JP3946041B2 - Surface cross-sectional shape or three-dimensional surface shape measuring device and scanning electron microscope - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface cross-sectional shape or three-dimensional surface shape measuring apparatus for more accurately measuring a shape formed on the surface of a sample to be measured. In particular, a surface cross-section provided with means capable of irradiating a sample with primary electrons in a scanning electron microscope and capturing well secondary electrons emitted from the irradiation point as a signal corresponding to the cross-sectional shape or three-dimensional surface shape of the surface. The present invention relates to a shape or three-dimensional surface shape measuring apparatus.
[0002]
[Prior art]
In a conventional scanning electron microscope (SEM: Scanning Electron Microscope) surface cross-sectional shape or three-dimensional surface shape measuring device, secondary electrons emitted from the surface of a sample (DUT) are taken into a secondary electron detector. Because of the influence of the surrounding electromagnetic field, there was a problem that more accurate shape measurement could not be performed. In addition, the secondary electrons emitted from the surface of the sample by the sample itself are blocked before being taken into the secondary electron detector, and the amount of secondary electrons to be received is much larger than when there is no wall surface. There are cases where the error is reduced and a large error occurs in the shape measurement.
[0003]
[Problems to be solved by the invention]
In a conventional cross-sectional shape or three-dimensional surface shape measuring device for a scanning electron microscope, the influence of the surrounding electromagnetic field is measured before the secondary electrons emitted from the sample surface are taken into the secondary electron detector. In order to receive, there was a difficulty that could not be captured more accurately. Along with this, there is a drawback that the measurement error of the cross-sectional shape or three-dimensional surface shape of the surface of the sample becomes large. In addition, the secondary electrons emitted from the surface of the sample by the sample itself are blocked before being taken into the secondary electron detector, and the amount of secondary electrons to be received is much larger than when there is no wall surface. May be less. In such a case, a large error occurs in the measurement result of the cross-sectional shape or three-dimensional surface shape of the sample surface.
On the other hand, with the progress of processing technology, the formation of wiring patterns and circuits is complicated, and three-dimensionally formed into a deep groove shape or uneven shape, and miniaturization of 0.2 μm or less is also progressing. Accordingly, there is a need for a surface cross-sectional shape or three-dimensional surface shape measuring apparatus capable of measuring the surface cross-sectional shape or three-dimensional surface shape more accurately.
Therefore, the problem to be solved by the present invention is a surface cross-sectional shape or three-dimensional surface shape measuring device for measuring the cross-sectional shape or three-dimensional surface shape of the surface formed on the surface of the sample to be measured with less error. Is to provide.
In addition, the cross-sectional or three-dimensional surface shape of the surface formed on the surface of the sample to be measured is measured with higher accuracy by receiving reflected electrons or secondary electrons, and the cross-sectional shape or three-dimensional surface shape of the surface is measured. An apparatus and a scanning electron microscope are provided.
[0004]
[Means for Solving the Problems]
A first solution will be described.
In order to solve the above problems, the surface of the sample is irradiated with incident electrons, and the shape of the sample to be measured is measured based on the emitted electrons (reflected electrons or secondary electrons) generated from the sample. In the surface shape measuring device,
A detector (in-lens type detector) for shape measurement that detects the emitted electrons that pass through the inside of the objective lens among the emitted electrons (reflected electrons or secondary electrons) generated from the sample A device for measuring a cross-sectional shape of a surface or a three-dimensional surface shape, which is provided in a predetermined manner.
According to the above-described invention, it is possible to realize a surface cross-sectional shape or three-dimensional surface shape measuring apparatus for measuring the cross-sectional shape or three-dimensional surface shape of the surface formed on the surface of the sample to be measured with less error.
[0005]
Next, a second solving means will be shown.
In order to solve the above problems, the surface of the sample is irradiated with incident electrons, and the shape of the sample to be measured is measured based on the emitted electrons (reflected electrons or secondary electrons) generated from the sample. In the surface shape measuring device,
An emission angle limited receiving means (for example, a detection electron limiting diaphragm) for detecting the emitted electrons passing through the inside of the objective lens among the emitted electrons (reflected electrons or secondary electrons) generated from the sample is provided in a predetermined manner. There is an apparatus for measuring a cross-sectional shape of a surface or a three-dimensional surface shape.
[0006]
Next, a third solving means will be shown.
In order to solve the above-described problem, in a surface cross-sectional shape or three-dimensional surface shape measuring apparatus that irradiates a sample surface with incident electrons e1 and measures the shape of a sample to be measured based on reflected electrons generated from the sample.
A surface having emission angle limited receiving means for receiving reflected electrons within a predetermined angle region and converting them into electric signals among the reflected electrons generated from the sample based on the incident electrons e1 irradiated on the sample. There is a cross-sectional shape or three-dimensional surface shape measuring device.
[0007]
Next, a fourth solving means will be shown.
In order to solve the above-described problem, in a surface cross-sectional shape or three-dimensional surface shape measuring apparatus that irradiates a sample surface with incident electrons e1 and measures the shape of a sample to be measured based on secondary electrons generated from the sample.
