JP2004212098A - Coating thickness meter and coating thickness measurement method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating thickness meter and a coating thickness measurement method for precisely controlling coating thickness by improving the S/N ratio of an electric signal determined by measuring the coating thickness of a thin film during film formation without depending on a measurement wavelength. <P>SOLUTION: The coating thickness meter A comprises a light source 10 for projecting light to a substrate, where an optical thin film is formed; a spectroscope 20, where measurement light is guided from the substrate; and a controller 30. The spectroscope 20 comprises a spectral section 21 for dispensing measurement light, and a light reception section 28 having a plurality of photodiodes for photoelectrically converting the luminous flux being dispensed by the spectral section 21 for inducing a light reception current. The controller 30 comprises an exposure time pattern, where exposure time is set for each photodiode, and a means for transmitting a control signal for measuring light reception current output according to the spectroscope 20 according to the exposure time pattern. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical film thickness meter and a film thickness measuring method, and in particular, can accurately measure the film thickness of an optical thin film formed on a substrate in a vacuum chamber by vapor deposition, sputtering, CVD, or the like. The present invention relates to an optical film thickness meter and a film thickness measuring method.
[0002]
[Prior art]
The optical film thickness meter monitors the film thickness deposited on the substrate during the film formation process such as a vacuum deposition process or a sputtering film formation process, and controls the opening / closing operation of a deposition source shutter when a predetermined film thickness is deposited. Used as a controller for Further, it is used as a measuring device for measuring the spectral characteristics of the substrate on which the film formation process has been performed.
[0003]
2. Description of the Related Art Conventionally, there is a film thickness meter using a photodiode array as a light receiver for film thickness measurement and the like of a substrate during film formation (for example, see Patent Document 1). By using a photodiode array for the light receiver, it is possible to monitor the reflectance change during the film formation process at a plurality of wavelengths simultaneously and continuously.
[0004]
In the case of the film thickness meter as described above, the measurement light from the film-forming substrate is photoelectrically converted by the light receiving device, and is sent to the arithmetic unit as an electric signal. At this time, the arithmetic unit performs predetermined arithmetic processing based on the obtained electric signal, and calculates the reflectance and the transmittance.
[0005]
Here, in order to accurately control the film thickness, it is necessary to accurately detect the time when a predetermined film thickness is formed from the calculated reflectance and transmittance changes. For this reason, the electric signal from the light receiver is amplified as much as possible for processing, but the measurement accuracy of the film thickness is generally affected by the noise contained in the electric signal.
[0006]
In particular, the S / N ratio of the electric signal is relatively low in the wavelength range where the electric signal to be output is small. In general, such low S / N ratios are caused by radiation distribution characteristics of the light source (for example, in the case of a halogen light source, a small amount of light on the short wavelength side) and spectral sensitivity characteristics of the photodiode (the ultraviolet light side, The near-infrared light side is poor), and the wavelength dependence of the transmittance of an optical fiber used as an optical path.
[0007]
In order to compensate for the low S / N ratio of the electric signal, the arithmetic processing method of the obtained electric signal is variously improved, and accurate film thickness control is performed. That is, the software in the arithmetic unit is generally improved.
[0008]
[Patent Document 1]
JP-A-5-164518 (page 2-3, FIG. 1-6)
[0009]
[Problems to be solved by the invention]
However, in order to perform accurate film thickness control with a film thickness meter, the method of improving the software aspect of the control device does not necessarily improve the S / N ratio of the electric signal itself, so that the control accuracy is greatly improved. I couldn't expect that.
[0010]
Further, data in a wavelength range where the electric signal intensity obtained in the measurement wavelength range is small has a relatively poor S / N ratio. There is a problem that the error is larger than that of the measurement range.
[0011]
In view of the above problems, it is an object of the present invention to improve the S / N ratio of an electric signal obtained by measuring the thickness of a thin film during film formation irrespective of the measurement wavelength, and to accurately control the film thickness. An object of the present invention is to provide a film thickness gauge and a film thickness measuring method.
[0012]
[Means for Solving the Problems]
According to the film thickness meter of claim 1, the object is to provide a light projecting unit that emits light intermittently to a substrate on which an optical thin film is formed, and a light detection unit to which measurement light from the substrate is guided. And a control unit for controlling the film thickness measurement, wherein the light detection unit includes a spectroscopic unit that disperses the measurement light, and receives a light beam split by the spectroscopic unit. A plurality of light detecting elements for accumulating electric charges by photoelectric conversion and outputting a light receiving current to the control means, the control means comprising: an exposure time pattern in which an exposure time is set for each of the light detecting elements; This problem is solved by providing a control signal sending unit that sends a control signal for measuring the light receiving current output according to the pattern to the light detecting unit.
[0013]
As described above, according to the present invention, the light detection means to which the measurement light is guided is provided with the light detection elements capable of measuring a plurality of separated wavelength lights, and the exposure time of each light detection element is the exposure time pattern. It is configured to be able to set. By doing so, in the wavelength range where the light reception current is originally small, the exposure time can be lengthened and the light reception current can be made large, so that the S / N ratio of the signal can be improved.
[0014]
Further, as in claim 2, it is provided with a light projecting means for intermittently projecting light onto the substrate on which the optical thin film is formed, a light detecting means for guiding measurement light from the substrate, and a control means. A film thickness meter, wherein the light detection means includes a spectroscopy section for separating the measurement light, and receives the light flux split by the spectroscopy section, accumulates electric charges by photoelectric conversion, and controls the light reception current. A plurality of photodetectors for outputting to the photodetector, the control unit measures an exposure time pattern in which an exposure time is set for each of the photodetectors, a light-receiving current output corresponding to the exposure time pattern, and the photodetector. Control signal sending means for sending a control signal for measuring the dark current output according to the exposure time pattern to the light detecting means in a state where the light is not exposed, and a signal from the light detecting element corresponding to a predetermined measurement wavelength. Said Calculating means for the measurement of the photocurrent outputs subtracting the measured value of the dark current output by said photodetector current output of the measurement and the same exposure time pattern, when provided with a suitable.
[0015]
As described above, according to the present invention, the light detecting means to which the measuring light is guided is provided with the light detecting elements capable of measuring a plurality of separated wavelength lights, and the exposure time of each light detecting element is determined by the exposure time pattern. It is configured to be able to set. Further, by using the same exposure time pattern, it is possible to measure the light receiving current output and the dark current output in each of the photodetectors in which the exposure time and the dark current measurement time are substantially equal.
[0016]
By doing so, the exposure time in the wavelength range where the light reception current is originally small can be lengthened to increase the light reception current, so that the S / N ratio of the signal can be improved and Accurate dark current correction can be performed in the photodetector (each measurement wavelength).
[0017]
It is preferable that an input / output unit for setting the exposure time pattern to the control unit is provided.
[0018]
According to a fourth aspect of the present invention, there is provided a method for measuring an optical thickness of a thin film formed on a substrate, comprising: dispersing measurement light from the substrate; Are respectively irradiated on a plurality of light detection elements, and a light reception current output generated by photoelectric conversion by irradiation of the light beam at each exposure time according to an exposure time pattern in which an exposure time is set for each light detection element. It can be a method of measuring.
[0019]
Further, according to the film thickness measuring method according to claim 5, there is provided a method for measuring an optical film thickness of a thin film formed on a substrate, wherein the measuring light from the substrate is spectrally separated, and the separated luminous flux is measured. Are respectively irradiated on a plurality of light detection elements, and a light reception current output generated by photoelectric conversion by irradiation of the light beam at each exposure time according to an exposure time pattern in which an exposure time is set for each light detection element. Measure, interrupt the irradiation of the light beam to the photodetector by interrupting the measurement light from the substrate, measure the dark current output at a measurement time according to the exposure time pattern for each photodetector A method of performing an operation of subtracting a measured value of a dark current output based on the same exposure time pattern as a measurement of the received light current output from a measured value of the received light current output from the photodetector corresponding to a predetermined measurement wavelength. it can
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view showing a configuration of a film thickness meter of an embodiment, FIG. 2 is an explanatory diagram of a shutter mechanism of the embodiment, FIG. 3 is a block diagram showing a configuration of the film thickness meter of the embodiment, and FIG. FIG. 3 is a block diagram illustrating a configuration of a timing setting unit.
[0021]
FIG. 5 is an explanatory diagram of a continuous measurement process of the embodiment, FIG. 6 is an explanatory diagram showing an exposure time for each channel of the embodiment, and FIG. 7 is an explanatory diagram showing a schematic processing procedure of obtaining film thickness control data of the embodiment. 8 is an explanatory view showing an exposure time for each channel by the variable exposure method of the embodiment, FIG. 9 is an explanatory view showing a light receiving current output after dark current correction by basic measurement of the embodiment, and FIG. 10 is a variable exposure method of the embodiment FIG. 11 is a block diagram showing a configuration of a timing setting unit according to another embodiment, and FIG. 12 is an explanatory diagram showing an exposure time for each channel by a variable exposure method according to another embodiment. FIG. Note that the arrangement, shape, and the like described below do not limit the present invention, and it is needless to say that various modifications can be made in accordance with the gist of the present invention.
[0022]
FIG. 1 shows a schematic configuration diagram of a film thickness meter A according to an embodiment of the present invention. The film thickness meter A of the present example is a light transmission type film thickness meter that measures the film thickness from a change in the amount of light transmitted through the substrate 1 during film formation disposed in the vacuum chamber 50. The formation of the thin film on the substrate 1 is not limited to the vacuum deposition method, but may be a sputtering or CVD method. Further, although the film thickness meter A of this example is of a light transmission type, it is not limited to this and may be of a light reflection type.
[0023]
The film thickness meter A of the present embodiment includes a light projector 10 as a light projecting unit, a spectroscope 20 as a spectral unit, a controller 30 as a control unit, and the like. The light projector 10 includes a light projecting unit 11 and a shutter mechanism 14. The light projecting unit 11 includes a light source 12, such as a halogen lamp, a xenon lamp, or a deuterium lamp, a condenser lens 13, and a stabilizing power supply (not shown). Have.
[0024]
FIG. 2 is an explanatory diagram showing the configuration of the shutter mechanism 14. The shutter mechanism 14 includes a stepping motor 15 as a driving source, a rotary cover plate 16 having a substantially circular shape, a position detector 17, and the like. The shielding plate 16 includes a shielding portion 16a that shields the light of the light source 12 and a cutout portion 16b that allows the light of the light source 12 to pass to the vacuum chamber 50 side. A periodic pulsed light beam is transmitted.
[0025]
The motor 15 is configured to receive a control signal from the controller 30 and rotate the shielding plate 16 at a predetermined rotation speed as described later, and the rotation speed is variably set by the control signal. .
[0026]
As shown in FIG. 1, in the light projector 10, light emitted from a light source 12 is collected by a collecting lens 13, and the collected light flux is transmitted to a vacuum chamber 50 side by passing through a shutter mechanism 14. You. The light projector 10 and the vacuum chamber 50 are connected to each other, and the vacuum chamber 50 and the spectroscope 20 are connected by optical fibers 40 and 42, respectively. Further, a lens unit is provided in each of the optical fibers 40 and 42, and an optical path with a small spot diameter and close to parallel light is secured. In addition, not only such an optical fiber optical system but also a mirror reflection optical system may be used.
[0027]
The output side of the optical fiber 40 is bifurcated, and a part of the light beam incident on the optical fiber 40 is guided to the position detector 17 composed of a photodiode provided in the light projector 10 through the branch part 40a.
[0028]
With this configuration, the rotational position of the shield plate 16 is accurately detected by the position detector 17, and the controller 30 can monitor the rotational position of the shield plate 16 based on a detection signal sent from the position detector 17. It is possible to perform synchronous control accurately.
[0029]
Further, the electromagnetic mechanical shutter as conventionally used is not suitable for transmitting a pulsed light beam by intercepting the light source in a short period, but in the shutter mechanism 14 of the present example, the shutter portion is a rotary type. This makes it possible to transmit a short-period pulsed light beam.
[0030]
The spectroscope 20 as a light detecting means includes a spectroscopic unit 21 and a light receiving unit 28. The spectroscopy unit 21 is of the cross-Zernartana type, and includes a slit 22, a reflecting mirror 23 for forming collimated light, a diffraction grating 24, and a reflecting mirror 25. The light receiving section 28 includes a detecting element 26 having a photodiode array, and a detecting element driving section 27 for sending control signals P ₁ and P ₂ to the detecting element 26.
[0031]
The measurement light from the vacuum chamber 50 that has passed through the slit 22 is collimated by the reflecting mirror 23, enters the diffraction grating 24, and is diffracted by the diffraction grating 24 according to the wavelength. The diffracted light diffracted by the diffraction grating 24 is reflected by the reflecting mirror 25 and irradiates a plurality of photodiodes of the detecting element 26 respectively.
[0032]
The light receiving section 28 including the detection element 26 and the detection element driving section 27 in this example constitutes a charge accumulation type linear image sensor. The detecting element 26 is constituted by 512 photodiodes, switches, capacitors, etc. as 512 light detecting elements corresponding to 512 measurement channels. The detection element driving section 27 includes a shift register that sends control signals P ₁ and P ₂ to the respective switches according to a start pulse and a clock signal from the controller 30.
[0033]
The film thickness meter A of the present example is designed to be able to perform measurement by designating an arbitrary wavelength range of 300 nm, and each photodiode has a wavelength range of about 300 nm (for example, 380 nm to 680 nm). It receives diffracted light corresponding to a wavelength width of 0.6 nm.
[0034]
Each element such as the above 512 photodiodes is allocated to 512 channels, and the first channel is on the long wavelength side (for example, around 680 nm), and the 512th channel is on the short wavelength side (for example, around 380 nm). Is set to
[0035]
Note that the measurement wavelength range is not limited to 300 nm, and the wavelength range irradiated to each photodiode is not limited to about 0.6 nm. Further, the number of channels is not limited to 512. For example, a linear image sensor having 1024 photodiodes may be used and the number of channels may be set to 1024.
[0036]
An outline of the operation of the light receiving unit 28 will be described. When the photodiode of each channel is irradiated with the diffracted light, it is photoelectrically converted by the photodiode, and the electric charge is stored in a capacitor (not shown) in the light receiving unit 28.
[0037]
Detecting device driving section 27 starts sending a control signal P ₁ or P ₂ to each channel and receives a start pulse from the controller 30. The detection element driving unit 27, continue adding the number of channels every time when receiving the clock signal from the controller 30 sends a control signal P ₁ or P ₂ to sequentially for each channel switch at different times.
[0038]
Each switch is electrically closed each capacitor is connected to sequentially output side by a control signal P ₁ or P _2. The detection element driving unit 27 and each switch constitute a sending unit. As a result, the electric charge accumulated in each capacitor due to the irradiation of the measurement light is sequentially output to the controller 30 with a time lag for each channel.
[0039]
In the light receiving section 28 of such a charge storage method, the amount of stored charge is proportional to the product of the intensity of incident light and the exposure time (exposure amount). However, since the capacity of the capacitor is finite, the output takes a constant value when the exposure amount exceeds a predetermined exposure amount (saturation exposure amount), and has no meaning as a measured value. Therefore, the exposure time is adjusted in order to appropriately adjust the exposure amount.
[0040]
As shown in FIG. 3, the controller 30 includes a CPU 31 that performs film thickness measurement control and a control signal transmitting unit that receives a control signal from the CPU 31 and transmits a predetermined start pulse and a clock signal to the detection element driving unit 27. A timing setting unit 32, a PGA (program gain amplifier) 33 as an amplifier for receiving an output from the detection element 26 for each channel and amplifying a signal for each channel, and receiving and A / D converting an amplified signal from the PGA 33 to a CPU 31 A / D converter 34 for sending to the I / O unit, an interface unit 35, an input / output device 37 as an input / output unit for performing setting input processing and data output processing, and a storage unit 38 for storing output data, setting values, and the like. And so on.
[0041]
The storage unit 38 includes a ROM 38a, a RAM 38b used as a work area, and the like. The ROM 38a stores a control program for the film thickness meter A, an operation system program, and the like. A display device 36 such as a monitor or a printer is connected via an interface unit 35. The CPU 31 sends various control signals and the like to the light projector 10 and the spectroscope 20, receives measurement data from the spectroscope 20, and receives received data based on the program of the storage unit 38 and the setting input from the input / output device 37. Performs various processes such as amplification, storage, calculation, and output. The calculation means of this example is mainly constituted by the CPU 31.
[0042]
The PGA 33 receives the output for each channel from the detection element 26, changes the amplification factor for each channel according to the setting from the CPU 31, and outputs it to the A / D converter 34. That is, the operator can set and input the input signal from the input / output device 37 so as to amplify the output signal by a predetermined multiple for each measurement wavelength (that is, for each channel). Is set.
[0043]
With such a configuration, it is possible to selectively amplify an output signal in a wavelength range where the signal strength is small and obtain the data as data. By amplifying such a small signal intensity, it is possible to improve the followability to a change in the amount of light, to easily handle the amplified signal as a control value, and to easily control the film thickness.
[0044]
Further, predetermined film thickness measurement data is transmitted from the controller 30 to the control device 51 of the vacuum evaporation apparatus through the interface unit 35. The control device 51 controls the drive of a shutter device that shuts off the evaporation source based on the data.
[0045]
Further, the controller 30 sends a signal for controlling the rotation speed of the motor 15 to the light projector 10. The motor 15 rotates the shielding plate 16 at a predetermined rotation speed based on the control signal. Further, a position signal indicating the rotational position of the shielding plate 16 is sent from the position detector 17 to the controller 30. Thus, the controller 30 can synchronize the rotation position of the shielding plate 16 with the start pulse sent to the detection element driving unit 27.
[0046]
As shown in FIG. 4, the timing setting unit 32 includes a clock 32a, a frequency divider 32b, a frequency divider 32c, and a control gate 32d. The frequency dividers 32b and 32c each receive a signal from the clock 32a and transmit a clock signal to the detection element driving unit 27 via the control gate 32d. In the detection element driving section 27, a clock signal is used to determine the timing for transmitting the control signals P ₁ and P ₂ . Divider 32b, divider 32c corresponds to the clock signal for sending control signals P _1, the control signal P _2.
[0047]
The interval at which the frequency divider 32b sends the clock signal to each channel is fixed. The clock signal transmitted by the frequency divider 32b has a predetermined width in time, so that when one clock signal is transmitted, the next clock signal is sequentially transmitted at a predetermined time interval thereafter. It has become. However, the input / output device 37 may be configured so that the signal width can be variably set.
[0048]
The interval at which the frequency divider 32c transmits the clock signal to each channel can be set to be equal to or longer than the clock signal transmission interval of the frequency divider 32b. The setting is input from the input / output device 37 as described later, and the CPU 31 controls the frequency divider 32c according to the setting.
[0049]
When the clock signal transmission interval from the frequency divider 32c is set to be equal to the clock signal transmission interval from the frequency divider 32b, the clock signals for all the channels are transmitted from the respective frequency dividers 32b and 32c. Takes the same amount of time.
[0050]
On the other hand, if the clock signal transmission interval from the frequency divider 32c is set longer than the frequency divider 32b, the time width of each clock signal transmitted from the frequency divider 32c is set wider according to the setting. You. Thus, the time required for transmitting the clock signals for all the channels from the frequency divider 32c becomes longer in accordance with the clock signal width than the frequency divider 32b. In other words, the clock signal for a channel having a larger channel number has a linearly longer time to be transmitted.
[0051]
The control gate 32d receives a control signal from the CPU 31, and functions as a gate for selectively transmitting a clock signal from the frequency divider 32b and the frequency divider 32c and a start pulse from the CPU 31 to the detection element driving unit 27.
[0052]
That is, when the start pulse is selectively transmitted by the control signal from the CPU 31, the gate is switched to the frequency divider 32b, and the clock signal for all the channels is transmitted from the frequency divider 32b. When the clock signal is transmitted from the frequency divider 32b to all channels, the gate is switched to the frequency divider 32c, and the gate is maintained until the clock signal is transmitted from the frequency divider 32c to all channels.
[0053]
A plurality of clock signal widths can be set in the frequency divider 32c in advance, and any one of the plurality of clock signal widths can be selected by a control signal from the CPU 31. With such a simple configuration, the timing setting section 32 can variably set the clock signal transmission interval to the detection element driving section 27, and can variably set the exposure time for each channel.
[0054]
Next, the procedure for measuring the basic film thickness by the film thickness meter A of this example will be described. When the control signal is transmitted from the controller 30 to the light projector 10 and the shielding plate 16 rotates at a predetermined rotation speed, the light beam is not transmitted to the vacuum chamber 50 side (bright period) as shown in FIG. The period (dark period) is periodically repeated. In the case of this basic measurement example, one cycle of the light-dark period is about 0.3 seconds.
[0055]
The controller 30 sends a start pulse _PST1 to the detection element driving unit 27 as shown in FIG. Further, the controller 30 sequentially sends clock signals as control signals for the number of channels to the detection element driving unit 27. Detector element driving unit 27, upon receiving the start pulse P _ST1, in accordance with the clock signal from the controller 30 begins to sequentially transmits the control signal P ₁ to the channels of the detector elements 26. That is, this figure (C), (D), the detecting element driving unit 27 sequentially advance the channel by the shift register every time receiving a clock signal, it sends a control signal P ₁ while shifting the time for each channel . Each channel by the control signal P ₁ are sequentially reset.
[0056]
That is, at this time, the charges accumulated in the capacitors of the respective channels are output (see FIG. 9E). In this way, the reset output S _{1 of} each channel is sent to the controller 30 at the predetermined time (T ₁ ). Since reset output S ₁ is not related to the layer thickness data, not used to the thickness control of the substrate 1.
[0057]
When all the channels have been reset for a predetermined time (T ₁ ), a start pulse P _ST2 is sent from the controller 30 to the detection element driving unit 27 after a lapse of a predetermined time (T ₀ ), and the detection element is further changed according to the clock signal. control signal P ₂ from the drive unit 27 to the respective channels are sent in the same manner as the control signal P _1. During the light period, each channel is irradiated with the measurement light.
[0058]
When the control signal P ₂ are successively sent to the channel, the charge stored in the capacitor of each channel is sequentially outputted to PGA33 (photodetector current output S _2). In this way, a predetermined time (T _1), receiving the current output S ₂ of each channel is sent to the controller 30 (see FIG. (E)).
[0059]
That is, from each channel, since the control signal P ₁ is delivered for reset of each channel switch, charge control signal P ₂ for output is accumulated in the measurement time until sent (exposure time) It is output as the light-receiving current output S ₂ to the controller 30 side. As shown in FIG. 6, the exposure time T _S (= T ₁ + T ₀ , that is, the interval between the control signal P ₁ and the control signal P ₂ ) of each channel is constant.
[0060]
In addition, in the film thickness meter A of the present example, the start pulses P _ST1 and P _ST2 , the clock signals and the control signals P ₁ and P ₂ are transmitted not only in the bright period but also in the dark period, and the output of each channel is transmitted. Is to be detected. That is, _(in practice, the dark current output) receiving the current output S ₂ when the measuring light to the photodiode of each channel is not irradiated, is output as the same data as the received current output S ₂ of the light period.
[0061]
Accordingly, the time until the control signal P ₂ for output from the control signal P ₁ for reset is sent to the respective channels are sent to the dark period, approximately the same as that of the light period (i.e., exposure time T _S Approximately). By doing so, since the dark current output outputted from the photodiode becomes proportional to the time, it is possible to estimate the dark current component included in the received current output S ₂ of the same period to more accurately .
[0062]
In the film thickness meter A of this example, the light-dark period is periodically repeated as described above, and the same output processing is performed for each of the light period and the dark period. Obtained every time. Therefore, it is possible to accurately correct the noise component due to the dark current for each light-dark cycle.
[0063]
FIG. 7 shows a processing procedure for obtaining film thickness control data. First, as shown in FIG. 7, the light-receiving current output and the dark current output of each channel can be obtained at predetermined time intervals by the repeated continuous measurement. The light-receiving current output and dark current output of each channel output from the detecting element 26 are amplified in real time by a predetermined multiple for each channel by the PGA 33, and are converted into digital data by the A / D converter 34. The dark current data is stored in the storage unit 38 in the controller 30.
[0064]
Then, arithmetic processing is performed based on the obtained data. Specifically, the controller 30 as the calculating means subtracts the dark current data from the received light data at each measurement of the light / dark period cycle for each channel, and stores the data in the storage unit 38 as the received light intensity data from which noise has been removed.
[0065]
In addition, according to the setting input from the input / output device 37, the data integration process may be performed a predetermined number of times (for example, 15 times). By doing so, data accuracy is improved.
[0066]
Then, from the received light intensity data obtained by the arithmetic processing, transmittance, optical film thickness, and the like as optical characteristic values are further calculated, and calculation data for a plurality of preset channels (for example, five channels) is sent to the outside. The output is used for controlling the vapor deposition process. In the case of this example, the number of channels can be set in advance from the input / output device 37. Further, display processing is performed on the display device 36. Note that the calculation data for all the channels may be output to the outside.
[0067]
Next, a description will be given of a variable exposure method which is a gist of the present invention by applying the above basic film thickness measuring procedure. At the time of the basic film thickness measurement, since the control signals P ₁ and P ₂ are both sent out at the same time interval between the channels, the exposure time and the dark current measurement time of each channel are the same (T _S = T ₁ + T ₀ ). On the other hand, in the variable exposure method, the exposure time and the dark current measurement time are variably set for each channel.
[0068]
The variable exposure method, and sends for all channels control signals P ₁ as exposure time pattern illustrated in FIG. 8 (A) to (D) is required for the time T _1. And after the control signal P ₁ delivery, the control signals P ₂ to time T ₀ after start to be sequentially sent.
[0069]
FIG. 7A shows an exposure time pattern for measuring the basic film thickness. In the exposure time pattern, the time T ₂ required to transmit the control signal P ₂ is the same time T ₁ required to transmit the control signal P ₁ as described above, and the exposure time Ts of each channel is Identical.
[0070]
In FIG contrast (B) to (D), the time _{T 2} required to deliver a control signal _{P 2} are each twice the time _{T 1,} 4-fold, and has a 6 times. Therefore, when these exposure time patterns are selected, the exposure time of channel 1 (long wavelength side) is the same as that in the case of the basic film thickness measurement, but the exposure time is linear toward channel 512 (short wavelength side). Is set to be longer.
[0071]
For example, as shown in FIG. 9, when the received light intensity data having a relatively small signal output on the short wavelength side in the measurement wavelength range is obtained by the basic film thickness measurement, the exposure on the short wavelength side channel is performed by the variable exposure method. A predetermined exposure time pattern is selected to make the time longer. The selection of the exposure time pattern can be performed by selecting the clock signal width of the frequency divider 32c as described above. Furthermore, the exposure time pattern may be specified by specifying the time T ₀ and the time T ₁ from the input / output device 37. When the exposure time pattern is specified, the CPU 31 controls the timing setting unit 32 to sequentially send a start pulse and a clock signal to the detection element driving unit 27.
[0072]
When light intensity data as shown in FIG. 9 is obtained in the basic film thickness measurement, light intensity data as shown in FIG. 10 is obtained by measuring using each exposure time pattern shown in FIG. In the figure, a to d denote received light intensity data measured using the exposure time patterns of FIGS. 8A to 8D, respectively.
[0073]
As described above, in the variable exposure method, the exposure time at the measurement wavelength (channel) where the signal intensity is originally small can be lengthened, so that the value of the obtained light-receiving current output increases, thereby increasing the S / N ratio as a whole. Can be improved.
[0074]
Next, another embodiment for performing the variable exposure method will be described. FIG. 11 is a block diagram illustrating a configuration of the timing setting unit 32 according to another embodiment. As shown in FIG. 11, the timing setting unit 32 includes a clock 33a, an address generator 33b that receives a signal from the clock 33a and generates a channel address signal, and a start pulse and a start pulse to the detection element driving unit 27 at a predetermined timing. A frequency divider 33c for transmitting a clock signal, and a ROM 32d that stores accumulation timing setting data and operates based on a predetermined program are provided.
