JP2003157790A - Micro ruggedness value measurement device and scanning electron microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a micro ruggedness value measurement device which can measure depth H or the like of a concave part in case of a large aspect ratio. SOLUTION: The micro ruggedness value measurement device for measuring depth or height of sample by scanning its surface is provided with an in-lens reflective electron detecting means for shape measurement which receives only reflected electrons within a given angle region from those passing inside an object lens based on incident electrons irradiating the sample and converts them into electric signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine concavo-convex amount measuring device for measuring the depth and height amount (height and depth) of fine concavo-convex formed on the surface of a sample to be measured, and a scanning electron. Regarding the microscope. In particular, the present invention relates to a fine unevenness amount measuring device for irradiating a sample with a primary electron in a scanning electron microscope and measuring the fine unevenness amount of the sample surface from the reflected electrons emitted from this irradiation point.

[0002]

2. Description of the Related Art FIG. 1 is a principle structural diagram of a scanning electron microscope (SEM) based on the application of backscattered electrons. The main constituent elements irradiate a desired position with a condenser lens 60 that collects an electron beam, backscattered electron detectors (BSE detectors) 31 and 32 that receive backscattered electrons, and incident electrons e1 that are incident on a sample. For this purpose, the scan coil 70 for deflection control, the objective lens 20 for focusing and controlling the focal position of the incident electron e1 irradiating the sample surface in the Z-axis direction, the sample in the XY-axis horizontal direction and the Z-axis vertical direction. And a stage 100 that moves in the direction. Here, since the scanning electron microscope is publicly known and well known in the art, other signals and components, and detailed description thereof will be omitted except for the main part of the present application.

FIG. 2 is an explanatory view of the principle of measuring the height H of the convex shape of the sample by a predetermined scan. Here, it is assumed that the generated reflected electrons have high energy and travel straight in all directions. Further, the sample is assumed to be a right angle convex edge having a height H as shown in FIGS. FIG. 2C is a relationship diagram showing a transition of the electric signal level received by the backscattered electron detector 32 when the irradiation point is moved in the A, B, and C directions by scanning the incident electron e1. First, in the state of the irradiation point A in FIG. 2A, the electric signal level received is the maximum level, and starts decreasing from here. In the space between the backscattered electrons of the sample and the receiving surface of the backscattered electron detector 32, a shadow of the backscattered electrons is generated by being disturbed by the convex portion of the sample. That is, the portion of the shielded reflected electron e4 increases. Here, it is assumed that the backscattered electron detector 32 has an arrangement condition in which the backscattered electron detector 32 can receive backscattered electrons e3 in the angle range of θ1 to θ2. At this time, the angles θ1 and θ2 are known and constant angles. By scanning from the irradiation point A to the right, the received electric signal level decreases in the section of the singular points A1 to B1 shown in FIG. Next, FIG. 2B shows that the reception amount becomes zero in the state of the irradiation point B. At this time, the received electric signal level is the singular point B shown in FIG.
As shown in 1, the level is almost zero. After that, the scanning section up to the irradiation point C is at almost zero level. Immediately after that, since the incident electrons e1 are irradiated on the upper surface of the convex portion,
As shown by the singular point D1 in (c), the electric signal level returns to the original maximum level.

The height H of the convex portion is obtained based on the electric signal data (reflected electron signal profile) obtained by the above-mentioned scanning. That is, first, the singular points B1 and D1 are specified,
From this, the true shadow length Lf of both sections is obtained. From this true shadow length Lf and the known angle θ2, the height H of the convex portion
Can be calculated as H = Lf × tan θ2. Further, the height H of the convex portion can be calculated from the penumbra shadow length Lh in the section of the singular points A1 and D1 and the known angle θ1 as H = Lh × tan θ1.

Next, FIG. 3 is a scanning explanatory view for measuring the depth H of the concave groove of the sample by the scanning of the scanning coil. First, FIG. 3A shows a case where the aspect ratio H / W of the groove width W and the groove depth H is small, that is, the groove width W is wide. As a result of measurement performed in the same manner as in FIG. 2 described above, FIG.
The electric signal data shown in can be acquired. According to this, since the singular point B1 and the singular point D1 are obtained, the depth H of the concave portion can be calculated from this as H = Lf × tan θ2 without any trouble. Next, FIG. 3B shows the case where the aspect ratio H / W of the groove width W and the groove depth H is large.
As a result of measurement in the same manner as in FIG. 2 described above, the electric signal data shown in FIG. 3D can be acquired. In this case, backscattered electrons cannot be received at all during the scanning section in the groove. This poor reception can be understood from the reduction or lack of the scanning distance scanned from the singular point A1 to the section B1. As a result, the singular point B1 is not a valid singular point. Therefore, there arises a problem that the depth H of the concave portion cannot be obtained when the aspect ratio is large. The reception area range W of the backscattered electron detector 32
It is possible to increase θ2 by widening D, but this is not preferable because the resolution is deteriorated.

