JP3353535B2 - Focused ion beam processing equipment - Google Patents

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 processing apparatus and, more particularly, to failure analysis of a semiconductor fine element or the like, process evaluation of a manufacturing process thereof, device correction by cutting or connecting wiring of a defective element, light or X-ray beam. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focused ion beam (FIB) processing apparatus equipped with a gas supply nozzle for assist deposition or assist etching for correcting a line mask defect or the like.

[0002]

2. Description of the Related Art FIG. 2 schematically shows an assist deposition of a conventional FIB processing apparatus. Such a device is known, for example, from Japanese Patent Publication No. 1-243354. According to this apparatus, the sample 4 is scanned and irradiated with the FIB 3 in which the ions generated from the ion source 1 are focused by the ion optical system 2. Secondary electrons or secondary ions emitted from the sample 4 are detected by the charged particle detector 6. The display device 8 uses a CRT
A signal synchronized with the FIB scanning signal generated by the ion optical system controller 7 is input to the scanning signal input, and an intensity signal detected by the charged particle detector 6 is input to the luminance signal. Ion Microscope, short for S
IM). When assist deposition is performed, the gas blowing device 9 controls the temperature of the gas material storage unit and the like, and controls the valve for releasing and stopping the gas from the gas supply nozzle 10. This apparatus is of course capable of sputtering using only FIB. The SIM image is used for positioning of a processing area, processing monitoring, and confirmation of processing completion.

In the assist deposition, a gas molecule for deposition (for example, tungsten hexacarbonyl: W (CO) ₆ gas) adsorbed on a sample surface is decomposed by ion irradiation to form a non-gaseous substance (for example, tungsten). : W). W, M
By employing a gas material containing o, Al, Pt, Au and the like, it is also possible to form these metal films on the deposited film.

On the other hand, in the assist etching, the gas molecules for etching (for example, xenon fluoride: XeF ₂ ) adsorbed on the sample surface (for example, Si surface) are decomposed by ion irradiation to accelerate sputter etching of the sample. Is an etching method. This decomposition reaction is a chemical reaction, and it is necessary to select an etching gas suitable for the sample material whose etching speed is to be increased.

The speed of assist deposition and assist etching is determined by simultaneous / repeated reaction of gas adsorption and dissociation reaction by ion irradiation. Therefore, it is necessary to sufficiently increase the gas molecule flux. Therefore, it is necessary to set the gas supply nozzle 10 near the sample surface. However, if it is too close, when a sample with a different surface height is moved in a plane, the nozzle tip comes into contact with that surface,
The nozzle and sample may be damaged. A typical set value from the sample surface to the tip of the nozzle is 100 to 300 μm. The inside diameter of the nozzle is as thin as 0.5 to 1 mm (here, the optical axis of the FIB device is taken in the height direction, and a right angle plane is called a horizontal plane. Therefore, when the FIB optical axis is set to be horizontal) Is different from the horizontal plane based on the direction of gravity.)

The conventional method of setting the nozzle height has been performed as follows. First, a plurality of samples having different sample heights are classified into the same height. Next, the sample holder is pulled out from the sample chamber of the FIB processing apparatus into the atmosphere, and a sample having a certain height is mounted. Finally, the excess or deficiency in height to the tip of the nozzle is eliminated by adjusting movement using the height adjustment mechanism attached to the sample holder (in the atmosphere, the sample stage may be pulled out, including the sample stage. The excess or deficiency of the height to the nozzle tip is eliminated by the adjustment movement using the height adjustment mechanism of the sample stage.) The confirmation of the movement amount has been performed in correspondence with the movement amount of the optical microscope itself in the height direction by utilizing the shallow depth of focus of the optical microscope.

[0007]

This method has the following problems. That is, simultaneous loading of samples having different heights on the sample holder (including the sample stage) and sequential loading of the sample holder into the sample chamber cannot be performed sequentially. For a sample, such as a package sample, in which the periphery of the observation site is high, the tip of the nozzle cannot be guided to the vicinity of the site by plane movement of the sample stage in the sample chamber.

SUMMARY OF THE INVENTION An object of the present invention is to simplify a method of setting the nozzle tip with a desired value away from the sample surface with respect to various sample surfaces having different heights, and to improve the usability of the FIB processing apparatus. .

