JP2013149751A - Charged particle beam lens - Google Patents

Abstract

An object of the present invention is to provide a charged particle beam lens having improved pressure resistance by suppressing the occurrence of creeping discharge at the periphery of the lens.
A charged particle beam lens includes a plate-like anode, a plate-like cathode, and an insulator disposed between the anode and the cathode. The insulator 13, the anode 11, and the cathode 12 each have one or more beam passage portions 14 through which a charged beam passes. Around the beam passage portion 14, the outer peripheral side surface a of the anode 11 is the outermost surface c and the insulator 13. The cathode 12 is disposed on the inner side closer to the beam passing portion 14 than the outer peripheral side surface b of the cathode 12.
[Selection] Figure 1

Description

The present invention belongs to a technical field of a charged particle beam optical system used in an apparatus using a charged particle beam such as an electron beam, and particularly relates to a charged particle beam optical system used in an exposure apparatus or the like.

In the production of semiconductor devices, the electron beam exposure technique is a promising candidate for lithography that enables fine pattern exposure of 0.1 μm or less. In these apparatuses, an electro-optical element for controlling the optical characteristics of the electron beam is used. In particular, the electron lens includes an electromagnetic type and an electrostatic type, and the electrostatic type is easy to configure and advantageous for miniaturization as compared with the electromagnetic type because it is not necessary to provide a coil core. In addition, among electron beam exposure techniques, a multi-beam system that simultaneously draws a pattern with a plurality of electron beams without using a mask has been proposed. The number of beams is determined by the number of electron lens arrays that can be arranged inside the multi-beam type exposure apparatus, and is a major factor in determining the throughput. Therefore, in recent years, higher arrangement density has been demanded.

An electrostatic charged particle lens is required to have insulation (pressure resistance) in order to apply a voltage between electrodes. As a proposal for improving the withstand voltage of the charged particle beam lens, an insulating portion is disposed between a portion of the substrate having a voltage application portion that contacts the inter-substrate insulator and the voltage application portion, and the voltage application portion and the insulator are arranged. Is electrically isolated (insulated) (see Patent Document 1). In fields other than charged particle beams, a proposal has been made to reduce electric field concentration at the triple point on the anode side and suppress discharge by placing a metal film between the anode and the insulator at the thermal anchor of the superconducting device. Yes (see Patent Document 2).

JP 2005-57110 A JP 2004-165368 A

In the above-described technical situation, with a further increase in throughput of the exposure apparatus and a further definition of the exposure pattern, a higher electric field has been required for the charged particle beam lens. However, when the configuration described in Patent Document 1 is used in such a high electric field, the withstand voltage is insufficient, and there is a possibility of discharging. It has been found that this discharge is caused not by the triple point on the anode side but the triple point on the cathode side, which is disclosed in Patent Document 2 above. The mechanism is as follows.

An electrostatic charged particle beam lens has a structure in which electrodes are stacked via an insulator, and the boundary between the vacuum region, the insulator, and the electrode is a triple point. When an electric field is applied between the electrodes, electrons are emitted from the triple point due to the concentration of the electric field, and the electrons hit the surface of the insulator to emit secondary electrons. As a result, the insulator surface is positively charged, further strengthening the electric field near the triple point and increasing the field emission electrons. Such positive feedback eventually causes a secondary electron avalanche phenomenon on the insulator surface, leading to discharge.

Furthermore, with the miniaturization of charged particle beam lenses, more delicate positioning and handling have been required during lens assembly. Since the neighboring spacers through which the electron beam passes are aligned in particular detail so as not to affect the electron beam trajectory, manufacturing tolerances must be absorbed primarily at the periphery. Although this peripheral portion does not affect the electron beam trajectory, an electric field similar to that in the vicinity of the electron beam is applied. Therefore, if there is a positional deviation, the electric field tends to concentrate in shape and may cause discharge. In addition, the peripheral portion may be flawed or chipped due to handling during assembly or position adjustment, and these may also promote discharge due to shape electric field concentration. That is, there is a case where the discharge in the peripheral part becomes a problem rather than the vicinity where the electron beam passes, and further improvement has been desired regarding the pressure resistance in the vicinity of the cathode side triple point in the peripheral part of the lens.

In view of the above problems, the charged particle beam lens of the present invention includes at least one plate-like anode, at least one plate-like cathode, and at least one insulator disposed between the anode and the cathode, Have The insulator, the anode, and the cathode each have one or more beam passing portions through which a charged beam passes, and around the beam passing portion, the outer peripheral side surface of the anode is the outermost surface of the insulator and the It arrange | positions from the outer peripheral side surface of a cathode at the inner side near the said beam passage part.

According to the charged particle beam lens of the present invention, since the outer peripheral side surface of the anode around the beam passing portion is arranged as described above, the electric field concentration at the cathode-side triple point in the lens peripheral portion is alleviated. Further, the surface on the anode side of the insulator also becomes the creeping surface of the insulating material, and it is possible to extend the creeping distance of the insulating material. Due to these two effects, it is possible to suppress the occurrence of creeping discharge at the lens peripheral portion where a structure in which an electric field concentrates, such as misalignment, scratches, and chips during assembly.

The figure which shows the structure schematic cross section of the charged particle beam lens in 1st Embodiment, a structure schematic cross section of an enlarged part, and an Einzel type | mold lens. The figure which shows the structure schematic cross section of the charged particle beam lens in 2nd Embodiment, an expansion part, and the structure schematic cross section of an Einzel type | mold lens. The figure which shows the structure schematic cross section of the charged particle beam lens in 3rd Embodiment, and the structure schematic cross section of an Einzel type | mold lens. The figure which shows the structure schematic cross section of the charged particle beam lens in 4th Embodiment, and the structure schematic cross section of an Einzel type | mold lens.

A feature of the charged particle beam lens of the present invention is that the pressure resistance of the charged particle beam lens is improved by disposing the outer peripheral side surface of the anode inside the outermost side surface of the insulator and the outer peripheral side surface of the cathode. Based on this concept, the charged particle beam lens of the present invention has a basic configuration as described in the means for solving the above-mentioned problems.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The first to fourth embodiments of the present invention will be described with reference to FIGS. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in these embodiments are not intended to limit the scope of the present invention only to those unless otherwise specified. Absent. In the present invention, the cathode includes a conductor having substantially the same potential as the electrode on the low potential side.

(First embodiment)
FIG. 1A is a schematic cross-sectional view of the configuration of the charged particle beam lens of the first embodiment, and FIG. 1B is a partially enlarged view of an area A surrounded by a broken line in FIG. In FIG. 1A, 11 is a plate-like anode, and 12 is a plate-like cathode, each of which is made of metal, various alloys, various semiconductors, or the like. Reference numeral 13 denotes a plate-like insulator made of various types of glass or various types of ceramics. At least the anode 11 is disposed on one surface of the insulator 13, and at least the cathode 12 is disposed on the surface opposite to the anode 11. The anode 11 and the cathode 12 are electrically insulated via an insulator 13. Each of the cathode 12, the anode 11, and the insulator 13 has at least one through-hole (beam passage portion) 14 through which a charged beam emitted from a light source (not shown) passes. The outer peripheral side surface a of the anode 11 is disposed on the inner side (side closer to the through hole 14) than the outer peripheral side surface b of the cathode 12 and the outermost side surface c of the insulator 13. Here, for example, when a negative voltage is applied to the cathode 12 and the anode 11 is set to the ground potential, it functions as an immersion lens.

In the above configuration, the insulator creepage distance 15 is longer than the thickness of the insulator 13 as shown in FIG. Further, the plurality of curved broken lines shown in FIG. 1B are equipotential lines having these shapes, and the electric field applied to the cathode-side triple point 16 in the peripheral portion of the lens away from the through hole 14 is relaxed. I understand that. As described above, the creepage distance 15 can be ensured to be equal to or larger than the thickness of the insulator 13 and the electric field at the cathode side triple point 16 can be relaxed, whereby the pressure resistance can be remarkably improved.

FIG. 1C is a diagram illustrating the configuration of the Einzel lens according to the first embodiment. In FIG. 1, 11 is an anode, 12 is a cathode, 13 is an insulator, and 14 is a charged particle emitted from a light source. Is a through-hole. The anode 11 is a disk-like single crystal silicon substrate having a thickness of 100 μm and a diameter of 98 mm that is polished on both sides. The cathode 12 is a disk-like single crystal silicon substrate having a thickness of 100 μm and a diameter of 101.6 mm, which is polished on both sides. The insulator 13 is a disc-shaped borosilicate glass having a thickness of 400 μm and a diameter of 101.6 mm. The opening diameter of the through hole 14 is 30 μm for the anode 11 and the cathode 12 and 4 mm for the insulator 13. Here, the anode 11 and the cathode 12 are disposed with the insulator 13 interposed therebetween and the central axis of the through hole 14 being aligned.

Next, a manufacturing method of the first embodiment of the Einzel lens shown in FIG. In the anode 11 and the cathode 12, a through hole 14 is formed in a silicon wafer by high-precision photolithography and dry etching. In the insulator 13, through holes 14 are formed by sandblasting, and microcracks and burrs on the processed surface are processed by wet etching and surface polishing. Although one through hole is shown in the illustrated example, a plurality of through holes may be formed. Next, the two anodes 11, the one cathode 12, and the two insulators 13 that have been subjected to these processes are arranged in the order of the anode 11, the insulator 13, the cathode 12, the insulator 13, and the anode 11. Join together. Thus, the configuration shown in FIG. Bonding was performed using a heat-resistant silicone adhesive. With this configuration, the electric field at the cathode-side triple point in the periphery of the lens away from the through hole 14 is relaxed, and the creepage distance of the insulator is increased, so that the pressure resistance is improved. Actually, when -3.7 kV was applied to the cathode 12 and the two anodes 11 were set to the ground potential and the electron beam was passed through the through hole 14, no discharge was observed, and the desired lens action was stably prolonged. I was able to keep it over time. Thus, it was confirmed that a highly reliable electron lens can be configured according to this embodiment.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIG. FIG. 2A is a schematic sectional view of a charged particle beam lens according to the second embodiment of the present invention, and FIG. 2B is an enlarged view of an area B surrounded by a broken line in FIG. As shown in FIG. 2A, in the second embodiment, a conductive film 27 is formed on a part of the outermost surface of the insulator 13 in the first embodiment. The conductive film 27 is electrically connected to the cathode 12 and is spaced apart from the anode 11. The conductive film 27 is made of metal, various alloys, various semiconductors, or the like. As charged particle beam lenses become smaller and more precise, more precise alignment and handling are required for lens assembly. That is, since each material is small and thin, it tends to be lost during handling. If there are scratches, chippings, or assembly deviations in the lens periphery, the pressure resistance may be reduced due to the concentration of the electric field and the change in the electric field strength. With the configuration shown in FIG. 2 (b), even if there is a flaw d, chipping e, assembly deviation f, etc. near the cathode side triple point in the periphery of the lens, these portions are at the same potential, so the electric field Is less likely to cause creeping discharge.

The present embodiment can be manufactured by the same material and dimensions and manufacturing method as those of the first embodiment except for the portions described below. FIG. 2C is a drawing showing an Einzel lens in the second embodiment, in which 27 is a conductive film. The conductive film 27 is platinum, the film thickness is 500 nm, the film width (length in the vertical direction in FIG. 2C) is 300 μm, and covers all the triple points on the cathode side of the lens periphery centering on the outer periphery of the cathode 12. ing. When the conductive film 27 is formed by the lift-off process of the sputtered film after forming and bonding the through holes in the same manner as in the first embodiment, the configuration shown in FIG. With this configuration, the occurrence of creeping discharge can be suppressed because no potential difference is given to sites such as scratches, chips, and assembly misalignments in the vicinity of the cathode side triple point in the lens periphery. When −3.7 kV was actually applied to the cathode 12 and the two anodes 11 were set to the ground potential and the electron beam was passed through the through hole 14, no discharge was observed, and the desired lens action was more stable. I was able to keep it for a long time. Thus, it was confirmed that a more reliable electron lens can be configured according to this embodiment.

(Third embodiment)
Next, a third embodiment will be described with reference to FIG. FIG. 3A is a schematic sectional view of a charged particle beam lens according to the third embodiment of the present invention. As shown in FIG. 3A, in the third embodiment, the conductive film on the outermost surface of the insulator 13 in the second embodiment has a conductive film 37 extending to the same plane as the surface on which the anode 11 is provided. It has become. By adopting the configuration of the third embodiment, the insulator creeping surface 36 can be obtained only on the plane of the insulator 13 which has excellent flatness and hardly has a singular point, and the pressure resistance performance is further improved. Although the distance between the insulator creepage surfaces 36 in the third embodiment is slightly shorter than that in the second embodiment, the withstand voltage is improved because the creeping surface where the electric field is applied is excellent in flatness. This is thought to be due to the large effect of the composition.

The present embodiment can be manufactured by the same material and dimensions and manufacturing method as those of the first embodiment except for the portions described below. FIG. 3B is a drawing showing an Einzel type lens in the third embodiment, in which 37 is a conductive film. The conductive film 37 is platinum, and has a film thickness of 500 nm. The conductive film 37 is formed on the cathode 12 and the outermost surfaces of the two insulators 13 and on the anode surfaces of the two insulators 13 from the outermost surface to the inner side of 200 μm. Covering. When the conductive film 37 is formed by the lift-off process of the sputtered film after the through hole 14 is formed and bonded as in the first embodiment, the configuration shown in FIG. 3B is obtained. With this configuration, the surface to which an electric field is applied in the lens peripheral portion is only the main plane of the plate-like anode 11 as shown in the insulator creepage surface of FIG. This surface is generally excellent in flatness, and is a place where scratches, chips, etc. during handling are unlikely to occur. That is, the possibility of having a singular point where the electric field concentrates on the creeping surface of the insulator is reduced, and the occurrence of creeping discharge can be suppressed. When −3.7 kV was actually applied to the cathode 12 and the two anodes 11 were set to the ground potential and the electron beam was passed through the through hole 14, no discharge was observed, and the desired lens action was more stable. I was able to keep it for a long time. Thus, it was confirmed that a more reliable electron lens can be configured according to this embodiment.

(Fourth embodiment)
Next, a fourth embodiment will be described with reference to FIG. FIG. 4A is a schematic sectional view of a charged particle beam lens according to the fourth embodiment of the present invention. As shown in FIG. 4A, in the fourth embodiment, the creeping surface of the insulator in the third embodiment is covered with a high resistance film 48. The high resistance film 48 is formed using a metal oxide, metal nitride, or semiconductor as a base material. With the configuration as in the fourth embodiment, even if electrons collide with the separation portion of the anode 11 and the conductive film 37, that is, the film formation portion of the high resistance film 48, the charge resistance is improved. The configuration like the high resistance film in the fourth embodiment may be applied to the first and second embodiments. In other words, in the second embodiment, the separated portion of the anode 11 and the conductive film 27 is covered with a high resistance film, and in the first embodiment, part or all of the peripheral surface of the insulator is covered with the high resistance film. You may make it the structure.

The present embodiment can be manufactured by the same material / dimension and manufacturing method as those of the third embodiment except for the portions described below. FIG. 4B is a drawing showing an Einzel lens in the fourth embodiment, in which 48 is a high resistance film. The high resistance film 48 is obtained by adding tungsten to aluminum oxide, has a volume resistivity of 1 × 10 ¹¹ [Ω · cm], a film thickness of 300 nm, and covers the separated portion of the anode 11 and the conductive film 37. When the through hole 14 is formed and bonded as in the third embodiment, the conductive film 37 is formed, and the high resistance film 48 is formed by the lift-off process of the sputtered film, the configuration shown in FIG. It becomes. With this configuration, even if electrons collide with the separated portion between the anode 11 and the conductive film 37, charging is not performed, so that the occurrence of creeping discharge can be suppressed. Actually, when -3.7 kV was applied to the cathode 12 and the two anodes 11 were set to the ground potential and the electron beam was passed through the through hole 14, no discharge was observed, and the desired lens action was stably achieved. I could keep it for a longer time. Thus, it was confirmed that a more reliable electron lens can be configured according to this embodiment.

11 .. Anode, 12 .. Cathode, 13 .. Insulator, 14 .. Through hole (beam passage part), a .. Anode outer side surface, b .. Cathode outer side surface, c.

Claims (4)

At least one plate-like anode, at least one plate-like cathode, and at least one insulator disposed between the anode and the cathode, wherein the insulator, the anode, and the cathode are charged. A charged particle beam lens having one or more beam passing portions for passing a beam,
Around the beam passage portion, the outer peripheral side surface of the anode is disposed closer to the inner side of the beam passage portion than the outermost side surface of the insulator and the outer peripheral side surface of the cathode. Line lens. The conductive film is formed on at least the outermost surface of the insulator, the conductive film is electrically connected to at least the cathode, and the conductive film and the anode are spaced apart. 2. The charged particle beam lens according to 1. The charged particle beam lens according to claim 2, wherein the conductive film extends to the same plane as the surface of the insulator having the anode. 4. The charged particle beam lens according to claim 1, wherein a separation portion between the cathode and the anode or the conductive film and the anode is covered with a high resistance film. 5.

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