[0006]

As described above, when the aspect ratio is large, the depth H of the concave portion cannot be obtained by a conventional fine unevenness measuring device such as a scanning electron microscope. On the other hand, it is difficult to arrange the backscattered electron detectors 31 and 32 in the center because of the objective lens 20 disposed in the center. Therefore, the problem to be solved by the present invention is to provide a fine unevenness amount measuring apparatus capable of measuring the depth H and the like of the concave portion when the aspect ratio is large. Another object of the present invention is to provide a scanning electron microscope equipped with a fine unevenness amount measuring device capable of measuring the depth H of the recessed portion when the aspect ratio is large.

[0007]

A first solution will be described.
In order to solve the above-mentioned problem, the surface of the object to be observed (sample) is scanned with a predetermined known distance section by an electron beam to identify the top and bottom of the sample, and the depth or height of the sample is determined based on this. In the fine unevenness amount measuring device for measuring the unevenness amount, the reflected electrons within the predetermined angle region among the reflected electrons passing through the inside of the objective lens among the reflected electrons due to the reflection of the incident electrons e1 irradiated on the sample. In-lens type backscattered electron detecting means for shape measurement (for example, secondary electron conversion plate 40 and secondary electron detector 41,
42), which is capable of measuring an uneven portion having a large aspect ratio, and is a fine unevenness amount measuring device characterized by the above. According to the above-mentioned invention, it is possible to realize a fine unevenness amount measuring device capable of measuring the depth H of the concave portion, the height of the convex portion, and the like when the aspect ratio is large.

Next, a second solving means will be shown. In order to solve the above problems, the top and bottom of the sample are specified from the reflected electron signal profile obtained by scanning the surface of the observation target (sample) with a predetermined known distance section by an electron beam, and based on this, In the fine unevenness amount measuring device for measuring the unevenness amount which is the depth or height of the sample, in the reflected electrons passing through the inside of the objective lens among the reflected electrons due to the reflection of the incident electron e1 irradiated on the sample, Reflection electron opening angle limiting diaphragm 5 that allows only the reflection electrons within a predetermined angle region to pass therethrough
0, and includes a shape measuring in-lens type backscattered electron detection unit that receives backscattered electrons e5 that have passed through the backscattered electron opening angle limiting diaphragm 50 and converts the backscattered electrons e5 into an electric signal, and includes the above. There is a fine unevenness amount measuring device.

Next, a third solving means will be shown. The fourth here
The figure shows the solution according to the invention. In order to solve the above problems, the top and bottom of the sample are specified from the reflected electron signal profile obtained by scanning the surface of the observation target (sample) with a predetermined known distance section by an electron beam, and based on this, In the fine unevenness amount measuring device for measuring the unevenness amount which is the depth or height of the sample, in the reflected electrons passing through the inside of the objective lens among the reflected electrons due to the reflection of the incident electron e1 irradiated on the sample, Reflection electron opening angle limiting diaphragm 5 that allows only the reflection electrons within a predetermined angle region to pass therethrough
The in-lens type backscattered electron detection means for detecting the uneven portion having a large aspect ratio, which has the number 0 and receives the backscattered electrons e5 that have passed through the backscattered electron opening angle limiting diaphragm 50 and converts it into an electric signal. And the incident electron e1
Out-lens type backscattered electron detector 31, which is in charge of detecting backscattered electrons in a predetermined angle region under the objective lens among the backscattered electrons reflected from the sample irradiated with There is a fine concavo-convex amount measuring device comprising 32 and the above.

Next, a fourth solving means will be shown. One mode of the above-mentioned backscattered electron detection means includes a secondary electron conversion plate 40 that receives backscattered electrons e5 in a predetermined angle region, converts the backscattered electrons e5 into corresponding secondary electrons e6, and emits them. There is a secondary electron detecting means for receiving and converting the output into an electric signal and outputting the electric signal, and by providing the above, it is possible to measure an uneven portion having a large aspect ratio. .

