JPH0481300B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of 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 probe current 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 to perform ion implantation or microfabrication such as forming grooves on the sample surface. FIG. 4 is a diagram showing an example of a conventional configuration of a two-stage focused focused ion beam device. When a voltage of about 5 KV is applied between the extraction electrode 1 and the liquid metal 2, 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 passed through the objective lens 6.
After being focused by a deflector 7, it is deflected in a two-dimensional direction to irradiate a sample 8. When irradiated with an ion beam, grooves of about 200 Å are formed on the surface of the sample 8 by ion implantation along the scanning direction of the beam or by sputtering effect.

As described above, a general focusing lens beam device consists of a two-stage focusing system including a focusing lens (also called a condenser lens) and an objective lens. Then, the crossover position of the ion beam Bi (fourth
A mass separator (also referred to as an EXB mass filter) 5 and a beam blanker 9 are arranged at point a in the figure. The positions of the focusing lens 4 and the objective lens 6 are fixed. Therefore, even in the case of a two-stage focusing system, the intensities of the focusing lens 4 and the objective lens 6 are used at a certain constant value. Focusing lens 4 and objective lens 6
By changing the intensity of the ion beam (however, the ion source position and sample surface position remain unchanged), the ion beam conditions (for example, narrowing down the beam diameter, or widening the beam diameter and increasing the current beam) can be adjusted. However, there is a restriction that the crossover of the ion beam Bi must always be connected to the position of the beam blanker 9 (or the center of the mass separator 5).

The reason why the ion beam Bi crossover must be connected to the position of the beam blanker 9 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.
After applying a voltage to the blanking plate 9a, the ion beam Bi is bent in the direction of the arrow in the figure.
There is a time delay until the ion beam is completely turned off after it is cut by the blanking aperture 9b. The ion beam reaches the sample 8 even during this delay time. Bi′ in the figure indicates the ion beam that reaches the sample 8 during the delay time.

The center of deflection of the ion beam at the start of blanking is the center position of the beam blanker 9 (a in the figure).
point). Therefore, if this point a is made the object point of the lower lens (objective lens) 6, since the object point position remains unchanged, the ion beam arrival position F on the sample 8
remains unchanged. Therefore, the beam will still reach the sample 8 by an additional amount of the ion beam Bi' shown in the figure (the amount reached before the beam is completely turned off), but the arrival position F will not move, so the height will be lower. Accurate drawing becomes possible.

Here, assuming a situation where the crossover of the ion beam, that is, the object point position of the objective lens deviates from the position of the beam blanker 9, the deflection center of the ion beam and the object point position of the objective lens 6 will not match. Therefore, the beam position on the sample 8 shifts from the start of beam blanking until 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 position of the beam blanker 9 so that the center of deflection of the ion beam and the object point of the objective lens 6 overlap.

(Problems to be Solved by the Invention) By changing the strength of the focusing lens and the objective lens, not only the magnification (including angular magnification) changes, but also the lens aberration. Therefore, it is possible to change the focusing state of the ion beam and obtain a desired probe current density, probe diameter, etc.

However, changing the intensity of the objective lens causes a mismatch between the center of deflection of the ion beam and the object point position of the objective lens (ion beam crossover), so if beam blanking is performed in this state, The beam position will shift, making accurate beam drawing impossible.

In order to eliminate such a problem, it is conceivable to mechanically move the blanking plate 9a of the boom blanker 9, but such a configuration would make the device extremely complicated and would be impractical.

The present invention was developed in view of these points, and its 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. There is a particular thing.

(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. an upper and lower blanking plate provided between the lenses; and an objective lens that allows a virtual deflection center of the blanking plate to coincide with an object point position of the objective lens that coincides with crossover of the ion beam. storage means storing the relationship between each voltage applied to the blanking plate and the corresponding voltage applied to each blanking plate; plate voltage setting means for setting the voltage applied to each blanking plate; Control for determining the voltage applied to each blanking plate according to the actual applied voltage from the storage means, and controlling the plate voltage setting means so that the actual voltage applied to each blanking plate matches this value. It is characterized by comprising means.

(Function) The control means obtains the voltage applied to each blanking plate from the storage means in accordance with the actual voltage applied to the objective lens, and adjusts the voltage applied to each blanking plate so that the actual voltage applied to each blanking plate matches this value. , controlling the plate voltage setting means. As a result, even if the intensity of the objective lens changes, the virtual deflection center of the blanking plate moves to the object point position of the objective lens, and the beam drawing position on the sample does not shift during beam blanking.

(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. In the figure, 21 is a first blanking plate, 22 is a second blanking plate, and these two upper and lower blanking plates 2
1 and 22 are arranged between a focusing lens and an objective lens (not shown). Moreover, these first and second blanking plates 21 and 22 are arranged apart from each other by a predetermined distance.

