JP3544865B2 - Substrate inspection apparatus, substrate inspection system including the same, and method of controlling substrate inspection apparatus - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a substrate inspection apparatus using an electron beam, a substrate inspection system using the same, and a substrate inspection method, and more particularly, to a substrate inspection apparatus that reduces a chromatic aberration of magnification while securing an irradiation area of a sample with a primary electron beam. The present invention also relates to a board inspection system and a board inspection apparatus control method using the same.
[0002]
[Prior art]
With the increasing integration of semiconductor devices, the sensitivity required for detecting defects and foreign substances on the substrate surface such as semiconductor wafers and photomasks has become increasingly higher. A semiconductor pattern defect inspection apparatus using an electron beam has been developed instead of the above. In this inspection device, an electron beam is formed by electron irradiating means and irradiates a sample substrate as a primary electron beam, and secondary electrons and reflected electrons generated according to changes in the shape, material and potential of the sample surface And a backscattered electron guided by an image projection means, focused, and enlarged and projected as a secondary electron beam onto an electron detection section to obtain a sample surface image. In particular, JP-A-7-249393 discloses a line. There has been proposed a method for improving the scanning speed by irradiating a sample with an electron beam having a rectangular or oblong cross section as a primary electron beam. In addition, in addition to this method, the primary electron beam is deflected by a Wien filter, which is an electron beam deflecting means, and is made to be perpendicularly incident on the sample surface, and the secondary electron beam passes through the same Wien filter. A method of directing the light to the projection means by going straight is proposed in Japanese Patent Application No. Hei 9-300275. FIG. 8 schematically shows a board inspection system provided with an inspection apparatus disclosed in Japanese Patent Application No. 9-300275.
[0003]
The substrate inspection system 100 shown in FIG. 1 includes a primary optical system 1, an electron gun controller 16 for controlling the primary optical system 1, a multi-stage quadrupole lens controller 17, a secondary optical system 2, and a secondary optical system lens control for controlling the same. Sections 52, 54 to 56, an electron detection section 3, an electron detection control section 57 for controlling the same, a Wien filter 41, a Wien filter control section 53 for controlling the same, a stage 43 and a stage voltage control section 51 for controlling the same, an image A signal processing unit 58, a host computer 59, a display unit 60, and a memory 61 are provided.
[0004]
The primary optical system 1 includes an electron gun and a multi-stage quadrupole lens system. The electron gun is a lanthanum hexaboride (LaB) having a rectangular electron emission surface having a major axis of 100 to 700 μm and a minor axis of 15 μm. ₆ A cathode 11, a Wehnelt electrode 12 having a rectangular opening, an anode 13 for extracting an electron beam and irradiating it as a primary electron beam 5, and a deflector 14 for adjusting a beam axis. The electron gun control unit 16 controls an acceleration voltage, an emission current, and the like of the primary electron beam 5. The quadrupole lens system includes a multi-stage quadrupole lens 15 that focuses the primary electron beam 5 under the control of the multi-stage quadrupole lens control unit 17.
[0005]
The primary electron beam 5 emitted from the cathode 11 is converged by the multi-stage quadrupole lens 15 and its control unit 17 so as to have a substantially rectangular cross-sectional shape, and enters the Wien filter 41 obliquely. Here, since the cathode 11 has a rectangular electron emission surface, the cross-sectional shape of the electron beam becomes substantially rectangular, and the irradiation area on the sample is enlarged, so that the inspection efficiency can be improved. The inspection efficiency can be increased by using an electron beam having an elongated cross section having an aspect ratio of more than 1 such as a line or a long ellipse other than a rectangle. However, an electron beam having various cross-sectional shapes is not limited to an elongated shape.
[0006]
The primary electron beam 5 is deflected by the Wien filter 41 in a direction perpendicular to the surface of the sample 42 and exits the Wien filter 41. Thereafter, the primary electron beam 5 is reduced by the cathode lens 21 which is a rotationally symmetric electrostatic lens, and is irradiated on the sample 42 as a substantially rectangular beam having a long axis of several hundred μm and a short axis of about 25 μm.
[0007]
FIG. 9 shows a basic configuration of the Wien filter 41. As shown in the figure, the Wien filters 41 are respectively arranged to face each other, and are controlled by a Wien filter control unit 53 (see FIG. 8) to control two rectangular parallelepiped electrodes 41a and 41b and two magnetic poles 41c and 41d. And Assuming that the Z axis is the optical axis of the projection system in the three-dimensional XYZ space shown in FIG. 1, the Wien filter 41 has a structure in which the electric field E and the magnetic field B are orthogonal to each other in an XY plane perpendicular to the Z axis. For the incident charged particles, only the charged particles satisfying the Wien condition qE = vB (q is the particle charge, and v is the speed of the linearly charged particles) function to travel straight.
