JPH01124948A - Focused ion beam implantation device - Google Patents

Abstract

PURPOSE:To make it possible to dynamically compensate a focus on a beam irradiation point at a high speed by employing a hardware operation circuit for obtaining a dynamic focus compensation signal from a deflection signal for graphic scanning. CONSTITUTION:An operation circuit 32 receives oblique irradiation signal and deflection signals (Vx, Vy) for graphic scanning from a distributor 34, obtains a dynamic focus compensation signal (Vx<2>+Vy<2>)<1/2> for compensating a focus by operation, and outputs the obtained result to an amplifier 25. The amplifier 2 drives a sub-lens 24 according to an input signal and dynamically compensates the focus for the height difference h based on the difference between an x-y plane of a material 28 and an X-Y plane of scanning deflectors 22a, 22b. This makes it possible to irradiate well-focused ion beam Bi on the material 28 even in the case of oblique irradiation.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a focused ion beam implantation device, and more particularly to a focused ion beam implantation device that enables dynamic correction of the focal point at a beam irradiation point.

(Prior Art) A focused ion beam device using a liquid metal ion source uses Ga, Jn, and S; from the ion source.

Metal ions such as Be, B, P, As, etc. can be obtained. These metal ions are P-type,
It becomes an N-type impurity. Therefore, if these ions emitted from an ion source can be implanted into a substrate (hereinafter simply referred to as material), maskless ion implantation becomes possible.

An ion implantation device using such a focused ion beam (FIB) technique is called a focused ion beam implantation device.

When accelerating ions that become this type of impurity and implanting them into a single-crystal Si wafer, etc., the beam is perpendicular to the wafer (<110
> directivity), the ions are implanted deeply without colliding with atoms. FIG. 6 is a diagram showing the state of ion implantation. In the wafer 1, atoms 2 are regularly arranged as shown in the figure.

In this state, when the ion beam B1 is irradiated perpendicularly to the surface of the wafer, the ions are implanted deep into the wafer without colliding with atoms, as shown in the figure. Such a phenomenon is called a channel effect.

In order to prevent this channel effect, unless a particularly deep ion implantation is intentionally performed, the ion beam is irradiated onto the wafer 1 as a beam B2 that is tilted obliquely to the wafer 1 surface as shown in the figure. .

Here, 0 is the inclination angle that the ion beam B2 makes with a plane perpendicular to the optical axis K. The inclination angle θ is about 7°. When such oblique ion beam irradiation is performed, the ions collide with atoms 2 near the surface of the wafer 1 and remain near the surface, as shown in the figure.

FIG. 7 is a conceptual diagram of the configuration of a focused ion beam device having such an oblique ion beam irradiation mechanism. Ion source (
The ion beam [3i is for scanning (not shown)] is emitted from the ion beam [3i is for scanning (
For scanning) X with deflector 11.

V enters the objective lens 12 after receiving two-dimensional deflection in each direction. The objective lens 12 is composed of an electron lens, and focuses the passing ion beam B1.

The ion beam Bi that has passed through the objective lens 12 is
The wafer 1 is deflected for oblique irradiation by the deflectors 13 and 14 for oblique irradiation on the stage, and the wafer 1 is irradiated obliquely. In this case, the reason why the deflector for oblique irradiation has a two-stage configuration of 13 degrees and 14 degrees is to correct chromatic aberration due to deflection.

(Problems to be Solved by the Invention) By the way, in a focused ion beam implantation apparatus having such an oblique irradiation mechanism, the wafer 1 is irradiated with an ion beam Bi tilted by 7 degrees with respect to the optical axis. Therefore, in the irradiation section, as shown in FIG.
The plane (xy plane) of the wafer 1 is different from that of the wafer 1.

Therefore, the height of the point where the beam is irradiated differs depending on the inclination angle θ, so that the focus of the ion beam shifts. Now, assuming that the deflection width is 1 mm square as shown in the figure, both ends of the deflection width are the X-Y plane and the x that is actually drawn.
The difference in height from the −y plane is Δh−61 μm. As a result, the ion beam 3i becomes out of focus by about 0.12 μm (when the beam aperture angle=11rad).

The present invention has been made in view of these points, and
The purpose of this is focused ion beam implantation, which corrects the height difference between the drawing surface of the scanning deflector and the drawing surface of the material, and enables beam drawing that is always focused on the material surface. The purpose is to realize the device.

(Means for Solving the Problems) The present invention, which solves the above-mentioned problems, is a focused ion beam implanter having an oblique irradiation mechanism. The present invention is characterized in that it includes an arithmetic circuit that obtains a dynamic focus correction signal (where K is a correction coefficient @).

(Function) A hard arithmetic circuit is provided to obtain a dynamic focus correction signal from the deflection signals (Vx, Vy) for figure scanning. This makes it possible to perform dynamic correction of the focus at the beam irradiation point at high speed.

