JPH067466B2 - Electrostatic deflector for charged beam - Google Patents

Description

TECHNICAL FIELD The present invention relates to a charged beam electrostatic deflector used for microfabrication, elemental analysis, etc., and is used for an exposure apparatus, an electron microscope, a mass spectrometer, a local analyzer, etc. Will be effective.

(Prior Art and Problems Thereof) In a conventional electrostatic deflector, for example, as shown in a front sectional view of FIG. 4A and a plan sectional view of FIG. The electrode support 1 made of Al ₂ O ₃ ) or silicon oxide (SiO ₂ ) is airtightly brazed to the electrode support 1, and the electrode support 1 is airtightly attached to the grounded stainless steel frame 4. It is attached and fixed. A pair of such deflection electrodes 2 are provided in both directions of the X and Y axes, and the charged beam 3 is electrostatically deflected in both the X and Y directions by the deflection voltage applied to them. The lead wire 5 to the deflecting electrode 2 passes through both the hole 40 formed in the frame 4 and the hole 10 formed in the electrode support 1 and passes through the deflecting electrode 2
Is brazed on the back side of.

FIG. 4C shows an equivalent circuit of voltage application to one of the deflection electrodes 2 among them. A deflection voltage is applied to the deflection electrode 2 from the control power source 6 via the lead wire 5, but the volume resistivity of the material of the electrode support 1 is very high, and is 10 ^{12 to} 10 ¹⁴ Ωcm. Therefore, the resistance value thereof normally shows a high ground resistance value of the order of 10 ^{12 to} 10 ¹⁴ Ω, and therefore, the equivalent resistance R 1 of the electrode support 1 inserted between the grounded frame 4 and the deflection electrode 2 is insulated. High resistance close to.

By the way, the charged beam 3 is deflected by the electrostatic deflector having the above-mentioned configuration to irradiate the beam to an arbitrary position on the sample (not shown) for fine processing and analysis. Very high position accuracy is required for irradiation. For example, in the exposure apparatus, 0.1 μ is required for a deflection width of about 10 mm.
Accuracy of m or less, that is, high accuracy of about 10 ^-5 is required.

Therefore, the permissible value of the fluctuation of the voltage value applied to the deflection electrode 2 is very small and severe, and it is unavoidable to seriously deal with disturbance noise and the like.

The configuration of the conventional electrostatic deflector described above causes the following problems.

One is that the lead wire 5 to the electrostatic deflector easily picks up external noise, and the noise voltage of the disturbance that intrudes from the lead wire is superimposed on the deflection voltage. Is irregular vibration or shaking.

The other is that there is a phenomenon in which a part of the charge beam 3 is scattered and adheres to the surface 11 of the electrode support 1, and since the scattering of the charge beam cannot be completely eliminated, the surface of the electrode support 1 is not completely removed. The potential of 11 largely fluctuates due to the attachment and detachment of the charged particles, which distorts the deflection voltage of the charged beam 3 and causes an unexpected floating in the deflection, or hinders the convergence of the charged beam 3.

The conventional measures against these problems are as follows.

That is, with respect to the former, the lead wire 5 is strictly shielded (51) and also serves as a power source protection measure at the time of discharge.
A process of adding an appropriate resistor R5 near the deflection electrode 2 was adopted. However, the result is not so good.

For the latter, as shown in FIG. 5A, measures were taken to prevent the surface of the electrode support body from being exposed by covering the electrode support body 1 with a part 21 of the deflection electrode. However, as a result of carrying out this as well, it was found that in most cases, when the precision of the deflection is required to be high in a small device, the countermeasure is insufficient.

Generally, the electrostatic deflector is assembled in a small size with high precision and assembled, and as shown in FIG. 5B, the electrostatic deflector has a structure of 8 poles or more for the purpose of improving the accuracy of deflection. In many cases, many layers are stacked on top of each other, which is very time-consuming to process and tends to be expensive. The measures shown in FIG. 5A were actually complicated and difficult to implement.

As a precaution, FIG. 5C shows a distribution method of the voltage applied to each deflection electrode in FIG. 5B. The deflection voltages ± Vx and ± Vy in the X and Y axis directions are applied to the four nodes of the resistor network formed by the resistor r, and the voltages of the other node portions are applied to the deflection electrode 2.

