JP2005174568A - Objective lens, electron beam apparatus, and device manufacturing method using the same - Google Patents

Abstract

An object of the present invention is to provide a cathode having a long lifetime without being affected by ions generated in a lens barrel, and appropriately arranging a plurality of electron beams around an optical axis, and in some cases, a plurality of electron beams of five or more from one electron gun. An electron beam apparatus capable of forming
An electron beam apparatus for focusing and scanning an electron beam emitted from an electron gun of a ZrO / W (tungsten zirconic acid) cathode or a transition metal carbide cathode on the sample in the direction of the optical axis. The electron beam apparatus was provided with a plate for reducing the vacuum conductance between the electron gun chamber side and the sample side, and an opening for allowing the electron beam to pass through the plate at a position away from the optical axis.
[Selection] Figure 1

Description

  The present invention relates to an electron beam apparatus, and more particularly to an electron beam apparatus that performs high-throughput evaluation of a substrate (sample) having a pattern with a minimum line width of less than 0.1 μm. The present invention also relates to an electron beam apparatus capable of evaluating a pattern on a wafer with high throughput and forming a pattern on a wafer with high throughput when the wafer diameter is increased to 300 mmΦ or more. Furthermore, it is related with the method of manufacturing a device using such an electron beam apparatus.

In recent years, an electron beam has been used for pattern evaluation on a substrate and for forming a pattern on a substrate. As a device that emits an electron beam, there is an electron beam device using a ZrO / W (tungsten zirconate) cathode electron gun. In this electron beam apparatus, a predetermined opening is conventionally formed on the optical axis, and the substrate is irradiated with the electron beam through this opening. At this time, the exhaust conductance was reduced by making the opening minute, and the electron gun chamber could be kept in an ultra-high vacuum.
In addition, for the purpose of improving throughput during pattern evaluation and pattern formation, a plurality of electron beams may be formed based on an electron beam emitted from a ZrO / W cathode electron gun. In this case, a method of forming up to four electron beams has been proposed from the characteristics of the electron gun.

Moreover, as for the electron beam from the ZrO / W cathode electron gun, only the electron beam of about 10% of the total energy is used for actual scanning or the like, and the remaining electron beam is not used. On the other hand, it has been known that an electron beam from a carbide cathode of a transition metal such as TaC is not emitted in the optical axis direction but a strong electron beam is emitted only in four directions outside the optical axis.
Furthermore, as a magnetic lens used in an electron beam apparatus that handles a plurality of electron beams, a magnetic lens in which a plurality of optical axes pass through a central region of a plate having a circular outer shape has been used.

However, each of the conventional electron beam devices has the following problems. That is, when a minute aperture through which an electron beam is passed is formed on the optical axis, there is a problem that ions generated in the lens barrel portion on the downstream side of the minute aperture pass through the minute aperture and damage the cathode. It was. This is because ions have a positive charge, are accelerated by an electric field formed by the cathode and the anode, collide with the cathode along the optical axis, and the cathode is subjected to ion bombardment.
Further, even when a plurality of electron beams are used, if only about four electron beams are formed, there is a problem that the throughput during pattern evaluation and pattern formation is not improved so much.

For the ZrO / W cathode, four electron beams in the off-axis direction, which is much stronger than the electron beam emitted in the optical axis direction, were not used. On the other hand, regarding the TaC cathode, although strong electron beams are emitted, these strong electron beams have not been effectively used.
In addition, if an electron beam with high intensity is focused finely, the electron beam is blurred due to the space charge effect, and there is a problem that it cannot be focused sufficiently thinly.
In addition, when a magnetic lens having a plurality of optical axes is used in the central region of a plate having a circular outer shape, the optical axis is a matrix such as 3 rows 3 columns, 4 rows 4 columns, or 5 rows 5 columns. Arranged in a shape. For this reason, the distance from the coil to each optical axis is different, and as a result, the lens strength in the optical axis in the region (peripheral region) close to the coil of the magnetic lens is There was a problem that the lens strength was slightly different. Furthermore, when pattern evaluation is performed while continuously moving the sample stage using electron beams arranged in a matrix, there is a problem that the evaluation regions overlap.

The present invention has been made in view of the above problems, has a long life of the cathode without being affected by ions generated in the lens barrel, and is appropriately arranged around the optical axis of a plurality of electron beams. An object is to provide an electron beam apparatus capable of forming a plurality of electron beams of five or more from one electron gun.
Also, it is possible to provide an electron beam apparatus that can reach four specimens without reducing the luminance, and can suppress a space charge effect as much as possible to narrow down a large current electron beam to a small diameter. With the goal.

Further, the present invention provides an objective lens capable of forming a plurality of electron beams on a single wafer, having no problem of overlapping evaluation areas, and providing an objective lens having substantially the same lens intensity for any electron beam. Objective.
Furthermore, it aims at providing the device manufacturing method using such an electron beam apparatus or the electron beam apparatus which has an objective lens.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided an electron gun that emits an electron beam from a ZrO / W cathode or a carbide cathode of a transition metal, and an electron beam emitted from the electron gun in an off-axis direction. An electron beam system that has an electron optical system that focuses and scans on a sample. An electromagnetic lens is provided between the electron gun and the sample, and the amount of rotation around the optical axis of the electron beam is adjusted using this electromagnetic lens. It is configured to do.

  According to the second aspect of the present invention, an electron gun that emits an electron beam from a ZrO / W cathode or a carbide cathode of a transition metal, and an electron that focuses and scans the electron beam emitted from the electron gun in an off-axis direction on the sample. An electron beam apparatus having an optical system is configured to have a shaped aperture plate that forms 5 to 8 electron beams.

  According to a third aspect of the present invention, an electron gun that emits an electron beam from a ZrO / W cathode or a carbide cathode of a transition metal, and an electrostatic lens that focuses the electron beam emitted from the electron gun in the off-axis direction are provided. The electrostatic lens is provided close to the cathode and a positive voltage is applied to irradiate the NA aperture of the NA aperture plate with an electron beam.

According to a fourth aspect of the present invention, in the electron beam apparatus according to the third aspect, the electrostatic lens has a structure in which three electrodes are superposed, and a central electrode of these three electrodes has a thickness of 2 mm. The configuration is as described above.
According to a fifth aspect of the present invention, in the electron beam apparatus according to the fourth aspect, the opening formed in the central electrode has a configuration in which the inner diameter on the cathode side is smaller than the inner diameter on the NA aperture plate side.

  According to a sixth aspect of the present invention, a thin plate portion made of a ferromagnetic material and having a longitudinal axis in the first direction and a thick plate portion having a rib structure surrounding the periphery of the thin plate portion, the optical axis of the electron beam in the thin plate portion is provided. A first component having a plurality of pipe-shaped protrusions at a position corresponding to the above, a thin plate portion made of a ferromagnetic material and having a longitudinal axis in the first direction, and a thick plate portion having a rib structure surrounding the periphery of the thin plate portion, A second part in which a plurality of openings are formed at positions corresponding to the optical axis of the electron beam in the thin plate part, and a part corresponding to each optical axis is shared by the first part and the second part And a coil wound along a direction orthogonal to each optical axis, and provided between each thick plate portion of each component generated when combined with a predetermined gap. .

According to a seventh aspect of the present invention, in the objective lens according to the sixth aspect, the magnetic field lines generated when a current is passed through the coil are formed so that a lens gap that goes out of the ferromagnetic body is formed toward the sample side. A configuration is adopted in which the relationship between the distance between the thin plate portions of the first and second parts and the length of the pipe-shaped projection in the optical axis direction is designed.
According to an eighth aspect of the present invention, the objective lens according to the sixth or seventh aspect is used to scan the electron beam in the first direction while continuously moving the sample stage in the second direction perpendicular to the first direction. Thus, a configuration is adopted in which pattern evaluation or pattern drawing of a sample is performed.

According to the ninth aspect of the present invention, there is provided an objective lens for focusing the electron beam from the electron gun onto the sample. The objective lens includes an excitation coil, an inner magnetic pole in the vicinity of the optical axis of the electron beam, and the inner magnetic pole. It has a structure surrounded by an outer magnetic pole arranged outside and a magnetic circuit connected between the inner magnetic pole and the outer magnetic pole, and the lens gap formed between the inner magnetic pole and the outer magnetic pole is on the sample side. While being opened, the inner magnetic pole and the outer magnetic pole have a truncated cone shape that gradually spreads from the sample side toward the electron gun side.
In the invention described in claim 10, the objective lens described in claim 9 is configured such that an axially symmetric electrode to which a positive voltage is applied is provided between the objective lens and the sample. Yes.
The invention described in claim 11 employs the objective lens described in claim 9 or 10 in which an E × B separator is provided inside the inner magnetic pole.

The invention described in claim 12 employs a configuration in which pattern evaluation or pattern formation is performed using the electron beam apparatus according to any one of claims 1 to 5.
According to a thirteenth aspect of the present invention, there is provided a device manufacturing method, wherein pattern evaluation or pattern formation is performed using the electron beam apparatus including the objective lens according to any one of the sixth to eleventh aspects.

Since there is no opening on the optical axis between the electron gun chamber and the lens barrel portion, there is an effect that ions from the lens barrel portion do not collide with the cathode and damage the cathode. Further, in the present invention, since the two-stage electromagnetic lens is provided between the aperture plate having four apertures and the sample, these electromagnetic lenses can have a short focal length, and the optical path length between the aperture plate and the sample is 30 cm or less. Can be. For this reason, the space charge effect can be reduced, and an electron beam having a larger current can be formed with a small size.
In addition, since a large number of electron beams are formed, the pattern on the sample can be evaluated or the pattern formation throughput can be improved.

