JPS62177849A - Focusing ion beam device - Google Patents

Abstract

PURPOSE:To enable the control of the probe bore, the probe current, and the like, by furnishing two layers of upper and lower blanking plates to a focusing ion beam device of two-stage focusing type, and making the value of voltage applied to those blanking plates variable. CONSTITUTION:Two layers of upper and lower blanking plates 21 and 22 are furnished between the focusing lens and the object lens, and these blanking plates 21 and 22 are arranged to separate at a specific distance each other. When the values of the voltage V1 and the voltage V2 to apply to the first and the second blanking plates 21 and 22 are differentiated, the deflecting amount of the both plates are also different, and the imaginary deflection center a is moved between the both plates. By controlling the focusing lens and the object lens to make the imaginary deflecting center position a come to the focus of the focusing lens and the focus of the object lens, the image drawing position does not change owing to the beams to reach to the sample until the blanking is perfectly off, when the blanking is on even though the crossover of the ion beams is converted. Therefore, a highly accurate image drawing is realized.

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to a focused ion beam device, and more specifically, the present invention relates to a focused ion beam device, and more specifically, even if the ion probe is set to an arbitrary probe diameter and N flow density, the ion beam is not drawn by the ion beam during blanking. The present invention relates to a focused ion beam device that prevents positional deviation from occurring.

(Prior Art) A focused ion beam device is a device that accelerates and focuses generated ions to irradiate a sample, and performs microfabrication such as ion implantation or forming grooves on the sample surface. FIG. 4 is a diagram showing an example of the conventional configuration of a two-stage focused focused ion beam device. 5KV between extraction electrode 1 and liquid metal 2
When a certain voltage is applied, ions are generated from the tip of the liquid metal 2. The generated ion beam Bi is accelerated by an accelerating tube 3, then narrowed by a focusing lens 4, and ions of different masses are separated by a mass separator 5.

The ion beam Bi from which unnecessary ions have been removed by the mass separator 5 is focused by an objective lens 6 and then deflected in a two-dimensional direction by a deflector 7 to irradiate the sample 8 . When the sample 8 is irradiated with the ion beam, ions are implanted into the surface of the sample 8 along the scanning direction of the beam, or about 200 grooves are formed due to the sputtering effect.

In this way, a general focused ion beam device uses a focusing lens (also called a condenser lens) and an objective lens.
It consists of a stage focusing system. Then, a mass separator (EX
(also referred to as a B mass filter) 5 and a beam blanker 9 are arranged.

The positions of the focusing lens 4 and the objective lens 6 are fixed. Therefore, even though it is a two-stage focusing system, the intensities of the focusing lens 4 and objective lens 6 are used at a constant value. By changing the intensities of the focusing lens 4 and the objective lens 6 (however, the ion source position and the position of the sample surface remain unchanged), the ion beam conditions (for example, narrowing down the beam diameter or increasing the beam diameter) can be adjusted. Although it is possible to change the ion beam (such as making it a large current beam), the ion beam [
There is a restriction that a 3i crossover must be connected.

The reason why the crossover of the ion beam 3i must be connected to the beam blanker 9 position is as follows.

This will be explained using FIG. In the figure, 9a is a blanking plate, and 9b is a blanking aperture for blocking passage of the ion beam. By applying a voltage to the planking plate 9a, the ion beam Bi is bent in the direction of the arrow in the figure, and the ion beam is cut by the planking aberration t9b to completely transform the ion beam A)
There is a time delay before this happens. The ion beam reaches the sample 8 even during this delay time. 3i in the diagram
L indicates the ion beam reaching the sample 8 during the delay time.

