JPH07311165A - X-ray reflectance analyzer - Google Patents

Abstract

PURPOSE:To evaluate a sample having unknown retractive index or density by extracting the oscillatory component from a measured X-ray reflectance, performing Fourier analysis while altering the refractive index, and displaying the Fourier transform intensity three-dimensionaily for the retractive index and frequency, thereby determining the optimal retractive index of a thin film causing a peak value. CONSTITUTION:An X-ray reflectance pattern measured for a sample of thin films 1, 2 formed on a substrate 3 is subjected to Fourier transform. Since the reflectance of each layer 1, 2 is unknown, Fourier transform is performed for the refractive index delta ranging over 10<-6>-10<-5>. Three peaks can be predicted from a two layer film but since four peaks A-D appeared, a decision is made that the peak B appearing at a frequency position two times as high as that of the peak A is an overtone. The Fourier transformed intensities of the retractive index and frequency are then displayed by three-dimensional level lines and a combination of refractive index and frequency corresponding to a maximal value is determined systematically. The film thickness is determined uniquely from the combination. Consequently, the film thickness and refractive index can be determined simultaneously for each layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention measures the X-ray reflectance of a single-layer or multiple-layer thin film formed on a substrate and analyzes the obtained pattern to determine the film thickness and refractive index of the thin film. The present invention relates to an X-ray reflectance analyzer that nondestructively evaluates information such as density and density.

[0002]

2. Description of the Related Art At present, devices in which a thin film is intentionally formed on a substrate for various purposes are industrially manufactured. Also, there is a case where a thin film formed on a substrate by accident changes the characteristics of elements and materials. The film thickness and density of the thin film formed on the substrate intentionally or accidentally affect the characteristics of elements and materials, and a highly accurate analysis method is required to control or evaluate them. Is. As a simple film thickness evaluation method, there is a method of performing fluorescent X-ray spectroscopy measurement and evaluating from the peak intensities of the constituent elements, but this method requires that a calibration curve representing the correlation between the film thickness and the peak intensity is obtained in advance. This is a relative evaluation method that cannot be achieved. On the other hand, in recent years, attempts have been made to measure the X-ray reflectance of a thin film, analyze the obtained pattern, and perform an absolute evaluation of the film thickness and film quality of the thin film. This method using X-rays has the features that it can be performed in the atmosphere, that it can be applied to a system that is opaque to light such as metal, and that it can be evaluated without destroying the sample.

There is a Fourier analysis method as a typical film thickness analysis method based on X-ray reflectance. This is a method for calculating the film thickness by performing Fourier analysis on the vibration structure of the X-ray pattern, and is disclosed in, for example, Jpn. J. Appl. Phys. 31 (1992) L113.

The Fourier analysis method assumes a refractive index or density of a thin film, corrects the periodic structure based on the refractive index or density, and further assumes the refractive index assumed when converting the frequency position of the peak obtained by Fourier transform into the film thickness. Alternatively, since density is used, in order to obtain an accurate film thickness, the refractive index or density of the thin film used as a measurement reference must be used. Also,
The Fourier analysis method is characterized in that a large number of peaks appear when the number of layers of a film increases, as in a multilayer laminated film, and it becomes very difficult to analyze them.

By the way, for the measurement of the X-ray reflectance pattern used in these analysis methods, it is desirable to use an X-ray optical system with a high accuracy capable of controlling an angle of about one thousandth and a monochromatic light source. Further, in order to improve the accuracy of the analysis, it is desirable that the number of data points to be analyzed is large and data of a wide incident angle range can be used, but for that purpose, a wide dynamic range is required in X-ray detection. .
Conventionally widely used scintillation counters only guarantee a dynamic range of about 5 digits. Therefore, aluminum foil is used as an attenuation filter, and this filter is used for measurement in the region where the incident angle is small and the reflected X-ray intensity is high, and when the incident angle increases and the reflected X-ray intensity decreases to some extent, the filter is used. Except for the above, a method is used in which the following measurement is performed, the extinction rate of the filter is taken into consideration, the intensity of the high intensity side region is corrected, and the region without the filter and the data are connected. If you connect the data with only one point,
The correction of the extinction ratio is often inaccurate, and the slope of the curve may become discontinuous at the connection point. On the other hand, first measure the condition with the filter, return the incident angle 2θ by 0.5 degree, and then measure the condition without the filter so that the data points may overlap at several points when the intensity decreases to some extent. , And the method of connecting the data smoothly by correcting the intensity at multiple data points where the angles overlap Mat. Res. Soc. Symp. Proc., 208,
It is disclosed on p.327.

[0006]

As described above, accurate evaluation of the film thickness requires inputting at least the refractive index or density of the thin film. Therefore, the X-ray reflectivity measurement method has been conventionally used to accurately evaluate the film thickness and film quality of a sample whose identity is known to some extent, and has never been used as an evaluation method for an unknown sample. For unknown samples, it is necessary to examine the composition, the rough film thickness, and the like by using another analysis device prior to these methods, which causes a problem that it takes time and effort. Also, when using other analyzers together, there is a possibility that contamination or alteration may occur during handling of the sample, or the spatial area evaluated by the device may differ, so an accurate initial value may not always be obtained. It was Further, it takes time to measure the X-ray reflectance pattern, and it is difficult to use it as a product quality control monitor on the line.

An object of the present invention is to provide an X-ray reflectance analyzer capable of analyzing a film structure model and a sample of which the film thickness, refractive index and density of each layer are unknown. further,
Accurate and speedy analysis without contamination or deterioration X
It is also one of the purposes to provide a linear reflectance analyzer.

[0008]

In order to solve the above problems, first, an analysis method of X-ray reflectance will be examined. As an example, when a two-layer thin film is formed on a substrate, if the surface and interface are smooth and the absorption inside the film is small, the X-ray reflectance in the region of the incident angle θ larger than the critical angle of total reflection of the film is The pattern is approximated by Equation 1. The two layers of thin film are herein referred to as thin film 1 and thin film 2, respectively. FIG. 2 shows a schematic diagram of this sample.

