JP6366127B2 - Electron beam apparatus, sample observation method - Google Patents

Description

  The present invention relates to an electron beam apparatus and a sample observation method, and more particularly to a technique that enables high-precision observation of a minute concave portion of a sample.

  Wafers (semiconductor substrates) on which circuit patterns used for semiconductor elements and the like are formed have deep grooves for forming fine conductive patterns, contact holes for connecting conductive patterns stacked in the thickness direction, and the like. Is formed. When inspecting wafers with such deep grooves and contact holes, it is necessary to accurately observe the side walls of the deep grooves and contact holes along the thickness direction of the wafer and detect defects present on these side walls. Has occurred.

  Conventionally, in an electron beam inspection apparatus used for wafer inspection, an electron beam is incident on a deep groove or a contact hole, and all secondary electrons emitted in various directions are detected collectively (for example, Patent Document 1).

JP 2005-121635 A

  In conventional detection methods that detect all secondary electrons emitted from wafers at various angles in a uniform manner, electrons are emitted from deep grooves and contact holes at the bottom and side walls. It was difficult to accurately sort out whether it was released. Further, even if a change in the signal intensity of the secondary electrons is detected, it is difficult to specify at which depth position of the deep groove or the contact hole the defect exists. Furthermore, in the method of detecting all secondary electrons uniformly, the signal at the edge of the deep groove or contact hole existing near the surface layer of the wafer is emphasized, so the state of the side wall of the deep groove or contact hole is observed. It was difficult.

  Secondary electrons emitted from the side walls of deep grooves and contact holes are generated when reflected electrons generated by an incident electron beam enter the side walls. Therefore, the amount of secondary electrons generated on the side wall is extremely small, resulting in a weak signal. For this reason, it is extremely difficult to detect such weak secondary electrons from the side wall with a conventional detector having a gain optimized for detecting a signal of secondary electrons generated from the surface of the wafer. Therefore, in order to precisely observe the side walls of deep grooves and contact holes, a detector having a gain capable of detecting weak secondary electrons is essential.

    The present invention has been made in view of the above problems, and an object thereof is to provide an electron beam apparatus and a sample observation method capable of accurately observing the state of the side wall of a fine recess formed in a sample. To do.

In order to solve the above problems, some aspects of the present invention provide the following electron beam apparatus and sample observation method. That is, the electron beam apparatus of the present invention comprises an electron beam optical system that irradiates an electron beam toward a fine concave portion formed in a sample , and a detection system that detects secondary electrons generated by reflected electrons of the electron beam. An electron beam optical element is provided, and the detection system includes a detector in which a plurality of detection elements are arranged, and the secondary electrons are generated according to the formation position of the detection element that has detected the secondary electrons. In addition, a gain control unit that specifies a position in the concave portion and an SEM image forming circuit that generates image information including a side wall along the depth direction of the concave portion are provided .

The sample observation method of the present invention includes an electron beam optical element including an electron beam optical system that irradiates an electron beam on a sample surface and a detection system that detects secondary electrons generated by reflected electrons of the electron beam, and the detection The system includes a detector having a plurality of detection elements arranged, and uses the electron beam apparatus that detects the secondary electrons by the different detection elements according to the emission angle of the secondary electrons, and uses the sample. A sample observation method for observing
An irradiation step of selectively irradiating the electron beam toward a fine recess formed in the sample, a step of detecting the secondary electrons by the detector, and the detection element detecting the secondary electrons And a step of identifying a position in the recess where the secondary electrons are generated according to a formation position of the image, and a step of generating image information including a side wall along the depth direction of the recess. It is characterized by.

  A step of individually setting individual gains of the detection elements, and a step of adding signals detected by the individual detection elements to obtain a high-definition image of a side wall along the depth direction of the recess. It is characterized by that.

  The method further includes a step of calculating a difference between signals detected by the individual detection elements to obtain a high-definition image of a specific region in the recess.

  The method further comprises the step of irradiating the entire surface of the sample with the electron beam and detecting in advance the position of the recess in the sample.