  First, based on FIG. 1, the structure of the electron beam apparatus 1 which concerns on one Embodiment of this invention is demonstrated in order toward the downstream from the upstream of optical axis OA. FIG. 1 is a schematic view showing the entire electron beam apparatus 1. The electron beam apparatus 1 is provided with an electron gun 2, and the electron gun 2 includes a ZrO / W cathode 2a that emits an electron beam, and a cathode heating filament 2b that heats the ZrO / W cathode 2a. Yes. The ZrO / W cathode 2a and the cathode heating filament 2b are surrounded by a Schottky shield 2c. The Schottky shield 2c is for repelling the thermal electrons from the cathode heating filament 2b so as not to affect the electron beam. In addition, a predetermined opening is formed in the vicinity of the ZrO / W cathode 2a in the Schottky shield 2c, and an electron beam passes through this opening. The cathode may be a transition metal carbide cathode, which will be described later.

  The Schottky shield 2c is surrounded by the electron gun chamber 2d, and a flat plate-like anode 4 functioning as an orifice is provided at a position corresponding to the optical axis OA on the outer surface of the electron gun chamber 2d. It has been. In the anode 4, four minute openings 4 a (only two are shown in the figure) are formed at positions slightly shifted from the optical axis OA. Here, since the minute opening 4a is very small, the space between the electron gun chamber 2d side and the lens barrel 17 on the sample 15 side is partitioned, and the vacuum conductance is kept small. At the same time, the position and shape of the four minute apertures 4a in the anode 4 are such that a portion of the electron beam having a high intensity among the electron beams emitted from the optical axis OA and emitted in the off-axis direction can pass. Designed properly.

  A rotation control lens 5 is provided on the downstream side of the anode 4. The rotation control lens 5 has a two-stage structure along the optical axis OA, and two coils 5a and 5b are wound around each stage. The coils 5a and 5b are controlled so that currents flow in opposite directions so that the directions of the magnetic fields generated are opposite to each other. The rotation control lens 5 having a two-stage structure is configured so that the bore diameter and the magnetic gap of each stage are equal, and when an equal current flows through each of the coils 5a and 5b, the optical axis of the electron beam. The surrounding rotations cancel each other. On the other hand, the amount of right or left rotation around the optical axis OA can be increased or decreased by relatively changing the ratio of the current flowing through the coils 5a and 5b.

More specifically, in a state where the rotational action of the rotation control lens 5 is not substantially functioning, for example, both lines connecting the centers of two electron beams having high intensities exist on the Y axis. Assume that In this state, when a predetermined ratio of current flows through the coils 5a and 5b, the centers O ₁ and O ₂ having high electron beam intensity are connected by the rotation action of the rotation control lens, as shown in FIG. A predetermined rotation angle θ is generated between the ellipse and the y-axis. FIG. 2 shows, as an example, a case where the origin is the position of the optical axis and each electron beam has a rotation angle θ around the optical axis. The reason why the rotation angle of the electron beam around the optical axis is adjusted as described above is so that the portion where the intensity of the electron beam is maximum coincides with the position of a beam shaping aperture described later. The rotation control lens has a rotation function as described above, and also has a function of focusing an electron beam.

  A molding plate 19 that molds an electron beam is provided on the downstream side of the rotation control lens 5. A large number (eight in FIG. 1 and FIG. 2) of beam shaping openings are formed in the shaping plate 19, and both ends in the Y-axis direction are beam shaping openings 19a and 19b. As shown in FIG. 2, the beam shaping apertures are all equally spaced when projected onto the Y axis, and all the beam shaping apertures have an electron beam intensity of 80% or more irradiated through the anode 4. It arrange | positions so that the inside of the area | region 20 may be entered. Here, the electron beam intensity of 80% means that the intensity of the position (usually the central part) where the beam intensity is the strongest in the region 20 is 100%, and the intensity is 80%.

An NA aperture plate 6 having an NA aperture 6 a is provided on the downstream side of the molding plate 18, and a reduction lens 7 is provided on the downstream side of the NA aperture plate 6. Further, electrostatic deflectors 8 and 11 are provided further downstream of the reduction lens 7 so that the electron beam can be deflected. A magnetic lens 12 is provided in the vicinity of the electrostatic deflector 8. Further, a sample 15 is disposed at the most downstream portion of the optical axis OA, and the surface of the sample 15 is irradiated with an electron beam.
In addition, an axisymmetric electrode 14 to which a positive voltage is applied in order to accelerate secondary electrons emitted from the sample 15 is provided in the vicinity of the surface of the sample 15. A magnetic lens 12 and an E × B separator 9 (an electrostatic deflector 9a and an electromagnetic deflector 9b) are provided in a direction in which the optical axis OA returns further upstream from the axially symmetric electrode 14. Further, a secondary electron detector 21 is provided in the direction in which the electron beam is deflected by the E × B separator 9.

Next, the operation of the electron beam apparatus 1 will be described. A part of the electron beam emitted from the ZrO / W cathode 2a travels toward the anode 4. Then, it passes through the four minute openings 4a at positions slightly shifted from the optical axis OA. At this time, the ions generated in the lens barrel are accelerated toward the cathode by the electric field created by the cathode 2a and the anode 4, but since the minute aperture 4a is displaced from the optical axis, the ions directly collide with the cathode 2a. Is avoided.
The four electron beams that have passed through the minute aperture 4 a of the anode 4 are rotated and focused around the optical axis OA by the rotation control lens 5 and pass through the beam shaping aperture of the shaping plate 19. The eight beam shaping openings including the beam shaping openings 19a and 19b at both ends of the shaping plate 19 have the same intervals when projected onto the Y axis as described above (see FIG. 2).

The electron beam shaped by the beam shaping aperture forms a crossover at the NA aperture 6 a of the NA aperture plate 6. The electron beam that has passed through the NA aperture is reduced by the reduction lens 7 and the magnetic lens (objective lens) 12, and the surface of the sample 15 is irradiated with eight electron beams. At this time, the electron beam is scanned in the X-axis direction by the electrostatic deflectors 8 and 11.
Secondary electrons emitted from the scanning point of the sample 15 are accelerated by the positive axisymmetric electrode 14, focused by the magnetic lens 12, and deflected in the direction of the secondary electron detector 21 by the E × B separator 9. Is done. By detecting secondary electrons with the secondary electron detector 21, an 8-channel SEM (scanning electron microscope) image can be obtained.

  FIG. 3 shows the intensity distribution in the electron beam emission direction when a TaC cathode (transition metal carbide cathode) having an optical axis direction of (100) is used as an electron gun. In the figure, a region 31 is an electron beam emitted from the (310) direction and a region 32 is an electron beam emitted from the (100) direction, and the region has an intensity of 60% or more. Since the intensity of the electron beam from the (100) direction is relatively weak and the region where the intensity is 60% or more is narrow, the beam forming aperture 33 is formed on the forming plate so as to use the electron beam at the center. On the other hand, since the intensity of the electron beam from the (310) orientation is strong and the region where the intensity is 60% or more is wide, a sufficiently strong electron beam can be obtained even at a position off the center. Therefore, the beam shaping openings 33 can be provided at positions where the intervals between all eight electron beams projected onto the Y axis are equal.

  Next, a second embodiment of the present invention will be described based on FIG. FIG. 4 shows an overall view of the electron beam apparatus 51 according to the present embodiment. The electron beam device 51 is provided with an electron gun 52. This electron gun 52 is commercially available, and a ZrO / W cathode 52a is welded to a heater 52b and positioned at the opening of the Schottky shield 52c. An extraction electrode 55 a is provided on the downstream side of the electron gun 52. The extraction electrode 55a has conventionally been formed with a hole of 0.6 mmΦ, but in the present invention, a hole with a diameter of 0.8 to 1.2 mmΦ larger than the conventional one is provided, and an electron beam emitted to the outside of the optical axis OA is provided to the extraction electrode 55a. It is not shielded by 55a.

  Further, a central electrode 55b and an anode electrode 55c are provided on the downstream side of the extraction electrode 55a, and these constitute an electrostatic lens 55. The electrostatic lens 55 functions so that the electron beam emitted to the outside of the optical axis forms a crossover in the NA opening 58a of the NA opening plate 58. The electrostatic lens 55 is an acceleration lens in which a positive voltage is applied to the central electrode 55b in order to focus an electron beam emitted at a large angle with respect to the optical axis OA with little aberration. Further, the thickness of the central electrode 55a in the optical axis direction is as thick as 3 mm or more so that a necessary focusing force can be obtained with a small voltage so that no discharge occurs. Incidentally, it was confirmed by simulation that the electron beam is sufficiently focused if the thickness is 2 mm or more. Also, the aberration is smaller when a positive voltage is applied than when a negative voltage is applied.

The central electrode 55b has an opening through which an electron beam passes. In order to form a crossover with small spherical aberration in the NA opening 58a, the shape of the opening of the central electrode 55b is ZrO / W cathode 52a side. The inner diameter is small, and the inner diameter is larger on the NA aperture plate 58 side. Incidentally, it has been found that the aberration is small when the central electrode 55b is grounded and the inner diameter of the central electrode 55b on the electron gun 52 side is approximately the same as the inner diameter of the extraction electrode 55a. This is because the electrode becomes small in a place where the trajectory of the electron is focused by the lens and passes near the optical axis, and the aberration becomes small because the trajectory and the electrode are not so close.
Further, a beam shaping aperture plate 57 having four beam shaping apertures 57a (only two are shown in the figure) is provided immediately downstream of the electrostatic lens 55. Each beam shaping opening 57a has a diameter of 50 μm, has a small vacuum conductance, and also functions as an orifice.

  The electron beam that has passed through the four beam shaping openings 57 a is reduced by the reduction lens 59, further reduced by the objective lens electromagnetic lens 62, and reduced to about 1/2000 on the sample 65. On the sample 65, two-dimensional raster scanning is performed by the deflector 60 and the electrostatic deflector of the E × B separator 61 to form an SEM image. Here, scanning of the electron beam is performed based on a command from the scanning control unit 74. The secondary electrons emitted from the four scanning points on the sample 65 are finely focused by the electrode 63 to which a positive voltage is applied and the objective lens electromagnetic lens 62. The focused secondary electrons form an enlarged image at a position where the secondary electrons pass through the E × B separator 61, and are further enlarged by the electrostatic lenses 66 and 68, and are formed on the aperture plate 70 having four holes. An image is formed. At this time, the secondary electrons are deflected by the alignment deflectors 67 and 69.

  Further, a secondary electron detector 71 having a combination of a scintillator and a photomultiplier is provided behind the aperture plate 70, and secondary electron signals from four electron beams are independently detected and amplified. The amplified secondary electron signal is converted into a digital signal by the A / D converter 72 and sent to the image forming circuit 73. The image forming circuit 73 also receives a scanning signal from the scanning control unit 74 and forms a two-dimensional image. The formed two-dimensional image is stored in the image memory 75, and cell-to-cell or die-to-die comparison is performed by the comparison circuit 76, and pattern defect detection on the sample 65 is performed.

  In the present invention, by using a short focal length lens as the reduction lens 59 and the objective lens electromagnetic lens 62, the distance between the beam shaping aperture plate 57 and the sample 65 can be reduced to 28 cm which is 30 cm or less. For this reason, the space charge effect can be suppressed. In addition, since the electrostatic lens 55 is disposed close to the electron gun 52, the four electron beams emitted to the outside of the optical axis OA can be focused before greatly leaving the optical axis OA, and the low-aberration crossover can be reduced with NA. Since it can be formed in the opening 58a, four electron beams with high luminance can be obtained. Further, since the objective lens is composed of a combination of the objective lens electromagnetic lens 62 and the electrode 63 to which a positive voltage is applied, the aberration of the primary electron beam can be reduced, so that an electron beam of 29 nA with a beam diameter of 25 nmΦ is obtained. A current can be obtained. Furthermore, since the first stage magnifying lens through which the secondary electrons pass can be made low-aberration, the secondary electrons emitted from the sample in ± 90 °, that is, in all directions above the sample are not crosstalked. Can be collected in the secondary electron detector 71.

  Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 5 shows an objective lens 101 used in the electron beam apparatus, FIG. 5 (A) is a plan view, and FIG. 5 (B) is a sectional line PP in FIG. 5 (A). It is sectional drawing. The objective lens 101 is for performing a pattern evaluation on the sample 112 by continuously moving a sample stage (not shown) in the Y-axis direction (second direction), and in the X-axis direction (first direction). Are provided with rectangular thin plate portions 107 and 108 having a longitudinal axis along the axis. In the figure, a part of the length in the longitudinal axis direction is omitted.

  An electron beam passage hole 102 through which the electron beam passes is formed in the upper thin plate portion 107 constituting the first component at a position corresponding to the optical axis OA of the electron beam. In addition, a cylindrical protrusion 103 is formed around the electron beam passage hole 102 and is symmetric with respect to the optical axis OA and directed downward. On the other hand, a predetermined opening is formed at a position corresponding to the above-described protrusion 103 in the lower thin plate portion 108 which is the second component. The diameter of the opening is larger than the outer diameter of the protrusion 103, and a lens gap 104 is formed between the outer peripheral surface of the protrusion 103 and the inner peripheral surface 105 of the opening. At this time, the distance between the square thin plate portions 107 and 108 and the length of the projection 103 are designed so that the position of the lowermost end portion of the protrusion 103 has a predetermined distance from the lower surface of the lower thin plate portion 108 in the Z-axis direction. Has been.

Further, thick plate portions 109 and 111 as predetermined ribs are formed around the thin plate portions 107 and 108, and the thin plate portion 107 is formed in the X-axis direction (the first direction which is the longitudinal axis direction). , 108 is prevented from bending. Between these thick plate portions 109 and 111, there is provided a coil 110 that allows current to flow around the plurality of optical axes OA along a direction perpendicular to the optical axis OA. Reference numeral 120 in the drawing denotes a screw position for fixing the upper magnetic pole and the lower magnetic pole.
In addition, an O-ring holding member 113 that holds the O-ring 14 is provided between the upper and lower thin plate portions 107 and 108, which is formed of a nonmagnetic metal part. The O-ring holding member 113 has a cylindrical or annular shape, and grooves are formed at both upper and lower ends thereof. An O-ring is inserted into this groove and is sandwiched between the thin plate portions 107 and 108. For this reason, the space between the optical axis OA side and the coil 110 side is mutually sealed, and the vacuum on the optical axis OA side can be maintained and the coil 110 and most of the magnetic pole surfaces can be kept at atmospheric pressure.

  A thin plate 106 is provided on the lowermost end portion of the objective lens 101 and on the side facing the sample 112. The thin plate 106 is applied with a positive voltage, can greatly reduce the aberration of primary electrons, and can easily extract secondary electrons emitted from the sample 112.

  Here, although a plurality of electron beams are incident on the objective lens 101, the interval between the optical axes OA is determined by the interval of the electron gun. If the interval between the electron guns is 25 mm, the interval when the optical axis OA is projected in the X-axis direction is 25 / √2 = 17.7 mm. As shown in FIG. 5, the triangle formed by the optical axis distances Lx and Ly in the directions parallel to the X axis and the Y axis, respectively, with the line S connecting the two optical axes as the hypotenuse, This is a case where the optical axis position is set so as to form a right isosceles triangle. When calculated based on the distance 17.7 mm of the optical axis OA when projected onto the X axis, for a wafer with a diameter of 300 mm, 300 / 17.7 = 16.97, and 16 electron beams along the X axis direction. Can be arranged. Here, when the sample is scanned using 16 electron beams, the throughput is increased by 16 times in the simple calculation as compared with the case where one electron beam is used. However, when the sample is a circular wafer or the like, the evaluation region at both end portions in the X-axis direction is narrower than the central portion, so even when one electron beam is used, the evaluation time at the end portion is shorter than that at the central portion. . For this reason, in comparison with the case of evaluating the entire sample, when 16 electron beams are used, the evaluation speed is improved by about 10 times compared with the case of using one electron beam. Further, if there is an optical system at the end, it is not necessary to move the stage greatly along the X-axis direction, so that the size of the sample storage chamber for storing the sample can be reduced.

  Secondary electrons emitted from the sample 112 are attracted by a positive electric field generated by the thin plate 106, focused by a Z-axis direction magnetic field generated by the objective lens 101, and an E × B separator (illustrated) provided on the objective lens 101. As shown by reference numeral 115, the light is deflected toward the secondary optical system provided on the far side of the thick plate portion 109 and detected by a secondary electron detector (not shown). In this embodiment, as shown in FIG. 5, the distances between the optical axes when the optical axes OA are projected onto the X axis are all equal. Therefore, when the evaluation is performed by continuously moving the sample stage in the Y axis direction, It is possible to solve the problem that the same evaluation area is evaluated with electron beams of different optical axes.

  FIG. 6 is a modification of the objective lens 101 described in the third embodiment. The objective lens 151 includes thin plate portions 173, 174, thick plate portions 177, 178, a thick plate portion 177, and a thick plate portion of a ferromagnetic material (low hysteresis material such as supermalloy, permalloy, μ-metal, and electromagnetic soft iron). 178, a multi-optical axis lens composed of a coil 160 provided between 178, deflector groups 171, 180, 181 and a lens intensity correcting electrode 175. In order to reduce the deflection aberration of the electron beam, the deflector groups 171, 180, 181 have a three-stage configuration, and by optimizing the deflection amount and the mutual rotation angle by simulation, it is possible to increase the aberration in a wide area. Can be deflected.

  Further, due to the processing accuracy of the openings 179 and 172 of the objective lens 151, the objective lens 151 has irregular focal lengths for each optical axis OA. In order to correct this irregularity, the lens strength correcting electrode 175 is made of ceramics. Independent voltage can be applied to each optical axis OA. The deflection coils 171 and 181 each have a saddle type coil wound in an angle range of about 120 °, or an X-axis direction deflection coil 182 and a Y-axis direction deflection coil 183, respectively. Reference numeral 184 in the figure denotes a screw position for fixing the upper magnetic pole and the lower magnetic pole.

  Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 7 shows the objective lens 201 of the present embodiment, and is a cross-sectional view of the objective lens 201 cut along a plane including the optical axis OA. An electron gun (not shown) is provided above the figure, and an electron beam emitted from the electron gun is focused on the surface of the sample 202 by the objective lens 201 through the optical axis. The objective lens 201 has a structure in which the excitation coil 210 is surrounded by the inner electrode 203, the outer electrode 204, and the magnetic circuit 211, and is formed so that the lens gap 206 is opened toward the sample 202 side.

  The objective lens 201 is different from the conventional objective lens in that the cross-sectional shape of the lens gap 206 is not parallel to the optical axis OA, and has a shape like a truncated cone having a small radius on the sample 202 side and a large radius on the electron gun side. Have. The simulation shows that the use of such a truncated cone shape reduces the AT (ampere-turn) number of the excitation current for obtaining the focusing condition to about half that of the lens gap parallel to the optical axis. It was confirmed by.

Further, conventionally, the density of magnetic flux passing through each magnetic pole becomes too large at the portion where the inner magnetic pole 203 and the outer magnetic pole 204 face each other (the hatched portion in the figure), and is close to the saturation magnetic flux density of the material. The problem was solved as follows. That is, the hatching portion 207 of the inner magnetic pole 203 has a high magnetic flux density on the electron gun side, and the hatching portion 208 of the outer magnetic pole 204 has a high magnetic flux density on the sample 202 side. When the hatched portion 107 of the inner magnetic pole 203 is cut along a plane perpendicular to the optical axis, the cross-sectional area becomes larger on the electron gun side, so that the saturation problem is solved. At the same time, in the hatched portion 208 of the outer magnetic pole 204, as shown by the hatched portion 209, saturation of the magnetic flux was avoided by slightly increasing the thickness. As a result, it was confirmed by simulation that the electron beam can be narrowed down even when a high voltage is applied to the electrode 215. Further, the half values θ ₁ and θ ₂ of the apex angle of the cone are values corresponding to the inner magnetic pole and the outer magnetic pole, respectively, but when both θ ₁ and θ ₂ are larger than 45 °, the magnetic flux density of the magnetic pole is small, A material with a low saturation magnetic flux density such as supermalloy could also be used.
Below the outer magnetic pole 204, a spacer 205 is provided for fixing the electrode 215 to the lower surface of the magnetic pole made of the outer magnetic pole 204. As the material of the spacer 205, a slightly conductive ceramic such as SiC is used. The problem of charge-up due to the fact that the surface of the insulator can be seen directly from the electron beam has also been solved.
The objective lens 201 also includes an E × B separator 212 that bends secondary electrons emitted from the sample 202 in the direction of a detector (not shown). The E × B separator 212 includes an electromagnetic deflector 212b. A saddle-shaped coil attached to the outside of the electric deflector 212a, and the core of the outer magnetic body is made common with the inner magnetic pole 203 of the objective lens 201, thereby shifting the axis of the objective lens 201 and each of the deflectors 212a and 212b. Minimized.
When permendur (Co—Fe 50% alloy) is used in the vicinity of the lens gap 206 and permalloy B (Fe—Ni (45%) alloy) is used for the other part of the magnetic circuit, the energy of the electron beam is large. Was able to create the necessary magnetic field.
Next, an embodiment of a semiconductor device manufacturing method using an electron beam apparatus or an objective lens according to the present invention will be described with reference to FIGS.

FIG. 8 is a flowchart showing an embodiment of a semiconductor device manufacturing method using the electron beam apparatus according to the present invention. The manufacturing steps of this embodiment include the following main steps.
(1) Wafer manufacturing step for manufacturing a wafer (or wafer preparation step for preparing a wafer)
(2) Mask manufacturing step for manufacturing a mask used for exposure (or mask preparation step for preparing a mask)
(3) Wafer processing step for performing necessary processing on the wafer (4) Chip assembly step for cutting out the chips formed on the wafer one by one and making them operable (5) Chip inspection step for inspecting the completed chips Each main step described above is further composed of several sub-steps.

Among these main steps, the wafer processing step (3) has a decisive influence on the performance of the semiconductor device. In this step, the designed circuit pattern is sequentially stacked on the wafer to form a large number of chips that operate as a memory or MPU. This wafer processing step includes the following steps.
(A) A thin film forming step for forming a dielectric thin film to be an insulating layer, a wiring portion, or a metal thin film for forming an electrode portion (using CVD or sputtering)
(B) Oxidation step for oxidizing the thin film layer and the wafer substrate (C) Lithography step for forming a resist pattern using a mask (reticle) to selectively process the thin film layer and the wafer substrate, etc. (D) Resist pattern Etching step (eg using dry etching technology) to process thin film layers and substrates according to
(E) Ion / impurity implantation diffusion step (F) Resist stripping step (G) Further, a step of inspecting the processed wafer. The wafer processing step is repeated as many times as necessary to manufacture a semiconductor device that operates as designed. To do.

FIG. 9 is a flowchart showing a lithography step which is the core of the wafer processing step of FIG. This lithography step includes the following steps.
(A) A resist coating step for coating a resist on the wafer on which a circuit pattern is formed in the previous step (b) an exposure step for exposing the resist (c) a development step for developing the exposed resist to obtain a resist pattern (D) An annealing step for stabilizing the developed resist pattern

The semiconductor device manufacturing step, wafer processing step, and lithography step described above are well known and need no further explanation.
When the pattern inspection method according to the present invention is used in the inspection step (G), a fine pattern can be inspected stably with high accuracy, so that the yield of products can be improved and the shipment of defective products can be prevented.

  The present invention can be applied to an electron beam apparatus that can perform pattern evaluation and pattern formation with high throughput by using a plurality of electron beams.

1 is a schematic view showing an electron beam apparatus according to a first embodiment of the present invention. It is a top view which shows the beam shaping opening and electron beam irradiation area | region disclosed in FIG. It is a top view which shows the beam shaping opening at the time of using the transition metal carbide cathode for an electron gun, and an electron beam irradiation area | region. It is the schematic which shows the electron beam apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the objective lens which concerns on the 3rd Embodiment of this invention, FIG. 5 (A) shows a top view and FIG. 5 (B) shows sectional drawing. It is a figure which shows the modification of the objective lens which concerns on the 3rd Embodiment of this invention, FIG. 6 (A) shows a top view, FIG.6 (B) shows sectional drawing. It is sectional drawing which shows the objective lens which concerns on the 4th Embodiment of this invention. 3 is a flowchart showing an embodiment of a method for manufacturing a semiconductor device according to the present invention. FIG. 9 is a flowchart showing a lithography step that forms the core of the wafer processing step disclosed in FIG. 8. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electron beam apparatus 2 Electron gun 2a Cathode 2d Electron gun chamber 4 Anode 5 Rotation control lens 6 NA aperture plate 6a NA aperture 7 Reduction lens 9 E × B separator 12 Magnetic lens (objective lens)
DESCRIPTION OF SYMBOLS 13 Lens gap 14 Axisymmetric electrode 15 Sample 19 Molding plate 19a, 19b Beam shaping | molding opening 20 Area | region where electron beam intensity is more than predetermined 31 Area | region which is an emitted electron beam from (100) azimuth | direction, and intensity | strength is 60% or more 32 (310) An electron beam emitted from an orientation and having an intensity of 60% or more 51 Electron beam device 52 Electron gun 52 b Cathode 55 a Extraction electrode 55 b Central electrode 55 c Anode electrode 57 Beam shaping aperture plate 57 a Beam shaping aperture 58 NA Aperture plate 58a NA aperture 59 Reduction lens 61 E × B separator 62 Electromagnetic lens for objective lens 63 Electrode 65 Sample 66, 68 Electrostatic lens 67, 69 Deflector 70 Aperture plate 71 Secondary electron detector 72 A / D converter 73 Image forming circuit 75 Image memory 76 Comparison circuit 101 Objective lens 102 Electron beam Hole 103 Protrusion 104 Lens gap 105 Opening inner wall surface 106 Thin plate 107, 108 Thin plate portion 109, 111 Thick plate portion 110 Coil 112 Sample 113 O ring holding member 114 O ring 151 Objective lens 160 Coil 171, 180, 181 Deflector 172, 176 , 179 Opening 173, 174 Thin plate portion 175 Lens strength correction electrode 177, 178 Thick plate portion 182 X-axis direction deflection coil 183 Y-axis direction deflection coil 201 Objective lens 203 Inner electrode 204 Outer electrode 205 Spacer 206 Lens gap 207, 288, 209 Hatching portion 210 Excitation coil 211 Magnetic circuit 212 E × B separator 215 Electrode OA Optical axis

Claims (13)

In electron beam equipment,
An electron gun that emits an electron beam from a ZrO / W cathode or a transition metal carbide cathode, and an electron optical system that focuses and scans the electron beam emitted from the electron gun in an off-axis direction on the sample;
An electron beam apparatus characterized in that an electromagnetic lens is provided between the electron gun and the sample, and the amount of rotation of the electron beam around the optical axis is adjusted using the electromagnetic lens. In electron beam equipment,
An electron gun that emits an electron beam from a ZrO / W cathode or a transition metal carbide cathode, and an electron optical system that focuses and scans the electron beam emitted from the electron gun in an off-axis direction on the sample;
An electron beam apparatus comprising: a shaped aperture plate that forms 5 to 8 electron beams based on electron beams emitted from the electron gun in a direction off the optical axis. In electron beam equipment,
An electron gun that emits an electron beam from a ZrO / W cathode or a transition metal carbide cathode, and an electrostatic lens that focuses the electron beam emitted from the electron gun in an off-axis direction, An electron beam apparatus, wherein the electron beam apparatus is provided near a cathode and applies a positive voltage to irradiate the NA aperture of the NA aperture plate with the electron beam.   4. The electron beam apparatus according to claim 3, wherein the electrostatic lens has a structure in which three electrodes are superposed, and a thickness of a central electrode of the three electrodes is 2 mm or more.   The electron beam apparatus according to claim 4, wherein the opening formed in the central electrode has an inner diameter on the cathode side smaller than an inner diameter on the NA opening plate side. A thin plate portion made of a ferromagnetic material and having a longitudinal axis in the first direction and a thick plate portion having a rib structure surrounding the thin plate portion, and a plurality of the plate portions at positions corresponding to the optical axis of the electron beam. A first part having a pipe-like protrusion;
A thin plate portion made of a ferromagnetic material having a longitudinal axis in the first direction and a thick plate portion having a rib structure surrounding the thin plate portion, and a plurality of the plate portions at positions corresponding to the optical axis of the electron beam. A second part formed with an opening of
The first component and the second component are provided between the thick plate portions of each component generated when the first component and the second component are combined with a portion corresponding to each optical axis in common with a predetermined gap, and each light A coil wound along a direction perpendicular to the axis;
An objective lens comprising:   The distance between the thin plate portions of the first and second parts and the pipe-like projection are formed so that a lens gap is formed toward the sample side where a magnetic field line generated when a current is passed through the coil is exposed to the outside of the ferromagnetic material. The objective lens according to claim 6, wherein the relationship with the length in the optical axis direction is designed.   7. The pattern evaluation or pattern drawing of a sample is performed by scanning an electron beam in the first direction while continuously moving the sample stage in a second direction perpendicular to the first direction. Or the objective lens of 7. In the objective lens,
The objective lens is for focusing an electron beam from an electron gun on a sample,
In the objective lens, an exciting coil is surrounded by an inner magnetic pole near the optical axis of the electron beam, an outer magnetic pole disposed outside the inner magnetic pole, and a magnetic circuit connected between the inner magnetic pole and the outer magnetic pole. Having a structured
A lens gap formed between the inner magnetic pole and the outer magnetic pole opens to the sample side, and the inner magnetic pole and the outer magnetic pole have a truncated cone shape that gradually spreads from the sample side toward the electron gun side. An objective lens comprising the objective lens.   The objective lens according to claim 9, wherein an axially symmetric electrode to which a positive voltage is applied is provided between the objective lens and the sample.   The objective lens according to claim 9, wherein an E × B separator is provided inside the inner magnetic pole.   A device manufacturing method comprising performing pattern evaluation or pattern formation using the electron beam apparatus according to claim 1.   A device manufacturing method, wherein pattern evaluation or pattern formation is performed using an electron beam apparatus comprising the objective lens according to claim 6.

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