JPS632320A - Corerection for deflecting distortion in focused ion beam - Google Patents

Abstract

PURPOSE:To accurately measure the deflecting distortion of a focused ion beam by deflecting the beam to be scanned on an X-marker, Y-marker, measuring the distortion by obtained electric signals, and correcting a deflecting voltage to be applied to a deflecting electrode to correct the distortion of the beam. CONSTITUTION:Deflecting voltages Xi, Yi are respectively applied to X-and Y-deflecting electrode plates 4a, 4b and 5a, 5b to deflect a focused ion beam (a), and scanned on an X-marker 2 and a Y-marker 3. Thus, the markers 2, 3 generate secondary electron signals, which are detected by a second electron detector 6, amplified by an amplifier 7, and applied to a computer 8. After a distortion parameter is determined on the basis of the deflecting distortion amount of the focused ion beam (a) measured in the computer 8, the values are introduced into an analog type distortion correcting circuit 9, and corrected deflecting voltage values X0, Y0 are generated from X-, Y-deflecting voltage generators 10, 11. The signals are applied to the plates 4a, 4b and 5a, 5b to correct the scanning of the beam (a).

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for correcting deflection distortion in a focused ion beam.

(Prior Art) In recent years, maskless ion implantation equipment has been developed and used for manufacturing semiconductor devices. In this maskless ion implantation equipment, ion beam writing is performed on a semiconductor substrate by deflecting the ion beam. things are being done.

In order to perform this ion beam drawing with high precision, it is necessary to make the ion beam diameter fine and to eliminate deflection distortion of the ion beam.

(Problem to be solved by the invention) However, in order to deflect an ion beam, a deflection voltage is usually applied to an X-direction deflection electrode plate and a Y-direction deflection electrode plate around the path of the focused ion beam, and the focused ion beam is However, in this electrostatic deflection system, due to electric field distortion, the deflection field 1-
Deflection distortion of pincushion-like distortion or barrel-shaped distortion occurs irreversibly.
Therefore, ion beam lithography using conventional ion implanters has a limit in terms of accuracy.

In order to eliminate this drawback, it has conventionally been common practice to modify the shape of the deflection electrode itself, or to use other poles such as 8 or 16 poles. There were many difficulties in manufacturing accuracy and installation due to legal regulations.

(Means for Solving the Problems) In order to solve the above problems, in the present invention, the focused ion beam is deflected by applying a deflection voltage to the deflection electrode to deflect the focused ion beam.
The marker and the Y marker are scanned, and the deflection distortion of the focused ion beam is measured from the electric signal obtained thereby,
This paper proposes a method for correcting deflection distortion of a focused ion beam in which the deflection distortion of the focused ion beam is corrected by correcting the deflection voltage applied to the deflection M and the pole based on the measured amount of deflection distortion of the focused ion beam. be.

Here, as the X marker and Y marker for scanning the focused ion beam, grooves (marker group lines) are etched in a parallel line pattern at regular intervals in the X and Y directions, as shown in FIGS. 1A and 1H. When using the marker, a focused ion beam is scanned across the groove formed on the marker in a direction perpendicular to the groove.

During scanning, the focused ion beam generates a secondary electron signal that becomes a pulse when it passes the rising and falling edges of the groove, or the focused ion beam is measured by measuring the pulse interval of this secondary electron signal. It is possible to accurately measure the deflection distortion of

In this case, the deflection distortion of the resulting focused ion beam can be roughly divided into pincushion-shaped and barrel-shaped deflection distortions, and in the case of pincushion-shaped deflection distortion, barrel-shaped deflection distortion that cancels out this pincushion-shaped deflection distortion By superimposing the , it becomes a linear deflection line,
On the other hand, in the case of barrel-shaped deflection distortion, a linear deflection line can be obtained by superimposing a pincushion-shaped deflection distortion that cancels this distortion, but in this invention, the deflection distance and the deflection voltage are in a corresponding relationship. Therefore, after determining the deflection distortion of the focused ion beam as described above, a deflection voltage corresponding to the deflection distortion that cancels out this deflection distortion is applied to the deflection electrode to correct the deflection distortion of the focused ion beam. It is something to do.

The deflection voltage applied to the deflection electrode is determined by the following formulas (1) and (2) based on the deflection distortion of the focused ion beam measured as above.
It is possible to define more.

X, =X, (1±Y, "-1'S) --・--(1)
Yo=Yt(1fXi"-B) --・--(2) Here, X,, Y are the deflection voltage values in the X direction and Y direction applied during measurement, and X,, Y, are the values after correction. add X
There are deflection voltage values in the direction and Y direction, and if the deflection voltage to be corrected and added is pincushion type, the sign in the formula should be a positive sign, and 1
m shall be selected as an arbitrary integer of mal according to the shape of the measured deflection distortion of the focused ion beam, and the correction coefficient B is selected as an arbitrary decimal number according to the size of the measured focused ion beam. .

On the other hand, in the case of a modified deflection voltage or a barrel shape, the sign in the formula is a negative sign, and m is an arbitrary number selected from m<1 depending on the shape of the measured deflection distortion of the focused ion beam. and the correction coefficient B is selected as an arbitrary decimal number depending on the size of the measured focused ion beam.