  According to the electron beam apparatus of the present invention, the sample is provided with a detector formed by arranging a plurality of detection elements, and the secondary electrons are detected by the detection elements different from each other according to the emission angle of the secondary electrons. It is possible to accurately and highly accurately observe the state of the side wall of the minute recess formed in.

  In addition, according to the sample observation method of the present invention, an electron beam is selected toward a minute concave portion formed in the sample and its peripheral portion using an electron beam apparatus having a detector in which a plurality of detection elements are arranged. The position of the side wall of the fine recess formed in the sample is determined by specifying the position in the recess where the secondary electron is generated according to the position where the detection element that has detected the secondary electron is irradiated. It becomes possible to observe with high accuracy.

1 is a schematic diagram showing an electron beam apparatus according to a first embodiment of the present invention. It is a schematic block diagram which shows the cross section along the longitudinal direction of an electron beam column. It is a schematic block diagram which shows the structure of a secondary electron beam detector. It is sectional drawing which shows the mode of the secondary electron discharge | released from a deep groove. It is a graph which shows distribution according to the emission angle of a secondary electron. It is a schematic diagram which shows the mode of discharge | release of the secondary electron which arises in a side wall. It is a schematic diagram which shows the mode of the secondary electron discharge | released from a side wall, scanning an electron beam. It is a block diagram which shows the structure for setting the gain of a secondary electron beam detector. It is a schematic diagram which shows the example of observation of the recessed part by this invention. It is a photograph which shows the example of observation of the recessed part by this invention. It is the flowchart which showed the sample observation method of this invention in steps. It is the flowchart which showed another sample observation method of this invention in steps. It is sectional drawing which shows the electron beam column of the electron beam apparatus in 2nd embodiment of this invention.

  A semiconductor wafer inspection apparatus using an electron beam will be described below as an embodiment of an electron beam apparatus according to the present invention with reference to the drawings. The present embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified. In addition, in the drawings used in the following description, in order to make the features of the present invention easier to understand, there is a case where a main part is shown in an enlarged manner for convenience, and the dimensional ratio of each component is the same as the actual one. Not necessarily.

(Electron Beam Device: First Embodiment)
FIG. 1 is a schematic diagram showing the overall configuration of the electron beam apparatus according to the present embodiment.
The electron beam apparatus (inspection apparatus) 10 of the present invention includes a chamber unit 11, an electron beam column 21 accommodated in the chamber unit 11, a control power source 3 connected to the electron beam column 21, and these control power sources 31. And a computer 41 connected to the computer.

  The chamber unit 11 includes a first chamber (wafer chamber) 12, a second chamber (intermediate chamber chamber) 13, and a third chamber (electron gun chamber chamber) 14. The first chamber 12, the second chamber 13, and the third chamber 14 form independent spaces that can be set to different degrees of vacuum, and are arranged adjacent to each other.

  The first chamber 12, the second chamber 13, and the third chamber 14 are connected to vacuum pumps 15, 16, and 17 for making the inside have a predetermined degree of vacuum, respectively. The electron beam column 21 is disposed so as to penetrate the first to third chambers 12, 13, and 14. The configuration of the electron beam column 21 will be described in detail later.

  In the first chamber (wafer chamber) 12, for example, a stage 18 for placing a wafer (sample) W having a semiconductor integrated circuit formed on the surface layer is disposed. A wafer (sample) W that is an object to be inspected is placed on one surface of the stage 18. The stage 18 is formed so as to be movable in any direction along the main surface of the wafer W, and moves the wafer W along a predetermined direction at a predetermined moving speed during inspection. In the semiconductor integrated circuit formed on the wafer W, concave portions such as deep grooves and contact holes are formed.

  The control power supply 31 inputs a scan voltage input to the electron beam column 21. Examples of the signal output from the control power supply 31 include a high voltage current and a high frequency current. The control power supply 31 is preferably further provided with a correction mechanism. This correction mechanism performs, for example, correction of a phase shift of a signal output from the control power supply 31, for example, a high-frequency voltage, correction of a waiting time of a scanning signal, switching of a control current circuit such as a filter, and the like.