It comprises emission angle limited receiving means for receiving secondary electrons in a predetermined angle region from secondary electrons generated from the sample based on incident electrons e1 irradiated on the sample and converting them into electric signals. There is a device for measuring the cross-sectional shape or three-dimensional surface shape of a surface.
[0008]
Next, a fifth solving means will be shown. FIG. 4 shows the solving means according to the present invention.
In order to solve the above problems, the surface of the sample is irradiated with incident electrons e1 and the shape of the sample to be measured is measured based on the reflected electrons or secondary electrons generated from the sample. In the device
An emission angle limited receiving means for receiving, in a predetermined manner, reflected electrons or secondary electrons in a predetermined angle region among reflected electrons or secondary electrons generated from the sample based on incident electrons e1 irradiated on the sample and converting them into an electrical signal. There is a surface cross-sectional shape or three-dimensional surface shape measuring apparatus characterized by comprising:
[0009]
Next, sixth solving means will be described. FIG. 4 shows the solving means according to the present invention.
One aspect of the emission angle limited receiving means for detecting the secondary electrons is as follows.
An electrostatic objective lens 20 that adjusts the focal point of incident electrons e1 that irradiate the sample surface;
Secondary electrons are generated based on the incident electrons e1 irradiated on the sample, and the secondary electrons passing through the inside of the electrostatic objective lens 20 have a predetermined opening 52 formed at the center of the irradiation axis. A detection electronic limiting aperture 50 that allows only secondary electrons e3 in the region to pass through;
In-lens type secondary electron detection means for shape measurement that receives secondary electrons e3 that have passed through the detection electron limiting diaphragm 50 and converts them into electrical signals,
There is an apparatus for measuring a cross-sectional shape or a three-dimensional surface shape of the above-mentioned surface characterized by comprising the above.
[0010]
Next, a seventh solving means will be shown.
One aspect of the emission angle limited receiving means for detecting the secondary electrons is as follows.
An electrostatic objective lens 20 that adjusts the focal point of incident electrons e1 that irradiate the sample surface;
Secondary electrons are generated based on the incident electrons e1 irradiated on the sample, and the secondary electrons passing through the inside of the electrostatic objective lens 20 have a predetermined opening 52 formed at the center of the irradiation axis. A detection electronic limiting aperture 50 that allows only secondary electrons e3 in the region to pass through;
In-lens type first secondary electron detection means for shape measurement that receives secondary electrons e3 that have passed through the detection electron limiting diaphragm 50 and converts them into electrical signals;
Out-lens type second secondary electron detection means for receiving secondary electrons that pass outside the electrostatic objective lens 20 among the secondary electrons generated from the sample surface and converting them into electrical signals is provided. ,
There is an apparatus for measuring a cross-sectional shape or a three-dimensional surface shape of the above-mentioned surface characterized by comprising the above.
According to this, based on the secondary electron profile based on the in-lens type first secondary electron detection means for shape measurement and the secondary electron profile based on the second secondary electron detection means of the out lens type. The contour of the two-dimensional shape or the three-dimensional shape can be specified more accurately.
[0011]
Next, an eighth solving means will be shown. Here, FIG. 2 shows a solution means according to the present invention.
One aspect of the emission angle limited receiving means for detecting the reflected electrons is as follows.
An electrostatic objective lens 20 that adjusts the focal point of incident electrons e1 that irradiate the sample surface;
Reflected electrons are generated based on the incident electrons e1 irradiated on the sample. Among the reflected electrons passing through the inside of the electrostatic objective lens 20, a predetermined region is formed by a predetermined opening 52 formed at the center of the irradiation axis. A detection electronic limiting diaphragm 50 that allows only the reflected electrons E3 to pass;
A secondary electron conversion plate 40 that receives the reflected electrons E3 that have passed through the detection electron limiting diaphragm 50, converts them into secondary electrons corresponding thereto, and emits them;
In-lens type secondary electron detection means for shape measurement that receives secondary electrons from the secondary electron conversion plate 40, converts them into electrical signals and outputs them,
There is an apparatus for measuring a cross-sectional shape or a three-dimensional surface shape of the above-mentioned surface characterized by comprising the above.
[0012]
Next, ninth solving means will be described. FIG. 4 shows the solving means according to the present invention.
As an aspect of the secondary electron detection means, there are two secondary electron detectors 31 and 32 provided in a predetermined arrangement corresponding to the scanning axis direction of the sample. There is a cross-sectional shape or three-dimensional surface shape measuring device.
[0013]
Next, a tenth solution means will be shown. FIG. 5 shows the solving means according to the present invention.
One aspect of the secondary electron detection means includes two first secondary electron detectors 31 and 32 that are provided in a predetermined arrangement corresponding to one scanning axis direction (X-axis direction) of the sample. Then, two second secondary elements provided perpendicularly to the first secondary electron detectors 31 and 32 and corresponding to the other scanning axis direction (Y-axis direction) of the sample are provided. Comprising electron detectors 33, 34;
There is an apparatus for measuring a cross-sectional shape or a three-dimensional surface shape of the above-mentioned surface characterized by comprising the above.