[0009]

In order to solve the above-mentioned problems, the distance between the tip of the nozzle and the sample surface is set based on the voltage value of the electrostatic lens and the distance from the electrostatic lens to the beam focusing point. did. Preferably, the lens voltage value of the electrostatic lens that focuses the FIB and the FIB
A relational expression with the distance to the focal point is obtained in advance, and thereafter, using this relational expression, the position and the distance between them are obtained from the lens voltage value when FIB is focused on the nozzle tip or the sample surface. Conversely, the lens voltage values corresponding to the desired positions are individually set, and the positions of the individual SIM images can be adjusted until just the focus is obtained.

[0010]

According to the above-mentioned means, the position of the tip of the nozzle or the surface of the sample can be easily known from the lens voltage value, and can be easily moved and adjusted to a desired position.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

FI equipped with gallium liquid metal ion source
In the B processing observation device, a processing beam having an ion acceleration voltage of 30 kV, a beam diameter of 0.05 to 1 μm, and a processing beam of 10 to 30 nm is provided by a two-stage electrostatic lens optical system of focusing and objective.
And a thin beam for SIM image observation. In the sample chamber, the nozzle 10 has the FIB 3 on the sample 4.
It is attached so as to face the irradiation part. There are two types of nozzle tip positions, evacuation position and working position,
The position can be set and adjusted from outside the sample chamber (atmospheric pressure side). Here, the retreat position is a high nozzle position set so that the tip of the nozzle does not come into contact with the sample even when a sample having a high sample surface is loaded. The working position is the position of the tip of the nozzle at the time of assist deposition or assist etching. The position is several tens μm away from the FIB optical axis in the plane direction, and 200 to 300 μm away from the sample surface in the height direction. It is. This work position requires fine movement in the XYZ directions at the adjustment stage,
Fine adjustment within the range of ± 500 μm is possible.

The relational expression [Vo = f (Z), Z = g (Vo)] between the lens voltage Vo of the objective lens in the observation beam and the distance Z from the objective lens to the beam focal point is obtained in advance by calculation. It has been confirmed experimentally that it matches well. For the functions f (Z) and g (Vo), polynomials up to the third order of the variables Z and Vo are sufficient in the range of Z = 5 to 20 mm. In addition, the height (see FIG. 1) of the outer diameter of the nozzle at the working position in the direction of the FIB axis at the nozzle tip is determined in advance for Zn. In the present embodiment, the set distance from the sample surface to the tip of the nozzle is 0.3 mm and Zn = 0.8 mm.

FIG. 3 shows the degree of blur of the SIM image with respect to the change in Z. This figure is a SIM image (16 μm square) when Z is changed from 6 to 6.3 mm, that is, when the increment ΔZ of Z is changed from 0 to 0.3 mm. The image of ΔZ = 0 is just focused. Sample is 4M-D
This is a RAM device. It was experimentally confirmed that the positional accuracy by the method of visually searching the sample height position of the just focus from the SIM image was ± 30 μm or less including individual differences. This accuracy is the desired nozzle height setting of 30.
The value was ± 10% or less as compared with 0 μm, indicating that this method was effective.

In the following, it is assumed that the temperature setting of the deposition or etching gas material storage has been completed, and the operation procedure for setting the nozzle height will be described. In the description, a portion of the sample surface to be deposited or etched is referred to as a “processed portion”.

(1) FIB is set to the observation beam, and SIM
Image observation is set to the maximum scanning range (about 1 mm square).

(2) The sample holder on which the sample is mounted is loaded into the sample chamber.

(3) After confirming that the nozzle is at the retracted position, the processing position of the sample is moved to a plane just below the FIB, and the height of the sample stage is lowered to a position sufficiently lower than the eucentric position of the sample stage. Lower the height. Here, the eucentric position is a height position when the tilt axis is common to any tilt angle in the tilt of the sample.

(4) The sample tilt is repeated while observing the SIM image in the maximum scanning range, and the height of the sample surface is adjusted to the eucentric position of the stage so that the sample image does not escape.

(5) The FIB is just focused on the sample surface, and the lens voltage value Vo of the objective lens at that time is set to Vo.
s, and the Z value Zs at that time is obtained from Zs = g (Vos).