[0008]
FIGS. 10A and 10B are explanatory views of the trajectory of the electron beam passing through the Wien filter 41, and both are sectional views of FIG. 9 cut along the XZ plane (Y = 0). As shown in FIG. 10A, in the substrate inspection system 100, a force F due to a magnetic field is applied to the primary electron beam 5 incident on the Wien filter 41. _B And the force F due to the electric field _E Act in the same direction, and the primary electron beam 5 is deflected so as to be perpendicularly incident on the surface of the sample 42. On the other hand, as shown in FIG. _B And the force F due to the electric field _E Acts in the opposite direction, and the Vienna condition F _B = F _E Holds, the secondary electron beam 6 goes straight without being deflected and enters the secondary optical system.
[0009]
Returning to FIG. 8, the stage 43 has a mechanism that can freely move horizontally with respect to each beam axis of the primary electron beam 5 and the secondary electron beam 6, thereby moving the sample 42 placed on the upper surface thereof. The entire surface can be scanned. The stage 43 can apply a negative voltage to the sample 42 by the stage voltage controller 51. Thus, incident damage to the sample 42 due to the primary electron beam 5 can be reduced.
[0010]
The electronic detection unit 3 includes an MCP (Micro Channel Plate) detector 31, a fluorescent plate 32, a light guide 33, and an image sensor 34 having a CCD or the like. The secondary electron beam 6 that has entered the MCP detector 31 via the secondary optical system 2 is amplified by the MCP detector 31 and irradiated on the fluorescent plate 32. At 34, it is detected as an image signal.
[0011]
This image signal is supplied to an image processing unit 58, where it is subjected to various kinds of signal processing, and is supplied to a host computer 59 as image data. The host computer 59 displays the image data on the display unit 60, and stores the image data using the memory 61.
[0012]
The secondary optical system 2 is provided between the cathode lens 21, the second lens 22, the third lens 23, and the fourth lens 24, which are rotationally symmetric electrostatic lenses, and between the second lens 22 and the third lens 23. And a field stop 26. The cathode lens 21, the second lens 22, the third lens 23, and the fourth lens 24 are controlled by secondary optical system lens controllers 52, 54, 55, and 56, respectively. The secondary optical system 2 also has a focal point F between the Wien filter 41 and the cathode lens 21. ₁ And an aperture stop 25 disposed in the focal plane 8 which is a plane perpendicular to the beam axis. The reason why the aperture stop 25 is arranged at the position of the focal plane 8 is that if the secondary electron beam 6 is to be imaged only by the cathode lens 21, the lens action becomes strong and aberrations are likely to occur. As shown in the explanatory view of the beam trajectory 7 of FIG. 7, both telecentric systems, that is, an optical system in which both the entrance pupil and the exit pupil exist at infinity, are formed together with the second lens 22 to perform one connection. This is because the chromatic aberration of magnification of the secondary electron beam 6 can be suppressed by causing an image to be formed and further providing the aperture stop 25 on the focal plane 8 of the imaging optical system 105.
[0013]
[Problems to be solved by the invention]
However, in the conventional substrate inspection system 100 having such a structure, in order to reduce the chromatic aberration of magnification of the secondary electron beam 5, the aperture of the aperture stop 25 is narrowed. There was a drawback that the upward irradiation area was limited. This is because the primary electron beam 5 from the aperture stop 25 to the sample 42 is focused on the focal point F on the aperture stop 25. ₁ Is incident on the sample 42, is subjected to a lens action by the cathode lens 21, and is illuminated perpendicularly to the sample 42 so as to be a Köhler illumination system.
[0014]
In addition, depending on the content of the test, there is a case where it is desired to widen or narrow the aperture of the aperture stop 25. In order to optimize the aperture in response to this, it is necessary to replace the aperture stop 25. is there. However, the conventional technique has a drawback that the vacuum atmosphere in the apparatus must be released each time the apparatus is replaced, and the efficiency of use of the apparatus becomes very poor.
[0015]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a substrate capable of suppressing the chromatic aberration of magnification of a secondary electron beam equivalently to a conventional technology while securing an irradiation area of a primary electron beam. An object of the present invention is to provide an inspection apparatus, an inspection system including the same, and a method of controlling a substrate inspection apparatus.
[0016]
[Means for Solving the Problems]
The present invention solves the above problems by the following means.