[0014]
Next, eleventh solving means will be shown. FIG. 6 shows the solution means according to the present invention.
An energy filter 54 is provided on the front surface of the detection electron limiting diaphragm 50 that receives the secondary electrons. The energy filter 54 passes secondary electrons having a predetermined energy or higher and blocks secondary electrons having a predetermined energy or lower.
A deceleration voltage source 56 for supplying a predetermined negative deceleration voltage to the energy filter 54;
There is an apparatus for measuring a cross-sectional shape or a three-dimensional surface shape of the above-mentioned surface characterized by comprising the above.
[0015]
Next, a 12th solution means is shown. FIG. 7 shows the solution means according to the present invention.
A secondary electron extraction electrode 24 which is disposed close to the sample surface and extracts and accelerates secondary electrons generated based on incident electrons e1 irradiated on the sample and supplies the secondary electrons to the detection electron limiting diaphragm 50;
An extraction voltage source 26 for supplying a predetermined positive extraction voltage to the secondary electron extraction electrode 24;
There is an apparatus for measuring a cross-sectional shape or a three-dimensional surface shape of the above-mentioned surface characterized by comprising the above.
[0016]
Next, thirteenth solving means will be shown. FIG. 8 shows the solving means according to the present invention.
One aspect of the detection electronic restriction diaphragm 50 is a detection electronic restriction variable diaphragm 80 having a mechanical variable diaphragm mechanism that makes the size of the central opening hole variable. Alternatively, there is a three-dimensional surface shape measuring device.
[0017]
Next, fourteenth solving means will be shown.
Applying an electromagnetic objective lens instead of the electrostatic objective lens 20 described above,
An apparatus for measuring a cross-sectional shape or a three-dimensional surface shape of the surface, characterized in that a secondary electron detecting means is provided so as to correspond to an axial rotation amount of secondary electrons accompanying the electromagnetic objective lens. There is.
According to this, the amount of rotation of the secondary electrons in the axial direction associated with the electromagnetic objective lens is obtained in advance, and the secondary electron detectors 31 and 32 are arranged so as to correspond to this, thereby obtaining a two-dimensional shape. Alternatively, a three-dimensional shape can be measured practically.
[0018]
Next, the fifteenth solving means will be shown.
A scanning electron microscope comprising a configuration for measuring a cross-sectional shape or a three-dimensional surface shape of a sample surface with a small amount of error and a high accuracy by applying the above-described surface cross-sectional shape or three-dimensional surface shape measuring device. There is.
[0019]
In addition, the invention means of the present application may be combined with each element means in the above-described solution means as appropriate to form other practical means that can be used as desired. Moreover, although the code | symbol provided to each said element respond | corresponds to the code | symbol shown by embodiment etc. of this invention, it is not limited to this, The structural means to which the other equivalent which is practical is applied It is also good.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
An example of an embodiment to which the present invention is applied will be described below with reference to the drawings. Further, the scope of the claims is not limited by the description of the following embodiment, and further, the elements described in the embodiment are not necessarily essential to the solution means. Furthermore, the features / forms of the elements described in the embodiments are merely examples, and are not limited to only the features / form contents.
[0021]
The present invention will be described below with reference to FIGS.
First, the relationship between the cross-sectional shape of the surface of the sample shown in FIGS. 1A and 1B and the secondary electron emission angle α will be described. Here, it is assumed that the secondary electrons received by the secondary electron detector among the emitted secondary electrons generated by the incident electrons are emitted from the left and right within an angle range of α.
In the cross-sectional shape of the groove-shaped surface of FIG. 1A, secondary electrons emitted in the direction within the angle range of α emitted based on the incident electrons incident on the point A are directions within the angle range of α. Since there is nothing to obstruct, the secondary electron detector can detect everything.
[0022]
On the other hand, in the cross-sectional shape of the groove-shaped surface of FIG. 1B, the direction within the angular range of α emitted based on the incident electrons incident on the deeper B point where the slope inclination angle of the A point is the same. In the case of secondary electrons, the electron is emitted in the direction within the angle range of α, but is partially blocked by the wall surface portion of the sample itself. That is, the area m is blocked by the right slope wall. Furthermore, the area n is blocked by the left slope. Therefore, the emission angle range from the point B is about half. As a result, the amount of secondary electrons received by the secondary electron detector causes a detection error of a small amount of electrons, which is about a fraction of that of the point A. Along with this, a large error occurs in the measurement shape obtained by performing the calculation process for obtaining the cross-sectional shape of the surface of the sample. For this reason, it is not preferable for the purpose of accurate shape measurement.
[0023]
Therefore, the principle means of the present invention will be described. As shown in FIG. 1C, the secondary electrons received by the secondary electron detector are provided with emission angle limited receiving means that can receive only the emission angles in the acute angle emission angle β region. The release angle limited receiving means will be described later. If secondary electrons of only the acute emission angle β region can be received, the sample itself is not partially obstructed at any of the points of FIGS. 1D, 1E, and F where the inclination angle of the slope is equal. The same amount of secondary electrons can be received. As a result, an accurate measurement of the cross-sectional shape of the surface is possible without causing a large error in the obtained measurement shape.
