JPH0745506A - Electron beam lithography method and equipment - Google Patents

Abstract

PURPOSE:To enable writing repetition patterns of a diffraction lattice type, in a region surrounded by an arbitrary sharp outer form, simultaneously and quickly without using an electron gun of high coherency. CONSTITUTION:An electron beam luminous flux which passes an aperture plate AP having an arbitrary shape is subjected to amplitude division into two luminous fluxes which are inclined to each other by a beam splitter CR. The divided two luminous fluxes are defleted to the direction wherein the two luminous fluxes are made to approach with each other by using a biprism EBP, and made to intersect to form an angle on a writing surface P which is conjugate with the aperture plate AP. The divided two aperture images are superimposed on the writing surface, and an interference fringes pattern which is clearly distinguished is written only in the aperture image region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam drawing method and an electron beam drawing apparatus, and more particularly to an electron beam drawing method capable of efficiently drawing a repetitive pattern within a predetermined outer shape by using electron beam interference. The present invention relates to an electron beam drawing apparatus.

[0002]

2. Description of the Related Art Conventionally, in a drawing apparatus using an electron beam, for example, when drawing a fine diffraction grating-like repetitive pattern, drawing is performed by sequentially sweeping an electron beam narrowed down by the drawing apparatus on a drawing surface. To do. However, this method has an essential problem that it takes time to draw the entire drawing surface because each line is drawn in order.

On the other hand, there has been proposed a method of drawing a repetitive pattern in the form of a fine diffraction grating at once by utilizing electron beam interference (Japanese Patent Laid-Open No. 62-140485). This method uses electron beam interference to divide a coherent electron plane wave into wavefronts (the wavefront is divided into two parts with a line perpendicular to the optical axis as a boundary), and the two divided wavefronts are mutually separated by an electron biprism. This is a method of causing interference with a minute angle, and applying the interference pattern to a drawing surface coated with an electron beam resist to simultaneously draw a surface area.

[0004]

However, this method of drawing by utilizing electron beam holography requires that the electron beam has a high spatial coherency,
For that purpose, an expensive field emission type electron gun is required, and even if such an electron gun is used, the coherence between both ends of the beam cross section is not sufficient, and therefore, an interference pattern that can be used for writing. The region in which is obtained is narrower than the beam cross section, and therefore the writing speed cannot be said to be sufficiently high. Moreover, in the interference pattern area obtained by this method, if the outer edge is not clear and it is desired to draw the interference pattern only within a predetermined sharp outline area, another mask or the like must be used. There is also a problem that becomes complicated.

The present invention has been made in view of the above circumstances, and an object thereof is to simultaneously and rapidly draw a diffraction grating-like repetitive pattern in a region surrounded by a sharp outer shape of an arbitrary shape. An object is to provide an electron beam drawing method that does not require the use of an electron gun having high coherence and an electron beam drawing apparatus therefor.

[0006]

According to the electron beam drawing method of the present invention which achieves the above object, an electron beam passing through an aperture having an arbitrary shape is amplitude-divided by a beam splitter into two beams forming an angle with each other. The two split light beams are deflected by a biprism toward each other, intersect at an angle on the drawing surface conjugate with the aperture, and the two divided aperture images are superimposed on the drawing surface. The method is characterized by drawing an interference fringe pattern that is clearly divided by the outline only in the aperture image area.

In this case, it is also possible to sequentially draw a plurality of interference fringe patterns by using openings having different shapes. It is also possible to draw a stripe pattern with a predetermined pitch by relatively moving the drawing surface in the direction of the interference fringe while exposing the interference fringe pattern formed using one opening.

Further, the electron beam drawing apparatus of the present invention comprises a replaceable aperture plate, an electron beam source for irradiating the aperture plate, and an imaging electron optical system for forming an image on the aperture plate on the drawing surface. A beam splitter arranged in the light flux from the aperture plate to the drawing surface and amplitude-splitting the electron beam flux passing through the aperture plate into two optical paths forming an angle with each other, and the two light fluxes split by the beam splitter approach each other. It is characterized by comprising a biprism which is deflected in the direction, intersects at an angle on the drawing surface, and superimposes two divided aperture images on the imaging surface.

In this case, it is realistic that the beam splitter is composed of a single crystal plate for diffracting an electron beam and the biprism is composed of an electron biprism, and the position of the beam splitter can be adjusted in the central axis direction. It is desirable to configure the beam splitter and the biprism so that the deflection angle of the biprism can be adjusted. Further, it is desirable that the beam splitter and the biprism be integrally rotatable about the central axis.

[0010]

In the present invention, the electron beam passing through the aperture having an arbitrary shape forms an angle with the beam splitter.
Amplitude split into two light fluxes, and the two split light fluxes are deflected by a biprism toward each other and intersect at an angle on the drawing surface conjugate with the aperture to draw two split aperture images. By overlapping on the surface, an interference fringe pattern clearly drawn by the outline is drawn only in the aperture image area, so electron waves that interfere with each other on the drawing surface are waves emitted from the same position in the opening. Therefore, it is not necessary to use a highly coherent electron beam source, and it is possible to perform drawing by using a thermionic electron gun instead of the field emission electron gun.
Also, since all the electrons that have passed through the opening can be used for drawing,
The interference fringes are bright and uniform with high intensity, and the drawing speed is significantly improved as compared with the conventional method using electron beam interference. Further, since the outer shape of the interference fringe pattern to be formed is clearly divided and any opening shape can be used, the flexibility of the pattern that can be drawn is improved.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The principles and embodiments of the electron beam drawing method and electron beam drawing apparatus of the present invention will be described below with reference to the drawings.

First, the principle of the drawing method of the present invention will be described using an optical model for simplicity. FIG. 2 is this optical model diagram, in which the aperture plate A and the drawing surface P are arranged in a conjugate manner via the lens L, and the aperture plate A is illuminated by the light from the light source S. Then, in the optical path from the aperture plate A to the drawing surface P, a beam splitter BS having a small relative angle of two light beams divided like a Wollaston prism and a biprism BP such as a Fresnel double prism on the image side of the beam splitter BS. To place. Here, the two light fluxes after passing through the beam splitter BS are 1 and 2, and the images of the aperture plate A formed by these light fluxes are A ₁ and A ₂ , respectively. Also, the luminous flux 1, 2
Are 1 ′ and 2 ′, respectively, after they are bent toward the central axis by the biprism BP.
If the images of the aperture plate A formed by 2 ′ are A ₁ ′ and A ₂ ′, respectively, the images A ₁ ′ and A ₂ ′ are congruent. The relative angle 2θ ₁ of the two light beams ₁ and 2 by the beam splitter BS and the deviation angle θ ₂ of each light beam 1 ′, 2 ′ by the biprism BP are represented by the images A ₁ ′ and A ₂ ′ of the aperture plate A on the drawing surface P.
However, if it is determined that they completely coincide with each other and overlap as shown in the figure, the angle formed by the wavefronts of the two light beams 1 ′ and 2 ′ on the image plane P is 2 (θ ₂ −θ ₁ ) from a simple calculation. Since the light from the light source S has a constant wavelength λ (the wavelength of the electron beam of energy E [eV] is given by (150 / E) ^1/2 ), the angle between this wavelength λ and the wavefront is formed. 2 (θ ₂ −
θ ₁ ) and a constant pitch linear interference fringe (in the case shown, a fringe perpendicular to the paper surface) are images A ₁ ′, A of the aperture plate A.
It is formed into ₂ 'regions. Moreover, this formation area is an inner area which is clearly divided by the outer edges of the images A ₁ ′ and A ₂ ′ of the aperture plate A, and uniform interference fringes are formed within the outer shape. Further, since the lights that interfere with each other on the image plane P are lights emitted from the same position in the aperture of the aperture plate A, the coherence of the light source S does not have to be high, and therefore the interference fringes have uniform brightness. In addition, since all the light emitted from the light source S can be used, an interference fringe with high intensity can be obtained.

Various methods are conceivable for changing the direction, pitch, and phase of the interference fringes. For example, the directions may be obtained by rotating the beam splitter BS and the biprism BP around the central axis. Further, the pitch may be changed by changing the wavelength of the light source S. In the case of an electron beam, if the energy of the electron beam is changed, the exciting current of the lens L must be changed, so that the aperture plate A and the drawing surface P are changed. The position of the beam splitter BS in the direction of the central axis is changed while maintaining the conjugate relation of A, and the deflection angle of the biprism BP is changed so that the images A ₁ 'and A ₂ ' on the drawing surface P coincide with each other. To change its potential. Further, in order to change the phase of the interference fringe, for example, the aperture plate A, the beam splitter BS or the biprism BP may be finely adjusted in the direction perpendicular to the central axis. A deflection system may be provided in the optical path and the deflection angle may be slightly changed.

Further, the shape of the illumination light flux of the aperture plate A is not particularly limited, but as shown in FIG. 2, the diameters of the light fluxes 1 and 2 split by the beam splitter BS are the smallest at the biprism BP position. It is desirable to determine the positions of the light source S and the biprism BP so that as much light flux as possible from the light source S can pass through the aperture of the aperture plate A. As shown in the figure, when the beam splitter BS and the biprism BP are arranged on the image side of the lens L, the aperture plate A is illuminated with a divergent light beam so that the image of the divergence point is formed near the biprism BP. It is desirable to do.

The position of the lens L does not necessarily have to be on the light source S side of the beam splitter BS as shown in the figure, but the beam splitter BS and the biprism BP can be used.
They may be arranged between them, or on the image side of the biprism BP, or at a plurality of positions, and the image forming magnification may be arranged to be any of enlargement, equal magnification, and reduction.

Now, an embodiment of an electron beam drawing apparatus for carrying out the electron beam drawing method of the present invention which can be represented by the above optical model will be described with reference to the sectional view of FIG. In FIG. 1, from the electron beam source side, the electron gun E
G, first condenser lens CL ₁ , replaceable aperture plate AP, second condenser lens CL ₂ , crystal CR for diffracting electron beam, electron biprism EBP, objective lens O
b. Substrate S to be coated with electron beam resist on the surface
B, the substrate SB is placed and the optical axis direction and the direction 2 orthogonal to it
The stage ST is movable along the axis, and the first condenser lens CL ₁ focuses the electron beam emitted from the electron gun EG at a position corresponding to the light source S in FIG. The combined image forming system of ₂ and the objective lens Ob serves as an image forming operation of the lens L in FIG. Then, the height of the stage is adjusted by this composite imaging system so that the image of the aperture plate AP is imaged on the drawing substrate SB. The crystal CR is made of a single crystal plate such as Si or GaAs having no lattice defect. When the thickness of the single crystal plate and the inclination angle with respect to the beam are appropriately selected, the 1st-diffraction beam has the same intensity as that of the 0th-order beam. The condition to be excited is achieved (Fig. 1
, Both beams are deflected, but only the diffracted beam is actually deflected. ), And acts as the beam splitter BS in FIG. Moreover, the electronic biprism EBP functions as the biprism BP of FIG. Then, the relative angle 2θ ₁ of the two beams divided by the crystal CR and the deviation angle θ ₂ of each beam by the electron biprism EBP are set to the aperture of the two beams on the drawing surface P (the surface conjugate with the aperture plate AP). The image of the plate AP is set so as to be completely matched.

With this arrangement, as described in the description of the principle with reference to FIG. 2, the angle 2 (θ ₂ −) between the wavelength of the electron beam and the wavefronts of the two electron beams on the substrate SB is formed.
θ ₁ ) and linear interference fringes of uniform brightness with a constant pitch (in the case of the drawing, a fringe perpendicular to the paper surface) are clearly distinguished only by the outer edge of the aperture image area of the aperture plate AP. Formed. An example thereof is shown in FIG. Figure 3 (a)
Is inserted from the horizontal direction of FIG. 1 along the long side direction using a horizontally long rectangular aperture plate as the aperture plate AP, and the crystal CR and the electron biprism EBP are rotated by 90 ° around the central axis of the system. FIG. 3B is a drawing pattern formed when drawing, and FIG.
Insert the crystal CR and the electron biprism EBP in the same manner as in the case of FIG. 3A, with the two short sides in the foreground and the hypotenuse falling to the right, and inserting from the lateral direction of FIG. 1 along the short sides. 3C is a drawing pattern to be created, and FIG.
A right-angled isosceles triangular aperture plate similar to that of (b) is turned upside down, and this time, one of the short sides thereof is turned to the side facing and the side is inserted along the side from the lateral direction of FIG. FIG. 3D is a drawing pattern formed when drawing is performed in the state of FIG. 1, and further, FIG. 3D uses a vertically long rectangular aperture plate to insert from the horizontal direction of FIG. 1 along its short side direction. Then, the crystal CR and the electronic biprism EBP are drawing patterns formed in the same manner as in the case of FIG. In each of these cases, the interference fringes have the same pitch.

As described above, by using the electronic drawing apparatus as shown in FIG. 1, one light flux passing through the aperture plate AP having an arbitrary aperture pattern is converted into two light fluxes which form an angle with each other by the beam splitter using the crystal CR. Amplitude division is performed, and the two divided light beams are deflected by a biprism by an electronic biprism EBP so as to be closer to each other and crossed at an angle on an imaging plane conjugate with the aperture plate AP to be divided. Two aperture plates A
By superimposing the images of P on the image plane, the aperture plate A
It is possible to simultaneously draw a linear interference fringe pattern of uniform brightness at a constant pitch, which is clearly segmented by its outer shape only in the area in the aperture image of P. Then, in this method, the electron waves that interfere with each other on the image plane P are
Electron gun EG because it is a wave from the same position in the opening of
Does not need to be high, and writing can be performed using a thermionic electron gun instead of the field emission electron gun. Further, for the same reason, since all the electrons that have passed through the aperture plate AP can be used for drawing, the interference fringe becomes bright and uniform with large intensity, and the drawing speed is higher than that of the conventional method using electron beam interference. Greatly improved.

In the drawing method and apparatus as described above, in order to change the direction, pitch and phase of the drawn interference fringes, various methods are conceivable as mentioned in the explanation of the principle, but the directions are different. For example, the crystal CR and the electronic biprism EBP may be rotated around the central axis. Further, the pitch changes the position of the crystal CR in the central axis direction while maintaining the conjugate relation between the aperture plate AP and the drawing surface P instead of changing the energy of the electron from the electron gun EG, and accordingly, the electron bias is changed. The electric potential is changed so that the deflection angle of the prism EBP changes. Further, in order to change the phase of the interference fringe, for example, the aperture plate AP, the crystal CR or the electronic biprism EBP may be finely adjusted in the direction perpendicular to the central axis. A deflection system may be provided in the optical path and the deflection angle may be slightly changed.

The shape of the electron beam with which the aperture plate AP is irradiated is not particularly limited, but as shown in FIG. 1, the diameter of the beam divided by the crystal CR is the smallest at the position of the electron biprism EBP. As described above, it is desirable to focus on the upstream side of the aperture plate AP, and it is desirable to allow as many electrons as possible from the electron gun EG to pass through the aperture of the aperture plate AP. As shown in FIG. 1, when the crystal CR and the electron biprism EBP are arranged on the image side of the synthetic lens, the aperture plate AP is illuminated with a divergent light beam, and the image of the divergence point is formed near the electron biprism EBP. It is desirable to do so. Each lens CL
The positions of ₁ , CL ₂ , and Ob do not necessarily have to be as shown in the drawing, and the number is not limited to that shown in the drawing. Further, the image forming magnification may be arranged to be any of enlargement, equal magnification, and reduction.

By the way, by combining the four drawing patterns as shown in FIG. 3, for example, the wiring pattern as shown in FIG. 4 can be drawn. In the wiring pattern of FIG. 4, the areas indicated by reference characters a to d are respectively shown in FIG.
To (d), and the wiring patterns of FIG. 4 are created by connecting and drawing them continuously without deviation. At the time of this drawing, the aperture plate AP of FIG. 1 is replaced according to the drawing position, and the crystal C is changed according to each aperture plate AP.
The R and the electronic biprism EBP are rotated around the central axis. The stage ST on which the substrate SB is placed is also moved correspondingly.

As another example, one opening plate of an isosceles right triangle is used, and a drawing device is arranged parallel to the hypotenuse so as to form interference fringes at a constant pitch. When the four interference fringe patterns are connected by rotating each 90 ° around the apex, a spiral pattern as shown in FIG. 5 is formed. However, the interference fringe pattern of each isosceles right triangle is configured such that the phase shifts by ¼ wavelength each time the orientation differs by 90 °. The spiral pattern as shown in FIG. 5 can be used as a planar electromagnetic coil.

Further, while exposing any one of the interference fringe patterns as shown in FIG. 3, for example, the drawing device and the substrate SB are relatively moved in the direction of the interference fringes, so that a linear grid pattern with a long predetermined pitch is obtained. Can be created. At that time, when the opening of the aperture plate AP is a narrow slit and the slit is orthogonal to the interference fringes, even if the relative movement locus is a curve other than a straight line, a striped pattern running in parallel can be drawn.

According to the drawing method of the present invention, 100Å
You can easily draw even fine lines. The electron beam writing method and the electron beam writing apparatus of the present invention have been described above based on the embodiments, but the present invention is not limited to these embodiments and various modifications can be made.

[0025]

As is clear from the above description, according to the electron beam writing method and the electron beam writing apparatus of the present invention, the electron beam passing through the aperture having an arbitrary shape is angled by the beam splitter. Amplitude split into two light fluxes, and the two split light fluxes are deflected in a direction toward each other by a biprism,
By intersecting at an angle on the drawing surface that is conjugate with the aperture and overlapping the two divided aperture images on the drawing surface, an interference fringe pattern that is clearly divided only by the outline in the aperture image area can be obtained. Since the drawing is performed, the electron waves that interfere with each other on the drawing surface are waves emitted from the same position in the aperture, so it is not necessary to use a highly coherent electron beam source, and the field emission type Drawing can be performed using a thermionic electron gun instead of the electron gun. Further, since all the electrons that have passed through the opening can be used for drawing, the interference fringes are bright and have a large intensity, and the drawing speed is significantly improved as compared with the conventional method using electron beam interference. Further, since the outer shape of the interference fringe pattern to be formed is clearly divided and any opening shape can be used, the flexibility of the pattern that can be drawn is improved.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of an electron beam drawing apparatus for carrying out the electron beam drawing method of the present invention.

FIG. 2 is an optical model diagram for explaining the principle of the drawing method of the present invention.

FIG. 3 is a diagram showing an example of an interference fringe pattern drawn by the drawing method of the present invention.

FIG. 4 is a diagram showing a wiring pattern drawn by connecting the patterns of FIG. 3;

FIG. 5 is a diagram showing a spiral pattern drawn by the drawing method of the present invention.

[Explanation of symbols]

L ... Lens A ... aperture plate P ... drawing plane S ... light source BS ... beam splitter BP ... biprism _{A 1, A 2, A 1} ', A 2' ... aperture plate image EG ... electron gun CL ₁ ... first condenser lens AP ... aperture plate CL ₂ ... second condenser lens CR ... crystal EBP ... electron biprism Ob ... objective lens SB ... the drawing board ST ... stage 1,2,1 ', 2' ... light beam to d ... fringe pattern

Claims (7)

[Claims] 1. An electron beam luminous flux passing through an aperture having an arbitrary shape is amplitude-split by a beam splitter into two luminous fluxes forming an angle with each other, and the split two luminous fluxes are deflected by a biprism so as to approach each other. , An interference fringe pattern that is clearly divided only by the outline of the aperture image area by overlapping the two aperture images that are divided by intersecting each other at an angle on the drawing surface that is conjugate with the aperture and overlapping the two aperture images on the drawing surface. An electron beam drawing method, which is characterized by drawing. 2. The electron beam drawing method according to claim 1, wherein a plurality of interference fringe patterns are sequentially connected and drawn by using openings having different shapes. 3. A fringe pattern having a predetermined pitch is drawn by relatively moving the drawing surface in the direction of the interference fringe while exposing the interference fringe pattern formed by using one opening. The electron beam drawing method according to claim 1. 4. A replaceable aperture plate, an electron beam source for irradiating the aperture plate, an imaging electron optical system for forming an image of the aperture plate on a drawing surface, and a light flux from the aperture plate to the drawing surface. A beam splitter arranged inside the beam splitter for amplitude-splitting the electron beam passing through the aperture plate into two optical paths forming an angle with each other, and the two beams split by the beam splitter are deflected toward each other, and the drawing surface Cross over at an angle,
An electron beam drawing apparatus comprising: a biprism that superimposes two divided aperture images on an image plane. 5. The electron beam drawing apparatus according to claim 4, wherein the beam splitter is a single crystal plate that diffracts an electron beam, and the biprism is an electron biprism. 6. The electron beam according to claim 4, wherein the beam splitter is configured so that its position can be adjusted in the central axis direction, and the deflection angle of the biprism is adjustable. Drawing device. 7. The electron beam drawing apparatus according to claim 4, wherein the beam splitter and the biprism are integrally rotatable about a central axis.