That is, according to the present invention,
Primary electron beam irradiating means for irradiating an electron beam as a primary electron beam to a substrate which is a sample,
The primary electron beam is incident on the surface of the substrate with its incident angle changed, and the secondary electron beam including secondary electrons and reflected electrons generated from the substrate by irradiation of the primary electron beam is captured. Electron beam deflecting means for passing through at an angle,
Including the electron beam deflecting means, while controlling and imaging the secondary electron beam, the imaging optical system forms a mutually conjugate telecentric system that forms an area that travels in parallel with the beam axis before and after the focal point. A plurality of projection means for controlling the secondary electron beam to make,
An electron beam detection unit that detects the secondary electron beam formed by the mapping projection unit at the last stage and outputs the image as an image signal,
A first stage which is disposed on a focal plane which is a plane perpendicular to the beam axis of the secondary electron beam passing through the focal point in the mapping projection means in the second and subsequent stages, and which determines an opening angle of the secondary electron beam Aperture angle aperture,
There is provided a substrate inspection apparatus including: an image display unit that receives an image signal supplied from the electron beam detection unit and displays an image representing a physical / electrical state of a surface of the substrate.
[0017]
The first opening angle aperture has first and second movable rectangular apertures each having a freely expandable / contractible aperture width, and the major axis directions thereof are substantially orthogonal to each other, and these first and second movable rectangular apertures. It is preferable to include first and second rectangular aperture driving means for varying the aperture width of the aperture.
[0018]
The substrate inspection apparatus according to the present invention further includes a second aperture stop disposed on a focal plane of the telecentric system in a region between the electron beam deflecting unit and the substrate, wherein the first aperture is provided. The angular aperture is provided with a first movable rectangular aperture having an expandable and contractible aperture width and a first rectangular aperture drive unit that varies the aperture width of the first movable rectangular aperture. A second movable rectangular diaphragm having a diaphragm width that can freely expand and contract, and a second rectangular diaphragm driving unit that varies the diaphragm width of the second movable rectangular diaphragm, the first and second movable rectangular diaphragms are: They may be arranged such that their major axes are substantially orthogonal to each other.
[0019]
The first and second movable rectangular diaphragms each have two metal flat plates, and the two metal flat plates are arranged to face each other on a long side to form the open angle diaphragm. Is preferred.
[0020]
The rectangular aperture driving means has a piezoelectric element connected to the metal flat plate, and drives the metal flat plate based on a change in the shape of the piezoelectric element to adjust the distance between the two metal flat plates. Good.
[0021]
Further, the cross-sectional shape perpendicular to the irradiation direction of the primary electron beam is preferably substantially rectangular.
[0022]
According to the present invention,
A board inspection system including a CPU, the above-described board inspection apparatus according to the present invention, signal processing means for processing the image signal and outputting image data, and storage means for storing the image data is provided. .
[0023]
According to the present invention,
Primary electron beam irradiating means for irradiating a substrate as a sample with an electron beam having a substantially rectangular cross section as a primary electron beam,
A first rotationally symmetric electrostatic lens that receives the primary electron beam, guides secondary electrons and reflected electrons generated from the substrate in a direction substantially perpendicular to the sample, and emits the secondary electron beam as a secondary electron beam,
The angle of incidence of the primary electron beam on the sample is changed so that the primary electron beam is incident on the surface of the sample, and the secondary electron beam emitted from the first rotationally symmetric electrostatic lens remains at the capture angle. An electric field magnetic field superimposed spectrometer to be passed;
A second rotationally symmetric electrostatic lens that is arranged at the subsequent stage of the electric field and magnetic field superimposed spectroscope and forms a first imaging optical system that forms a telecentric system together with the first rotationally symmetric electrostatic lens,
Two pieces disposed in a first focal plane, which is a focal plane of the first imaging optical system, having the incident direction of the primary electron beam as a long axis and being parallel to and separated from each other with a freely adjustable diaphragm width. A first aperture angle aperture having a metal flat plate,
Having a first piezoelectric element, a first opening angle aperture drive mechanism that varies the aperture width of the first aperture angle aperture,
A field stop disposed on the image plane of the first image forming optical system,
At least a pair of third and fourth rotationally symmetric electrostatic lenses forming a second imaging optical system forming a telecentric system conjugate with the first imaging optical system, disposed at a stage subsequent to the field stop, ,
A focal plane of the second imaging optical system, which is disposed on a second focal plane conjugate to the first focal plane, and is a direction substantially orthogonal to a major axis direction of the first aperture stop. A long aperture, a second aperture angle aperture having two metal flat plates spaced apart in parallel with each other with a freely adjustable aperture width,
Having a second piezoelectric element, a second opening angle aperture drive mechanism that varies the aperture width of the second aperture angle aperture,
An electron beam detection unit that detects the secondary electron beam imaged by the fourth rotationally symmetric lens and outputs the image as an image signal;
Image display means for receiving the supply of the image signal from the detection means, and displaying an image representing a physical and electrical state of the surface of the substrate,
A board inspection system including a host computer for processing the image signal is provided.
