JPH0644468B2 - Slit for charged particle beam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is used in the fields of semiconductor industry, medical care, biotechnology, etc., to analyze the physical properties and composition of minute regions by using high-energy charged particle beams, fine processing, etc. The present invention relates to an improved structure of an objective slit of a device that performs

(Prior Art) When a huge amount of information is processed by a computer, it is required to increase the storage capacity and the processing speed. Therefore, development of high integration of IC is progressing from LSI to VLSI and to three-dimensional IC. With this,
Individual elements and wirings thereof are extremely miniaturized / multilayered, and extremely shallow regions from the surface are being used. I like this
In the development of C and process research, it is extremely important to analyze the atomic distribution in the microscopic region. For that purpose, the Rutherford backscattering method with a resolution of 1 μm or less using a focused ion beam of high energy (MeV) is used. Analytical methods such as (RBS) and particle excitation X-ray method (PIXE) are effective.

FIG. 4 shows an example of a general configuration of a high energy charged particle (ion) beam device. The ion beam is focused and irradiated as follows. That is, the electrostatic accelerator
The ion beam (d) emitted from the ion source (b) of (a) and accelerated by the accelerator (c) is shaken at a predetermined angle (usually 15 ° or more) by the deflection analysis electromagnet (e) to select the ion species and energy. After being narrowed down to several tens of μm by the objective slit (f), it passes through a drift space of 2 to 5 m, enters into two or three quadrupole electromagnet lenses (g) and is focused, and the sample chamber (h) The backscattered ions that connect the spots on the target (measurement sample) (i) inside are detected by the detector (j).
(k) is a coil of the deflection analysis electromagnet.

The distance from the objective slit (f) to the quadrupole electromagnet lens (g) is called the object plane distance, and the distance from the lens (g) to the target (i) is called the image plane distance. It has the function of reducing and projecting the aperture of the objective slit (f) onto the target (i) at a reduction ratio approximately equal to the ratio of two distances. By the way, since the reduction ratio is about 1/5 to 1/30, in order to obtain the diameter of 1 μm as the minimum beam spot, the beam should be the objective slit.
In (f), it is necessary to reduce the diameter to 5 to 30 μm, and 1 μm is required as the movement accuracy of the edge of the slit.

As the conventional slit, it is convenient to use a plate having a minute hole through which the beam passes, but the beam diameter cannot be changed. In the application of local analysis of minute areas and micromachining, it is generally necessary to arbitrarily change the size of the beam spot. Therefore, the wedge width and the metal cylindrical edge are opposed to each other from four directions to change the slit width. A mechanism for controlling the shape of the passing beam is adopted. In the conventional slit, a wedge-shaped edge is attached to the tip of a precision drive mechanism such as a micrometer head, and the opening width is estimated from the scale of the micrometer head at each edge. FIG. 5 (a) is a front view showing an example of a slit having an electric drive adjusting mechanism section using a piezoelectric element instead of the micrometer head. A pair of knife-shaped edges (l) or a fifth
An arm in which a pair of wedge-shaped edges shown in the vertical side view in Fig. (B) are supported by flexible joints (m).
Attached to the tip of (n) and facing each other, adjust the applied voltage of the piezoelectric element (p) behind each to adjust the slit width between the wedge-shaped edges (l) through which the ion beam (q) passes indicated by the arrow. It is supposed to be set.

(Problems to be Solved by the Invention) (A) In the above-described conventional slit, when the slit is completely closed to find a position where the opening width is zero, the surface flatness of the wedge-shaped or cylindrical edge is incomplete. Due to its nature (it is inevitable that unevenness and inclination of about μm exist in terms of working accuracy), even if the edges are in contact with each other, there is a partial gap, so the ion beam leaks and the zero point cannot be clearly determined. If the zero point cannot be determined, it is impossible to accurately set the opening width on the order of μm. In addition, if the edges are brought into contact with each other so as to forcefully close them, this may cause excessive load on the edge tip or the high-precision drive mechanism, causing deformation of the edge tip and rattling of the drive mechanism. Become. After all, in the conventional technique, the zero point cannot be satisfactorily determined practically. Therefore, it is impossible to set and control the required opening width.

(B) It is estimated that the amount of heat that hits the tip of the edge of the slit in the ion beam to generate heat is several W or more. Since the edge is placed in a vacuum, all this heat is transferred to the arm or column that supports the edge. In the prior art, since the wedge-shaped or cylindrical edge is supported by the arm portion and / or the column portion, the change in the slit opening width caused by the thermal expansion of this portion becomes a nonnegligible amount. In fact, in the conventional slit, a change in the current of the ion beam due to a change in the order of several to ten and several μm is observed during use.

(C) In the conventional slit, since the opening width is set by independently operating two facing edges, it is necessary to set the opening width with two times on both sides to set the opening width with the opening center fixed. Need operation. Further, when it is desired to set only the opening center position with the opening width fixed while adjusting the axes of the beam and the optical system, the operation is required twice on both sides, and the operability is also poor.

