KR101166013B1 - X-ray reflectometry of thin film layers with enhanced accuracy - Google Patents

Abstract

The present invention relates to a method for inspecting a sample comprising a first layer having known reflective properties and a second layer formed on the first layer. The method includes directing radiation toward the surface of the sample to generate a reflected signal as a function of elevation angle to the surface and sensing the radiation reflected from the surface. Features due to the reflection of radiation from the first layer are identified in the reflected signal. This reflected signal is corrected corresponding to the identified feature and the known reflective properties of the first layer. The corrected reflected signal is analyzed to determine the properties of the second layer. Other improved test methods are also disclosed.

Reflective properties, first layer, second layer, sample, elevation, radiation, reflection signal

Description

X-RAY REFLECTOMETRY OF THIN FILM LAYERS WITH ENHANCED ACCURACY}

1 is a schematic side view of a system for X-ray reflection (XRR) measurement in accordance with an embodiment of the present invention.

2 is a schematic front view of a detector array configured for XRR in accordance with an embodiment of the invention.

3 is a schematic of an XRR measurement in accordance with an embodiment of the invention.

4 is a schematic diagram of an XRR measurement showing a method for obtaining an XRR spectrum having subpixel resolution, according to an embodiment of the present invention.

FIG. 5A is a schematic side view of the system of FIG. 1 showing an angle bounded by an X-ray beam in another configuration of shutter and sample in the system, in accordance with an embodiment of the present invention. FIG.

FIG. 5B is a schematic diagram of X-ray measurement results used to determine the zero angle for incidence of X-rays on a sample in the system shown in FIG. 5A, according to an embodiment of the invention. FIG.

6 is a schematic plan view of a cluster tool for fabricating semiconductor equipment, including a overhaul station in accordance with an embodiment of the present invention.

7 is a schematic side view of a semiconductor processing chamber with X-ray overhaul capability in accordance with an embodiment of the present invention.

The present invention relates generally to analyzers, and more particularly to thin film analysis instruments and methods using X-rays.

X-ray reflectometry (XRR) is a well-known technique for measuring the thickness, density and surface quality of a thin film layer deposited on a substrate. Conventional X-ray reflectometers are sold by many companies, including Technos (Osaka, Japan), Siemens (Munich, Germany), and Bede Scientific Instrument (Durham, UK). Such reflectometers typically operate by irradiating the sample with an X-ray beam to a light extent, close to the total external reflection angle of the sample material, ie at a small angle to the sample surface. Measuring the X-ray intensity reflected from the sample as a function of angle provides a pattern of interference fringes, which is analyzed to determine the characteristics of the film layer that produced the interference fringe pattern. X-ray intensity measurements are typically performed using a proportional counter or array detector, typically a position-sensitive detector such as a photodiode array or charge coupled device (CCD).

A method for measuring film thickness by analyzing X-ray data is described, for example, in U.S. Pat. 5,740,226, which is incorporated herein by reference. After measuring the X-ray reflectance as a function of angle, the average reflectance curve is fitted to the interference fringe spectrum. The mean curve is based on an equation representing the attenuation, background value and surface roughness of the film. The fitted average reflectance curve is then used to extract the vibration component of the interference fringe spectrum. Fourier transform this component to find the film thickness.

Koppel, US Pat. No. 5,619,548, which is incorporated herein by reference, describes an X-ray thickness gauge based on reflectometry. A curved reflective monochromator is used to focus the X-rays on the surface of the sample. Position-sensitive detectors, such as photodiode detector arrays, respond to X-rays reflected from the surface and produce an intensity signal as a function of the angle of reflection. Angle-dependent signals are analyzed to determine the structural properties of the thin film layer on the sample, including thickness, density, and surface roughness.

US Pat. No. 5,923,720 to Barton et al., Which is incorporated herein by reference, also describes an X-ray spectrometer based on a curved crystalline monochromator. Monochromators have the form of tapered algebraic spirals, which are described as achieving finer focal spots on the sample surface than prior art monochromators. X-rays reflected or diffracted from the sample surface are received by the position-sensitive detector.

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Another common method of X-ray reflection measurement is described, for example, in the invention Naudon et al., Journal of Applied Crystallography 22 (1989), p. 460, which is incorporated by reference herein. Novel Apparatus for Grazing X-Ray Reflectometry ". The divergent beam of X-rays is directed towards the surface of the sample at grazing incidence and the detector opposite the X-ray source collects the reflected X-rays. The knife edge is placed close to the sample surface directly above the measurement position to block the primary X-ray beam. The monochromator between the sample and the detector (rather than between the source and the sample, as in US Pat. No. 5,619,548) selects the wavelength of the reflected X-ray beam that reaches the detector.

XRR is also in situ in an attachment furnace, for example to inspect a thin film layer in production on a semiconductor wafer, as described by Hayashi et al. In US patent application publication US 2001/0043668, which is incorporated by reference herein in its entirety. Can be used. The furnace is provided with X-ray incidence and extraction windows on its sidewalls. The substrate with the thin film attached thereto was irradiated through the incident window, and the X-rays reflected from the substrate were sensed through the X-ray extraction window.

Embodiments of the present invention provide a method and system for performing XRR measurements with improved precision. These methods and systems are advantageous for analyzing thin film layers, and in particular for characterizing low density materials such as low k porous dielectrics deposited on high density underlying layers such as silicon wafers.

In some embodiments of the present invention, the angular scale of the XRR fringe pattern generated by the thin film layer is corrected based on the known reflective properties of the underlying layer. The structure of the fringe pattern depends on the density, thickness and other properties of the thin film, but especially when the density of the thin film layer is less than the density of the underlying layer, the pattern is distinct from the critical angle for total external reflection from the underlying layer. It may also include shoulders. This critical angle, in turn, is determined by the composition and density of the underlying layer. Once the parameters of the underlying layer are known (eg, when the underlying layer is a silicon wafer substrate), the angular scale of the XRR fringe pattern can be accurately corrected based on the position of the shoulder.

In another embodiment of the invention, an array of X-ray detector elements is used to measure the XRR fringe pattern at sub-pixel resolution. For this purpose, the sample is irradiated by a converging X-ray beam. As the array is positioned and oriented, the elements of the array analyze the radiation reflected from the sample along an axis perpendicular to the plane of the sample. The array is then moved along the axis in increments less than the pitch of the array, and the measurement is repeated. Preferably, the increase is equal to the fraction of the pitch of the array (pitch / n, n is an integer) and the measurement is repeated at different locations of the array along the axis. XRR measurements made at different locations are usually combined by interpolating measurements taken at different increments to obtain fringe spectra with improved resolution.