Those in which shape measurement is performed by detecting reflected electrons instead of secondary electrons are similarly improved.
[0024]
The means of the present invention uses an in-lens type detector instead of an out-lens type detector as a secondary electron detector for shape measurement as the first emission angle limited receiving means. In other words, a plurality of secondary electron detectors arranged in the azimuth direction above the objective lens are used.
According to this, the entire acute angle emission angle α region shown in FIG. 1 is received by the out-lens type detector shown in FIG. 9B, but only the acute angle emission angle β region shown in FIG. Since electrons can be received by an in-lens type detector as shown in FIG. 9A, there is obtained an advantage that accurate cross-sectional shape measurement of the surface with few errors can be performed.
[0025]
Next, FIG. 2 is a principle structural diagram in the case of including a detection electron limiting diaphragm 50 that limits the angle range of detection electrons (detection target electrons) in the case of reflected electrons. This is the case for reflected electrons. Here, the detection electronic limit diaphragm 50 is a second emission angle limited receiving unit.
The detection electron limiting diaphragm 50 is a shielding plate having a circular opening 52 having a predetermined diameter centered on the irradiation axis for irradiating the incident electrons e1 and is passed from the sample through the objective lens (electrostatic objective lens) 20. Among the reflected electrons E2 reflected in the region of the wide angle range θ1 having a conical expanse, the reflection of the limited region within the limited angle range θ2 (corresponding to the combination of the right and left acute emission angle β regions). The size of the opening hole 52 through which the electron E3 passes is set. As a result, the reflected electrons E4 other than the limited angle range θ2 can be excluded. The reflected electrons E3 that have passed through the opening hole 52 are converted into secondary electrons by the secondary electron conversion plate 40 and supplied to the secondary electron detectors 31 and 32.
In addition, when the inclined surface stands vertically as shown in FIG. 1 (d), the portion near the side wall of the inclined surface and the bottom surface cannot be measured practically even if the reflected electrons in the acute emission angle β region are applied. In this case, as shown in FIG. 1 (e), the sample itself is tilted, and the tilt angle of the slope viewed from the detection system is tilted so as to correspond to the acute angle emission angle β (limited angle range θ2). In addition, the tilt angle of the sample is adjusted so that at least the center of the bottom surface is not shielded. Furthermore, when measuring the other slope, the same measurement may be performed after the sample is tilted to the opposite side.
Therefore, according to the above-described configuration example of the inventive principle of FIG. 2, the reflected electrons in only the acute emission angle β region shown in FIG. 1 are received by the secondary electron detectors 31 and 32 via the secondary electron conversion plate 40. The advantage that can be obtained.
[0026]
Next, FIG. 3 is a principle structural diagram in the case of including a detection electron limiting aperture 50 that limits the angle range of detection electrons (detection target electrons) in the case of secondary electrons. This is the case for secondary electrons. Here, the detection electronic limit diaphragm 50 is a third emission angle limited receiving unit.
The detection electron limiting diaphragm 50 in this case is the same as described above, and has the size of the opening hole 52 through which the secondary electrons e3 in the region within the limited angle range θ2 pass. As a result, secondary electrons e4 other than the limited angle range θ2 can be excluded.
Therefore, according to the configuration example of the principle of the invention shown in FIG. 3 described above, there is an advantage that secondary electrons only in the acute emission angle β region shown in FIG. 1 can be received.
[0027]
Next, FIG. 4 is a principle structural diagram according to the present invention of a scanning electron microscope having a detection electron limiting diaphragm.
This component includes a condenser lens 60, secondary electron detectors 31 and 32, a detection electron limiting diaphragm 50, a scan coil 70, an electrostatic objective lens 20, and a calculation unit 110. Here, the detection electronic limit diaphragm 50 is a fourth emission angle limited receiving unit. Here, since the scanning electron microscope is publicly known and well known in the art, other signals and components, and detailed description thereof, are omitted except for the main part according to the present application.
The condenser lens 60 condenses the electron beam in a predetermined manner.
The secondary electron detectors 31 and 32 are in-lens type secondary electron detectors for shape measurement that detect secondary electrons passing through the inside of the electrostatic objective lens 20, and are X-axis direction (lateral) Change in secondary electrons that change in the X-axis direction is detected. The secondary electron e3 that has passed through the detection electron limiting diaphragm 50 is received and an electric signal amplified in a predetermined manner is output, and is disposed at a position facing the electron beam axis.
The scan coil 70 is a deflection unit that controls the deflection of the incident electrons e1 incident on the sample in a desired direction based on control from the outside. For example, it is possible to scan in the X-axis direction and Y-axis direction of a horizontal straight line, or to scan in an arbitrary plane direction of the X-axis and Y-axis.
