JP4698166B2 - Thin film forming method, film thickness measuring method and film thickness measuring apparatus - Google Patents

Description

  The present invention relates to a thin film forming method, a film thickness measuring method, and a film thickness measuring apparatus for forming a thin film while measuring the film thickness of the thin film formed on the substrate, and more particularly to irradiating the thin film formed on the substrate with light. The present invention relates to a thin film forming method, a film thickness measuring method, and a film thickness measuring apparatus for forming a thin film while measuring the thickness of the thin film by measuring the intensity of the reflected light or transmitted light.

  When the substrate on which the thin film is formed is irradiated with light of wavelength λ, when the reflected light or transmitted light (hereinafter referred to as “reflected light, etc.”) is measured, the intensity of the measured reflected light or the like is the optical property of the thin film. It is widely known that extreme values appear periodically as the film thickness nd increases (see FIG. 9). That is, when the refractive index of the thin film is n, it is known that extreme values such as reflected light periodically appear every time the optical film thickness nd of the formed thin film is an integral multiple of λ / 4. .

  In the conventional film thickness measurement technique, the film thickness of a thin film during film formation is measured using the extreme values that appear periodically (for example, Patent Document 1). FIG. 9 is an explanatory diagram for explaining a conventional film thickness measurement technique. In the prior art, as shown in FIG. 9, the difference between the average value of the intensity near the extreme value of the reflected light and the like after the start of vapor deposition and the intensity of the reflected light and the like at the time of non-deposition is represented by A, the pole of the reflected light, etc. By detecting that the difference between the intensity at an arbitrary point after passing the value and the average value of the intensity in the vicinity of the extreme value is B, and B / A shows the target value, the film thickness corresponding to the target value is obtained. Measuring.

  According to this conventional film thickness measurement technique, the arbitrary point is set at a place where a change in the amount of light such as reflected light is relatively large with respect to a change in film thickness, so that it is less susceptible to noise and is called B / A. Since the “ratio” is used, the film thickness does not change even if the refractive index of the film slightly changes.

Japanese Examined Patent Publication No. 57-24485 (page 1-4, FIG. 3)

  However, since the above-described conventional film thickness measurement technique uses an extreme value that periodically appears (every time the optical film thickness nd becomes λ / 4), the optical film thickness nd must be larger than λ / 4. The value of B / A cannot be detected. For this reason, there was a problem that the optical film thickness nd could not be measured accurately unless the range of nd> λ / 4. Thus, if the range of film thickness that can be measured with high accuracy is limited, a thin film having an optical film thickness nd smaller than λ / 4 cannot be stably produced, and the quality of the thin film as a product varies. Will occur. In addition, restrictions on the design of the thin film are increased, and the difficulty of designing the thin film increases.

For example, the type of optical thin film transmits only light of a certain wavelength lambda _u, there is a band-pass filter for reflecting the other wavelengths. In the formation of this band-pass filter, when it is necessary to detect a thin optical film thickness than lambda _{u /} 4, conventionally, in order to maintain measurement accuracy, different from the wavelength lambda _u (than the wavelength lambda _u The optical film thickness was detected using light having a wavelength λ _m . At this time, if the refractive index of the thin film differs between λ _u and λ _m (there is chromatic dispersion), this is one factor that causes a control error in detecting the optical film thickness.

The present invention has been made in view of the above problems, and an object of the present invention is to accurately measure the film thickness of the thin film smaller than λ / 4 when the wavelength of the irradiation light is λ. It is possible to provide a thin film forming method, a film thickness measuring method, and a film thickness measuring apparatus capable of forming a thin film while measuring a relatively thin film thickness .

According to the thin film forming method of claim 1 , the object is to irradiate the substrate on which the thin film is formed and measure the intensity of the measurement light that is reflected light or transmitted light of the thin film. In the thin film forming method of forming a thin film on the surface of the substrate while measuring the film thickness of the substrate, a light receiving amount R _t and a reference light amount are supplied while forming a thin film on the substrate by supplying a thin film raw material toward the substrate. When R _{0 is} a light amount change value ΔR _t , the light amount change value indicating the amount of change in the intensity of the measurement light is calculated as a light amount change value ΔR _t that is the difference between the relative light amount R _t / R ₀ changes over a certain period of time. change value calculation step of (e.g., step Sa1 described later) and the change of light intensity values calculated by said change value calculation step (e.g., [Delta] R t _below) whether turned to decrease from the increase or the amount of light Change value is increasing from decreasing trend An inflection point determination step (for example, step Sa2 to step Sa10 or step Sb2 to step Sb6 described later) for determining at least one of whether or not a change has occurred, and the light amount change value tends to decrease in the inflection point determination step or Based on the light amount change value (for example, ΔR _t described later) at the time point when it is determined that the trend has increased, or a reference for measuring the film thickness based on the light amount change value in the vicinity of the time point (for example, ΔR _t described later) An inflection point change value calculating step (for example, Step Sa11 and Step Sb7 to be described later) for determining an inflection point change value (for example, ΔRc described later) and the inflection point determined in the inflection point change value calculating step. Target light amount change for setting a target light amount change value (for example, ΔRg described later) that is a light amount change value when a thin film having a desired film thickness is formed based on a point change value (for example, ΔRc described later). A desired value is determined by determining a setting step (for example, step S5 described later) and that the light amount change value has reached the target light amount change value (for example, ΔRg described later) set in the target light amount change value setting step. A target film thickness detection step (for example, step S9 described later) for detecting that the film thickness has been formed, and the light amount change value is set in the target light amount change value setting step in the target film thickness detection step. By determining that the target light quantity change value has been reached , the problem is solved by including a stopping step (for example, step S10 described later) for stopping the supply of the film material toward the substrate .

Thus, in the present invention, the inflection point change value is determined based on whether or not the light amount change value ΔR _t which is the difference between the changes in the relative light amount R _t / R ₀ in a certain time has turned to a decreasing tendency or an increasing tendency. The target light quantity change value is determined based on the inflection point change value, and it is detected that the desired film thickness has been formed by determining that the light quantity change value has reached the target light quantity change value. ing. Since it can be determined whether the light quantity change value has turned to a decreasing trend or an increasing tendency even when the optical film thickness is small, the inflection point change value can also be determined at a stage where the optical film thickness is small. it can. Therefore, according to the present invention, it is possible to detect that a desired film thickness has been formed even when the film thickness is small.

According to the film thickness measuring method according to claim 5 , the problem is that the substrate on which the thin film is formed is irradiated with light, and the intensity of measurement light that is reflected light or transmitted light is measured. In the film thickness measurement method for measuring the film thickness of the thin film, when the received light amount R _t , the reference light amount R ₀ , and the light amount change value ΔR _t , the light amount change value indicating the amount of change in the intensity of the measurement light is set for a certain time A change value calculation step of calculating as a light amount change value ΔR _t which is a difference in change of the relative light amount R _t / R _{0 at} the time, and whether or not the light amount change value calculated in the change value calculation step has changed from an increasing tendency to a decreasing tendency Or an inflection point determination step for determining at least one of whether or not the light quantity change value has changed from a decreasing tendency to an increasing tendency, and the light quantity change value tends to decrease or increase in the inflection point determination process. The light amount change value at the time when it is determined to have turned, Alternatively, based on the light amount change value in the vicinity of the time point, an inflection point change value calculation step for determining an inflection point change value serving as a reference for measuring the film thickness, and the inflection point change value calculation step determined in the inflection point change value calculation step This is solved by performing a film thickness detection step (for example, Step S8 and Step S9 described later) for detecting the film thickness based on the inflection point change value and the light amount change value .
Further , according to the film thickness measuring apparatus of claim 9 , the object is to irradiate the substrate on which the thin film is formed and measure the intensity of the measurement light which is reflected light or transmitted light of the light. In the film thickness measuring device for measuring the film thickness of the thin film, when the received light amount R _t , the reference light amount R ₀ , and the light amount change value ΔR _t , the light amount change value representing the change amount of the intensity of the measurement light is constant. Change value calculation means for calculating a light amount change value ΔR _t that is a difference in change of the relative light amount R _t / R _{0 over} time, and whether the light amount change value calculated in the change value calculation step has changed from an increasing tendency to a decreasing tendency Inflection point determining means for determining at least one of whether or not the light quantity change value has changed from a decreasing tendency to an increasing tendency, and the light quantity change value in the inflection point determining step is decreasing or increasing The light intensity change value at the time of determining that Or an inflection point change value calculating means for determining an inflection point change value serving as a reference for measuring the film thickness based on the light amount change value in the vicinity of the time point, and the inflection point change value calculating step This is solved by including a film thickness detecting means for detecting the film thickness based on the inflection point change value and the light amount change value .

Thus, in the present invention, the inflection point change value is determined based on whether or not the light amount change value ΔR _t which is the difference between the changes in the relative light amount R _t / R ₀ in a certain time has turned to a decreasing tendency or an increasing tendency. And the film thickness is detected based on the inflection point change value. Since it can be determined whether the light quantity change value has turned to a decreasing trend or an increasing tendency even when the optical film thickness is small, the inflection point change value can also be determined at a stage where the optical film thickness is small. it can. Therefore, according to the present invention, the film thickness can be accurately measured even when the film thickness is small.

