JP2007220317A - Electron beam inspection method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electron beam inspection method and device quick in identification without contamination and static charge, and with high accuracy in identification of a substance with structural defect. <P>SOLUTION: With the use of scattered information of backscattering electrons, an average value S of emission efficiency including a fluctuation ▵S is found (a step S304), a plurality of candidate matters causing structural defects of a sample 5 are selected (a step S305) with the use of the average value S and the fluctuation ▵S, electron energy of electron beams 2 is made to vary (a step S307), and selection of the candidate matters is repeated to identify the matter causing the structural defect from among the plurality of candidate matter information obtained (a step S308), so that high accuracy is attained in identifying a matter causing structural defect, and further, a low-cost, high-speed, and high-accuracy matter identification is to be realized without the use of an EDS or the like. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electron beam inspection method and apparatus for detecting a structural defect generated in a semiconductor wafer in a semiconductor manufacturing process for manufacturing a planar type integrated circuit using the semiconductor wafer and searching for a cause of the structural defect.

  In recent years, a semiconductor device is manufactured by repeating a process of transferring a pattern formed on a wafer with a photomask by lithography and etching. In such a manufacturing process, in order to improve the yield and realize stable operation of the manufacturing process, it is necessary to quickly analyze defects found by in-line inspection and use them for countermeasures.

  In order to quickly link inspection results with countermeasures against defects, a defect review: classification technique that reviews a large number of inspection results at high speed and classifies them according to the cause of occurrence is the key. For this reason, optical beam inspection apparatuses such as optical and SEM (scanning electron microscope) have been commercialized. In addition, with the miniaturization of a processing pattern, SEM having higher resolution than an optical type is regarded as important. These electron beam inspection apparatuses can detect irregularities such as minute foreign matter, minute shape defects, and scratches. Furthermore, by performing substance identification of these defects, it is possible to more accurately identify the cause of the defect, for example, in which manufacturing process the defect has occurred, which is also an important matter.

  Here, there are three known examples as a method of substance identification. The first method is a method using EDS (Energy Dispersive x-ray Spectroscopy). This is a characteristic X-ray generated by irradiating a defect portion with a primary electron beam having a high energy of 15 keV and a high beam current of 1 nA, which is larger than the energy of about 1 keV and the beam current of about 10 pA, which are usually used for observation The substance is identified by obtaining This method has high accuracy of substance identification, but it requires switching of beam energy and beam current when using EDS, and it takes time to switch. Further, since the energy is high, the beam spreads widely in the solid, and because the beam is a large current beam, the beam diameter is widened, resulting in poor spatial resolution. In addition, the device price is also high.

  The second method is a method of improving the material contrast of the SEM image by performing energy separation of secondary electrons (see, for example, Patent Document 1). In this method, since contamination (film having a very thin carbon as a main component) adheres to the sample by irradiation with the primary electron beam, the emission efficiency of secondary electrons generated from the extremely thin surface changes greatly. Secondary electrons have low energy and are strongly influenced by the charging of the sample. In a sample that is easily charged, the trajectory changes and the secondary electron detection efficiency at the detector changes. Therefore, the substance contrast cannot be obtained with high accuracy.

  The third method uses backscattered electrons (generally electrons having an initial kinetic energy of 50 ev or more). Since backscattered electrons are generated from a position deep to some extent in the sample, they are not easily affected by contamination. In addition, since this method is high in energy, it is not easily affected by charging, and the emission efficiency of backscattered electrons increases in proportion to the atomic number (for example, see Non-Patent Document 1). Has been used to get. However, with this method, the signal amount of backscattered electrons is small, and the signal amount varies (shot noise), making it difficult to detect substances with similar atomic numbers.

  FIG. 11 is an explanatory diagram for explaining this difficulty. FIG. 11A is a diagram illustrating an example of a backscattered electron image acquired by SEM. In this backscattered electron image 101, copper patterns 105 arranged on a silicon substrate 104 are shown, and structural defects 102 made of aluminum powder or the like adhere to gap portions of these lattices. FIG. 11B is a diagram showing a profile of the backscattered electron image 101 in the portion indicated by the solid line AB where the structural defect 102 exists. The horizontal axis represents the pixel position on the solid line AB, and the vertical axis represents the emission efficiency calculated from the backscattered electron signal. The release efficiency will be described in detail in the section of the best mode for carrying out the invention.

  Here, the emission efficiency S is large in the calculation region 51 in the central portion where the structural defect 102 exists. On the other hand, there is a variation ΔS in the emission efficiency S of the calculation region 51, and the value cannot be specified.