[0024]
According to the present invention,
An electron beam irradiating means for irradiating a substrate as a sample with an electron beam as a primary electron beam, and changing the incident angle of the primary electron beam so as to be incident on the surface of the substrate, receiving the primary electron beam, and Electron beam deflecting means for passing a secondary electron beam including a secondary electron and a reflected electron generated from a substrate at a capture angle, and a plurality of image projections including the electron beam deflecting means for imaging the secondary electron beam Means, the secondary electron beam imaged by the mapping projection means at the last stage, the electron beam detection means to output as an image signal, receiving the supply of the image signal from the electron beam detection means, A method for controlling a board inspection apparatus, comprising: an image display unit that displays an image representing a physical / electrical state of a surface of the board.
The secondary electron beam is controlled and imaged by controlling the secondary electron beam so that the secondary electron beam forms a mutually conjugate telecentric system by the plurality of projection units.
By arranging a first aperture stop at a first focal plane in the mapping projection means in the second and subsequent stages, an area for irradiating the substrate with the primary electron beam and the secondary electron beam are secured. A method for controlling a substrate inspection apparatus that reduces chromatic aberration of magnification of a beam is provided.
[0025]
The first aperture angle aperture is formed by two movable rectangular apertures each having a freely expandable / contractible aperture width and each major axis being substantially orthogonal to each other. By varying the aperture width of the movable rectangular aperture, it is preferable to control the opening angle independently in two directions substantially orthogonal to each other.
[0026]
Further, a second aperture angle aperture is further provided on a second focal plane in a region between the electron beam deflecting unit and the substrate, which is a focal plane of the first-stage mapping projection unit, The first and second opening angle diaphragms are respectively formed by first and second movable rectangular diaphragms having a freely expandable and contractible diaphragm width, and the first and second movable rectangular diaphragms have respective long axes mutually. A drive means for varying the aperture width of each of the first and second movable rectangular apertures, independently of each other in two directions substantially orthogonal to each other. Is better controlled.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, some embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same portions as those in FIGS. 8 to 10 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.
[0028]
FIG. 3 is a block diagram showing a first embodiment of the board inspection system according to the present invention. In the figure, the primary optical system 1 provided in the substrate inspection system 70, the electron gun control unit 16 and the multi-stage quadrupole lens control unit 17 for controlling the same, the electron detection unit 3, the electron detection control unit 57 for controlling the same, the Vienna FIG. 8 shows a filter 41, a Wien filter control unit 53 for controlling the filter 41, a stage 43 and a stage voltage control unit 51 for controlling the stage 43, an image signal processing unit 58, a host computer 59, a display unit 60 and a memory 61. It is the same as the substrate inspection system 100.
[0029]
The feature of the present embodiment is that the secondary lens system control unit 55, 56 of the secondary optical system 72 controls the third lens 23 and the fourth lens 24 to form both telecentric systems. An aperture angle stop 27 is provided in a focal plane 9 which is conjugate with the focal plane 8 in which the aperture angle stop 25 is provided in the prior art, that is, has a relationship in which the roles can be exchanged with each other in imaging. It is located.
[0030]
FIG. 4 is a block diagram of the secondary optical system 72 of the board inspection system 70 shown in FIG.
[0031]
As shown in the drawing, the secondary optical system 72 includes an aperture stop 27 that is characteristic of the present embodiment and is provided between the third lens 23 and the fourth lens 24. The host such that the optical system formed by the four lenses 24 forms both telecentric systems together with the imaging optical system 105 formed by the cathode lens 21 and the second lens 22 and forms an imaging optical system 75 conjugate to each other. The computer 59 controls the settings of the secondary optical system lens controllers 55 and 56 (see FIG. 3).
[0032]
With such a configuration, the secondary electron beam 6 (secondary electron / reflected electron / backscattered electron) generated from the surface of the sample 42 is emitted from the cathode lens 21 as is apparent from comparison with FIG. After the traveling direction is controlled by the beam path 7, as shown in the beam trajectory 7 in FIG. ₁ , Travels straight without deflecting inside the Wien filter 41, is collimated by the second lens 22 while being enlarged, that is, is controlled to travel parallel to the beam line axis, and forms an image on the field stop 26. I do. The traveling direction of the secondary electron beam 6 that has passed through the field stop 26 is again controlled by the third lens 23, and the focal point F of the aperture stop 27 on the focal plane 9 conjugate with the focal plane 8. ₂ And an image is formed on the lower surface of the MCP detector 31 by the fourth lens 24. In this way, the secondary electron beam 6 does not form an image between the third lens and the fourth lens, and the focus F ₂ Is formed to form an imaging optical system 75 conjugate with the imaging optical system 105, and in this imaging optical system 75, the aperture angle stop 27 is provided on the focal plane 9 conjugate with the focal plane 8. Thus, the chromatic aberration of magnification of the secondary electron beam generated by the cathode lens 21 can be suppressed by the aperture stop 27 which does not hinder the irradiation of the sample with the primary electron beam 5.