The thin film formation method according to claim 1, wherein the change value calculation step and the inflection point determination step are performed a plurality of times at predetermined time intervals, and the light amount change value tends to decrease in the inflection point determination step. Based on counting the number of times determined to be present or the number of times determined to be increasing, and determining whether or not the counted number has reached a predetermined number, the light quantity change value decreases from the increasing tendency. It is preferable to determine whether or not the tendency has changed or whether or not the light quantity change value has changed from a decreasing tendency to an increasing tendency.
The film thickness measurement method according to claim 5, wherein the change value calculation step and the inflection point determination step are performed a plurality of times at predetermined time intervals, and the light amount change value decreases in the inflection point determination step. Based on counting the number of times determined to be trending or the number of times determined to be increasing and determining whether the counted number has reached a predetermined number, the light quantity change value is It is preferable to determine whether or not the light quantity change value has changed to a decreasing tendency or whether or not the light quantity change value has changed from a decreasing tendency to an increasing tendency.
The film thickness measurement apparatus according to claim 9, wherein the change value calculation unit and the inflection point determination unit perform calculation of the light amount change value a plurality of times at a predetermined time interval, and the inflection point determination unit. Is based on counting the number of times the light quantity change value is determined to be decreasing or the number of times determined to be increasing, and determining whether the counted number has reached a predetermined number, It is preferable to determine whether or not the light quantity change value has changed from an increasing tendency to a decreasing tendency, or whether or not the light quantity change value has changed from a decreasing tendency to an increasing tendency.

  With this configuration, even when there is noise in the intensity change of the measurement light, it is possible to determine an appropriate inflection point change value with less influence of noise.

The thin film formation method according to claim 1, wherein the change value calculation step and the inflection point determination step are performed a plurality of times at predetermined time intervals, and the light amount change value tends to decrease in the inflection point determination step. Based on counting the number of times determined continuously multiple times or the number of times determined consecutively if there is a tendency to increase, and determining whether the counted number has reached a predetermined number It is preferable to determine whether the light quantity change value has changed from an increasing tendency to a decreasing tendency, or whether the light quantity change value has changed from a decreasing tendency to an increasing tendency.
The film thickness measurement method according to claim 5, wherein the change value calculation step and the inflection point determination step are performed a plurality of times at predetermined time intervals, and the light amount change value decreases in the inflection point determination step. Based on counting the number of times determined consecutively when there is a tendency or the number of times determined consecutively when increasing, and determining whether the counted number has reached a predetermined number Thus, it is preferable to determine whether or not the light quantity change value has changed from an increasing tendency to a decreasing tendency, or whether or not the light quantity change value has changed from a decreasing tendency to an increasing tendency.
The film thickness measurement apparatus according to claim 9, wherein the change value calculation unit and the inflection point determination unit perform calculation of the light amount change value a plurality of times at a predetermined time interval, and the inflection point determination unit. Counts the number of times that the light quantity change value has been determined to be decreasing a plurality of times or the number of times that it has been determined to be an increase tendency, and whether the counted number has reached a predetermined number It is preferable to determine whether or not the light quantity change value has changed from an increasing tendency to a decreasing tendency, or whether or not the light quantity change value has changed from a decreasing tendency to an increasing tendency, based on the determination.

  With this configuration, even when there is noise in the intensity change of the measurement light, it is possible to determine an appropriate inflection point change value with less influence of noise.

The thin film formation method according to claim 1, wherein the change value calculation step and the inflection point determination step are performed a plurality of times at predetermined time intervals, and the light amount change value tends to decrease in the inflection point determination step. Whether or not the light quantity change value has changed from an increasing tendency to a decreasing tendency, based on whether or not it has been determined at a predetermined frequency, or whether or not it has been determined to have an increasing tendency, or It is preferable to determine whether or not the light quantity change value has changed from a decreasing tendency to an increasing tendency.
The film thickness measurement method according to claim 5, wherein the change value calculation step and the inflection point determination step are performed a plurality of times at predetermined time intervals, and the light amount change value decreases in the inflection point determination step. Whether or not the light quantity change value has changed from an increasing tendency to a decreasing tendency, based on whether or not it has been determined to be in a predetermined frequency, or whether or not it has been determined to be in an increasing trend, or It is preferable to determine whether or not the light quantity change value has changed from a decreasing tendency to an increasing tendency.
The film thickness measurement apparatus according to claim 9, wherein the change value calculation unit and the inflection point determination unit perform calculation of the light amount change value a plurality of times at a predetermined time interval, and the inflection point determination unit. The light amount change value decreases from the increasing tendency based on whether it is determined at a predetermined frequency that the light amount change value is decreasing or whether it is determined at a predetermined frequency that it is increasing. It is preferable to determine whether or not the tendency has changed or whether or not the light quantity change value has changed from a decreasing tendency to an increasing tendency.

  With this configuration, even when there is noise in the intensity change of the measurement light, it is possible to determine an appropriate inflection point change value with less influence of noise.

As described above, according to the film thickness forming method of the present invention, when the wavelength of the irradiation light is λ , the film thickness is measured to obtain a desired film thickness even when the film thickness is smaller than λ / 4 . A thin film can be formed.
In addition, according to the film thickness measuring method and film thickness measuring apparatus of the present invention, the film thickness of the thin film is smaller than λ / 4, where the wavelength of the irradiation light formed on the substrate is λ. The thickness can be measured.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The members, arrangements, and the like described below are not intended to limit the present invention and can be variously modified within the scope of the gist of the present invention.

FIG. 1 is a schematic view when the film thickness measuring apparatus of this embodiment is used in the film forming apparatus of this embodiment. FIG. 2 is a flowchart of the film thickness control process in the present embodiment. FIG. 3 is a flowchart of the inflection point determination process of the present embodiment performed in the film thickness process of FIG. FIG. 4 shows an example of a film control data table that stores film thickness control data. FIG. 5 is a graph showing the relationship between the film formation time t and the relative light amount R _t / R _{0 and} the relationship between the film formation time t and the light amount change value ΔR _t based on the film control data table shown in FIG. Is. FIG. 6 is a graph showing a reference curve of reflected light intensity when light having a wavelength λ is irradiated onto a substrate on which a thin film is formed.

  As shown in FIG. 1, in this embodiment, the vapor deposition apparatus 100 which forms a thin film by vapor deposition is used as a film-forming apparatus. The vapor deposition apparatus 100 includes a vacuum chamber 1, a substrate holder 2, a vapor deposition source 3, a shutter 5, and a vacuum pump 6.

  The vacuum chamber 1 is a stainless steel container that is usually used in a known vapor deposition apparatus, and has a substantially rectangular parallelepiped shape. The vacuum chamber 1 is provided with an exhaust port 1a for exhaust, and a vacuum pump 6 is connected through the exhaust port 1a. The inside of the vacuum chamber 1 is depressurized by operating the vacuum pump 6 to be in a vacuum state. The vacuum chamber 1 has an opening 1b for monitoring the thickness of the thin film to be formed at the center of the ceiling of the vacuum chamber. The opening 1b is sealed with a transparent lid 1c formed of quartz glass or the like, and is kept airtight.

  The substrate holder 2 is for holding a substrate on which a thin film is to be formed, and the substrate holder 2 of this embodiment has a dome shape. A plurality of substrates S are arranged on the inner surface of the dome-shaped base holder 2. Although the shape of the board | substrate S is not specifically limited, In this embodiment, the plate-shaped thing is used. As the substrate S, a substrate having a shape such as an optical lens can be used. The substrate S is held by the base holder 2 with a jig or bolt so as to face the vapor deposition source 3 disposed on the bottom surface of the vacuum chamber 1.

The substrate holder 2, similarly to the substrate S, a monitor substrate S ₀ is held by the jig and bolts. Similarly to the substrate S, the monitor substrate S _{0 is} also held by the substrate holder 2 so as to face the vapor deposition source 3 disposed on the bottom surface of the vacuum chamber 1. In the present embodiment, the center in the through hole of provided substrate holder 2, the monitor substrate S ₀ so as to close the through hole is held. The material of the monitor substrate S ₀ is not particularly limited, as a material whose refractive index is known, it is possible to use silicon dioxide. In the present embodiment, B270 manufactured by Schott Corporation, commonly called white plate glass, is used.
The substrate S and monitor substrate S ₀ is equivalent to the substrate of the present invention. It is also possible to use the same as the substrate S as a monitor substrate S _0.

  The vapor deposition source 3 is provided on the bottom surface of the vacuum chamber 1. The vapor deposition source 3 of the present embodiment is an electron beam vapor deposition source, and includes a crucible 3a for holding a thin film raw material and an electron gun 3b for generating an electron beam for irradiating the raw material filled in the crucible 3a. Yes. The vapor deposition raw material is evaporated by irradiating the vapor deposition raw material filled in the water-cooled crucible 3a with an electron beam.

An electron gun power source 4 is connected to the electron gun 3b. By supplying electric power to the electron gun 3b by the electron gun power source 4, an electron beam is generated from the electron gun 3b, and the evaporation material in the crucible 3a is heated by this electron beam. Material evaporant is vaporized substances heated deposition material diffuses into the vacuum vessel 1 as a raw material of a thin film, a part or the substrate S held on the substrate holder 2 is supplied to the monitor substrate S _0, substrate S and, adhering to the surface of the monitor substrate S ₀ to form a thin film.