FIG. 11C is a diagram showing the relationship between the emission efficiency of backscattered electrons and the atomic number. In this figure, the horizontal axis represents the atomic number, the vertical axis represents the emission efficiency, and the atomic number and the emission efficiency are in a proportional relationship. Here, the atomic number corresponding to the emission efficiency S is determined using this proportional relationship. On the other hand, when there is a variation ΔS in the emission efficiency, the atomic number varies 32 and it becomes difficult to specify the atomic number. In the example of FIG. 11C, the case where the atomic number is between 11 and 16 with respect to the emission efficiency variation ΔS is illustrated.
JP 2000-173526 A L. Reimer et al., “Scanning Electron Microscopy”, published by Springer-Verlag, 1998, p. 145

  However, according to the above-described background art, although the above-described first method has a high accuracy of substance identification, it takes time for identification, the spatial resolution is low, and the device price is high. In the second method described above, although the identification time is early, it is affected by contamination and charging. Further, in the third method described above, the identification time is fast and there is no contamination and no charge, but the accuracy of identifying the substance of the structural defect 102 is low.

  For these reasons, it is important how to realize an electron beam inspection method and apparatus with a high accuracy for identifying a substance having a structural defect while identifying time is fast, there is no contamination and charging.

  The present invention has been made in order to solve the above-described problems caused by the background art, and has a fast identification time, no contamination and no charging, and a highly accurate electron beam inspection method for identifying a structural defect substance and An object is to provide an apparatus.

  In order to solve the above-described problems and achieve the object, an electron beam inspection method according to claim 1 is directed to irradiating a surface of a sample with a primary electron beam generated by an electron gun. Detecting the scattering information of backscattered electrons generated from the surface, and obtaining candidate substance information of candidate substances that are candidates for identifying substances existing on the surface based on the scattering information, The irradiation conditions at the time of irradiation are changed, the irradiation, the detection, and the acquisition are repeated, and the plurality of candidate substance information acquired by the repetition are compared to identify the substance.

According to the first aspect of the present invention, the substance of the structural defect generated on the surface of the sample is identified based on a plurality of pieces of scattered information of backscattered electrons with different irradiation conditions.
An electron beam inspection method according to a second aspect of the present invention is the electron beam inspection method according to the first aspect, wherein the identification includes a candidate substance that is commonly included in a plurality of candidate substance information. It is characterized by.

  The electron beam inspection method according to a third aspect of the present invention is the electron beam inspection method according to the first or second aspect, wherein the scattering information includes emission efficiency of the backscattered electrons and variations in the emission efficiency. It is characterized by including a size.

  An electron beam inspection method according to claim 4 is the electron beam inspection method according to any one of claims 1 to 3, wherein the irradiation condition is an acceleration voltage of the primary electron beam. It is characterized by that.

  An electron beam inspection method according to a fifth aspect of the invention is the electron beam inspection method according to any one of the first to fourth aspects, wherein the acquisition is a scattering accompanying the change for each candidate substance. It is characterized by being performed with reference to scattering change information indicating a change in information.

  The electron beam inspection method according to claim 6 is the electron beam inspection method according to claim 5, wherein the irradiation with the change and the detection are performed on a candidate material sample made of the candidate material. And the scattering change information is acquired in advance before performing irradiation and detection of the sample.

  An electron beam inspection method according to a seventh aspect of the invention is the electron beam inspection method according to any one of the first to sixth aspects, wherein the substance and the substance are based on positional information of the substance. The image information on the surface of the sample including the vicinity region is collected.

  An electron beam inspection method according to an eighth aspect of the present invention is the electron beam inspection method according to the seventh aspect, wherein the plurality of scattering information is subjected to arithmetic processing to obtain image information in which the contrast of the substance is emphasized. It is characterized by forming.

  An electron beam inspection method according to the invention described in claim 9 is the electron beam inspection method according to any one of claims 1 to 8, wherein the candidate substance is selected before performing the identification, The identification is performed on the candidate substance that has been selected.

  An electron beam inspection method according to a tenth aspect of the invention is the electron beam inspection method according to any one of the first to ninth aspects, wherein the identification information of the substance, the positional information of the substance, and the substance The substance is classified based on the shape information.

  According to an eleventh aspect of the present invention, there is provided an electron beam inspection apparatus according to an eleventh aspect, wherein an irradiation means for irradiating a surface of a sample with a primary electron beam generated by an electron gun, and a rear portion generated from the surface during the irradiation. A detector that detects scattering information of scattered electrons, a substance information acquisition unit that acquires candidate substance information of a candidate substance that is a candidate for identifying a substance existing on the surface, based on the scattering information; and the irradiation A control unit that repeats the irradiation, the detection, and the acquisition, and a substance identification unit that compares the plurality of candidate substance information acquired by the repetition and identifies the substance, Is provided.

In the eleventh aspect of the invention, the substance of the structural defect generated on the surface of the sample is identified based on the plurality of pieces of scattered information of the backscattered electrons with the irradiation condition changed.
An electron beam inspection apparatus according to a twelfth aspect of the present invention is the electron beam inspection apparatus according to the eleventh aspect, wherein the detector includes a plurality of detectors having different angles from the irradiation direction in which the irradiation is performed. It is characterized by providing.

In the invention described in claim 12, the scattering information of the backscattered electrons scattered in different directions is acquired.
An electron beam inspection apparatus according to a thirteenth aspect of the present invention is the electron beam inspection apparatus according to the twelfth aspect, wherein the detector is arranged such that at least one of the detectors is disposed in the vicinity of the surface. It is characterized by that.