[0033]
Next, a second embodiment of the board inspection system according to the present invention will be described with reference to the drawings.
[0034]
FIG. 5 is a perspective view showing a part of the configuration of the board inspection system according to the present embodiment.
[0035]
As shown in the figure, the board inspection system 80 according to the present embodiment is different from the board inspection system shown in FIG. 4 in that the aperture angle stop 27 provided on the focal plane 9 is formed by two movable rectangular stops 81 and 82. There is a feature. The other points are the same as those of the board inspection system 70 shown in FIG.
[0036]
The movable rectangular diaphragms 81 and 82 are arranged on the focal plane 9 and have a structure in which the diaphragm width (short axis length) in the X direction and the Y direction in the orthogonal coordinates XY can freely expand and contract.
[0037]
FIG. 6 is a perspective view showing the basic configuration of the movable rectangular diaphragm 81. As shown in the figure, the movable rectangular diaphragm 81 includes two flat plates 86 and 87 formed of metal, for example, molybdenum (Mo), and has two edges 86e and 87e opposed by the flat plates 86 and 87. An aperture for controlling the amount of the next electron beam 6 is formed. The movable rectangular diaphragm 81 further includes rectangular diaphragm driving mechanisms 88 and 89 connected to the metal flat plates 86 and 87, respectively, and a movable rectangular diaphragm controller 90 for controlling the rectangular diaphragm driving mechanisms 88 and 89. . The rectangular aperture driving mechanisms 88 and 89 are formed using a motor, a piezoelectric element, or the like. In the present embodiment, a piezoelectric element is used as the piezoelectric element, and the movable rectangular aperture control unit 90 receives a voltage to apply a strain or stress. , Thereby driving the metal plates 86 and 87 in the X direction in mutually opposite directions. The amount of movement of the metal flat plates 86 and 87 by the piezoelectric element is about 100 μm when a piezo element is used, for example. In this way, the rectangular aperture drive mechanisms 88 and 89 can adjust the distance 81 g between the plate edges and adjust the aperture width of the rectangular aperture 81, that is, the size in the X direction.
[0038]
The movable rectangular diaphragm 82 also has a configuration similar to that of the movable rectangular diaphragm 81. The metal flat plate is disposed so as to be orthogonal to the metal flat plates 86 and 87 of the movable rectangular diaphragm 81 shown in FIG. It is formed so that it can be adjusted.
[0039]
Since the substrate inspection system 80 according to the present embodiment includes the two movable rectangular apertures 81 and 82 having such a configuration, the vacuum atmosphere in the substrate inspection apparatus is released to replace the open angle aperture. The aperture stop can be adjusted to an optimal size without any adjustment, and can be independently adjusted in two directions orthogonal to each other on a plane perpendicular to the beam axis of the secondary electron beam 6. it can. Thereby, in addition to the effects of the above-described first embodiment, a board inspection system that can adjust the aperture angle stop according to the content of the test is provided.
[0040]
Next, a third embodiment of the board inspection system according to the present invention will be described with reference to the drawings.
[0041]
FIG. 1 is a block diagram showing a basic configuration of a board inspection system 90 according to the present embodiment. As is clear from comparison with FIG. 3, the feature of the substrate inspection system 90 according to the present embodiment is that the mapping projection system has the same specifications as the second embodiment on the mutually conjugate focal planes 8 and 9. The movable rectangular diaphragms 91 and 92 are disposed so that their major axes are orthogonal to each other. The other points are the same as in the first embodiment.
[0042]
A more detailed configuration of the secondary optical system of the board inspection system 90 according to the present embodiment is shown in a perspective view of FIG.
[0043]
As shown in the figure, a movable rectangular diaphragm 91 is disposed on a focal plane 8 between the Wien filter 41 and the cathode lens 21, and is a focal plane conjugate with the focal plane 8, A movable rectangular stop 92 is disposed on the focal plane 9 between the four lenses 24.
[0044]
In the XYZ space shown in the figure, the movable rectangular diaphragm 91 is disposed such that the major axis direction is the same as the major axis direction of the substantially rectangular cross section of the primary electron beam 5.
