Evaluation device

An evaluation device includes an X-ray diffraction measuring device configured to acquire a first X-ray locking curve having a first main peak and a first sub-peak partially overlapping the first main peak by measuring an X-ray locking curve of a first portion of a sample having a crystalline material. The evaluation device includes an analysis device configured to separate the first sub-peak from the first main peak, perform first evaluation of a crystal defects or distortion of the sample based on a peak position, peak intensity, or a half width of the separated first sub-peak, and output the first evaluation.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2022-037614, filed Mar. 10, 2022, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to an evaluation device.

BACKGROUND

The sample is evaluated by X-ray diffraction measurement.

DETAILED DESCRIPTION

Embodiments provide an evaluation device capable of performing precise evaluation.

In general, according to one embodiment, an evaluation device includes an X-ray diffraction measuring device configured to acquire a first X-ray rocking curve having a first main peak and a first sub-peak partially overlapping the first main peak by measuring an X-ray rocking curve of a first portion of a sample having a crystalline material. The evaluation device includes an analysis device configured to separate the first sub-peak from the first main peak, perform first evaluation of crystal defects or distortion of the sample based on a peak position, a peak intensity, and a half width of the separated first sub-peak, and output the first evaluation.

Hereinafter, embodiments will be described with reference to the drawings. In the drawings, the same or similar portions are designated by the same or similar reference numerals.

First Embodiment

FIG.1is a block diagram illustrating a configuration example of an evaluation device1of the present embodiment. The evaluation device1of the present embodiment is an evaluation device based on a rocking curve method for obtaining an incident angle distribution of diffraction intensity from part of a sample. The evaluation device1provides an X-ray diffraction measuring device10and an analysis device20. The evaluation device1of the present embodiment is used for evaluation of, for example, a sample40. Here, the sample40is a silicon wafer on which a pattern of a memory cell array or the like of a NAND memory having a three-dimensional structure is formed. Further, the evaluation device1may further provide a display device30for displaying an evaluation result.

The X-ray diffraction measuring device10includes an X-ray irradiation unit11, a sample stage12, a stage driving unit13, an X-ray detection camera14, and a control unit15. The X-ray diffraction measuring device10irradiates an inspection region of the sample40with monochromatic X-rays with good parallelism and measures intensity (diffracted light intensity) of diffracted X-rays generated from the sample40by using an X-ray camera. By measuring an incident angle of X-rays while scanning the incident angle, change characteristics (X-ray rocking curves) of the diffracted light intensity on the incident angle can be acquired for each pixel of the X-ray camera.

The X-ray irradiation unit11provides an X-ray source (not illustrated), a multilayer film focusing mirror, a monochromator, and a slit. The X-ray source includes, for example, a rotation cathode type target (for example, Cu, Mo, or the like) and a filament for generating an electron beam. When a target is irradiated with an electron beam generated from the filament and accelerated by a high voltage, X-rays are emitted from a target metal. The multilayer film focusing mirror monochromatizes and parallelizes the X-rays emitted from the X-ray source to increase intensity. The monochromator is, for example, a double crystal monochromator and further increases degree of parallelization of X-rays incident from the multilayer film focusing mirror to the extent that lattice spacing of an element to be measured can be acquired. The slit limits a range in which the X-rays incident from the monochromator irradiate the sample40. Specifically, the range of X-rays that irradiate the sample40is limited to a width direction Hi and a depth direction Li. That is, assuming that an incident angle of X-rays on the sample40is θs, the range (irradiation region) in which the X-rays irradiate the sample40is a rectangular region where the x direction is Hi/sin θs and the y direction is Li. In the following, the X-ray irradiation unit11has a configuration in which the incident angle θs of X-rays on the sample40can be changed in a predetermined range.

FIG.2is a schematic diagram illustrating a positional relationship between the X-ray irradiation unit11, the sample40, and the X-ray detection camera14. As illustrated inFIG.2, for example, by setting a central position of an X-ray irradiation region in the sample40as a center and maintaining constant a distance Di from a slit (not illustrated) to the central position of the irradiation region in the sample40, the X-ray irradiation unit11is rotatable in an xz plane.