Next, a fifth solving means will be shown. The fourth here
The figure shows the solution according to the invention. As one mode of the above-mentioned secondary electron detecting means, two secondary electron detectors 41 arranged and provided in a predetermined manner corresponding to the scanning axis direction of the sample,
42 is the above-mentioned fine unevenness amount measuring device.

Next, a sixth solving means will be shown. One mode of the secondary electron detecting means described above includes two first secondary electron detectors 41 and 42 which are provided in a predetermined manner in correspondence with one scanning axis direction (X axis direction) of the sample. Then, two second secondary devices which are orthogonally arranged to the first secondary electron detectors 41 and 42 and are arranged in a predetermined manner corresponding to the other scanning axis direction (Y-axis direction) of the sample. There is the above-mentioned fine unevenness amount measuring device including an electron detector and the above.

Next, a seventh means for solving the problems will be described. 6th here
The figure shows the solution according to the invention. Behind the objective lens, the reflected electrons with a certain energy or more are passed,
An energy filter 54 for blocking passage of other electrons having a certain energy or less (for example, secondary electrons) is provided, a deceleration voltage source 56 for supplying a predetermined negative deceleration voltage to the energy filter 54 is provided, and the above is provided. There is the above-mentioned fine unevenness amount measuring device characterized by the above.

Next, the eighth solving means will be described. A reference chip having a known depth Ds or a known height Hs is applied as a sample, the reflected electron signal profile of the known depth Ds or the known height Hs is acquired by the reflected electron detection means, and the calculated depth calculated from this is obtained. Dx or calculated height Hx,
From the difference between the known depth Ds or the known height Hs, a correction value (for example, the height calculation coefficient tan θ2) for correcting the measurement system is obtained and stored, and stored in the subsequent measurement of the unknown sample. There is the above-described fine unevenness amount measuring device characterized in that the measurement correction factor and the change factor with time of the measurement system are significantly reduced by performing the calculation correction processing based on the correction value.

Next, a ninth solving means will be described. As one mode of the above-described backscattered electron opening angle limiting diaphragm 50, the aperture 5 for the backscattered electrons e5 passing through the backscattered electron opening angle limiting diaphragm 50 is provided.
There is the above-mentioned fine unevenness amount measuring device characterized by comprising a variable diaphragm mechanism that can change the size of 2 or a variable diaphragm mechanism that can switch to a plurality of types of aperture diameters.

Next, the tenth solving means will be described. Here, FIGS. 9 and 10 show a solving means according to the present invention. Secondary electron detector for detecting secondary electrons emitted from the sample instead of backscattered electrons reflected from the sample to identify the singularity of the convex edge of the measurement site of the sample to obtain a secondary electron signal profile (For example, the in-lens type secondary electron detectors 43 and 44 shown in FIG. 9 or the out-lens type secondary electron detectors 45 and 46 shown in FIG.
And secondary electron detectors 43, 44 to which both of FIG.
45, 46) is provided.

Next, the eleventh solving means will be shown. Here, FIG. 8 shows a solving means according to the present invention. As one aspect when the measurement site of the sample is a gentle slope where shadows of backscattered electrons do not occur, sample inclination is performed by inclining the angle of the sample on the stage to a predetermined angle so that a shadow is produced at the measurement site. There is the above-mentioned fine unevenness amount measuring device characterized by comprising a mechanism.

Next, a twelfth solving means will be shown. By applying the above-mentioned fine unevenness amount measuring device, S with a high aspect ratio of the sample
There is a scanning electron microscope having a configuration for measuring an EM image.

If desired, the means of the present invention may be combined with the respective element means of the above-mentioned solving means as appropriate to form other practical means. Further, although the reference numerals given to the above respective elements correspond to the reference numerals shown in the embodiments of the present invention and the like, the present invention is not limited to this, and constituent means to which other practical equivalents are applied. Also good.

[0020]

BEST MODE FOR CARRYING OUT 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 content of the following embodiments, and further, the elements, connection relationships, and the like described in the embodiments are not necessarily essential to the solving means. Furthermore, the forms / forms of the elements, connection relationships, etc. described in the embodiments are merely examples, and the form / form contents are not limited only.