Although the embodiments of the invention described herein are primarily for improved X-ray measurement for thin films and especially films formed on semiconductor wafers, the principles of the invention are based on other forms of radiation based as well as other applications of X-ray reflection and scattering. Can be used for analysis.

Therefore, according to an embodiment of the present invention,

In the inspection method of a sample comprising a first layer having a known reflective property and a second layer formed on the first layer,                     

Directing the radiation towards the surface of the sample;

Sensing radiation reflected from the surface to produce a reflected signal as a function of elevation angle to the surface;

Identifying features in the reflected signal due to the reflection of radiation from the first layer;

Correcting the reflected signal in accordance with known reflection characteristics and identified features of the first layer; And

 And analyzing the corrected reflection signal to determine the characteristics of the second layer.

Typically, the radiation comprises X-rays and sensing the radiation includes receiving radiation in an array of detector elements having an array axis perpendicular to the surface.

In the disclosed embodiment, identifying the feature comprises finding the position of the shoulder with a reflected signal corresponding to a critical angle with respect to the entire external reflection line from the first layer. Typically, correcting the reflected signal includes comparing the position of the shoulder against a known value of the critical angle determined by the known density of the first layer. Correcting the reflected signal includes finding a zero angle in the angular scale of the reflected signal based on known values of the position of the shoulder and the critical angle.

In some embodiments, when the critical angle for the entire external reflection line from the first layer is the first critical angle, analyzing the corrected reflection signal determines the correction value of the second critical angle for the entire external reflection line from the second layer. It includes a step. Typically, the first and second layers each have a first density and a second density, and analyzing the corrected reflected signal includes evaluating the second density based on the correction value of the second critical angle. In this case, the second density is smaller than the first density. In one embodiment, the first layer comprises silicon and the second layer comprises a porous dielectric.

According to an embodiment of the present invention, an inspection apparatus for a sample comprising a first layer having a known reflective property and a second layer formed on the first layer, wherein the X-ray is directed to the surface of the sample. Radiation source;

A detector assembly arranged to sense radiation reflected from the surface to produce a reflected signal as a function of elevation angle to the surface; And

Identifying features of the reflected signal due to reflection of radiation from the first layer, correcting the reflected signal in accordance with known reflection characteristics and identified features of the first layer, and analyzing the corrected reflected signals By determining the characteristic, a signal processor coupled to receive and process the reflected signal is provided.

According to an embodiment of the present invention, in the apparatus for inspecting a sample,

The device is:

A radiation source suitable for guiding X-rays towards the surface of the sample; And

A detector assembly,                     

The detector assembly is:

A detector element array arranged along an array axis generally perpendicular to the surface and separated from each other at a predetermined pitch and receiving X-rays reflected from the surface and generating a signal in response to the received radiation; And

A moving element coupled to move the detector element array in a direction parallel to the array axis between at least the first and second positions separated from each other by an increment that is not an integer multiple of the pitch; And

An apparatus is provided comprising a signal processor coupled to couple a signal generated by a detector assembly at at least a first position and a second position to determine an X-ray reflectance of the surface as a function of elevation angle to the surface. .

Typically, the signal processor is a device characterized in that it is suitable for interleaving a signal generated by the detector assembly in at least a first position and a second position to determine an X-ray reflectance of the surface.

In the disclosed embodiment, the increase is characterized by less than half the pitch.

Typically, the array comprises a linear array and the detector element is a device characterized by having a lateral dimension greater than one pitch of the array perpendicular to the array axis. As an alternative, the array comprises a detector element of a two-dimensional matrix, and the detector assembly is suitable for storing the detector element in each column of the array along a direction perpendicular to the array axis.

According to the present invention,                     

Guiding X-ray towards the surface of the sample;

Constructing an array of detector elements separated from one another at a predetermined pitch to receive X-rays reflected from the surface while resolving received radiation along an array axis generally perpendicular to the surface;

Moving the array of detector elements in a direction parallel to the array axis between at least the first and second positions separated from each other by an increment that is not an integer multiple of the pitch;

Receiving at least a first signal and a second signal respectively generated by the detector element in at least a first position and a second position in response to the received X-rays; And

Combining at least a first signal and a second signal to determine an X-ray reflectivity of the surface as a function of elevation angle to the surface; a method of inspecting a sample is provided.

According to the present invention,

A cluster tool for producing microelectronics,

The tool is:

A deposition station suitable for depositing a thin film layer on an underlying layer having known reflective properties on the surface of the semiconductor wafer; And

Includes an inspection station,

The inspection station is:

A radiation source suitable for guiding X-rays towards the surface of the wafer;

A detector assembly arranged to sense radiation reflected from the surface to generate a reflected signal as a function of elevation angle to the surface; And

Receiving and processing the reflected signal by identifying the characteristic of the reflected signal due to the reflection of radiation from the underlying layer and correcting the reflected signal in response to the identified characteristic of the underlying layer and known reflective properties, A tool is provided that includes a signal processor coupled to analyze a corrected reflected signal to characterize the thin film layer deposited by the deposition station.

According to the present invention,

A production chamber suitable for containing a semiconductor wafer;

A deposition apparatus suitable for depositing a thin film layer on an underlying layer having known reflection properties on the surface of the semiconductor wafer in the chamber;

A radiation source suitable for guiding X-rays towards the surface of the semiconductor wafer within the chamber;

A detector assembly arranged to sense radiation reflected from the surface to generate a reflected signal as a function of elevation angle to the surface; And

Receiving and processing the reflected signal by identifying the characteristic of the reflected signal due to the reflection of radiation from the underlying layer and correcting the reflected signal in response to the identified characteristic of the underlying layer and known reflective properties, An apparatus for producing a microelectronic device is provided, comprising a signal processor coupled to analyze a corrected reflected signal to determine a feature of the thin film layer deposited by the deposition device.

According to the present invention,

A cluster tool for producing microelectronics,

The tool is:

A deposition station suitable for depositing a thin film layer on a surface of a semiconductor wafer; And

Includes an inspection station,

The inspection station is:

A radiation source suitable for guiding X-rays towards the surface of the wafer;

Detector assembly; And

A signal processor coupled to couple a signal generated by the detector assembly at at least a first position and a second position to determine an X-ray reflectance of the thin film layer as a function of elevation angle to the surface,

The detector assembly is:

A detector element array arranged along an array axis perpendicular to the surface and separated from each other at a predetermined pitch and operative to receive X-rays reflected from the surface and generate a signal in response to the received radiation; And

A tool is provided that includes a moving element connected to move the array of detector elements in a direction parallel to the array axis between at least the first and second positions separated from each other by an increment that is not an integer multiple of the pitch. .