[0028]
As shown in FIG. 3, the detection electron limiting diaphragm 50 is a secondary electron e2 generated from the sample and passing through the electrostatic objective lens 20, and other than the secondary electrons that can pass through the aperture hole 52. Secondary electrons are excluded. The size of the opening hole 52 is set to a size of the opening diameter so as to obtain a desired acute angle emission angle β. This provides the advantage that the secondary electron detectors 31 and 32 can receive only the acute emission angle β region shown in FIG.
[0029]
The electrostatic objective lens 20 adjusts and controls the focus (focus) in the vertical direction (Z-axis direction) of the incident electrons e1 irradiated on the sample surface based on control from the outside. When there is a large recess as shown in FIG. 1, the focus of the incident electrons e1 to be irradiated can be controlled so that the focus is set at the target height position. If a magnetic field type objective lens is applied, the secondary electrons e2 cause a rotational movement while passing through the magnetic field type objective lens due to the magnetic field, so that the emission directionality of the secondary electrons is lost and the tilt angle information is lost. For this reason, it is not preferable for the purpose of accurate shape measurement.
By applying the electrostatic objective lens 20, the secondary electron detectors 31 and 32 are placed at the positions where the X-axis and Y-axis having a conical expanse are emitted in the plane direction. There is an advantage that the secondary electrons e3 in the corresponding specific emission direction can be received.
[0030]
The stage 100 is a moving mechanism that moves a sample by a desired amount in the horizontal direction of the XY axis and the vertical direction of the Z axis.
The calculation unit 110 controls the above elements to scan a desired section in the horizontal direction as desired, and obtains secondary electron signals obtained from the secondary electron detectors 31 and 32 in a relationship that is synchronously correlated with the scanning operation. In response to the (secondary electron profile), the concavo-convex shape of the scanning area is generated as two-dimensional or three-dimensional image information by a known surface cross-sectional shape calculating means or three-dimensional surface shape means.
[0031]
According to the above-described configuration example of FIG. 4, the objective lens uses the electrostatic objective lens 20 and includes the detection electronic limiting diaphragm 50, so that the acute angle emission angle β region shown in FIG. 1 is obtained. Can only receive secondary electrons. In addition, by applying the electrostatic objective lens 20, the secondary electron detectors 31 and 32 remain at the arrangement positions while maintaining the emission directivity in the plane direction of the X-axis and Y-axis having a conical extension. There is an advantage that the secondary electrons e3 in the corresponding specific emission direction can be received. This provides a great advantage that accurate two-dimensional and three-dimensional image information with little error can be generated.
[0032]
Next, FIG. 5 shows an arrangement of the two secondary electron detectors shown in FIG. 4 as viewed from the upper part of the lens barrel body when four secondary electron detectors 31, 32, 33, and 34 are arranged. FIG.
Each of the secondary electron detectors 31, 32, 33, and 34 is provided with an arrangement angle of 90 degrees with respect to the circumference of the barrel main body. This is suitable for shape measurement in a state where the sample is inclined as shown in FIG.
According to the configuration of FIG. 5 described above, secondary electrons e3 in the state of emission direction can be measured simultaneously in the plane direction of the X-axis and Y-axis, so that it is unnecessary to rotate the stage on which the sample is placed by 90 degrees. Therefore, the measurement error accompanying the stage positioning error can be eliminated. Therefore, in particular, as a result of being able to accurately measure an extremely fine concavo-convex shape, a great advantage is obtained that two-dimensional and three-dimensional image information can be generated more accurately.
[0033]
Next, FIG. 6 shows a configuration example in which an energy filter 54 for removing unnecessary low-energy secondary electrons and a deceleration voltage source 56 are additionally provided.
The energy filter 54 allows high energy secondary electrons having a certain energy or higher to pass through, and slows and repels low energy secondary electrons having a certain energy or lower to block the passage thereof. The structure is a fine mesh-like grid electrode, and is disposed in a plane over the entire region through which the secondary electrons e2 pass. A desired negative DC voltage is applied to this electrode by a deceleration voltage source 56.
The deceleration voltage source 56 is a negative DC variable power supply, and supplies a desired negative deceleration voltage to the energy filter 54 based on control from the outside. This voltage control prevents passage of low energy secondary electrons below the desired energy level.
[0034]
According to the configuration shown in FIG. 6, since a deceleration voltage is applied to the energy filter 54 and electrons below a certain energy are pulled back and cannot pass, unnecessary secondary electrons can be eliminated. Secondary electrons and other unnecessary noise-like secondary electrons can be effectively separated. Therefore, as a result of improving the signal-to-noise ratio of the received electrical signal, a great advantage can be obtained that two-dimensional and three-dimensional image information can be generated more accurately.
[0035]
Next, FIG. 7 shows a configuration example in which a secondary electron extraction electrode 24 and an extraction voltage source 26 for increasing the amount of secondary electrons emitted from the sample are additionally provided. The secondary electron extraction electrode 24 is an electrode for secondary electron extraction intended to improve the detection efficiency by increasing the amount of secondary electrons to be received, particularly at the bottom of a deep groove having a high aspect ratio. On the other hand, it is effective when a narrow receiving range with an acute emission angle β region is applied. The secondary electron extraction electrode 24 is disposed at a position immediately above the sample, and has a round opening hole 25 for allowing secondary electrons to pass therethrough. Thereby, secondary electrons at a low energy level can be extracted.