  The shutter 5 includes a shutter plate 5a, a rotating rod 5b, and a shutter drive motor 5c. The shutter plate 5a is a plate-like member having a size that covers the vapor deposition source 3 (the crucible 3a). A rotating rod 5b is connected to the shutter plate 5a. The rotating rod 5b is pivotally supported on the bottom surface of the vacuum chamber 1, and is connected to the shutter drive motor 5c. By driving the shutter drive motor 5c, the rotating rod 5b rotates, and the shutter plate 5a has a position where the upper part of the vapor deposition source 3 (the crucible 3a) is covered and a position where it is not covered as the rotating rod 5b rotates. To move between.

When the shutter plate 5a is in a position not to cover the upper part of the deposition source 3 (crucible 3a) is a raw material vaporized material evaporated from the crucible 3a, can be supplied to the substrate S and monitor substrate S _0. That is, when the shutter plate 5a is in a position that does not cover the upper part of the vapor deposition source 3 (the crucible 3a), film formation can be performed. When the shutter plate 5a is at the top of the cover position of the deposition source 3 (crucible 3a) is a raw material vaporized material evaporated from the crucible 3a, it can not be supplied to the substrate S and monitor substrate S _0. That is, when the shutter plate 5a is at a position covering the upper part of the vapor deposition source 3 (the crucible 3a), film formation cannot be performed.

  The film thickness measurement apparatus of this embodiment includes a projector 21, a light receiver 22, a light-projecting side mirror 23, a light-receiving side mirror 24, an A / D converter 25, and a control means 30. Yes. The light projector 21 includes a light source that emits laser light or white light, and the light receiver 22 includes a photodiode or a phototube. The light projecting side mirror 23 and the light receiving side mirror 24 are mirrors that reflect the laser or white light emitted from the light projector 21.

The projection-side mirror 23 is installed at an angle that reflects the laser light or white light emitted from the projector 21 to the monitor substrate S ₀ in the vacuum chamber 1. The light-receiving side mirror 24 is installed at an angle that reflects laser light or white light reflected by the monitor substrate S ₀ or a thin film formed on the surface of the monitor substrate S ₀ toward the light receiver 22.

Laser light or white light emitted from the projector 21 is incident on the monitor substrate S ₀ in the vacuum chamber 1 through the projector-side mirror 23 and the lid 1c. Laser light or white light is reflected by the monitor substrate S ₀ or a thin film formed on the surface of the monitor substrate S ₀ , and is received by the light receiver 22 via the lid 1 c and the light receiving side mirror 24. The light receiver 22 outputs an electrical signal corresponding to the intensity of the received light. When white light is used as the light source by the projector 21, the light receiver 22 is provided with a wavelength selection function (such as a filter) so that light of a selected wavelength is selectively received.

Here, the light received by the light receiver 22 will be described. Upon irradiation to monitor substrate S ₀ on which a thin film is formed of light of wavelength λ on the surface, and reflected light from the reflecting light and monitor substrate S ₀ from the film surface cause interference by the phase difference therebetween. The refractive index and optical film thickness of the thin film influence this phase difference. Therefore, the intensity of the reflected light received by the light receiver 22 varies depending on the refractive index and the optical film thickness of the thin film. In the present embodiment, the optical film thickness of the thin film formed is measured and controlled based on the intensity of the light received by the light receiver 22 in this way. In the present embodiment, although by receiving the light reflected by the monitor substrate S _0, etc. and controls the optical thickness of the thin film, it is also possible to control the thickness of the thin film by receiving the transmitted light. In addition, since the optical film thickness is the product of the refractive index and the geometric film thickness of the thin film, if the optical film thickness is known, the geometric film thickness of the thin film whose refractive index is known can be known. It is also possible to measure and control the geometric film thickness. Therefore, also in the following description, the geometric film thickness can be calculated by dividing the optical film thickness by the refractive index.

  The A-D converter 25 is electrically connected to the light receiver 22, converts the electrical signal output from the light receiver 22 into a digital signal, and outputs the digital signal. The A / D converter 25 is electrically connected to the control unit 30, and the digital signal output from the A / D converter 25 is input to the control unit 30.

  The control unit 30 includes a control unit 31 that performs various controls and a storage unit 32 such as a hard disk or a semiconductor memory. The control means 30 corresponds to the change value calculation means, the inflection point determination means, the inflection point change value calculation means, and the film thickness detection means of the present invention.

  The control unit 31 includes an input unit that receives an input of a digital signal or the like from the A / D converter 25, a CPU (Central Processing Unit), a RAM that stores information as required by the operation of the CPU, and a shutter drive. A motor driver for controlling the motor 5c is provided. In addition, in order for an operator to give the instruction | indication to the control part 31, the keyboard etc. for inputting the instruction | indication to the control part 31 are connected to the control part 31, and the control part 31 receives the instruction | indication from an operator from an input means. The storage means 32 stores processing performed by the control unit 31, for example, an operation program for film thickness control processing described later, film thickness control data described later, and the like.

  The control means 30 receives a digital signal input from the A-D converter 25. Further, the digital signal from the A / D converter 25 is processed, and film thickness control data described later is stored in the storage means 32. Further, a film thickness control process described later is performed based on the film thickness control data, and a control signal is output to the shutter drive motor 5c.

Using the film thickness measuring apparatus of the present embodiment described above, the optical film thickness of the thin film formed by the vapor deposition apparatus 100 is measured, and the thin film having a desired optical film thickness is applied to the substrate (substrate S or monitor substrate S). _The method for forming the surface of ₀ ) will be described below.

First, the raw material of the thin film formed in the crucible 3a is filled. In this embodiment, a Ta ₂ O ₅ thin film was prepared using Ta ₂ O ₅ as a raw material. Note that the raw material and the type of thin film to be formed are not limited thereto. The substrate holder 2, to hold the substrate S and monitor substrate S _0, placing the substrate holder 2 in the vacuum chamber 1. In this state, the vacuum pump 6 is operated to reduce the pressure inside the vacuum chamber 1 to a predetermined pressure. For example, the pressure is reduced to about 1 × 10 ⁻³ Pa or less. At this stage, the shutter plate 5a is in a position covering the upper part of the vapor deposition source 3 (the crucible 3a).

When the inside of the vacuum chamber 1 is stabilized at the predetermined pressure, power supply to the electron gun 3b is started by the electron gun power source 4. Next, when the operator gives an instruction to start film formation to the control unit 31, the control unit 31 outputs a control signal to the shutter drive motor 5c, drives the shutter drive motor 5c, and moves the shutter plate 5a. Then, the upper part of the evaporation source 3 (the crucible 3a) is moved to a position where it is not covered. Thus, supply of the raw material evaporant onto the substrate S and monitor substrate S ₀ is started, the formation of a thin film (deposition) is started. Thereafter, during the formation of the thin film, laser light or white light continues to be emitted from the projector 21, continues to be received by the light receiver 22, and a digital signal can be input to the control unit 31 via the A / D converter 25. . The formation of the thin film is continued until step S10 described later is performed.
In the present embodiment, the control unit 31 starts the film thickness control process shown in FIGS. 2 and 3 in response to an instruction for starting film formation to the control unit 31 by the operator.

  2 and 3 are flowcharts of the film thickness control process in the present embodiment. FIG. 3 is a flowchart of the inflection point determination process of the present embodiment performed in the film thickness process of FIG. Hereinafter, the film thickness control process of the present embodiment performed by the control unit 31 will be described with reference to FIGS.

First, in step S1, initialization is performed. In the initialization, the value of the increase / decrease counter Lid is set to “0”, the value of the decrease / increase counter Ldi is set to “0”, and the inflection point flag is reset (set to “0”). The increase / decrease counter Lid, decrease / increase counter Ldi, and inflection point flag are stored in the RAM of the control means 30. The increase / decrease counter Lid, decrease / increase counter Ldi, and inflection point flag will be described later (see step Sa2 to step Sa11). In the initialization in step S1, the current received light amount R of the light receiver 22 is measured based on the digital signal input from the A-D converter 25. The measured received light amount is stored as a reference light amount _{R0 in} a storage area for storing the reference light amount of the RAM. Furthermore, measurement of the film formation time t is started. Note that the processing of step S1 is also performed when an initialization instruction is received from the operator during the following processing.

Subsequent to step S1, in step S2, measurement data is taken in. The measurement data is the film formation time t at the present time (current measurement point) and the received light amount R _t of the light receiver 22 at the current time. The amount of received light _Rt is a value measured based on a digital signal input from the A / D converter 25 and represents the intensity of measurement light that is light received by the light receiver 22. In the present embodiment, is set measurement points every T ₀ sec, the deposition time t executes the step S2 each time the elapsed T ₀ seconds, incorporation of measurement data. The measurement data acquired in step S2 is temporarily stored in an area for storing the measurement data in the RAM. The value of T ₀ (measurement point interval) is a value that is arbitrarily set by the operator in advance for the control means 30 and is stored in the storage means 32. Since the value of T ₀ is preferably to set a sufficiently long time for time to process step S1~ step S4, in this embodiment, to reduce the influence of noise on the received light amount R _t, data In order to reduce the amount and reduce the processing load on the control unit 31, T ₀ seconds = 2 seconds are set.

Subsequent to step S2, in step S3, an inflection point determination process is performed. Or inflection point determination process monitors the change in the amount of received light R _t in the light receiver 22, or the amount of change in the received light amount R _t change as the deposition time has elapsed is increasing, it is decreasing It is a process performed in order to determine such as.
FIG. 3 shows a flow of the inflection point determination process of the present embodiment. In the inflection point determination process of the present embodiment, the following steps Sa1 to Sa11 are performed.

