JPH0582479A - Focussed ion beam device - Google Patents

Abstract

PURPOSE:To enable the etching step, etc., in the path of a stable focussed ion beam current to be performed by a method wherein ions are led-out in a constant-current mode by feeding the aligner signals corresponding to the fluctuation in the leading-out voltage to the aligner between a leading-out electrode and an objective lens. CONSTITUTION:Ions are focussed by a focussing lens 130 including a leading-out electrode 101, a lens electrode 102 passing through an electrostatic aligner 103 for making the ions pass through the center of an objective lens 106. The leading-out electrode 101 is actuated in the constant-current mode. At this time, even if the leading-out voltage is fluctuated to shift the ion incoming direction from the focussing lens 130, the correction voltage signals are read-out by the characteristic curve of the fluctuated voltage and an aligner correction voltage so as to impress the aligner 103 with the aligner correction voltage comforming to said signals. Accordingly, the processing step such as the etching step using the focussed beams can be performed stably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focused ion beam (FI for short) of a fine element such as a semiconductor element.
The present invention relates to the improvement of a processing apparatus such as etching and deposition without a mask using B).

[0002]

2. Description of the Related Art FIG. 2 shows an emission ion current (I) -extraction voltage of a liquid metal ion source for generating gallium (Ga) ions.
It is a graph which shows (V) characteristic. Here, the extraction voltage is a voltage applied between the ion emitter and the extraction electrode. V
Has a threshold voltage above which I rapidly increases. In this liquid metal ion source, due to changes with time such as the flow resistance of the liquid metal flowing on the emitter surface, I-
The V characteristic curve itself is more likely to change than other ion sources. On the other hand, in the processing such as etching and deposition without mask using FIB of fine elements such as semiconductor elements,
Three conditions are required over a long period of time: a stable FIB current, a stable irradiation position, and a stable FIB diameter. By the way, the emitter, the extraction electrode, and the lens electrode (which may be a ground electrode) that form the ion source form an electrostatic lens, and if the mechanical axes of these electrodes are deviated, the extraction voltage Changes, the central axis of the emitted ions deviates, and also shifts from the optical axis of the focusing lens. As a result, the FIB irradiation position on the sample is displaced,
Further, the FIB diameter also becomes large due to blurring.

Therefore, in the conventional apparatus, as shown in FIG. 3, in order to suppress the fluctuation of the irradiation point of the FIB on the sample due to the fluctuation of the extraction voltage of the ion source, a deflection signal corresponding to the fluctuation of the extraction voltage is supplied to the deflector. There was a means to do so. However, this method has a drawback that the condition is not satisfied although the condition is satisfied.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a stable FIB current, a stable irradiation position, and a stable FIB diameter with respect to the time variation of the extraction voltage of the ion source.

[0005]

In order to solve the above-mentioned problems, ions from an ion source are extracted in a constant current mode, and an aligner signal corresponding to a change in extraction voltage is applied to the aligner between an extraction electrode and an objective lens. A means for supplying is provided.

[0006]

By the above means, the ions from the ion source are extracted in the constant current mode, and an aligner signal corresponding to the fluctuation of the extraction voltage is supplied to the aligner between the extraction electrode and the objective lens, so that the FIB It can be aligned so that the central axis passes through the center of the objective lens. As a result, a stable FIB current, a stable FIB irradiation position, and a stable FIB diameter are supplied.

[0007]

EXAMPLE An example of the present invention will be described below with reference to FIG.

Extraction electrode 1 on the emitter 100 of the ion source
When a high negative voltage is applied to 01, the ions are ejected from the emitter 100 and the focusing lens 130 (extraction electrode 10
1, lens electrode 102, and ground electrode). The focused ion beam passes through an aperture 300 that determines the beam opening angle, and further passes through an eight-pole electrostatic aligner 103 for passing the focused beam through the center of the objective lens 106.
The aligner 103 electrode has a FIB to aligner voltage.
The stigma voltage of the stigma function for correcting the lens astigmatism is superimposed. The blanker 104 turns on and off the irradiation of the FIB 120 on the sample 200, and the two-stage 8-pole electrostatic deflector 105 sets the FIB 12 on the sample 200.
The irradiation point of 0 is controlled. Secondary electron detector 10
Reference numeral 7 is for detecting secondary electrons emitted from the sample 200 by irradiation with the FIB 120, and the deposition nozzle 108 is a nozzle portion for spraying a metal gas for FIB-induced deposition such as metal onto the sample. Reservoir part 1
There are also 10.

In order to operate the device thus constructed in accordance with the object of the present invention, the following preparations are first made.
First, a variation of ± ΔVe is applied to the reference value Ve ₀ of the extraction voltage Ve applied to the extraction electrode 101, and the position variation of the FIB on the sample 200 is measured. Next, a correction voltage ΔVax of the aligner voltage for returning the fluctuation position to the original,
Measure ΔVay. This measurement is performed by a method such as observing a scanning secondary electron image on the sample surface. Figure 4
The origin 0 of the coordinates X and Y in (a) corresponds to the irradiation position on the sample when the deflection by the deflector is 0 in the reference state of the extraction voltage Ve ₀ , and the directions of the coordinates X and Y are on the sample. The moving direction of the FIB is shown. The straight line 28 shows the movement of the FIB with respect to the change in the extraction voltage Ve, and can be approximated to a straight line near the origin. FIG. 4B shows the coordinate ΔVa.
At the origin 0 of x, ΔVay, the correction voltage is 0, and the absolute value of the aligner voltage corresponds to the reference values Vax ₀ , Vay ₀ . A straight line 29 is an aligner correction voltage ΔV applied to correct the movement of the FIB with respect to the change of the extraction voltage Ve.
It is a characteristic curve showing ax and ΔVay, and can be linearly approximated near the origin.

After such pre-preparation, the FIB device is operated with the correction signal being supplied to the aligner 103.
The extraction power source controls the extraction voltage by the negative feedback loop, that is, operates in the constant current mode so that the total ion current flowing into the extraction electrode always becomes a desired set value. The FIB current used for sample irradiation is a small amount of the total ion current, and if the total ion current is constant, the FIB current is also constant. Even if the extraction voltage fluctuates and the ion emission direction from the focusing lens 130 shifts, the correction voltage signal is read from the circuit that reads the aligner correction voltage signal from the characteristic curve of the fluctuation voltage and the aligner correction voltage in FIG. 4B. The aligner correction voltage based on the correction voltage signal is applied to the aligner. As a result, the emitted beam passes through the center of the objective lens 106 and is corrected so that the FIB irradiation position on the sample does not shift and the blurring of the FIB itself is suppressed.

Strictly speaking, the change in the extraction voltage Ve changes the focal length of the focusing lens 130 because the electric field strength of the focusing lens 130 is changed. Therefore, strictly speaking, a slight blur of FIB still remains on the sample. In order to correct this, as a preparation, the lens correction voltage to be added to the lens electrode 102 corresponding to the variation of ± ΔVe from the reference value Ve ₀ of the extraction voltage Ve is measured. This measurement is also performed by a method such as observing a scanning secondary electron image on the sample surface. After such preparation, lens correction can be performed by the same method as the above aligner correction. By combining this lens correction and aligner correction, stable FIB current,
It is possible to supply a stable FIB irradiation position and a more stable FIB diameter.

[0012]

According to the present invention, it is possible to perform a stable masking process such as etching and deposition using a focused beam without a mask.
IB current, stable FIB irradiation position, and stable FI
Since it can be performed under the B diameter, high precision, high reliability, and high value-added processes can be achieved by using this for manufacturing fine elements such as semiconductor elements.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a focused ion beam apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an extraction ion current-extraction voltage characteristic curve of an ion source.

FIG. 3 is a schematic view of a conventional focused ion beam device.

FIG. 4 is a schematic diagram for explaining the operation of the device of the present invention.

[Explanation of symbols]

1 ... Lens barrel, 2 ... Ion source, 3 ... Ion beam, 4, 13
0 ... Focusing lens, 5,200 ... Sample, 6 ... Emitter, 7
... control electrode, 8 ... ground electrode, 9 ... DC high voltage power supply, 1
0, 11 ... Aperture, 12 ... Current-voltage conversion circuit, 13 ... Differential amplification circuit, 14 ... Reference circuit, 15 ... High-frequency transmission circuit, 1
6 ... Variable power source, 17 ... Stepping transformer, 18, 1
9 ... Interface, 20, 21 ... Data reading circuit, 22, 23 ... DA conversion circuit, 24 ... Deflection signal amplifier, 26, 27 ... Deflection electrode, 28 ... Characteristic curve showing movement of FIB with respect to change of extraction voltage Ve (origin (Linear approximation in the vicinity), 29 ... F with respect to change in extraction voltage Ve
Characteristic curves showing aligner correction voltages ΔVax and ΔVay applied to correct the movement of IB (linear approximation in the vicinity of the origin), 100 ... Ion emitter, 101 ... Extraction electrode, 102 ... Intermediate electrode, 103 ... Aligner, 104
... Blanker, 105 ... Deflector, 106 ... Objective lens,
107 ... Secondary electron detector, 108 ... Depot nozzle, 11
0 ... Gas reservoir for deposit, 120 ... FIB, 300 ... Movable diaphragm.

Claims (2)

[Claims] 1. A focused ion beam is formed by focusing ions emitted from an ion source by a plurality of stages of electrostatic lenses, the beam optical axis is aligned by an aligner between the lenses, and the focused beam is deflected by a deflector. In a focused ion beam apparatus for scanning on a sample surface, in order to prevent the irradiation point of the focused ion beam on a sample from varying with the variation of the extraction voltage of the ion source, an aligner according to the variation of the extraction voltage is used. A focused ion beam device comprising means for supplying a signal to the aligner. 2. In order to prevent the irradiation beam of the focused ion beam on the sample from being blurred due to the fluctuation of the extraction voltage of the ion source, a focusing lens signal according to the fluctuation of the extraction voltage is sent to the focusing lens. The focused ion beam device according to claim 1, further comprising means for supplying.