JP2014143393A - Electron beam lithography apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that unintended irradiation with reflection electrons or secondary electrons cannot be prevented completely, in the improvement of an electron beam lithography apparatus including an antireflection mechanism for preventing the long-distance photosensitive action (unnecessary sensitization) incident to the reflection electrons emitted from the sample surface by irradiation with an electron beam or re-incidence of secondary electrons to the sample side.SOLUTION: An antireflection mechanism of a plate body having an antireflection structure provided, on the surface facing a sample, with a plurality of cuts having V-shaped cross section continuously comprises an antireflection structure for attenuating and absorbing the reflection electrons or secondary electrons, by reflecting the reflection electrons or secondary electrons emitted from the sample surface in each V-shaped cut a plurality of times.

Description

  The present invention relates to an antireflection mechanism installed in an electron beam drawing apparatus used for drawing a fine pattern of a semiconductor element, and more particularly to improve the antireflection structure installed on the objective lens side of a sample surface. The present invention relates to an electron beam drawing apparatus.

  In an electron beam drawing apparatus, a resist coated on a sample such as a mask or a wafer is irradiated with an electron beam through an objective lens, and the electron beam is scanned according to a pattern. At this time, the reflected electrons reflected or scattered on the sample surface are reflected again on the lower surface of the objective lens, and the re-reflected electrons return to the sample surface.

  The resist is also exposed to the re-reflected electrons. That is, as shown in FIG. 9, a resist on the sample surface other than the place where the electron beam is incident by the re-reflected electrons is exposed, so that a so-called long-distance photosensitivity effect is produced, thereby causing a reduction in drawing accuracy. .

  Electron beam drawing with an antireflection mechanism at the position on the beam incident side facing the sample surface for the purpose of preventing re-incidence of reflected electrons or secondary electrons emitted from the sample surface by electron beam irradiation to the sample side Prior arts exemplified below are known as proposals related to the apparatus.

  (1) A configuration in which a mirror surface to which reflected electrons of an electron beam irradiated onto a drawing sample hit is covered with a material composed of a material whose main constituent element is an element having an atomic number of 13 or less (Patent Document 1) ).

(2) A plurality of thin plates having a plurality of openings are stacked, and each opening is connected to form a hole for suppressing the emission of reflected electrons or secondary electrons. Electron beam drawing characterized in that a concave portion is provided in the antireflection mechanism so that the lowermost part of a fixing member for fixing to the lower part of the objective lens is positioned on the objective lens side with respect to the lower surface of the antireflection mechanism Device (Patent Document 2).
Also in Patent Document 2, it is said that it is preferable to use a substance having a small atomic number Z in order to reduce re-reflection of electrons, and a thin plate is directly made by machining or etching a material having a small atomic number such as C or Be. Examples include a processed structure or a structure in which Cu, Al, or the like is processed by machining or etching, and then a surface having a small atomic number such as Be or C is coated by vapor deposition, sputtering, plating, or the like. .

However, as the required drawing accuracy increases, the effect of preventing re-reflection becomes insufficient only by using a material having a low atomic number. The following documents are known as proposals for improving the structure of the opening instead of the material of the antireflection mechanism.
(3) The antireflection mechanism includes a plate having a plurality of apertures, and the side walls of the apertures are formed so as not to be directly seen from the beam irradiation position on the sample surface. An electron beam drawing apparatus in which a noble metal catalyst is supported on a portion of the sample surface that cannot be directly seen from the beam irradiation position (Patent Document 3).
In Patent Document 3, an antireflection plate having a honeycomb structure is provided as a plate body of the antireflection mechanism so that the side wall of the hole portion cannot be seen from the beam irradiation position on the sample surface. A structure in which a noble metal catalyst having a catalytic action is supported on the side wall and the back surface of the hole is employed.

JP 60-53021 A JP-A-11-251223 JP 2000-123776 A

  However, in the antireflection mechanism of Patent Document 3, since the holes are opened vertically, the reflected electrons or secondary electrons incident vertically cannot be sufficiently absorbed. Further, although this antireflection plate is used in the current drawing apparatus, there is a problem that unintentional irradiation by reflected electrons or secondary electrons cannot be prevented.

  Therefore, the present invention is intended to solve such problems of the prior art, and by reflecting the surface structure of the antireflection plate, the reflection electrons or secondary electrons are sufficiently attenuated and then absorbed. An object of the present invention is to propose an electron beam drawing apparatus including an antireflection mechanism having a prevention structure.

In order to achieve the above object in the present invention, an electron beam writing apparatus according to the invention of claim 1 re-reflects reflected electrons or secondary electrons emitted from the sample surface upon irradiation with the electron beam to the sample side. In an electron beam lithography system provided with an antireflection mechanism for preventing
The antireflection mechanism has an antireflection structure in which a plurality of cuts having a V-shaped cross section are continuously provided on a surface of the plate body facing the sample.

