JPS593856A - Exb speed selector - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to an ExB speed selector, and more particularly to an EXB speed selector having a structure that focuses selected charged particle beams to form a sharp beam. Regarding.

(b) Background of the Technology In the manufacturing process of semiconductor devices, ion implantation is widely used as a method of introducing impurities into selected regions of a semiconductor substrate.

In the ion implantation method, as is well known, the required impurity ions formed in the ion source are introduced into the desired ion implantation area through extraction, separation, and addition, but the ion beam usually has a diameter of 5 to 10 mm. It is about as thick as a sword. The size of the pattern of the ion-implanted region of the semiconductor substrate is usually much smaller than the diameter of this ion beam, and VLN is performed on the surface of the semiconductor substrate with a film, and the entire film on the desired ion-implanted region is selectively removed. A mask is formed, and ion implantation is performed through this mask.

However, increasing the speed and integration density of semiconductor devices is 1'II.
In order to advance the process, the pattern of the ion implantation region needs to be miniaturized, which increases the difficulty of forming the mask. There is a need for a method of selectively irradiating impurities only to the introduced region.

(C) Prior Art and Problems An EXB velocity selector (also called a Wien filter) is already known as a velocity selector for charged particles such as ions. FIG. 1(a) is a schematic perspective view of the EXB speed selector, and FIG. 1(b) is an explanatory diagram of its operation. In the figure, 1 and 2 are magnetic pole pieces, between which a magnetic field having a magnetic flux density Bo is formed, and 3 and 4 are electrodes, and an electric field having an electric field intensity Eo is formed between these electrodes. In the structure shown in this figure, the electric field and magnetic field are orthogonal, and below the electric field r1
The direction is the X axis, and the magnetic field direction is the Y axis. The ion beam is introduced into the selector in the Z-axis direction at this EXB speed.

In this case, the trap, the mass of the ion is m, the charge is q2, and the position is (X
+ V + ZL velocity (XH'l, Z L acceleration (
x+y+z), the equation of motion becomes the following equation.

mx = q (Eo-ZBo) (1
) my = O, (2) mz-=qxBo (3J
Equation (1) becomes 0 when its right-hand side becomes Z=Eo/Bo. In other words, this shows that the forces exerted by the electric field and the magnetic field in the X-axis direction are balanced. Therefore, speed Vo==(0,0
, EO/BO), the ions Fi move straight in the ZtN direction at a constant velocity. On the other hand, ions whose speed is much higher than that are acted on by a blade parallel to the Xz plane, and are deflected in either direction of the positive X axis.

Therefore, as shown in (b), ISi'lIko5
By blocking the shielding plate 6, only ions with a velocity of VO can be selected.

Further, in detail 1, the French formula can be obtained by consolidating the previous Ir+ formula (1) by focusing on ions in the vicinity of the two axes where the velocity V is VoKll.

”;= −S” Bo2X (4
) Equation (4) indicates that a force proportional to the deviation from the Z-axis acts in the Z-axis direction, and it is known that the ion beam is focused in the X-axis direction.

That is, in the Oruzou EXB speed selector,
Ions whose velocity differs from Vo=Eo/Bo are deflected in the direction of the electric field force, and the ion beam traveling straight is focused in the direction of the magnetic field.

In order to form a sharp ion beam using the above-mentioned objective trap, it is necessary to focus the ion beam symmetrically with respect to two axes. As a method for making the ion beam focused symmetrically with respect to two axes, the second
While the magnetic field Bo and the electric field Eo are orthogonal to each other as shown in the schematic cross-sectional view in Figure 2(a), the magnetic pole faces 1' and 2' are tilted to each other as shown in the schematic cross-sectional view in Figure 2(b). A method is known in which the magnetic field is shaped like an arc.

In Fig. 2(b), the magnitude of the magnetic flux density passing through a point P on the central axis of the EXB speed selector is iBo, the electric field strength is Eo, and the center of a circle whose arc is the magnetic flux density a passing through P is 01.
Let Ro be the length of the radius OP of this circle. At this time, the electric field and magnetic field are expressed as shown below.

Ex = 'Eo (5
) Ey = o (6
)B y =8=B o (” Ro )
(8) In this case, the equation of motion corresponding to the cutting allowance (4) is as follows: Vo=Eo/Bo The ion beam is focused symmetrically on the Z-axis.

As explained above, the speed Vo=Eo/
The OJ function is to select Bo ions and bundle them into an axially symmetrical VC bundle, but as is well known, in the ion implantation method used in the manufacturing process of semiconductor devices, etc., the implantation depth of the ions is The kinetic energy, or velocity Vo, of the ions is selected to make the value approximately 011. Therefore, the EXE velocity selector applied to beam formation in the ion implantation method must have a function that satisfies the ion beam focusing requirements described above regarding the selected velocity VO or accelerator and pressure vIL.

(d) Purpose of the Invention The present invention provides an apparatus for selecting charged particles having a velocity distribution, such as ion beams, and for forming a sharp beam by focusing the particles. purpose.

(e) Structure of the Invention The object of the present invention is to provide static
and a magnetic pole disposed opposite to each other to form a static magnetic field that intersects the electrostatic field, the magnetic pole face of the magnetic pole being perpendicular to the magnetic field. This is achieved by an EXB speed sorter which can be adjusted so that seven lines coincide with 2,000 planes that include a certain straight line and are symmetrical with respect to the plane of symmetry of the electrostatic field.

The equations of motion of ions in the electric and magnetic fields expressed by the above equations (5) to (8) are the following equations (11) to (13), corresponding to the above equations (1) to (3).

mma=q(Eo-4By) (b)rny
=(IZBX ("9m"; =
q (xBy-multiBx) (131(]
3) Using the initial condition Z=Vof: Vo +-B in Z
oX (14) is obtained, Fio = Vo Bo (+5
), then the expression (+4)? Using equations (11) and (12'), when these equations (11') and (12') are satisfied, the acceleration layer V and y become symmetrical, and an ion with an initial velocity Vo becomes Z It is known that VC focuses axially symmetrically.

If the acceleration overpressure of ions is vn-, then the initial velocity is V.

Then, formula (1), (19 and (17)) yields.

Therefore, when implanting impurity ions, the electric field and magnetic field ratio Eo/Bo'k, t, is calculated according to equation (18) according to the type of impurity and the ion implantation depth. In order to focus the desired ion beam symmetrically around two axes, the radius of curvature of the magnetic field must be adjusted according to equation (19), that is, the magnetic pole surface must be adjusted to two directions including the center axis of curvature. It is necessary to make a thousand faces consistent.

(f) Embodiments of the Invention The present invention will be specifically described below by way of embodiments with reference to the drawings.

FIG. 3 is a sectional view showing the main parts of an embodiment of the present invention.

In the figure, 11 and 12 are magnetic pole pieces, 13 and 14 are electrodes, 15 is a core, and 16 is a coil.

The magnetic pole pieces 11 and 12 of this embodiment have a shape obtained by cutting a cylinder by a plane parallel to the axis, for example, a plane including the axis,
The opposing end surfaces of the core 15 are cylindrical surfaces that come into sliding contact with the magnetic pole pieces 11 and 12.

Furthermore, the pole pieces 11 and 12 can be rotated through the required angle to come into sliding contact with the end face of the core 15 by control from outside the device.

By rotating the # pole piece 11 and 120 times, the opposing magnetic pole faces can be respectively aligned with the plane containing the central axis of curvature of the required magnetic field.

Therefore, frost, pole 13! By forming an electric field Eo in the direction toward the pole 14 and a magnetic field Bo in the direction from the magnetic pole piece 11 toward the magnetic pole piece 12, and rotating the magnetic pole pieces 11 and 12 as described above, the electric field E is crossed.

and the normal force direction from the center of the magnetic field BO to the electrode 13 is expressed by equation (19)
The pole pieces 11 and 12 have 2,000 planes including a straight line perpendicular to the cross section of FIG. 3 at a distance of radius RO given by
If we align the magnetic pole faces of the ions and pass an ion beam with mass m1 and charge q from the paper surface side to the back side of the cross-sectional view of Fig. 3, we can select ions with energy qVη and focus them into a point. I can do it.

(g) Effects of the Invention As explained above, according to the present invention, charged particles having a velocity distribution, such as ion beams, are selected to have a desired velocity, and are focused to form a sharp beam. For example, selective ion implantation in a fine pattern can be performed without using a mask.

[Brief explanation of the drawing]

Figure 1 (a) is a perspective view showing an example of a conventional EXB speed selector, Figure #41 (b) is an explanatory diagram of its operation, and Figures 2 (a) and (b) are of a conventional EXE speed selector. FIG. 3 is a schematic sectional view of an electrode and a magnetic pole portion, and is a tli plane view showing a second embodiment of the present invention. In the figure, 1.1', 2 and 2' are pole pieces, 3 and 4
is an electrode, 5 is an opening, 6 is a shielding plate, 11 and 12FiMm
Piece, 13 and Hi 4id1iU&, I Fl::1
A, 16 indicates the coil 0 Figure 2 ((1) Figure 3

Claims (1)

[Claims] electrodes that are arranged to face each other to form an electrostatic field; and magnetic poles that are arranged to face each other to form a static magnetic field that intersects the electrostatic field (M is a magnetic pole of the magnetic pole). EX characterized in that the planes are adjusted to have a degree of adjustment M so as to correspond to 2,000 planes that include a - line that is a plane in the electrostatic field and that are symmetrical with respect to the plane of symmetry of the electrostatic field.
B speed sorter.