JPH0616387B2 - Focused ion beam implanter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a focused ion beam implanter, and more specifically, to a focused ion beam implanter capable of reliably implanting ions into a material. .

(Prior Art) A focused ion beam apparatus using a liquid metal ion source starts from Ca, In, Si, Be, B,
Metal ions such as P, As and Zn can be obtained. These metal ions become P-type and N-type impurities with respect to the Si or III-V group semiconductor substrate (referred to as substrate). Therefore, if these ions emitted from the ion source can be injected into a substrate (hereinafter simply referred to as a material), maskless ion injection becomes possible. An ion implanter using such a focused ion beam (FIB) technique is called a focused ion beam implanter.

When accelerating ions of this kind of impurities into a single crystal Si wafer or the like, the beam is perpendicular to the wafer surface (<110
(> Direction, etc.), the ions are implanted deep without colliding with the atoms. FIG. 3 is a diagram showing a state of ion implantation. Atoms 2 are regularly arranged in the wafer 1 as shown in the figure. In this state, the ion beam B1 is applied to the wafer 1
When irradiated perpendicularly to the surface, the ions are implanted deeply without colliding with the atoms as shown in the figure. Such a phenomenon is called a channel effect.

In order to prevent this channel effect, the ion beam is irradiated onto the wafer 1 surface as a beam B2 obliquely inclined with respect to the wafer 1 surface, as shown in the figure, unless particularly deep ion implantation is intentionally performed. . Here, θ is an angle formed by the ion beam B2 and the optical axis K. The inclination angle θ is about 7 °. When such oblique irradiation of the ion beam is performed, the ions collide with the atoms 2 near the surface of the wafer 1 and stay near the surface as shown in the figure.

FIG. 4 is a structural conceptual diagram of a focused ion beam apparatus having such an ion beam oblique irradiation mechanism. An ion beam Bi emitted from an ion source (not shown) is two-dimensionally deflected in each of the x and y directions by a scanning (scanning) deflector 11 and enters an objective lens 12. The objective lens 12 is composed of an electron lens, and the passing ion beam Bi
Converge. Ion beam B passing through the objective lens 12
i is subjected to oblique irradiation deflection by the upper and lower two-stage oblique irradiation deflectors 13 and 14, and obliquely irradiates the wafer 1. In this case, the oblique irradiation deflectors 13 and 14 are configured in two stages in order to correct the chromatic aberration due to the deflection.

(Problems to be Solved by the Invention) In the above description, the case where the ion beam is irradiated onto the wafer (material) with an inclination of 7 ° with respect to the optical axis in order to eliminate the channel effect is taken as an example. It was However, this alone is not sufficient to eliminate channel effects. The reason will be described below.

FIG. 5 is a diagram showing a three-dimensional structure of a wafer (material). In the figure, x, y, and z are crystal axes of the wafer, and S1 and S2 are planes containing atom 2, respectively. The z axis of the crystal axes is parallel to the optical axis K, and the surfaces S1 and S2 are also parallel. The distance between the surfaces S1 and S2 is L. Now faces S1 and S2
Plane S which does not include atom 2 between and and is parallel to S1 and S2
Set 3. Even if the ion beam Bi inclined by θ with respect to the optical axis K is incident along the surface S3, it does not collide with the atom 2. Therefore, the channel effect still occurs.

The present invention has been made in view of such points,
The purpose thereof is to realize a focused ion beam implantation apparatus which can eliminate the channel effect and more surely perform ion implantation into a material.

(Means for Solving the Problems) The present invention for solving the above problems is directed to a focused ion beam implanting apparatus for irradiating a material with an ion beam to perform ion implantation. It is characterized in that the oblique irradiation deflector which is tilted only by a horizontal structure is rotatable, and a rotation drive mechanism for rotating the oblique irradiation deflector is provided so that the rotation angle can be controlled. It is a thing.

(Operation) The deflector for oblique irradiation is rotated by a predetermined angle in the horizontal direction by the rotation drive mechanism. FIG. 6 is an explanatory view of the operation of the present invention. By rotating the irradiation deflector by φ in the horizontal direction, the surface S3 shown in FIG. 5 is rotated by an angle φ like S3 '. As a result, the possibility that the incident ion beam Bi collides with the atom 2 can be greatly increased.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. The same parts as those in FIG. 4 are designated by the same reference numerals. In the figure, reference numeral 20 designates a block in which the oblique irradiation electrostatic deflectors 13 and 14 are fixed, and its three-dimensional shape is as shown in FIG. The block 20 is rotatable about an axis 30 (specifically, the x-axis or the y-axis) by ± 90 ° in the horizontal direction here.

Reference numeral 21 denotes a gear provided on the outer periphery of the block 20. When the gear 21 rotates, the block 20 rotates in the horizontal direction by a predetermined angle as shown in FIG. Two
Reference numeral 2 denotes a gear that meshes with the gear 21 and is attached to the rotary shaft of the motor 23. Reference numeral 24 is an MPU that outputs a control signal according to the rotation angle of the block 20 to the motor 23. The operation of the apparatus thus configured will be described below.

Ion beam Bi emitted from an ion source (not shown)
Is two-dimensionally deflected by the scanning deflector 11, enters the objective lens 12, and is converged. The ion beam Bi converged by the objective lens 12 enters the oblique irradiation deflectors 13 and 14 which are rotatable in the horizontal direction. Oblique irradiation deflector 1
3, 14 are fixed to the block 20 as shown in FIG. 2 as described above. When the MPU 24 gives a rotation control signal to the motor, the motor 23 rotates by an amount corresponding to the input signal. When the motor 23 rotates, the gear 22 directly connected to its rotation shaft also rotates, and the rotational force is transmitted to the gear 21 meshed with the gear 22.

When the gear 21 rotates, the block 20 accordingly rotates horizontally by a predetermined angle as shown in FIG. When the block 20 rotates, the deflectors 13 and 14 fixed inside the block 20 naturally rotate by the same angle. The rotation angle φ can be set to an angle that maximizes the probability that the ion beam Bi collides with the atom 2. Therefore, the ion beam Bi irradiated on the material is inclined by the angle θ (specifically, the above-mentioned angle of 7 °) with respect to the optical axis K, and is also inclined by the predetermined angle φ in the horizontal direction. The material 1 can be injected with the channel effect eliminated as shown in FIG.

Here, as a method of monitoring the horizontal rotation angle φ of the oblique irradiation deflectors 13 and 14, the following method can be considered.

A mechanism for mechanically reading the angle is provided.

The angle is measured by detecting the crosshairs (reference mark) placed on the stage.

In the above description, in order to rotate the oblique irradiation deflectors 13 and 14 in the horizontal direction, the block to which these deflectors are fixed is rotated by using the rotation drive mechanism as an example. However, the present invention is not limited to this, and any mechanism may be used as long as it can rotate the oblique irradiation deflectors 13 and 14 by a predetermined angle in the horizontal direction. Further, the mechanism for rotating the block 20 shown in the embodiment is not limited to one using gears, but any mechanism can be used as long as it can be rotated using a belt or other mechanism. Good. It goes without saying that the allowable range of the rotation angle is not limited to ± 90 as shown in the example.

(Effects of the Invention) As described in detail above, according to the present invention, it is possible to eliminate the channel effect by enabling the oblique irradiation deflector to rotate in the horizontal direction and controlling the rotation angle thereof. It is possible to realize a focused ion beam implantation apparatus capable of more reliably performing ion implantation in a material.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing a three-dimensional shape of a horizontal rotating portion, FIG. 3 is a diagram showing a state of ion implantation, and FIG. 4 is an oblique irradiation mechanism. FIG. 5 is a view showing the structure of a focused ion beam apparatus having the same, FIG. 5 is a view showing a three-dimensional structure of a wafer, and FIG. 11 ... Scanning deflector, 12 ... Objective lens 13, 14 ... Oblique irradiation deflector 20 ... Block 21,22 ... Gear 23 ... Motor, 24 ... MPU Bi ... Ion beam

Claims (1)

[Claims] 1. A focused ion beam implanter for irradiating a material with an ion beam for ion implantation, wherein an oblique irradiation deflector for tilting the ion beam by a predetermined angle with respect to an optical axis is horizontally rotatable. In addition, the focused ion beam implantation apparatus is characterized in that a rotation drive mechanism for rotating the oblique irradiation deflector is provided and the rotation angle can be controlled.