The distortion parameters and signs in equations (1) and (2) selected in this way are added to, for example, an analog correction circuit, and the deflection voltage corrected by the analog correction circuit is applied to the deflection electrode to generate a focused ion beam. This is to correct deflection distortion.

(Effects of the Invention) In summary, according to the present invention, distortion of ion beam deflection, which is a problem in devices using focused ion beams such as maskless ion beam devices, and the accompanying positional changes in the ion beam diameter can be accurately corrected. According to the present invention, the deflection distortion of the ion beam can be corrected based on the well-measured measurements, and the present invention does not require the use of a deflection electrode with a complicated structure for removing deflection distortion, which is conventionally used in general. It is possible to accurately correct the deflection distortion of a focused ion beam using a simple method, and therefore it is possible to perform high-precision, high-quality writing using a focused ion beam using a simple method.

(Example) Examples of this invention will be shown below.

FIG. 3 shows an embodiment of the present invention.
An X marker 2 and a Y marker 3 are arranged side by side on the surface, and two X deflection electrode plates 4a, 4b and two Y markers are placed on the operation table 1.
Deflection electrode plates 5a and 5b are also provided.

For example, as shown in FIG. 1A, the X marker 2 is
It is constructed by forming approximately 1,200 parallel grooves at equal intervals in the Y direction in a square of 1.2 mm in length and width, and the Y marker 3 is formed by forming approximately 1200 parallel grooves in a square of 1.2 mm in length and width at equal intervals in the X direction, as shown in FIG. 1B, for example. It is constructed by forming approximately 1,200 zero-parallel grooves on the surface.

1゛Scan the Y marker 3.

As a result, a secondary electron signal is generated from the X marker 2 and Y marker 3 as described above, or this secondary electron signal is detected by the secondary electron detector 6, further amplified by the amplifier 7, and applied to the computer 8. do.

In the computer 8, the deflection distortion amount of the focused ion beam a is measured based on the secondary electron signal, and based on the measured deflection distortion amount, the sign, m, and correction coefficient i of the above equations (1) and (2) are determined.
! ! l! Determine distortion parameters such as B.

Figure 2 shows an example of measuring the deflection distortion of the focused ion beam a when the focused ion beam a is sequentially scanned upward on the X marker in Figure 1A. Deflection distortion can be seen.

Figure 4A shows an example of correction using equations (1) and (2) when m is 1 and correction coefficient B is 10%, and Figure 4B is an example of correction using formulas (1) and (2) when m is 1 and correction coefficient B is 10%.
This is an example of correction when the correction coefficient is 10%.

Based on the amount of deflection distortion of the focused ion beam a measured in the computer 8, the rows of equations (1) and (2) in FIG. 5 show an analog deflection distortion correction circuit used in this embodiment. +2a and 12b are distortion conversion circuits, 13a and llb
14a and 14b are 31-node circuits for correction amounts, and 15a and 15b are addition circuits.

In the analog deflection circuit, the levels of the X and Y signals input to the X input terminal 16a and the Y input terminal 16b are adjusted, and the X signal is set to x, and the X signal is set to Y.

The level-adjusted X signal X is passed through the distortion conversion circuit 12b to the JX
1', and in the primary multiplex 13b x, 1
By integrating m and level-adjusted Y signal Y, Y, X,
'' is obtained, and the adjustment circuit 14b multiplies this integrated value by the correction coefficient B to obtain BY, X, ''', and the adder circuit 15b adds or subtracts this integrated value to Y. Then Y, ±
B-Y,
Next, the multiplex 13a integrates Y, s and The circuit 15a adds or subtracts this integrated value from X to obtain X,±B-X,Y,''.

The deflection voltage in the X direction thus modified is generated by the X deflection voltage generator 10 and the deflection voltage in the Y direction is generated by the Y deflection voltage generator 11. - Accurate correction of deflection distortion can be achieved by a simple method without using a commonly used deflection electrode with a complicated structure for removing deflection distortion.

[Brief explanation of drawings]

Figure 1 is a plan view of the marker used in this invention.
Figure A shows an X marker, Figure 1B shows a Y marker, and Figure 2 shows an example of strain measurement when a focused ion beam is scanned over the same X marker. FIG. 3 is a schematic diagram showing a focused ion beam correction system showing an embodiment of the present invention;
This figure shows an example of correcting deflection distortion of a focused ion beam when distortion parameters such as m and correction coefficient B in (2) are appropriately selected. In this case, FIG. 4B shows the case where m is 2 and the correction coefficient is IH. FIG. 5 is a diagram showing an example of an analog deflection correction circuit used in this embodiment.

Claims (1)

[Claims] In a method in which a focused ion beam is deflected by applying a deflection voltage to a deflection electrode, the focused ion beam is deflected and scanned over an X marker and a Y marker. The deflection distortion of the focused ion beam is measured from an electrical signal, and the deflection voltage applied to the deflection electrode is corrected based on the measured amount of deflection distortion of the focused ion beam, thereby correcting the deflection distortion of the focused ion beam. A method for correcting deflection distortion in a focused ion beam, characterized by: