JP6544171B2 - Surface treatment status monitoring device - Google Patents

Description

  The present invention relates to a surface treatment status monitoring device that measures the size of a microstructure formed on a sample surface, for example, the depth of fine holes or grooves formed on the surface of a semiconductor substrate by etching.

  In the process of manufacturing a semiconductor integrated circuit, etching is performed to form fine holes (holes) and trenches (trench) such as TSV (= Through Silicon Via) in a semiconductor substrate such as a silicon wafer. There is. In general, when performing etching processing, masking with a resist film is performed on a portion of the substrate where holes and grooves are not formed before processing. As a result, only the unmasked portion is selectively scraped off during processing, and when the resist film is removed after processing, a substrate with holes and grooves formed is obtained. Since the depth of the hole or groove formed at this time depends on various conditions such as etching time, type of etching gas, gas pressure, etc., in order to make the depth of the hole or groove a target depth, During processing, control is performed to determine the etching end point and adjust the conditions while monitoring temporal changes in the depths of the holes and grooves.

  In Patent Document 1, when forming a groove by etching a substrate whose surface is masked with a resist film, laser light is irradiated to the surface of the substrate being processed to monitor a temporal change in the depth of the groove How to do it is described. The laser light emitted to the surface of the substrate being processed is reflected from the surface of the resist film, the surface of the substrate, and the surface of the groove formed by etching. Among the interference light generated due to the interference of these reflected light, the interference light generated from the light reflected from the surface of the resist film and the light reflected from the surface of the groove, and the light reflected from the surface of the substrate and the surface of the groove The intensity of the interference light generated from the reflected light of any of the layers fluctuates reflecting the depth of the groove during the etching process. Specifically, each time the groove depth changes by a quarter of the wavelength of the laser light, the tendency of the change in the intensity of the interference light changes from an increase to a decrease, or from a decrease to an increase. That is, the total intensity of the interference light to be measured is represented by the sum of a fixed value and a value that periodically increases and decreases. In the method described in Patent Document 1, the total intensity of the interference light is continuously observed, and the maximum value and the minimum value that appear each time the groove depth changes by a quarter of the wavelength of the laser light are captured. Monitor temporal changes in groove depth.

  However, in this method, the maximum value or the minimum value (hereinafter collectively referred to as “extreme value”) is determined unless it is confirmed that the tendency of the change in intensity of the interference light is reversed. I can not do it. Therefore, a time lag occurs between the timing at which the extremum actually appears and the timing at which the extremum is determined. In addition, after the extreme value is determined, the depth of the groove can not be determined until the next extreme value is determined. That is, in this method, there is a problem that it is not possible to measure the groove depth which changes every moment in real time.

  In order to solve such problems, the present inventor has proposed a surface treatment status monitoring device capable of measuring in real time the size of a fine structure formed on a sample surface by surface treatment processing (Patent Document 2).

  FIG. 1 shows a schematic configuration of the surface treatment status monitoring device. The surface processing situation monitoring device includes a light source 110, a measurement optical system 120, a light separating unit 130, and a data processing unit 140. The light source 110 and the measurement optical system 120, and the measurement optical system 120 and the light separating unit 130 are connected to each other via an optical fiber.

  As the light source 110, for example, a super luminescent diode (SLD) light source is used which emits coherent light having a center wavelength of 820 nm and a full width at half maximum of 15 nm. The measurement light emitted from the light source 110 is taken into the incident side optical fiber 121, travels through the optical fiber 123 through the fiber coupler 122, and exits from the tip of the optical fiber 123. The measurement light emitted from the optical fiber 123 is irradiated onto the sample 150 through the collimator lens 124.

  The light emitted from the light source 110 is reflected on the surface of the sample 150 and the bottom of the groove 151 formed on the surface, respectively (FIG. 2). These reflected lights 160 and 161 enter the optical fiber 123 through the collimator lens 124. The reflected lights 160 and 161 incident on the optical fiber 123 are guided to the fiber coupler 122, and at least a part of them is interfered to generate interference light and reach the light splitting unit 130. The measurement light including the interference light that has reached the light separating unit 130 is wavelength dispersed by the light separating means 131 such as a diffraction grating, and is detected for each wavelength by the array detector 132 such as a CCD line sensor. An output signal from the array detector 132 corresponding to each wavelength is input to the data processing unit 140.

  The data processing unit 140 creates a spectrum (FIG. 3A) of the measurement light including the interference light based on the output signal from the array detector 132. Subsequently, the axis of the measurement light spectrum is converted from wavelength to wave number (FIG. 3 (b)). Furthermore, the intensity of the measurement light spectrum is normalized using the spectrum of the reflected light from the surface of the sample acquired before the start of the surface treatment (FIG. 3 (c)). Then, the measurement light spectrum after normalization is subjected to frequency analysis (Fourier transform) to obtain a power spectrum (FIG. 3 (d)), and the depth of the groove is determined from the peak position on the power spectrum. As described above, in the surface treatment status monitoring device described in Patent Document 2, the depth of the groove is determined only by mathematically processing the data obtained by detecting the measurement light including the interference light. Measurement is possible.

JP 10-325708 A JP, 2013-120063, A JP, 2014-206467, A

  In the apparatus described in Patent Document 2, the measurement light spectrum is acquired, and the change in the intensity of interference light with respect to the wave number (interference wave) is frequency analyzed to obtain the depth of the groove. However, in the case of fine grooves, the period of the interference wave with respect to the wave number becomes long. As shown in FIG. 4 as an example (example of the groove depth of 4.0 μm), when the groove becomes shallow, the period of the interference wave becomes longer than the entire area of the measurement light spectrum (corresponding to the wavelength band of SLD). Then, only the interference wave of less than one cycle (about 3/4 in the example of FIG. 4) can be confirmed in the measurement light spectrum, and there is a problem that it becomes difficult to obtain the groove depth with high accuracy. The

  The problem to be solved by the present invention is the size of the structure to be measured, such as the depth of a hole or groove formed on the surface of a sample by surface treatment or the size of a step, or the thickness of a film layer or substrate increasing or decreasing. In the surface treatment status monitoring device that measures the size of a micro structure, the size of a micro structure is to be measured in real time and with higher accuracy than in the past.

The present invention, which has been made to solve the above problems, is formed on the surface of a sample, such as the depth or step of a hole or groove formed on a substrate by surface treatment, or the thickness of a film layer or substrate increasing or decreasing. A surface treatment status monitoring device for measuring the size of the target structure to be measured;
a) a plurality of light sources emitting light having a predetermined wavelength width and coherence, the plurality of light sources having mutually different wavelength bands of emitted light,
b) an irradiation optical system which irradiates irradiation light emitted from each of the plurality of light sources to a range including the measurement target structure on the surface of the sample;
c) A detection unit for wavelength-dispersing and detecting measurement light including interference light generated by interference of light respectively reflected by two portions defining the size of the measurement target structure;
d) a spectrum generation unit that generates a measurement light spectrum based on the output signal from the detection unit;
e) A structure determination unit that performs frequency analysis on the measurement light spectrum to determine the size of the measurement target structure.

  For example, when the structure to be measured is a groove formed on the surface of the substrate, the two portions defining the size of the structure to be measured are the surface of the substrate and the bottom of the groove. Further, when the structure to be measured is a film layer, the two parts are the upper surface and the lower surface of the film layer. The measurement light includes not only the interference light but also reflected light which has not interfered.

  In the surface treatment condition monitoring apparatus according to the present invention, since the plurality of light sources having different wavelength bands are used, the wavelength band of the irradiation light becomes wider than in the prior art. For example, when two SLD light sources having the same wavelength width as each other and having different emission bands from each other are used, it is possible to measure the intensity change of the interference light in the wavelength band twice as large as the conventional one. As a result, with a conventional light source, only a half cycle interference wave can be obtained and it is difficult to measure the size of the structure. Frequency analysis can be performed to measure the size of the microstructure with high accuracy. Further, in the surface treatment status monitoring device according to the present invention, the interference light is only processed in the same manner as the device described in Patent Document 2, so the size of the measurement target structure can be measured in real time.

  In the case of the SLD light source, although it is possible to widen the emission band by increasing the type and number of diodes used for one light source, such an SLD light source is special and increases the cost. On the other hand, in the surface treatment status monitoring device of the present invention, the wavelength band can be expanded by using two independent light sources in combination. For example, the device can be configured inexpensively by combining a plurality of inexpensive SLD light sources for general use. . Also, for example, it is possible to determine the width of the combined wavelength band so that at least one cycle of interference wave can be obtained from the smallest possible measurement target structure, and to combine multiple light sources to meet the requirements. Compared to the conventional device using only one light source, the degree of freedom in design is high. In addition, a synthetic | combination wavelength zone | band means the zone | band prescribed | regulated by the shortest wavelength and the longest wavelength among the wavelengths of the irradiated light emitted from the said several light source.

  In the surface treatment status monitoring device according to the present invention, a plurality of light sources in which the light emission bands are not continuous (separated) can be used in combination as appropriate. However, in this case, it is desirable that the total of the wavelength bands of the irradiation lights respectively emitted from the plurality of light sources be half or more of the combined wavelength band.

  Even if a light source with a wide synthetic wavelength band is used, the measurement light spectrum can be acquired only in the wavelength band of the light (irradiated light) actually irradiated to the sample. Therefore, in order to obtain the size of the fine structure with high accuracy, it is desirable to select the plurality of light sources so that at least a half period interference wave is included in the wavelength band of the measurement light spectrum to be actually acquired. .

  In the surface treatment status monitoring device according to the present invention, it is preferable that the structure determination unit performs frequency analysis after normalizing the measurement light spectrum with a spectrum of light reflected from the sample surface before surface treatment processing.

  As described above, the measurement light to be detected also includes the reflected light which has not interfered. If the spectrum of such measurement light is directly subjected to frequency analysis, a peak derived from the peak shape of the reflected light appears in the low frequency region of the obtained power spectrum, making it difficult to determine the peak indicating the size of the structure to be measured. There is. In particular, when the structure to be measured is small, it is difficult to determine the peak indicating the size of the structure. As described above, by normalizing the measurement light spectrum data by the spectrum data of the reflected light from the sample surface, the peak derived from the peak of the reflected light is removed from the power spectrum, and the size of the structure to be measured with higher accuracy. Can be measured.

  By using the surface treatment status monitoring device according to the present invention, it is possible to measure the size of a minute measurement target structure in real time and with higher accuracy than in the past.

The principal part block diagram of the conventional surface treatment condition monitoring apparatus. The figure explaining the reflected light in the sample surface. The figure which demonstrates the procedure which measures the magnitude | size of measurement object structure from a measurement light spectrum in the conventional surface treatment condition monitoring apparatus. The figure explaining the interference wave in case the magnitude | size of measurement object structure is minute. BRIEF DESCRIPTION OF THE DRAWINGS The principal part block diagram of one Example of the surface treatment condition monitoring apparatus which concerns on this invention. The figure which shows the light emission zone | band of two SLD light sources used in a present Example. The figure which demonstrates the procedure which measures the magnitude | size of measurement object structure from a measurement light spectrum in the surface treatment condition monitoring apparatus in a present Example. The graph which compared the result of having measured the magnitude | size of measurement object structure using the apparatus of a present Example with the past. The graph which compared the measurement error at the time of measuring the size of measurement object structure using the device of a present example with the conventional. The example which measured the magnitude | size of three types of measurement object structures which mutually differ in a magnitude | size with the surface treatment condition monitoring apparatus of a present Example. The figure which shows the measured value of the frequency analysis part regarding a minute measurement object structure.

  Hereinafter, an embodiment of a surface treatment status monitoring device according to the present invention will be described with reference to the drawings. The principal part structure of the surface treatment condition monitoring apparatus 1 of a present Example is shown in FIG. In the surface treatment status monitoring device 1 of the present embodiment, the depth (the size of the structure to be measured) of the groove formed on the surface of the sample 50 by etching is monitored in real time.