The present invention will be described below with reference to FIGS. The elements corresponding to those of the conventional configuration are designated by the same reference numerals, and the description of the overlapping portions will be omitted.

In FIG. 4, only the reflected electrons reflected at a narrow angle are converted into secondary electrons in the state of being separated in the left-right direction, and the secondary electrons are detected by the secondary electron detector while being separated in the left-right direction. It is a principle structure figure of in-lens type backscattered electron detection for shape measurement. The essential components include an objective lens 20, a backscattered electron opening angle limiting diaphragm 50, a secondary electron conversion plate 40, and secondary electron detectors 41 and 42.

The backscattered electron opening angle limiting diaphragm 50 is a diaphragm that allows only the backscattered electrons in a predetermined narrow angle range to pass, and enables the depth H of a groove having a high aspect ratio to be measured. That is, the reflected electrons e in a wide range around the irradiation point of the incident electrons e1
2, the secondary electron conversion plate 40 is allowed to pass only the reflected electrons e5 in the region of the narrow angle passage angle θ4 corresponding to the opening hole 52.
Supply to. According to this, the narrow-angle passing angle θ4 can be set to a narrow angle of, for example, 2 degrees to 5 degrees. Therefore, as a result that only the reflected electrons e5 in this narrow-angle region can be detected, a great advantage that the depth H of the groove having a high aspect ratio can be measured is obtained.

FIG. 5 shows the case of the conventional out-lens type backscattered electron detector, the case of the in-lens type backscattered electron detector for shape measurement of the present invention, and the backscattered electron opening angle limiting diaphragm 50 of the present invention.
Of in-lens type backscattered electron detector for shape measurement applying
It is a relative explanatory view showing the maximum measurable aspect ratio in one form. Here, the width d of the groove is the penumbra shadow length when the depth of the sample in the case of the out-lens backscattered electron detector is h1, and the depth of the sample in the case of the in-lens backscattered electron detector for shape measurement. Is the half shadow shadow length when h2 is the half shadow shadow length when the sample depth is h3 in the case of the in-lens type backscattered electron detector for shape measurement to which the backscattered electron aperture angle limiting diaphragm is applied. In the case of the conventional out-lens type backscattered electron detector for shape measurement, as shown in FIG. 5A,
Since the depth of the sample can be measured up to h1, the aspect ratio R1 is R1 = h1 / d. Next, in the case of the in-lens type backscattered electron detector for shape measurement which detects backscattered electrons in two or more directions of the present invention, as shown in FIG. 5B, the depth of the sample can be measured up to h2. Therefore, the aspect ratio R2 is R2 = h2 / d. Next, in the case of the in-lens type backscattered electron detector for shape measurement to which the backscattered electron aperture angle limiting diaphragm 50 of the present invention is applied, as shown in FIG. 5C, the depth of the sample can be measured up to h3. And the aspect ratio R3 is R3 = h3 /
d. Therefore, from the comparison of these FIG. 5, when the backscattered electron opening angle limiting diaphragm 50 is provided, it is possible to measure even a deep groove having a remarkably high aspect ratio. At this time, the diameter of the opening hole 52 can be formed as desired. In practical use, the S of the electrical signal to be detected output from the secondary electron detector and the noise component generated from the secondary electron detector, etc.
It is desirable to set the aperture diameter of the optimum condition in consideration of the N ratio.

Returning to FIG. 4, the secondary electron conversion plate 40 is provided with a hole in the central axis portion for passing the incident electron e1 from the upper side to the sample side, and receives the reflected electron e5 from the lower side,
The secondary electrons e6 corresponding to this are emitted and supplied to the left and right secondary electron detectors 41 and 42.

The secondary electron detectors 41 and 42 detect changes in secondary electrons which change in the X-axis direction (horizontal direction) by scanning in the X-axis direction (lateral direction). The secondary electron e is provided at a position on the X axis.
Upon receiving 6, the electric signal amplified to a predetermined level is output.

According to the invention configuration example of the in-lens type backscattered electron detector for shape measurement to which the backscattered electron opening angle limiting diaphragm of FIG. 4 described above is applied, the backscattered electron e2 from the sample is mainly the incident electron e1. By adopting a configuration in which only backscattered electrons within a predetermined narrow angle range are detected, it is possible to obtain a great advantage that a deep groove or edge having a remarkably high aspect ratio can be satisfactorily measured. Needless to say, it becomes possible to satisfactorily measure even an uneven portion such as a deep hole having a high aspect ratio.

