KR101588275B1 - Micro-column having a source lens which comprises four electrodes for easy fabrication - Google Patents

Abstract

The present invention relates to a micro-electron column including a source lens of a quadrupole lens layer, and more particularly to a micro-electron column which can improve the resolution of such a micro-electron column and which is easy to manufacture.
The present invention employs an auxiliary focusing electrode to improve the characteristics of a microelectronic column to optimize the geometry and operating conditions of the source lens to adjust the size of the electron beam in the sample To thereby provide a microelectronic column having a resolution of 50 nm which is driven with a low energy of 1 keV or less

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a micro-electron column including a source lens of a quadrupole lens layer,

The present invention relates to a micro-electron column including a source lens of a quadrupole lens layer, and more particularly to a micro-electron column which can improve the resolution of such a micro-electron column and which is easy to manufacture.

A microcolumn developed for the first time in the early 1990's by IBM TJ Watson Laboratories has an electron emission source t, a source lens 10, A deflector 20 and an Einzel lens 30 as a focus lens and is an electron column having a total length of 10 mm or less.

The microelectronic column is characterized by its short length, which minimizes scattering of electrons moving within the column.

A major feature of the microelectronic column is that it allows a multi electron beam structure using an electron column of a small structure. Multi-electron columns can improve productivity, which is currently being pointed out as a disadvantage in electron beam equipment, such as CD-SEM, wafer-inspection, and electron beam lithography.

A large electron column to make an existing electron beam is fabricated with an aperture of several hundred micrometers size through which electrons can pass through mechanical processing using a metal plate. However, since a micro electron column is required to have an aperture of about several micrometers as required, it is required to finely process a hole. These problems are solved by MEMS processes using semiconductors. Among them, the source lens is an important component that not only controls the trajectory of the electron beam while the electron beam reaches the sample, but also determines the electrical characteristics of the microcolumn.

As shown in Fig. 1, the source lens 10 has the greatest influence on the electron beam characteristic of the microcolumn. A typical source lens includes an extractor S1 for inducing field emission in an electron emission source tip, an accelerator S2 for accelerating electrons, a limiting electrode S2 for filtering electrons, and a limiting aperture (S3). By applying a voltage to each electrode, an electric field is formed between the electrode plates to control the movement of the electron beam.

It is generally known that the accelerating electrode of the source lens has a larger hole size than the extraction electrode and the limiting electrode, and thus does not directly affect the characteristics of the electron beam. When different voltages are applied to the electrodes constituting the microcolumn, numerous equipotential lines (equipotential lines) as shown in FIG. 2 are formed in the aperture space by the electric field. Each of the above equipotential lines serves as an electron lens. The spacing and curvature of the equipotential lines are determined by the thickness of the electrode, the diameter of the aperture, the gap between the electrodes, and the applied voltage. Electrons passing through these electron lenses are focused or diverged as they accelerate or decelerate.

Since the structure of the source lens greatly influences the characteristics of the microcolumn, the structure of the source lens is a very important factor in the design of the microcolumn.

An auxiliary focusing electrode is interposed between an extractor (S1) and an accelerating electrode (S3) in order to improve the characteristics of a microminiature electron column. The geometry of the source lens And an operating condition is optimized to adjust the size of the electron beam in the sample, thereby providing a microelectronic column having a resolution of 50 nm which is driven with a low energy of 1 keV or less.

In addition, according to the present invention, the aperture size of the limiting electrode S3 and the extraction electrode S1 is increased by inserting a new lens layer or electrode S2s into the source lens, And aims at improving alignment of the tip (t) and the extraction electrode (S1) and increasing the number of electrons passing through the extraction electrode (S1) to improve electron beam characteristics of the microcolumn.

In order to achieve the above object, a micro-electron column of the present invention includes an electron emission source for emitting electrons, an electrostatic field electron lens for forming and controlling the electron beam, and a deflector for scanning the electron beam onto a sample Wherein the electron lens comprises: an extraction electrode for inducing the electron emission in the electron emission source; An auxiliary focusing electrode for adjusting a focusing speed of an electron beam generated from the electron emission source; An acceleration electrode for accelerating the electrons emitted by the extraction electrode; And a limiting electrode for controlling the amount and size of the electron beam by the electrons accelerated by the accelerating electrode, wherein the diameter of the limiting electrode is at least one fifth of the diameter of the auxiliary focusing electrode, And the diameter of the extraction electrode is equal to or larger than the diameter of the auxiliary focusing electrode.

