotation period in a test process at a first rotation speed, and acquires a film thickness measurement value (second measurement value) after a rotation period in a test process at a second rotation speed. The model construction unit 134 constructs the model formula shown in the above formula (5) based on at least the film thickness measurement value after the solidification time and rotation period obtained in the test process at the first rotation speed and the film thickness measurement value after the solidification time and rotation period obtained in the test process at the second rotation speed.

[0109] (Production stage) Next, a series of processes executed by the control device 100 to estimate the film thickness after constructing the model formula will be described. Fig. 15 is a flow chart showing an example of a series of processes executed by the control device 100 in the production stage. In this series of processes, the liquid process control unit 114 of the control device 100 performs liquid process on the workpiece W to be processed according to the process conditions stored in the process information storage unit 112. In parallel with this liquid process, the film thickness estimation unit 120 acquires a signal waveform based on the reflected light Lc from the surface Wa of the workpiece W during the liquid process.

[0110] Control device 100 executes steps S71 to S80 in the same manner as steps S21 to S30 shown in Fig. 11. In step S25 shown in Fig. 11, the rotation of workpiece W is adjusted to the set value of the rotation speed during drying in the test process. In contrast, in step S75, liquid process control unit 114 controls rotation holder 30 so that workpiece W rotates at the set value of the rotation speed during drying defined in the process conditions stored in process information storage unit 112.

[0111] Next, the control device 100 executes step S81. In step S81, for example, the control device 100 controls the heat treatment unit U2 to perform heat treatment on the workpiece W to be treated on which the coating film AF is formed. As a result, the coating film AF on the front surface Wa of the workpiece W is solidified, and a resist film is formed on the front surface Wa.

[0112] Next, the control device 100 executes step S82. In step S82, for example, the film thickness estimation unit 120 calculates the film thickness of the resist film from the signal waveform obtained in the processes up to step S80 (estimates the film thickness). Specifically, the feature amount acquisition unit 126 of the film thickness estimation unit 120 executes processes similar to steps S51 to S54 to generate a normalized waveform from the signal waveform. Then, similar to step S55, the feature amount acquisition unit 126 acquires delta times Dt as feature amounts at each of a plurality of times from the normalized waveform.

[0113] Next, the feature amount acquiring unit 126 calculates the film thickness reduction speed Ds by dividing the constant d by the delta time Dt at each of the multiple time points, similar to step S56. As a result, the feature amount acquiring unit 126 acquires a state transition curve that represents the transition of the film thickness reduction speed Ds of the coating film AF formed on the surface Wa of the workpiece W to be processed, as shown in Fig. 16. Thereafter, the feature amount acquiring unit 126 acquires the value of the solidification time ST (evaluated solidification time) that coincides with the trigger value Tr in the state transition curve, similar to step S57. In Fig. 16, the acquired value of the solidification time ST is indicated by "ta".

[0114] Next, the film thickness calculation unit 128 inputs the acquired value of the solidification time ST (the above ta) into the model formula stored in the model information storage unit 132, thereby acquiring the calculation result of the model formula as an estimated value of the film thickness. This completes the estimation of the film thickness at the production stage for one workpiece W. The control device 100 (film thickness estimation unit 120) may repeatedly execute the series of processes of steps S71 to S82 for each of the subsequent multiple workpieces W.

[0115] [Variations] (1) The method of calculating the film thickness is not limited to the above example. In the above example, the solidification time ST is obtained from a state transition curve that represents the transition of the film thickness reduction rate Ds, but the solidification time may be obtained from a curve that represents the transition of the delta time Dt. The curve that represents the transition of the delta time Dt is also referred to as a "state transition curve." In order to distinguish it from the solidification time ST obtained from the state transition curve that represents the transition of the film thickness reduction rate Ds, the solidification time obtained from the state transition curve that represents the transition of the delta time Dt is expressed as "solidification time STd."

[0116] FIG. 17 shows a number of state transition curves representing the transition of delta time Dt obtained in the preparation stage (model formula construction stage). These state transition curves are obtained by executing five test processes by changing the rotation speed during drying to five stages from ωd1 to ωd5. In this case, in the above-mentioned fourth process of each test process, instead of the state transition curve representing the transition of the film thickness reduction rate Ds, a state transition curve representing the transition of delta time Dt (test variable) indicating the drying state of the coating film AF on the surface Wa of the test workpiece WT is obtained. Note that ωd1 to ωd5 are set in advance by an operator or the like so that they increase in this order.