The extraction voltage source 26 is a positive DC variable power supply, and supplies a predetermined extraction voltage to the secondary electron extraction electrode 24 so as to satisfy the best detection condition based on control from the outside.
[0036]
According to the configuration of FIG. 7, the detection efficiency of secondary electrons from the groove bottom having a high aspect ratio can be increased. However, since the measurement accuracy is somewhat sacrificed, it is desirable to apply it to a groove having a high aspect ratio. As a result, even for a groove having a high aspect ratio, the SN ratio is improved, so that a great advantage that more accurate shape measurement information can be generated is obtained.
[0037]
Next, FIG. 8 is a structural diagram of the principle of the present invention of a scanning electron microscope provided with a detection electron limiting variable stop 80. Here, the detection electronic limit variable aperture 80 is the fifth emission angle limit receiving means.
The detection electronic limit variable aperture 80 has a variable aperture mechanism that mechanically varies the aperture diameter based on control from the outside in the size of the variable aperture hole 82 through which the secondary electrons e3 pass. The aperture of the variable aperture can be firstly made up to a large aperture size which is almost equal to the aperture without an aperture when the aperture size is almost fully open, and secondly, the smallest aperture size which can be practically controlled. At this time, the diaphragm mechanism is configured such that the center of the incident axis coincides with the center of the opening hole.
The shape of the variable opening hole 82 is preferably circular, but need not be circular. For example, when it corresponds to the two secondary electron detectors 31 and 32, it may be a parallel slit-like (see FIG. 8A) opening hole (opening width). Further, in the case of corresponding to the four secondary electron detectors 31 to 34, an opening hole having a quadrangular shape (see FIG. 8B) may be used.
By the way, the insertion of the detection electron limiting variable diaphragm 80 can make the measurable inclination angle range only the acute emission angle β region, but on the other hand cuts a part of the signal received by the secondary electron detector. As a result, the signal-to-noise ratio becomes worse. For this reason, it is an excellent advantage that the variable aperture hole 82 can be adjusted to the diaphragm condition corresponding to the situation of the measurement object.
[0038]
According to the configuration shown in FIG. 8, first, the optimum condition is considered in consideration of the SN ratio between the electrical signal to be detected output from the secondary electron detector and the noise component generated from the secondary electron detector or the like. It is possible to adjust and control the aperture diameter. Furthermore, since the secondary electron detection signal output from the secondary electron detector can be set to the optimum signal-to-noise ratio condition, a great advantage can be obtained that the most accurate shape measurement information can be generated. Furthermore, when it is not necessary to generate accurate shape measurement information, there is an advantage that measurement can be performed in a fully opened state so as to satisfy the same conditions as in the prior art.
[0039]
The technical idea of the present invention is not limited to the specific configuration example and the structural example of the above-described embodiment. Furthermore, based on the technical idea of the present invention, the above-described embodiment may be modified as appropriate and applied widely.
For example, in the above-described embodiment, the description has been given with a specific example in the case of a two-dimensional or three-dimensional surface shape measuring device that receives a secondary electron from a sample and performs accurate shape measurement, but instead of a secondary electron. The same effect as described above is exhibited when receiving reflected electrons. Therefore, a two-dimensional or three-dimensional surface shape measuring apparatus capable of measuring an accurate shape by applying reflected electrons from a sample may be used.
[0040]
Further, in the secondary electron extraction electrode 24 of FIG. 7 described above, a function as an objective lens is maintained for the lowermost electrode of the electrostatic objective lens 20 in place of the secondary electron extraction electrode 24 if desired. However, it may function so as to also have the function of the secondary electron extraction electrode 24. In this case, it can be realized at a lower cost with the combined use.
[0041]
In addition, the above-described detection electron limiting diaphragm, which is an emission angle limited receiving means, arrangement of four secondary electron detectors, energy filter and deceleration voltage source, secondary electron extraction electrode and extraction voltage source, detection electron You may implement | achieve a desired scanning electron microscope by combining suitably each element element of the discharge angle limited receiving means of a limit variable aperture. Thereby, an optimal scanning electron microscope corresponding to the measurement application can be realized.
[0042]
In the above description, the electrostatic objective lens 20 is used. However, an electromagnetic objective lens may be used instead of the electrostatic objective lens 20 if desired. However, since the secondary electrons are rotated in the axial direction along with the electromagnetic objective lens, the amount of rotation is obtained in advance by other measuring means, and the secondary electron detector 31 corresponds to the amount of rotation. , 32 may be configured to determine the arrangement position on the 32 side. In this case, it is inferior to the electrostatic objective lens 20 due to the arrangement of the secondary electron detectors 31 and 32 corresponding to the known amount of secondary electron rotation in the axial direction accompanying the electromagnetic objective lens. The advantage that it can be measured practically is obtained.