[0009]

[Equation 1]

The refractive index δ of the film used in the above can be expressed by Equation 2.

[0011]

[Equation 2]

If the elemental composition of the film and the density ρ are found in equation 2, δ can be calculated because the rest are constants. See the references cited above for more details on these equations.

In Equation 1, the first to third terms are reflections from the surface and the interface, and the fourth and fifth terms are the thin film 1 and the thin film 1, respectively.
The vibration component of the thin film 2 due to interference in the film, the sixth term is the thin film 1
And a vibration component due to interference in the synthetic film that is a combination of the thin film 2 and the thin film 2. All of these terms are inversely proportional to the fourth power of θ,
The third term is a base component, and the fourth to sixth terms are vibration giving components. Therefore, the base component is subtracted, the vibration component is extracted by normalizing it by the −4th power of θ, and this is subjected to Fourier analysis. However, when the film thickness t is obtained by Fourier analysis, the content of cos is proportional to the horizontal axis, that is, cos (constant × t ×
It should be in the form of (horizontal axis). However, as is clear from Equation 1, this is not satisfied when the horizontal axis is θ. for that reason,
As shown in Expression 3, it is necessary to convert the horizontal axis from θ to φ and correct it to the form of cos (constant × t × φ).

[0014]

[Equation 3]

However, if the δ of the thin film 1 is used as the refractive index δ in the equation 3, only the fourth term of the equation 1 representing the vibration component due to the thin film 1 is corrected. That is, in order to obtain each vibration component, it is necessary to perform correction using the refractive index of the film caused by each vibration. Here, when the correction is made with the refractive index of a certain layer, the period of the vibration component due to the other layer is slightly shifted, so that the intensity of the peak obtained by the Fourier transform becomes small. In the present invention, this property is utilized to enable analysis of a sample whose film model, film thickness of each layer, and film quality are unknown. That is, after extracting the vibrating structure, Fourier analysis is performed while changing the refractive index δ, and the Fourier transform intensity at each refractive index and frequency is stored. Then, the Fourier transform intensity with respect to the refractive index and the frequency is three-dimensionally displayed. Accordingly, even when there are a plurality of peaks on the Fourier analysis result generated by the vibration structure generated by the thin film, it becomes easy to individually obtain the refractive index at which each peak is maximum. Also,
The Fourier transform intensity is not very sensitive to the refractive index, but the three-dimensional display shows the symmetry of the distribution of the Fourier transform intensity in a wide refractive index region as a reference, and the maximum value of the combination of the refractive index and the frequency Make decisions easier,
This makes it possible to obtain the refractive index δ and the film thickness t of the thin film without initial values. The above procedure is summarized in a flowchart and shown in FIG.

As a means for three-dimensionally displaying using a data set consisting of three sets of refractive index δ, frequency, and Fourier transform intensity, the Fourier transform intensity is calculated by arranging the refractive index δ and frequency on the vertical and horizontal axes. It is recommended to display contour lines or mapping by color. Further, the points of the combination having the maximum value, that is, the peak and the ridge may be simply displayed. In addition, a technique for realizing three-dimensional display by utilizing computer graphics and holography techniques can be expected in the future.

Further, since the film thickness t is uniquely obtained from the combination of the refractive index δ and the frequency, the above-mentioned display of the refractive index δ and the frequency can be changed to the display of the refractive index δ and the film thickness t. In this case, the desired thin film thickness can be read directly from the display, which is more practical. In order to display the refractive index δ and the film thickness t, it is necessary to convert the frequency dependency of the Fourier transform intensity into the film thickness dependency of the Fourier transform intensity. The process is as shown in the flowchart of FIG. It may be done in a loop that calculates while swinging δ, or the loop ends,
It is also possible to collectively calculate after obtaining the frequency dependence of the Fourier transform intensity for all the refractive indices δ.

Further, when the composition is known, the refractive index δ is determined only from the density ρ according to the equation (2). In such cases,
The Fourier analysis can be performed by shaking the density ρ, and the three-dimensional display of the Fourier transform intensity with respect to the density ρ and the frequency or the density ρ and the film thickness t becomes possible.
And the film thickness t are determined. In the case of a film composed of a light element like an organic substance, the atomic scattering factor of the light element is so small that it can be ignored, and the ratio of atomic number and atomic weight can be approximated to 1: 2, so the term due to composition is 1 Since it can be fixed to / 2 and the refractive index δ can be determined only by the density ρ, a method of performing Fourier analysis by shaking the density ρ is effective. This allows nondestructive evaluation of the density of organic thin films of unknown density.

Displaying the Fourier transform intensity with respect to the refractive index δ and the film thickness t is effective for distinguishing the peak due to the synthesis of a plurality of films among the plurality of peaks. For example, the sixth term of the equation 1 is a vibration component generated by the synthesis of the thin film 1 and the thin film 2, and the product of the refractive index δ of the thin film 1 and the film thickness t and the thin film 2
The product of the refractive index δ of the film thickness t and the sum of the products of the film thickness t divided by the composite film thickness of the film 1 and the thin film 2 corresponds to the apparent refractive index δ of this composite film. The composite film thickness is determined. Therefore, the product δt of the apparent refractive index and the film thickness of this composite film is equal to the sum of the product δt of the thin film 1 and the product δt of the thin film 2. Therefore, when the Fourier transform intensity is displayed for the refractive index δ and the film thickness t, the area of a rectangle whose diagonal is a straight line connecting the origin with the position of the film thickness t and the refractive index δ where the Fourier transform intensity has a maximum value for each peak. Becomes δt,
Since the rectangular area for the peak of the thin film 1 and the area for the thin film 2 added thereto are equal to the area for the synthetic film, the synthetic film can be visually discriminated.

This is the Fourier transform intensity with density ρ and film thickness t.
The same applies to the case where is displayed, which is particularly effective for analysis of a multilayer organic film.

As described above, the product of the refractive index δ and the film thickness t or the product of the density ρ and the film thickness t at the maximum point of each peak is effective for the analysis of the multilayer film structure. It is convenient to have a function to pick up and list out. It is also complicated to provide a function of estimating the layer structure of a thin film by using one of the judgment factors that some sums of picked up products are equal to other single products within a predetermined error range. It is effective for analyzing various multilayer films.