The center of deflection of the ion beam at the start of blanking is located at the center of the beam blanker 9 (point a in the figure). Therefore, if this point a is made the object point of the lower lens (objective lens) 6, the position of the object point remains unchanged, so the ion beam arrival position fiF on the sample 8 remains unchanged. Therefore, the ion beam Bi' in the figure (the amount reached before the beam is completely turned off) will reach the sample 8, but since the arrival position F does not move, highly accurate drawing is possible. It becomes possible. However, if the crossover of the ion beam deviates from the position of the beam blanker 9, the center of deflection of the ion beam and the object point position of the objective lens 6 will no longer match. Therefore, the position of the beam reaching the sample 8 is shifted between the start of beam blanking and the time when the beam is completely turned off, making it impossible to perform highly accurate drawing. Therefore, as described above, the ion beam crossover is connected to the beam blanker 9 position so that the deflection center of the ion beam and the object point of the objective lens 6 overlap.

(Problem to be solved by the invention) By changing the strength of the focusing lens and objective lens,
In addition to changing the magnification (including angular magnification), the lens aberration also changes, so the focusing state of the ion beam changes, and the probe current density, probe diameter, and current value can be adjusted by 1q to suit the purpose. However, since the crossover (center of deflection) of the ion beam no longer matches the object point of the objective lens, the beam position reaching the sample shifts during beam blanking, making accurate beam drawing impossible. . In order to eliminate such a problem, the planking plate of the beam blanker 9 may be mechanically moved. However, the mechanical movement method makes the device extremely complicated and is not practical.

The present invention has been made in view of these points, and
The purpose is to realize a focused ion beam device in which the beam drawing position does not shift during beam blanking even if the strengths of the two lenses are changed.

(Means for Solving the Problems) The present invention solves the above-mentioned problems in a two-stage focusing type focused ion beam device that accelerates and focuses generated ions and irradiates them onto a sample. Two planking plates, upper and lower, are provided between the lens and the planking plate, and the voltage applied to these planking plates is varied so that the virtual deflection center of the planking plate can be made to coincide with the object point position of the objective lens. It is characterized by:

(Function) In the present invention, a two-stage -F limit blanking plate is provided between a focusing lens and an objective lens, and the voltage applied to these blanking plates is varied.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of main parts showing an embodiment of the present invention.

The configuration of other parts is assumed to be the same as the embodiment shown in FIGS. 4 and 5. In the figure, 21 is a first planking plate, 22 is a second planking plate, and these two planking plates 21 and 22, upper and lower, are arranged between a focusing lens and an objective lens (not shown). There is.

Moreover, these first and second planking plates 21
．． 22 are arranged apart from each other by a predetermined distance.

23 is a first amplifier that applies voltage to the first planking plate 21; 24 is a second planking plate 2;
2 is a first link circuit that applies a variable blanking signal to the first amplifier 23; 26 is a first link circuit that applies a variable blanking signal to the second amplifier 24; This is the second link circuit. As shown in the figure, the blanking signal is a pulse signal that turns blanking on when it is at a high level and turns off blanking when it is at a low level. For example, about 50V is used as the voltage level. The output of the first amplifier 23 is applied to one plate 21a of the first blanking plate 21, and a voltage obtained by inverting the output of the amplifier 23 by an inverter 27 is applied to the opposing plate 21b.

As the inversion voltage, for example, when the voltage applied to the plate 21a is +50V, the inversion value -50V is used. Similarly, the output of the second amplifier 24 is applied to one plate 22a of the second blanking plate 22, and the voltage obtained by inverting the output of the amplifier 24 by the inverter 28 is applied to the opposing plate 22b. There is.

The operation of the device configured as described above will be explained as follows.

Now, let the voltages applied to the first and second blanking plates 21 and 22 be Vr and V2, respectively.

Here, assuming Vl-V2, the ion beam 3i is deflected by each planking plate 21, 22 and follows a trajectory as shown by the solid line in FIG. That is, the ion beam is first deflected by the first planking plate 21. This deflected beam is further transferred to the second planking plate 2.
2, it is deflected at the same rate and follows a trajectory as shown in the figure.

Here, if a is the point where a straight line extending from the second bending point K in the opposite direction along the beam trajectory intersects with the optical axis Z, then the final ion beam 3i travels straight as if it were emitted from this point a. This point a is the virtual deflection center point, and Vs=Vz
In this case, the virtual deflection center point a is located exactly in the middle of the upper and lower planking plates 21 and 22.