  The computer 41 inputs a control command for the electron beam column 21, and also obtains a secondary electron beam reflecting the shape of a wiring pattern including a concave portion such as a deep groove or a contact hole obtained by irradiating the wafer W with an electron beam. An image of the wiring pattern is formed based on the output signal (secondary electron beam). When such an electron beam apparatus 10 is used as a circuit pattern inspection apparatus, the computer 41 compares images of a plurality of wiring patterns and detects whether there is a difference between the images. If there is a difference in the comparison between the images, it may be configured to output as a circuit pattern formation abnormality.

FIG. 2 is a schematic configuration diagram showing a cross section along the longitudinal direction of the electron beam column.
The electron beam column 21 includes a substantially cylindrical outer package 22 having an elongated outer shape. The exterior body 22 is made of, for example, a metal cylinder and has a structure in which a central axis is mechanically secured. Examples of the metal material include stainless steel, iron, phosphor bronze, aluminum, and titanium. Furthermore, it is also preferable that a magnetic shield made of an alloy having a high magnetic permeability such as permalloy or mu metal is additionally provided. The exterior body 22 is provided with a plurality of vent holes (not shown) for evacuating the interior of the exterior body 22. The degree of vacuum in the region through which the electron beam passes can be increased by the vent hole.

  A plurality of electron beam optical elements are accommodated in the exterior body 22 of the electron beam column 21. That is, the electron gun 51, the condenser lens 52, the electron beam aperture mechanism 53, the optical axis adjustment mechanism 54, the blanking electrode 55, the secondary electron beam detector 56, the scan electrode 57, and the objective lens 69 are sequentially arranged from the top of the exterior body. Etc. are provided inside the exterior body 22. Among these, the secondary electron beam detector 56 constitutes a detection system, and the electron beam optical elements excluding this detection system constitute an electron beam optical system.

As the electron gun 51, for example, a Schottky type or a thermal field emission type electron gun is used. By applying an acceleration voltage to the electron gun 51, an electron beam (electron beam) E is emitted. The electron beam E emitted from the condenser lens 52, the electron beam diaphragm mechanism 53, and the electron gun 51 is condensed and adjusted so as to obtain a desired current.
The optical axis adjustment mechanism 54 adjusts the beam astigmatism, the beam position on the optical axis, and the beam irradiation position on the sample.

  The secondary electron beam detector (detector) 56 constituting the detection system is configured to irradiate the wafer W with the electron beam E, and emit the secondary electron beam R emitted according to the deep grooves, contact holes, etc. formed in the wafer W. Detect and output as a high voltage, high frequency detection signal (secondary electron signal). Such a detection signal is taken out of the electron beam column 21 via the transmission mechanism 58. The extracted output signal of the secondary electron beam detector 56 is amplified by, for example, a preamplifier and converted into image digital data of a circuit pattern by an AD converter. Such image digital data is input to the computer 41 (see FIG. 1). The detailed configuration of the secondary electron beam detector 56 will be described in detail later.

  The scan electrode 57 (electron beam optical element) deflects the electron beam E by introducing (applying) a high-frequency control signal (electric signal), for example, a high-frequency current of 0 to 400 V from the outside. By applying an arbitrary control signal to the scan electrode 57, the electron beam E is deflected, and the electron beam E can be scanned along an arbitrary direction on the main surface of the wafer W. Such a high-frequency control signal is introduced into the scan electrode 57 from the outside of the electron beam column 21 via the transmission mechanism 58. The objective lens 69 focuses the electron beam E deflected by the scan electrode 57 on the main surface of the wafer W.

  With such a configuration, the electron beam E emitted from the electron gun 51 is scanned on the main surface of the wafer W, and the secondary grooves reflecting the deep grooves formed on the wafer W, the shape of the contact holes, the composition, the charging state, and the like are reflected. The electron beam R is detected by a secondary electron beam detector 56 (detection system). A circuit pattern including a deep groove and a contact hole formed on the main surface of the wafer W by processing a detection signal of the detected secondary electron beam R by the computer 41 via a preamplifier or an AD converter, for example. Get the image.

