JPH0670956B2 - Static controller for charged beam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to various devices for performing microfabrication, elemental analysis, etc. using a charged beam to deflect a beam by an electric field or to obtain a beam diameter or a beam sectional shape. The present invention relates to an improvement of the electrostatic controller for a charged beam, which is used for controlling the charged beam by changing, for example.

(Prior Art and its Problems) In a conventional electrostatic deflector for a charged beam (hereinafter, an electrostatic controller is represented by an electrostatic deflector), its main part is
A conductive deflection electrode (eg, copper, stainless steel, etc.),
An insulating electrode support that supports it (eg, alumina,
By applying a deflection voltage to the conductive deflection electrode made of glass or the like), an electric field is formed to deflect the charged beam.

In a conventional electrostatic deflector, for example, as shown in a front sectional view of FIG. 4A and a plan sectional view of FIG. 4B, the deflection electrode 2 made of copper is made of alumina (Al ₂ O ₃ ) and made of glass (SiO ₂ ). ₂ ) An electrode support 1 made of an insulating material is airtightly brazed, and this electrode support 1 is airtightly brazed and fixed to a grounded stainless steel frame 4. ing. 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 a deflection voltage applied thereto. The lead wire 5 to the deflection electrode 2 passes through both the hole 40 formed in the frame 4 and the hole 10 formed in the electrode support 1 and is brazed to the back surface of the deflection electrode 2.

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 9 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, its resistance value usually shows a high ground resistance value in the order of 10 ^{12 to} 10 ¹⁴ Ω, and therefore,
The equivalent resistance R1 of the electrode support 1 inserted between the grounded frame 4 and the deflection electrode 2 is a high resistance close to insulation.

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, an exposure apparatus is required to have an accuracy of 0.1 μm or less for a deflection width of about 10 mm, that is, a high accuracy of about 10 ⁻⁵ .

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. 3 is irregular vibration or shaking.

The other is that there is a phenomenon in which part of the charged beam 3 is scattered and adheres to the surface 11 of the electrode support 1 (charge-up). The potential of the surface 11 of the support is the adhesion of charged particles,
The peeling causes a large fluctuation, 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, in the former case, the lead wire 5 is strictly shielded (51), and an appropriate resistor R5 is added near the deflection electrode 2 in order to protect the power supply during discharge. . However, the result is not so good.

As for the latter, as shown in FIG. 5A, a measure was 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. But,
When this is also carried out, it has been 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 resistance network formed by the resistor r, and the voltages of the other node portions are applied to the deflection electrode 2.

The following two issues can also be taken up as problems. That is, one is that the surface potential of the conductive electrode is constant. This means that it is not possible to create any desired field strength distribution along the surface. (If this is to be realized, there is only a method of arranging a large number of small electrodes and applying an appropriate voltage to each of them, but this processing is practically impossible as in the above.) Another one That is, the structure of the electrostatic deflector is complicated, and it is difficult to obtain the electrode mounting accuracy.

There was such a thing.

(Object of the Invention) The present invention solves the above problems, is not easily affected by disturbance noise, and does not cause potential fluctuations that hinder the convergence of a beam, and has a simple structure. It is an object of the present invention to provide an electrostatic controller for a charged beam, which can control the charged beam accurately and highly accurately.

(Structure of the Invention) The present invention relates to an electrostatic controller composed of a control electrode and an electrode support, in which all or part of the electrode support is composed of a semiconductor, and a charged beam is mainly used, An electrostatic controller for a charged beam, wherein the control electrode is provided outside the electrode support.

(Embodiment) FIG. 1A is a front sectional view of an electrostatic deflector according to a first embodiment of the present invention. Members corresponding to those in FIGS. 4A and 4B are designated by the same reference numerals, and description thereof will be omitted.

The electrode support 1 is made of a semiconductor material such as SiC and has a volume resistance value of about 10 ⁶ Ωcm.

The electric field generated by applying the deflection voltage to the deflection electrode 2 acts on the charged beam 3 through the electrode support 1.
(To be more specific, a current flows from the deflection electrode 2 to the grounded frame 4 through the electrode support 1 and the surface of the electrode support 1 becomes an intermediate potential between the potential of the deflection electrode 2 and the ground potential. , This potential causes an electric field to be generated in the central space to deflect the charged beam 3.) When the electrostatic deflector for the charged beam has the above configuration, it occurs in the silicon carbide (SiC) electrode support 1. Figure 1C
The ground resistance R1 of the deflecting electrode 2 is about 10 ⁶ Ω. R1 is 1
If the resistance value is about 0 ^{6, the} current flowing from the control power supply to the deflection electrode is about 10 ⁻⁴ A, which is hardly a burden on the control power supply 6.