Next, FIG. 6 shows an energy filter 54 and a deceleration voltage source 56 for removing unnecessary low energy secondary electrons.
This is a configuration example in which and are additionally provided. The energy filter 54 allows high-energy reflected electrons of a certain energy or more to pass therethrough, and unnecessary secondary electrons of a certain energy or less decelerate and repel them to block passage. The structure is a fine mesh grid electrode, and is arranged in a plane over the entire region through which the reflected electrons e5 pass. A desired negative DC voltage is applied to this electrode by the 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 under the control of the outside. By making this voltage control desired, there is an advantage that the reflected electrons suitable for reception and the secondary electrons which are other noise elements can be effectively separated.

According to the invention configuration example of the in-lens type backscattered electron detector for shape measurement provided with the energy filter of FIG. 6, a deceleration voltage is applied to the energy filter 54, and secondary electrons having a certain energy or less can be pulled back and passed. Disappear. Therefore, by controlling the deceleration voltage to a desired condition, it is possible to effectively separate the reflected electrons suitable for reception from the other electrons that are noise factors. Therefore, as a result of improving the SN ratio of the received electric signal, there is an advantage that the depth H of the groove having a high aspect ratio of the sample with higher measurement accuracy can be measured.

The technical idea of the present invention is not limited to the specific configuration examples and connection mode examples of the above-described embodiment. Furthermore, based on the technical idea of the present invention, the above-described embodiments may be appropriately modified and widely applied. For example, in the above-described embodiment, the depth H of the groove is used as the measurement target of the sample, but as shown in FIG. 7A, the height of the convex portion in the case where a plurality of convex portions of the sample are continuous is similar to the above. Can be measured. Further, as shown in FIG. 7B, even in a sample having a complicated step at the bottom of the groove, each step can be satisfactorily measured. Further, it is possible to measure a round hole having an extremely small diameter.

Further, there may be provided a correction means for applying a reference chip having a known height to correct an error factor of the measurement system. That is, by applying one or more kinds of height reference chips Cs having a known height Hs (or a known depth Ds), the height reference chips are scanned in a predetermined manner periodically or after the power of the apparatus is turned on. Obtain the backscattered electron signal profile of Cs. True shadow length Lf of the reference chip obtained from this
(Or penumbra shadow length Lh) and the known height Hs of the reference chip, the height calculation coefficient tan θ2 = (Hs / Lf),
(Or tan θ1 = (Hs / Lh)) is obtained as a calibration value. After that, using this calibrated height calculation coefficient tan θ2 (or tan θ1), the height Hx and depth Hx of the unknown test sample are calculated from the measurement of the true shadow length Lf or the penumbra shadow length Lh. To do. The height calculation coefficient tan θ
Instead of the correction means having 2 as the calibration value, the correction coefficient Hx / Hs is obtained from the calculated height Hx obtained by the measurement of the reference chip and the known height Hs, and the correction is made based on this correction coefficient. good. Therefore, by calibrating based on the reference chip of known height, it is possible to cancel various measurement error factors and aging factors of the measurement system, which is a great advantage that a further highly precise fine unevenness amount measuring device can be realized. can get.

The singularity D1 due to the convex edge when the true shadow length or the penumbra shadow length is obtained is such that the secondary electron is more accurately defined than the reflected electron when the slope is gentle. is there. In such a case, a singular point A1 (or B1) based on the backscattered electron profile and a singular point (or penumbra) from the singular point D1 based on the secondary electron profile
The height may be calculated by obtaining the shadow length.

Further, in the measurement of the edge pattern of a slope which is not a steep angle, the secondary electron detector 4 is used even if it is scanned.
As a result, an effective change cannot be obtained in the detection signals 1 and 42, so that the change point of the edge pattern may not be detected.
Therefore, as means for coping with this, a variable diaphragm mechanism capable of varying the aperture diameter of the aperture hole 52 in the reflection electron aperture angle limiting diaphragm 50 shown in FIG. 4 is provided. Regarding the aperture diameter of this variable aperture mechanism, firstly, when the aperture diameter is almost fully opened, it is possible to achieve a large aperture diameter that is almost equal to that when there is no aperture, and secondly, to the minimum aperture diameter that can be practically controlled. And At this time, the diaphragm mechanism is configured so that the center of the incident axis and the center of the aperture hole coincide with each other, and the diaphragm amount is controlled. Therefore, in the case of including a variable diaphragm mechanism that makes the aperture diameter of the aperture hole 52 variable, by controlling the aperture diameter as desired, it is possible to reduce the aperture diameter of FIG.
As shown in C, there is an advantage that a relatively wide aspect range can be supported.