  The surface treatment status monitoring device 1 of the present embodiment includes a light source unit 10, a measurement optical system 20, a light separating unit 30, and a data processing unit 40. The light source unit 10 includes a first SLD light source 11 and a second SLD light source 12 which have different wavelength bands of light emitted from each other. As shown in FIG. 6, the emission band of the first SLD light source 11 is about 790 nm to about 850 nm, and the emission band of the second SLD light source is about 890 nm to about 900 nm. The irradiation lights emitted from the first SLD light source 11 and the second SLD light source 12 are introduced to the light source part first optical fiber 13 and the light source part second optical fiber 14, respectively, and are synthesized by the light source part fiber coupler 15 to become synthesized irradiation light. , And is sent to the measurement system first optical fiber 21 of the measurement optical system 20. The first SLD light source 11 is the same as the SLD light source used in the conventional surface treatment status monitoring device described with reference to FIGS. 1 to 4.

  The combined irradiation light introduced into the measurement system first optical fiber 21 of the measurement optical system 20 travels through the measurement system second optical fiber 23 via the measurement system fiber coupler 22 and is emitted from the tip thereof. The combined irradiation light emitted from the measurement system second optical fiber 23 is irradiated onto the surface of the sample 50 via the collimator lens 24.

  As shown in the enlarged view in FIG. 5, the light 60, 61 reflected by the surface of the sample 50 and the bottom of the groove 51 formed in the surface of the sample 50 respectively passes through the collimating lens 24 and the measurement system second light It enters the fiber 23. The reflected lights 60 and 61 incident on the measurement system second optical fiber 23 interfere with each other at least in part in the measurement system fiber coupler 22 to become interference light, and are transmitted to the light splitting unit 30 through the measurement system third optical fiber 25.

  The measurement light including the interference light that has entered the light splitting unit 30 is wavelength-separated by the diffraction grating 31, and is detected by the CCD line sensor 32 for each wavelength. An output signal from the CCD line sensor 32 is sent to the data processing unit 40, stored in the storage unit 41, and provided for processing to be described later. The light separating unit 30 may be configured to separate the measurement light into wavelengths and detect the intensity for each wavelength, and a light separating element other than the diffraction grating or a detector other than the CCD line sensor may be used.

  The data processing unit 40 functionally includes a spectrum generation unit 42, a frequency analysis unit 43, a fitting calculation unit 44, and a structure determination unit 45 in addition to the storage unit 41. The substance of the data processing unit 40 is a general personal computer, and the functions of the units excluding the storage unit 41 are realized by executing a predetermined program. Further, an input unit 48 and a display unit 49 are connected to the data processing unit 40. The storage unit 41 is a formula representing the relationship between the data of the spectrum of the reflected light from the surface of the sample 50 before etching and the intensity of the reflected light and the intensity of the measuring light including the measuring light during the etching. A theoretical equation including the depth of the groove 51 formed in the sample 50 as a parameter is stored. The theoretical formula will be described later.

  The spectrum generation unit 42 obtains the intensity of the measurement light for each wavelength from the output signal of the CCD line sensor 32 (FIG. 7A), converts the wavelength into a wave number, and measures the measurement light spectrum with the wave number as the horizontal axis. It generates (FIG. 7 (b)). Subsequently, the structure determination unit 45 reads the spectral intensity of the reflected light from the storage unit 41, and normalizes the intensity of the measurement light spectrum by dividing it by the intensity of the reflected light spectrum (FIG. 7 (c)). Thus, a spectrum (corresponding to an interference wave) in which the change in intensity of the interference light is emphasized can be obtained. Further, the structure determination unit 45 analyzes the frequency of the normalized measurement light spectrum to obtain a power spectrum, and determines the depth of the groove from the position of the peak appearing in the power spectrum (FIG. 7 (d)).

  As shown in FIG. 7 (d), when the depth of the groove (the size of the structure to be measured) is several tens of μm or more, as described with reference to FIG. However, the size of the structure to be measured can be monitored at the same level. This is because the change in intensity of the interference light (interference wave) appears in a plurality of cycles in the measurement light spectrum acquired in the wavelength band of the light emitted from one light source. In other words, when the interference wave appearing in the measurement light spectrum is less than one cycle, the accuracy of the frequency analysis is deteriorated, and it becomes difficult to determine the size of the measurement target structure. Specifically, as described in FIG. 4, in the conventional device using only one light source corresponding to the first SLD light source 11, measurement is performed when the size of the structure to be measured is approximately 10 μm or less (4 μm in FIG. 4) The period of the interference wave appearing in the light spectrum decreases to about one cycle, and it becomes difficult to measure the size of the structure to be measured.