[0045]
By providing the movable rectangular diaphragm 91 having such a structure on the focal plane 8, the primary electron beam 5 can adjust the opening angle only in the X direction without limiting the opening angle in the Y direction. it can. Thereby, the irradiation area of the primary electron beam 5 is sufficiently secured. This structure is particularly effective when it is not desirable to irradiate the sample 42 with the primary electron beam 5 more than necessary, for example, when it is desired to avoid charge-up or contamination of the sample 42.
[0046]
Further, the movable rectangular stop 92 on the focal plane 9 is installed so that the major axis direction thereof is in the X direction, and is disposed so as to be orthogonal to the long axis of the movable rectangular stop 91. Thereby, it is possible to shape the secondary electron beam 6 in two directions, the X direction and the Y direction, and it is possible to reduce chromatic aberration of magnification.
[0047]
That is, the opening angle of the secondary electron beam 6 in the X direction is adjusted by the movable rectangular aperture 91, the opening angle in the Y direction is adjusted by the movable rectangular aperture 92, and the movable rectangular apertures 91 and 92 are respectively adjusted. Since they are on the conjugate planes 8 and 9 of the secondary optical system, apertures having a shape in which movable rectangular apertures 91 and 92 are superimposed on the secondary electron beam 6 are provided on the conjugate planes 8 and 9 respectively. An equivalent aberration reducing effect can be obtained.
[0048]
As described above, according to the board inspection system 90 according to the present embodiment, two movable rectangular diaphragms 91 and 92 whose major axis directions are orthogonal to each other are provided on the mutually conjugate focal planes 8 and 9, respectively. Further, the focus F of the primary electron beam 5 ₁ Is formed on the focal plane 8 where the aperture is formed, so that the major axis of the aperture of the open angle aperture is in the same direction as the major axis of the substantially rectangular cross section of the primary electron beam 5, so that the primary electron beam 5 is irradiated. It is possible to reduce the aberration of the secondary electron beam without limiting the area. Further, since the two movable rectangular diaphragms can be arranged at different plane positions, the driving mechanism is different from the case where two movable rectangular diaphragms are simultaneously provided on a single diaphragm position plane as in the second embodiment. There is an advantage that a sufficient installation space can be secured.
[0049]
【The invention's effect】
As described in detail above, the present invention has the following effects.
[0050]
That is, according to the substrate inspection apparatus of the present invention, a plurality of projection units for controlling the secondary electron beam so as to form a mutually conjugate telecentric system, and a focal plane in the second and subsequent projection units. With the aperture stop provided, the chromatic aberration of magnification of the secondary electron beam can be suppressed without limiting the irradiation area of the primary electron beam on the substrate. Thereby, the inspection area of the substrate can be enlarged without lowering the resolution performance of the projection unit.
[0051]
In the case where the first and second movable rectangular diaphragms whose major axis directions are substantially orthogonal to each other are provided on the focal planes of the second and subsequent stages, the opening angles are independently adjusted in two directions perpendicular to the beam axis. Since it is possible to adjust the aperture angle to the optimal one without opening the vacuum atmosphere in the apparatus and replacing the aperture angle aperture. As a result, the downtime of the apparatus can be significantly reduced, and the usage efficiency can be improved.
[0052]
In the case where a second aperture stop is provided on the focal plane of the telecentric system between the electron beam emitting means and the substrate, and the movable rectangular aperture is provided as the first and second aperture stops, the above is described. In addition to the effect, the space for the drive mechanism of the movable rectangular diaphragm can be secured, so that the flexibility in device design is improved. Further, since the second movable rectangular aperture is disposed so that its major axis direction is the same as the major axis direction of the primary electron beam, the aperture width can be adjusted only in the minor axis direction of the primary electron beam. Thus, it is possible to prevent the primary electron beam from irradiating the sample with a necessary amount or more, thereby preventing charge-up and contamination of the sample.
[0053]
Further, according to the control method of the substrate inspection apparatus according to the present invention, since the mapping projection means controls and forms an image of the secondary electron beam so as to form a mutually conjugate telecentric system, It is possible to arrange an aperture stop on the focal plane in the projection means, and it is possible to control the substrate inspection apparatus so as to achieve the above-described effects.
[0054]
Further, according to the substrate inspection system according to the present invention, the above-described substrate inspection apparatus can be operated by the above-described control method, so that the substrate can be charged with excellent resolution and high efficiency while preventing charge-up and contamination of the sample. Inspection can be performed.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a third embodiment of a board inspection system according to the present invention.