  These electron beam optical elements and the stage 18 are accommodated in chambers corresponding to the required degree of vacuum among the chambers constituting the chamber unit 11. That is, the electron gun 51 and the condenser lens 52 that require the highest degree of vacuum to emit the electron beam E are disposed in the third chamber (electron gun chamber chamber) 14 in which the inside is set to the highest degree of vacuum. The The electron beam diaphragm mechanism 53, the optical axis adjusting mechanism 54, and the blanking electrode 55 are disposed in the second chamber (intermediate chamber chamber) 13 having a high degree of vacuum next to the third chamber 14. The secondary electron beam detector (detection system) 56, the scan electrode 57, the objective lens 69, and the stage 18 on which the wafer W is placed are disposed in the first chamber (wafer chamber) 12 having a relatively low degree of vacuum. The Thereby, it is not necessary to make all the electron beam optical elements, the stage 18 and the wafer W into a high vacuum environment of a level necessary for emitting the electron beam E.

Next, the secondary electron beam detector (detector) 56 will be described in more detail.
FIG. 3 is a schematic configuration diagram showing the configuration of the secondary electron beam detector in a cross section along the longitudinal direction of the electron beam column.
The secondary electron beam detector (detector) 56 is formed by arranging a plurality of detection elements 71, 71. That is, the secondary electron beam detector 56 is divided into a plurality of detection elements 71, 71. Each detection element 71 includes, for example, a scintillator and a photomultiplier tube. The individual detection elements 71 detect secondary electrons independently of each other and output their intensity signals.
Further, the secondary electron beam detector (detector) 56 may be constituted by a semiconductor detector in which a plurality of detection elements 71, 71... Are formed.

  The plurality of detection elements 71, 71,... Are arranged in a line, for example, parallel to the surface of the stage 18, or arranged in a plane so as to spread in the X direction and the Y direction, or an incident electron beam passes therethrough. It only has to be arranged concentrically around the hole. Between the detection elements 71 and 71 arranged adjacent to each other, the detection elements 71 and 71 are arranged in close contact with each other so that no gap is formed on the detection surface on which the secondary electrons are incident.

  In this way, by configuring the secondary electron beam detector 56 from an array of a plurality of detection elements 71, 71..., The detection elements 71, 71 at different positions according to the emission angle of secondary electrons. It becomes possible to detect secondary electrons at 71. That is, it becomes possible to specify the emission angle of the secondary electrons according to the arrangement position of the detection element 71 that has detected the secondary electrons.

 The secondary electrons generated when the backscattered electrons generated from the concave portion formed on the wafer, for example, the bottom of the deep groove collide with the side wall of the deep groove, are emitted at an angle depending on the width of the deep groove and the position in the depth direction of the side wall. Determined.

For example, according to the cross-sectional view of the deep groove shown in FIG. 4, the width of the deep groove P is a, the depth of the deep groove P is b, and the angle of secondary electrons emitted from an arbitrary depth position x of the side wall S is θ. In order for the secondary electrons emitted from the side wall S to escape from the deep groove P, it is necessary to be emitted within the range shown in the following formula (1).
0 <θ <tan ⁻¹ (a / (b−x)) (1)
FIG. 5 shows the relationship between the number of secondary electrons emitted from the deep groove in a certain angle range and the position (depth position) x from the bottom of the deep groove, and shows the distribution according to the emission angle of the secondary electrons. It is shown.

 Based on these secondary electron emission characteristics, the secondary electrons emitted in a certain angle range are selected and detected, so that detailed information on the specific depth range in the concave part (deep groove or contact hole) of the sample can be obtained. Can be obtained. Further, by detecting secondary electrons of two different angles from each other and calculating the difference between them, it is possible to more accurately detect the depth position of the concave portion from which the secondary electrons have been emitted.

 By these secondary electron detection methods, it is possible to reduce the strong signal of secondary electrons generated near the edge of the recess on the surface of the sample, and to obtain information including the structure at an arbitrary depth position on the sidewall of the recess. Become.

 FIG. 6 is a schematic diagram showing a state of secondary electron emission generated at the side wall when the bottom of the deep groove is irradiated with an electron beam. According to this, the secondary electrons irradiated to the bottom B of the deep groove P are reflected by the bottom B, and the reflected electrons enter the side wall S. Secondary electrons generated from the side wall S by the reflected electrons are emitted at different angles depending on the depth position in the side wall S. The secondary electrons emitted at different angles are detected by different detection elements 71, 71... According to the emission angles.