[0117] The solidification time STd is the time when the delta time Dt coincides with the trigger value Trd in the state transition curve representing the transition of the delta time Dt. The trigger value Trd is a value set to an evaluated value (delta time) when a certain degree of drying has progressed in the process of drying the coating film AF, similar to the above-mentioned trigger value Tr, and is set in advance by, for example, an operator. The trigger value Trd may be set as follows in the state transition curve representing the transition of the delta time Dt obtained in the test process performed on each of the multiple test workpieces WT, by calculating the film thickness reduction rate from the delta time Dt of each state transition curve.

[0118] The trigger value Trd is set so as to be included in the range between the maximum and minimum values ​​of the delta time Dt at any time in the trigger setting period Ptrd defined below in a plurality of state transition curves representing the transition of the delta time Dt. The trigger setting period Ptrd is a period that satisfies the condition that the difference between the maximum and minimum values ​​at one time of the film thickness reduction rate Ds converted from the state transition curves representing the transition of the delta time Dt is greater than a predetermined value. That is, in the trigger setting period Ptrd, at any time, the difference between the maximum and minimum values ​​at each time of the film thickness reduction rate Ds converted from the delta time Dt is greater than a predetermined value. This predetermined value may be 5 nm / s, 10 nm / s, or 15 nm / s, as in the setting of the trigger setting period Ptr described above. As described above, in the setting of the trigger setting period Ptrd, each of the plurality of state transition curves representing the transition of the delta time Dt is converted into the film thickness reduction rate Ds, and then the values ​​are evaluated.

[0119] Similarly to the above example, when the solidification time STd is used as an index for evaluating the film thickness after the rotation period, the model construction unit 134 generates a model equation showing the relationship between the solidification time STd and the film thickness after the rotation period. In one example, the model construction unit 134 calculates, for each irradiation location, the coefficient a1 and the constant b1 that satisfy the relationship of the following formula (6) when the coefficient is "a1" and the constant is "b1" by the least squares method. In formula (6), Th indicates the film thickness after the rotation period. Th = a1 × ST1 + b1 (6)

[0120] 18 shows a state transition curve representing the transition of delta time Dt obtained in the production stage. The feature acquisition unit 126 acquires the value of the solidification time STd (evaluated solidification time) that coincides with the trigger value Trd in the state transition curve representing the transition of the delta time Dt. In FIG. 18, the acquired value of the solidification time STd is indicated by "tad". Then, the film thickness calculation unit 128 inputs the acquired value of the solidification time STd (above tad) into the model formula shown in the above formula (6) to acquire the calculation result of the model formula as an estimated value of the film thickness.

[0121] (2) The feature quantity (delta time Dt) corresponds to the time difference between an arbitrary time in the normalized waveform and a time shifted by n periods from that time, where n is 1 in the above example. Unlike the above example, n may be an integer of 2 or more. For example, when n is 2, the feature quantity (delta time Dt) is defined as the time difference between an arbitrary time in the normalized waveform and a time shifted by two periods from that time. In this case, the period T1 during which the arbitrary time changes from a minimum V to a maximum P is k When the time is included in the period T1, the time that is two periods away is k+2 or period T1 k-2 Any time point is included in the period T2 where the value changes from the maximum value P to the minimum value V. k When the time is included in the period T2, the time that is two periods away is k+2 or period T2 k-2 Included in.

[0122] (3) The feature amount (delta time Dt) may be the time difference between any one time in the signal waveform before normalization and a time shifted by n periods from the one time. In this case, the feature amount acquiring unit 126 may acquire, as the feature amount (delta time Dt), the time difference between adjacent minimums V on the time axis and the time difference between adjacent maximums P on the time axis. Note that the feature amount (delta time Dt) obtained from the normalized waveform is substantially equivalent to the feature amount (delta time Dt) obtained from the signal waveform.

[0123] (4) The control device 100 may change the conditions of the liquid treatment for the subsequent workpiece W according to the film thickness calculated by the film thickness calculation unit 128. The control device 100 (film thickness estimation unit 120) may have a process condition change unit 136 as a functional module, as shown in FIG. 6. The process condition change unit 136 changes the setting values ​​of various conditions of the liquid treatment included in the process information stored in the process information storage unit 112, based on the film thickness after the rotation period calculated by the film thickness calculation unit 128. For example, when the absolute value of the difference between the film thickness after the rotation period and a predetermined target film thickness is larger than a predetermined value, the process condition change unit 136 changes the setting value of the rotation speed of the workpiece W during drying of the coating film AF so that the absolute value of the difference is reduced.