[0075]
A plurality of exposure time patterns are stored in the accumulation timing setting data, and the operator sets an exposure time pattern and a dark current measurement time control pattern for the entire channel by selecting an appropriate exposure time pattern from the input / output device 37. can do.
[0076]
The ROM 33d selects an exposure time pattern according to a control signal from the CPU 31. The ROM 33d executes a predetermined operation program, reads the selected exposure time pattern data, and outputs a clock signal for each channel to the frequency divider 33c according to the read exposure time pattern data and the address signal from the address generator 33d. A signal for controlling the transmission timing is transmitted.
[0077]
The frequency divider 33c sequentially transmits a start pulse and a clock signal to the detection element driving unit 27 according to the clock signal transmission timing control signal. Timing setting unit 32 of another embodiment is configured to deliver a clock signal frequency divider 33c correspond to both the control signals P ₁ and P _2.
[0078]
FIG. 12 shows an example of the exposure time pattern. The exposure time pattern of FIG. (A) to (D), the control signal P ₁ is similar to the exposure time pattern of the basic film thickness measurement, the each channel is sequentially sent in the same interval. When the control signal P ₁ is sent to all channels, starts to be transmitted is a control signal P ₂ after a time T _0.
[0079]
Control signal P _2, the transmission time for an increase in the delivery channel number is sent to increase nonlinearly. That is, the transmission interval to each channel is set to be non-linearly increased as the channel number increases. Time required for drawing (A) to (D) in the control signal P ₂ is sent to all channels, respectively 2.5, 4, 5, has a 8 times.
[0080]
Since the control signal P ₂ is sequentially transmitted as a temporally non-linear, it is possible to channel number than smaller channels, towards the channel the channel number is large so that more exposure time is long .
[0081]
That is, as shown in FIGS. 7A to 7D, when N ′> N, when the exposure time Ts (N ′) of the channel N ′ and the exposure time Ts (N) of the channel N are compared, The exposure time Ts (N ′) is equal to or longer than the exposure time Ts (N).
[0082]
The exposure time pattern of this embodiment is configured so that an arbitrary pattern can be realized by storing the exposure time pattern in the ROM 32d in advance as accumulation timing setting data. For example, such an exposure time pattern can be realized by transmitting a control signal designating a clock signal transmission interval at any time from the ROM 33d to the frequency divider 33c in accordance with the address. The exposure time pattern can be a linear pattern (FIG. 8) as in the above-described embodiment, in addition to the above-described non-linear pattern.
[0083]
It is also possible to use a temporally linear pattern up to a predetermined channel and a temporally non-linear pattern with respect to subsequent channels. Furthermore, by separating the channels ranges, different linear pattern for each channel range it is also possible to (transmission interval of the control signal P ₂ are different patterns).
[0084]
In addition, in the film thickness meter A of this example, it is also possible to change each continuation time (light period time, dark period time) of the light-dark period cycle by setting from the input / output device 37. However, it is desirable that the exposure time of the light-receiving current output measurement and the measurement time of the dark current output measurement be substantially the same. This makes it possible to adjust the exposure time for each channel arbitrarily, and to select the optimum exposure time, so that accurate film thickness measurement data can be obtained.
[0085]
Further, the film thickness meter A of the present example can simultaneously measure a predetermined wavelength range, but can also measure only one or a plurality of wavelengths within the measurement wavelength range. In this case, predetermined data can be obtained by specifying a channel corresponding to the wavelength.
[0086]
【The invention's effect】
As described above, according to the film thickness meter and the film thickness measuring method of the present invention, the light beam from the light projector is sent out in a pulsed manner in a short period, and the film substrate is irradiated with the light beam from the light projector. The measurement is similarly performed for a plurality of wavelengths in both the non-irradiated periods.
[0087]
Then, in each light-dark cycle, the length of the exposure time and the dark current measurement time of each channel can be set according to the original signal output intensity of each channel. Specifically, the length of the exposure time and the like in the measurement wavelength range where the signal output intensity is small can be set relatively long. Therefore, it is possible to perform measurement with an improved gain in such a measurement wavelength range.
[0088]
This makes it possible to measure both the light receiving current output and the dark current output for a plurality of wavelengths within one cycle, to obtain accurate data in consideration of the dark current component in real time, and to measure the entire measurement wavelength range. The S / N ratio of the electric signal output obtained over the range can be improved. Therefore, it is possible to improve the accuracy of the film thickness control with the accurate film thickness control data obtained in this way.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram illustrating a configuration of a film thickness meter according to an embodiment.
FIG. 2 is an explanatory diagram of a shutter mechanism according to the embodiment.