  On the other hand, in the surface treatment status monitoring apparatus 1 of the present embodiment, in addition to the first SLD light source 11, the second SLD light source 12 having a different light emission band from the first SLD light source 11 is used, as shown by the broken line in FIG. In addition to the emission band of the first SLD light source, the measurement light spectrum is acquired also in the wavelength band of the second SLD light source 12. Therefore, it is possible to acquire an interference wave with more cycles than that of the conventional device, perform frequency analysis, and measure the size of the measurement target structure with high accuracy.

  FIGS. 8 and 9 show the results of measuring the size of the structure to be measured with the surface treatment status monitoring device 1 of this example and the conventional surface treatment status monitoring device. FIG. 8 is a graph comparing measurement values when the size of the structure to be measured is 30 μm or less. FIG. 9 is a graph comparing errors of measured values in the range of 10 μm to 200 μm in the size of the structure to be measured. From FIG. 8, when the structure to be measured is larger than 10 μm, good measurement results are obtained in any of the measurement results of the device of the present embodiment and the conventional device. When the size is 10 μm or less, it is understood that the measurement accuracy is higher when the apparatus of the present embodiment is used. Further, it can be understood from FIG. 9 that the measurement error is smaller than in the conventional case when the apparatus of this embodiment is used over the whole range of 10 μm to 200 μm.

  Although it is possible to use two light sources that emit light in mutually continuous wavelength bands in the surface treatment status monitoring device 1 of the present embodiment, as described above, two light sources having mutually separated wavelength bands may be used. It is preferable to combine them.

  The measurement light spectrum acquired about the groove | channel of 3.2 micrometers in depth using the surface treatment condition monitoring apparatus 1 of a present Example is shown to Fig.10 (a). The upper part of FIG. 10 (a) is the measurement light spectrum with the wave number as the horizontal axis, the reflected light spectrum, and the interference wave, and the lower part is the spectrum after normalization with the reflected light spectrum with the wave number as the horizontal axis. It is. Further, FIG. 10 (b) shows the one obtained for the groove having a depth of 3.6 μm, and FIG. 10 (c) shows the one obtained for the groove having a depth of 4.0 μm in the same manner.

  When the spectra of FIGS. 10A to 10C in the wavelength band of the first SLD light source 11 are compared, it can be seen that the shapes of the three spectra and the shapes of the interference waves are very similar. Therefore, it is difficult to distinguish them by frequency analysis. In order to discriminate these three structures, it is necessary to acquire a spectrum (interference wave) in a wavelength band different from the wavelength band of the first SLD light source 11 having mutually different shapes. In the apparatus of the present embodiment, by using the second SLD light source 12 which emits light in wavelength bands different in the shape of spectrum (interference wave), three measurement object structures which are different in size can be distinguished.

  Here, if it is intended to use a second light source emitting in a wavelength band adjacent to the wavelength band of the first SLD light source 11, one emitting in a band of about 850 nm to about 900 nm should be used. In general, the light source is more expensive as the emission band is wider when the intensity is comparable. Further, in the case of the above example, even if the measurement light spectrum is acquired at a wavelength close to the wavelength band of the first SLD light source 11, it is difficult to distinguish the three measurement target structures. Therefore, as in the present embodiment, by combining two light sources having mutually separated light emission bands, the shape of the spectrum (interference wave) can be efficiently determined by an apparatus that can be configured inexpensively, and the structure to be measured with high accuracy The size of the can be measured.

  However, if the emission bands of the two light sources are extremely far apart, and their bandwidths are narrow, the bandwidth in which the measurement light including the interference light can be detected and the spectrum can be acquired becomes narrow, and the frequency analysis It is difficult to measure the size of the structure to be measured with high accuracy because interference waves with sufficient frequency can not be obtained. In the present embodiment, in consideration of this point, the minimum size (4.0 μm in the present embodiment) of the structure to be measured is determined in advance. Then, when the structure of the size is measured, interference waves of at least one cycle appear in the combined wavelength band, and the sum of the wavelength bands of the irradiation light actually emitted by the two light sources is half of the combined wavelength band. The two light sources are combined so as to occupy the above (that is, an interference wave of at least 1/2 cycle can be obtained).