According to the present invention,

An apparatus for producing microelectronics, the apparatus comprising:

The device is:

A production chamber suitable for containing a semiconductor wafer;

In a chamber, a deposition apparatus suitable for depositing a thin film layer on a surface of a semiconductor wafer;

A radiation source suitable for guiding X-rays towards the surface of the semiconductor wafer within the chamber;

Detector assembly; And

A signal processor coupled to couple a signal generated by the detector assembly at at least a first position and a second position to determine an X-ray reflectance of the thin film layer as a function of elevation angle to the surface,

The detector assembly is:

A detector element array arranged along an array axis perpendicular to the surface and separated from each other at a predetermined pitch and operative to receive X-rays reflected from the surface and generate a signal in response to the received radiation; And

An apparatus is provided comprising a moving element coupled to move the array of detector elements in a direction parallel to the array axis between at least first and second positions separated from each other by increments other than an integer multiple of the pitch. .

According to the present invention,

Directing radiation of the first predetermined position lobe towards the radiation sensor at a second predetermined position;

While the shutter is positioned to block radiation at a predetermined blocking angle, detecting radiation incident directly on the radiation sensor from the radiation source to generate a first direct signal as a function of elevation;

While the shutter is positioned so as not to block radiation at a predetermined blocking angle, detecting radiation directly incident on the radiation sensor from the radiation source to generate a second direct signal as a function of elevation;

Introducing a sample between a radiation source at a first predetermined location and a radiation sensor at a second predetermined location such that radiation is incident on the surface of the sample;

While the shutter is positioned to block radiation at a predetermined blocking angle, detecting radiation reflected from the surface of the sample onto the radiation sensor to generate a first reflected signal as a function of elevation;

While the shutter is positioned so as not to block radiation at a predetermined blocking angle, detecting radiation reflected from the surface of the sample onto the radiation sensor to generate a second reflected signal as a function of elevation; And

Comparing a second ratio between the first reflected signal and the second reflected signal to a first ratio between the first direct signal and the second direct signal to find an elevation of the tangent to the surface; A method of testing a sample is provided.

Typically, the method includes analyzing the first and second reflected signals to measure the properties of the thin film layer on the sample surface.

In the disclosed embodiment, comparing the first ratio and the second ratio comprises finding a first elevation with a first ratio having a given value and a second elevation with a second ratio having a given value, the first and second elevation angles. And measuring the elevation angle of the tangent to the surface being the average of. As an alternative, the method below includes obtaining a difference between the first and second elevation angles to measure the minimum elevation angle at which the shutter blocks the radiation.

According to the present invention,

In the sample inspection device:

A radiation source at a first predetermined location suitable for generating radiation;

A positionable shutter to block radiation at a predetermined blocking angle;

A moving stage configured to position the sample such that radiation generated by the radiation source is incident on the surface of the sample;

The radiation sensor in a second predetermined position suitable for sensing radiation to generate a signal responsive to radiation incident on the radiation sensor as a function of elevation angle;

A signal processor coupled to compare a first ratio between the first direct signal and the second direct signal and a second ratio between the first reflected signal and the second reflected signal to find an elevation of the tangent to the surface; ,

The signal is:                     

A first direct signal responsive to radiation incident directly on the radiation sensor from the radiation source while the shutter is positioned to block radiation at a predetermined blocking angle;

A second direct signal responsive to radiation directly incident on the radiation sensor from the radiation source while the shutter is positioned to not block radiation at a predetermined blocking angle;

A first reflected signal responsive to radiation reflected from the surface of the sample to the radiation sensor while the shutter is positioned to block radiation at a predetermined blocking angle;

And a second reflected signal responsive to radiation reflected from the surface of the sample to the radiation sensor while the shutter is positioned to not block radiation at a predetermined blocking angle.

The terms first and second are used arbitrarily in the claims and in the claims. Thus, for example, these terms do not necessarily reflect the actual order in which the aforementioned sings are received.

The invention will become apparent from the accompanying drawings and the description.

(Example)

Reference is now made to FIG. 1, which is a schematic side view of a system 20 for X-ray reflectometry (XRR) in accordance with an embodiment of the present invention. System 20 is similar to the XRR system described in US Pat. No. 6,512,814 mentioned above, with the features and capabilities described herein being added.

A sample 22, such as a semiconductor wafer, to be evaluated by the system 20 is mounted above the motion stage 24 and allows for precise adjustment of its position and orientation. An X-ray tube with an X-ray source 26, typically an appropriate monochromatizing lens (not shown), illuminates a small area 28 above the sample 22. For example, an XTF5011 X-ray tube from Oxford Instruments (Scotts Valley, California) can be used for this purpose. The lens focuses radiation from the X-ray tube onto the area 28 with a converging beam 27. Many other optical configurations that can be used in the source 26 are described in US Pat. No. 6,381,303, the disclosure of which is incorporated herein by reference. For example, the lens may comprise a curved crystal monochromator, such as Doubly-Bent Focusing Crystal Optics from XOS Inc., of Albany, New York. Other suitable lenses are described in US Pat. Nos. 5,619,548 and 5,923,720, above. More possible optical configurations will be apparent to those skilled in the art. Typical X-ray energy for reflectometry and dispersion measurements in system 20 is about 8.05 KeV (CuKa1). Alternatively, other energies such as 5.4 KeV (CrKa1) may be used.

The dynamic knife edge 36 and the shutter 38 are used to limit the angular range of the incident beam 27 of the X-ray in the vertical (ie, perpendicular to the plane of the sample 22), while slit 39 Can be used to limit the beam horizontally. The knife edge, shutter and slit together act as a shutter assembly to adjust the transverse dimension of the beam 27. The configuration of the shutter assembly in FIG. 1 is shown by way of example, and alternative arrangements of the X-ray lens for adjusting the transverse dimension of the beam 27 in the manner described below will be apparent to those skilled in the art. It is considered to be in the range of.