Next, when the voltages Vt and V applied to the first and second planking plates 21 and 22 are made different, as a result of the deflection point being different for each planking plate, the virtual deflection center point fia becomes different between the upper and lower two stages. Move within the range between the planking plates as shown in FIG. (a) is the case where the voltage V+lfi applied to the first planking plate 21 is smaller than the voltage V2 applied to the second planking plate 22 (Vt<V2), and (b) is the case where ■1 is greater than v2 The cases (Vl > V2) are shown respectively. It can be seen that the larger the applied voltage, the more the ion beam is deflected. In this way, by providing upper and lower planking plates and changing the voltage applied to these plates, it is possible to produce the same effect as if the position of one planking plate was moved up and down. can.

Therefore, the focusing lens and objective lens are controlled so that these virtual deflection center point positions become the focusing lens of the focusing lens and the object point of the objective lens. In this way, even if the ion beam crossover changes, the writing position will not change due to the beam reaching the sample by the time the beam is completely turned off when blanking is turned on. Accurate drawing becomes possible.

Note that whether or not the blanking virtual object point position matches the beam crossover position can be checked by inputting a weak W0BBLER signal to the blanking plates 21 and 22. In other words, a waver signal having the same voltage ratio as that applied to the upper and lower blanking plates 21 and 22 is applied to each plate (however, this applied voltage is within a range where the beam is not cut by the blanking aperture).
. If the blanking virtual object point position is the virtual deflection center)
If the crossover position coincides with that of the sample, the probe position on the sample surface remains unchanged as described above. Here, the voltages applied to the upper and lower plates can be varied to an arbitrary ratio by providing a link circuit. Link circuit 25 in the diagram
．． 26, it can be set to any value.

Furthermore, in the above-mentioned embodiment, the ratio of the voltages applied to the upper and lower plates was manually adjusted so that the virtual deflection center and the object point position of the objective lens coincided. The relationship between each voltage applied to the objective lens and the ratio is determined in advance and stored in a RAM or the like, and the relationship between the voltages applied to the objective lens and the above-mentioned upper and lower plates is calculated based on the data read from the RAM in accordance with the data representing the voltage applied to the objective lens. The ratio of applied voltages may be controlled to automatically match the virtual deflection center with the object point position of the objective lens.

(Effects of the Invention) As described above in detail, according to the present invention, a two-stage focused focused ion beam device is provided with two upper and lower blanking plates, and the value of the voltage applied to these blanking plates 1. By varying this, the apparent position of the planking plate can be changed by electrical operation. Therefore, conventionally it was not possible to change the operating conditions of the focusing lens and objective lens, but this allows the user to control the probe diameter, probe current, etc., without causing any problems even if the crossover position created by the focusing lens is changed. becomes possible, and the practical effect is extremely large.

[Brief explanation of drawings]

FIG. 1 is a main part configuration diagram showing an embodiment of the present invention, FIG.
FIG. 3 is a diagram showing the trajectory of the ion beam, FIG. 4 is a diagram showing an example of the conventional configuration of a focused ion beam device, and FIG. 5 is a diagram showing the trajectory of the ion beam. 1... Extraction electrode 2... Liquid metal 3... Accelerator tube 4... Focusing lens 5... Mass separator 6... Objective lens 7... Deflector 8
...Sample 9...Beam blanker 9a...Blanking plate 9b...Blanking aperture 23.24...Amplifier 25.26...Link circuit 27.28...Inverter patent applicant Japan Denshi Co., Ltd. Agent: Patent attorney: Fujiji Ijima (1 person) Figure 3 (a) (b) Vl < V2
Vl > V2 Fig. 4 8; Sample 9; Beam blanker angle 5 Fig. 8; Sample 9F Beam planker

Claims (1)

[Claims] In a two-stage focused focused ion beam device that accelerates and focuses the generated ions and irradiates them onto the sample, two upper and lower planking plates are provided between the focusing lens and the objective lens, and the voltage is applied to these planking plates. A focused ion beam device characterized in that the virtual deflection center of the planking plate can be made to coincide with the object point position of the objective lens by varying the voltage applied to the focused ion beam.