[0043]
Moreover, you may comprise so that the movement mechanism which can move the detection electronic restriction aperture 50 of FIG. 4 mentioned above is provided. In this case, there can be obtained an advantage that both the normal measurement accuracy in the fully opened state, which is the detection condition similar to the conventional detection condition corresponding to the measurement situation, and the high measurement accuracy of the present invention can be applied.
[0044]
【The invention's effect】
The present invention has the following effects in view of the above description.
According to the configuration example of the inventive principle of FIG. 2 described above, there is an advantage that the secondary electron detectors 31 and 32 can receive the reflected electrons only in the acute emission angle β region shown in FIG.
According to the configuration example of the principle of the invention shown in FIG. 3 described above, there is an advantage that secondary electrons in only the acute emission angle β region shown in FIG. 1 can be received.
[0045]
According to the above-described configuration example of FIG. 4, the objective lens uses the electrostatic objective lens 20 and includes the detection electronic limiting diaphragm 50, so that the acute angle emission angle β region shown in FIG. 1 is obtained. Can only receive secondary electrons. In addition, by applying the electrostatic objective lens 20, the secondary electron detectors 31 and 32 remain at the arrangement positions while maintaining the emission directivity in the plane direction of the X-axis and Y-axis having a conical extension. There is an advantage that the secondary electrons e3 in the corresponding specific emission direction can be received. As a result, it is possible to obtain a measurement signal that can clearly identify the two-dimensional position of the sample irradiation point. As a result, it is possible to obtain a great advantage that accurate two-dimensional and three-dimensional image information with less errors can be generated. .
[0046]
According to the configuration of FIG. 5 described above, the secondary electrons e3 having the emission directionality can be simultaneously measured in the plane direction of the X axis and the Y axis, and as a result, accurate two-dimensional and three-dimensional image information with less errors. A great advantage is obtained.
[0047]
According to the configuration of FIG. 6 described above, a deceleration voltage is applied to the energy filter 54, and electrons below a certain energy cannot be pulled back and passed. As a result, useless secondary electrons can be eliminated. Secondary electrons and other unnecessary noise-like secondary electrons can be effectively separated. Therefore, the signal-to-noise ratio of the received electrical signal can be improved, resulting in a great advantage that more accurate shape measurement information can be generated.
[0048]
According to the configuration of FIG. 7 described above, it is possible to increase the detection efficiency of secondary electrons particularly from the groove bottom having a high aspect ratio. However, since the measurement accuracy is somewhat sacrificed, it is desirable to apply it to a groove having a high aspect ratio. As a result, even for a groove having a high aspect ratio, the SN ratio is improved, so that a great advantage that more accurate shape measurement information can be generated is obtained.
[0049]
According to the configuration of FIG. 8 described above, first, a ratio (SN ratio) between a target electrical signal received and output by the secondary electron detector and a noise component such as white noise generated from the secondary electron detector itself. Therefore, it is possible to adjust and control the aperture state under the optimum conditions. Therefore, since the secondary electron detection signal output from the secondary electron detector can be set to the optimum S / N ratio condition, a great advantage that the most accurate shape measurement information can be generated is obtained. On the other hand, when it is not necessary to generate accurate shape measurement information, there is an advantage that measurement can be performed in a fully opened state as in the prior art.
Therefore, the technical effect of the present invention is great, and the industrial economic effect is also great.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a relationship between a cross-sectional shape of a surface of a sample and an emission angle α of secondary electrons (or reflected electrons).
FIG. 2 is a principle structural diagram in the case where a detection electron limiting diaphragm for limiting the angle range of detection electrons (detection target electrons) in the case of reflected electrons is provided according to the present invention.
FIG. 3 is a structural diagram of the principle when a detection electron limiting diaphragm for limiting the angle range of detection electrons (detection target electrons) in the case of secondary electrons is provided according to the present invention.
FIG. 4 is a structural diagram of the principle of the present invention of a scanning electron microscope having a detection electron limiting diaphragm according to the present invention.
FIG. 5 is an arrangement view of the present invention as seen from the upper part of the lens barrel body when four secondary electron detectors are arranged.
FIG. 6 is a configuration example additionally including an energy filter for removing unnecessary low-energy secondary electrons and a deceleration voltage source according to the present invention.
FIG. 7 is a structural example of the present invention additionally including a secondary electron extraction electrode and an extraction voltage source for increasing the amount of secondary electrons emitted from a sample.
FIG. 8 is a principle structural diagram according to the present invention of a scanning electron microscope having a detection electron limiting variable aperture according to the present invention.
FIG. 9 is a principle configuration diagram for detecting secondary electrons with an in-lens detector and a principle structure diagram for detecting secondary electrons with an out-lens detector according to the present invention.
[Explanation of symbols]
20 Electrostatic objective lens (objective lens)
24 Secondary electron extraction electrode
26 Extraction voltage source
31, 32, 33, 34 Secondary electron detector
50 detection electronic limit aperture
54 Energy Filter
56 Deceleration voltage source
60 condenser lens
70 scan coil
80 Detection electronic limit variable aperture
110 Calculation unit

Claims (10)

In the surface cross-sectional shape or three-dimensional surface shape measuring device that irradiates the sample surface with incident electrons and measures the shape of the sample to be measured based on the emitted electrons generated from the sample.