The use of knife edge 36 and shutter 38 in XRR measurements is described in detail in US Pat. No. 6,512,814. Briefly, for optimal detection of low-angle reflections near 0 °, the shutter 38 retracts out of the range of the incident beam 27, while the knife edge 36 is located above the area 28 and the beam It is lowered to reduce the effective vertical cross-sectional area. As a result, the lateral dimension of the X-ray spot incident on the area 28 is reduced. On the other hand, for effective detection of weaker, high-angle reflections, the knife edge 36 withdraws from the beam 27, while the shutter 38 is positioned to delete the low-angle portion of the beam. (Alternatively, the shutter can be positioned to erase the low-angle portion of the reflective beam 29.) In this way, only the high-angle reflections from the sample 22 reach the detector array and the strong low Each reflection does not reach, thus enhancing the signal / background ratio of the high-angle measurement. During the XRR measurement, the slit 39 is typically wide open to allow the entire cone of converging lines and thus increase the signal / noise ratio of the reflectivity measurement.

The reflected beam 29 of X-rays from the sample 22 is collected by the detector assembly 30. Typically, for XRR, the assembly 30 is reflected over a range of reflection angles in the vertical (rising-Φ) direction between about 0 ° and 3 °, both below and above the critical angle of the sample relative to the total external reflection. Collect X-rays. (For clarity of illustration, the angle shown in the figures is exaggerated, as the source 26 and detector assembly 30 are raised above the plane of the sample 22 in FIG. 1).

Assembly 30 includes a detector array 32, such as a CCD array, as described below. Although for the sake of simplicity of illustration, only a single row of detector elements are shown, with a relatively small number of detector elements, in general, the array 32 is arranged in either a linear array or a matrix (two-dimensional) array. It contains a larger number of elements. Assembly 30 may include any suitable type of moving element 33 known in the art to position and align array 32 relative to sample 22. Assembly 30 includes a window 34 made of a suitable X-ray transmissive material, such as beryllium, spaced in front of the detector array between the array and the sample. More details of the operation of the array 32 are described below with reference to FIG. 2.

Signal processor 40 analyzes the output of assembly 30 to determine the distribution 42 of X-ray photon flow reflected from sample 22 as a function of angle at a given energy or over a range of energies. Typically, the sample 22 has a thin film surface layer, such as one or more thin film films, in the region 28, so that the distribution 42 as a function of elevation angle has an interference effect in the X-ray wavelength reflected from the interference between the layers. It shows a structure that vibrates due to. The processor 40 analyzes the characteristics of each distribution using the analytical methods described below to determine the characteristics of the surface layer of one or more samples, such as thickness, density and surface quality of the layer.

2 is a front view of an array 32 in accordance with an embodiment of the present invention. The array 32 is shown in this figure to include a single row of detector elements 46 with array axes connected along an axis perpendicular to the plane of the sample 22. Element 46 has a high aspect ratio. That is, their width in the direction across the array axis is substantially greater than their height along the axis. Since the array 32 can collect X-ray photons over a relatively large area for each angular increase along the array axis, high aspect ratios are useful for improving the signal / noise ratio of the system 20. However, the width of the element 46 shown in this figure is merely exemplary, and the principles of the present invention may be applied using smaller or larger aspect ratio elements depending on the application needs and availability of suitable detector equipment. . As pointed out above, the array 32 includes one of a linear CCD array or a matrix array such as a model S7032-1008 array produced by Hamamatsu, Hamamatsu, Japan. The array contains 1044 × 256 pixels with a total size of 25.4 × 6 mm. It can be operated in a pre-binding manner using special hardware supplied for this purpose by Hamamatsu, so that in each row of the array, multiple detector elements effectively act as single elements with high aspect ratios. In this case, although the array 32 physically comprises a two-dimensional matrix of detector elements, as shown in FIG. 2, the array functionally takes the form of a single line of detector elements.
Alternatively, array 32 includes an array of PIN diodes with suitable readout circuitry that may include integrated processing electronics as described in US Pat. No. 6,389,102, the disclosure of which is incorporated herein by reference. can do. The patent also describes masking that can be applied to improve the detection characteristics of the array and the alternative features of the array, including the various geometrical phases (1- or 2-dimensional) of the array. This feature is also applicable to the assembly 30 of the present patent application. In any situation, this detector type is described herein as illustrative, and any suitable type, width and number of detectors may be used.

In one aspect of the invention, for example, the array 32 described in FIG. 2 is moved in the Z-direction by a small increase using the moving element 33 (FIG. 1). Increments in the Z-direction, which are half the array pitch, ie two vertical positions 45 and 47 spaced apart by one half of the distance between the centers of the detector elements 46 are shown. (Although positions 45 and 47 are shown to be horizontally offset in FIG. 2, the horizontal offset is used only for clarity of description in this figure and is not necessary or desired in the XRR measurement.) Each position 45 and 47 Source 26 is activated, and assembly 30 captures X-rays reflected from sample 22 as an action of elevation. Assembly 30 may be operated in this manner to capture X-rays above two different horizontal positions, typically with a smaller Z-direction increase between positions. For example, three different positions separated by 1/3 array pitch may be used.

The signal generated by the assembly 30 at each different horizontal position is input to the processor 40 which combines read signals made at different positions into a single spectrum. Essentially, the processor creates a "virtual array" with a more precise resolution than the actual physical array 32. For example, signals in a virtual array can be derived by simply interleaving read signals made at different array locations. Therefore, for each "virtual pixel" in the virtual array, the processor 40 alternates from one virtual pixel to the next virtual pixel among the readout signals made at the different measurement positions, and at the corresponding position in one actual measurement. Select the measured value of the pixel.

In other terms, the following read pixel readout signal is made at three consecutive positions in the array:

Position 1: R11, R21, R31, R41, ...

Position 2: R12, R22, R32, R42, ...

Position 3: R13, R23, R33, R43, ...

Then, in virtual pixels separated by one third of the actual array pitch, the resulting virtual array contains the following values:

R11, R12, R13, R21, R22, R23, R31, R32, R33, R41, ...

Alternatively, other methods, such as signal differentials or signal sums of those read at different array locations, may be used to extract the XRR information from individual measurements, prior to combining, or to select the actual measurement results to be used at each pixel of the virtual array. Can be used.

The above-mentioned resolution improvement technique is particularly useful when the XRR spectrum has a precise structure with high spatial frequency, so the fringe separation is comparable or smaller than the array pitch. Alternatively, if the XRR spectrum is strong enough and the fringes are well separated, it may be sufficient to measure the XRR signal at a single vertical position, such as position 45, to extract the acceptable spectrum.

3 and 4 are schematic diagrams of XRR measurements using system 20, according to one embodiment of the invention. As noted above, this kind of configuration can be generated by using signals received at a single vertical position of array 32 or by combining signals from two or more vertical positions. The configuration of FIG. 3 shows the intensity of the reflected X-rays received by the array 32 at a single vertical position, as a function of elevation, using Cu Kα (8.05 KeV) from the source 26. 4, which will be described below, shows the result of combining signals captured at a plurality of different vertical positions of the array.