By the way, when the Fourier transform intensity is displayed three-dimensionally, there is a mode in which one of the refractive index δ or the density ρ and one of the frequency or the film thickness t is displayed. It is convenient to use them properly, so it is good to have these modes switchable.

The method for analyzing the film thickness and refractive index of the thin film, or the density and film structure of the thin film has been described above, but it is better to obtain information about the composition. This can be solved by providing a means for dispersing the fluorescent X-ray generated from the sample by the incident X-ray for measuring the X reflectance, analyzing the obtained fluorescent X-ray spectrum, and determining the composition. The composition obtained can be used to determine the refractive index δ of the thin film. With this method, it is not necessary to move the sample between a plurality of devices, so there is no risk of contamination or alteration. Also,
It is preferable that the apparatus is provided with a database that collects crystal structures and densities so that the crystal structure information and the densities of the obtained substances of composition can be read and the refractive index δ can be calculated using the information. Further, in this method, since the spatial region on the sample for measuring the X-ray reflectance and the region for composition analysis are the same, more accurate analysis can be realized by using a plurality of devices together. This point is particularly important in the analysis of a minute region having an X-ray beam width of 100 μm or less. Further, it is more effective for analysis if fluorescent X-ray measurement is performed at two or more incident angles and the information depth is changed so that the information of the outermost surface and the information of the inner layer can be obtained separately.

In addition, not only the composition but also the peak intensity in the fluorescent X-ray measurement was stored, and the X-ray reflectance analysis of several samples was performed, and the obtained film thickness was stored in advance. Correlation with the fluorescent X-ray peak intensity, that is, the calibration curve is obtained, and subsequent film thickness evaluation is performed exclusively from the fluorescent X-ray measurement and the previously obtained calibration curve, thereby speeding up the evaluation on the production line. It is also possible to apply it to quality control monitors.

Next, a method of expanding the dynamic range of X-ray reflectance measurement by using a light-attenuating means will be examined. FIG. 10 shows a schematic diagram of a conventional example in which the measurement regions with and without the light-reducing means are overlapped for the purpose of improving the accuracy of intensity correction. Here, when switching the presence or absence of the dimming means, the incident angle is returned by a predetermined angle, but a method for avoiding the problem of backlash at this time will be considered.

As shown in FIG. 11, prior to the actual measurement,
A function of preliminarily examining the angle θc at which the reflected light weakens to a predetermined intensity Ic is provided by using a light reducing means. It is assumed that the angle regions of front and rear Δθ are overlapped with each other with this θ c sandwiched. In this measurement, the dimming means is used to start angular scanning from a region with a large reflection intensity, and when the angle reaches (θc-Δθ), the intensity when the dimming means is used while automatically switching the dimming means. Continue to measure and store both the strength and the strength when not in use until the angle reaches (θc + Δθ). After the angle (θc + Δθ), the measurement is performed without using the dimming means. After the measurement, in the angular range from (θc −Δθ) to (θc + Δθ) measured by overlapping, determine the extinction ratio of the extinction device from the intensity ratio of the data with and without the extinction device. , Correct the data on the high intensity side and smoothly connect the overlap section. By doing so, it is possible to realize the overlap of the measurement areas with and without the light reducing means without reversing the angular scanning.

The object can also be achieved by the following method. That is, as shown in FIG.
When the angle scanning is started from a region having a large reflection intensity and the reflection intensity decreases to a predetermined intensity I1 or less, both the intensity when the dimming unit is used and the intensity when the dimming unit is not used while automatically switching the dimming unit. Is continuously measured and stored until the intensity when the dimming means is not used becomes equal to or lower than the predetermined intensity I2. After the measurement is completed, the extinction ratio of the dimming means is determined from the intensity ratio of the data with and without the dimming means measured in the overlapped section, and the high-intensity side data is corrected to Tie smoothly. Also by doing so, it is possible to realize the overlap of the measurement areas with and without the light reducing means without reversing the angular scanning.

The extension of the dynamic range by the intensity correction using the above-mentioned dimming means makes the light source sufficiently bright.
If the detector has high sensitivity, it is possible to secure a wider dynamic range by making the dimming means multi-stage or by using the dimming means capable of continuously changing the dimming rate.

[0029]

After the vibration component of the measured X-ray reflectance is extracted, Fourier analysis is performed while changing the refractive index, and the Fourier transform intensity at each refractive index and frequency is stored, and the Fourier transform for the refractive index and frequency is performed. By displaying the intensity three-dimensionally, it becomes possible to easily obtain the optimum value of the refractive index of the thin film which causes each peak. This makes it possible to evaluate even a sample whose refractive index and density are unknown. Contour line display and color-based display are effective for displaying three-dimensional data. In addition, the display with peaks and ridges is simple and easy to see.

Since the film thickness is uniquely determined from the refractive index and the frequency, the above-mentioned display is made into a three-dimensional Fourier transform intensity for the refractive index and the film thickness. It is more practical because it can be obtained directly.

When the composition is known or the thin film is made of a light element, the density can be used as a parameter instead of the refractive index, and the three-dimensional representation of the density and the frequency, or the Fourier transform intensity of the density and the film thickness. By doing so, it becomes possible to nondestructively control the film thickness and film quality of films having the same composition and to evaluate the density of organic thin films.

When the refractive index or density and the film thickness are three-dimensionally displayed, the peaks at which a plurality of films are involved are discriminated by using the position where the Fourier transform intensity has a maximum value and the area of a rectangle whose diagonal line is the origin. It becomes easy and is effective for analysis of multilayer films.

Similarly, the function of listing out the product of the refractive index and the film thickness or the product of the density and the film thickness, which takes the maximum value of each peak, and the combination of these products are summed to obtain a predetermined value. Effective information can be obtained in multi-layer film analysis by listing out those that are equal to other single products in the error range, and by providing a function for estimating the layer structure.