(Object of the Invention) An object of the present invention is to solve the above problems, and to provide an electrostatic deflector that is not easily affected by disturbance noise and that does not cause fluctuations in potential that hinder beam convergence. And

(Structure of the Invention) A first invention of the present invention is an electrostatic device composed of a deflection electrode capable of applying a predetermined voltage to a frame and an electrode support for fixing the deflection electrode to the frame. In the deflector, the electrode support has a volume resistivity of 10 ² Ωcm to 1
The above object is achieved by an electrostatic deflector for a charged beam which is made of a material within the range of 0 ¹⁰ Ωcm.

A second invention of the present application is an electrostatic deflector including a deflection electrode capable of applying a predetermined voltage to a frame, and an electrode support body for fixing the deflection electrode to the frame,
The electrode support has a volume resistivity of 10 ² Ωcm to 10 ¹⁰
The object is achieved by an electrostatic deflector for a charged beam, which is made of a material within the range of Ωcm and which applies a voltage to the deflection electrode via the electrode support.

(Embodiment) First, an embodiment of the first invention of the present application will be described with reference to the drawings.

FIG. 1A is a front sectional view of a charged beam electrostatic deflector according to an embodiment of the present invention, and FIG. 1C is a sectional view taken along line AA. FIG. 1B is an equivalent circuit diagram, and the functions, names, and reference numerals of the respective members correspond to those in FIGS. 4A, 4B, and 4C.

In the present invention, in place of conventional aluminum oxide (Al ₂ O ₃ ) and silicon oxide (SiO ₂ ), silicon carbide (S
iC) is used for the electrode support 1 to which the deflection electrode 2
Is airtightly brazed. As in the conventional case, the electrode support 1 is also supported in an airtight manner with respect to the frame 4 which is grounded.

As is clear from FIG. 1C, the silicon carbide electrode support 1 of this embodiment is an annular body common to the deflecting electrodes 2, but this is an individual member as in FIG. 4B. May be provided.

Originally, in the electrostatic deflector, the absolute value of the electric field voltage itself is relatively small, about 10 ^{1 to} 10 ² V, which is in comparison with 10 ^{4 to} 10 ⁵ which is the voltage applied to the accelerating tube for generating the charged beam 3. And the value is extremely small. Therefore, the electrode support of the electrostatic deflector is not required to have a resistance as high as that of an insulator, unlike the electrode support of the acceleration tube.
The invention of the present application was made paying attention to this.

The ground resistance R1 of the deflection electrode 2 of FIG. 1B, which is generated in the silicon carbide (SiC) electrode support 1 of this embodiment, is 10
It is about ⁶ Ω. When R1 has a resistance value of about 10 ^{6, the} current flowing from the control power supply to the deflection electrode is about 10 ⁻⁴ A, and the control power supply 6 is hardly burdened.

Due to the large decrease from the high resistance close to the insulation of the ground resistance R1 to about 10 ⁶ , the influence of the disturbance noise passing through the lead wire 5 is significantly reduced as compared with the conventional case. Lead wire 5
Also, the effect of the resistance R5 added to is significantly increased.

In addition, since the electric charges attached to the surface of the electrode support 1 disappear and disappear through the grounding resistance R1, various disturbances caused by the scattering of the charged beam 3 on the surface 11 of the electrode support 1 are extremely different from the conventional ones. I was able to make it smaller.

There is a reason for selecting silicon carbide having a low volume resistivity as the material for the electrode support.

Without using silicon carbide, the ground resistance value of the deflecting electrode 2 of the conventional material, that is, aluminum oxide or silicon oxide, is 10
^To make it about ⁶ Ω, make the electrode support very thin,
It must be 1 μm or less. This is not feasible due to mechanical strength and space insulation issues. The practical value of the volume resistivity is 10 ⁶ Ω from the viewpoint of experiment and design.
It can be selected in the range of 4 digits up and down, that is, 10 ² Ωcm to 10 ¹⁰ Ωcm centering on the cm level. The reason for selecting this range is that fluctuations of plus or minus 2 digits from the viewpoint of disturbance noise and surface potential change, and plus or minus 2 digits from the viewpoint of the size of the unchanged electrode and electrode support are allowed. is there. The adjustment of the ground resistance value is also limited by the influence of the magnetic field generated by the flowing current on the deflection.

By adopting the same concept as the metal film resistor, even if a metal or semiconductor film is thinly coated on the surface of a conventional insulating material such as aluminum oxide, the same conductive surface and ground resistance value can be obtained. It is possible to get. However, as a practical matter, it is obviously difficult to control this resistance value as desired, and there is a possibility that the coating may be gradually peeled off by being hit by the charged beam 3 during long-term use.

When using silicon carbide having a specific volume resistivity of about 10 ⁶ Ωcm, for example, in order to obtain 10 ⁶ Ω as the ground resistance value, the size of the electrode support (individually for each deflection electrode) is large. The height may be set to 1 cm × 1 cm × 1 cm, which is an extremely realistic numerical value. The resistance value is, of course, almost constant regardless of how the surface is altered, and is stable over a long period of time.

Further, silicon carbide has an advantage that its thermal conductivity is much higher than that of aluminum oxide and the like, and thermal design becomes very easy.

Similar to aluminum oxide, silicon carbide can be easily metallized on the surface, brazed to the deflection electrode and the lead wire, and has slightly higher bending strength and hardness. For this reason, it can be said that it is the most suitable material for the electrode support when the deflection electrode has to be fixed with extremely high precision like an electrostatic deflector. Further, conventionally, silicon carbide has been widely used as a seal part such as a bearing and a part for a chemical pump due to its good wear resistance and chemical resistance, and the stability of its material has been sufficiently proved. .

However, in the present invention, the material of the electrode support is not limited to silicon carbide, and any substance having an appropriate volume resistivity can be used.

Further, the frame does not necessarily need to be grounded, and its material is not limited to metal.

Next, an embodiment of the second invention of the present application will be described with reference to the drawings.

FIG. 2A is a front sectional view of the electrostatic deflector for charged beam according to the embodiment of the present invention, and FIG. 2B is its equivalent circuit diagram. Each corresponds to FIG. 1A and FIG. 1B.

In this embodiment, the lead wire 5 is attached to the electrode support 1.
The brazing is performed at a position just behind the deflecting electrode 2. In the case of this configuration, the resistance value of the thin silicon carbide film from the brazing position to the deflection electrode 2 becomes the resistance R5 in FIG. 2B, and the resistance for preventing the disturbance noise from the lead wire becomes. , It is supposed to be naturally added by selecting the best position.

This configuration has additional practical advantages. This is because the airtight brazing is required only between the frame 4 and the electrode support 1, so that the process is simplified.

The second invention is more effective when implemented as shown in FIG. 3 (plan sectional view). That is, the silicon carbide electrode support 1 is formed in an annular shape, and the silicon carbide electrode support 1 is fixed to the frame 4 by a plurality of silicon carbide legs 7 which are integrated with the electrode support 1 or are provided separately. The role of the resistor (group) r of the resistor network shown in FIG. 5C is fulfilled. It is possible to make the conventional device of FIG. 5B resistant to noise, greatly simplify the device, and reduce the cost. Further effects are exhibited when the number of deflecting electrodes is more than eight, for example, 16 or when the electrostatic deflectors are stacked in the axial direction.

(Effect of the Invention) According to the electrostatic deflector for a charged beam of the present invention, not only the charged beam can be deflected with high accuracy, but also a shield for noise prevention, a cover for beam scattering prevention, etc. are not required, and the entire system is achieved. Can be greatly simplified.

[Brief description of drawings]

1A, 1B, and 1C are a front sectional view, an equivalent circuit diagram, and a plan sectional view of an electrostatic deflector according to a first embodiment of the present invention. 2A and 2B are a front sectional view and an equivalent circuit diagram of an embodiment of the second invention of the present application. FIG. 3 is a plan sectional view of another embodiment of the second invention of the present application. 4A, B, and C are front sectional views of a conventional electrostatic deflector,
Plan sectional view and equivalent circuit diagram. FIG. 5A is a partial front sectional view of a conventional electrostatic deflector. FIG. 5B is a plan sectional view of a conventional electrostatic deflector for eight poles, and FIG. 5C is a voltage distribution circuit diagram used therein. DESCRIPTION OF SYMBOLS 1 ... Electrode support, 2 ... Deflection electrode, 3 ... Charged beam, 4
... Frame, 5 ... Lead wire, 6 ... Control power supply, R1, R
5, r ... resistance.

Claims (2)

[Claims] 1. An electrostatic deflector comprising a deflection electrode capable of applying a predetermined voltage to a frame, and an electrode support for fixing the deflection electrode to the frame. An electrostatic deflector for a charged beam, comprising a material having a volume resistivity in the range of 10 ² Ωcm to 10 ¹⁰ Ωcm. 2. An electrostatic deflector comprising a deflection electrode capable of applying a predetermined voltage to a frame and an electrode support for fixing the deflection electrode to the frame. It is made of a material having a volume resistivity in the range of 10 ² Ωcm to 10 ¹⁰ Ωcm, and the predetermined voltage is applied to the deflection electrode via the electrode support. Charged beam electrostatic deflector.