In step Sa1, based on the film formation time t, the received light amount R _t , the reference light amount R ₀ stored in the RAM, the measurement interval T ₀ stored in the storage means 32, and the past film thickness control data. The relative light amount R _t / R ₀ , the light amount change value ΔR _t , and the second-order light amount change value Δ ² R _t at the measurement point are calculated. The calculated relative light amount R _t / R ₀ , light amount change value ΔR _t , and second-order light amount change value Δ ² R _t are stored in the storage unit 32 as film thickness control data along with the film formation time t stored in the RAM. save. The change value calculation process of the present invention is performed by the processing of step Sa1.

The value of the relative light quantity R _t / R ₀ relatively represents the intensity of the measurement light received by the light receiver 22 and is calculated by multiplying the value obtained by dividing R _t by R ₀ by 100. Therefore, the unit is%.
The value of the light amount change value ΔR _{t is} a value representing the change amount of the received light amount R _t that changes as the film formation time elapses, that is, the change amount of the intensity of the measurement light. In the present embodiment, the following value is adopted as the light amount change value ΔR _t .
That is, the average value of the relative light amount R _t / R ₀ at each measurement point from the film formation time (t−T ₁ ) seconds to t seconds is expressed as R _t / R ₀ Ave (t), and the film formation time (t The average value of the relative light quantity R _t / R ₀ at each measurement point from −T ₀ −T ₁ ) seconds to (t−T ₀ ) seconds is expressed as R _t / R ₀ Ave (t−T ₀ ), The light quantity change value ΔR _t is defined by the following (formula 1).

Note that the value of T _{1 is} a value that the operator arbitrarily sets in advance for the control means 30 and is stored in the storage means 32. In the present embodiment, is set as ₁ second = 10 seconds T in order to reduce the influence of noise such as the received light amount R _t in the light receiver 22.

The value of the second-floor light amount change value Δ ² R _t determines whether the light amount change value ΔR _t that is a change amount of the received light amount R _t that changes as the film formation time elapses is increasing or decreasing. It is a value that is an element to do. In the present embodiment, the following values are adopted as Δ ² R _t .
That is, the light amount change value ΔR _t at t seconds is _expressed as ΔR _t (t), and the light amount change value ΔR _t at (t−T ₀ ) seconds is _expressed as ΔR _t (t−T ₀ ). The change value Δ ² R _t is defined by the following (formula 2).

The sign of the second-order light quantity change value Δ ² R _t defined by (Equation 2) is an element for determining whether the light quantity change value ΔR _t is increasing or decreasing.

In step Sa1, these film thickness control data are added and stored in the film control data table 32a of the storage means 32 as film thickness control data for the film formation time t (current measurement point).
FIG. 4 shows an example of a film control data table 32a that stores film thickness control data. Each value in FIG. 4 represents film thickness control data in an experiment in which a thin film was formed by the above-described vapor deposition apparatus 100. In this experiment, the light amount of light having a wavelength λ = 550 nm is measured by the light receiver 22. The formed thin film is Ta ₂ O ₅ and its refractive index is 2.225. The film formation rate was 0.25 nm / sec.

FIG. 5 is a graph showing the relationship between the film formation time t and the relative light amount R _t / R _{0 and} the relationship between the film formation time t and the light amount change value ΔR _t based on the film control data table 32a shown in FIG. It is a thing. In FIG. 5, the left vertical axis represents the relative light quantity R _t / R ₀ , the right vertical axis represents the light quantity change value ΔR _t , and the horizontal axis represents the film formation time t. In FIG. 5, if the value of the horizontal axis is multiplied by the film formation rate of the thin film to be formed (thickness of the thin film formed per unit time) and the refractive index of the thin film, it becomes equal to the optical film thickness. .

Subsequent to step Sa1, in step Sa2, it is determined whether or not the value of the increase / decrease counter Lid is “0”. If it is determined in step Sa2 that the value of the increase / decrease counter Lid is not "0", the process proceeds to step Sa3, and if it is determined that the value of the increase / decrease counter Lid is "0", the process proceeds to step Sa7.
In step Sa3, it is determined whether or not the value of the second floor light quantity change value Δ ² R _t is “0” or more. If it is determined in step Sa3 that the value of the second-floor light amount change value Δ ² R _t is “0” or more, the process proceeds to step Sa4, and if the value of the second-floor light amount change value Δ ² R _t is smaller than “0”. If determined, the process proceeds to step Sa5.

In step Sa4, the value of the increase / decrease counter Lid is set to “0” and the value of the decrease / increase counter Ldi is set to “+1”, and the process proceeds from the inflection point determination process to step S4 (FIG. 2).
In step Sa5, the value of the increase / decrease counter Lid is incremented by "+1", and the process proceeds to step Sa6.
In step Sa6, the value of the increase or decrease the counter Lid it is determined whether an _{L 0.} If it is determined in step Sa6 that the value of the increase / decrease counter Lid is L ₀ , the process proceeds to step Sa11, and if it is determined that the value of the increase / decrease counter Lid is not L ₀ , the inflection point determination process starts with step S4 (FIG. 2). ) The value of L _{0 is} a value preset by the operator for the control unit 30 and is stored in the storage unit 32. In the present embodiment, the value of L ₀ is set to “3”.

In step Sa7, it is determined whether or not the value of the second-order light amount change value Δ ² R _t is “0” or more. If it is determined in step Sa7 that the value of the second floor light quantity change value Δ ² R _t is equal to or greater than “0”, the process proceeds to step Sa9, and if the value of the second floor light quantity change value Δ ² R _t is smaller than “0”. If determined, the process proceeds to step Sa8.

In step Sa8, the value of the increase / decrease counter Lid is incremented by "+1", the value of the decrease / increase counter Ldi is set to "0", and the process proceeds from the inflection point determination process to step S4 (FIG. 2).
In step Sa9, a process of “+1” is performed on the value of the decrease / increase counter Ldi, and the process proceeds to step Sa10.

In step Sa10, the value of the decrease and increase the counter Ldi it is determined whether an _{L 0.} If it is determined in step Sa10 that the value of the decrease / increase counter Ldi is L _0, the process proceeds to step Sa11, and if it is determined that the value of the decrease / increase counter Ldi is not L ₀ , the inflection point determination process starts with step S4 (FIG. Move to 2).

In the present embodiment, by performing more steps Sa2~ step Sa10, for each measurement point, the inflection point determination step of the present invention is carried out, or the light amount change value [Delta] R _t that is increasing, it is decreasing And the light quantity change value ΔR _t has changed from an increasing tendency to a decreasing tendency, or the light quantity change value ΔR _t has been changed from a decreasing tendency to an increasing tendency.

In other words, by performing the step Sa3 and step Sa7 at each measurement point, the light amount change value [Delta] R _t is determined whether to or decline on the increase at each measurement point. Then, the number of times that the light quantity change value ΔR _t is continuously determined to be decreasing at a plurality of measurement points is counted by the value of the increase / decrease counter Lid. In addition, the number of times that the light quantity change value ΔR _t is continuously determined to be increasing at a plurality of measurement points is counted by the value of the decrease counter Ldi. Further, the step Sa6, in step Sa10, the value of the increase or decrease counter Lid, the value of the decrease and increase counter Ldi, when it is determined that reaches _{L 0,} the light amount change value [Delta] R _t is turned to decrease from increase Therefore, it has been judged that the trend has shifted from a decreasing trend to an increasing trend. Then, when it is determined that the light quantity change value ΔR _t has changed from an increasing tendency to a decreasing tendency or from a decreasing tendency to an increasing tendency, the process proceeds to step Sa11.

  In step Sa11, the inflection point change value ΔRc is determined and the inflection point flag is set (set to “1”), and then the inflection point determination process proceeds to step S4 (FIG. 2). The inflection point change value ΔRc and the inflection point flag determined in step Sa11 are stored in the RAM of the control unit 31. By the process of step Sa11, the inflection point change value calculation step of the present invention is performed.

The inflection point change value ΔRc is a light amount change value ΔR _{t serving} as a reference for measuring the optical film thickness of the thin film. The inflection point flag indicates that the inflection point change value ΔRc has been determined.
Various methods for determining the inflection point change value ΔRc are conceivable. For example, the value and the light amount change value [Delta] R _t at which the light amount change value [Delta] R _t is determined to turned to decrease from increasing, light intensity change value when the light amount change value [Delta] R _t is determined to turned to increase from decrease the value of [Delta] R _t, or based on the value of the light amount change value [Delta] R _t of the time near, it is possible to determine the inflection point variation value .delta.rc.

In the present embodiment, the following method is used in consideration of the influence of noise such as the amount of light received by the light receiver 22. That is, the light amount change value ΔR _t at each measurement point from (t− (L ₀ −1) × T ₀ ) seconds to t seconds is read from the film control data table 32a of the storage unit 32, and the average value thereof is calculated. The inflection point change value ΔRc is used.

By performing the inflection point determination process described above for each measurement point, it is determined that the light amount change value ΔR _t has changed from an increasing tendency to a decreasing tendency, or has changed from a decreasing tendency to an increasing tendency. from the light amount change value [Delta] R _t time or near, determines the value of the inflection point changes value .delta.rc.