According to the thirteenth aspect of the present invention, even when a sample having a small thickness in the irradiation direction irradiated with the primary electron beam is used, the substance existing on the sample surface is identified.
An electron beam inspection apparatus according to a fourteenth aspect of the present invention is the electron beam inspection apparatus according to any one of the eleventh to thirteenth aspects, wherein the detector includes a sample stage on which the sample is placed, A lens barrel part including the irradiation means is provided.

  An electron beam inspection apparatus according to a fifteenth aspect of the present invention is the electron beam inspection apparatus according to the fourteenth aspect, wherein the sample stage juxtaposes a standard sample made of the candidate substance together with the sample. And

According to the fifteenth aspect of the present invention, the scattering change information is acquired using an electron beam inspection apparatus.
An electron beam inspection apparatus according to a sixteenth aspect of the present invention is the electron beam inspection apparatus according to the fourteenth or fifteenth aspect, wherein the detector includes a mounting surface on which the sample of the sample stage is mounted. The detector that performs the detection when the crossing angle with the orthogonal plane orthogonal to the irradiation direction of the primary electron beam irradiated from the lens barrel portion has a finite value is placed near the irradiation position of the sample. It has the arrangement means to arrange, It is characterized by the above-mentioned.

In the sixteenth aspect of the present invention, the detection efficiency of backscattered electrons by the detector is improved.
The electron beam inspection apparatus according to claim 17 is the electron beam inspection apparatus according to any one of claims 11 to 16, wherein the detector collides the backscattered electrons. And a secondary electron detector for detecting secondary electrons generated by the reflector.

According to the seventeenth aspect of the present invention, the detection efficiency of backscattered electrons by the detector is improved.
The electron beam inspection apparatus according to claim 18 is the electron beam inspection apparatus according to claim 17, wherein the reflector has a ring-shaped structure surrounding the primary electron beam. And

In the invention described in claim 18, the detection efficiency is greatly improved.
An electron beam inspection apparatus according to claim 19 is the electron beam inspection apparatus according to any one of claims 11 to 18, wherein the substance identification information, the substance position information, and the substance A classifying means for classifying the substance based on the shape information is provided.

According to the nineteenth aspect of the present invention, when a substance has a structural defect, it is easy to identify a factor that has occurred.
An electron beam inspection apparatus according to a twentieth aspect of the invention is the electron beam inspection apparatus according to any one of the eleventh to nineteenth aspects, wherein image information obtained by performing arithmetic processing on the scattered information is formed. An image forming unit is provided.

According to the twentieth aspect of the present invention, it is easy to see an image of a substance included in the image information, that is, a structural defect.
An electron beam inspection apparatus according to a twenty-first aspect of the invention is the electron beam inspection apparatus according to any one of the eleventh to twentieth aspects, wherein display means for displaying a substance name of the identified substance is provided. It is characterized by providing.

In the invention described in claim 20, the operator is notified of the substance name of the identified substance.
An electron beam inspection apparatus according to a twenty-second aspect of the present invention is the electron beam inspection apparatus according to the twentieth and twenty-first aspects, wherein the display means displays the image information, and the image is displayed on the displayed image. The substance name is overwritten.

  In the twenty-second aspect of the present invention, the operator is notified of the shape of the substance together with the substance name of the identified substance.

  According to the present invention, since a substance having a structural defect is identified based on a plurality of scattered information of backscattered electrons whose irradiation conditions are changed, the identification time is fast, there is no contamination and charging, and the structure It is possible to identify the substances that make up the defects with high accuracy, and to classify the structural defects reliably and at high speed, making it easy to identify the cause of the structural defects, and to reduce the structural defects in the sample quickly and reliably. Furthermore, when the sample is a semiconductor wafer, the yield can be improved immediately.

  The best mode for carrying out an electron beam inspection method and apparatus according to the present invention will be described below with reference to the accompanying drawings. Note that the present invention is not limited thereby.

  First, the overall configuration of the electron beam inspection apparatus 99 according to the present embodiment will be described. FIG. 1 is a configuration diagram showing the overall configuration of the electron beam inspection apparatus 99. The electron beam inspection apparatus 99 includes an electron gun 1, an objective lens 4, a deflection coil 17, a sample 5, a sample table 6, a detector 7, an information processing unit 8, a sample table control unit 9, a power supply control unit 10, a control unit 11, A display unit 12 and an input unit 13 are included. Here, the electron gun 1, the objective lens 4, the deflection coil 17, the sample 5, the sample stage 6, the detector 7, and the sample stage control unit 9 are disposed in a vacuum container (not shown). This vacuum vessel is brought into a high vacuum state using a rotary pump, a molecular pump, an ion pump, or the like. Further, the electron gun 1, the objective lens 4, the deflection coil 17, and the power supply control unit 10 constitute an irradiation unit.

  The electron gun 1 accelerates the electrons emitted from the heated filament with an acceleration voltage applied between the anode and the electron gun and irradiates the sample 5. The electron beam 2 indicates a traveling route along which electrons travel due to this irradiation. The electron gun 1 can also be a Schottky electron gun.