An electrostatic objective lens that adjusts the focal point of incident electrons irradiated on the sample surface;
Secondary electrons are generated based on the incident electrons irradiated on the sample. Among the secondary electrons that pass through the inside of the electrostatic objective lens, a predetermined aperture is formed at the center of the irradiation axis, and a secondary region of a predetermined region is formed. A detection electronic restriction aperture that allows only the secondary electrons to pass through;
In-lens type secondary electron detection means for shape measurement that receives secondary electrons that have passed through the detection electron limiting diaphragm and converts them into electrical signals;
An apparatus for measuring a cross-sectional shape of a surface or a three-dimensional surface shape, comprising: In the surface cross-sectional shape or three-dimensional surface shape measuring device that irradiates the sample surface with incident electrons and measures the shape of the sample to be measured based on the emitted electrons generated from the sample.
An electrostatic objective lens that adjusts the focal point of incident electrons irradiated on the sample surface;
Secondary electrons are generated based on the incident electrons irradiated on the sample. Among the secondary electrons that pass through the inside of the electrostatic objective lens, a predetermined aperture is formed at the center of the irradiation axis, and a secondary region of a predetermined region is formed. A detection electronic restriction aperture that allows only the secondary electrons to pass through;
In-lens type first secondary electron detection means for shape measurement that receives secondary electrons that have passed through the detection electron limiting diaphragm and converts them into electrical signals;
Out-lens type second secondary electron detection means that receives secondary electrons that pass outside the electrostatic objective lens and converts them into electrical signals among the secondary electrons generated from the sample surface;
An apparatus for measuring a cross-sectional shape of a surface or a three-dimensional surface shape, comprising: In the surface cross-sectional shape or three-dimensional surface shape measuring device that irradiates the sample surface with incident electrons and measures the shape of the sample to be measured based on the emitted electrons generated from the sample.
An electrostatic objective lens that adjusts the focal point of incident electrons irradiated on the sample surface;
Reflected electrons are generated based on the incident electrons irradiated on the sample. Among the reflected electrons passing through the inside of the electrostatic objective lens, only the reflected electrons in a predetermined region are formed at a predetermined aperture formed in the center of the irradiation axis. A detection electronic restriction aperture that passes through,
A secondary electron conversion plate that receives the reflected electrons that have passed through the detection electron limiting diaphragm, converts them into secondary electrons corresponding thereto, and emits them;
In-lens type secondary electron detection means for shape measurement that receives secondary electrons from the secondary electron conversion plate, converts them into electrical signals and outputs them, and
An apparatus for measuring a cross-sectional shape of a surface or a three-dimensional surface shape, comprising:   4. The surface of the surface according to claim 1, wherein the secondary electron detection means is two secondary electron detectors provided in a predetermined arrangement corresponding to a scanning axis direction of the sample. Cross-sectional shape or three-dimensional surface shape measuring device. The secondary electron detection means includes two first secondary electron detectors provided in a predetermined arrangement corresponding to one scanning axis direction (X-axis direction) of the sample,
Two second secondary electron detectors provided perpendicularly to the first secondary electron detector and provided in a predetermined manner corresponding to the other scanning axis direction (Y-axis direction) of the sample;
The apparatus for measuring a cross-sectional shape of a surface or a three-dimensional surface shape according to claim 1, comprising: An energy filter that passes secondary electrons of a predetermined energy or higher and blocks secondary electrons of a predetermined energy or lower on the front surface of the detection electron limiting diaphragm that receives secondary electrons;
The apparatus for measuring a sectional shape of a surface or a three-dimensional surface shape according to claim 1, further comprising: a deceleration voltage source that supplies a predetermined negative deceleration voltage to the energy filter. A secondary electron extraction electrode that is arranged close to the sample surface, extracts secondary electrons generated based on incident electrons irradiated on the sample, and supplies the secondary electrons to the detection electron limiting aperture;
An extraction voltage source for supplying a predetermined positive extraction voltage to the secondary electron extraction electrode;
The apparatus for measuring a cross-sectional shape of a surface or a three-dimensional surface shape according to claim 1, comprising:   The cross section of the surface according to claim 1, wherein the detection electronic restriction diaphragm is a detection electronic restriction variable diaphragm provided with a mechanical variable diaphragm mechanism that makes a size of a central opening hole variable. Shape or three-dimensional surface shape measuring device. Applying an electromagnetic objective lens instead of an electrostatic objective lens,
The cross-sectional shape of the surface according to claim 1, further comprising a secondary electron detection unit arranged so as to correspond to an axial rotation amount of secondary electrons accompanying the electromagnetic objective lens. Or a three-dimensional surface shape measuring device.   A configuration for measuring the cross-sectional shape or three-dimensional surface shape of the sample surface with high accuracy by applying the cross-sectional shape or three-dimensional surface shape measuring device of the surface according to claim 1 to 9 is provided. Scanning electron microscope.

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