If the refractive index or density, the frequency or the film thickness can be selected as parameters and the modes can be switched, the optimum ones for various purposes can be used, which is convenient.

By providing the function of spectroscopically measuring the fluorescent X-rays generated by the incident X-rays, the information of the composition necessary for obtaining the refractive index used for the analysis can be obtained without the risk of contamination or alteration. Further, since the spatial areas to be measured are the same, the composition of the portion whose reflectance is accurately measured can be obtained.

By equipping the apparatus with a database relating to the crystal structure and density, it is possible to directly obtain the density required for obtaining the refractive index from the obtained composition or to calculate the density from the crystal structure information. Therefore, it demonstrates its power in the analysis of unknown samples. Further, the correlation between the peak intensity of the fluorescent X-ray and the X-ray reflectance analysis result is stored,
First, using several samples, create a calibration curve from these correlations, and perform subsequent evaluations using the peak intensity of the fluorescent X-ray and the calibration curve to speed up the evaluation and improve the quality on the line. Can be used for management monitoring.

By automatically switching the presence or absence of the dimming means and measuring the intensity in the case of the dimming means and the intensity in the absence of the dimming means in a predetermined angle region, the backlash is prevented from occurring. Therefore, highly accurate intensity correction is realized. Further, the dynamic range can be further widened by using a multi-stage light reducing means or using a light reducing means capable of continuously switching the light reducing rate.

[0038]

EXAMPLES Examples of the present invention will be described in detail below.

Example 1 As shown in FIG. 2, consider Fourier analysis of an X-ray reflectance pattern measured in a sample in which a two-layer thin film is formed on a substrate. Here, it is assumed that the refractive index of each layer is unknown. Therefore, Fourier analysis is performed while changing the refractive index δ. As an X-ray source, for example, CuK
When α rays are used, the refractive index δ of most substances is in the order of 10 −6 to 10 −5, so δ may be varied within this range. Although it will be touched on later, the Fourier transform intensity is not so sensitive to the refractive index, so it is easier to analyze by making a wide swing in the range of δ. An example of the result of Fourier transform using different refractive indices δ is shown in FIG. 3 side by side.

Theoretically, from an n-layer multilayer film, n (n + 1)
The appearance of two peaks is expected. Actually, if the roughness of the interface is large or the difference in refractive index between layers is small, the number of peaks will decrease, and in the opposite case,
A peak (overtone) is produced at the double frequency position. When the film of two layers is present as in the sample of FIG. 2, the appearance of three peaks is expected, but in FIG. 3, four peaks are seen. For the sake of explanation, A, B, C, and
Name it D. Of these, B is located at a frequency position approximately twice that of A, so there is a possibility that it is an overtone of A.

After changing the refractive index δ and performing Fourier analysis, the Fourier transform intensities with respect to the refractive index and the frequency are three-dimensionally shown in contour lines in FIG. It is preferable that the contour display program uses an algorithm incorporating data interpolation. Each of the peaks A to D displayed in contour lines forms a mountain-like profile. When the origin is located at the lower left position, the series of each peak has a downward sloping profile.
Since the Fourier transform intensity is not as sensitive to the refractive index as it is to the frequency, the symmetry of the Fourier transform intensity distribution in a wide refractive index region is very useful for determining the position of the refractive index that has the maximum value at each peak. . The determination of the peak position may be designated by the analyst on the screen of the apparatus, or may be designated by mathematical means such as obtaining the center of gravity of the contour line figure. By displaying three-dimensionally in this way, A
For each of the peaks D to D, the combination of the refractive index and the frequency having the maximum value can be systematically determined. In FIG. 4, the position of the maximum value of each peak is marked with a cross.

Here, since peak A and peak B have almost the same refractive index positions where the maximum values are present, it is highly likely that they are the same substance, and together with the finding that the previous frequency is doubled, It can be determined that peak B is an overtone of peak A. Thus, the present invention also provides useful information for overtone identification. Furthermore, if the combination of frequency and refractive index is determined by the above method, the film thickness can be uniquely obtained from these. As described above, even if the refractive index of each layer is unknown, the film thickness and the refractive index of each layer can be simultaneously obtained by the present invention.

[Embodiment 2] By mapping the obtained Fourier transform intensities for the refractive index and the frequency for each color, the visibility is further improved, and the effect equal to or more than that of the embodiment 1 is obtained.

Any of lightness, saturation, and hue may be used for color classification. For example, if the color scheme is blue for low intensity, green for medium intensity, and red for high intensity, it is close to the altitude display on the map, so that the sense is easy to grasp. Further, the mapping in which only the lightness is changed is suitable for grayscale printout. It should be noted that by incorporating a data interpolation technique in the mapping and making the pixels finer, the profile of the intensity distribution becomes smooth, and it becomes easy to determine the peak position from the symmetry.

[Embodiment 3] Taking contour lines display one step further,
Similar to the topography on the map, the profile of the Fourier transform intensity is displayed by the ridge and the peak. An example in which the profile of the Fourier transform intensity is displayed by ridges and peaks is shown in FIG.

In a sample in which the thin film is a multi-layer film and many peaks appear, this display method is effective because the structure is simple and easy to discriminate. It may be added to the function of the apparatus as an auxiliary display mode of the first or second embodiment.

[Embodiment 4] FIG. 6 shows an example in which the film thickness is obtained from the refractive index and the frequency, and the Fourier transform intensity is three-dimensionally displayed with respect to the refractive index and the film thickness. Although FIG. 6 shows an example of the contour line display, the display method of mapping for each color or the display with peaks and ridges is the same. By displaying the refractive index and the film thickness, the film thickness and the refractive index of the thin film to be evaluated can be directly obtained, which is more practical.

Here, when peak D is a peak due to the composite film of the film of peak A and the film of peak C, δAtA + δ
The relationship of CtC = δDtD is established. When the refractive index and the film thickness are displayed as shown in FIG. 6, the product (δt) of the refractive index of the peak and the film thickness corresponds to a rectangle having a straight line connecting the peak position and the origin as a diagonal line. That is, it becomes possible to visually discriminate δAtA + δCtC = δDtD, which is a relation for distinguishing the peaks due to the synthesis, and the analysis becomes easy.

[Embodiment 5] When the composition is known, the refractive index is determined from the equation 2 if the density is known. In such a case, the density ρ is shaken, the refractive index δ is calculated from the density ρ,
Fourier analysis is performed, and the obtained Fourier transform intensity profile is three-dimensionally displayed with respect to density and frequency, or density and film thickness, and the density and film thickness of each peak are determined.
As the display method, for example, the above-mentioned contour line display, color-based mapping, ridge line and peak display, etc. are used. When determining the density of a thin film, the specific gravity cannot be measured normally due to the small amount of sample.
However, by using the present invention, the density of the thin film as well as the film thickness can be determined nondestructively.

It can be applied to the film quality evaluation of a film whose density varies depending on conditions such as a CVD thin film.

[Embodiment 6] In a film composed of a light element such as an organic substance, the atomic scattering factor is negligible, and the ratio of atomic number and atomic weight is approximately 1: 2.
Even if it can be approximated to / 2, and the exact composition is not known, the density ρ is shaken to calculate an approximate value of the refractive index δ, and as in Example 5,
It is possible to determine the density and the film thickness of each peak by three-dimensionally displaying the Fourier transform intensity for the density and the frequency or the density and the film thickness. In this case, since the refractive index δ and the density ρ are proportional to each other, the apparent density ρ of the synthetic film is the same as in Example 4.
The product of the film thickness t and the film thickness t is equal to the sum of the product of the density and the film thickness of the thin films forming the composite film. Therefore, if the Fourier transform intensities of the density and the film thickness are displayed three-dimensionally, the peak due to the composite film can be visually discriminated. In FIG. 7, the relationship of ρAtA + ρCtC = ρDtD showing that peak D is due to the synthetic film of peak A and peak C is read.

[Embodiment 7] In order to discriminate the composite film, the product of the refractive index δ and the film thickness t or the product of the density ρ and the film thickness t, which takes the maximum value of each peak, is calculated and printed out. It is used by the analyst to determine when the sum of these partial products is equal to another single product.

Further, the combination of these numerical values is surveyed in the apparatus, and the ones in which the sum of the combinations of some products is equal to the other products are listed out within a predetermined error range, and a film having a complex multilayer structure is formed. It helps to estimate the structure.

[Embodiment 8] 3 of the above Fourier transform intensities
In the three-dimensional display, a program is set up so that it can display any combination of refractive index and frequency, refractive index and film thickness, density and frequency, and density and film thickness, and the analyst can select the optimum display mode according to the purpose. It can be switched by selecting it. This improves usability.

[Embodiment 9] In addition to an optical system for measuring the X-ray reflectance, a monochromator and a detector for dispersing fluorescent X-rays generated from the sample surface are installed. Since the X-ray reflectance measurement is performed at an incident / reflection angle of about 10 degrees or less, an optical system for fluorescent X-ray measurement may be provided on the high angle side. As the excitation light source for fluorescent X-ray measurement, the light source for X-ray reflectance measurement is used as it is. The fluorescent X-ray measurement may be carried out either before or after the X-ray reflectance measurement, but at least before the data analysis of the X-ray reflectance, the information about the composition of the sample is obtained from the characteristic X-ray peak on the fluorescent X-ray spectrum. Use it as a reference for calculating the refractive index. Also, in a storage device installed in the device or a CD
Information on density or crystal structure corresponding to compounds having various compositions recorded in a storage medium such as a ROM is made available. If there is information on the density, the refractive index is calculated by combining with the composition obtained from the characteristic X-ray. If there is information on the crystal structure, the density is calculated from it, combined with the composition obtained from the characteristic X-ray, the refractive index is calculated, and the Fourier analysis is performed. The above procedure is summarized in a flowchart and shown in FIG.

The feature of this system is that the spatial area of the fluorescent X-ray measurement is completely the same as that of the X-ray reflectance measurement. Therefore, a minute beam width of 5 to 100 μm using a beam condenser is used. It is more effective in part evaluation. Further, the smaller the incident angle, the more strongly the peak is the composition information closer to the surface. Therefore, the measurement can be performed while changing the incident angle at several points, and the information on the film structure can be obtained in advance by fluorescent X-ray measurement. deep.

Further, both the fluorescent X-ray measurement and the X-ray reflectance measurement were carried out using the same type of sample, and first, a calibration curve showing the correlation between the fluorescent X-ray peak intensity and the film thickness was obtained and stored in the device. After that, the film thickness is evaluated directly from the fluorescent X-ray spectroscopy result. When used to manage products on the line, the throughput can be increased by evaluating the film thickness only by the fluorescent X-ray evaluation, which is quickly evaluated after the calibration curve is obtained. A flowchart of this evaluation method is shown in FIG.

[Embodiment 10] A schematic view of this embodiment is shown in FIG.
1. The flowchart is shown in FIG.

Prior to the actual measurement, a dimming means is used to automatically check the angle θc at which the reflected light weakens to a predetermined intensity Ic. This survey measurement does not need to take a long integration time because it is sufficient if the approximate θc can be obtained. θ
The angle region of front and rear Δθ with c sandwiched is overlapped with and without the use of the dimming means. In the actual measurement, the dimming means is used to start the angular scanning from a region with a large reflection intensity, and when the angle reaches (θc-Δθ), the dimming means is automatically switched while the dimming means is used. Continue to measure and store both the strength and the strength when not in use until the angle becomes (θc + Δθ). Angle (θc +
After [Delta] [theta], the measurement is performed without using the dimming means.

After the measurement was completed, the measurement was performed by overlapping.
The average extinction ratio is determined with and without the ([theta] c- [Delta] [theta]) to ([theta] c + [Delta] [theta]) light extinguishing means, and the data on the high intensity side is corrected accordingly. For the overlap section, the weighted average of the data with light reduction means and the data without light reduction means is intensity-corrected. That is, at an angle close to (θc-Δθ), the weight of the data with the light reduction means is intensity-corrected, and the weight is increased. it can.

[Embodiment 11] A schematic diagram of this embodiment is shown in FIG.
3. The flow chart is shown in FIG.

When the dimming means is used to start angular scanning from a region having a large reflection intensity, and when the reflection intensity is reduced to a predetermined intensity I1 or less, the dimming means is used while automatically switching the dimming means. Both the intensity and the intensity when not used are measured and stored until the intensity when the dimming means is not used becomes equal to or lower than the predetermined intensity I2.

After the measurement is completed, the average extinction ratio is determined depending on whether or not there is a dimming means in the overlapped and measured section, and the data on the high intensity side is corrected accordingly. For the overlap section, the weighted average of the data with light reduction means and the data without light reduction means is intensity-corrected. That is, the correction can be smoothly performed by increasing the weight of the data with the light reduction means corrected at a small angle and increasing the weight of the data without the light reduction means at a large angle.

[Embodiment 12] A schematic diagram of this embodiment is shown in FIG.
Shown in.

Two filters A and B are provided so that they can be automatically switched in and out of the optical path. These are designed so that they can be independently switched in and out of the optical path.

Initially, both A and B were used for measurement, and when the X-ray intensity decreased to I1, only B filters were automatically and alternately attached and detached (first overlap section), and the filters were used. When the X-ray intensity decreases to I2 only with A, the measurement is performed using only the filter of A, and when the X-ray intensity decreases to I1 again, the measurement of the filter of A is automatically performed while alternately attaching and detaching (second Overlapped section), when the X-ray intensity decreases to I2 without a filter,
After that, measure without a filter.

In the intensity correction, first, the average extinction rate of the filter A is determined in the second overlap section as in the case of the eleventh embodiment, and this extinction rate is used to determine the high intensity area before the second overlap section. Is performed and the weighted average is used in the second overlap section. Next, in the first overlap section, the average extinction rate of the filter B is determined, and using this extinction rate, the intensity of the high-intensity region before the first overlap section is corrected to obtain the first overlap section. Correction is performed using the weighted average in the lap section.

The threshold intensities I1 and I2 have a relationship of I1≤I2, and the larger the difference, the narrower the overlap section. It is recommended to be able to set it flexibly according to the sample.

In the present embodiment, the example of the light-reducing means using two filters has been described. (Measure with dimming with filter C) → (Measure with dimming with filter D) → (Measure without filter) Even if the above steps (measure with dimming with filter A + B) → (Filter Measure with A) → (Measure without filter)
The present invention can be implemented.

Further, as shown in FIG. 16, it is preferable to prepare filters 4 and 5 having different extinction rates and perform switching by using a slide system or a revolver system.

[Embodiment 13] As shown in FIG. 17, two tapered neutral density filters 6 and 7 are combined, one is made to be slidable left and right by a stepping motor, and the other is vertically moved in synchronization with it. Slide it on. As a result, the filter thickness can be continuously changed. In FIG. 17, the filter film thickness is almost doubled between the dotted line position and the solid line position. The two filters have the same taper angle, and the filter surfaces are parallel to each other at the X-ray transmitting position.

By precisely controlling the filter to be slid to the left and right by the stepping motor, the multi-step intensity correction of the twelfth embodiment can be realized with an arbitrary attenuation rate and an arbitrary number of steps. At this time, in order to reduce the influence of the backlash of the stepping motor, it is preferable that the sliding direction at the time of setting is set to one direction, and when it is returned to the opposite direction, it is first returned to a large value and then adjusted.

[0073]

As described above, according to the present invention, the X-ray can be used to efficiently determine the film thickness and the refractive index or the density even if the film model, the film thickness of each layer and the film quality are unknown. A reflectance analyzer can be realized. In addition, there is no risk of contamination or deterioration, and the composition at the position where the X-ray reflectance is measured can be correctly evaluated by fluorescent X-ray analysis, enabling analysis of unknown samples. In addition, a calibration curve for obtaining the film thickness from the peak intensity of the fluorescent X-ray can be created with one device from the analysis results of the peak intensity of the fluorescent X-ray and the X-ray reflectance, and the fluorescent X-ray is accurately supported. Evaluation can be used to increase measurement throughput. Also,
By automatically switching the presence / absence of the dimming means and measuring the intensity in the predetermined angle area with and without the dimming means, it is possible to measure the intensity with high accuracy without backlash. Correction is possible. Further, the dynamic range can be further widened by using a multi-staged light-attenuating means or using a light-attenuating means capable of continuously switching the light-attenuating rate.

[Brief description of drawings]

FIG. 1 is a flowchart of the present invention.

FIG. 2 is a schematic view of a sample in which a two-layer thin film is formed on a substrate.

FIG. 3 shows an example in which the results of Fourier analysis are output side by side while changing the refractive index δ.

FIG. 4 is an example in which the results of Fourier analysis with the refractive index δ changed are displayed in contour lines.

FIG. 5 shows an example in which the results of Fourier analysis are displayed with peaks and ridges while changing the refractive index δ.

FIG. 6 shows a refractive index δ obtained by obtaining a film thickness t from the refractive index δ and frequency.
And an example of displaying the Fourier analysis result for the film thickness t.

FIG. 7 shows an example of displaying Fourier analysis results for density ρ and film thickness t.

FIG. 8 is a flowchart of an analysis procedure.

FIG. 9 is a flowchart of a quality control monitor on the line.

FIG. 10 is a conventional example of overlap measurement with / without a dimming unit.

FIG. 11 is an explanatory diagram of an overlap measuring method (1) with / without a dimming unit.

12 is a flow chart of the method of FIG.

FIG. 13 is an explanatory diagram of an overlap measuring method (2) with / without a dimming unit.

FIG. 14 is a flowchart of the method of FIG.

FIG. 15 is an example of overlapping measurement in which the dimming means is provided in two stages.

FIG. 16 shows an example of a multi-step dimming means.

FIG. 17 is a schematic view of a dimming unit capable of continuously varying the dimming rate of the present invention.

[Explanation of symbols]

1 ... Thin film 1, 2 ... Thin film 2, 3 ... Substrate, 4 ... Filters with different extinction rates, 5 ... Filters with different extinction rates, 6, 7 ... Extinction filters.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuo Kikuchi 3-9-12 Matsubara-cho, Akishima-shi, Tokyo Rigaku Denki Co., Ltd. Haijima factory (72) Inventor Takao Kibuchi 3--12, Matsubara-cho, Akishima-shi, Tokyo No. Rigaku Denki Co., Ltd. Haijima factory

Claims (31)

[Claims] 1. An apparatus for Fourier-analyzing an oscillating structure extracted from an X-ray reflectance pattern of a thin film sample, Fourier-analyzing the oscillating structure while swinging an estimated value of the refractive index of the thin film, and obtaining each refractive index. An X-ray reflectivity analyzer having a function of three-dimensionally displaying a Fourier transform intensity profile with respect to a refractive index and a frequency using the obtained Fourier analysis result. 2. An apparatus for Fourier-analyzing an oscillating structure extracted from an X-ray reflectance pattern of a thin film sample, Fourier-analyzing the oscillating structure while swinging an estimated value of the refractive index of the thin film, and obtaining each refractive index. An X-ray reflectivity analyzer having a function of displaying a Fourier transform intensity profile in contour lines with respect to a refractive index and a frequency using the obtained Fourier analysis result. 3. An apparatus for Fourier-analyzing an oscillating structure extracted from an X-ray reflectance pattern of a thin-film sample, Fourier-analyzing the oscillating structure while swinging an estimated value of the refractive index of the thin-film, and obtaining each refractive index. An X-ray reflectance analysis device having a function of mapping and displaying a Fourier transform intensity profile for each refractive index and frequency using the obtained Fourier analysis result. 4. An apparatus for Fourier-analyzing an oscillating structure extracted from an X-ray reflectance pattern of a thin film sample, Fourier-analyzing the oscillating structure while swinging an estimated value of the refractive index of the thin film, and obtaining each refractive index. An X-ray reflectance analysis device having a function of displaying peaks and ridges of a Fourier transform intensity profile for a refractive index and a frequency component using the obtained Fourier analysis result. 5. An apparatus for Fourier-analyzing an oscillating structure extracted from an X-ray reflectance pattern of a thin film sample, Fourier-analyzing the oscillating structure while swinging an estimated value of the refractive index of the thin film, and obtaining each refractive index. An X-ray reflectivity analyzer having a function of three-dimensionally displaying a Fourier transform intensity profile regarding a refractive index and a film thickness by using the obtained Fourier analysis result. 6. An apparatus for Fourier-analyzing an oscillating structure extracted from an X-ray reflectance pattern of a thin film sample, Fourier-analyzing the oscillating structure while swinging an estimated value of the refractive index of the thin film, and obtaining each refractive index. An X-ray reflectivity analysis apparatus having a function of displaying a Fourier transform intensity profile for the refractive index and the film thickness by contour lines using the obtained Fourier analysis result. 7. An apparatus for Fourier-analyzing an oscillating structure extracted from an X-ray reflectance pattern of a thin film sample, Fourier-analyzing the oscillating structure while swinging an estimated value of the refractive index of the thin film, and obtaining each refractive index. An X-ray reflectivity analysis apparatus having a function of mapping and displaying a Fourier transform intensity profile for each of the refractive index and the film thickness by using the obtained Fourier analysis result. 8. An apparatus for Fourier-analyzing an oscillating structure extracted from an X-ray reflectance pattern of a thin-film sample, Fourier-analyzing the oscillating structure while swinging an estimated value of the refractive index of the thin-film, and obtaining each refractive index. An X-ray reflectance analysis device having a function of displaying peaks and ridges of a Fourier transform intensity profile for a refractive index and a film thickness by using the obtained Fourier analysis result. 9. An apparatus for Fourier-analyzing a vibrational structure extracted from an X-ray reflectance pattern of a thin-film sample, Fourier-analyzing the vibrational structure while shaking the estimated value of the density of the thin-film, and obtaining each density. An X-ray reflectivity analysis apparatus having a function of three-dimensionally displaying a profile of Fourier transform intensity with respect to density and frequency using a Fourier analysis result. 10. An apparatus for Fourier-analyzing a vibrational structure extracted from an X-ray reflectance pattern of a thin-film sample, Fourier-analyzing the vibrational structure while swinging an estimated value of the density of the thin-film, and obtaining each density. An X having a function of displaying a Fourier transform intensity profile in contour lines with respect to density and frequency using the Fourier analysis result.
Line reflectance analyzer. 11. An apparatus for Fourier-analyzing a vibrational structure extracted from an X-ray reflectance pattern of a thin-film sample, Fourier-analyzing the vibrational structure while shaking an estimated value of the density of the thin-film, and obtaining each density. An X-ray reflectivity analyzing apparatus having a function of mapping and displaying a Fourier transform intensity profile for each density and frequency by color, using a Fourier analysis result. 12. An apparatus for Fourier-analyzing an oscillating structure extracted from an X-ray reflectance pattern of a thin-film sample, Fourier-analyzing the oscillating structure while swinging an estimated value of the density of the thin-film, and obtaining each density. An X-ray reflectivity analyzer having a function of displaying peaks and ridges of a Fourier transform intensity profile with respect to density and frequency using a Fourier analysis result. 13. An apparatus for Fourier-analyzing an oscillating structure extracted from an X-ray reflectance pattern of a thin-film sample, Fourier-analyzing the oscillating structure while swinging an estimated value of the density of the thin-film, and obtaining each density. An X-ray reflectivity analyzer having a function of three-dimensionally displaying a Fourier transform intensity profile for density and film thickness using a Fourier analysis result. 14. An apparatus for Fourier-analyzing an oscillating structure extracted from an X-ray reflectance pattern of a thin-film sample, Fourier-analyzing the oscillating structure while swinging an estimated value of the density of the thin-film, and obtaining each density. An X-ray reflectivity analyzer having a function of displaying a Fourier transform intensity profile in contour lines with respect to density and film thickness using a Fourier analysis result. 