  The deflection coil 17 forms a deflection magnetic field that two-dimensionally scans the electron beam 2 in two vertical and horizontal directions in a plane substantially orthogonal to the traveling direction. Here, the deflection magnetic field moves the position on the surface of the sample 5 where the electron beam 2 is irradiated vertically and horizontally. The deflection coil 17 performs this two-dimensional movement using two coils whose magnetic field directions are orthogonal.

The objective lens 4 is a coil that focuses the electron beam 2 emitted from the electron gun 1 with a spread, and has a focal position on, for example, the surface of the sample 5 on the traveling path of the electron beam 2.
The detector 7 is constituted by a semiconductor detector, for example, and detects backscattered electrons scattered from the sample 5 by the electron beam 2 irradiated on the sample 5.

  The sample stage 6 is an XY stage on which a sample 5 such as a semiconductor wafer is placed at the irradiation position of the electron beam 2. The XY stage is moved in the XY direction substantially orthogonal to the traveling direction of the electron beam 2, and the sample 5 is placed at a position desired by the operator while being position-controlled by the sample table control unit 9.

  The power supply control unit 10 controls the acceleration voltage of the electron gun 1, the driving current for driving the deflection coil 17 and the objective lens 4, etc., controls the electron energy of the electron beam 2, scans the electron beam 2 in the xy direction, and the electrons The focus position of the beam 2 is controlled.

  The control unit 11 generates, accelerates, and scans the electron beam 2 and further detects the backscattered electrons and the like so that the operation is appropriately performed at the timing intended by the operator. And the sample stage controller 9 is controlled.

  The input unit 13 includes a keyboard or the like, and various control information is input by an operator. The display unit 12 includes a display such as an LCD, and displays control information input from the input unit 13 or image information of the sample 5 obtained by scanning the electron beam inspection apparatus 99.

  The information processing unit 8 includes an arithmetic processing unit such as a CPU and a storage unit in terms of hardware, inputs backscattered electron scattering information from the sample 5 detected by the detector 7, and from this input information, A substance having a structural defect such as a deposit on the surface of the sample 5 is identified. FIG. 2 is a functional block diagram illustrating a functional configuration of the information processing unit 8. The information processing unit 8 includes emission efficiency calculation means 21, scattering change information 23, substance information acquisition means 22, candidate substance information 24, substance identification means 28, memory 26, and image formation means 27. Here, the emission efficiency calculating means 21, the substance information acquiring means 22, the substance identifying means 28, the memory 26, and the image forming means 27 are controlled from the control unit 11 by a signal line (not shown). These functions will be described in detail in the operation of the electron beam inspection apparatus 99.

  Next, the operation of the electron beam inspection apparatus 99 according to the present embodiment will be described with reference to FIG. FIG. 3 is a flowchart showing the operation of the electron beam inspection apparatus 99. First, the operator places the sample 5 which is a semiconductor wafer on the sample stage 6 (step S301). Here, the arrangement position of the sample 5 is set so that the scanning region of the electron beam 2 scanned on the sample 5 includes structural defects such as deposits existing on the sample 5. Note that the position of the structural defect on the semiconductor wafer is specified in advance using an inspection device such as an optical microscope in an inspection performed in each process of semiconductor manufacturing.

  Thereafter, the operator sets the acceleration voltage of the electron beam 2 (step S302). Here, the acceleration voltage is set by the power supply control unit 10 such that the electron energy of the electron beam 2 becomes 0.5 keV, for example.

  Thereafter, the electron beam inspection apparatus 99 performs scanning while irradiating the sample 5 with the electron beam 2 and detects the backscattered electrons 14 generated from the sample 5 by the detector 7 (step S303). At this time, the detector 7 transfers scattered information indicating the intensity of the detected backscattered electrons 14 to the information processing unit 8. This scattering information is displayed as a two-dimensional image as shown in FIG. 11A, for example, when scanning is performed on a plane on the sample 5.

  Thereafter, the information processing unit 8 calculates the average value S and the variation ΔS of the radiation efficiency in the region where the structural defect exists based on the scattering information from the detector 7 by the emission efficiency calculating unit 21 (step S304). Here, the emission efficiency calculating means 21 converts the scattering information indicating the intensity of the input backscattered electrons into radiation efficiency. Here, the emission efficiency is the amount of scattered electrons back-scattered with respect to a predetermined amount of the electron beam 2 irradiated on the sample 5, and has a value specific to the substance present at the irradiation position.

  Further, the backscattered electrons are electrons scattered by the atoms constituting the sample and having high energy of 50 eV or more. Here, since the backscattered electrons have high energy, they have high straightness. Therefore, the backscattered electrons detected by the detector 7 are only a part of the backscattered electrons generated radially at the position where the electron beam 2 of the sample 5 is irradiated.

Here, the emission efficiency is obtained by correcting the intensity information using a solid angle obtained by viewing the electron-sensitive area of the detector 7 from the irradiation position of the sample 5 irradiated with the electron beam 2. In this correction, when the emission efficiency is ε, the intensity information is r, and the solid angle is Ω,
ε∝r / Ω
It is calculated using the following relational expression. The solid angle Ω is determined by the shape of the detector 7 and the position where the detector 7 is arranged, and is input in advance from the input unit 13 by the operator.