FIG. 8 is a view for explaining a sample tilting mechanism for tilting a sample on a gentle slope. As shown in FIG. 8A, there is a case where there is no inclination of the backscattered electron extraction angle θ2 or more in an edge pattern of a gentle gentle slope or the like. In this case, since the shadow of the reflected electrons does not occur at the edge, no change can be obtained in the detection signals of the secondary electron detectors 41 and 42 even when scanning, and as a result, the change point of the edge pattern cannot be detected. . Therefore, as a means for responding to this, as shown in FIG. 8B, X that holds and moves the sample is used.
A mechanism for tilting the stage surface is additionally provided for the stage movable in the YZ axis directions. Alternatively, a mechanism for holding the sample and tilting it as desired is additionally provided. The measurement of the other slope may be performed in the same manner by inclining the sample in the opposite direction. Therefore, when the mechanism means for tilting the sample is provided, it becomes possible to set the reflected electron extraction angle θ2 or more with respect to the incident electron e1 (see FIG. 8C). As a result, the edge pattern of the gentle slope can be practically measured. As a result, there is an advantage that the measurable tilt range can be greatly expanded.

Further, if desired, in-lens type backscattered electron detectors for shape measurement are used as two secondary electron detectors for measurement in the X-axis direction, and two secondary electron detectors for measurement in the Y-axis direction. The fine unevenness amount measuring device may be configured to include a total of four secondary electron detectors. Then, the scan coil 70 is deflection-controlled in the X-axis direction and the Y-axis direction. In the case of this configuration, it is not necessary to rotate the stage on which the sample is placed by 90 degrees, so that it is possible to eliminate the measurement error due to the positioning error of the stage. The advantage that can be obtained is obtained.

Further, if desired, as shown in FIG. 4, the measurement of the fine unevenness amount which is configured to include both the conventional backscattered electron detectors 31 and 32 and the secondary electron detectors 41 and 42 of the present invention. It may be a device. Therefore, in the case where a constituent means that uses both the out-lens type backscattered electron detector and the in-lens type backscattered electron detector for shape measurement is provided, from the uneven portion close to vertical in the sample to the uneven portion on the gentle slope. The great advantage is that a wide range of edges and uneven parts can be measured simultaneously.

The in-lens type secondary electron detectors 43 and 44 shown in FIG. 9 may be provided. Even with this secondary electron detector, it is possible to satisfactorily measure a deep groove or edge having a high aspect ratio. If desired, backscattered electron detection and secondary electron detection may be switched in time, or may be used simultaneously.

Further, the out-lens type secondary electron detectors 45 and 46 of FIG. 10 may be provided. Even with this secondary electron detector, it is possible to satisfactorily measure a deep groove or edge having a high aspect ratio. If desired, backscattered electron detection and secondary electron detection may be switched in time, or may be used simultaneously. Also, if desired, FIG.
In-lens type secondary electron detectors 43 and 44 of FIG.
Both of the out-lens type secondary electron detectors 45 and 46 may be provided. Furthermore, the secondary electron detectors of the two systems may be switched in time and used, or may be used simultaneously. Further, the backscattered electron detection and the two-system secondary electron detection may be switched in time, or may be used simultaneously.

Further, the backscattered electron e9 which is bent due to the convergence effect of the objective lens shown in FIG. 11 may be detected. Also in this case, it is possible to satisfactorily measure a deep groove or edge having a high aspect ratio.

Further, a scanning electron microscope having a structure incorporating the above-described fine unevenness amount measuring device may be realized. In this case, there is a great advantage that it is possible to obtain a clearer SEM image with respect to a portion of the circuit chip, which is the sample to be tested, having a large aspect ratio of irregularities.