The X-ray detection camera14receives the diffracted X-rays generated from the sample40and generates a signal according to intensity of the received diffracted X-rays. The X-ray detection camera14includes a plurality of semiconductor detection elements (solid-state imaging elements or the like) arranged in, for example, a two-dimensional array. For example, charge coupled devices (CCDs) or CMOS image sensors are used as the semiconductor detection elements. The diffracted X-rays generated from irradiation X-rays in the irradiation region of the sample40are photoelectrically converted by the semiconductor detection elements disposed in a projection region of the X-ray detection camera14and output as an imaging signal.

As illustrated inFIG.2, for example, by setting the central position of the X-ray irradiation region in the sample40as a center and maintaining constant a distance Do from the central position of irradiation region in the sample40to the projection region of the X-ray detection camera14, the X-ray detection camera14is rotatable in the xz plane. Specifically, a position of the X-ray detection camera14is adjusted according to a rotation state of the X-ray irradiation unit11so as to make constant an angle θc between a direction of the X-rays irradiated on the sample40and a line connected the central position of the X-ray irradiation region in the sample40to the central position of the projection region of the X-ray detection camera14. The adjustment of the position of the X-ray detection camera14is called ω (omega) scan. For example, when the X-ray irradiation unit11and the X-ray detection camera14are fixed and the sample40is rotated in the xz plane, the angle θs (an angle ω (omega)) of the X-rays incident on the sample40can be changed while a difference (2θ) between an angle of an X-ray reflected by the sample40and an angle of an X-ray incident on the sample40are fixed. Such measurement is called measurement by the co (omega) scan. Further, even when the sample40is not rotated in the xz plane, the measurement by the ω (omega) scan can be performed by appropriately rotating the X-ray irradiation unit11and the X-ray detection camera14.

The sample stage12(FIG.1) can be moved in two directions (the x direction and the y direction) parallel to a surface of the sample stage12by the stage driving unit13such as a motor. By moving the sample stage12in the x direction and/or the y direction, the irradiation region of the sample40can be scanned. Further, as illustrated inFIG.2, the sample stage12is rotatable at a predetermined angle φ in the xy plane.

The control unit15(FIG.1) controls the entire operation of the X-ray diffraction measuring device10. Specifically, for example, the control unit15controls rotations of X-rays of the X-ray irradiation unit11according to a change of the incident angle θs or controls rotation of the X-ray detection camera14according to the rotation of the X-rays of the X-ray irradiation unit11. Further, the control unit15controls parameters and the like of each part constituting the X-ray irradiation unit11, and further instructs the stage driving unit13to move (move in parallel in the xy plane) or rotate (rotationally move in the xy plane) a stage position so as to adjust a position where the X-ray is incident on the sample40.

The control unit15(FIG.1) transmits location information of the sample stage12, that is, an incident position (coordinates) of the X-ray in the sample40to the analysis device20. Then, the control unit15receives initial setting information for acquiring an X-ray rocking curve and change information of each setting content from the analysis device20.

The analysis device20(FIG.1) is, for example, a computer. The analysis device20provides a central processing unit (CPU)21, a RAM22, and a memory unit23. The analysis device20performs analysis processing (analysis and evaluation) of data (an electrical signal having a magnitude corresponding to detection intensity of the diffracted light output from each pixel of the X-ray detection camera14) input from the X-ray diffraction measuring device10, an incident position (coordinates, the incident angle θs) of the X-ray of the sample40output from a control unit15, and an X-ray rocking curve. Further, the analysis device20outputs a result of the analysis processing (analysis and evaluation).

The CPU21(FIG.1) operates according to a program stored in the memory unit23and controls each portion of the analysis device20. The RAM22stores data input from the X-ray diffraction measuring device10and stores a result obtained by executing a program described below.