For example, in the schematic diagram shown in FIG. 6, secondary electrons whose emission angles are in the range of θ ₁ to θ ₂ are detected by the detection element 71 a. Further, the secondary electrons in the range of emission angles θ ₃ to θ ₄ are detected by the detection element 71b, and the secondary electrons in the range of emission angles of θ ₅ to θ ₆ are detected by the detection element 71c. Thereby, each of the plurality of detection elements 71, 71... Constituting the secondary electron beam detector 56 is associated with the emission angle of secondary electrons, and detailed information on the side wall S of the deep groove P, for example, the side wall surface It is possible to construct a fine electron microscope image.

 Further, for example, as shown in FIG. 7, a specific depth in the side wall S of the deep groove P is detected by detecting secondary electrons emitted from the side wall S while scanning the electron beam along the bottom B of the deep groove P. It is also possible to obtain detailed information.

  Secondary electrons emitted from the side walls and contact holes of deep grooves are generated by reflected electrons reflected from the bottom of the electron beam. Therefore, the number of emitted electrons is extremely small, and weak signals of secondary electrons are detected with high sensitivity. This is very important. Therefore, the detection elements 71, 71,... Constituting the secondary electron beam detector 56 can independently set the gain.

FIG. 8 is a configuration diagram showing a configuration for setting the gain of the secondary electron beam detector.
.. Are connected to a plurality of detection elements 71, 71... Constituting the secondary electron beam detector 56, respectively. Each gain control unit 72 includes a gain switching circuit 73 and a plurality of, for example, three gain circuits 74a, 74b, and 74c. The gain circuits 74a, 74b, and 74c amplify the input secondary electron detection signal with a predetermined gain (gain) width. The gain circuits 74a, 74b, and 74c have different gain (gain) widths. For example, the gain circuit 74a has the smallest amplification with respect to the detection signal of the input secondary electrons, and the gain circuit 74c has the amplification. The biggest.

  The gain switching circuit 73 selects any one of the gain circuits 74a, 74b, and 74c and outputs a secondary electron detection signal. With such a gain control unit 72, the gain circuits 74a, 74b, 74c are individually associated with each of the plurality of detection elements 71, 71..., And the gain of each detection element 71 can be set independently.

  For example, when secondary electrons emitted at all emission angles are measured together with the same gain, the signal of each angle component is weak, so it is buried in the signal from the surface with a strong signal intensity, It is extremely difficult to selectively detect a signal of secondary electrons emitted from an angle with sufficient intensity. Therefore, as shown in FIG. 8, the secondary electron beam detector 56 is divided into a plurality of detection elements 71, 71... And the gain can be switched for each detection element 71. Only secondary electrons can be selectively detected.

  A weak detection signal of secondary electrons emitted from the side wall of the recess (deep groove or contact hole) is converted into a high gain for each detection element 71 by the gain circuits 74a, 74b, and 74c constituting the gain control unit 72. Is done. The individual gain control units 72 correspond to the individual detection elements 71 on a one-to-one basis and do not interlock with the other gain control units 72, so that a desired gain is set independently for each individual detection element 71. It becomes possible.

Thereby, for example, an angle in which only a secondary electron component emitted at a specific angle is measured with high sensitivity by setting a gain high by an arbitrary detection element 71 and setting other detection elements 71 low. Sorting becomes possible. As a specific example, a high-definition electron microscope image of only a specific region of the side wall can be obtained. As a specific selection range of the gain by the gain control unit 72, for example, it is possible to make it variable between 10 ^{3 and} 10 ¹² .

  An SEM image configuration circuit 75 is connected to the output side of the gain control unit 72. The SEM image construction circuit 75 has an arithmetic function capable of adding or subtracting amplified secondary electron detection signals output from the respective gain control units 72, 72.