[0041]

The present invention has the following effects based on the above description. According to the invention configuration example of the in-lens type backscattered electron detector for shape measurement to which the backscattered electron opening angle limiting diaphragm of FIG. 4 described above is applied, the backscattered electron e2 from the sample is centered on the incident electron e1. Since only the backscattered electrons in the narrow angle range are detected, it is possible to satisfactorily measure a deep groove or edge having a remarkably high aspect ratio. Needless to say, it is possible to satisfactorily measure even an uneven portion such as a deep hole having a high aspect ratio. Also,
According to the invention configuration example of the in-lens type backscattered electron detector for shape measurement including the energy filter of FIG. 6, the deceleration voltage is applied to the energy filter 54, and secondary electrons having a certain energy or less are pulled back and cannot pass through. Therefore,
By controlling the deceleration voltage to a desired condition, it is possible to effectively separate the reflected electrons suitable for reception and the other electrons that are noise factors. Therefore, the SN of the received electrical signal
As a result of being able to improve the ratio, there is an advantage that the depth H of the groove having a high aspect ratio of the sample with higher measurement accuracy can be measured.
Further, by calibrating on the basis of a reference chip of known height, various measurement error factors and aging factors of the measurement system can be canceled out, so that there is a great advantage that a further highly precise fine unevenness amount measuring device can be realized. can get. Further, when a variable diaphragm mechanism that makes the aperture diameter of the aperture 52 variable is provided, by controlling the aperture diameter as desired, it becomes possible to cope with a relatively wide aspect range as shown in FIGS. 5B to 5C. Benefits are obtained. Further, when the mechanism means for tilting the sample is provided, it is possible to set the reflected electron extraction angle θ2 or more with respect to the incident electron e1 (see FIG. 8C), and as a result, it is possible to practically measure the edge pattern of the gentle slope. As a result, the merit that the measurable tilt range can be expanded is obtained.
Further, in the case of including a constituent means that uses both the out-lens type backscattered electron detector and the in-lens type backscattered electron detector for shape measurement in combination, from the uneven portion near vertical in the sample to the uneven portion on the gentle slope. The great advantage is that a wide range of edges and uneven parts can be measured simultaneously. Therefore, the technical effect of the present invention is great, and the economic effect in industry is also great.

[Brief description of drawings]

FIG. 1 is a principle structural diagram of a scanning electron microscope based on the application of backscattered electrons.

FIG. 2 is an explanatory view of the principle of measuring the height H of the convex shape of the sample by a predetermined scan.

FIG. 3 is a scanning explanatory diagram for measuring a depth H of a concave groove of a sample by scanning with a scan coil.

FIG. 4 is a principle structural diagram of an in-lens type backscattered electron detection device for shape measurement in which only secondary electrons reflected at a narrow angle are detected by a secondary electron detector according to the present invention.

FIG. 5 shows a case of a conventional out-lens backscattered electron detector and a case of an in-lens backscattered electron detector for shape measurement,
It is a relative explanatory view which shows the maximum measurable aspect ratio in three forms of the in-lens type backscattered electron detector for shape measurement to which the backscattered electron opening angle limiting diaphragm of the present invention is applied.

FIG. 6 is a structural example of the present invention in which an energy filter for removing unnecessary low-energy backscattered electrons and a deceleration voltage source are additionally provided.

FIG. 7 is a cross-sectional view of a sample showing complex irregularities and deep holes of the sample that can be measured by the present invention.

FIG. 8 is a diagram illustrating a sample tilting mechanism for tilting a sample on a gentle slope according to the present invention.

FIG. 9 is an in-lens type secondary electron detector 4 of the present invention.
3 is an example of a configuration including 3, 44.

FIG. 10 is an in-lens type secondary electron detector 4 of the present invention.
5 is an example of a configuration including 5 and 46.

FIG. 11 is an example of the configuration of the present invention in which backscattered electrons that bend due to the convergence effect of the objective lens are detected.

[Explanation of symbols]

20 Objective lens 31, 32 Backscattered electron detector (BSE detector) 40 Secondary electron conversion plate 41-46 Secondary electron detector 50 Reflection electron aperture angle limiting diaphragm 52 Open hole 54 Energy Filter 56 Deceleration voltage source 60 condenser lens 70 scan coils 100 stages

Claims (12)