15. An apparatus for Fourier-analyzing an oscillating structure extracted from an X-ray reflectance pattern of a thin-film sample, Fourier-analyzing the oscillating structure while shaking an estimated value of the density of the thin-film, and obtaining each density. An X-ray reflectivity analyzer having a function of mapping and displaying a Fourier transform intensity profile for each of the density and the film thickness using a Fourier analysis result. 16. An apparatus for Fourier-analyzing a vibrational structure extracted from an X-ray reflectance pattern of a thin-film sample, Fourier-analyzing the vibrational structure while shaking an estimated value of the density of the thin-film, and obtaining each density. An X-ray reflectivity analyzer having a function of displaying peaks and ridgelines of a Fourier transform intensity profile for density and film thickness using a Fourier analysis result. 17. The X-ray reflectance analyzer according to any one of claims 1 to 16, wherein the mode for displaying the Fourier transform intensity is any one of refractive index and frequency, refractive index and film thickness, density and frequency, and density and film thickness. An X-ray reflectivity analysis device characterized by being capable of switching and using any of these combinations. 18. An X-ray reflectance analyzer according to any one of claims 5 to 8 or an X-ray reflectance analyzer according to any one of claims 13 to 16, wherein the Fourier transform intensity has a maximum value and the refractive index or density and film thickness. An X-ray reflectance analyzer having a function of listing out combinations of 19. An X-ray reflectance analyzer according to any one of claims 5 to 8 or an X-ray reflectance analyzer according to any one of claims 13 to 16, wherein the Fourier transform intensity has a maximum value and the refractive index or density and film thickness. , The product of each refractive index and film thickness, or each product of density and film thickness,
An X-ray reflectivity analyzer having a function of adding out some of the elements and listing out elements that are equal to other elements within a predetermined error range. 20. The X-ray reflectance analyzer according to any one of claims 5 to 8 or the X-ray reflectance analyzer according to any one of claims 13 to 16, wherein the Fourier transform intensity has a maximum value and a refractive index or a density and a film thickness. Of the combination of the refractive index and the film thickness, or the product of the density and the film thickness, and the refractive index or the density of the combination, are used as a judgment material to estimate the layer structure of the thin film. Characteristic X
Line reflectance analyzer. 21. An apparatus for analyzing an X-ray reflectance pattern of a thin film sample, comprising means for spectroscopically measuring fluorescent X-rays generated from the thin film by incident X-rays, and analyzing the composition of the thin film from the fluorescent X-ray spectrum. Then, the refractive index of the thin film is calculated from the obtained composition, and the vibration structure of the reflectance is subjected to Fourier analysis from the calculated value. 22. The X-ray reflectance analyzing apparatus according to claim 21, wherein the density of the thin film is read from the database of the storage medium mounted in the apparatus, or the crystal structure of the thin film is read to calculate the density. An X-ray reflectivity analyzer having a function of obtaining a refractive index of the thin film by using. 23. The X-ray reflectance analyzer according to claim 21, wherein the fluorescent X-ray spectroscopic measurement is performed at at least two X-ray incident angles, and the change of the fluorescent X-ray spectrum depending on the incident angle causes the outermost surface layer. An X-ray reflectance analysis device characterized by being able to distinguish the information of the internal layers. 24. The X-ray reflectance analyzer according to claim 21, wherein the incident X-ray has a beam width of 5 to 100 μm. 25. The X-ray reflectance analyzer according to claim 21, wherein the peak intensity in fluorescent X-ray spectroscopy measurement and the film thickness obtained by X-ray reflectance pattern analysis are at least 2
A database for three or more samples, and the film thickness is estimated by fluorescent X-ray spectrum measurement using the database.
Alternatively, an X-ray reflectance analysis device having a function of evaluating. 26. In an apparatus for analyzing an X-ray reflectance pattern of a thin film sample, an incident angle θ at which the X-ray reflected light intensity reaches a predetermined intensity is automatically determined, and the X-ray reflected light intensity is set to the predetermined intensity. In an incident angle region larger than the intensity, measurement is performed by using the dimming means, and in the incident angle region set in advance across the incident angle θ, the dimming means is automatically switched to reflect light reflected by the dimming means. Both the intensity and the reflected light intensity without using the light attenuating unit are measured, and the extinction ratio of the light attenuating unit is calculated from the measured value to correct the X-ray reflected light intensity on the high intensity side to obtain the X-ray. An X-ray reflectivity analyzing apparatus, characterized in that measurement is performed without using a dimming means in an incident angle region where reflected light intensity is small. 27. In an apparatus for analyzing an X-ray reflectance pattern of a thin film sample, a dimming means is used for measurement in an incident angle region where the X-ray reflected light intensity is large, and the incident angle becomes large. When the X-ray reflection intensity I1 is decreased to the second X-ray which is preset to be measured while automatically switching both the reflected light intensity using the dimming means and the reflected light intensity not using the dimming means. The X-ray reflected light intensity on the high intensity side is corrected by repeatedly calculating the light extinction ratio of the light attenuator from the measured value during this period until the reflected light intensity I2 is reached. An X-ray reflectivity analysis device, characterized in that measurement is performed without using a light-attenuating means. 28. The X according to claim 26 or 27.
An X-ray reflectance analyzing apparatus, wherein an attenuation filter that can be automatically inserted into an optical path is used as a light attenuating unit in the ray reflectance analyzing apparatus. 29. The X according to claim 26 or 27.
An X-ray reflectance analyzing apparatus, characterized in that, in the ray reflectance analyzing apparatus, light reducing means are arranged in multiple stages in an optical path, and intensity correction is performed in at least two stages. 30. The X according to claim 26 or 27.
An X-ray reflectance analyzing apparatus, characterized in that in the linear reflectance analyzing apparatus, a dimming unit having a variable dimming rate is arranged in an optical path, and intensity correction is performed in at least two stages. 31. The X-ray reflectance analyzer according to claim 29, wherein at least two tapered filters are combined and at least one of them is slid as a dimming means with variable extinction ratio. An X-ray reflectivity analyzer having a structure in which the thickness is continuously changed.