FIG. 2 is a perspective view showing a more detailed configuration of a secondary optical system of the substrate inspection system shown in FIG.
FIG. 3 is a block diagram showing a first embodiment of the board inspection system according to the present invention.
4 is a block diagram showing a trajectory of a secondary electron beam in the substrate inspection system shown in FIG.
FIG. 5 is a block diagram showing a part of the configuration of a second embodiment of the board inspection system according to the present invention.
FIG. 6 is a block diagram showing details of a movable rectangular stop of the substrate inspection system shown in FIG. 5;
FIG. 7 is a block diagram showing a trajectory of a secondary electron beam in the conventional substrate inspection system shown in FIG.
FIG. 8 is a block diagram showing an example of a conventional board inspection system using a Wien filter.
FIG. 9 is a perspective view showing a detailed configuration of the Wien filter shown in FIG. 8;
FIGS. 10A and 10B are explanatory diagrams showing the function of the Wien filter shown in FIG. 9;
[Explanation of symbols]
1 Primary optical system
2,72,73 Secondary optical system
3 electron detector
5 Primary electron beam
6. Secondary electron beam (direction of travel)
7 Secondary electron beam orbit
8,9 Focal plane
11 Cathode
12 Wehnelt electrode
13 Anode
14 Deflector
15 Multi-stage quadrupole lens
16 electron gun controller
17 Multi-stage quadrupole lens controller
21 Cathode lens
22 Second lens
23 Third lens
24 Fourth lens
25, 27 aperture angle aperture
26 Field stop
31 MCP detector
32 fluorescent screen
33 Light Guide
34 Image sensor
41 Wien filter
41a, 41b electrodes
41c, 41d Magnetic pole
42 samples
43 stages
51 Stage voltage controller
52, 54-56 Secondary optical system lens controller
53 Wien filter controller
57 Electronic detection control unit
58 Image signal processing unit
59 Host computer
60 Display
61 memory
70,80,90 Board inspection system
75,105 Imaging optical system
81, 82, 91, 92 Movable rectangular diaphragm
81g Distance between flat plate edges
86,87 metal plate
88, 89 Rectangular aperture drive mechanism
90 Movable rectangular aperture control unit

Claims (11)

Primary electron beam irradiating means for irradiating an electron beam as a primary electron beam to a substrate which is a sample,
The primary electron beam is incident on the surface of the substrate by changing its incident angle, and the secondary electron beam including secondary electrons and reflected electrons generated from the substrate by irradiation of the primary electron beam is captured. Electron beam deflecting means for passing through at an angle,
Including the electron beam deflecting means, while controlling and imaging the secondary electron beam, the imaging optical system forms a mutually conjugate telecentric system that forms a region that travels in parallel with the beam axis before and after the focal point. A plurality of projection means for controlling the secondary electron beam to make,
An electron beam detection unit that detects the secondary electron beam formed by the mapping projection unit in the last stage and outputs the image as an image signal,
A first stage which is disposed on a focal plane which is a plane perpendicular to the beam axis of the secondary electron beam passing through the focal point in the mapping projection means of the second and subsequent stages, and which determines an opening angle of the secondary electron beam Aperture angle aperture,
A substrate inspection apparatus comprising: an image display unit that receives an image signal from the electron beam detection unit and displays an image representing a physical / electrical state of a surface of the substrate. The first opening angle diaphragm has first and second movable rectangular diaphragms, each having a freely expandable and contractible diaphragm width, and whose major axis directions are substantially orthogonal to each other, and these first and second movable rectangles. 2. The substrate inspection apparatus according to claim 1, further comprising first and second rectangular aperture driving means for varying the aperture width of the aperture. A second aperture stop provided at a focal plane of the telecentric system in a region between the electron beam deflecting unit and the substrate,
The first opening angle diaphragm includes a first movable rectangular diaphragm having an expandable and contractible diaphragm width and a first rectangular diaphragm driving unit that varies the diaphragm width of the first movable rectangular diaphragm.