[0124] (5) The film thickness calculation unit 128 may correct the film thickness after the rotation period calculated using the above model formula according to the measured temperature. As shown in FIG. 3, the measurement unit 60 may have a temperature sensor 80. The temperature sensor 80 is a sensor that measures the temperature at a predetermined position in a treatment chamber for performing liquid treatment to form a film of the treatment liquid Lp on the surface Wa of the workpiece W. The treatment chamber is formed by a housing that houses the spin holder 30 and a part of the treatment liquid supply unit 40. In one example, the temperature sensor 80 is provided in the holder 32 and measures the temperature of the holder 32.

[0125] The temperature of the holding unit 32 affects the temperature of the central part of the coating film AF. Therefore, if the temperature of the holding unit 32 deviates from a predetermined reference temperature, the film thickness after drying (after the rotation period) may change at the irradiation point P1 and its vicinity even if the processing conditions are the same. From the above, the film thickness calculation unit 128 may correct the film thickness after the rotation period (the estimated film thickness at the irradiation point P1) calculated using the model formula according to the deviation between the measurement value by the temperature sensor 80 and the reference temperature. For example, the film thickness calculation unit 128 may correct the film thickness after the rotation period so that the change in film thickness due to the deviation is canceled (reduced) according to the deviation of the temperature. The film thickness calculation unit 128 may correct the model formula according to the deviation, or may correct the calculation result by the model formula according to the deviation without changing the model formula. The temperature sensor 80 may be provided in a cup member surrounding the spin holding unit 30, unlike the example shown in FIG. 3. In this case, the film thickness calculation unit 128 may correct the estimated value of the film thickness at the irradiation point P3 based on the value measured by the temperature sensor 80.

[0126] The configuration of the measuring unit 60 (light-emitting and receiving devices 70A to 70C) is not limited to the above example. The measuring unit 60 may have one light-emitting and receiving device instead of the light-emitting and receiving devices 70A to 70C. In this case, the film thickness estimation unit 120 estimates the film thickness for one irradiation position. The measuring unit 60 may have one or more pairs of a light-emitting device (light-emitting unit) and a light-receiving device (light-receiving unit) instead of the light-emitting and receiving devices. A mirror member that changes the optical path of the irradiated light and the reflected light may be disposed in the optical path between the light-emitting device and the light-receiving device. The light source of the light-emitting device may be provided outside the housing that houses the rotating holder 30 and a part of the processing liquid supply unit 40.

[0127] In the above example, the thickness of the resist film or the coating film AF in the process of forming the resist film is estimated, but the type of film is not limited to the resist film. The film thickness estimation unit 120 may estimate the film thickness after the rotation period, for example, for the above-mentioned lower layer film or upper layer film.

[0128] [Effects of the embodiment] The above-described film thickness estimation method includes irradiating light toward irradiation points P1 to P3 set to overlap with the surface Wa of the workpiece W during a rotation period during which the workpiece W, with the treatment liquid supplied onto its surface Wa, is rotated so that a film (coating film AF) of the treatment liquid Lp is formed on the surface Wa of the workpiece W; receiving reflected light Lc, which is a combination of light L1 reflected from the surface Wa of the workpiece W and then emitted through the film of the treatment liquid Lp, and light L2 reflected from the outer surface Fa of the film of the treatment liquid, to obtain a signal waveform indicating a periodic time change in the intensity of the reflected light Lc during the rotation period; obtaining a feature amount (delta time Dt) at each of a plurality of times from the signal waveform; and calculating the thickness of the film of the treatment liquid Lp after the rotation period based on the time change of the feature amount. The feature amount is defined as the time difference between an arbitrary one time in the signal waveform and a time shifted by n (n is an integer equal to or greater than 1) periods from the arbitrary one time.

[0129] The reflected light received by the light receiving unit may contain components other than the light L1 that is reflected by the surface Wa of the workpiece W and then emitted through the film of the processing liquid Lp, and the light L2 that is reflected by the outer surface of the film of the processing liquid Lp. For example, the light may also be irradiated onto a layer that exists below the surface Wa, and the reflected light may contain light that is emitted from the film of the processing liquid Lp through this layer. In this case, if the physical quantity at a certain time in the signal waveform is evaluated to calculate the film thickness, there is a risk that the film thickness cannot be calculated accurately due to the influence of components other than the light L1 and the light L2.