The memory unit23stores software231for operating the X-ray diffraction measuring device10to acquire and analyze a desired X-ray rocking curve. The software231is read into the RAM22to be loaded and executed by the CPU21, and thus, an X-ray rocking curve is evaluated. As a result of the evaluation, for example, a position of the sample40on which evaluation was performed can be two-dimensionally mapped to be displayed. An output destination of the result of the evaluation may be, for example, the display device30. The analysis device20may be configured to cause an operation realized by the software231to be performed by one or more processors (not illustrated) configured as hardware. A processor that performs the operation realized by the software231may be, for example, a processor configured as an electronic circuit or a processor configured with an integrated circuit such as a field programmable gate array (FPGA).

FIGS.3A and3Bare diagrams illustrating X-ray rocking curves measured in each portion of a first sample41in the first embodiment.FIG.3Aillustrates a schematic upper view of the first sample41. Further, a first portion41a, a second portion41b, and a third portion41cprovided on the first sample41are illustrated.FIG.3Billustrates an X-ray rocking curve measured in the first portion41a, an X-ray rocking curve measured in the second portion41b, and an X-ray rocking curve measured in the third portion41c.

When looking at the rocking curve measured in the first portion41a, a peak having intensity of about 0.5 is observed near an incident angle of 0.025 deg. Further, a half width of the peak is about 0.003 deg.

When looking at a rocking curve measured in the second portion41b, a peak having intensity of about 1.2 is observed near a greater incident angle of 0.036 deg. Further, a half width of the peak is greater, that is about 0.01 deg.

When looking at the rocking curve measured in the third portion41c, a peak is observed near 0.03 deg which is greater than the incident angle observed in the first portion41aand less than the incident angle observed in the second portion41b. Intensity of the peak is about 1.1 which is greater than the intensity of the peak observed in the first portion41aand less than the intensity of the peak observed in the second portion41b. A half width of the peak is about 0.02 deg which is greater than the peak measured in the first portion41aand the peak measured in the second portion41b.

As described above, peaks of different incident angles, different intensities, and different half widths are observed in different portions (the first portion41a, the second portion41b, and the third portion41c) of the first sample41.

Next, action and effect of the present embodiment will be described.

An evaluation device for a sample having a crystalline material and using X-rays includes an evaluation device based on a topograph imaging method of imaging and evaluating a diffracted image from the entire sample, and an evaluation device based on a rocking curve method of obtaining an incident angle distribution of diffraction intensity from a portion of a sample.

FIGS.4A to4Dare schematic diagrams illustrating results of evaluating the sample40by using an evaluation device based on the topograph imaging method, according to a comparative embodiment of the present embodiment.FIG.4Aillustrates a rocking curve corresponding to (422) plane reflection of silicon.FIG.4Billustrates a diagram (denoted as “Low angle”) in which topograph imaging was performed for an incident angle less than the incident angle corresponding to (422) plane reflection.FIG.4Cillustrates a diagram (denoted as “just Bragg”) in which topograph imaging was performed at an incident angle corresponding to (422) plane reflection.FIG.4Dillustrates a diagram (denoted as “High angle”) in which topograph imaging was performed for an incident angle greater than the incident angle corresponding to (422) plane reflection. AmongFIGS.4B,4C, and4D,FIG.4Dillustrates that a pattern formed on the sample40is most clearly observed. This suggests that silicon in an imaged portion of the sample40is distorted such that an incident angle of a rocking curve is increased. More specifically, this suggests interplanar spacing of crystal planes of silicon in the imaged portion of the sample40is reduced.

Furthermore, an in-plane distribution of crystal defects can be evaluated by analyzing a change in the pattern observed in the figure in the X and Y directions. As such, an evaluation device based on a topograph imaging method can evaluate a sample with crystallinity.

Meanwhile, in a case of the evaluation device based on the topograph imaging method, a method of observing crystal defects changes according to an incident angle of X-rays. It is ideal for quantitatively evaluating crystal defects to make measurement changing the incident angle of X-rays. Meanwhile, as illustrated in, for example,FIGS.4B,4C, and4D, when an incident angle is changed, appearance of a pattern formed on the sample40is changed. Therefore, it is difficult to quantitatively compare and examine evaluation results ofFIGS.4B,4C, and4D. As a result, it is difficult to quantitatively evaluate crystal defects from an X-ray topograph image obtained through a topograph imaging method.