23 is a first amplifier that applies a voltage to the first blanking plate 21; 24 is a second amplifier that applies a voltage to the second blanking plate 22; 25 is a blanking signal that applies a blanking signal to the first amplifier 23; The first link circuit provides variable power, and 26 is the second link circuit.
This is a second link circuit that similarly provides a variable blanking signal to the amplifier 24 of the same. 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. The amplitude level is
For example, about 50V is used. first amplifier 23
The output of the 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
One plate 2 of the blanking plates 22 of
2a, and a voltage obtained by inverting the output of the amplifier 24 by an inverter 28 is applied to the opposing plate 22b. Although not shown in FIG. 1, storage means such as a RAM is provided for storing data for aligning the center of movable deflection by the blanking plates 21 and 22 with the object point position of the objective lens. The data stored in this storage means is
Specifically, it is data showing the relationship between each voltage applied to the objective lens and the corresponding voltage applied to each blanking plate 21, 22. Although the plate voltage setting means consisting of the first and second link circuits that set the voltage applied to each blanking plate 21, 22 may be adjusted manually, in the present invention, the adjustment is performed by a control means (not shown). be done. This control means determines from the storage means the voltage applied to each blanking plate according to the actual voltage applied to the objective lens, and the actual voltage applied to each blanking plate 21, 22 matches this value. Thus, the plate voltage setting means is controlled. Note that the configuration other than the above is the same as that in FIGS. 4 and 5.

Next, the operation of the device configured in this way will be explained.

Now, the first and second blanking plates 2
Let the voltages applied to terminals 1 and 22 be V1 and V2, respectively. Here, if V1=V2, the ion beam Bi
is deflected by each blanking 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 blanking plate 21. This deflected beam is further deflected at the same rate by the second blanking plate 22 and follows a trajectory as shown in the figure. Here, 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 is defined as a.
Then, the final ion beam Bi travels straight as if it were emitted from this point a. This point a is the virtual deflection center point, and when V1=V2, the virtual deflection center point a is the upper and lower blanking plate 2.
It comes to the exact middle position between 1 and 22.

Next, the first and second blanking plates 2
When the voltages V1 and V2 applied to terminals 1 and 22 are made different, the amount of deflection at each blanking plate is different, and as a result, the virtual deflection center position a is as shown in Fig. 3 within the range between the upper and lower two blanking plates. Move as shown. A is the first blanking plate 21
When the voltage V1 applied to the second blanking plate 22 is smaller than the voltage V2 applied to the second blanking plate 22 (V1
＞V2), and b is when V1 is larger than V2 (V1
>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 blanking plates and changing the voltage applied to these plates, it is possible to obtain the same effect as if the position of one blanking plate was moved up and down. . Therefore, in the present invention, the control means determines the voltage applied to each blanking plate 21, 22 according to the actual applied voltage to the objective lens from the storage means, and applies this value to the actual voltage applied to each blanking plate 21, 22. The plate voltage setting means is controlled so that the voltages applied to the plates match.
As a result, even if the intensity of the objective lens is changed,
Since the virtual deflection center of the blanking plate automatically moves to the object point position of the objective lens, the beam drawing position on the sample does not shift during beam ranking, making it possible to draw with high precision.

Note that whether or not the virtual deflection center of the blanking plate coincides with the beam crossover position can be checked by inputting a weak WOBBLER signal to the blanking plates 21 and 22. In other words, the check can be made by applying to each plate a wobbler signal having the same voltage ratio as the voltage applied to the upper and lower blanking plates 21 and 22. (However, this applied voltage is within a range where the beam is not cut by the blanking aperture).

(Effects of the Invention) As explained in detail above, according to the present invention,
A two-stage focused focused ion beam device is equipped with two upper and lower blanking plates, and the voltage applied to each blanking plate corresponding to the actual voltage applied to the objective lens is determined from the storage means, and the actual value is added to this value. Since the plate voltage setting means is controlled so that the voltage applied to each blanking plate matches,
Even if the intensity of the objective lens changes, the virtual deflection center of the blanking plate automatically moves to the new object point position of the objective lens, and the beam drawing position on the sample does not shift during beam blanking. Therefore, no problem occurs even if the operating conditions of the objective lens are changed, so it is possible to control the probe diameter, probe current density, etc., which is extremely effective in practical use.

[Brief explanation of the drawing]

FIG. 1 is a main part configuration diagram showing an embodiment of the present invention,
Figures 2 and 3 are diagrams 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. DESCRIPTION OF SYMBOLS 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, 2
7, 28...Inverter.

Claims (1)

[Claims] 1. In a two-stage focused focused ion beam device that accelerates and focuses generated ions and irradiates them onto a sample, two stages of blanking, upper and lower, are provided between a focusing lens and an objective lens. each applied voltage to the objective lens and each corresponding blanking plate such that a virtual deflection center of the blanking plate can be aligned with the object point position of the objective lens that coincides with the crossover of the ion beam; a storage means storing a relationship between voltages applied to each of the blanking plates; a plate voltage setting means for setting the voltage applied to each of the blanking plates; A focused ion system characterized by comprising: control means for determining the applied voltage from the storage means and controlling the plate voltage setting means so that the actual voltage applied to each blanking plate matches this value. Beam device.