[0130] In contrast, in the film thickness estimation method, a feature value is acquired at each of a plurality of times from a signal waveform that indicates a periodic time change in the intensity of the reflected light Lc. In the signal waveform, the time difference between any one time and a time shifted by n periods from the given time depends on the change in the film thickness of the processing liquid Lp during the rotation period. Therefore, by acquiring the time difference as a feature value, it is possible to acquire from the signal waveform an amount that depends on the state of the film thickness of the processing liquid Lp during the rotation period. As a result, by calculating the film thickness based on the time change in the feature value, even if a component other than the light L1 and the light L2 is included in the reflected light, the influence of the component on the calculated film thickness value can be reduced. Therefore, it is possible to accurately estimate the film thickness based on the reflected light from the workpiece W.

[0131] The feature amount may be defined as a time difference between an arbitrary time in the signal waveform and a time shifted by one period from the arbitrary time. In the signal waveform, the time difference between an arbitrary time and a time shifted by one period from the arbitrary time corresponds to the time for the waveform to advance by one wavelength, and depends on the change in film thickness of the film of the processing liquid Lp during the rotation period. Therefore, by calculating the film thickness based on the time change of the time difference (delta time Dt), an estimated value of the film thickness can be obtained from the feature amount that depends on the change in the film thickness. Therefore, it is possible to accurately estimate the film thickness from the signal waveform based on the reflected light.

[0132] The film thickness estimation method may further include generating a normalized waveform from the signal waveform after acquiring the signal waveform and before acquiring the feature amount. Generating the normalized waveform may include generating the normalized waveform by normalizing the intensity of the signal waveform in half-cycle units, where the period from an arbitrary extreme value to the next extreme value in the signal waveform is defined as a half-cycle. The feature amount may be defined as a time difference between an arbitrary time in the normalized waveform and a time shifted by n cycles from the arbitrary time. In this case, when calculating the time difference at a time located between the maximum P and the minimum V of the signal waveform, the point where the normalized intensity coincides can be calculated as the time shifted by n cycles, so that the calculation of the time difference becomes easy. Therefore, it is possible to simplify the calculation of the film thickness based on the time change of the feature amount.

[0133] Normalizing the intensity of the signal waveform in half-cycle units may include calculating a conversion value In for each half cycle using the above formula (1) and converting the signal waveform based on the conversion value In for each half cycle. In this case, even if the values ​​of multiple maxima P in the signal waveform are different from each other and the values ​​of multiple minima V are different from each other, the intensity between one extreme value and the next extreme value is converted to the same range between different half cycles. Therefore, the difference between an arbitrary time and a time shifted by n cycles can be easily calculated, which makes it possible to simplify the calculation of the feature amount.

[0134] Calculating the thickness of the film of the processing liquid Lp may include obtaining a state transition curve showing the transition of a variable indicating the drying state of the film of the processing liquid Lp based on the time change of the feature amount, obtaining an estimated solidification time at which the value of the variable becomes a predetermined trigger value Tr, Trd in the state transition curve, and calculating the thickness of the film of the processing liquid based on a model formula previously constructed for estimating the thickness of the film of the processing liquid Lp and the estimated solidification time. In the state transition curve, a strong correlation was found between the solidification time at which the value of the variable becomes the trigger value and the thickness of the film of the processing liquid Lp after the rotation period. Therefore, it is possible to estimate the film thickness with high accuracy based on the solidification time that has a strong correlation with the film thickness after the rotation period. In addition, it is possible to simplify the calculation in calculating the film thickness by applying the obtained solidification time to the model formula to calculate the film thickness.