(6) The sample stage is moved downward by about 5 mm.

(7) Lens voltage value Vow [= f (Zs + Z) for focusing the beam on the top of the nozzle tip at the working position
n + 0.3 mm)], and the lens voltage is set there.

(8) Move the nozzle from the retracted position to the working position.

(9) In the SIM image of the maximum scanning range (1 mm square) (see FIG. 4), the tip of the nozzle is several tens of meters from the center of the image.
The nozzle position is finely adjusted on the XYZ axes so as to be apart by μm and the SIM image becomes a just focus image. For the final just focus image, increase the image magnification (to increase the FIB scanning range by 200
Confirm to narrow down to about μm square).

(10) The lens voltage Vo is set to Vos again.

(11) While monitoring the SIM image, the sample stage is slowly moved to a eucentric position about 5 mm above to obtain a just-focused SIM image.

Since the nozzle height can be set to a desired value by the above operation procedure, a deposition or etching operation is performed thereafter. Furthermore, samples having different heights (<5 mm) are mounted on the sample stage, and when working on these samples, the procedure returns to the step (3) and the steps (3) to (11) may be repeated.

In this embodiment, the function Vo = f
Although the computer used for controlling the FIB processing apparatus is used to convert between Z and Vo using (Z) and Z = g (Vo), a table prepared in advance may be used.

The same technique as that of the present invention can be applied to work using a focused beam such as an electron beam or a laser beam.

[0030]

According to the present invention, the surface of the sample and the tip of the nozzle can be set at desired heights in the FIB processing apparatus.
Conversely, these height positions directly below the beam can also be measured. Accordingly, it is possible to easily set the nozzle tip with a desired value away from the sample surface with respect to various sample surfaces having different heights, and without taking the sample out of the sample chamber (atmospheric pressure) for each sample. Therefore, the work of assist deposition and assist etching can be made highly efficient. In addition, the usability of the FIB processing apparatus by this operation was greatly improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a method for setting a nozzle height in a focused ion beam processing apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of assist deposition or assist etching in a focused ion beam processing apparatus.

FIG. 3 shows the degree of blur of a SIM image (16 μm square scanning) with respect to a change in the height position (Z) of the sample surface in the example of the present invention. When ΔZ = 0, FIB is just focused on the sample surface.

FIG. 4 is an explanatory diagram of a SIM image (600 μm square scanning) used for setting a nozzle to a work position.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ion source part, 2 ... Ion optical system part, 3 ... Focused ion beam (FIB), 4 ... Sample, 5 ... Sample holder, 6 ...
Charged particle detector, 7: ion optical system control unit, 8: display device, 9: gas blowing device, 10: gas supply nozzle.

Continuation of front page (56) References JP-A-6-20639 (JP, A) JP-A-1-243354 (JP, A) JP-A-8-17385 (JP, A) JP-A-2-205683 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01J 37/30 H01J 37/305 H01L 21/302

Claims (2)

(57) [Claims] 1. A focused ion beam processing apparatus for processing by irradiating the sample through the electrostatic lens the focused ion beam, and the distance to the focal point of the focused ion beam from the voltage value of the electrostatic lens Lens Relational expression or relational table of
Between the nozzle for supplying the gas determined in advance and the sample
Based of the distance, the tip of the nozzle for supplying the gas
Distance equivalent to the surface of the sample, it changes the focal point of the beam
A focused ion beam processing apparatus , comprising: a controller configured to set the lens voltage so as to perform the operation. 2. The position of a gas supply nozzle of a focused ion beam processing apparatus provided with a gas supply nozzle for blowing a gas to a sample when the sample is processed by irradiating the sample with a focused ion beam via an electrostatic lens. In the adjusting method, the step of focusing the focused ion beam on the surface of the sample or the tip of the gas supply nozzle, and changing the focus based on a distance between the tip of the gas supply nozzle and the sample determined in advance. Setting the lens voltage so as to perform the adjustment, and adjusting the position of the gas supply nozzle or the sample so that the tip of the gas supply nozzle or the sample surface is focused. A method for adjusting the position of a gas supply nozzle of a focused ion beam processing apparatus.