  Further, the emission efficiency variation ΔS occurs due to variations in scattering information detected at a plurality of points at different irradiation positions of the electron beam 2. The magnitude of the variation ΔS is, for example, the standard deviation with respect to the average value S having the variation in emission efficiency. Here, the variation ΔS is calculated from the scattering information from the irradiation position where the same substance exists, that is, the average value S of the emission efficiency. For example, in the example of the profile of the scattering intensity as shown in FIG. 11B, the region where the emission efficiency exceeds the threshold is the calculation region 51 made of the same substance, and the variation in the emission efficiency S calculated in the calculation region 51 is The variation ΔS is calculated. The calculation area 51 can be set manually by the operator in the profile example as shown in FIG.

  After that, the information processing unit 8 determines candidate substances by using the average value S and the variation ΔS of the emission efficiency of the calculation region 51 where the same substance exists by the substance information acquisition unit 22 (step S305). In determining the candidate substance, the scattering change information 23 is referred to. The scattering change information 23 is information indicating the variation in the emission efficiency when the irradiation energy of the electron beam 2 is changed for each candidate substance that may exist on the surface of the sample 5.

  FIG. 4 is an explanatory diagram showing the scattering change information 23 in a graph. The horizontal axis represents the irradiation energy of the electron beam 2, and the vertical axis represents the backscattered electron emission efficiency. Here, examples of candidate substances include aluminum Al, copper Cu, carbon C, and silicon Si that cause structural defects in the semiconductor manufacturing process. In the semiconductor manufacturing process, candidate substances that cause structural defects are relatively limited, and the above-described substances occupy the main part of the candidate substances.

  Here, aluminum Al, copper Cu, carbon C, and silicon Si have different emission efficiencies for each element, and the emission efficiencies fluctuate with changes in irradiation energy. In particular, copper Cu, unlike other elements, increases the radiation efficiency as the irradiation energy increases, and the difference in radiation efficiency from other elements increases.

  The substance information acquisition unit 22 refers to the scattering change information 23 and determines a candidate substance based on the average value S and the variation ΔS of the emission efficiency obtained in step S304 (step S305). In FIG. 4, the average value S and the variation ΔS of the emission efficiency obtained in step S <b> 304 are displayed as error bars 31 on the graph of the scattering change information 23. The error bar 31 is a line segment in which the range of the variation ΔS centered on the average value S of the radiation efficiency is shown at the position where the irradiation energy is 0.5 keV. Here, the substance information acquisition unit 22 uses, as candidate substances, two candidate substances, copper Cu and aluminum Al, present in the range indicated by the line segment of the error bar 31 from the graph of the scattering change information 23 shown in FIG. decide. The name of the candidate substance is stored as candidate substance information 24 in the memory 26.

  Thereafter, the operator or the control unit 11 determines whether or not the candidate substance information 24 is sufficient for identifying a substance having a structural defect (step S306). If not enough (No at step S306), the power source control unit 10 to change the acceleration voltage (step S307), and the process proceeds to step S303. Then, scanning of the electron beam 2 in steps S303 to S305, irradiation and detection, calculation of emission efficiency and variation, and determination of candidate substances are repeated, and candidate substance information having different electron energies is acquired.

  Here, the electron energy of the electron beam 2 is changed to 1.5 keV, and the average value S and the variation ΔS of the emission efficiency of the sample 5 obtained from the same calculation region 51 are shown as error bars 41 on the graph of FIG. . The error bar 41 is a line segment in which the range of the variation ΔS centered on the average value S of the radiation efficiency is shown at the position where the irradiation energy is 1.5 keV. Here, the substance information acquisition unit 22 uses, as candidate substances, two candidate substances existing within the range indicated by the line segment of the error bar 41, silicon Si and aluminum Al, from the graph of the scattering change information 23 shown in FIG. decide. The names of the candidate substances are stored as candidate substance information 25 in the memory 26.

  In addition, when the candidate substance information 24 is sufficient for identifying a substance having a structural defect (Yes in step S306), the operator or the control unit 11 uses the substance identification unit 28 of the information processing unit 8 to obtain candidate substance information. By comparison, a substance having a structural defect is identified (step S308). Here, the substance identification means 28 reads the candidate substance information 24 and 25 from the memory 26, and compares the copper Cu and aluminum Al contained in the candidate substance information 24 with the silicon Si and aluminum Al contained in the candidate substance information 25. In addition, the aluminum Al contained in common is identified as a substance that causes a structural defect. When the control unit 11 performs the determination in step S306, this determination criterion is set by obtaining an input from the input unit 13 or an algorithm as described above by calculation or the like.

  Thereafter, the information processing section 8 forms image information for displaying the substance name on the display section 12 in the image forming means 27 (step S309). As this image information, for example, as shown in FIG. 5, a backscattered electron image 111 is formed by overwriting the material name Al on the backscattered electron image 101 which is image information of the structural defect 102. In the backscattered electron image 111, the material name Al is overwritten on the backscattered electron image 101 shown in FIG. 11A, and the material name Al indicates the position of the structural defect 102 by an arrow.