In particular, in the present embodiment, the inflection point change value ΔRc can be determined with less influence of noise for the following reason.
The digital signal input from the A / D converter 25 to the control unit 31 may include noise such as the amount of light received by the light receiver 22. When viewed at a measurement point within a short period, the sign of the second-order light amount change value Δ ² R _t indicating whether the light amount change value ΔR _t tends to increase or decrease may be replaced by noise. Therefore, in the present embodiment, in order to determine the inflection point change value ΔRc, the number of times that the value of the second-order light amount change value Δ ² R _t equal to or greater than “0” should be stored continuously, or less than “0”. In step Sa6 and step Sa10, the number of times that the second-order light quantity change value Δ ² R _t of the second stage should be stored continuously is defined as L ₀ . In this way, it is possible to appropriately determine the inflection point change value ΔRc while reducing the influence of noise on the positive and negative of Δ ² R _t . In the above-described embodiment, the value of L ₀ is set to “3” in order to reduce the influence of noise on the positive and negative of Δ ² R _t . However, the value of L ₀ is limited to “3”. Not something. Arbitrary integers can be set within a range in which the influence of noise separately on the positive and negative of Δ ² R _t can be reduced and the inflection point change value ΔRc can be appropriately determined.

After the inflection point determination process (step Sa1 to step Sa11) in step S3, step S4 (see FIG. 2) is performed.
In step S4, it is determined whether or not the inflection point flag is set. If it is determined in step S4 that the inflection point flag is set, the process proceeds to step S5. On the other hand, if it is determined in step S4 that the inflection point flag is not set, the process proceeds to step S2, and the processes of steps S2 and S3 are performed again for the next measurement point.

In step S5, a target light quantity change value ΔRg is set. By the processing of step S5, the target light quantity change value setting step of the present invention is performed. The target light amount change value ΔRg is a value that determines the light amount change value ΔR _t when a thin film having a target optical film thickness is formed. The value of the target light amount change value ΔRg is determined based on the inflection point change value ΔRc determined in step Sa11. The value of the target light amount change value ΔRg is calculated based on a preset calculation formula based on the inflection point change value ΔRc. This calculation formula is arbitrarily set in advance by the operator for the control means 30 and stored in the storage means 32. For example, it is defined as the following (Equation 3) and stored in the storage means 32.

  The value of k can be set according to the target optical film thickness. In the present embodiment, the substrate S on which a thin film is formed is based on a reference curve that represents the relationship between the optical film thickness x (= nd) and the reflected light intensity F (x) when light of wavelength λ is irradiated. Thus, k is determined by (Expression 5) described later. At this time, the reference curve may be derived from a predetermined calculation formula, or obtained from the result of a preliminary experiment in which the intensity of actual reflected light or the like was measured for a thin film having a known refractive index and film thickness. It can also be.

  In the present embodiment, the reference curve is obtained based on the following calculation formulas (Expression 4-1) to (Expression 4-4).

In the above formula, F (0) indicates the intensity of reflected light when the film thickness is 0, and an arbitrary value can be set. R ₁ is the reflectance when the incident measurement light is reflected by the surface of the monitor substrate S ₀ . r ₂ is the reflectance when the incident measurement light is reflected by the front and back surfaces of the monitor substrate S ₀ . n ₀ is the refractive index of the monitor substrate S ₀ . n is the refractive index of the thin film to be formed.

  FIG. 6 is a graph showing a reference curve as a relationship between reflected light intensity and optical film thickness. When the reflected light intensity is measured when the substrate S on which the thin film is formed is irradiated with light having a wavelength λ, as shown in FIG. 6, the measured reflected light intensity increases the geometric film thickness d of the thin film. In addition, it is widely known that the extreme value appears periodically. That is, assuming that the refractive index of the thin film is n, extreme values such as reflected light may periodically appear every time the optical film thickness x (= nd) of the formed thin film is an integral multiple of λ / 4. Are known.

The reference curve shown in FIG. 6A shows the relationship of the reflected light intensity F (x) to the optical film thickness x. In addition, the reference | standard curve shown in FIG. 6 is a curve based on the type | formula shown by the above-mentioned (Formula 4-1)-(Formula 4-4).
As shown in FIG. 6, f (x) shows a maximum at x = _{x 0.}
In this embodiment, the value of k is defined by the following (formula 5), where x = _xg is the target optical film thickness.

Subsequent to step S5, in step S6, measurement data is acquired in the same manner as in step S2, and the acquired measurement data (film formation time t, received light amount R _t ) is temporarily stored in an area for storing measurement data in the RAM. Remember.

Subsequent to step S6, in step S7, as in step Sa1, the film formation time t, the received light amount R _t , the reference light amount R ₀ stored in the RAM, and the measurement interval T ₀ stored in the storage unit 32 are stored. Based on the past film thickness control data (FIG. 4; values in the film control data table 32a), the relative light amount R _t / R ₀ , the light amount change value ΔR _t , and the second-order light amount change value Δ ² R _{t at the} current measurement point. Is calculated. Then, together with the film formation time t stored in the RAM, the calculated relative light amount R _t / R ₀ , light amount change value ΔR _t , second-order light amount change value Δ ² R _t are stored in the film control data table of the storage unit 32. 32a is stored as film thickness control data.

Subsequent to step S7, in step S8, the optical film thickness is calculated. That is, the inflection point variation value ΔRc determined in step Sa11, based on the amount change value [Delta] R _t in calculated in step S7, for sensing the optical thickness d _t of the thin film in the current measurement point. Specifically, in the present embodiment, the optical film thickness _dt is measured by the equation defined as (Equation 6) below.

That is, the left side f (d _t ) is obtained by substituting the inflection point change value ΔRc determined in step Sa11 and the light amount change value ΔR _t calculated in step S6 into the right side of (Expression 6). F (d _t ) calculated in (Expression 6) is defined as representing the value of the above-described function f (x) at the optical film thickness x = _dt, and f (d _t ) calculated in (Expression 6) ) To calculate the optical film thickness d _t (= x) based on the function f (x) (see FIGS. 5 and 6). That is, the inflection point variation value ΔRc determined in step Sa11, based on the ratio of the light amount change value [Delta] R _t in calculated in step S7, the measurement of optical thickness d _t of the thin film in the current measurement point.

Following step S8, in step S9, and the light amount change value [Delta] R _t has reached the target light amount change value [Delta] rg, determining whether the thin film of the optical film thickness of the target is formed. That is, it is determined whether or not the light amount change value ΔR _t calculated in step S6 is smaller than the target light amount change value ΔRg. If it is determined in step S9 that the light amount change value ΔR _t is smaller than the target light amount change value ΔRg and it is detected that a thin film having a target optical film thickness has been formed, the process proceeds to step S10. On the other hand, the light amount variation value [Delta] R _t in step S9 is, if it is determined not smaller than the value of the target light amount change value ΔRg proceeds to step S6, the next measurement point, the processing of step S6~ step S9 again Do. The film thickness detection process of the present invention is performed by the process of step S8 or step S9. In particular, the target film thickness detection process of the present invention is performed by the process of step S9.

If the inflection point change value ΔRc determined in step Sa11 is a negative value, step S9 is performed as follows. That is, if it is determined that the light quantity change value ΔR _t is greater than the target light quantity change value ΔRg, the process proceeds to step S10. If it is determined that the light quantity change value ΔRt is not greater than the target light quantity change value ΔRg, the process proceeds to step S6. The process of step S6 to step S9 is performed again for the next measurement point.

In step S10, a control signal is output to the shutter drive motor 5c so as to move the shutter plate 5a to a position covering the upper part of the vapor deposition source 3 (the crucible 3a). When a control signal is output to the shutter drive motor 5c in step S10, the shutter drive motor 5c is driven, and the shutter plate 5a moves to a position that covers the upper part of the vapor deposition source 3 (the crucible 3a). Thus, the raw material evaporant supplied to the substrate S and monitor substrate S ₀ is stopped, the formation of a thin film (deposition) is completed, it is possible to form a thin film of an optical film thickness of a target. The stop process of the present invention is performed by the process of step S10.

As described above, in this embodiment, in order to measure the optical film thickness, or to detect whether or not a thin film having a target optical film thickness is formed, the amount of change in the received light amount _Rt is set. is characterized in that focusing on the light amount change value [Delta] R _t shown. Change in relative light amount R _t / R ₀ with the passage of film formation time (increase in optical film thickness) and change in light amount change value ΔR _t with passage of film formation time (increase in optical film thickness) Are common in that the extreme values are periodically shown (see FIGS. 5 and 6) as the deposition time elapses (increase in the optical film thickness). However, as can be seen from FIG. 5 and FIG. 6, the light amount change value ΔR _t exhibits an extreme value at a time earlier than the relative light amount R _t / R ₀ (at a stage where the optical film thickness is thin).

When measuring whether or not a thin film having a target optical film thickness is formed with reference to the extreme value of the relative light quantity R _t / R ₀ as in the prior art, the optical film thickness is accurately measured. for, wait until the relative light intensity R _{t /} R ₀ is deposited showing the extreme time (optical thickness = lambda / 4), it had to be determined extreme values of the relative light amount R _{t /} R ₀ It was. In contrast, as in this embodiment, determining whether the thin film of the optical film thickness with respect to the inflection point variation value ΔRc corresponding to extrema of the light amount change value [Delta] R _t to the target is formed With this configuration, since the light amount change value ΔR _t exhibits an extreme value when the film formation time is short (when the optical film thickness is smaller than λ / 4), the optical film thickness is less than λ / 4. It becomes possible to accurately measure the optical film thickness at a small stage. Therefore, according to the present embodiment, a thin film having an optical film thickness smaller than λ / 4 can be stably produced with high accuracy. For this reason, it becomes possible to ease the restrictions of thin film design and reduce the difficulty of thin film design.

