JPH0523012B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an E×B velocity selector, and more particularly, to an E×B velocity selector with a new structure that focuses selected charged particle beams to form a sharp beam. ×B Regarding the speed selector.

(Technical background) In the manufacturing process of semiconductor devices, as a method of introducing impurities into selected regions of a semiconductor substrate,
Ion implantation is widely used.

As is well known in the ion implantation method, the required impurity ions formed in the ion source are introduced into the target ion folding part after the process of extraction, separation and acceleration, but the ion beam usually has a diameter of 5 to 10 mm.
It is about mm thick. Compared to the diameter of this ion beam, the dimensions of the pattern of the ion-implanted region on the semiconductor substrate are usually much smaller! The surface of the semiconductor substrate is coated with a film, and the film is selectively applied to the desired ion-implanted region. This removal forms a mask, and ion implantation is performed through this mask.

However, in order to promote higher speed and higher integration density of semiconductor devices, it is necessary to miniaturize the pattern of the ion-implanted region, which increases the difficulty of forming the mask, and also makes it possible to achieve sharp edges without using a mask during ion implantation. There is a need for a method of selectively irradiating impurities only to impurity-introduced regions using an impurity ion beam.

(Prior Art) An ExB velocity selector, also called a Wien filter, is generally composed of two parallel electrodes and two magnetic poles perpendicular to these, and is used to control the ion beam, etc. It is used for speed selection of charged beams.

FIG. 2 is a block diagram of a conventional general E×B speed selector. In the figure, 1 and 2 are a pair of electrodes, and an electric field E _O is formed between the electrodes 1 and 2 in the X-axis direction. 3 and 4 are a pair of magnetic poles;
4, a magnetic field B _O is formed in the Y-axis direction.
Generally, electrodes 1, 2 are parallel to each other, magnetic poles 3, 4 are also parallel to each other, and the electric field E _O and the magnetic field
B _O , that is, the X and Y axes are orthogonal to each other.

The charging direction (optical axis) 5 of the charged beam is a Z axis perpendicular to both the X and Y axes, and an aperture hole 60 is provided at a position where the optical axis 5 penetrates the aperture member 6 .

Here, the mass of the charged particles (ions, electrons, etc.) constituting the charged beam is m, the charge is e, the above X,
If the position with respect to the Y, Z coordinate system is (x, y, z), the velocity is (x〓, y〓, z〓), and the acceleration is (x¨, y¨, z¨), then the configuration shown in Figure 1 is obtained. The equation of motion of charged particles in the E×B velocity selector is as shown in the following equation.

mx=e(E _O −zB _O ) ……(1) my=o ……(2) mz=exB _O ……(3) Here, in equation (1), if z〓=E _O /B _O Ba,
mx¨=o, and the forces exerted on the charged particles by the electric field E _O and the magnetic field B _O are mutually balanced in the X-axis direction.
Therefore, in Fig. 2, a charged particle that moves in the Z-axis direction and has a velocity of z = E _O /B _O (4), ie, a velocity v _O = (O, O,
The charged particles (E _O /B _O ) travel straight at a constant velocity and pass through the aperture hole 60 of the aperture member 6 . Further, when the speed z deviates from the above-mentioned condition (4), a force parallel to the XZ plane acts, causing deflection in the positive or negative direction of the X axis.

Now, when the velocity v of the charged beam is approximately equal to v _O , the equation of motion of the charged particles near the Z axis (optical axis) is linearized from equations (1) to (3) to form the following equation (5). obtained as follows.

x¨=-e ² /m ² B _O ² x ...(5) Equation (5) is the displacement X in the X-axis direction from the Z-axis (optical axis)
This shows that an acceleration proportional to is applied to the charged particles, and the charged beam is focused in the X-axis direction (electric field direction) and on the Z-axis.

Now, conventionally, in this way, the charged beam was
By passing through the ×B velocity selector, the beam is focused in the direction of the electric field, but this is only in the direction of the electric field, and there is a drawback that the resulting charged beam is not symmetrical around the Z axis.

As a method to solve this drawback,
3856 has been considered, but the degree of inclination needs to be changed depending on the type of charged beam required, and the accuracy of the inclination is The disadvantages were that the reproducibility was poor and the equipment became complicated and large.

(Objective of the Invention) The present invention provides an ExB speed capable of extracting and focusing only a charged beam having a desired velocity from a charged beam having a wide velocity distribution, and forming a high quality charged beam. The purpose is to provide a sorter.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides electrodes that are arranged opposite to each other to form an electrostatic field, and electrodes that are arranged opposite to each other to form the electrostatic field. and magnetic poles that form a static magnetic field that intersects with the optical axis. The above object is achieved by the E×B speed selectors which are arranged in a vertically connected manner, with the aperture holes provided in common.

(Operation) The operation of the front-stage quadrupole, which is behind the two quadrupoles in the front and rear stages connected in series as described above, is the same as the operation of the E×B speed selector described above. The electric field formed by the electrode pair of the rear quadrupole is placed at an appropriate position in the rear quadrupole, as in the case of the front quadrupole, and the equation of motion of a charged particle in the quadrupole at the rear stage is given by the following equation: .

mx¨=o ...(6) my¨=e( _ER −z〓B _R ) ...(7) mz¨=ey〓B _R ...(8) In this quadrupole, the magnetic field is in the X-axis direction. act, Y
This is because an electric field acts in the axial direction.

Here, the electric field of the latter quadrupole is E _R and the magnetic field is
It is called B _R. Then, the equation (9) is obtained as the equation corresponding to the above equation (5).

y¨=−e ² /m ² B _R ² y ...(9) Using the same idea as the first stage, in the second stage, the charged beam is
It shows that the Y-axis direction (the electric field direction of the rear quadrupole) is focused on the Z-axis.

That is, when E _O /B _O = E _R /B _R ...(10) is satisfied, v _O = (O, O, E _O /B _O ) =
A charged beam having a velocity of (O, O, E _R /B _R ) can be taken out from the aperture hole 60 .

Further consideration of the focusing effect results in the following.

The charged beam cyclotron radius r _O in the front-stage quadrupole and the cyclotron radius r _R of the charged beam in the rear-stage quadrupole are given by the following equations.

r _O ＝mv _O ／eB _O ……(11) r _R ＝mv _O ／eB _R ……(12) Here, L _O is the effective length of the quadrupole in the front stage, and L _R is the effective length of the quadrupole in the rear stage. _{If the distance between the _ _ _ _} At this time, the charged beam is focused symmetrically with respect to the Z axis at a distance f=r _R /sin(L _R /r _R )...(14) from the subsequent quadrupole.

Therefore, the electric field and magnetic field E _O of the quadrupole in the front and rear stages are
Although it is necessary to select B _O , E _O , B _O , effective lengths L _O , L _R , and the spacing Ld between the front and rear quadrupoles according to the speed of the charged beam, the resolution, etc., the present invention objectives are achieved.

(Example) FIG. 1 shows an embodiment of the invention.

In FIG. 1, the symbols of the quadrupole at the front stage are the same as in the conventional FIG. 2. In the latter quadrupole, 7,
8 is an electrode, 9 and 10 are magnetic poles, and 11 is a focal plane of a charged beam. In this embodiment, as described above, electrodes 1 and 2 are parallel to each other, magnetic poles 3 and 4 are also parallel to each other, and similarly, electrodes 7 and 8 and magnetic poles 9 and 10 are also parallel to each other. However, the electric field E _O formed by electrodes 1 and 2 and the electric field E _R formed by electrodes 7 and 8 are vertically connected to each other in the front quadrupole and the rear quadrupole so that they are orthogonal to each other. It is arranged as follows.

Further, as shown in FIG. 2, the effective length L _O of the quadrupole in the front stage, the effective length L _R of the quadrupole in the rear stage, the interval between the quadrupoles is Ld, and the focal length of the quadrupole in the rear stage is f. Further, the surface of the aperture member 6 and the focal plane 11 are both perpendicular to the optical axis 5.

As mentioned above, when a magnetic field B _O is formed in the +Y direction between the magnetic poles 3 and 4 of the front quadrupole, and a charged particle with a charge q and a mass m enters the front quadrupole along the optical axis 5, It is deflected in the -X direction by the magnetic field B _O. When the velocity of the charged beam is approximately equal to v _O , the electric field E _O is set at electrode 1,
Since the charged beam is formed in the +X direction between 2 and 3, the charged beam travels straight inside the front quadrupole along the optical axis 5, and is simultaneously focused in the X direction and onto the Z axis.

Next, in the embodiment, since the quadrupole in the later stage is connected in series, when the magnetic field B _R is formed in the +X direction between the magnetic poles 9 and 10 of the quadrupole in the later stage, the charged particles is deflected in the -Y direction by the magnetic field _BR .

Here, the electric field E _R is set at electrode 7,
8, the charged particles will travel straight through the rear quadrupole, and the charged beam will be focused in the Y-axis direction and onto the Z-axis.

Here, according to a configuration that further satisfies the conditions shown in equations (11), (12), and (13), an aperture member is placed on the focal plane 11 separated from the rear quadrupole by a distance f shown in equation (14). The charged beam passing through the aperture hole 60 of No. 6 is directed toward the Z-axis (optical axis)
It is focused symmetrically around the

Note that the shapes and structures of the electrodes and magnetic poles are not limited to those in this embodiment, and the methods for forming electric fields and magnetic fields are not limited to those in this embodiment.

For example, the electric fields of the quadrupole at the front stage and the rear stage may not be perpendicular to each other but may be oblique to each other.

Furthermore, the versatility can be further expanded by adding a function of making the distance Ld between quadrupoles variable.

(Effects of the Invention) According to the present invention, a charged beam having only a specific speed and mass is selected from a charged beam having an energy distribution, for example, an ion beam composed of multiple types having different masses and charges, and is focused. As a result, a high-quality charged beam can be formed, and, for example, it becomes possible to directly microfabricate a semiconductor substrate without using a mask.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an E×B speed selector according to an embodiment of the present invention. FIG. 2 is a similar diagram of a conventional ExB speed separator. 1, 2, 7, 8... electrode, 3, 4, 9, 10...
...Magnetic pole, 5...Optical axis, 6...Aperture member, 60...
Aperture hole, 11... Focal plane.

Claims (1)

[Claims] 1 A quadrupole is formed by comprising electrodes that are arranged to face each other and form an electrostatic field, and magnetic poles that are arranged to face each other and form a static magnetic field that intersects the electrostatic field. , at least two such quadrupoles,
1. An EXB speed selector characterized in that the directions of the electrostatic fields are crossed, the optical axis and the aperture hole arranged on the optical axis are common, and the EXB speed selector is arranged in a vertically connected manner.