JPS5851384B2 - Deflection method of charged particle beam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for deflecting a charged particle beam.

In general, charged particle beam deflection and scanning systems are widely used in cathode ray tubes, television image pickup tubes, electron beam processing machines, electron beam exposure machines, scanning electron microscopes, ion implantation devices, and the like.

The present invention eliminates the oblique incidence and chromatic aberration of charged particle beams, which are drawbacks of conventional charged particle beam deflection systems used in these fields, and also provides a deflection method that reduces aberrations such as image distortion and coma. It provides:

FIGS. 1 and 2 are explanatory diagrams of a conventional deflection system.

FIG. 3 is a diagram explaining the principle of the present invention.

In Figures 1, 2 and 3, G is a charged particle beam source, LG
are the focusing electron lenses attached to the beam source, LM and MOL.
is a main focusing electron lens, S is an irradiated surface, and DM and DS are charged particle beam deflection means.

Note that the electronic lenses LG, LM and beam deflection means DM, D
As S, either an electrostatic type or an electromagnetic type may be used.

BO, B, B', and B'' are charged particle beams, and the beam BO is assumed to be a parallel beam for convenience of explanation.

In the case of no deflection, the beam BO passes through the main focusing electron lens LM or MOL to become the beam B, and the focus P
image is formed.

In the case of FIG. 1, when the deflection means DM is activated, the charged particle beam is deflected into a beam B' and focused on a point P'.

However, in this case, there are three problems:

(1) The beam obliquely enters the irradiated surface at point P', which is inconvenient for many applications (for example, if the irradiated surface of an electron beam exposure machine has unevenness, the oblique incidence causes positional errors).

(2) If there is a deviation in particle velocity of the charged particle beam, chromatic aberration occurs.

That is, the particle beam component having a low velocity is deflected by a large angle like beam B" and is imaged at a position P" different from P'.

(3) As the beam travel length between the lens LM and the irradiated surface S increases with deflection, the beam that was focused at one point P in the case of no deflection does not become focused at one point P' when deflected. In other words, coma aberration (an aberration in which an aberration that was converged at one point leaves a star-like tail) appears.

(4) An image distortion aberration (aberration in which a square changes into a barrel shape or a pincushion shape) appears in which the intensity of the deflection signal and the deflection distance (distance between P and P') are not proportional.

The above problem of oblique incidence can be solved by using the deflection means DM as shown in FIG.
This can be solved by providing a deflection means DS in the opposite direction, and the beam can be made perpendicular to the irradiated surface S, but the above problems of chromatic aberration (2) and image distortion (4) are solved. Not done.

The present invention solves all of the above four problems,
The principle will be explained below with reference to FIG.

The main focusing lens MOL in FIG. 3 is created by the method described later.
This is an electronic lens in which the main focusing lens shown in FIGS. 1 and 2 is moved parallel to the irradiated surface S by electrical means.

Two sets of deflection means DM! :The beam is translated in parallel like BO' by DS, and made to be perpendicularly incident on the center of the electron lens MOL' which has been moved directly above the deflection position P'.

As a result, the beam B' is perpendicularly incident on the deflection position P' on the irradiated surface S.

The beam BO", which is a chromatic aberration component caused by the difference in particle velocity, does not enter the center of the moved lens MOL, but enters parallel to the optical axis of the lens MOL', so on the irradiated surface S it is deflected at a deflection position P. The image is formed at the same position as ', and chromatic aberration related to the image formation position is removed.

Note that the beam B O //, which is a chromatic aberration component, is not incident perpendicularly to the irradiated surface, but the chromatic aberration is usually minute (beam energy deviation of about several ev), so chromatic aberration in the direction of incidence is not actually a problem. small enough not to become

Since the returned beam is incident parallel to the optical axis of the moved MOL, image distortion is also eliminated.

Furthermore, in FIG. 3, since the forward direction deflection means DM and the reverse direction deflection means DS are provided at the portions of the parallel beams (BO, BO', BO" are all parallel beams), the beam travels due to deflection. The path length difference does not affect its parallelism.

Therefore, comatic aberration at the focal point due to the difference in travel path length is eliminated.

Next, a method of moving the position of the main focusing lens MOL will be explained.

Hereinafter, the main focusing lens will be assumed to be an electromagnetic lens for convenience of explanation, and the magnetic field vector field forming the lens MOL when not deflected will be expressed as %.

The central axis of the lens is Xd and yd in the X and Y directions, respectively.
The magnetic field H when moving by .

H-HO (a%/c9x) xd (θ pull/ay) yd+V
2(θ2Ho/aX2)X2d+1/2(θ2Ho/a
y2) y2d+・・・・・・・・・ In S, when the amount of movement Xd, yd is small, the fourth and subsequent terms of this Tiller series are small, so if these are ignored, H−ya+HX−Xd+Hy−yd MashiHX = -δHo/θX), Hyconi-θHru/
θy).

On the other hand, if the deflection currents in the X and Y directions are xd and xa, the deflection distance is proportional to these, and if k is the deflection sensitivity, they are KIX and KIy, respectively, so to move the lens by the deflection distance is H2+HX-KIX+Hy, KIy, and the magnetic field vector field based on the second and third terms of the above equation can be formed by a deflection current and air.

The above can be physically realized because △H=O(
△ is Laplace operator), therefore △Hx=△H=O,
It is clear that both HX and Hy are magnetic vector fields that satisfy Laplace's equation.

In the case of a button electrostatic lens MOL, it can be realized in exactly the same manner as above, using an electric field E instead of the magnetic field H.

Next, an example of a moving focusing lens system MOL is shown in FIGS. 4 and 5.

The percentage in FIG. 4 indicates the magnetic field generated by a solenoid coil C, which is often used as a focusing electrode lens.

In the figure, X is the central axis, the X axis is on the paper, and the y axis is perpendicular to the paper (right-handed system).

If you look at this from an angle, it will look like coil C in Figure 5,
This coil C has a DC construction.

A magnetic field is generated by flowing .

The differential Hx=aH,ヮ10X with respect to X of this magnetic field indicates the X-direction component of the magnetic field, and as shown in FIG. ), and this magnetic field can be generated by passing a deflection current Ix through the coils C1x and C2x as shown in FIG.

The coils C1x and C2x each have the same shape as a coil that generates a normal electromagnetic deflection magnetic field.

However, in normal electromagnetic deflection, a magnetic field in the Y direction perpendicular to the X direction is used to deflect the beam in the X direction, but in the present invention, the magnetic field for moving the focusing lens MOL is parallel to the moving direction X (+x upper end of the direction) or antiparallel (lower end of the -x direction)
The difference is that a directional magnetic field is applied.

FIG. 6 shows the arrangement of the X-direction deflection coil when the movable focusing lens MOL of FIGS. 4 and 5 is applied to the deflection system of the present invention shown in FIG.

The arrangement of the y-direction deflection coils is also similar. To deflect the parallel beam BO incident along the central axis in the +X direction, 1
First, the beam is deflected in the +X direction by the +y force direction magnetic field of the deflection means DM, and then the direction of the beam is returned to parallel to the central axis by the -y direction magnetic field of the deflection means DS, but here the beam is translated in the +X direction. .

The center of the moving focal lens MOL is moved in the +X direction by the same amount as above by the current Ix flowing through the deflection means DM and DS. The beam converges at the deflection position P'.

The coils DS and C1x shown in FIG. 6 may be superimposed to form one coil.

In that case, the magnetic field direction of the composite coil is the direction of the fourth quadrant (+
X, -y direction).

Note that the actual angle of the direction of the magnetic field is determined by the intensity ratio of the directional components of each magnetic field.

As explained above, the present invention allows a deflected charged particle beam to be incident on an electro-optical lens that has been moved to a deflection position parallel to its optical central axis, and to converge the charged particle beam at the focal point of the lens. This has a remarkable effect of eliminating oblique incidence of the beam, chromatic aberration, coma aberration, and image distortion.

Note that astigmatism and curvature of the image plane (aberration in which the focal plane becomes spherical rather than flat) due to deflection cannot be removed by the present invention alone, but in order to remove them, the well-known dynamic focus correction (Dy
By using both namic focusing and dynamic astigmatism correction, a deflection system completely free of third-order (5eidel) aberrations associated with deflection can be obtained.

In addition, we have developed a charged particle beam projection method suitable for manufacturing high-density integrated circuits such as LSI and VLSI (Japanese Patent Application No. 50-12).
No. 7833) has been proposed, but if the deflection method of the present invention is applied to this method, it will bring many benefits.

[Brief explanation of the drawing]

FIGS. 1 and 2 are explanatory diagrams of a conventional charged particle beam deflection system. FIG. 3 is a diagram explaining the principle of the present invention. FIGS. 4 and 5 are explanatory diagrams showing an example of a moving focusing lens system used in the present invention. FIG. 6 is a diagram showing the arrangement of deflection coils when the movable focusing lens shown in FIGS. 4 and 5 is applied to the deflection system of the present invention shown in FIG. 3. Symbols in the figure G: Charged particle beam source, DM. DS... Beam deflection means, MOL... Main focusing electron lens, BO, BO', BO"... Parallel charged particle beam, S... Irradiated surface, P, P', P"... Image point.

Claims (1)

[Claims] 1. A charged particle beam is deflected so as to be incident parallel to the optical central axis of an electro-optical lens that has moved to a deflection position, and the charged particle beam is focused at a focal position of the lens. A method for deflecting a charged particle beam. 2. The electromagnetic field forming the electro-optical lens when not deflected is generated by the deflection signal.1. A charged particle beam according to claim 1, wherein the charged particle beam is moved to a deflection position of an electro-optical lens by superimposing an electromagnetic field determined by the spatial differentiation of said electromagnetic field in the direction of movement. deflection method.