로 주어지고, 여기서 초점 거리는 초점 영역(28)에서 어레이(32)까지의 거리이다. 대안으로 또는 부가적으로, 각 스케일은, 상기한 미국 특허 출원 제 10/313,280을 사용하여, φ2에서의 쇼울더부에 기초하여 그러나 어레이 피치 및 초점 거리를 참조하지 않고, 절대적으로 교정될 수 있다.The upper curve 50 shows the reflectance measured from the pure silicon wafer, while the lower curve 52 shows the reflectance from the wafer on which the low-k porous dielectric film was formed. Both curves have shoulder portions at an angle indicated by phi 2 in the figure which is slightly greater than 0.2 °. This angle corresponds to the critical angle for the total external reflectivity of the silicon. More specifically, for a standard silicon wafer with a density of 2.33 g / cm ³ , the critical angle at 8.05 KeV is 0.227 °. Thus, if the position of the shoulder portion is found at φ2, by simply returning back to the left of φ2 by 0.227 °, the zero point can be accurately determined on the (horizontal) angular scale of the spectrum of FIG. In the stages for each detector element 46, the scaling factor of each scale is

Where the focal length is the distance from the focal region 28 to the array 32. Alternatively or additionally, each scale can be absolutely corrected based on the shoulder portion at φ2 but without reference to the array pitch and focal length, using US Patent Application No. 10 / 313,280, supra.

Above the critical angle, the curve 52 shows a vibrating structure, mainly due to reflections from the upper and lower surfaces of the low-k film. The period and amplitude of these vibrations can be analyzed to determine the surface quality and thickness of the low-k film and possibly other thin film layers below it on the wafer. For example, a fast Fourier transform can be used to extract the appropriate vibration characteristics. Alternatively, parametric curve fitting can be used to determine more accurate film parameters. A method for analyzing an XRR signal, such as curve 52, is described in more detail in US Pat. No. 6,512,814, above.

The critical angle and the position of the shoulder portion of the reflectance curve are mainly determined by the density of the material on which the X-rays are reflected. The porous, low-k dielectric layer deposited on the wafer has a significantly lower density than the silicon substrate, and the critical angle of the porous layer is significantly smaller than the silicon below it. Thus, another shoulder portion appears in the curve 52 at a smaller angle marked in the figure as φ1 corresponding to the critical angle of the porous layer. The exact value of φ1 can be determined from the calibration of each scale described above, using the known value of φ2. Processor 40 can then more accurately determine the overall density of the porous material based on the calibrated value of φ1. Since the net density of the dielectric material (without holes) is typically known, the total pore density per unit volume of the porous layer is determined between the known net density of the dielectric material and the estimated total density of the porous layer, based on the measured value of φ1. Can be inferred by the difference.

4 shows the intensity of reflected X-rays received by the array 32 as a function of elevation, showing the result of combining a plurality of measurements made at different vertical positions of the array. Each scale in this figure is enlarged as compared with that in FIG. Unprocessed curve 54 shows typical measurements made at a single vertical position in array 32. The combined curve 56 shows the results obtained by five measurements taken at different vertical positions of the array, which are incremented in the Z direction by an array pitch of 1/5 and offset from each other. The pitch of the array is such that the flared angle between successive detector elements 46 is about 0.004 °.

As shown in curve 56, the period of the vibration pattern of the reflected radiation varies between about 0.007 ° and about 0.010 °, which is close to the Nyquist limit of array 32. Thus, curve 54 fails to capture a portion of the actual vibration structure that appears in curve 56, and reproduces another portion of the structure with poor fidelity. On the other hand, when a plurality of measurements are combined, part of the vibration structure lost in curve 54 is successfully captured at the other measurements. As a result, the effective resolution of the array 32 is improved, as shown by the curve 56 of the array 32. The improvement obtained in this manner allows for a more accurate resolution than the resolution of the X-ray optics used to cast the vibration pattern on the array 32. As mentioned above, the theoretical model is fitted to curve 56 to determine parameters such as the surface quality and thickness of the surface layer on sample 22. Since the XRR signal is inherently complex and exhibits nonlinear frequency variation as a function of angle, the added data points obtained by shifting the array in the manner described above are useful for improving the fit and thus extracting more accurate values of the surface layer parameters. .

In accordance with one embodiment of the present invention, reference is now made to FIGS. 5A and 5B, which schematically illustrate a method of determining the zero angle of a sample 22. FIG. 5A is a side schematic view of system 20 showing the angle of incidence on array 32 and each spread of the X-ray beam generated by source 26 at different system conditions. Each characteristic of the beam detected by the array 32 under these different conditions is used to determine the zero angle of the sample 22. The term "zero angle" within this context is used to indicate the angle of tangency to the surface of the sample 22 at the point of incidence of the X-ray beam on the sample. This zero angle is equivalent to the aforementioned zero point in the spectrum shown in FIG. 3. However, unlike the method described above for finding the zero point in this spectrum, the method described in FIGS. 5A and 5B does not depend on the layer structure of any particular sort on the sample 22. The zero angle is generated by the resolution enhancement technique described above by identifying the detector elements of the array 32 aligned with the tangent to the sample 22 (or by finding the vertical pixels aligned with this tangent). In a virtual array).

5A shows four different beam configurations.

As shown in the figure, the narrowly reflected beam 55 incident on the array 32 when the sample 22 is in position and the shutter 38 is positioned to cut off the row angular portion of the beam. ).

The light reflection beam 57 which broadly extends downward with respect to the zero angle of the sample 2 when the shutter 38 escapes from the beam.

Narrow incident on the array 32 when the shutter 38 is removed from the X-ray beam path (so that there is no reflected beam) and once again positioned to cut off the low angle portion of the beam. Direct beam 58.

When both the shutter and the sample are removed from the X-ray beam, the light-integrated beam 59 extends upward with respect to the zero angle of the beam 57 and usually even beyond this zero angle.

It should be noted that near zero angle, the signal captured by the array 37 by the beam 57 does not have a sharp cutoff, but is not completely smooth but gradually increases. (For the sake of simplicity, this gradual increase is not shown in FIG. 3) Therefore, it is difficult to determine the zero angle only based on this signal.