FIGS.5A and5Bare schematic diagrams illustrating evaluation of the sample40including a substrate40aand a thin film40cformed on the substrate40a. Here, it is assumed that the substrate40ahas crystallinity. The sample40is an example of the sample40used in the present embodiment.

FIG.5Ais a schematic diagram in a case where the sample40does not include the thin film40c. Atoms40bare arranged on the substrate40awith a predetermined cycle. X-rays incident by the X-ray irradiation unit11are reflected and detected by the X-ray detection camera14.

FIG.5Bis a diagram in a case where the sample40includes the thin film40c. In a case where the thin film40cis provided, atomic arrangement in the substrate40amay be distorted. For example, an interatomic distance L2of the atoms40bin the substrate40aofFIG.5Bis longer than an interatomic distance L1illustrated inFIG.5Aas the sample40includes the thin film40c. In this case, an interatomic distance in a crystal plane naturally changes. Further, an interval between the crystal planes also changes. Thereby, Bragg condition for reflecting X-rays also changes.

FIGS.6A to6Care diagrams illustrating action and effect of the present embodiment.FIG.6Aillustrates an X-ray rocking curve of the sample40having no distortion.FIG.6Billustrates an example of an X-ray rocking curve of the sample40having distortion. For example, when X-rays are reflected on the larger incident angle side, a position of a peak of the X-ray rocking curve is observed on the larger incident angle side.FIG.6Cillustrates another example of the X-ray rocking curve of the sample40with distortion. When X-rays are simultaneously irradiated to portions having different incident angles, a plurality of peaks which are small and have different incident angles overlap each other as illustrated by dashed lines inFIG.6C, and one peak is observed as illustrated by a solid line inFIG.6C.

Then, in a case of an evaluation device based on a rocking curve method of obtaining an incident angle distribution of diffraction intensity from part of a sample, such as the evaluation device of the present embodiment, rocking curves when an incident angle is changed can be measured in the first portion41a, the second portion41b, and the third portion41cof the sample. Furthermore, crystal defects or distortion of the first portion41acan be evaluated based on a peak position (an incident angle), a peak intensity, and a half width of the peak of the rocking curve measured in the first portion41a. The same applies to the second portion41band the third portion41c.

According to the evaluation device of the present embodiment, the evaluation device capable of performing precise evaluation can be provided.

Second Embodiment

Description of content overlapping with the first embodiment is omitted.

FIG.7is a schematic cross-sectional view of the sample40evaluated by the evaluation device of the present embodiment. An insulating film40ehaving an element separation function is formed around a semiconductor portion40dhaving a trapezoidal cross section. The semiconductor portion40dis configured to be adjacent to a pattern such as a memory cell array of a NAND memory having a three-dimensional structure. The semiconductor portion40dhas silicon as a crystalline material. Then, a gate electrode40f1is provided in the upper left of the semiconductor portion40dthrough the insulating film40e. Further, a gate electrode40f2is provided in the upper right of the semiconductor portion40dthrough the insulating film40e. Both portions40gand40hare insulating films, but materials thereof are different from each other. A distance between an upper surface40d1of the semiconductor portion40din the X direction and the gate electrode40f1, and a distance between the upper surface40d1of the semiconductor portion40din the X direction and the gate electrode40f2are referred to as L. Here, crystal defects or distortion may occur in the semiconductor portion40d, depending on the distance L. The present embodiment describes evaluation of the crystal defects or distortion.

FIGS.8A and8Bare schematic diagrams illustrating evaluation results of the second sample, the third sample, and the fourth sample in the comparative embodiment of the present embodiment.