For example, in an optical thin film, there is a thin film (for example, a bandpass filter) in which the refractive index changes greatly depending on the wavelength (wavelength dispersion) and is used only for a specific wavelength. In this case, if the wavelength λ _u at which the thin film is used and the wavelength λ _{m of} the light used for measuring the film thickness are different, a film thickness measurement error occurs due to the influence of wavelength dispersion. According to the present embodiment, such an error can be avoided. That is, conventionally, when a film thickness thinner than λ _u / 4 is to be detected, the film thickness of λ _m / 4 is accurately detected by making the wavelength λ _{m of the} measurement light smaller than λ _u. Was. Therefore, there may also occur a measurement error due to the mismatch of the lambda _u and lambda _m. On the other hand, according to the present embodiment, a thin film thinner than λ _u / 4 can be detected with high accuracy while keeping the wavelength λ _{m of the} measurement light coincident with λ _u . Therefore, it is possible to avoid a measurement error due to a mismatch between λ _u and λ _m .

In short, the intensity of the reflected light or the like (relative light amount R _t / R ₀ ) that is measured generally shows a trigonometric curve with time change (an increase in the optical film thickness), and the optical film thickness nd is λ Every time it becomes / 4, it shows an extreme value periodically. The present invention has been made by paying attention to the fact that, when the intensity curve that changes approximately in the form of a trigonometric function is differentiated, the phase of the curve shifts to the short wavelength side (the smaller the optical film thickness). It is. That is, the gentle position of the change in the vicinity of the extreme value of the curve indicating the intensity has a value near 0 in the differential curve, and the position with a large change that is an intermediate position of the extreme value shows the maximum value or the minimum value in the differential curve.

  In the prior art, since an extreme value periodically appearing in a curve indicating the intensity of reflected light or the like to be measured is used, the value of B / A is set unless the optical film thickness nd is larger than λ / 4. It cannot be detected. In the present invention, attention is paid to the fact that a curve in which an extreme value appears with an optical film thickness smaller than λ / 4 can be obtained by differentiating a curve indicating the intensity of reflected light or the like to be measured. By detecting the optical film thickness using the extreme value appearing at an optical film thickness smaller than λ / 4, the optical film thickness that could not be performed conventionally unless the value was larger than λ / 4. Can be detected even with a thinner optical film thickness.

  By the way, in order to stop film formation quickly when a desired film thickness is formed, it is required that the control means 30 perform processing quickly. However, since the process of differentiating the curve indicating the intensity is a complicated process, the processing load of the control unit 30 increases and the process of the control unit 30 is delayed.

Therefore, in this embodiment, instead of differentiating the relative light amount R _{t /} R _0, determined by calculating the light amount change value [Delta] R _t is the difference between the change in the relative light amount R _{t /} R ₀ at a certain time, the amount of light Control based on the change value ΔR _t is performed. By controlling in this way, the processing of the control means 30 can be relatively simplified, and processing for quickly stopping film formation can be performed when a desired film thickness is formed.

  The embodiment described above can be modified, for example, as in the following (a) to (d).

(A) In the above-described embodiment, the light amount change value ΔR _t is defined as in (Expression 1), but the light amount change value of the present invention is not limited to (Expression 1) in the above embodiment. Can be defined in various ways. In short, a value indicating an extremum before the optical film thickness nd becomes λ / 4 with time change (increase in optical film thickness) is defined as a light amount change value indicating the amount of change in the intensity of measurement light. Just add. As the light amount change value indicating the change amount of the intensity of the measurement light, the following (a-1) and (a-2) can be defined in addition to the above-described embodiment, for example.

(A-1) The relative light amount R _t / R ₀ at the film formation time t seconds is expressed as R _t / R ₀ (t), and the relative light amount R _t / R ₀ at the film formation time (t−T ₀ ) seconds is _expressed as The light amount change value ΔR _t can also be defined by the following (formula 7), expressed as R _t / R ₀ (t−T ₀ ).

FIG. 7 is a graph showing the relationship between the film formation time t and the relative light amount R _t / R _{0 and} the relationship between the film formation time t and the light amount change value ΔR _t . In Figure 7, of the film thickness control data layer control data table 32a shown in FIG. 4, the value of the light amount change value [Delta] R _t calculated by equation (1), the light amount change value [Delta] R _t calculated by equation (7) It is replaced with the value of and graphed. Note that T ₀ seconds = 2 seconds and T ₁ seconds = 10 seconds.

As can be seen by comparing FIG. 5 showing the value of the light quantity change value ΔR _t calculated by (Equation 1) and FIG. 7 showing the value of the light quantity change value ΔR _t calculated by (Equation 7), better in the case of calculating the value of the light amount change value [Delta] R _t (equation 1), is smooth manner of change of the light amount change value [Delta] R _t than calculating the value of the light amount change value [Delta] R _t (equation 7) . Therefore, in order to reduce the influence of noise such as the amount of received light in the light receiver 22, it is preferable to define the light amount change value ΔR _t in (Equation 1) in the above-described embodiment.

  (A-2) In the embodiment described above, the light quantity change value of the present invention is defined by the above (Equation 1) in consideration of the processing load of the control means 30. However, when the processing capability of the control means 30 is high, or when it is not necessary to consider the influence of the processing load of the control means 30, the light quantity change value of the present invention can be defined as follows.

That is, the value of the light quantity change value ΔR _t can be a differential value of the relative light quantity R _t / R ₀ at the film formation time t seconds. Or, the value of the light amount change value [Delta] R _t, the relative amount of light _R t / _{R 0} from the average value of the differential value, at the film formation time _{(t-T 0)} seconds relative light amount _R t / _{R 0} in the deposition time t seconds It is also possible to use a value obtained by subtracting the average value of the differential values. In accordance with this, the value of the second-order light amount change value Δ ² R _{t in} the above embodiment can also be a second-order differential value of the relative light amount R _t / R _{0 at} the film formation time t seconds, or the film formation time. deposition time from the light amount change value [Delta] R _t in t seconds (t-T ₀₎ can also be a change in light quantity value [Delta] R _t the value obtained by subtracting the like in seconds.

(B) In the above-described embodiment, the average value of the light amount change value ΔR _t at each measurement point from (t− (L ₀ −1) × T ₀ ) seconds to t seconds is the inflection point change value ΔRc. . However, the method of determining the inflection point change value ΔRc is not limited to this. For example, the inflection point change value ΔRc can be determined as shown in the following (b-1) to (b-4). In any case, the inflection point change value ΔRc may be determined by a method capable of calculating an appropriate inflection point change value ΔRc while reducing the influence of noise as much as possible.

(B-1) The average value of the light amount change value ΔR _t at each measurement point in a predetermined period near t seconds, which is different from (t− (L ₀ −1) × T ₀ ) seconds to t seconds, is inflected. The point change value ΔRc can be used.
(B-2) (t− (L ₀ −1) × T ₀ ) The maximum selected from the light amount change value ΔR _t of each measurement point in the period from t to (sec) to t seconds and in other predetermined periods in the vicinity of t seconds The value or the minimum value can be used as the inflection point change value ΔRc.
(B-3) Maximum and minimum from the amount of light change ΔR _{t at} each measurement point in the period from (t− (L ₀ −1) × T ₀ ) seconds to t seconds and other predetermined periods in the vicinity of t seconds. except for the light amount change value [Delta] R _t, the average value of the remaining amount change value [Delta] R _t, may be an inflection point change value .delta.rc.
(B-4) (t− (L ₀ −1) × T ₀ ) selected from the light amount change value ΔR _t of each measurement point in a period from t to (seconds) to t seconds or in another predetermined period in the vicinity of t seconds. Any one light quantity change value ΔR _t can be used as the inflection point change value ΔRc.

(C) The inflection point determination process (FIG. 3) in the above-described embodiment can be modified as shown in FIG.
FIG. 8 shows a flow of inflection point determination processing according to an embodiment different from the above-described embodiment. In the inflection point determination process of FIG. 8, the following steps Sb1 to Sb7 are performed. In addition, in order to perform the inflection point determination process of FIG. 8, the processing content of step S1 (refer FIG. 2) in the above-mentioned embodiment is changed as follows.

In the initialization step S1, an initial value a negative value incidence Q _t (but not limited to, for example, "0") is set to the inflection point flag (set to "0") resetting. It will be described later negative value incidence _{Q t} (see step Sb2~ step Sb6). Further, the current received light amount R of the light receiver 22 is measured based on the digital signal input from the AD converter 25. The measured received light amount is stored as a reference light amount _{R0 in} a storage area for storing the reference light amount of the RAM. Furthermore, measurement of the film formation time t is started. Note that the processing of step S1 is also performed when an initialization instruction is received from the operator during the following processing.

In the inflection point determination process of FIG. 8, first, step Sb1 is performed. The process of step Sb1 is the same as that of step Sa1 in the above-described embodiment.
Following step Sb1, in step Sb2, or negative values incidence _{Q t} is less than _{Q 0,} determines whether _{Q 0} or more. The negative value appearance rate Q _t represents how often negative values are filed as the value of the second-order light amount change value Δ ² R _t .