5B is a schematic plot of the results of the measurements made by the array 32 under radiation by beams 55, 57, 58, 50. The result is calculated for each pixel on the horizontal (each) axis as RATIO = I _NARROW / I _BROAD , the ratio of the intensity values of the pixels due to one of the narrow beams to the value due to the corresponding one of the broad beams. For the elevation angle below the zero angle, the left branch 61 of the plot plots each pixel value measured when the beam 58 is incident on the array 32 for the value measured when the beam 59 is incident. It is generated by calculating the ratio of. The right branch 63 for the elevation angle of the zero angle is given by the ratio of each pixel value measured when the beam 55 is incident on the array to the value measured when the beam 57 is incident.

As shown in FIG. 5B, the ratio for the positive and negative angles is zero near zero angle, because the shutter 38 cuts the beams 55 and 58 in the angular range. The ratio increases above zero at the cut-on angle, roughly corresponding to the angle at which the shutter 38 intercepts the X-ray beam, and gradually increases to a value that is about 1 away from the shutter edge. Branches 61 and 63 tend to be flat curves because local variations in intensity values due to narrow beams are typically canceled by corresponding variations in intensity values due to broad beams. Therefore, the zero angle can be accurately known by taking the average angle between the 50 percent points 65 (where the intensity ratio is 0.5). Alternatively, the curve fitting procedure is applied to branches 61 and 63, and the fitting parameter can be used to find the zero angle. The angular position of the shutter 38 is given as half of the angular distance between the points 65. As a further alternative, curve 63 is mirrored around a point on the horizontal axis to overlap with curve 61. Mirroring points that give the best overlap between the two curves are identified at zero angle.

The methods illustrated by FIGS. 5A and 5B can be used to find the zero angle at any point on the surface of the sample 22, regardless of the presence of some type of surface on the sample and the nature of the sample. This method for finding the zero angle is particularly useful in X-ray reflectometers of semiconductor wafers, for example, which tend to bend, so the zero angle varies over the surface of the wafer. This method is effective even when the incident X-ray beam is not uniform, and is also independent of any angular fluctuations in the reflected beam (as long as the reflectance fluctuates continuously as a function of angle). This method can be combined with the resolution enhancement method described above with reference to FIGS. 2-4 in which signals are obtained at different locations in the array 32 to determine the zero angle with greater accuracy.

Another advantage of the method is that it can be performed in cooperation with actual XRR measurements without substantially interrupting the measurement procedure. Measurements for the direct beams 58 and 59 may be made whenever the sample 22 is not in the system 20, between the measurements of the sample 22 typically different. For example, if the surface layer density of the sample is greater than about 1.5 g / cm 3, the angular range between about 0.15 ° and 4 ° can be useful for XRR measurements, while the angular range between 0 ° and 0.15 ° can be used for zero angle calibration. have.

In order to obtain the data used to create the branch 63, for example, the shutter 38 proceeds to cut a small angle of the X-ray beam of less than about 0.1, and the reflected signal is exposed to exposure of about 1-2 seconds. Obtained from array 32 over time. The shutter is then retracted and an additional reflected signal is obtained from the array. The signal is normalized in proportion to the ratio of the exposure duration at the two shutter positions. The ratio of the normalized curve is calculated to find branch 63. Similar procedures are used to create the branch 63.

6 is a schematic plan view of a cluster tool 70 for use in manufacturing semiconductor devices in accordance with an embodiment of the present invention. The cluster tool includes a plurality of stations, including a deposition station 72, an inspection station 74, and other stations 76 known in the art as cleaning stations for depositing thin films on semiconductor wafers 77. Included. The inspection station 74 is constructed and operates in a manner similar to the system 20 as described above. The robot 78 transfers the wafer 77 to the stations 72, 74, 76,... Under the control of the system controller 80. The operation of the tool 70 can be controlled and monitored by an operator using a workstation 82 connected to the controller 80.

Inspection station 74 is used to perform X-ray inspection of the wafer by XRR before and after a step selected in the production process performed by deposition station 72 and another station in tool 72. In one embodiment, deposition station 72 is used to make a porous thin film, such as a porous low-k electric layer, on wafer 77. Such an apparatus, using the controller 80 and possibly the workstation 82, enables convenient correction and evaluation of process parameters and early detection of process deviations in wafer production. The above technique of finding the zero angle and further enhancing the detection solution can be used at station 74 as well.

7 is a schematic side view of a system 90 for semiconductor wafer assembly and inspection in place, in accordance with another embodiment of the present invention. The system 90 includes a vacuum chamber 92, a vacuum chamber 92, and a deposition apparatus 94, to make a thin film on the wafer 77, as known in the prior art. The wafer is mounted to the motion stage 24 in the chamber 92. The chamber typically comprises an X-ray window 96, which is of the type disclosed in the above-mentioned patent application publication US 2001/0043668 A1. The shutters, knife edges and slits shown in FIG. 1 are missing in FIG. 7 for simplicity, but typically this kind of element is integrated into chamber 92 or in source 26.

X-rays reflected from the area 28 are received by the array at the detection assembly 30 through another one of the windows 96. Processor 40 receives a signal from detector assembly 30 and processes the signal to examine the properties of the thin film layer being fabricated in chamber 92. The results of this inspection can be used to control the deposition apparatus 94 such that the film produced by the system 90 has the desired properties, such as thickness, density porosity, and the like. The above technique for finding the zero angle and enhancing the detection solution can also be used in the chamber 92.

Although the above embodiment primarily determines the porosity characteristics of the low-k electric layer in semiconductor wafers, the principles of the present invention employ not only X-rays but also other ionizing radiation bands, for different X-ray reflectometry applications, different types of The same can be used for radiation based analysis. Therefore, the above embodiments are merely exemplary, and the present invention is not particularly limited to those illustrated and illustrated herein. Rather, the scope of the present invention includes combinations and sub-combinations of the various features of the foregoing description, as well as variations and modifications of those not disclosed in the prior art and those skilled in the art have understood the foregoing description.

According to the present invention, there is provided a thin film analysis instrument and method using X-rays.