Due to the large decrease of the ground resistance R1 from the high resistance close to the insulation to about 10 ⁶ Ω, the influence of disturbance noise passing through the lead wire 5 is significantly reduced compared to the conventional one, and the resistance added to the lead wire 5 is reduced. The effect of R5 is also significantly increased.

Furthermore, even if charged particles collide with the surface of the electrode support 1,
Since the electrode support 1 is a semiconductor, no charge up occurs. Therefore, very accurate beam control is possible.

However, the conditions that enable this effect are as follows.

First, in order to generate a desired electric field at the position of the charged beam 3, the resistance value of the electrode support 1 is set to a potential as designed by the current flowing from the deflection power source (not shown) to the deflection electrode 2. You must have as many values as you have.

Since the realistic value of electric potential is about 10 ² V and that of electric current is about 10 ^-4 A, its resistance value needs to be 10 ⁶ Ω or more. If the electrode support 1 has a uniform resistance value, the dimensions are 1c
Assuming m ² and a length of 1 cm, the volume resistivity is 10 ⁶ Ωcm. Practically, it is possible to judge that the volume resistivity required for generating an electric field is 10 ² Ωcm or more, while it is possible to electrically change it by about 2 digits and dimensionally about 2 digits.

Next, in order to prevent the influence of charge accumulation (charge-up), even if a small amount of the current of the charged beam 3 collides with the electrode support 1, the amount of the current should affect the charged beam. It must have a low resistance that does not generate a significant voltage. As a practical numerical, current conflict 10 ^-6 A, since the voltage does not affect the beam is estimated to 10 ^0, the resistance value is required less 10 ⁶ Omega. Similarly to the above, if electrical and dimensional tolerances are applied, the volume resistivity needs to be 10 ¹⁰ Ωcm or less.

Based on the above two conditions, the electrode support as a whole has about 10
^It is necessary to have a volume resistivity of about ² to 10 ¹⁰ Ωcm.

FIG. 1B is a front sectional view of an electrostatic deflector according to a second embodiment of the present invention.

In this embodiment, the deflection electrode 2 is a simple conductive film 2'attached to the electrode support 1. The conductive film 2'is manufactured by metallizing the electrode support 1
A method of applying a metal film to the electrode, or, for example, a method of directly using the conductive deposition layer appearing on the surface of the electrode support 1 when the electrode support 1 of SiC is made by firing as an electrode, and further bending the wiring cable. There is a method of laying it in a plane.

Since the electrode support 1 which is a semiconductor has a function of making the electric field uniform by itself by the movement of electric charges, the deflection electrode 2 of the present invention has a considerably relaxed condition for its mounting accuracy. This is a side effect of the present invention.

FIG. 2A (front sectional view) and FIG. 2B (plan sectional view) are views of an electrostatic deflector according to a third embodiment of the present invention.

In this embodiment, first, the frame 4 is eliminated and the electrode support 1 itself also serves as a frame. conventionally,
In such an electrostatic deflector, a conductive tube called a drift tube is installed or a grounded frame 4 is provided to completely surround the charged beam. However, in the present invention, since the electrode support 1 is a semiconductor, it can serve as a drift tube, and therefore the structure can be greatly simplified.

Electrostatic deflectors usually use deflecting electrodes with 8 poles (see FIG. 2B) or 16 poles (multipole deflection) for one deflector, and further stack these deflectors in two axial stages. (Second
As shown in FIG. A), the method of reversing the deflection of the charged beam (double deflection) is adopted, so that simplification of this structure is important. Since the joint between the electrode support 2 and the frame 4 is eliminated, no special sealing technique is required, and the electrode support itself can be a vacuum partition, which is a great advantage.

Furthermore, the precision of the position of the deflection electrode 2 is uniquely determined by its mechanical processing precision, and since the machining is performed almost on the outer diameter side, high precision can be easily produced. A uniformizing effect of the electric field distribution by the electrode support 1 can also be expected.