[0135] The film thickness estimation method may further include constructing a model formula. The constructing of the model formula includes irradiating light toward irradiation points P1 to P3 during a first rotation period during which a first test substrate, with the processing liquid Lp supplied onto its surface Wa, is rotated at a first rotation speed so as to form a film of the processing liquid Lp on the surface Wa, and receiving a first reflected light that is a combination of light that is reflected off the surface Wa of the first test substrate and then emitted through the film of the processing liquid Lp and light that is reflected off the outer surface of the film of the processing liquid Lp on the first test substrate, thereby generating a first signal waveform that indicates a periodic time change in intensity of the first reflected light during the first rotation period. acquiring a first feature amount corresponding to the feature amount at each of a plurality of times from the first signal waveform; acquiring a first state transition curve expressing a transition of a first variable indicating a drying state of the film of the processing liquid Lp on the surface Wa of the first test substrate based on the time change of the first feature amount; acquiring a first solidification time at which the value of the first variable becomes trigger values ​​Tr, Trd in the first state transition curve; acquiring a first measurement value indicating a thickness of the film of the processing liquid Lp formed on the first test substrate after the first rotation period; during a second rotation period in which the second test substrate is rotated at a second rotation speed so that a film of the processing liquid Lp is formed on the surface Wa of the second test substrate, light is irradiated toward the irradiation points P1 to P3, and a second reflected light is received which is a combination of light that is reflected from the surface Wa of the second test substrate and then emitted through the film of the processing liquid Lp, and light that is reflected from an outer surface of the film of the processing liquid on the second test substrate, thereby obtaining a second signal waveform which indicates a periodic time change in the intensity of the second reflected light during the second rotation period, and acquiring a second feature corresponding to the feature, acquiring a second state transition curve representing the transition of a second variable indicating the drying state of the film of the processing liquid Lp on the surface Wa of the second test substrate based on the change over time of the second feature, acquiring a second solidification time at which the value of the second variable becomes a trigger value in the second state transition curve, acquiring a second measurement value indicating the thickness of the film of the processing liquid Lp formed on the second test substrate after the second rotation period, and generating a model formula based on the first solidification time, the first measurement value, the second solidification time, and the second measurement value.If the rotation speed of the workpiece W during rotation to form a film of the processing liquid Lp is different, the transition of the variables indicating the drying state of the film of the processing liquid Lp will be different. As a result, the acquired value of the solidification time that coincides with the trigger value and the measured film thickness will be different. In the above method, a model formula is constructed based on the measured values ​​of the solidification time and film thickness obtained at different rotation speeds, so it is possible to construct a model formula that outputs an estimated value of the film thickness with high accuracy.

[0136] Constructing the model formula may include executing a test process for each of a plurality of test substrates while changing the rotation speed setting value in multiple stages, and generating the model formula based on the results of the execution of the test process. The test process may include irradiating light toward irradiation points P1 to P3 during a test rotation period in which a test substrate with the processing liquid Lp supplied on its surface Wa is rotated at a set value of the rotation speed for the test process so that a film of the processing liquid Lp is formed on the surface Wa of the test substrate, receiving a composite reflected light that is a combination of light that is reflected on the surface Wa of the test substrate and then emitted through the film of the processing liquid Lp and light that is reflected on the outer surface of the film of the processing liquid Lp on the test substrate, thereby obtaining a test signal waveform that indicates a periodic time change in the intensity of the composite reflected light during the test rotation period, obtaining corresponding feature amounts corresponding to the feature amounts at each of a plurality of times from the test signal waveform, obtaining a test transition curve that indicates the transition of a test variable that indicates a drying state of the film of the processing liquid Lp on the surface Wa of the test substrate based on the time change in the corresponding feature amount, obtaining a test solidification time at which the value of the test variable becomes a trigger value Tr, Trd in the test transition curve, and obtaining a measurement value that indicates the thickness of the film of the processing liquid formed on the test substrate after the test rotation period. In a plurality of test transition curves obtained by the test processes respectively performed on a plurality of test substrates, when a period satisfying a condition that the difference between the maximum value and the minimum value at a certain time of the decrease rate Ds representing the decrease width per unit time of the film thickness of the film of the processing liquid Lp is larger than a predetermined value is defined as a trigger setting period, the trigger value may be set to be included in the range between the maximum value and the minimum value of the test variable at any time of the trigger setting period. In this case, the strength of the correlation between the solidification time acquired so as to coincide with the trigger value and the film thickness after the rotation period can be increased. As a result, it is possible to accurately estimate the film thickness based on the solidification time and the model formula.

[0137] The film thickness estimation method may further include measuring the temperature at a predetermined position in a processing chamber for performing processing to form a film of the processing liquid Lp on the surface Wa of the workpiece W, and correcting the thickness of the film of the processing liquid Lp calculated using the model formula according to the deviation between the measured value of the temperature at the predetermined position and a reference temperature. If the temperature deviates from the reference temperature, the state transition curve representing the transition of the dry state of the film thickness may also change according to the deviation of the temperature. In this method, the film thickness is corrected according to the deviation of the temperature, so that it is possible to estimate the film thickness with higher accuracy.