(Embodiments) Hereinafter, embodiments 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.

In the figure, 21 is an objective lens (main lens), 22a
, 22b are scanning deflectors that scan the ion beam in two-dimensional directions, and 23a and 23b are scanning deflectors 22, respectively.
a, a deflection amplifier that drives 22b, 24 is the objective lens 2
A sub-lens for beam focus correction arranged above 1, 25
is an amplifier that drives the sub-lens 24.

26a and 26b are deflectors for oblique irradiation, and 27a.

27b is an amplifier that drives the oblique irradiation deflectors 26a and 26b, respectively, and 28 is a material to which the ion beam Bi is obliquely irradiated. 29 is a CPU that outputs pattern data and signals for oblique irradiation, and 30 is a D/A converter that converts the pattern data and signals for oblique irradiation into analog signals. 31 is a deflection amplifier 23a which receives the output of the D/A converter 30.

23b is a distributor that supplies a scanning signal based on pattern data to the arithmetic circuit 22, and a deflection amplifier input signal and an oblique irradiation signal to the arithmetic circuit 22.

The arithmetic circuit 32 is made up of a hardware circuit, and receives the deflection amplifier input signal and the oblique irradiation signal and outputs the ion beam Bi.
A dynamic focus correction signal for focus correction is output and applied to the amplifier 25.

33 is a D/A that converts the oblique irradiation signal into an analog signal.
A converter 34 is a distributor that receives the output of the D/A converter 33 and provides oblique irradiation signals to the amplifiers 27a and 27b, respectively. The operation of the device configured as described above will be explained as follows.

The drawing pattern data output from CPLJ29 is D
/A converter 30 converts the signal into an analog signal. This analog drawing signal is passed through a distributor 31 to a deflection amplifier 23.
Enter a, 23b. These deflection amplifiers 23a, 23
b drives the scanning deflectors 22a and 22b according to the input signal, whereby the ion beam Bi is deflected in two-dimensional directions.

The ion beam 3i that has received this deflection enters the objective lens 21 and is focused.

On the other hand, the CPU 29 also outputs an oblique irradiation signal for irradiating the beam at a predetermined angle with respect to the optical axis.
It is included in D/A converter 30.33. Among these, D/A
After the input into the converter 33 is converted into an analog signal,
It enters the distributor 34.

From the distributor 34, a two-stage deflection amplifier 27a is provided.
, 27b is applied with an oblique irradiation signal, and the amplifiers 27a,
27b is a deflector 2 for oblique irradiation that corresponds to the input signal.
6a and 26b. As a result, objective lens 2
The ion beam Bi focused by 1 is tilted by an angle θ (for example, 7°) with respect to the optical axis and irradiates the material 28. Therefore, ion implantation into material 28 is performed with channel effects eliminated.

When such oblique irradiation is performed, the scanning deflector 228.22
The X-Y plane of b is different from the x-y plane of the actual material,
The fact that defocus occurs has been explained with reference to FIG. In the present invention, the height difference Δ between the two planes at this irradiation position is
The sub-lens 24 performs dynamic focus correction based on h.

FIG. 2 is a diagram showing the characteristics of the sub-lens 24. Here, it is assumed that the sub-lens used has an electrode structure as shown in FIG. In FIG. 3, the shaded portions are electrodes. In FIG. 2, the horizontal axis is the lens voltage (KV), and the vertical axis is the focal length ΔZ (+U+). If the lens voltage between 0 and 10 Kv is simply approximated by a straight line (connecting the middle points of X in the figure with a straight line), the sensitivity of this sub-lens will be 2 μa+/V. In other words, the focal position changes by 2μ with a lens voltage of 1μ. Therefore, since the maximum value of Δ2 when tilted by 7° is 60 μm in the case of FIG. 8, the lens voltage required for focus correction is about 30V. Incidentally, since the characteristic shown in FIG. 2 is approximately linear, the error can be almost ignored even if it is approximated by a straight line.

Therefore, in the embodiment shown in FIG.
receives the deflection signal for figure scanning and the signal for oblique illumination from the distributor 31, calculates a dynamic focus correction signal for correcting the focus, and outputs it to the amplifier 25. The amplifier 25 drives the sub-lens 24 according to the input signal, thereby controlling the height difference Δh based on the difference between the X-Y plane of the scanning deflectors 22a and 22b and the x-y plane of the material 28. Performs focus correction. As a result, even in the case of oblique irradiation, the material 28 can be irradiated with a focused ion beam Bi.

The figure scanning signal input to the arithmetic circuit 32 consists of an X-direction signal vx and a y-direction signal Vy, and theoretically
The value of x + y is proportional to the distance by which the beam is deflected. Further, when the beam is tilted by 7 degrees, the relationship between the intra-field deflection (11II11 squares) distance ΔX and the difference in height between the two surfaces Δh is as shown in FIG. 4 (see FIG. 8). From this figure, the height difference Δh due to beam deflection can also be approximated by a straight line.