[Claims] 1. A fine unevenness measuring apparatus for measuring the depth or height of a sample by scanning the surface of an object to be observed (sample) with an electron beam, wherein the reflected electrons due to the reflection of incident electrons irradiated on the sample. of,
Among the backscattered electrons passing through the inside of the objective lens, there is provided an in-lens type backscattered electron detection means for shape measurement, which receives only backscattered electrons within a predetermined angle region and converts them into an electric signal. Quantity measuring device. 2. The top and bottom of the sample are specified from a backscattered electron signal profile obtained by scanning a surface of an object to be observed (sample) with a predetermined known distance section by an electron beam,
Based on this, in a fine unevenness amount measuring device that measures the unevenness amount which is the depth or height of the sample, in the reflected electrons due to the reflection of the incident electrons irradiated on the sample,
Among reflected electrons passing through the inside of the objective lens, a reflected electron opening angle limiting diaphragm that allows only reflected electrons within a predetermined angle region to pass, and an electric signal that receives reflected electrons that have passed through the reflected electron opening angle limiting diaphragm An in-lens type backscattered electron detection unit for shape measurement, which is converted into, and a fine unevenness amount measuring apparatus, comprising: 3. The top and bottom of the sample are specified from the reflected electron signal profile obtained by scanning the surface of the object to be observed (sample) with a predetermined known distance section by an electron beam,
Based on this, in a fine unevenness amount measuring device that measures the unevenness amount which is the depth or height of the sample, in the reflected electrons due to the reflection of the incident electrons irradiated on the sample,
Among reflected electrons passing through the inside of the objective lens, a reflected electron opening angle limiting diaphragm that allows only reflected electrons within a predetermined angle region to pass, and an electric signal that receives reflected electrons that have passed through the reflected electron opening angle limiting diaphragm Of the in-lens type backscattered electron detection means for shape measurement, which is in charge of detecting uneven parts with a large aspect ratio, and backscattered electrons reflected from the sample irradiated with incident electrons.
An out-lens type backscattered electron detector for detecting backscattered electrons in a predetermined angle region below the objective lens to detect a recessed and projected portion having a small aspect ratio, . 4. The backscattered electron detecting means receives a backscattered electron in a predetermined angle region, converts the backscattered electron into a secondary electron corresponding to the backscattered electron, and emits the secondary electron. 4. The fine unevenness amount measuring device according to claim 1, further comprising: a secondary electron detecting unit that converts the signal into a signal and outputs the signal. 5. The secondary electron detecting means is two secondary electron detectors arranged and provided in a predetermined manner corresponding to the scanning axis direction of the sample, according to claim 4. Fine unevenness measuring device. 6. The two secondary electron detectors are two first secondary electron detectors, which are provided in a predetermined manner in correspondence with one scanning axis direction (X axis direction) of the sample, and Two second secondary electron detectors, which are orthogonal to the first secondary electron detector and are arranged in a predetermined manner corresponding to the other scanning axis direction (Y-axis direction) of the sample; The fine unevenness amount measuring device according to claim 4, further comprising: 7. An energy filter which allows reflected electrons having a certain energy or more to pass therethrough and other electrons having a certain energy or less to pass behind the objective lens, and a deceleration for supplying a predetermined negative deceleration voltage to the energy filter. The fine unevenness amount measuring device according to claim 1, further comprising: a voltage source. 8. A reference chip having a known depth Ds or a known height Hs is applied as a sample, and the reflected electron signal profile of the known depth Ds or the known height Hs is acquired by the reflected electron detection means and calculated from this. Calculated depth Dx or calculated height Hx and known depth Ds or known height H
It is characterized in that a correction value for correcting the measurement system is obtained and stored from the difference from s, and in subsequent measurement of an unknown sample, calculation correction is performed based on the stored correction value. The fine unevenness amount measuring device according to claim 1. 9. The backscattered electron aperture angle limiting diaphragm is provided with a variable aperture mechanism that is capable of varying the size of an aperture hole of backscattered electrons passing through the backscattered electron aperture angle limiting diaphragm. Alternatively, the fine unevenness amount measuring device described in 3. 10. A secondary electron signal profile is obtained by detecting secondary electrons emitted from a sample instead of reflected electrons reflected from the sample in order to identify a singular point of a convex edge of a measurement site of the sample. The fine unevenness amount measuring device according to claim 1, further comprising a secondary electron detector. 11. When the measurement site of the sample is a gentle slope where shadows of backscattered electrons do not occur, the sample on the stage is tilted at a predetermined angle so that the shadow is produced at the measurement site. The fine unevenness amount measuring device according to claim 1, further comprising a tilting mechanism. 12. A scanning electron microscope, comprising a structure for measuring an SEM image of a sample having a high aspect ratio by applying the fine unevenness amount measuring apparatus according to claim 1. Description: