JPS58209844A - Electric field ionization type ion source - Google Patents

Abstract

PURPOSE:To provide fine ion beam having high luminance by grinding tungsten single crystal fine wire used as a needle-shaped electrode so as to have the specified radius of curvature and by constructing the top end of a tungsten chip with a face of special structure. CONSTITUTION:In an ion beam irradiation apparatus in which high voltage is applied between a needle-shaped electrode and a draw out electrode in gas environment exhaust in a high vaccum and fine ion beam having high luminance and comprising gas positive ions is generated from the top end of the needle- shaped electrode, tungsten single crystal fine wire 1 is electrolytically polished and the top end of it is sharpened so as to have a radius of curvature of 5,000- 300Angstrom , and electric field evaporation treatment is performed on it so that 100 face may appear on the top end of the chip. Further, evaporation treatment is performed under released conditions, to form rough surface of C(2X2) structure. Microscopic roughness is increased on the surface and ion beam having high luminance is obtained through this process. Where, C(2X2) structure is a state that five atoms have mutually evaporated from the lattice which forms 100 face.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to the shape of a needle-like electrode for obtaining a small diameter ion beam for high brightness agricultural machinery.

(b) Background of the technology In the manufacturing process of semiconductor large-scale integrated circuits (LSI), it is necessary to process line widths of about 1 [μm], and in this case, alignment accuracy of ol [μm] is required. It is said that Conventionally, photo-etching technology (photolithography) has been used to form fine patterns.

In other words, light (1% JLJ) is passed through a mask to a thin resist film coated on a semiconductor substrate (wafer). Total irradiation 1
- Utilizing the fact that the portion exposed to light polymerizes or decomposes, resulting in a difference in solubility in a developer, 2. Opens a window in a fine pattern in the resist film and performs processing such as dry etching after V. Various patterns are created.

However, the purpose is to process a line width of 1 [μm] or less (on the other hand, in the conventional projection exposure method using light, the minimum processing width is limited to about 15 [μm] due to limitations due to the wavelength used). .

Therefore, ion beam exposure, electron beam exposure, X-ray exposure, etc. are used for this purpose.

Although both of these have the inherent advantage of being able to expose fine patterns, ion beams have the advantage of being easier to focus and collimate and have higher resolution than the other two.

In other words, in the case of XfFIJ, there is no lens suitable for this, so the gap ζ between the mask and the wafer may result in penumbra blur [7] Also, when using an electron beam, backscattering after wafer collision and While the proximity effect due to strong energy secondary city, child emission etc. is recognized,
In the case of an ion beam, there is not much back scattering and the energy of the secondary electrons generated is low, so the effect can be expected.

The most important feature of the ion beam is that it has the ability to draw precise patterns using computer control, and in this respect it is similar to the electron beam.
r! It has features that electron beams cannot have, such as introducing impurity elements by ion implantation and processing wafers by ion etching.

Now, in order to carry out precise pattern drawing, impurity implantation, etc., which are characteristics of ion beam mist, it is necessary that the ion beam has a high brightness and a small diameter.

In other words, by making the tips of the needle-like poles as sharp as possible, the electric field strength can be increased and the brightness can be increased when the ion beam diameter is small.

(e) Prior art and problems Figure 1 shows the configuration of the ion chamber where the ion beam is formed in an ion beam exposure system. Figure 2 shows the shape of the tungsten (W) needle-shaped electrode used as the ion source. Showing money.

In the figure, the conventional ion source has a diameter of 200 to 300 μm.
] The entire tip of a W head 1 is electrolytically polished to make it sharp into a button shape, and the gas to be formed, such as hydrogen, is supplied from the nozzle 2 to the entire tip of the ion beam, and at the same time the inside of the device is heated to about 10-7 [ torr] high vacuum discharge (by applying a DC high voltage between the W electrode 1 and the extraction electrode 3 with a hole in the vertical shape, hydrogen gas is field ionized at the tip of the W electrode, and the extraction A hydrogen ion beam is obtained from the hole 4 of the electrode 3.

The reason W is chosen as the ion source here is that its melting point is 338.
This is due to the fact that the tip of the electrode does not change and become stiff even if the temperature is as high as 7 [°C] and the large flow density is exceeded.

Now, in order to ionize gas molecules in an electric field and obtain a high-brightness micro-diameter ion beam of gas cations, it is necessary to make the tip of the W electrode as sharp as possible and increase the electric field strength by 1fe, which is not possible with conventional W wires. W single crystal is used. In other words, when performing electrolytic polishing using a conventional W wire, the radius of curvature is only a few [μm], whereas when performing electrolytic I1F polishing using a thin W wire made of single crystal, the radius of curvature is only a few [μm]. 100 to several thousand [A] can be obtained.

In this case, W with a known plane orientation in the thin wire cross section is produced industrially, for example, with a crystal plane in the (100:) direction, a diameter of 0.2 [mm) and a stiffness of about IO [n1m]. Fine wire is available and suitable for this purpose.

Now, in this case, the entire W single crystal wire chip that has been depolished has been replaced, and the tip of the tip is flattened by bamboo evaporation.
The t(100) plane and the 1~ plane are often used as ion sources.

Here, field evaporation is performed using the ion beam equipment shown in Figure 1 under a high vacuum of less than lo [torr].
In this evacuated state, a positive high voltage is applied to the tip of the Wil so that the electric field changes by about 6 [v/in], and the total temperature of the W kasuri 1 is maintained at about 15 [K].

In this case, W atoms become ions and evaporate from the tip of the W line 1, so that the entire tip surface can be made into a perfect [100) plane crystallographically.

Conventionally, an ion beam was formed using the W single crystal thin wire (hereinafter referred to as a W chip) produced in this manner as an electrode, and ion beam exposure was performed. However, there was much hope for the emergence of an ion source with higher brightness in this ion beam exposure.

(d) Object of the Invention An object of the present invention is to provide a needle-like electrode shape that obtains a micro-diameter ion beam with higher brightness than before.

(e) Structure of the Invention The object of the present invention is to polish the W single crystal thin wire used as a sword-shaped electrode to have a radius of curvature of 5000 CA:] or less, and to make the tip of the W tip have a C (2X2) structure. 0 (1) It can be used in a state where it is configured as follows.

(f) Embodiments of the Invention In order to obtain high brightness, the present invention uses W with an exposed floo surface.
The tip of the chip was further subjected to electric and field evaporation under different conditions to form a (100) surface metal C (2×2) structure.

Here, the C(2X2) structure refers to a state in which atoms are alternately evaporated from the lattice points forming the (100) plane gold.

In other words, Fig. 3 shows the (100) plane arrangement of W with a body-centered cubic crystal lattice, but if the temperature of the W chip is maintained at When the electric field strength V at the tip of the tip is about 6 (V/A) and the field evaporation continues, ions selectively evaporate at the starting part ζ. W atoms 5 are arranged in a lattice pattern. It is known to obtain a planar surface, and a W chip is commonly used as an ion source.

However, recently, for a W chip with such a flat rloO) surface, the chip TlHf'f: about 450 [K) - the total electric field strength at the tip of the chip raised with soil is about 4 [V/in] l It was found that when electric field evaporation 9 is continued, atoms evaporate every other crystal plane that forms the (], OO) plane, resulting in an uneven surface state. (G ,Ehrtic
hPhysics 'f'oday 47. June
e 198] Figure 4 shows this state.
This shows a state in which every other W atom on the (oo) plane evaporates to form all 6 lattice defects, resulting in a C(2X2) structure.

The present invention utilizes this firm C(2×2) structure to increase the unevenness of the tip and obtain a high-intensity, minute-diameter beam.

That is, a W single crystal thin wire is electrolytically polished and subjected to edge field evaporation treatment to sharpen the radius of curvature of the tip to 5000 [A] to 300 [A] to 300 [A], thereby shaping the wire so that the (100) plane appears at the tip of the chip. By performing electric field evaporation with the conditions relaxed, this surface is made to have an uneven surface fC (2 x 2) structure, which increases the surface unevenness in terms of fineness and generates high-intensity ions. Beamla can be increased.

(gl Effects of the Invention 7. Implementation of the Invention) As a result, it has become possible to obtain a high-intensity, minute-diameter ion beam, and it has become possible to greatly improve the efficiency of ion beam exposure.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an ion chamber, FIG. 2 is a diagram of the shape of a tungsten electrode, FIG. 3 is a lattice arrangement of tungsten atoms in the (1003 plane), and FIG. 4 is an explanatory diagram of a C (2x2) structure. In the diagram, ■ is a tungsten wire, 5 is a tungsten atom, and 6 is a lattice defect.

Claims (1)

[Claims] A high voltage is applied between the needle electrode and the extraction electrode in a high vacuum evacuated gas atmosphere 2, and a high brightness minute diameter ion beam of the gas cations is obtained from the tip of the needle electrode. In this ion beam irradiation device, a tungsten monomer is used, in which the radius of curvature of the tip with respect to the needle electrode is 5000 [A] or less, and the surface of the tip is a (Zoo) plane with a C (2X2) structure. A field ionization type ion source characterized by being composed of crystal wires.