  In the electron beam writing apparatus according to the second aspect of the present invention, a plurality of incisions having a V-shaped cross-section are continuously formed concentrically from the center of the plate body to the outer periphery, and the angle θ of the V-shaped incision is 2 × arctan. It has an antireflection mechanism having an angle smaller than (distance A between sample and antireflection mechanism / maximum dimension B of sample).

  An electron beam lithography apparatus according to a third aspect of the present invention is formed with a cross-sectional shape of a hexagonal pyramid-shaped structure arranged in a plurality of honeycombs on the surface side of the sample opposite to the V-shaped incision of the cross-sectional shape, and the V-shaped And an anti-reflection mechanism having an angle θ smaller than 2 × arctan (distance A between sample and anti-reflection mechanism / maximum dimension B of sample).

  The electron beam drawing apparatus according to the invention of claim 4 is characterized in that the plate having the antireflection mechanism is made of a conductor.

  The electron beam writing apparatus according to the invention of claim 5 is characterized in that the surface of the antireflection structure is covered with a material whose main constituent element is an element having an atomic number of 13 or less.

  The electron beam writing apparatus according to the invention of claim 6 is characterized in that the antireflection mechanism is electrically grounded, and the antireflection structure is attached to the lower part of the objective lens facing the sample.

  According to the first aspect of the present invention, the reflected electrons or secondary electrons generated from the sample surface are attenuated and absorbed by providing a V-shaped cut in the antireflection mechanism. Thus, it becomes possible to prevent re-reflection of electrons to the sample surface.

  In the present invention according to claim 2, the angle θ (4a) of the V-shaped cut provided in the antireflection mechanism is 2 × arctan (distance A between the sample and the antireflection mechanism / maximum dimension B of the sample). Thus, it becomes possible to more effectively prevent re-reflection of electrons to the sample surface.

  According to the third aspect of the present invention, the cross-sectional shape is formed in the cross-sectional shape of a hexagonal pyramid structure arranged in a plurality of honeycombs on the sample surface side where the V-shaped cuts face each other, thereby preventing reflection. The area occupied by the structure can be made larger, coupled with the V-shaped cut angle θ being smaller than 2 × arctan (distance A between sample and antireflection mechanism / maximum dimension B of sample), It becomes possible to prevent re-reflection of electrons to the sample surface more effectively.

  In the present invention described in claim 4, the plate body having the antireflection mechanism is made of a conductor, so that the reflected electrons or the secondary electrons from the sample surface are diffused in the antireflection mechanism without being charged. Is possible.

  In the present invention according to claim 5, the surface of the antireflection structure is covered with a material whose main constituent element is an element having an atomic number of 13 or less, so that reflected electrons or secondary electrons are reflected from the sample surface. It becomes possible to absorb with high efficiency on the surface of the prevention mechanism.

  According to the sixth aspect of the present invention, the antireflection mechanism having the antireflection structure is electrically grounded, and the antireflection structure is attached to the lower part of the objective lens facing the sample, whereby the electron beam In the beam irradiation by the drawing apparatus, it is possible to prevent the unintended portion of the sample from being irradiated and to keep the surface of the antireflection mechanism at the ground potential.

It is a cross-sectional schematic diagram which shows an example of the fine structure of the surface of the thin plate for reflection prevention concerning embodiment of this invention. It is a plane schematic diagram which shows the shape of the thin plate which has an antireflection mechanism shown in FIG. It is a cross-sectional schematic diagram of FIG. It is a cross-sectional schematic diagram which shows the fine structure of the antireflection plate by which the hexagonal pyramid whose cross-sectional shape is V shape is arrange | positioned on the surface of the thin plate for antireflection concerning embodiment of this invention in honeycomb form. FIG. 5 is a schematic plan view of FIG. 4. It is a schematic diagram which shows the hexagonal pyramid whose cross-sectional shape in FIG. FIG. 4 is a schematic diagram of an electron traveling path after entering the V-shaped cut in FIG. 1 (FIG. 3). It is a schematic diagram which shows the maximum angle of the V-shaped cut so that the electrons incident on the V-shaped cut do not come out of the cut. It is a schematic diagram for demonstrating the principle of a long-distance interaction.

<Antireflection mechanism>
FIG. 1 is a schematic cross-sectional view showing the fine structure of an antireflection plate according to an embodiment of the present invention.
The reflected electrons or secondary electrons are attenuated by reflecting the reflected electrons or secondary electrons generated from the sample surface multiple times within each V-shaped notch installed in the fine structure of the antireflection mechanism (1a). By absorbing and absorbing, it becomes possible to prevent re-reflection of electrons to the sample surface.

FIG. 2 is a schematic plan view showing an example of the shape of a thin plate constituting the antireflection mechanism (1a) in FIG.
The plate according to claim 1 is a thin plate constituting the antireflection mechanism, and is a plate having a V-shaped notch shown in FIG. 3 which is a sectional view of FIG. Since a plurality of the V-shaped cuts are continuously formed concentrically from the center to the outer periphery of the antireflection structure, reflected electrons or secondary electrons are concentrically formed from the electron beam irradiation position (5a) of the sample. Even if it is scattered, it can be attenuated and absorbed with high efficiency.

  4 shows a hexagonal pyramid structure having a V-shaped cross section shown in FIG. 6 arranged in a honeycomb shape as shown in FIG. 5 on the surface of an anti-reflection thin plate according to the embodiment of the present invention. It is a cross-sectional schematic diagram when the fine structure of the antireflection plate is cut at a plane connecting the hexagonal pyramid peaks 2d as indicated by 2f in FIG. Since the hexagonal pyramid structure is arranged in a honeycomb shape as shown in FIG. 5, the area of the antireflection structure occupying the thin plate can be increased, and a plurality of concentric circles are continuously formed. Reflected electrons or secondary electrons can be attenuated and absorbed with higher efficiency than is possible.

FIG. 7 is a schematic diagram of an electron traveling path after entering the V-shaped cut in FIG. As shown in FIG. 8, the V-shaped angle θ (4a) of the incision is made smaller than 2 × arctan (distance A between the sample and the antireflection mechanism / maximum dimension B of the sample), thereby reducing the V-shaped incision. The incident angle (3b shown in FIG. 7) of the reflected electrons reflected or scattered on the sample surface with respect to each side becomes smaller than 90 °, and the electrons re-reflected to the sample surface once enter the V-shaped cut. Can be reflected within the V-shaped cut and attenuated without exiting.
As shown in the figure, the electrons incident on the V-groove at the angle 3a and emitted at the angle 3b enter the other surface of the V-groove from the next time on at an angle smaller than 3a (= 3b). Reflection is repeated, and it goes to the back of the V-groove while being attenuated.
After repeatedly entering and reflecting with attenuation in the V-groove, it does not come out of the V-groove again while proceeding in the reverse direction from the back of the V-groove, and as a result, incident electrons are absorbed in the V-groove. Therefore, harmful effects due to re-reflection on the sample are prevented.
The sample mentioned here is an object to be irradiated with an electron beam, for example, a blank for a photomask.

<Antireflection plate>
The surface of the antireflection mechanism is covered with a material having a low electron beam reflectivity. An element having an atomic number of 13 or less that can absorb reflected electrons or secondary electrons with high efficiency is preferably used. As the main constituent element on the surface of the antireflection mechanism, for example, beryllium or carbon (graphite) is preferable. These elements are coated on the surface of the antireflection mechanism by plating or coating. The film thickness is preferably about several tens of μm, which is a general film thickness for plating and coating. The film thickness covering the surface of the antireflection mechanism is a value that can be taken depending on the material used, and is not particularly limited as long as a predetermined amount of reflected electrons or secondary electrons can be absorbed.

The antireflection plate is preferably made of a conductor including a metal having a resistivity of about 10 ⁻⁶ Ωcm. For example, iron, copper, and aluminum can be used. In the alloy, copper or aluminum is the main constituent material.
The antireflection plate is made of a conductor, and the surface thereof is made an element having an atomic number of 13 or less as a main constituent material, so that the antireflection plate having an element of an atomic number of 13 or less as a main constituent material can be reflected without making The antireflection mechanism that exhibits the effect of absorbing electrons or secondary electrons can be easily produced.

<Electron beam drawing device>
The antireflection structure of the present embodiment can constitute an antireflection mechanism by adding the antireflection structure alone or other necessary members. When the antireflection mechanism is used in an electron beam drawing apparatus, as shown in FIG. 9, the antireflection structure and the sample are connected so that the antireflection mechanism is grounded and can sufficiently absorb the reflected electrons or secondary electrons. It is preferable to install the sample chamber on the upper surface of the sample chamber (lower surface of the objective lens).

  Examples of the present invention will be specifically described below, but the present invention is not limited thereto.

(Antireflection mechanism)
・ Main components: Iron
・ Resistivity of main constituent material (iron): 1.0 × 10 ⁻⁷ Ωm
・ Surface coating material: Graphite ・ V-shaped digging angle θ: 30 °
・ V-shaped cutting height: 70nm

(Sample structure)
・ Sample size: 6 inches ・ Substrate: Synthetic quartz glass ・ Resist: FEN

  An example in which an electron beam is drawn using the electron beam drawing apparatus having the antireflection structure of the present invention is shown. A halftone blank in which MoSi, Cr, a chemically amplified negative resist was formed on glass was drawn with an electron beam, developed and etched, and then the resist and Cr film were peeled off to produce a pattern. The width of the produced pattern was measured with a scanning electron microscope, and the influence of unintentional irradiation of the sample portion by reflected electrons or secondary electrons was examined.

  For drawing, a plurality of patterns to be measured with a scanning electron microscope are arranged at equal intervals, and a high-density drawing pattern (drawing density 50%) for reproducing a long-distance interaction around the pattern is an arbitrary place. The drawing layout placed in is used.

  In the case where the above-described drawing layout is drawn by an electron beam drawing apparatus using a conventional anti-reflection mechanism, the average value difference in the pattern size of the sparse / dense portion due to the long-range interaction is 8 nm, whereas In the case of using the antireflection mechanism described in Item 2, the influence of unintentional irradiation of the sample portion by reflected electrons or secondary electrons was reduced to 4.5 nm.

  The difference from the first embodiment is that the antireflection mechanism according to claim 3 is used. The hexagonal pyramid structure has a diameter of about 70 nm.

(Antireflection mechanism)
・ Main components: Iron
・ Resistivity of main constituent material (iron): 1.0 × 10 ⁻⁷ Ωm
・ Surface coating material: Graphite ・ V-shaped digging angle θ: 30 °
・ V-shaped cutting height: 70nm

(Sample structure)
・ Sample size: 6 inches ・ Substrate: Synthetic quartz glass ・ Resist: FEN

In an electron beam lithography apparatus using a conventional anti-reflection mechanism, the above-described drawing layout is drawn, while the average value difference in the pattern size of the sparse / dense portion due to the long-range interaction is 8 nm. When the pyramid-shaped structures are arranged in a honeycomb shape, the average value difference of the pattern size of the sparse and dense parts due to the long-range interaction is 3.5 nm, and the unintended irradiation of the sample part by reflected electrons or secondary electrons The impact has decreased.

1a: Antireflection mechanism (conductor)
1b: Antireflection mechanism surface 2a: V-shaped cut (mountain)
2b: V-shaped cut (valley)
2c: Antireflection plate 2d: Concavity and convexity of hexagonal cone (mountain)
2e: Hexagonal concavity and convexity (valley)
2f: Surface 3a having a V-shaped cross section when hexagonal pyramids are arranged in a honeycomb 3a: Electron travel path 3b: Incident angle 4a of reflected electrons reflected or scattered on the sample surface with respect to each side of the V-shaped cut: Antireflection Mechanism 4b: Incident electron 4c: Sample 4d: Incident angle of reflected electrons reflected or scattered on the sample surface with respect to each side of the V-shaped cut: θ: V-shaped cut angle A: Distance between the sample and the antireflection mechanism B: Sample 5a: Electron beam irradiation position 5b: Antireflection mechanism installation portion 5c: Reflected electron or secondary electron 5d: Rereflected electron or reflected secondary electron

Claims (6)

In an electron beam drawing apparatus provided with an antireflection mechanism on the upper surface or side surface of a sample chamber for preventing rereflection of reflected electrons or secondary electrons emitted from the sample surface by electron beam irradiation to the sample side,
The electron beam drawing apparatus, wherein the antireflection mechanism has an antireflection structure in which a plurality of cuts having a V-shaped cross section are continuously provided on a surface of the plate body facing the sample.   A plurality of incisions having a V-shaped cross-section are continuously formed concentrically from the center to the outer periphery of the plate body, and the V-shaped incision angle θ is 2 × arctan (distance A between the sample and the antireflection mechanism A / of the sample 2. The electron beam lithography apparatus according to claim 1, further comprising an antireflection mechanism having an angle smaller than the maximum dimension B).   The cross-sectional shape is a cross-sectional shape of a hexagonal pyramid structure arranged in a plurality of honeycombs on the sample surface side where the V-shaped cuts face each other, and the V-shaped cut angle θ is 2 × arctan (with the sample 2. The electron beam drawing apparatus according to claim 1, further comprising an antireflection mechanism having an angle smaller than the distance A of the antireflection mechanism / the maximum dimension B) of the sample.   4. The electron beam drawing apparatus according to claim 1, wherein the plate having the antireflection mechanism is made of a conductor.   5. The electron beam lithography apparatus according to claim 1, wherein the surface of the antireflection structure is covered with a material whose main constituent element is an element having an atomic number of 13 or less.   6. The electron beam according to claim 1, wherein the antireflection mechanism is electrically grounded, and the antireflection structure is attached to a lower part of the objective lens facing the sample. Drawing device.

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