The negative value appearance rate Q _t of this embodiment is a negative second-order light quantity change value Δ ² R at a frequency how many times at each of M measurement points from the film formation time (t−T ₁ ) seconds to t seconds. _It represents whether _t has appeared. If a negative second-order light quantity change value Δ ² R _t appears at a frequency of m times, the negative value appearance rate Q _t is defined by the following (formula 8).

In this case as well, as in the above-described embodiment, the value of T _{1 is} a value that the operator arbitrarily sets in advance for the control means 30 and is stored in the storage means 32. In the present embodiment, T ₁ second = 10 seconds is set in order to reduce the influence of noise such as the amount of received light in the light receiver 22.
In the present embodiment, it is determined from the value of the negative value appearance rate Q _t whether the light amount change value ΔR _t tends to increase or decrease.

In step Sb2, the value of the negative value incidence Q _t in the current measurement points the last time, or less than Q _0, it is determined whether the Q ₀ or more. The value of the negative value incidence _{Q t} at each measuring point, later step Sb3, is intended to be stored in the RAM in step Sb5.

If it is determined in step Sb2 that the negative value appearance rate Q _t is smaller than Q ₀ and the light amount change value ΔR _t tends to increase (Q <Q ₀ ), the process proceeds to step Sb3. On the other hand, in step Sb2, the value of the negative value incidence _{Q t} is _{Q 0} or more, when the light amount change value [Delta] R _t is determined that there is a decreasing tendency (Q ≧ _{Q 0),} the process proceeds to step Sb5. The Q ₀ value is a value that the operator arbitrarily sets in advance for the control means 30 and is stored in the storage means 32. In the present embodiment, as a value of the second-order light amount change value Δ ² R _t , a state where positive and negative appear in half is used as a criterion for determining whether or not the light amount change value ΔR _t tends to increase. Is set as Q ₀ = 0.5.

In step Sb3 and step Sb5, the negative value appearance rate Q _t at the current measurement point is calculated based on T ₁ stored in the storage unit 32 and the past film thickness control data (film control data table 32a). The calculated negative value appearance rate Q _t is stored in the RAM. Step Sb4 is performed following step Sb3, and step Sb6 is performed following step Sb5.

In step Sb4, it determines whether or not the value of the negative value incidence Q _t is less than Q _0. If it is determined in step Sb4 that the negative value appearance rate Q _t is smaller than Q ₀ and the light quantity change value ΔR _t is still in an increasing trend (Q <Q ₀ ), the inflection point determination process is executed. The process proceeds to S4 (FIG. 2). On the other hand, in step Sb4, it is determined that the negative value appearance rate Q _t is equal to or greater than Q ₀ (Q ≧ Q ₀ ), and the previous measurement point is increasing (in step Sb2, Q <Q ₀ When it is determined that the light amount change value ΔR _t has started to decrease, the process proceeds to step Sb7.

In step Sb6, it determines whether or not the value of the negative value incidence Q _t is less than Q _0. If it is determined in step Sb6 that the negative value appearance rate Q _t is equal to or greater than Q ₀ and the light quantity change value ΔR _t is still in a decreasing trend (Q ≧ Q ₀ ), the inflection point determination process is executed. The process proceeds to S4 (FIG. 2). On the other hand, in step Sb6, it is determined that the negative value appearance rate Q _t is smaller than Q ₀ (Q <Q ₀ ), and the previous measurement point has a decreasing tendency (in step Sb2, Q ≧ Q _0). When it is determined that the light amount change value ΔR _t has started to increase, the process proceeds to step Sb7.

In the present embodiment, by performing the above steps Sb2 to Sb6 for each measurement point, the inflection point determination step of the present invention is performed, and the light amount change value ΔR _t is increasing or decreasing. And the light quantity change value ΔR _t has changed from an increasing tendency to a decreasing tendency, or the light quantity change value ΔR _t has been changed from a decreasing tendency to an increasing tendency.

That is, by performing Step Sb4 and Step Sb6 at each measurement point, it is determined whether the light quantity change value ΔR _t tends to increase or decrease at each measurement point. Then, by determining that Q ≧ Q ₀ in step Sb4, it is determined that the light amount change value ΔR _t has changed from an increasing tendency to a decreasing tendency. Further, by determining that Q <Q ₀ in step Sb6, it is determined that the light amount change value ΔR _t has changed from a decreasing tendency to an increasing tendency. Then, when it is determined that the light amount change value ΔR _t has changed from an increasing tendency to a decreasing tendency or from a decreasing tendency to an increasing tendency, the process proceeds to step Sb7.

  In step Sb7, the inflection point change value ΔRc is determined and the inflection point flag is set (set to “1”), and then the inflection point determination process proceeds to step S4 (FIG. 2). The inflection point change value ΔRc and the inflection point flag determined in step Sb7 are stored in the RAM of the control unit 31. By the process of step Sb7, the inflection point change value calculation step of the present invention is performed.

Similar to the above embodiment, the inflection point changes value ΔRc is a value of the light amount change value [Delta] R _t as a reference for measuring the optical thickness of the thin film, the light amount change value [Delta] R _t is a decreasing tendency from increasing The value of the light amount change value ΔR _t at the time when it is determined to have changed, the value of the light amount change value ΔR _t at the time when it is determined that the light amount change value ΔR _t has changed from a decreasing tendency to an increasing tendency, or a light amount change value ΔR _t near that time point. It is a value determined based on the value of _t .

  Various methods for determining the inflection point change value ΔRc are conceivable, but it is preferable that the inflection point change value ΔRc is determined so that the influence of noise such as the amount of received light in the light receiver 22 is reduced. For example, it may be determined by the following methods (c-1) to (c-3).

(C-1) The light amount change value ΔR _t at each measurement point from (t−T ₂ ) second to (t−T ₃ ) second is read from the film control data table 32a of the storage means 32, and the average value thereof is read. Can be the inflection point change value ΔRc. In this case, values of T ₂ seconds and T ₃ seconds are arbitrary as long as an appropriate inflection point change value ΔRc can be calculated. For example, by setting T ₂ = T ₁ and T ₃ = 0, an appropriate inflection point change value ΔRc can be calculated. Also, an appropriate inflection point can be obtained by setting (t−T ₂ ) to (t−T ₃ ) seconds to be an intermediate period between (t−T ₁ ) seconds and t seconds. The change value ΔRc can be calculated.

(C-2) The light amount change value ΔR _t at each measurement point from (t−T ₂ ) seconds to (t−T ₃ ) seconds is read from the film control data table 32a of the storage means 32, and the maximum value is read from the values. and excluding the minimum light amount change value [Delta] R _t, the average value of the remaining amount change value [Delta] R _t, may be an inflection point change value .delta.rc. The values of T ₂ seconds and T ₃ seconds in this case are the same as in the case of (c-1).

(C-3) The light amount change value ΔR _t at each measurement point from (t−T ₂ ) second to (t−T ₃ ) second is read from the film control data table 32a of the storage means 32, and the maximum value thereof is read. The minimum value can be set as the inflection point change value ΔRc. The values of T ₂ seconds and T ₃ seconds in this case are the same as in the case of (c-1).

(C-4) The light quantity change value ΔR _t at each measurement point from (t−T ₂ ) seconds to (t−T ₃ ) seconds is read from the film control data table 32a of the storage means 32, and from among these, Any one selected light quantity change value ΔR _t can be used as the inflection point change value ΔRc. The values of T ₂ seconds and T ₃ seconds in this case are the same as in the case of (c-1).

As described above, in the inflection point determination process according to the embodiment of FIG. 8, whether or not the light amount change value ΔR _t tends to increase depending on whether or not the negative value appearance rate Q _t is smaller than Q _0. Therefore, the inflection point change value ΔRc when the light amount change value ΔR _t turns to a decreasing tendency or an increasing tendency is appropriately determined while reducing the influence of noise such as the amount of light received at the light receiver 22. can do.

  (D) In the above embodiment, an example in which a thin film was formed on the surface of the substrate S by vapor deposition using the vapor deposition apparatus 100 has been described. However, instead of the vapor deposition apparatus 100, other well-known PVD (physical) It is also possible to form a thin film on the surface of the substrate S with a film forming apparatus that performs vapor deposition or a film forming apparatus that performs chemical vapor deposition (CVD). In any case, as in the embodiment described above, the optical film thickness of the thin film is measured with a film thickness measuring device during film formation, and the thin film material for the substrate S is formed when the target optical film thickness is formed. Stop supplying.

  For example, when a film forming apparatus that performs sputtering is used, a shutter plate 5a that is driven between a position that shields between the sputtering target and the substrate S and a position that does not shield is provided, and the shutter plate 5a is driven. Then, the start (start of film formation) and end (end of film formation) supply of the thin film material to the substrate S are controlled. When a film forming apparatus that performs CVD is used, the control unit 31 controls the opening and closing of a control valve that controls the supply of a raw material gas that is a thin film raw material. The start and end of film formation (end of film formation) are controlled by the start and end of supply of the source gas.