(Means for Solving the Problems) Problems of the conventional objective slit which adversely affects the function of the high energy charged particle beam device are as follows (I).
(II) Reasonably solved or reduced by the present invention which adopts the means of (III).

That is, the slit for a charged particle beam of the present invention has, as an overall configuration, an objective slit used in an apparatus for performing physical property / composition analysis of a minute region, fine processing, etc. by using a high energy charged particle beam, (I) A pair of wedge-shaped, knife-shaped, or cylindrical edges that face each other to form a slit gap are arranged in the upstream and downstream directions of the charged particle beam with a slight offset, and (II) the wedge that forms the slit gap. (3) Opposing a cooling water passage mechanism for guiding cooling water to just below the edge and passing it in the arm portion and / or the column portion for supporting the precision drive mechanism portion by supporting the edges of the mold, knife type or cylindrical type respectively, and (III) The step motors of the precision drive mechanism drive the forward and backward movements of the pair of edges,
The control is performed by two systems of pulse generators, an opening width control unit and an opening center position control unit.

(Operation) Each of the means (I), (II), and (III) of the present invention brings about an effect by the following operations, and in combination, they can focus the charged particle beam highly accurately and stably. It is possible to supply a slit having excellent operability.

(I) Opposing edges are arranged slightly offset in the upstream and downstream directions of the beam, so when the aperture width is narrowed, the edges are touched until they pass through the complete closure and overlap from the beam upstream. The slit can be closed without being forced. Even if there is some imperfections on the edge surface due to this margin, the zero point position can be accurately determined by monitoring the passing ion beam, so that the opening width of several μm can be set accurately thereafter. . The presence of this margin also avoids the risk of overloading the edge and precision drive mechanism during zero point calibration.

(II) The heat input to the edge is removed immediately below it, and the cooling water circulates inside the arm and / or column that supports the edge, so there is no temperature gradient in these parts, and there is a slit due to the effect of thermal expansion. The change in the opening width is suppressed.
Therefore, the opening width does not depend on the ion beam current and is always kept in a stable state.

(III) Since the slit opening width and the opening center position are controlled by different control systems and the control purpose is achieved by one operation, the operability becomes very good.

(Example) Hereinafter, the slits for a charged particle beam of the present invention are
The preferred embodiment of the figure will be described in detail to clarify its characteristics. FIG. 1 is a vertical sectional side view showing the structure of a pair of edges of this embodiment as a representative of the lower part because the upper part and the lower part are equal, and FIG. 2 shows the pair of edges in a completely closed state. FIG. 3 is a partially enlarged vertical sectional side view showing the relative positional relationship of FIG. 3 and FIG. 3 is an arrangement wiring diagram showing the configuration of the control system of the charged particle beam slit of the present invention.

As shown in FIG. 1, in this embodiment, a pair of cylindrical upper and lower edges (1) and (1) form a slit slit having an opening width (W) between which the charged particle beam line (BL) is sandwiched. It is installed so as to be vertically opposed so as to be translated in the direction of the central axis (X) (X) perpendicular to the beam line (BL), but in the present invention, the center of the edge (1) (1) The axes (X) and (X) are arranged so as to be displaced back and forth by a slight displacement distance (ε), for example, 1 mm in the upstream and downstream directions of the beam line (BL).

Each cylindrical edge (1) is made of a heavy metal such as M ₀ so that it is not easily damaged by ion irradiation and has little forward scattering.
A columnar arm (3) that is held by (2) and extends along the central axis (X).
Or it is attached to the tip of the pillar. The arm part (3) is made of stainless steel with a double pipe structure, and the vacuum duct wall (4)
And is sealed by an O-ring (5) at the penetrating portion and is guided to move back and forth. The arm part (3) has a cooling water passage mechanism inside the cooling water inlet (6) and the outlet (7) on the atmosphere side, and the cooling water flowing from the inlet (6) holds the inner pipe inside the metal fitting. It flows in the direction of (2), turns back there, returns in the outer pipe, flows out from the outlet (7), and circulates. In this way, the arm portion (3) is not given a temperature gradient over its entire length, the heat amount due to the heat received from the ion beam at the edge (1) is efficiently discharged, and the length change due to expansion does not occur.

Also, the arm part (3) is on the atmospheric side,
It is drivingly connected to the step motor (10) through the translational conversion mechanism (8) and the coupling (9), and these constitute a precision drive mechanism section. The edge (1) advances in the direction of the beam line (BL) by the forward rotation of the step motor (10) in the clockwise direction (cw), and retracts in the opposite direction by the reverse rotation of the counterclockwise direction (ccw).

In the present invention, one edge (1) is displaced from the facing edge by a distance (ε) as in the previous term, so that both edges (1) and (1) move forward as shown in FIG. It is possible to approach and reach a state where it crosses the beam line (BL) and overlaps in the front-rear direction. In this state, both edges do not hit each other with solid contact, and the ion beam can be completely closed, so that the slit The position of the opening center can be easily determined.