Claims (48)

In the inspection method of a sample comprising a first layer having a known reflective property and a second layer formed on the first layer, Directing the radiation towards the surface of the sample; Sensing radiation reflected from the surface to generate a reflected signal as a function of elevation angle to the surface; Identifying a feature of the reflected signal due to the reflection of radiation from the first layer, the feature comprising a position of a shoulder in the reflected signal corresponding to a critical angle for total external reflection from the first layer; The position of the shoulder is compared to a known value of the critical angle determined by a known density of the first layer, and zero in the angular scale of the reflected signal based on the known position of the shoulder and the known critical angle. Correcting the reflected signal in response to known reflection characteristics and identified features of the first layer by detecting an angle; And Analyzing the corrected reflected signal to determine a characteristic of a second layer. The method of claim 1, wherein the radiation comprises X-rays. The method of claim 1, wherein sensing radiation comprises receiving radiation at an array of detector elements having an array axis perpendicular to the surface. 4. The method of claim 3, wherein receiving radiation is: Moving the array between at least the first and second positions along a direction parallel to the array axis; Generating a first reflected signal and a second reflected signal by the radiation received by the detector elements at the first and second positions; And Combining the first reflected signal with the second reflected signal to produce an enhanced reflected signal. The method of claim 1, wherein the critical angle for total external radiation reflected from the first layer is a first critical angle, and analyzing the corrected reflected signal corrects the second critical angle for total external radiation reflected from the second layer. And determining the value. 6. The method of claim 5, wherein the first layer and the second layer each have a first density and a second density, and analyzing the corrected reflected signal comprises evaluating the second density based on a correction value of the second critical angle. A test method for a sample, characterized in that it comprises a step. 7. The method of claim 6, wherein the second density is less than the first density. 8. The method of claim 7, wherein the first layer comprises silicon and the second layer comprises a porous dielectric. A device for inspecting a sample comprising a first layer having a known reflective property and a second layer formed on the first layer, A radiation source directing X-rays towards the surface of the sample; A detector assembly arranged to sense radiation reflected from the surface to produce a reflected signal as a function of elevation angle to the surface; And Identifying the feature in the reflected signal due to the reflection of radiation from the first layer, the feature including the position of the shoulder in the reflected signal corresponding to the critical angle for total external reflection from the first layer; The position of the shoulder is compared to a known value of the critical angle determined by a known density of the first layer, and zero in the angular scale of the reflected signal based on the known position of the shoulder and the known critical angle. Correcting the reflected signal in response to known reflection characteristics and identified features of the first layer by detecting an angle; And a signal processor coupled to receive and process the reflected signal, by analyzing the corrected reflected signal to determine a characteristic of a second layer. 10. The device of claim 9, wherein the radiation comprises X-rays. 10. The apparatus of claim 9, wherein the detector assembly comprises an array of detector elements having an array axis perpendicular to the surface. The apparatus of claim 11, wherein the detector assembly comprises at least a first position and a second such that the array generates a first reflected signal and a second reflected signal by radiation received by the detector elements at the first and second positions. A moving element for moving the array between positions along a direction parallel to the array axis, And the signal processor combines the first reflected signal and the second reflected signal to produce an enhanced reflected signal. 10. The method of claim 9, wherein the critical angle for total external radiation reflected from the first layer is a first critical angle, and the signal processor corrects the second critical angle for total external radiation reflected from the second layer by analyzing the corrected reflected signal. Device for inspection of a sample, characterized in that the value is determined. 14. The sample of claim 13, wherein the first and second layers have a first density and a second density, respectively, and the signal processor evaluates the second density based on a correction value of the second critical angle. Inspection device. 15. The apparatus of claim 14, wherein the second density is less than the first density. 16. The apparatus of claim 15, wherein the first layer comprises silicon and the second layer comprises a porous dielectric material. In the inspection apparatus of the sample, The device is: A radiation source for guiding X-rays towards the surface of the sample; And A detector assembly, The detector assembly is: A detector element array arranged along an array axis perpendicular to the surface and separated from each other at a predetermined pitch and receiving X-rays reflected from the surface and generating a signal in response to the received radiation; And A moving element coupled to move the detector element array in a direction parallel to the array axis between at least the first and second positions separated from each other by an increment that is not an integer multiple of the pitch; And A signal processor coupled to couple a signal generated by the detector assembly at at least a first position and a second position to determine an X-ray reflectance of the surface as a function of elevation angle to the surface . 18. The apparatus of claim 17, wherein the signal processor interleaves a signal generated by the detector assembly at at least a first position and a second position to determine an X-ray reflectance of the surface. 18. The apparatus of claim 17, wherein the increment is less than half the pitch. 18. The apparatus of claim 17, wherein the array comprises a linear array and the detector element has a lateral dimension greater than one pitch of the array perpendicular to the array axis. 18. The apparatus of claim 17, wherein the array comprises detector elements of a two dimensional matrix, and the detector assembly stores the detector elements in each column of the array along a direction perpendicular to the array axis. Guiding X-ray towards the surface of the sample; Constructing an array of detector elements separated from one another at a predetermined pitch to receive X-rays reflected from the surface while resolving received radiation along an array axis perpendicular to the surface; Moving the array of detector elements in a direction parallel to the array axis between at least the first and second positions separated from each other by an increment that is not an integer multiple of the pitch; Receiving at least a first signal and a second signal generated by the detector element in response to the X-rays received at each of at least the first and second positions; And Combining at least a first signal and a second signal to determine an X-ray reflectance of the surface as a function of elevation angle to the surface; Inspection method of a sample comprising a. 23. The method of claim 22, wherein combining at least the first signal and the second signal comprises interleaving these signals. 23. The method of claim 22, wherein the increase is less than half the pitch. A cluster tool for producing microelectronics, The tool is: An underlayer on a surface of a semiconductor wafer, comprising: a deposition station for depositing a thin film layer on the underlayer having known reflective properties; And Includes an inspection station, The inspection station is: A radiation source for guiding X-rays towards the surface of the wafer; A detector assembly arranged to sense radiation reflected from the surface to generate a reflected signal as a function of elevation angle to the surface; And Identifying a feature in the reflected signal due to reflection of radiation from the lower layer, the feature comprising a position of a shoulder in the reflected signal corresponding to a critical angle for total external reflection from the lower layer; The position of the shoulder of the reflected signal is compared to a known value of the critical angle determined by the known density of the lower layer, and the angle scale of the reflected signal is based on the known value of the position of the shoulder and the critical angle. Correcting the reflected signal in response to detecting a zero angle, thereby responsive to known reflection characteristics and identified features of the underlying layer; And analyzing the corrected reflected signal to determine characteristics of the thin film layer deposited by the deposition station; a signal processor coupled to receive and process the reflected signal by microelectronics. Cluster tool for producing devices. A production chamber containing the semiconductor wafer; A vapor deposition apparatus for depositing a thin film