  Further, as this image information, it is also possible to use information obtained by performing arithmetic processing among a plurality of scattering information acquired by changing the acceleration voltage. For example, in the case of the backscattered electron image 101 including the structural defect 102 as shown in FIG. 11A, the averaging is performed between the plurality of backscattered electron images 101 acquired by changing the acceleration voltage. This addition averaging reduces statistical noise included in the image and obtains a high-contrast backscattered electron image that emphasizes the structural defect 102. In addition, as a calculation process, not only an addition average but a difference, integration, etc. can be used according to the irradiation conditions changed.

Thereafter, the electron beam inspection apparatus 99 displays this image information on the display unit 12 via the control unit 11 (step S310), and ends this process.
As described above, in the present embodiment, the average value S of the emission efficiency including the variation ΔS of the calculation region 51 is obtained using the scattering information of the backscattered electrons generated from the sample 5 by the irradiation of the electron beam 2. Using the average value S and the variation ΔS, a plurality of candidate substances that form the structural defect of the sample 5 are selected, the electron energy of the electron beam 2 is changed, and the selection of the candidate substances is repeated. Therefore, even if the substance with a large variation ΔS cannot be identified with a single measurement, the structure with high accuracy can be identified. It is possible to identify a substance having a defect, and thus, it is possible to identify a substance at a low cost, at a high speed, and with high accuracy without using EDS or the like.

In the present embodiment, an example in which a semiconductor detector is used as the detector 7 is shown, but a scintillator, a channeltron, a multichannel plate, or the like can also be used.
In this embodiment, the scattering change information 23 as shown in FIG. 4 is acquired in advance, but a standard sample made of a candidate substance, such as copper Cu or aluminum Al, is used instead of the semiconductor wafer. The scattering change information 23 can be acquired by using the electron beam inspection apparatus 99. Furthermore, these standard samples can be juxtaposed on the surface of the sample stage 6 where no semiconductor wafer is present, and based on the scattering information from these standard samples, identification of substances or improvement of identification accuracy can be performed.

  FIG. 6 is a layout view showing the sample 5 and the standard sample 71 juxtaposed on the sample stage 6 as seen from the irradiation direction of the electron beam 2. The standard sample 71 includes a circular standard sample portion made of, for example, aluminum 72, copper 73, carbon 74, and silicon 75. By irradiating this portion with the electron beam 2, the scattering change information 23 of these substances is present. To get.

  In the present embodiment, it is assumed that the sample 5 and the detector 7 are in the positional relationship as shown in FIG. 1, and the detector 7 detects a part of the backscattered electrons scattered radially from the sample 5. However, by arranging the detector 7 in the vicinity of the sample 5, the detection efficiency of backscattered electrons can be increased, and the substance can be identified at high speed.

  FIG. 7 is a layout diagram illustrating an example in which the detector 7 is disposed in the vicinity of the sample 5. A lens barrel portion 81 shown in the figure is a vacuum container containing the electron gun 1, the deflection coil 17, the objective lens 4, and the like, and the electron beam 2 is irradiated from the exit outlet 82. Here, the detector 7 is disposed in the vicinity of the sample 5, while the sample stage 6 is disposed with an inclination with respect to a plane orthogonal to the irradiation direction of the electron beam 2. Thereby, it is possible to prevent the lens barrel portion 81 that emits the electron beam 2 from coming into contact with the detector 7 and to arrange the detector 7 in the vicinity of the sample 5. At this time, instead of tilting the sample stage 6, the lens barrel part 81 can be tilted so that the positional relationship between the sample stage 6 and the lens barrel part 81 is the same.

  In the present embodiment, it is assumed that the sample 5 and the detector 7 are in the positional relationship as shown in FIG. 1, and the detector 7 detects a part of the backscattered electrons 14 scattered radially from the sample 5. However, by providing a metal reflector near the electron beam 2 exit 82 of the lens barrel 81 described above, the detection efficiency of the backscattered electrons 14 can be improved, and the substance can be identified at high speed. it can.

  FIG. 8 is a cross-sectional view showing an example in which a reflecting plate 91 is arranged in the vicinity of the exit port 82 of the lens barrel portion 81. The reflection plate 91 has a ring-like structure, and the electron beam 2 passes through the center portion of the ring. A part of the backscattered electrons 3 of the sample 5 generated by the irradiation of the electron beam 2 is detected by the detector 7 and many other electrons collide with the reflector 91. At this time, the number of secondary electrons 92 proportional to the collided backscattered electrons 3 is emitted from the reflecting plate 91. Since the secondary electrons 92 have small initial energy and inferior linearity, they can be captured by the detector 7 by applying an electric field between the detector 7 and the reflecting plate 91. Thereby, the detector 7 can indirectly increase the detection efficiency of the backscattered electrons 3.