In the microcolumn of the present invention, at least one of the electron emitting source, the extracting electrode, the auxiliary focusing electrode, the accelerating electrode, the electron lens including the limiting electrode, and the deflector are formed on a single silicon substrate And sequentially assembling the substrates to form a plurality of electron columns.

Further, in the microcolumn according to the present invention, the auxiliary focusing electrode is located within the range of 100 to 500 mu m from the extraction electrode and the acceleration electrode, respectively.

Further, in the microcolumn of the present invention, the deflector is disposed between the limiting electrode and the sample.

The micro-electron column having the above structure optimizes the geometrical structure and operating conditions of the source lens by additionally providing an auxiliary focusing electrode between the extraction electrode and the acceleration electrode in the source lens which has the greatest effect on the characteristics of the electron beam, Or less sub-50 nm or less resolution driven by low energy.

The electron microcolumn of the present invention has an effect that it is possible to easily fabricate the source lens array by making the diameter of the limiting electrode equal to or greater than 1/5 of the diameter of the focusing electrode.

In addition, the present invention has an effect that a plurality of micro-electro-optical columns can be easily manufactured by disposing a plurality of electrodes constituting an electro-optical column on a silicon substrate.

1 is a schematic cross-sectional view showing the structure of a conventional micro-column.
2 is a view showing the equipotential line distribution characteristic by an electric field in an aperture space in the source lens.
3 is a schematic perspective view showing a configuration of a microcolumn of the present invention.
FIG. 4 is a graph showing characteristics of a beam current density and a beam diameter in a specimen. FIG.
FIG. 5 is a graph showing the relationship between the voltage applied to the auxiliary focusing electrode S2s and the beam current characteristic of the emission tip current and the specimen according to the size of the limiting electrode of the microcolumn according to the present invention. .
6 is a graph showing the beam size and beam current characteristics of a sample according to a voltage applied to an acceleration electrode of a microcolumn according to the present invention.
7 is a schematic cross-sectional view showing a trajectory shape of an electron beam in a micro electron column according to another embodiment of the present invention.
FIG. 8 is a graph comparing electron beam sizes in a sample of a micro-electro-optical column according to an embodiment of the present invention having the configuration of FIG. 7 and a conventional micro-electro-optical column.
9 is a perspective view showing a configuration of a multi-microminiature electron column of a silicon wafer scale (Si wafer) according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings so that those skilled in the art can easily carry out the technical idea of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described with reference to the accompanying drawings, wherein like reference numerals are used to denote like elements, unless otherwise indicated.

The concept of the auxiliary focusing electrode of the present invention is such that an electron beam having passed through the extraction electrode S1 having increased size and increased in divergence is focused on the auxiliary focusing electrode S2s to form an Einzel, The electron trajectory incident on the lens is adjusted to an optimal condition.

The alignment of the lens layer (electrode) of the microcolumn is not easy because of its small diameter. In particular, the diameter of the limiting electrode is usually smaller, which makes alignment with other electrodes difficult.

The micro-sized electron column can exhibit high-resolution performance with a small beam size only if the diameters of the respective electrodes are aligned very precisely along the electro-optical axis.

Accordingly, the present invention is characterized in that the auxiliary focusing electrode S2s is added to the source lens so as to be formed of four electrodes, so that the diameter of the limiting electrode is usually larger than that of the conventional aperture. It is preferable that the diameter of the limiting electrode is larger than 1/5 of the diameter of the auxiliary focusing electrode and the diameter of the acceleration electrode is larger than the diameter of the acceleration electrode.

3 is a schematic perspective view showing a configuration of a microcolumn of the present invention. As shown in FIG. 3, the source lens 110 of the present invention includes four electrodes. Compared with the conventional source lens 10, the auxiliary focusing electrode S2s is added between the extraction electrode S1 and the accelerating electrode S2.

In order to confirm the effect of the S2s electrode in the micro-electron column structure according to the present invention as shown in FIG. 3, a conventional micro-column (configuration shown in Table 1 below) 15 were used for comparison. The results of the conventional electron column are shown as hollow circles and the results of the present invention as black circles.