FIG. 2C is a plan sectional view of the fourth embodiment of the present invention.

In FIG. 2B of the above embodiment, a notch (horizontal notch 7) is provided between the electrodes in order to make the distribution of the electric field strength of the generated electric field spatially stepwise as in the conventional case. The current is made difficult to flow into the adjacent electrodes. In this embodiment, this consideration is unnecessary, and more precise control is performed. That is, the current flowing in the semiconductor electrode support 1 between the X and Y deflection electrodes causes the fifth
An electric field similar to that described in FIG. C is generated in a distributed constant manner. The electric field strength changes spatially and continuously,
It is suitable for high-level charged beam control.

Originally, the use of 8- or 16-pole deflection electrodes
This is to correct the disturbance of the electric field in the middle in the X and Y directions. According to the configuration of this embodiment, the shape of the electrode support can be devised so that the X and Y deflection voltages are appropriately mixed in each case, and the currents appropriately flow into each other. Even if the electrode itself has four poles, an electrostatic deflector with an infinite number of poles can be used.

FIG. 3A is a front sectional view of the fifth embodiment of the present invention.

In contrast to the improvement of the electric field distribution in the horizontal direction in the above embodiment, in the present embodiment, the electric field distribution in the vertical direction is improved. That is, the stepwise spatial distribution shown in FIG. 2D above is changed to the spatial distribution of continuous electric field strength as shown in FIG. 3B, and the aberration associated with double deflection is reduced. By changing the shape of the electrode support according to the present invention, it is possible to realize almost any mode of electric field distribution in the three-dimensional direction.

In the above examples, SiC was used as the semiconductor electrode support, and the case where the material had a uniform volume resistivity was explained, but this is not an absolute condition, and a semiconductor film exists on the surface of the insulator. Even in such a combination type electrode support, if the resistance value thereof is within the above range, the same effect as described above can be obtained.

Further, in the above-mentioned embodiment, only the one having the deflector function for changing the direction of the beam orbit is taken as the controller of the charged beam, but the application of the present invention is not limited to this, and the stigmator for changing the shape of the beam is used. It is clear that the function and the Lens function that changes the size of the beam diameter also have a great effect.

Furthermore, silicon carbide has the advantage that its thermal conductivity is much higher than that of aluminum oxide, etc., and its thermal design is also very easy. Also, like aluminum oxide, surface metallization and control electrodes, It is easy to braze lead wires, and the bending strength and hardness are slightly higher. For this reason, it can be said that it is the most suitable material for the electrode support when the control electrode has to be fixed with extremely high accuracy like an electrostatic controller. Further, conventionally, silicon carbide has been widely used as seal parts such as bearings and parts for chemical pumps due to its good wear resistance and chemical resistance, and the stability of its material has been well proven. It is a particularly suitable material for the invention.

However, the material of the electrode support of the present invention is not limited to silicon carbide, and any substance having an appropriate volume resistivity can be used. For example, TiC, AlN, BN, and materials such as aluminum oxide and silicon oxide mixed with a metal can also be used.

(Effect of the Invention) According to the present invention, not only accurate control of a charged beam, which has hitherto been impossible, but also electrostatic control for a charged beam capable of highly controlling each element of the position, shape, and diameter of the beam. Can be provided.

[Brief description of drawings]

1A, 1B, 2A, and 3A are front cross-sectional views of an electrostatic controller according to an embodiment of the present invention. FIG. 1C is an equivalent circuit diagram. 2B and C are plan sectional views. 2D and 3B are diagrams showing the distribution of electric field strength. 4A, B, and C are a front sectional view, a plan sectional view, and an equivalent circuit diagram of a conventional electrostatic deflector. FIG. 5A is a partial front sectional view of a conventional electrostatic deflector. FIG. 5B is a plan sectional view of a conventional eight-pole electrostatic deflector, and FIG. 5C is a voltage distribution circuit diagram used therein. 1 ... electrode support, 2 ... deflecting electrode, 3 ... charged beam, 4 ... frame, 5 ... lead wire, 6,7 ... notch.

Claims (1)

[Claims] 1. An electrostatic controller for a charged beam comprising a control electrode and an electrode support, wherein the electrode support is wholly or partly made of a semiconductor and the charged beam is used as a center. An electrostatic controller for a charged beam, wherein a control electrode is provided outside the electrode support.