  As described above, in the present embodiment, the minimum size of the structure to be measured is 4.0 μm, but in the etching process, the groove depth is monitored even after the treatment starts until the groove depth reaches 4.0 μm. Is desirable. In the surface treatment situation monitoring apparatus 1 of the present embodiment, the fitting operation unit 44 is used in such a case.

The fitting operation unit 44 reads the intensity data and theoretical formula of the reflected light spectrum from the storage unit 41. This theoretical expression represents the relationship between the reflected light intensity and the measurement light intensity as an expression including the size of the structure to be measured as a single parameter, and for example, the following expression proposed by the inventor in Patent Document 3 1) can be used. In the above-described frequency analysis, the measurement light spectrum was normalized with the reflected light spectrum to exclude and analyze the influence of the reflected light. On the other hand, in equation (1), the intensity of the measurement light corresponds to the term (the product of Rr (λ) and the first term in parentheses) corresponding to the reflected light from the surface of the sample 50 and the term (Rr ( It is represented by the product of λ) and the second term in parentheses. Then, the parameters α ₁ , α ₂ , and T (t) are appropriately changed to match (fit) the measured intensity of the measurement light spectrum, and the size of the measurement target structure is estimated.

In equation (1), λ is the wavelength of the measurement light, t is the time, Rr (λ) is the intensity of the reflected light from the surface of the sample 50, and α ₁ is a coefficient corresponding to the intensity of the reflected light from the surface of the sample 50 Α ₂ is a coefficient corresponding to the intensity of the interference light, T (t) is the size of the structure to be measured at time t, and n (λ) is the refractive index of the material constituting the structure to be measured at wavelength λ. Among these, α ₁ and α ₂ change with the state of the surface of the sample 50 (for example, flatness and surface temperature) and the size T (t) of the structure to be measured. As described above, the intensity data Rr (λ) of the reflected light spectrum is measured in advance and stored in the storage unit 41.

When the measurement light is wavelength-separated and detected at a certain time point t, the intensities of the measurement light at a plurality of wavelengths are obtained, and the spectrum generation unit 42 generates the measurement light spectrum as described above. In parallel with this, the fitting operation unit 44 uses appropriate initial values as the parameters α ₁ , α ₂ and T (t) in the above equation (1), and a plurality of wavelengths equal to the wavelength at which the measurement light is detected. Calculate the measured light intensity at the wavelength. Subsequently, the fitting operation unit 44 obtains the difference between the measured intensity and the calculated intensity at each of the plurality of wavelengths, and uses a suitable method such as the least square method to minimize the total sum of the differences at the plurality of wavelengths. Determine α ₁ , α ₂ , and T (t). Thereby, the size T (t) of the structure to be measured can be estimated.

  Unlike frequency analysis, even if the measurement target structure is small, the size can be estimated by the calculation by the fitting calculation unit 44. However, in the calculation by the fitting calculation unit 44, the load on the data processing unit 40 becomes large because the optimum value is found while changing a plurality of parameters little by little. Therefore, it is preferable to minimize the number of calculations performed by the fitting calculation unit 44.

  Therefore, in the present embodiment, immediately after the start of etching, the size of the structure to be measured is determined using both frequency analysis and estimation by the fitting operation unit 44. As shown in FIG. 11, in the frequency analysis, if the size of the structure to be measured is smaller than the above-described minimum size (4.0 μm), the accuracy is degraded. Therefore, for a while after the start of the etching process, the structure determination unit 45 uses the estimation result by the fitting calculation unit 44 as a measurement result to obtain a difference from the result of the frequency analysis unit. Then, for example, when it is confirmed that the difference between estimated values of a predetermined number of consecutive times is less than or equal to a preset threshold, or when the size of the measurement target structure reaches the minimum size, estimation by the fitting operation unit 44 Finish. Then, after that, the structure determination unit 45 determines the depth of the groove (the size of the measurement target structure) based on the result of the frequency analysis. As a result, even if the size of the measurement target structure is equal to or less than the above-described minimum size, measurement can be performed with high accuracy, and the load on the data processing unit 40 can be minimized.

  The above-described embodiment is an example, and can be appropriately modified in accordance with the spirit of the present invention. Although two SLD light sources 11 and 12 are used in the above embodiment, other types of light sources may be used, and three or more light sources may be combined. Further, in the above embodiment, although the combined irradiation light obtained by combining the light emitted from the two SLD light sources 11 and 12 in the light source unit fiber coupler 15 is irradiated to the surface of the sample 50, the irradiated light emitted from the two light sources The same region of the surface of the sample 50 may be irradiated without synthesizing the

  In the above embodiments, the example has been described focusing on the example of measuring (monitoring) the depth of the groove during etching in real time, but in addition, the depth or level difference of the hole formed on the substrate by surface treatment, or It is possible to measure in real time the size of various measurement target structures formed on the sample surface, such as increasing or decreasing film layer and substrate thickness.

  In the above embodiment, an example in which the fitting calculation unit 44 is used for a while from immediately after the start in the etching process has been described, but in the case where the target structure is gradually reduced as in the measurement of the resist film thickness For a while after the start of the measurement, the size is determined only by the frequency analysis unit 43, and the fitting calculation unit 44 is used from the time when the value reaches the preset minimum size (or a time slightly before). It can also be done.

DESCRIPTION OF SYMBOLS 1 ... surface processing condition monitoring apparatus 10 ... light source part 11 ... 1st SLD light source 12 ... 2nd SLD light source 13 ... light source part 1st optical fiber 14 ... light source part 2nd optical fiber 15 ... light source part fiber coupler 20 ... measurement optical system 21 ... Measurement system first optical fiber 22 Measurement system fiber coupler 23 Measurement system second optical fiber 24 Collimator lens 25 Measurement system third optical fiber 30 spectroscopy unit 31 diffraction grating 32 CCD line sensor 40 data processing unit 41 storage unit 42 spectrum generation unit 43 frequency analysis unit 44 fitting operation unit 45 structure determination unit 48 input unit 49 display unit 50 sample 51 groove

Claims (4)

The surface treatment status to measure the size of the measurement target structure formed on the sample surface, such as the depth or step of the hole or groove formed on the substrate by surface treatment processing, or the thickness of the film layer or substrate increasing or decreasing A monitoring device,
a) a plurality of light sources emitting light having a predetermined wavelength width and coherence, the plurality of light sources having mutually different wavelength bands of emitted light,
b) an irradiation optical system which irradiates irradiation light emitted from each of the plurality of light sources to a range including the measurement target structure on the surface of the sample;
c) A detection unit for wavelength-dispersing and detecting measurement light including interference light generated by interference of light respectively reflected by two portions defining the size of the measurement target structure;
d) a spectrum generation unit that generates a measurement light spectrum based on the output signal from the detection unit;
e) a structure determination unit that performs frequency analysis on the measurement light spectrum to determine the size of the measurement target structure ;
The sum of the plurality of wavelength bands of illumination light from the light source is emitted respectively, more than half der Rukoto synthetic wavelength band defined by the shortest wavelength and the longest wavelength of the wavelength of the irradiation light emitted from the plurality of light sources Surface treatment status monitoring device characterized by   The surface treatment status monitoring device according to claim 1, wherein light emission zones of the plurality of light sources are separated from each other. The surface treatment status monitoring according to claim 1 or 2 , wherein the structure determination unit performs frequency analysis after normalizing the measurement light spectrum with a spectrum of light reflected from the sample surface before surface treatment processing. apparatus. f) A mathematical expression that represents the relationship between the intensity of the reflected light from the sample surface before the surface treatment and the intensity of the measurement light, using a theoretical expression that includes the size of the structure to be measured as a parameter A fitting operation unit configured to estimate the size of the measurement target structure by fitting the operation spectrum represented by
The surface treatment status according to any one of claims 1 to 3 , wherein the structure determination unit determines the size of the measurement target structure based on the result of the frequency analysis and the estimation result of the fitting operation unit. Monitoring device.

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