The second opening angle aperture is provided with a second movable rectangular aperture having an expandable and contractible aperture width and a second rectangular aperture drive unit that varies the aperture width of the second movable rectangular aperture,
2. The substrate inspection apparatus according to claim 1, wherein the first and second movable rectangular diaphragms are disposed so that their major axes are substantially orthogonal to each other. The first and second movable rectangular diaphragms each have two metal flat plates, and the two metal flat plates are arranged to face each other on a long side to form the open angle diaphragm. The substrate inspection apparatus according to claim 2 or 3, wherein: The rectangular aperture driving means has a piezoelectric element connected to the metal plate, and drives the metal plate based on a change in the shape of the piezoelectric element to adjust a distance between the two metal plates. The substrate inspection apparatus according to claim 4, wherein: The substrate inspection apparatus according to any one of claims 1 to 5, wherein a cross-sectional shape perpendicular to the irradiation direction of the primary electron beam is substantially rectangular. A CPU,
A board inspection apparatus according to any one of claims 1 to 6,
Signal processing means for processing the image signal and outputting image data,
A substrate inspection system comprising: a storage unit configured to store the image data. Primary electron beam irradiating means for irradiating a substrate as a sample with an electron beam having a substantially rectangular cross section as a primary electron beam,
A first rotationally symmetric electrostatic lens that receives irradiation of the primary electron beam, guides secondary electrons and reflected electrons generated from the substrate in a direction substantially perpendicular to the sample and emits the secondary electron beam,
The primary electron beam is incident on the sample surface by changing the angle of incidence of the primary electron beam on the sample, and the secondary electron beam emitted from the first rotationally symmetric electrostatic lens remains at the capture angle. An electric field magnetic field superimposed spectrometer to be passed;
A second rotationally symmetric electrostatic lens that is arranged at a stage subsequent to the electric field and magnetic field superimposed spectroscope and forms a first imaging optical system that forms a telecentric system together with the first rotationally symmetric electrostatic lens,
Two pieces disposed on a first focal plane, which is a focal plane of the first imaging optical system, with the incident direction of the primary electron beam as a long axis, and separated in parallel with each other with a freely adjustable diaphragm width. A first aperture angle aperture having a metal flat plate,
Having a first piezoelectric element, a first opening angle aperture drive mechanism that varies the aperture width of the first aperture angle aperture,
A field stop disposed on an image plane of the first image forming optical system,
At least a pair of third and fourth rotationally symmetric electrostatic lenses forming a second imaging optical system forming a telecentric system conjugate to the first imaging optical system, disposed at a stage subsequent to the field stop, ,
A focal plane of the second imaging optical system, which is disposed on a second focal plane conjugate to the first focal plane, and is substantially orthogonal to a major axis direction of the first aperture stop; A long aperture, a second aperture angle aperture having two metal flat plates spaced apart in parallel with each other with a freely adjustable aperture width,
A second opening angle aperture drive mechanism having a second piezoelectric element, and varying the aperture width of the second aperture angle aperture,
An electron beam detection unit that detects the secondary electron beam imaged by the fourth rotationally symmetric lens and outputs the image as an image signal;
Image display means for receiving an image signal from the detection means and displaying an image representing a physical / electrical state of the surface of the substrate,
A board inspection system comprising: a host computer configured to process the image signal. Electron beam irradiation means for irradiating a substrate as a sample with an electron beam as a primary electron beam, the primary electron beam being incident on the surface of the substrate by changing its incident angle, receiving the primary electron beam, Electron beam deflecting means for passing a secondary electron beam including a secondary electron and a reflected electron generated from a substrate at a capture angle, and a plurality of image projections including the electron beam deflecting means for forming an image of the secondary electron beam Means, the secondary electron beam imaged by the last projection projection means, the electron beam detection means to output as an image signal, receiving the supply of the image signal from the electron beam detection means, A method for controlling a substrate inspection apparatus, comprising: an image display unit that displays an image representing a physical / electrical state of the surface of the substrate.
The secondary electron beam is controlled and imaged by controlling the secondary electron beam so that the secondary electron beam forms a mutually conjugate telecentric system by the plurality of mapping projection means,
By arranging a first opening angle stop on a first focal plane in the mapping projection means in the second and subsequent stages, an area for irradiating the substrate with the primary electron beam and the secondary electron beam are secured. A method for controlling a substrate inspection apparatus, which reduces chromatic aberration of magnification of a beam. The first opening angle aperture is formed of two movable rectangular apertures each having a freely expandable / contractible aperture width and each major axis being substantially orthogonal to each other, and further using a rectangular aperture drive unit further comprising: The control method of the substrate inspection apparatus according to claim 9, wherein the opening angle is independently controlled in two directions substantially orthogonal to each other by varying a stop width of the movable rectangular stop. A second aperture angle aperture is further provided on a second focal plane in a region between the electron beam deflecting unit and the substrate on the focal plane of the first-stage mapping projection unit,
The first and second opening angle apertures are formed by first and second movable rectangular apertures each having a freely adjustable aperture width,
The first and second movable rectangular diaphragms are disposed such that their long axes are substantially orthogonal to each other,
The substrate according to claim 9, further comprising: a driving unit configured to change the width of each of the first and second movable rectangular diaphragms to independently control an opening angle in two directions substantially orthogonal to each other. Inspection device control method.

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