Here, the deflection distance d based on the deflection signals VX and vy in each of the x and y directions is expressed by the following equation.

d = Kt Cv77"T"7 - (1)
K1 + Coefficient On the other hand, the focus correction amount ΔZ based on the dynamic focus correction is expressed by the following equation, with the output of the amplifier 25 being Vj.

ΔZ −K 2 ・■O ・・・
(2) K21 coefficient On the other hand, the height difference Δh based on the deflection distance d is expressed by the following equation.

Δh=Kx・d...(3)
K3: Since the condition for the coefficient beam to be focused is Δ2=Δh, the following equation holds true from equations (1) to (3).

K2·v1=1·K3r■rτ+Vy' (4) From this, the output ■O of the amplifier 25 is determined as follows.

VJ-(Kl ・Kx/Kz) x +
yT=K x +vyT −r
s>K; correction coefficient (=Kt·Kl/2) From the above, by having the arithmetic circuit 32 calculate equation (5) using hardware, it becomes possible to perform dynamic focus correction according to the deflection distance d. According to the present invention, since the dynamic focus correction I is determined by hardware, it is possible to perform automatic focus correction at a lower cost and at higher speed than dynamic correction using software. Further, according to the present invention, by automatically changing the calculation coefficients using hardware according to the inclination angle θ (up to 7°), it is possible to deal with all inclination angles θ.

In the embodiments described above, a case has been described in which dynamic focus correction is performed by sending a correction signal to the sub-lens 24 provided outside the objective lens 21.

However, the present invention is not limited to this.

For example, as shown in FIG. 5, one objective lens 21 (
(see FIG. 1) may be used to control the voltage applied to the center electrode. As shown in the figure, a voltage power source 4 that generates a maximum of 50 KV in a lens high voltage power source 40
A floating high-speed amplifier (for example, a maximum output of 50
V) 42 are connected in series. Then, the output of the arithmetic circuit 32 (see FIG. 1) is converted into an optical signal, and the output is sent to the optical fiber 43.
This is transmitted to the high-speed amplifier 42. The high-speed amplifier 42 changes its output according to the control output of the arithmetic circuit 32 and supplies it to the center electrode 21b of the objective lens 21. As a result, the amount of convergence of the objective lens 21 is changed, and the focal position on the material is dynamically changed. This allows automatic focusing of the ion beam onto the material.

(Effects of the Invention) As described above in detail, according to the present invention, by providing a hard arithmetic circuit for calculating a dynamic focus correction signal from a deflection signal for figure scanning (VX, vy>), A focused ion beam implanter that corrects the height difference due to the difference between the drawing surface of the scanning deflector and the drawing surface of the material, making it possible to perform beam drawing that is always focused on the material surface. can be realized.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an embodiment of the present invention, Fig. 2 is a diagram showing the characteristics of the sub-lens, Fig. 3 is a diagram showing the electrode structure of the sub-lens, and Fig. 4 is a diagram showing the in-field deflection distance and 2 5 is a diagram showing the main part of another embodiment of the present invention, FIG. 6 is a diagram showing the state of ion implantation, and FIG. 7 is a diagram showing the oblique irradiation mechanism. FIG. 8 is a conceptual diagram of the configuration of a focused ion beam device, which shows the relationship between the X-Y plane and the x-y plane of the material based on the scanning deflector. 21...Objective lens 213.21b, 21C-...Objective lens electrode 22a,
22b...Scanning deflector 23a, 23b...Deflection amplifier 24...Sub lenses 25, 27a, 27b ・7 amplifiers 26a, 26b...Oblique irradiation deflector 28...Material 29... CPU30.33...D/
A converter 31.34...Distributor 32...Arithmetic circuit 40
... Lens high voltage power supply 41 ... High voltage power supply 42 ...
・High-speed amplifier 43... Optical fiber patent applicant Japan Electronics Co., Ltd. Patent attorney Ijima
Fuji Jigai 1 person Figure 2 Figure 3 Steel 6 and Figure 7

Claims (3)

[Claims] (1) In a focused ion beam implanter with an oblique irradiation mechanism, a dynamic focus correction signal of K√(Vx^2Vy^2) is received in response to the deflection signals (Vx, Vy) for figure scanning (where K is a correction coefficient ) A focused ion beam implantation device characterized by being provided with an arithmetic circuit that obtains the following. (2) The focused ion beam implantation apparatus according to claim 1, wherein the dynamic focus correction signal drives a sub-lens for focus correction provided outside the main lens. (3) The focused ion beam implantation apparatus according to claim 1, wherein the dynamic focus correction signal drives a high-speed amplifier connected to the main lens.