layer on the lower layer having a known reflective property as a lower layer on the surface of the semiconductor wafer in the chamber; A radiation source for guiding X-rays toward the surface of the semiconductor wafer in the chamber; A detector assembly arranged to sense radiation reflected from the surface to generate a reflected signal as a function of elevation angle to the surface; And Identifying a feature in the reflected signal due to reflection of radiation from the lower layer, the feature comprising a position of a shoulder in the reflected signal corresponding to a critical angle for total external reflection from the lower layer; The position of the shoulder is compared to a known value of the critical angle determined by the known density of the lower layer, and the zero angle in the angular scale of the reflected signal based on the known position of the shoulder and the critical angle. By detecting, correcting the reflected signal in response to known reflection characteristics and identified features of the underlying layer; And analyzing the corrected reflected signal to determine characteristics of the thin film layer deposited by the deposition apparatus; a signal processor coupled to receive and process the reflected signal by microelectronics. Device for producing the device. A cluster tool for producing microelectronics, The tool is: A deposition station for depositing a thin film layer on the surface of the semiconductor wafer; And Includes an inspection station, The inspection station is: A radiation source for guiding X-rays towards the surface of the wafer; Detector assembly; And A signal processor coupled to couple a signal generated by the detector assembly at at least a first position and a second position to determine an X-ray reflectance of the thin film layer as a function of elevation angle to the surface, The detector assembly is: A detector element array arranged along an array axis perpendicular to the surface and separated from each other at a predetermined pitch and operative to receive X-rays reflected from the surface and generate a signal in response to the received radiation; And Producing a microelectronic device comprising a moving element coupled to move the array of detector elements in a direction parallel to the array axis between at least first and second positions separated from each other by an increment not an integer multiple of the pitch Cluster tool for An apparatus for producing microelectronics, the apparatus comprising: The device is: A production chamber containing the semiconductor wafer; A deposition apparatus for depositing a thin film layer on a surface of a semiconductor wafer in the chamber; A radiation source for guiding X-rays toward the surface of the semiconductor wafer in the chamber; Detector assembly; And A signal processor coupled to couple a signal generated by the detector assembly at at least a first position and a second position to determine an X-ray reflectance of the thin film layer as a function of elevation angle to the surface, The detector assembly is: A detector element array arranged along an array axis perpendicular to the surface and separated from each other at a predetermined pitch and operative to receive X-rays reflected from the surface and generate a signal in response to the received radiation; And Producing a microelectronic device comprising a moving element coupled to move the array of detector elements in a direction parallel to the array axis between at least first and second positions separated from each other by an increment not an integer multiple of the pitch Device for Directing radiation from a radiation source at a first predetermined location towards the radiation sensor at a second predetermined location; While the shutter is positioned to block radiation at a predetermined blocking angle, detecting radiation incident directly on the radiation sensor from the radiation source to generate a first direct signal as a function of elevation; While the shutter is positioned so as not to block radiation at a predetermined blocking angle, detecting radiation directly incident on the radiation sensor from the radiation source to generate a second direct signal as a function of elevation; Introducing a sample between a radiation source at a first predetermined location and a radiation sensor at a second predetermined location such that radiation is incident on the surface of the sample; While the shutter is positioned to block radiation at a predetermined blocking angle, detecting radiation reflected from the surface of the sample onto the radiation sensor to generate a first reflected signal as a function of elevation; While the shutter is positioned so as not to block radiation at a predetermined blocking angle, detecting radiation reflected from the surface of the sample onto the radiation sensor to generate a second reflected signal as a function of elevation; And Comparing a second ratio between the first reflected signal and the second reflected signal to a first ratio between the first direct signal and the second direct signal to find an elevation of the tangent to the surface; Inspection method of the sample. 30. The method of claim 29, wherein the radiation comprises X-rays. 30. The method of claim 29, wherein the radiation sensor comprises an array of detector elements having an array axis perpendicular to the surface of the sample. 32. The method of claim 31, wherein sensing radiation to measure direct and reflected signals comprises: Moving the array between at least a first position and a second position along a direction parallel to the array axis;  Generating first and second signals due to radiation received by the detector element at least in the first and second positions; Combining the first and second signals to generate an enhanced signal. 30. The method of claim 29, comprising analyzing the first and second reflected signals to measure the properties of the thin film layer on the sample surface. 30. The method of claim 29, wherein comparing the first ratio and the second ratio comprises: finding a first elevation angle having the first value having a given value and a second elevation angle having the second value having the given value; Measuring an elevation of a tangent to a surface that is an average of elevation angles. 35. The method of claim 34, comprising obtaining a difference between the first and second elevation angles to measure the minimum elevation angle at which the shutter blocks radiation below the minimum elevation angle. Sample inspection device is: A radiation source at a first predetermined location for generating radiation; A positionable shutter to block radiation at a predetermined blocking angle; A moving stage configured to position the sample such that radiation generated by the radiation source is incident on the surface of the sample; The radiation sensor in a second predetermined position that senses radiation to generate a signal responsive to radiation incident on the radiation sensor as a function of elevation angle; A signal processor coupled to compare a first ratio between the first direct signal and the second direct signal and a second ratio between the first reflected signal and the second reflected signal to find an elevation of the tangent to the surface; , The signal is: A first direct signal responsive to radiation incident directly on the radiation sensor from the radiation source while the shutter is positioned to block radiation at a predetermined blocking angle; A second direct signal responsive to radiation directly incident on the radiation sensor from the radiation source while the shutter is positioned to not block radiation at a predetermined blocking angle; A first reflected signal responsive to radiation reflected from the surface of the sample to the radiation sensor while the shutter is positioned to block radiation at a predetermined blocking angle; And a second reflected signal responsive to radiation reflected from the surface of the sample to the radiation sensor while the shutter is positioned to not block radiation at a predetermined blocking angle. 37. The sample inspection apparatus of claim 36, wherein the radiation comprises X-rays. 37. The sample inspection apparatus of claim 36, wherein the radiation sensor comprises an array of detector elements having an array axis perpendicular to the surface of the sample. 39. The detector of claim 38, wherein the radiation sensor includes a moving element that moves the array between at least the first position and the second array position along a direction parallel to the array axis. Generate at least a first and a second signal due to the radiation received by the element, And the signal processor combines at least the first and second signals to generate an enhanced signal. 37. The apparatus of claim 36, wherein the signal processor analyzes the first and second reflected signals to measure the properties of the thin film layer on the sample surface. 37. The method of claim 36, wherein the signal processor finds a first elevation angle having a first value having a given value and a second elevation angle having a second value having a given value, and obtaining an average of the first and second elevation angles to the surface. A sample inspection device, characterized by measuring the elevation angle of the tangent. 42. The apparatus of claim 41, wherein the signal processor obtains a difference between the first and second elevation angles thereafter to measure the minimum elevation angle at which the shutter blocks radiation. delete delete delete delete delete delete

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