  For example, the SEM image construction circuit 75 adds the detection signal of the secondary electrons in the first emission angle range and the detection signal of the secondary electrons in the second emission angle range, so that only a specific angle component is obtained. First, it is possible to construct an SEM observation image of an arbitrary region on the surface, bottom, or side wall of a deep groove or contact hole. In addition, the SEM image forming circuit 75 subtracts the detection signal of the secondary electrons in the first emission angle range and the detection signal of the secondary electrons in the second emission angle range, for example, to obtain a specific angle component. The secondary electron detection signal can be emphasized, and a high-definition SEM observation image at a specific depth position on the side wall of the deep groove or contact hole can be constructed.

  Although FIG. 8 shows an example in which the gain is switched in three stages, the gain may be switchable in two stages or four or more stages. Or you may make it the structure which can switch a gain not stepwise but continuously.

  The secondary electron beam detector 56 is divided into a plurality of detection elements 71, 71... And an electron beam apparatus (inspection apparatus) 10 in which a gain control unit 72 is connected to each detection element 71. The contact hole having the shape shown in FIG. In FIG. 9A, the side wall S of the contact hole P is flat. On the other hand, in FIG. 9B, a concave structure (defect) V is formed in a portion of the side wall S of the contact hole P away from the surface.

  FIG. 10 shows SEM observation images of the deep groove shown in FIG. 9A and the deep groove shown in FIG. 10A is an SEM observation image of the defect-free contact hole shown in FIG. 9A, and FIG. 10B is a contact hole having a defect on the side wall shown in FIG. 9B. It is a SEM observation image of this. As described above, when the side wall of the contact hole is observed using the electron beam apparatus 10 of the present invention, the amount of emitted electrons is different, and the presence or absence of defects makes it difficult to observe with the conventional electron beam apparatus. Since it is emphasized as an SEM observation image, it is possible to detect a defect present on the side wall of the contact hole.

(Sample observation method: first embodiment)
The sample observation method of the present invention using the above-described electron beam apparatus will be described.
FIG. 11 is a flowchart showing the sample observation method of the present invention step by step. This sample observation method is an example in which detailed information on a recess is obtained by selectively irradiating an electron beam toward the bottom surface of the recess.
First, an electron beam is irradiated to the whole sample including a recessed part. Thereby, the position and surface shape of the recessed part in a sample are observed (S1).
Next, a gain (gain) when observing the concave portion is set for each detection element constituting the secondary electron beam detector (S2). The gain can be set by controlling the gain switching circuit of the gain controller. The selection of the gain for each detection element may be determined with reference to the surface shape of the recess obtained by observing the entire sample.

  Next, the electron beam is selectively focused and irradiated toward the bottom surface of the concave portion of the sample (S3). The electron beam incident on the bottom is reflected, and when the reflected electrons hit the side wall, secondary electrons are emitted at a predetermined emission angle according to the position. The emitted secondary electrons are incident on different detection elements according to the emission angle. And the detection signal amplified according to the gain set for each detection element is output.

  Next, the sum and difference of the detection elements are calculated (S4). And the signal (S5) in which the specific position of the side wall is emphasized, the signal (S6) in which the bottom surface of the concave portion is emphasized, and the signal (S7) in which the surface of the concave portion is emphasized are obtained. Based on such a signal, by constructing an electron microscope image of the concave portion, detailed information (fine shape and defect) on the side wall and bottom surface of the concave portion can be obtained.

(Sample observation method: second embodiment)
FIG. 12 is a flowchart showing stepwise the sample observation method of the present invention using a scanning electron microscope.
First, an electron beam is irradiated to the whole sample including a recessed part. Thereby, the position and surface shape of the recessed part in a sample are observed (S11).
Next, a gain (gain) when observing the concave portion is set for each detection element constituting the secondary electron beam detector (S12). The gain can be set by controlling the gain switching circuit of the gain controller. The selection of the gain for each detection element may be determined with reference to the surface shape of the recess obtained by observing the entire sample.

  Next, the concave portion of the sample is irradiated while scanning with an electron beam (S13). Thereby, the electron beam is incident on the entire bottom surface of the concave portion of the sample while being scanned. The electron beam incident on the bottom is reflected, and when the reflected electrons hit the side wall, secondary electrons are emitted at a predetermined emission angle according to the position. The emitted secondary electrons are incident on different detection elements according to the emission angle. And the detection signal amplified according to the gain set for each detection element is output.