FIG. 3 is a block diagram illustrating a configuration of a film thickness meter according to an embodiment.
FIG. 4 is a block diagram illustrating a configuration of a timing setting unit according to the embodiment.
FIG. 5 is an explanatory diagram of a continuous measurement process according to the embodiment.
FIG. 6 is an explanatory diagram showing an exposure time for each channel according to the embodiment.
FIG. 7 is an explanatory diagram illustrating a schematic processing procedure for acquiring film thickness control data according to the embodiment.
FIG. 8 is an explanatory diagram showing an exposure time for each channel according to the variable exposure method of the embodiment.
FIG. 9 is an explanatory diagram showing a light-receiving current output after dark current correction based on basic measurement in the example.
FIG. 10 is an explanatory diagram illustrating a light-receiving current output after dark current correction by the variable exposure method according to the embodiment.
FIG. 11 is a block diagram illustrating a configuration of a timing setting unit according to another embodiment.
FIG. 12 is an explanatory diagram showing an exposure time for each channel by a variable exposure method according to another embodiment.
[Explanation of symbols]
Reference Signs List 1 substrate, 10 projector, 11 projector, 12 light source, 13 condenser lens, 14 shutter mechanism, 15 motor, 16 shield plate, 16a shield, 16b cutout, 17 position detector, 20 spectroscope, 21 spectroscope , 22 slits, 23, 25 reflecting mirrors, 24 diffraction gratings, 26 detecting elements, 27 detecting element driving sections, 28 light receiving sections, 30 controllers, 32 timing setting sections, 32a, 33a clocks, 32b, 32c, 33c frequency dividers, 32d control gate, 33b address generator, 33d ROM, 34 A / D converter, 35 interface unit, 36 display device, 37 input / output device, 38 storage unit, 40, 42 optical fiber, 40a branch unit, 50 vacuum chamber, 51 control device, A thickness _{meter, P 1,} P ₂ control signal, _{S 1} reset output, _{S 2} photodetector current output, _{T S} exposure time

Claims (5)

A film thickness meter comprising: a light projecting unit that emits light intermittently to a substrate on which an optical thin film is formed; a light detection unit that guides measurement light from the substrate; and a control unit that controls film thickness measurement. And
The light detecting means includes a spectroscopy section for splitting the measurement light, and a plurality of photodetectors for receiving the light flux split by the spectroscopy section, accumulating electric charges by photoelectric conversion, and outputting a light receiving current to the control means. Equipped with an element,
The control means transmits an exposure time pattern in which an exposure time is set for each of the light detection elements, and a control signal for measuring a light-receiving current output according to the exposure time pattern to the light detection means. A film thickness meter comprising sending means. A light emitting unit that intermittently emits light to the substrate on which the optical thin film is formed, a light detection unit to which measurement light from the substrate is guided, and a control unit, a film thickness meter including:
The light detecting means includes a spectroscopy section for splitting the measurement light, and a plurality of photodetectors for receiving the light flux split by the spectroscopy section, accumulating electric charges by photoelectric conversion, and outputting a light receiving current to the control means. Equipped with an element,
The control means is configured to measure an exposure time pattern in which an exposure time is set for each of the light detection elements, measure a light-receiving current output according to the exposure time pattern, and respond to the exposure time pattern when the light detection elements are not exposed. Control signal sending means for sending a control signal for measuring the dark current output to the light detecting means,
Calculating means for subtracting the measured value of the dark current output by the same exposure time pattern as the measurement of the received light current output from the measured value of the received light current output from the photodetector corresponding to a predetermined measurement wavelength. Characteristic film thickness gauge. The film thickness meter according to claim 1, further comprising an input / output unit configured to set the exposure time pattern to the control unit. A method for measuring the optical film thickness of a thin film formed on a substrate,
Dispersing the measurement light from the substrate, irradiating the separated light flux to a plurality of photodetectors,
A method for measuring a light-receiving current output generated by photoelectric conversion by irradiating the light beam at each of the exposure times according to an exposure time pattern in which an exposure time is set for each of the light detection elements. . A method for measuring the optical film thickness of a thin film formed on a substrate,
Dispersing the measurement light from the substrate, irradiating the separated light flux to a plurality of photodetectors,
A light-receiving current output generated by photoelectric conversion by irradiation of the light beam at each of the exposure times is measured according to an exposure time pattern in which an exposure time is set for each of the light detection elements,
Interrupting the irradiation of the light beam to the photodetector by interrupting the measurement light from the substrate,
Measure the dark current output at a measurement time according to the exposure time pattern for each photodetector,
A film which performs an operation of subtracting a measured value of a dark current output based on the same exposure time pattern as a measurement of the received light current output from a measured value of the received light current output from the photodetector corresponding to a predetermined measurement wavelength. Thickness measurement method.

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