It is the schematic explaining the film thickness measuring apparatus of this embodiment. It is a flowchart of the film thickness control process in this embodiment. It is a flowchart of the inflection point determination process of this embodiment performed by the film thickness process of FIG. 3 shows an example of a film control data table that stores film thickness control data. The relationship between the film formation time t and the relative light amount R _t / R _{0 and} the relationship between the film formation time t and the light amount change value ΔR _t are shown in a graph. It is a graph showing the reference | standard curve of reflected light intensity when the light of wavelength (lambda) is irradiated to the board | substrate with which the thin film is formed. In another embodiment, it illustrates the relationship between the deposition time t relative light amount R _{t /} R _0, and the relationship between the deposition time t and the light amount change value [Delta] R _t graphically. The flow of the inflection point determination process which concerns on another embodiment is shown. It is explanatory drawing explaining the conventional film thickness measurement technique.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum chamber 1a Exhaust port 1b Opening 1c Cover body 2 Base holder 3 Deposition source 3a Crucible 3b Electron gun 4 Electron gun power supply 5 Shutter 5a Shutter plate 5b Rotating rod 5c Shutter drive motor 6 Vacuum pump 21 Projector 22 Receiver 23 Projector side Mirror 24 Light receiving side mirror 25 AD converter 30 Control unit 31 Control unit 32 Storage unit 32a Film control data table 100 Deposition apparatus S Substrate S ₀ Monitor substrate

Claims (12)

A thin film is formed on the surface of the substrate while irradiating the substrate on which the thin film is formed and measuring the thickness of the thin film by measuring the intensity of measurement light that is reflected or transmitted light of the light. In the thin film forming method,
While forming a thin film on the base by supplying a thin film raw material toward the base,
When the received light amount R _t , the reference light amount R ₀ , and the light amount change value ΔR _t , the light amount change value indicating the amount of change in the intensity of the measurement light is a difference between changes in the relative light amount R _t / R ₀ over a certain time. A change value calculating step for calculating the light amount change value ΔR _t ;
An inflection point for determining at least one of whether or not the light quantity change value calculated in the change value calculation step has changed from an increasing tendency to a decreasing tendency, or whether or not the light quantity change value has changed from a decreasing tendency to an increasing tendency A determination process;
Based on the light amount change value at the time when it is determined that the light amount change value has turned to decrease or increase in the inflection point determination step, or a reference for measuring the film thickness based on the light amount change value in the vicinity of the time point An inflection point change value calculating step for determining an inflection point change value;
A target light amount change value setting step for setting a target light amount change value when a thin film having a desired film thickness is formed based on the inflection point change value determined in the inflection point change value calculation step;
Performing a target film thickness detection step of detecting that a desired film thickness has been formed by determining that the light amount change value has reached the target light amount change value set in the target light amount change value setting step. ,
Stopping the supply of the film material toward the substrate by determining that the light amount change value has reached the target light amount change value set in the target light amount change value setting step in the target film thickness detection step A method of forming a thin film comprising the steps. The change value calculation step and the inflection point determination step are performed a plurality of times at predetermined time intervals,
In the inflection point determination step, the number of times the light quantity change value is determined to be decreasing or the number of times determined to be increasing is counted, and it is determined whether or not the counted number has reached a predetermined number. The method according to claim 1, further comprising: determining whether the light quantity change value has changed from an increasing tendency to a decreasing tendency, or whether the light quantity change value has changed from a decreasing tendency to an increasing tendency. The thin film formation method of description. The change value calculation step and the inflection point determination step are performed a plurality of times at predetermined time intervals,
In the inflection point determination step, the number of times that the light quantity change value is determined to be decreasing is counted a plurality of times or the number of times that the light amount change value is determined to be increasing is determined to be a plurality of times. Based on determining whether or not the predetermined number has been reached, it is determined whether or not the light amount change value has changed from an increasing tendency to a decreasing tendency, or whether or not the light amount change value has changed from a decreasing tendency to an increasing tendency The thin film forming method according to claim 1, wherein: The change value calculation step and the inflection point determination step are performed a plurality of times at predetermined time intervals,
In the inflection point determination step, the light amount change value is determined based on whether the light amount change value is determined to be decreasing at a predetermined frequency or whether it is determined to be increasing at a predetermined frequency. 2. The thin film forming method according to claim 1, wherein it is determined whether or not the value has changed from an increasing tendency to a decreasing tendency, or whether or not the light quantity change value has changed from a decreasing tendency to an increasing tendency. In the film thickness measurement method for measuring the film thickness of the thin film by irradiating the substrate on which the thin film is formed and measuring the intensity of the measurement light that is reflected light or transmitted light of the light,
When the received light amount R _t , the reference light amount R ₀ , and the light amount change value ΔR _t , the light amount change value indicating the amount of change in the intensity of the measurement light is a difference between changes in the relative light amount R _t / R ₀ over a certain time. A change value calculating step for calculating the light amount change value ΔR _t ;
An inflection point for determining at least one of whether or not the light quantity change value calculated in the change value calculation step has changed from an increasing tendency to a decreasing tendency, or whether or not the light quantity change value has changed from a decreasing tendency to an increasing tendency A determination process;
Based on the light amount change value at the time when it is determined that the light amount change value has turned to decrease or increase in the inflection point determination step, or a reference for measuring the film thickness based on the light amount change value in the vicinity of the time point An inflection point change value calculating step for determining an inflection point change value;
A film thickness detection method comprising: detecting a film thickness based on the inflection point change value and the light amount change value determined in the inflection point change value calculation step. The change value calculation step and the inflection point determination step are performed a plurality of times at predetermined time intervals,
In the inflection point determination step, the number of times the light quantity change value is determined to be decreasing or the number of times determined to be increasing is counted, and it is determined whether or not the counted number has reached a predetermined number. 6. The method according to claim 5, further comprising: determining whether the light quantity change value has changed from an increasing tendency to a decreasing tendency, or whether the light quantity change value has changed from a decreasing tendency to an increasing tendency. The film thickness measuring method as described. The change value calculation step and the inflection point determination step are performed a plurality of times at predetermined time intervals,
In the inflection point determination step, the number of times that the light quantity change value is determined to be decreasing is counted a plurality of times or the number of times that the light amount change value is determined to be increasing is determined to be a plurality of times. Based on determining whether or not the predetermined number has been reached, it is determined whether or not the light amount change value has changed from an increasing tendency to a decreasing tendency, or whether or not the light amount change value has changed from a decreasing tendency to an increasing tendency The film thickness measuring method according to claim 5, wherein: The change value calculation step and the inflection point determination step are performed a plurality of times at predetermined time intervals,
In the inflection point determination step, the light amount change value is determined based on whether the light amount change value is determined to be decreasing at a predetermined frequency or whether it is determined to be increasing at a predetermined frequency. 6. The film thickness measuring method according to claim 5, wherein it is determined whether or not the value has changed from an increasing tendency to a decreasing tendency, or whether or not the light quantity change value has changed from a decreasing tendency to an increasing tendency. In a film thickness measurement device that measures the film thickness of a thin film by irradiating the substrate on which the thin film is formed and measuring the intensity of measurement light that is reflected light or transmitted light of the light,
When the received light amount R _t , the reference light amount R ₀ , and the light amount change value ΔR _t , the light amount change value indicating the amount of change in the intensity of the measurement light is a difference between changes in the relative light amount R _t / R ₀ over a certain time. Change value calculating means for calculating the light amount change value ΔR _t ;
An inflection point for determining at least one of whether or not the light quantity change value calculated in the change value calculation step has changed from an increasing tendency to a decreasing tendency or whether or not the light quantity change value has changed from a decreasing tendency to an increasing tendency A determination means;
Based on the light amount change value at the time when it is determined that the light amount change value has turned to decrease or increase in the inflection point determination step, or a reference for measuring the film thickness based on the light amount change value in the vicinity of the time point An inflection point change value calculating means for determining an inflection point change value;
A film thickness measuring device comprising: a film thickness detecting unit configured to detect a film thickness based on the inflection point change value and the light amount change value determined in the inflection point change value calculating step. The change value calculation means and the inflection point determination means perform the calculation of the light amount change value a plurality of times at a predetermined time interval,
The inflection point determination means counts the number of times that the light quantity change value has been determined to be decreasing or has increased, and determines whether or not the counted number has reached a predetermined number And determining whether the light quantity change value has changed from an increasing tendency to a decreasing tendency or whether the light quantity change value has changed from a decreasing tendency to an increasing tendency. The film thickness measuring apparatus described. The change value calculation means and the inflection point determination means perform the calculation of the light amount change value a plurality of times at a predetermined time interval,
The inflection point determination means counts the number of times that the light quantity change value is determined to be decreasing a plurality of times continuously or the number of times that the light amount change value is determined to be an increase tendency is determined to be a plurality of times. Based on determining whether or not the predetermined number has been reached, it is determined whether or not the light amount change value has changed from an increasing tendency to a decreasing tendency, or whether or not the light amount change value has changed from a decreasing tendency to an increasing tendency The film thickness measuring device according to claim 9. The change value calculation means and the inflection point determination means perform the calculation of the light amount change value a plurality of times at a predetermined time interval,
The inflection point determination means determines whether the light amount change value is determined to be decreasing with a predetermined frequency, or based on whether it is determined with a predetermined frequency that the light amount change value is increasing. The film thickness measuring apparatus according to claim 9, wherein it is determined whether or not the value has changed from an increasing tendency to a decreasing tendency, or whether or not the light quantity change value has changed from a decreasing tendency to an increasing tendency.

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