  In the present embodiment, the sample 5 and the detector 7 are in the positional relationship as shown in FIG. 1, and the backscattered electrons scattered upward of the sample 5 on which the electron beam 2 is incident are detected by the detector 7. However, another detector 16 is disposed closer to the surface of the sample 5 than the detector 7, and backscattered electrons scattered in the oblique direction of the sample 5 are detected by the detector 16. Can also be detected. Thereby, even when the thickness of the electron beam 2 in the irradiation direction of the structural defect of the sample 5 is small and the scattering information of the detector 7 includes the scattering information of the substance that is the base of the structural defect, Can be identified.

  FIG. 9 is a block diagram of an electron beam inspection apparatus 100 in which a detector 16 is added to the electron beam inspection apparatus 99. The detector 16 is a detector that detects the backscattered electrons 14 from the sample 5 in the same manner as the detector 7, but the arrangement position is set closer to the surface of the sample 5 than the detector 7. The As a result, the detector 16 detects the backscattered electrons 15 that are scattered in an oblique direction closer to the surface of the sample 5 than the backscattered electrons 14 incident on the detector 7.

  FIG. 10 is an explanatory diagram showing that the scattering information acquired by the detector 7 and the detector 16 differs depending on whether the structural defect of the sample 5 has a large thickness or a thin thickness. First, FIG. 10A is an explanatory diagram showing the relationship between the backscattered electrons generated in the thick structural defect 201 and the base 202 of the structural defect of the sample 5 and the scattering information acquired by the detector 7. By the irradiation of the electron beam 2, the structural defect 201 of the sample 5 and the base 202 of the structural defect generate backscattered electrons 203 to 206. Here, the backscattered electrons 203 and 204 are generated by the structural defect 201, and the backscattered electrons 205 and 206 are generated by the base 202. The backscattered electrons 203 and 205 are scattered in the direction in which the detector 7 exists, and the backscattered electrons 204 and 206 are scattered in the direction in which the detector 16 exists.

  Here, since the backscattered electrons 205 generated in the base 202 are blocked by the thick structural defect 201, the scattering information detected by the detector 7 is only the information of the backscattered electrons 203 generated in the structural defect 201. It will be included. Therefore, the material constituting the structural defect 201 can be identified by the information processing unit 8 described above.

  FIG. 10B is an explanatory diagram showing the relationship between backscattered electrons generated in the thin structural defect 207 and the base 202 of the structural defect of the sample 5 and scattering information acquired by the detector 7. By irradiation with the electron beam 2, the structural defect 207 of the sample 5 and the base 202 of the structural defect generate backscattered electrons 213 to 216. Here, the backscattered electrons 213 and 214 are generated by the structural defect 207, and the backscattered electrons 215 and 216 are generated by the base 202. The backscattered electrons 213 and 215 are scattered in the direction in which the detector 7 exists, and the backscattered electrons 214 and 216 are scattered in the direction in which the detector 16 exists.

  Here, the scattered information detected by the detector 7 is generated in the backscattered electrons 213 generated in the structural defect 207 and in the base 202 since the backscattered electrons 215 generated in the base 202 pass through the thin structural defect 207. The information of the backscattered electrons 215 to be included is included. Therefore, the information processing unit 8 described above cannot identify the substance constituting the structural defect 207.

  On the other hand, the scattering information detected by the detector 16 is that the backscattered electrons 214 generated by the underlying defects 202 are blocked by the thin scattered defects 207 traveling in the oblique direction. It will only contain information. Therefore, the scattering information detected by the detector 16 can identify the substance constituting the structural defect 207 by the information processing unit 8 described above.

  In the present embodiment, the substance name which is the identification information of the substance identified by the information processing unit 8 is displayed on the display unit 12. However, the information processing unit 8 is provided with a classification unit, and this substance name, Can classify this substance by, for example, generation factors based on position information, shape information, etc. of the substance on the sample 5. The position information and shape information of the substance can be obtained by inspection using an optical microscope or image processing using a backscattered electron image in the vicinity of the structural defect.

It is a block diagram which shows the whole structure of an electron beam inspection apparatus. It is a functional block diagram which shows the functional structure which the information processing part of an electron beam inspection apparatus has. It is a flowchart which shows operation | movement of an electron beam inspection apparatus. It is explanatory drawing which shows the content of the scattering change information which exists in an information processing part. It is a figure which shows an example of the image information which displays the substance name of a structural defect. It is an arrangement drawing showing arrangement of standard samples juxtaposed to a sample. It is an arrangement view showing an example in which a detector is arranged in the vicinity of an irradiation position on a sample. It is sectional drawing which shows an example which arrange | positions a reflecting plate in the injection port vicinity of a lens-barrel part. It is a block diagram which shows the whole structure of the electron beam inspection apparatus to which another detector was added. It is explanatory drawing which shows operation | movement of the electron beam inspection apparatus to which another detector was added. It is explanatory drawing which shows an example of the scattering information acquired by the detection of the backscattered electron of a sample.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electron gun 2 Electron beam 3, 14, 15 Backscattered electron 4 Objective lens 5 Sample 6 Sample stand 7, 16 Detector 8 Information processing part 9 Sample stand control part 10 Power supply control part 11 Control part 12 Display part 13 Input part 17 Deflection coil 21 Emission efficiency calculation means 22 Substance information acquisition means 23 Scatter change information 24, 25 Candidate substance information 26 Memory 27 Image formation means 28 Substance identification means 31, 41 Error bar 32 Variation 51 Calculation area 71 Standard sample 72 Aluminum 73 Copper 74 Carbon 75 Silicon 81 Lens barrel part 82 Exit 91 Reflecting plate 92 Secondary electron 99,100 Electron beam inspection apparatus 101, 111, 202-206, 213-216 Backscattered electron image 102, 201, 207 Structural defect 104 Silicon substrate 105 Copper pattern 202 Base