[0138] The substrate processing system 1 described above includes a rotating holding unit 30 configured to hold and rotate the workpiece W, a processing liquid supply unit 40 configured to supply processing liquid Lp to the surface Wa of the workpiece W held by the rotating holding unit 30, a light-projecting unit (light-projecting and receiving devices 70A-70C) configured to irradiate light toward irradiation points P1-P3 set to overlap with the surface Wa of the workpiece W held by the rotating holding unit 30, a light-receiving unit (light-projecting and receiving devices 70A-70C) configured to receive reflected light Lc that is a combination of light L1 reflected by the surface Wa of the workpiece W and then emitted through the film of the processing liquid Lp and light L2 reflected by the outer surface Fa of the film of the processing liquid Lp, and a control device 100 configured to control the rotating holding unit 30, the processing liquid supply unit 40, the light-projecting unit, and the light-receiving unit. The control device 100 is configured to execute the following operations: supplying the processing liquid Lp to the surface Wa of the workpiece W by the processing liquid supply unit 40; irradiating light from the light projecting unit toward the irradiation points P1 to P3 during a rotation period during which the workpiece W, to which the processing liquid Lp has been supplied, is rotated by the rotating holder 30 so that a film of the processing liquid Lp is formed on the surface Wa of the workpiece W; acquiring a signal waveform indicating a periodic time change in the intensity of the reflected light Lc during the rotation period based on the reflected light Lc received by the light receiving unit; acquiring a feature amount (delta time Dt) at each of a plurality of times from the signal waveform; and calculating the thickness of the film of the processing liquid Lp after the rotation period based on the time change of the feature amount. The feature amount is defined as the time difference between an arbitrary one time and a time shifted by n periods from the arbitrary one time in the signal waveform. In this substrate processing system 1, it is possible to accurately estimate the film thickness based on the reflected light from the workpiece W, similar to the above-mentioned film thickness estimation method. [Explanation of symbols]

[0139] 1...substrate processing system, 2...coating and developing apparatus, U1...liquid processing unit, Lp...processing liquid, 30...rotation and holding section, 40...processing liquid supply section, 60...measurement section, 70A to 70C...light emitting and receiving devices, P1 to P3...irradiation points, 100...control device, 120...film thickness estimation section.

Claims

1. irradiating light toward an irradiation location set to overlap with the surface of the substrate during a rotation period in which the substrate having a treatment liquid supplied thereon is rotated so as to form a film of the treatment liquid on the surface of the substrate; receiving reflected light that is a combination of light that is reflected by the surface of the substrate and then emitted through the film of the processing liquid and light that is reflected by an outer surface of the film of the processing liquid, thereby acquiring a signal waveform that indicates a periodic time change in intensity of the reflected light during the rotation period; generating a normalized waveform from the signal waveform; acquiring a feature amount at each of a plurality of times from the normalized waveform; calculating a thickness of the film of the treatment liquid after the rotation period based on a time change of the characteristic amount; generating the normalized waveform includes generating the normalized waveform by normalizing the intensity of the signal waveform in units of a half cycle, where the half cycle is a period from an arbitrary extreme value to the next extreme value in the signal waveform; The feature amount is defined as a time difference between any one time point in the normalized waveform and a time point shifted by n (n is an integer equal to or greater than 1) periods from the any one time point.

2. 2. The method of estimating a film thickness according to claim 1, wherein the characteristic amount is defined as a time difference between an arbitrary time in the normalized waveform and a time shifted by one period from the arbitrary time.

3. Normalizing the intensity of the signal waveform in units of half cycles includes: For each half period, the parameters Ix, Imin, Imax, and In are respectively Ix: Intensity of the signal waveform at any time x included in the half cycle Imin: The minimum value of the signal waveform in the corresponding half cycle Imax: maximum value of the signal waveform in the corresponding half cycle In: Transform value of the intensity of the signal waveform at the time x calculating a conversion value In using Equation 1 when In=(Ix-Imin) / (Imax-Imin)...(1) 3. The method of claim 1, further comprising converting the signal waveform based on the conversion value In for each half period.

4. Calculating the thickness of the film of the treatment liquid includes: acquiring a state transition curve that represents a transition of a variable indicating a drying state of the film of the treatment liquid based on a time change of the feature amount; obtaining an estimated set time at which the value of the variable in the state transition curve reaches a predetermined trigger value; The film thickness estimating method according to any one of claims 1 to 3, comprising: calculating a thickness of the film of the treatment liquid based on a model equation previously constructed for estimating a thickness of the film of the treatment liquid and the evaluated solidification time.

5. A method for manufacturing a substrate having a treatment liquid supplied onto its surface, comprising: irradiating light toward an irradiation point set to overlap with a surface of the substrate during a rotation period during which the substrate is rotated so as to form a film of the treatment liquid on the surface of the substrate; receiving reflected light that is a combination of light that is reflected by the surface of the substrate and then emitted through the film of the processing liquid and light that is reflected by an outer surface of the film of the processing liquid, thereby acquiring a signal waveform that indicates a periodic time change in intensity of the reflected light during the rotation period; acquiring a feature amount at each of a plurality of times from the signal waveform; calculating a thickness of the film of the treatment liquid after the rotation period based on a time change of the characteristic amount; the feature amount is defined as a time difference between an arbitrary time in the signal waveform and a time shifted by n (n is an integer equal to or greater than 1) periods from the arbitrary time, Calculating the thickness of the film of the treatment liquid includes: acquiring a state transition curve that represents a transition of a variable indicating a drying state of the film of the treatment liquid based on a time change of the feature amount; obtaining an estimated set time at which the value of the variable in the state transition curve reaches a predetermined trigger value; A film thickness estimating method comprising: calculating a thickness of the film of the treatment liquid based on a model equation previously constructed for estimating a thickness of the film of the treatment liquid and the evaluated solidification time.

6. Further comprising constructing the model formula; Constructing the model formula includes: irradiating light toward the irradiation location during a first rotation period during which a first test substrate having the treatment liquid supplied onto its surface is rotated at a first rotation speed so as to form a film of the treatment liquid on the surface of the first test substrate; receiving a first reflected light obtained by combining light reflected from the surface of the first test substrate and then emitted through the film of the treatment liquid and light reflected from an outer surface of the film of the treatment liquid on the first test substrate, thereby acquiring a first signal waveform indicating a periodic time change in intensity of the first reflected light during the first rotation period; acquiring a first feature amount corresponding to the feature amount at each of a plurality of times from the first signal waveform; acquiring a first state transition curve that represents a transition of a first variable that indicates a dry state of the film of the treatment liquid on the surface of the first test substrate based on a time change of the first characteristic amount; obtaining a first solidification time at which the value of the first variable in the first state transition curve becomes the trigger value; obtaining a first measurement indicative of a thickness of the film of the treatment liquid formed on the first test substrate after the first rotation period; irradiating light toward the irradiation location during a second rotation period during which the second test substrate having the treatment liquid supplied onto its surface is rotated at a second rotation speed so as to form a film of the treatment liquid on the surface of the second test substrate; and receiving a second reflected light obtained by combining light that is reflected by the surface of the second test substrate and then emitted through the film of the treatment liquid and light that is reflected by the outer surface of the film of the treatment liquid on the second test substrate, thereby acquiring a second signal waveform that indicates a periodic time change in intensity of the second reflected light during the second rotation period; acquiring, from the second signal waveform, a second feature amount corresponding to the feature amount at each of a plurality of times; acquiring a second state transition curve that represents a transition of a second variable that indicates a dry state of the film of the treatment liquid on the surface of the second test substrate based on the time change of the second feature amount; obtaining a second solidification time at which the value of the second variable becomes the trigger value on the second state transition curve; obtaining a second measurement indicative of a thickness of the film of treatment liquid formed on the second test substrate after the second rotation period; and The method of claim 4 , further comprising: generating the model equation based on the first solidification time, the first measurement value, the second solidification time, and the second measurement value.

7. Further comprising constructing the model formula; Constructing the model formula includes: executing a predetermined test process for each of the plurality of test substrates while changing a set value of the rotation speed in a plurality of stages; generating the model formula based on an execution result of the test process; The test process includes: irradiating light toward the irradiation location during a test rotation period during which the test substrate having the treatment liquid supplied onto its surface is rotated at a set rotation speed for the test process so that a film of the treatment liquid is formed on the surface of the test substrate; and receiving a composite reflected light obtained by combining light that is reflected from the surface of the test substrate and then emitted through the film of the treatment liquid and light that is reflected from the outer surface of the film of the treatment liquid on the test substrate, thereby obtaining a test signal waveform that indicates a periodic time change in intensity of the composite reflected light during the test rotation period; acquiring corresponding feature quantities corresponding to the feature quantities at a plurality of times from the test signal waveform; obtaining a test transition curve representing a transition of a test variable indicating a drying state of the film of the treatment liquid on the surface of the test substrate based on a time change of the corresponding feature amount; obtaining a test set time at which the value of the test variable in the test progression curve becomes the trigger value; obtaining measurements indicative of a thickness of a film of the treatment liquid formed on the test substrate after the test spinning period; 6. The film thickness estimation method according to claim 4, wherein, when a trigger setting period is defined as a period during which a difference between a maximum value and a minimum value of a rate of decrease, which represents a decrease in film thickness per unit time of the film of the processing liquid, at a certain time point in the multiple test progress curves obtained by the test processes respectively performed on the multiple test substrates, is greater than a predetermined value, the trigger value is set to be included in a range between a maximum value and a minimum value of the test variable at any time point in the trigger setting period.

8. measuring a temperature at a predetermined position in a processing chamber for performing a process of forming a film of the processing liquid on the surface of the substrate; The film thickness estimating method according to any one of claims 4 to 7, further comprising: correcting a thickness of the film of the treatment liquid calculated using the model formula in accordance with a deviation between a measured value of the temperature at the predetermined position and a reference temperature.

9. A computer-readable storage medium storing a program for causing a substrate processing apparatus to execute the film thickness estimation method according to any one of claims 1 to 8.

10. a rotation holder configured to hold and rotate the substrate; a processing liquid supply unit configured to supply a processing liquid to a surface of the substrate held by the spin holder; a light projection unit configured to project light toward an irradiation location set to overlap with a surface of the substrate held by the rotating holder; a light receiving unit configured to receive reflected light obtained by combining light that is reflected by the surface of the substrate and then emitted through the film of the processing liquid and light that is reflected by an outer surface of the film of the processing liquid; a control unit configured to control the rotation holding unit, the processing liquid supply unit, the light projecting unit, and the light receiving unit, The control unit is supplying the processing liquid to a surface of the substrate by the processing liquid supply unit; irradiating light from the light projecting unit toward the irradiation location during a rotation period in which the substrate, to which the processing liquid has been supplied, is rotated by the rotary holder so that a film of the processing liquid is formed on the surface of the substrate; and acquiring a signal waveform indicating a periodic time change in intensity of the reflected light during the rotation period based on the reflected light received by the light receiving unit; generating a normalized waveform from the signal waveform; acquiring a feature amount at each of a plurality of times from the normalized waveform; and calculating a thickness of the film of the treatment liquid after the rotation period based on a time change of the characteristic amount. generating the normalized waveform includes generating the normalized waveform by normalizing the intensity of the signal waveform in units of a half cycle, where the half cycle is a period from an arbitrary extreme value to the next extreme value in the signal waveform; The feature amount is defined as a time difference between an arbitrary time in the normalized waveform and a time shifted by n (n is an integer equal to or greater than 1) periods from the arbitrary time.

11. A rotary holder configured to hold and rotate a substrate; a processing liquid supply unit configured to supply a processing liquid to a surface of the substrate held by the spin holder; a light projection unit configured to project light toward an irradiation location set to overlap with a surface of the substrate held by the rotating holder; a light receiving unit configured to receive reflected light obtained by combining light that is reflected by the surface of the substrate and then emitted through the film of the processing liquid and light that is reflected by an outer surface of the film of the processing liquid; a control unit configured to control the rotation holding unit, the processing liquid supply unit, the light projecting unit, and the light receiving unit, The control unit is supplying the processing liquid to a surface of the substrate by the processing liquid supply unit; irradiating light from the light projecting unit toward the irradiation location during a rotation period in which the substrate, to which the processing liquid has been supplied, is rotated by the rotary holder so that a film of the processing liquid is formed on the surface of the substrate; and acquiring a signal waveform indicating a periodic time change in intensity of the reflected light during the rotation period based on the reflected light received by the light receiving unit; acquiring a feature amount at each of a plurality of times from the signal waveform; and calculating a thickness of the film of the treatment liquid after the rotation period based on a time change of the characteristic amount. the feature amount is defined as a time difference between an arbitrary time in the signal waveform and a time shifted by n (n is an integer equal to or greater than 1) periods from the arbitrary time, Calculating the thickness of the film of the treatment liquid includes: acquiring a state transition curve that represents a transition of a variable indicating a drying state of the film of the treatment liquid based on a time change of the feature amount; obtaining an estimated set time at which the value of the variable in the state transition curve reaches a predetermined trigger value; A substrate processing apparatus comprising: a processing step of calculating a thickness of the film of the processing liquid based on a model equation previously constructed for estimating a thickness of the film of the processing liquid and the evaluated solidification time.

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