FIG.8Bis a schematic diagram illustrating differences between the second sample, the third sample, and the fourth sample.FIG.8Bis a schematic diagram illustrating shapes of the upper surface40d1of the semiconductor portion40dwhen viewed from the Z direction. In the second sample, the upper surface40d1has a line shape extending in the Y direction. In the third sample, the upper surface40d1has a cross shape extending in the X direction and the Y direction. In the fourth sample, the upper surface40d1that does not extend in the Y direction beyond a portion thereof extending in the X direction is formed. The upper surface40d1of the fourth sample has a T shape.

FIG.8Ais a schematic diagram illustrating results obtained by evaluating the second sample, the third sample, and the fourth sample in different distances L (−0.3, 0, 0.3, 0.65, 0.80, 0.95, 1.1, 1.25, 1.4, and 2.0 where, L is an arbitrary unit (abbreviated as a.u.) and the same is applied hereinafter) by using a topograph imaging method. A plurality of basic patterns illustrated inFIGS.7and8Bare arranged in a square region. A contrast image in the square region is an image taken by an X-ray topograph, and a difference in shading is checked by a difference in crystal defects and distortion. A defect rate of crystal defects can be defined by standardizing a degree of the shading. That is, when contrast is dark, the defect rate is high, and conversely, when contrast is light, the defect rate is low. In the second sample and the third sample, L=1.25 or more, and in the fourth sample, L=1.4 or more, contrast is light, and a defect rate is very low. Meanwhile, in the comparative embodiment, although presence or absence of crystal defects could be determined, the crystal defects and distortion could not be quantitatively evaluated.

FIG.9is a diagram illustrating X-ray rocking curves measured in different distances L for the second sample of the present embodiment. The X-ray rocking curves illustrated inFIG.9correspond to (422) plane reflection of silicon. Main peaks of the X-ray rocking curves are observed near an incident angle of 0.014 deg. Further, sub-peaks of the X-ray rocking curves are observed near or less than an incident angle of 0.014 deg.

FIGS.10A and10Bare examples of function fitting performed on the main peak of the X-ray rocking curve.FIG.10Aillustrates a measured X-ray rocking curve. Further,FIG.10Billustrates that a main peak of the X-ray rocking curve illustrated inFIG.10Ais fitted as the sum of a rocking curve1and a rocking curve2. The rocking curve1and the rocking curve2can be generated by using, for example, a Gaussian function or a Lorentzian function. A function used for fitting is not limited to the Gaussian function or the Lorentzian function.

FIG.11is a diagram illustrating sub-peaks, which are separated from main peaks, of X-ray rocking curves measured in the second sample of the present embodiment. The sub-peaks have information on crystal defects or distortion.

For example, crystal defects or distortion related to an interval between crystal planes can be evaluated from incident angles of the sub-peaks. Assuming that the interval between crystal planes is d, a margin of an incident angle is θ, λ is a wavelength of an X ray, and n is a natural number, a relationship of 2dsinθ=nλ (Bragg's law) is established. Accordingly, crystal defects or distortion related to the interval between crystal planes may be evaluated from an incident angle.

Further, for example, a crystallite size of a portion of crystal defects or distortion can be evaluated from a half width of a sub-peak. Generally, as the crystallite size is reduced, the half width tends to increase. Accordingly, the crystallite size of the portion of the crystal defects or distortion may be evaluated from the half width of the sub-peak.

Evaluation results derived from the sub-peaks are not limited thereto.

FIG.12is a diagram illustrating X-ray rocking curves measured in the third sample of the present embodiment.FIG.13is a diagram illustrating sub-peaks, which are separated from main peaks, of X-ray rocking curves measured in the third sample of the present embodiment.FIG.14is a diagram illustrating X-ray rocking curves measured in the fourth sample of the present embodiment.FIG.15is a diagram illustrating sub-peaks, which are separated from main peaks, of X-ray rocking curves measured in the fourth sample of the second embodiment. The third sample and the fourth sample can be evaluated in the same manner as the second sample.

According to the evaluation device of the present embodiment, the evaluation device capable of performing precise evaluation can be provided.