FIG. 3 shows an example of the configuration of the control system of the present invention, in which motor drivers (11) of the step motors (10) facing each other are provided.
(11) are respectively connected to four pulse generators (14) via a forward rotation OR element (12) and a reverse rotation OR element (13), and each pulse generator 1 (14) is open / closed / opened. And the operation switches (15) are connected to each other so that the function of upward / downward movement of the opening center can be achieved. The signals are also connected to the opening width display counter (16) and the opening center display counter (17) to display the respective values.

By pressing one of the four switches (15) in this circuit system, the slit adjustment and setting can be easily operated.
For example, the first opening width opening switch (15) from the top of Fig. 3
When is pressed, the pulse from the pulse generator (14) connected to it is input to the reverse rotation (ccw) of the upper and lower motor drivers through the OR element for reverse rotation, whereby the step motor (10)
Step (10) reverses stepping, and edges (1) and (1) move backward with the opening center left unchanged to open the opening width. Similarly 2
When the second opening width closing switch is pressed, the upper and lower step motors both rotate normally (cw), and the edges (1) and (1) move forward without changing the opening center to sandwich the opening width. When the third open center raising switch is pressed, the upper step motor reverses (cc
w), the edge rises, the lower step motor rotates forward (cw), and the edge rises, and the opening width between the edges (1) and (1) remains unchanged, and the opening center moves upward. When the fourth opening center lowering switch is pressed, the upper step motor rotates forward and its edge lowers, and the lower step motor reverses and its edge lowers, and the opening width between edges (1) and (1) is changed. The center of the opening shifts downward as it is. It is not necessary to alternately operate the upper and lower drive parts for each of these operations, and they are performed in a single operation.

(Effects of the Invention) As described above, according to the charged particle beam slit of the present invention, the zero point position is accurately determined by monitoring the transmitted ion beam current even if the shape of the edge surface is imperfect. it can. And the risk of overloading the edges and the precision drive mechanism during this zero point calibration is avoided. As a result of the determination of the zero point, an opening width of several μm can be adjusted and set with high accuracy. Moreover, this opening width control is performed by an operation separate from the adjustment setting operation of the opening center, and the purpose of each adjustment setting can be achieved even with one operation, so both operations are very easy to operate. Further, the change due to the thermal expansion of the arm portion is suppressed, and the opening width does not depend on the ion beam current and is always kept in a stable state, so that accurate measurement can be performed.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view showing a charged particle beam slit according to a preferred embodiment of the present invention with a lower portion as a representative and a partially omitted upper portion. FIG. 2 is a partially enlarged vertical sectional side view of the edge in a completely closed state. FIG. 3 is an arrangement wiring diagram showing an example of the configuration of the control system, FIG. 4 is a diagram showing a general arrangement of the high energy charged particle beam device of the prior art, and FIG. FIG. 5B is a partially enlarged vertical sectional side view of an example of the slit, which is a front view showing an example of the slit of the technology. (1) ... cylindrical edge, (2) ... edge holding metal fittings, (3) ... columnar arm, (4) ... vacuum duct wall, (5) ... O ring, (6) ...
Cooling water inlet, (7) ... Cooling water outlet, (8) ... Rotation / translation conversion mechanism, (9) ... Coupling, (10) ... Step motor, (11)
... motor driver, (12) ... OR element for forward rotation, (13) ... OR element for reverse rotation, (14) ... pulse generator, (15) ... operation switch, (16) ... open width display counter, (17) ... Opening width center display counter, (BL) ... Charged particle beam line, (w) ... Opening width, (ε) ... Deviation distance, (x) ... Central axis line, (cw) ... Clockwise direction, (ccw) ... Counterclockwise Circumferential direction, (a) ... electrostatic accelerator, (b) ... ion source, (c) ... accelerating tube, (d) ... ion beam, (e) ... deflection analysis electromagnet, (f) ... objective slit, (g ) ...
Quadrupole magnet lens, (h) ... Sample chamber, (i) ... Target, (j) ... Detector, (k) ... Coil, (l) ... Edge, (m)
… Flexible joint, (n)… arm, (p)… piezoelectric element, (q)… ion beam.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akio Arai 2-4-4 Nakajima-cho, Suma-ku, Kobe-shi, Hyogo (56) References JP-A-64-3948 (JP, A) JP-A-57-50755 ( JP, A) JP-A-56-111040 (JP, A)

Claims (1)

[Claims] 1. An objective slit for use in an apparatus for performing physical property / composition analysis of minute regions, fine processing, and the like using a high-energy charged particle beam, (I) a pair of wedge-shaped members forming slit gaps facing each other. ,
The positions of the knife-shaped or cylindrical-shaped edges are arranged in the upstream and downstream directions of the charged particle beam with a slight offset, and (II) Support the wedge-shaped, knife-shaped, or cylindrical-shaped edges that form the above-mentioned slit gap, respectively. A cooling water passage mechanism is provided in the arm portion and / or the column portion that is coupled to the precision driving mechanism portion to guide the cooling water to just below the edge and pass therethrough. (III) The pair of facing edges are moved forward and backward respectively. A slit for a charged particle beam, characterized in that it is driven by a step motor of, and its control is performed by a pulse generator of two systems of an opening width control section and an opening center position control section.