  Next, the sum and difference of the detection elements are calculated (S14). Then, a signal in which the specific position of the side wall is emphasized (S15), a signal in which the bottom surface of the concave portion is emphasized (S16), and a signal in which the surface of the concave portion is emphasized (S17) are obtained. Based on such a signal, by constructing an electron microscope image of the concave portion, detailed information (fine shape and defect) on the side wall and bottom surface of the concave portion can be obtained.

(Electron Beam Device: Second Embodiment)
FIG. 13 is an electron beam apparatus according to the second embodiment, and is a schematic configuration diagram showing a cross section along the longitudinal direction of the electron beam column. In addition, the same number is attached | subjected to the structure similar to the electron beam apparatus of 1st embodiment, and the detailed description is abbreviate | omitted.
In the electron beam apparatus 10 of the first embodiment, since the secondary electron beam detector 56 cannot be disposed on the optical axis of the electron beam, secondary electrons emitted along the optical axis of the electron beam cannot be detected. For this reason, in order to make it possible to detect secondary electrons emitted along the optical axis of the electron beam, in the electron beam apparatus 80 of the second embodiment, a secondary electron beam detector 81 is provided outside the electron beam column 21. And a separator (beam splitter) 82 for separating the secondary electrons and guiding the secondary electrons toward the secondary electron beam detector 81 in a region including the optical axis of the electron beam.

The separator (beam splitter) 82 transmits an electron beam directed toward the wafer (sample) W and refracts secondary electrons emitted from the wafer W toward the secondary electron beam detector 81.
Similar to the secondary electron beam detector 56 shown in FIG. 3, the secondary electron beam detector 81 is formed by arranging a plurality of detection elements.

  With the electron beam apparatus 80 having such a configuration, secondary electrons emitted along the optical axis of the electron beam can be detected, and a blind spot does not occur in the observed image, and a high-definition electron microscope image of the concave portion is obtained. It becomes possible.

  DESCRIPTION OF SYMBOLS 10 ... Electron beam apparatus, 21 ... Electron beam column, 56 ... Secondary electron beam detector (detector), 71 ... Detection element, 82 ... Separator (beam splitter).

Claims (5)

An electron beam optical system that includes an electron beam optical system that irradiates an electron beam toward a minute recess formed in the sample, and a detection system that detects secondary electrons generated by reflected electrons of the electron beam;
The detection system includes a detector formed by arranging a plurality of detection elements,
In accordance with the formation position of the detection element that has detected the secondary electrons , a gain control unit that sets the gain by specifying the position in the recess where the secondary electrons are generated, and in the depth direction of the recess An electron beam apparatus comprising: an SEM image forming circuit that generates image information including a side wall along the side . An electron beam optical system that irradiates an electron beam onto the sample surface, and an electron beam optical element that includes a detection system that detects secondary electrons generated by reflected electrons of the electron beam. The detection system includes a plurality of detection elements. The sample observing method comprises: an array of detectors; and an electron beam apparatus that detects the secondary electrons by the detection elements that are different from each other according to the emission angle of the secondary electrons. And
An irradiation step of selectively irradiating the electron beam toward a fine recess formed in the sample;
Detecting the secondary electrons with the detector;
Identifying the position in the recess where the secondary electrons are generated according to the formation position of the detection element that has detected the secondary electrons;
Generating image information including a side wall along the depth direction of the recess;
A sample observation method comprising: Individually setting individual gains of the detection elements;
The sample observation method according to claim 2 , further comprising a step of adding signals detected by the individual detection elements to obtain a high-definition image of the side wall along the depth direction of the recess. It calculates the difference between each other signals detected by each of the detecting element, according to claim 2 or 3 sample observation method wherein, further comprising the step of obtaining a high-resolution image of a specific region of the recess. By irradiating the electron beam on the entire surface of the sample, claims 2 to 4 sample observation method according to any one of the preceding, wherein further comprising a step of pre-detecting the position of said recess in said sample.