Claims (22)

Irradiate the surface of the sample with the primary electron beam generated by the electron gun,
Detecting scattering information of backscattered electrons generated from the surface during the irradiation;
Candidate substance information of candidate substances that are candidates when identifying substances present on the surface, based on the scattering information,
Change the irradiation conditions when performing the irradiation, repeat the irradiation, the detection and the acquisition,
Comparing the plurality of candidate substance information acquired by the repetition,
An electron beam inspection method for identifying the substance.   The electron beam inspection method according to claim 1, wherein the identification uses a candidate substance that is commonly included in a plurality of pieces of candidate substance information as the substance.   The electron beam inspection method according to claim 1, wherein the scattering information includes an emission efficiency of the backscattered electrons and a magnitude of variation in the emission efficiency.   The electron beam inspection method according to claim 1, wherein the irradiation condition is an acceleration voltage of the primary electron beam.   The electron beam inspection method according to any one of claims 1 to 4, wherein the acquisition is performed with reference to scattering change information indicating a change in scattering information accompanying the change for each candidate substance. .   The electron beam inspection method repeats the irradiation and detection with the change on a candidate material sample made of the candidate material, and acquires the scattering change information in advance before performing the irradiation and detection of the sample. The electron beam inspection method according to claim 5.   7. The electron beam inspection method according to claim 1, wherein image information on a surface of a sample including the substance and a region near the substance is collected based on position information of the substance. The electron beam inspection method described in 1.   The electron beam inspection method according to claim 7, wherein the electron beam inspection method performs arithmetic processing on the plurality of pieces of scattering information to form image information in which a contrast of the substance is emphasized.   9. The electron beam inspection method according to claim 1, wherein the candidate substance is selected before the identification, and the identification is performed on the candidate substance that has been selected. The electron beam inspection method as described in one.   10. The electron beam inspection method according to claim 1, wherein the substance is classified based on identification information of the substance, position information of the substance, and shape information of the substance. Electron beam inspection method. An irradiation means for irradiating the surface of the sample with a primary electron beam generated by an electron gun;
A detector for detecting scattering information of backscattered electrons generated from the surface during the irradiation;
Substance information acquisition means for acquiring candidate substance information of candidate substances that become candidates when identifying substances present on the surface, based on the scattering information;
A control unit that changes the irradiation conditions when performing the irradiation, and repeats the irradiation, the detection, and the acquisition;
A plurality of candidate substance information obtained by the repetition, comparing substance information, and identifying the substance,
An electron beam inspection apparatus comprising:   The electron beam inspection apparatus according to claim 11, wherein the detector includes a plurality of detectors having angles different from an irradiation direction in which the irradiation is performed.   The electron beam inspection apparatus according to claim 12, wherein at least one of the detectors is disposed in the vicinity of the surface.   The electron beam inspection apparatus according to any one of claims 11 to 13, wherein the detector includes a sample stage on which the sample is placed and a lens barrel part that includes the irradiation unit.   The electron beam inspection apparatus according to claim 14, wherein the sample stage juxtaposes a standard sample made of the candidate substance together with the sample.   The detector has a finite value of a crossing angle between a mounting surface on which the sample is placed on the sample stage and an orthogonal surface orthogonal to the irradiation direction of the primary electron beam irradiated from the lens barrel. The electron beam inspection apparatus according to claim 14, further comprising an arrangement unit that arranges a detector that performs the detection in the vicinity of an irradiation position of the sample.   The said detector is provided with the reflecting plate which collides the said backscattered electron, and the secondary electron detector which detects the secondary electron generated with the said reflecting plate, The any one of Claim 11 thru | or 16 characterized by the above-mentioned. The electron beam inspection apparatus according to one.   The electron beam inspection apparatus according to claim 17, wherein the reflecting plate has a ring-shaped structure surrounding the primary electron beam.   19. The electron beam inspection apparatus includes a classification unit that classifies the substance based on identification information of the substance, position information of the substance, and shape information of the substance. Electron beam inspection apparatus as described in one.   The electron beam inspection apparatus according to claim 11, further comprising an image forming unit that forms image information obtained by performing arithmetic processing on the scattering information.   21. The electron beam inspection apparatus according to claim 11, further comprising display means for displaying a substance name of the identified substance.   The electron beam inspection apparatus according to claim 20 or 21, wherein the display means displays the image information and overwrites the substance name on the displayed image.

Images