Tip Diameter S1 diameter S2 diameter S3 diameter Tip-S1 distance S1-S2 distance S2-S3 distance Diameter / Gap (占 퐉) 0.1 5 100 2.5 50 200 400 Driving Voltage (V) -1000 -697.5 0 0 - - -

FIG. 4 is a graph showing characteristics of a beam current density and a beam diameter in a specimen. FIG. The column of the present invention is as shown in Table 2 below, the comparison column has no S2s electrode, the remaining electrode diameters are the same as those of the present invention, and the electrode distances are the same as those of the conventional column.

Tip Diameter S1 diameter S2s diameter S2 diameter S3 diameter Tip-S1 distance S1-S2s distance S2s-S2 distance S2-S3
Street Diameter / Gap (占 퐉) 0.1 50 50 50 10 50 200 200 400 Driving Voltage (V) -1000 -697.5 -800 /
Variable 0 0 - - - -

In order to realize the same conditions as those of the conventional microelectronic column, the diameter of the electron beam in the sample was observed under the condition of the aperture diameter of 10 mu m and the working distance of 2.0 mm at the same driving voltage. Here, the applied voltage of S1 was applied at -697.5 V, and the tip current was matched to 10 ㎂. In the case of the micro-electron column structure of the present invention, the beam diameter is much smaller than that of the conventional micro-column, and it can be seen that the S2s electrode greatly influences the electron beam control. That is, the auxiliary focusing electrode S2s has a great influence on the electron beam control.

FIG. 5 shows the voltage applied to the auxiliary focusing electrode S2s and the beam current characteristics at the emitter tip current and the specimen according to the size of the limiting electrode. As shown in the graph of the change of the electron beam diameter in the sample according to the voltage applied to the auxiliary focusing electrode S2s, the electron beam diameter decreases as the applied voltage of the auxiliary focusing electrode S2s increases .

However, as the voltage applied to the auxiliary focusing electrode S2s increases, the beam diameter does not decrease continuously. 5 is a graph showing a correlation between a voltage applied to the auxiliary focusing electrode S2s, a tip current, and a beam current in the sample according to the size of the limiting electrode S3.

As shown, the tip current The beam current in the sample is not largely affected by the size of the limiting electrode S3. However, when the aperture diameter of the limiting electrode S3 is 2.5 占 퐉, the dependency of the auxiliary focusing electrode S2s on the applied voltage is insignificant, S3 has an aperture diameter of 10 m, it can be seen that the control effect of the auxiliary focusing electrode S2s is clearly revealed. It can be seen that the smaller the limiting electrode S3 is, the smaller the number of electrons passing through the limiting electrode S3 is and the less the correlation with the control effect of the auxiliary focusing electrode S2s is. Therefore, if the voltage applied to the auxiliary focusing electrode S2s is appropriately adjusted, the aperture diameter of the limiting electrode S3 can be increased to about 10 mu m without decreasing the electron beam characteristic of the micro-electron column to increase the beam current. As the voltage applied to the accelerating electrode S2 or the auxiliary focusing electrode S2s increases, the beam current increases (see FIG. 5), and the beam size gradually decreases as shown in FIG.

6 is a graph showing the beam size and beam current characteristics in the sample according to the voltage applied to the accelerating electrode. As shown in FIG. 6, when the acceleration voltage S2 or the auxiliary focusing electrode S2s is applied with a specific voltage (-860 V) is applied, the beam size in the sample increases sharply. This means that when a voltage of 860 V or more is applied to the auxiliary focusing electrode S2s, the electron beam convergence in the source lens becomes too much so that a crossover occurs before the electron beam enters the Einzel lens portion, .

The introduction of the auxiliary focusing electrode S2s, which is a control electrode of a new concept, enables selection of the extraction electrode having a large bore diameter, thereby increasing the beam current and reducing the beam size in the sample, thereby improving the resolution of the microcolumn do.

FIG. 7 is a view showing a trajectory shape of an electron beam in a microelectronic column according to another embodiment of the present invention. In the source lens according to the present invention, the auxiliary focusing electrode S2s serves as a focusing electrode, And shows an ultra-small electron column which is formed using only a source lens and a deflector. Referring to Fig. 7, there is shown a trajectory path of an electron beam B in a micro-electro-optic column according to an embodiment of the present invention. First, field electron emission is induced by a strong electric field formed between the extraction electrode S1 and the electron emission tip (t), and the electron beam B is emitted from the tip t. The auxiliary focusing electrode S2s controls the focusing speed of the electron beam B passing through the extraction electrode aperture of the extraction electrode S1. At this time, a voltage is flexibly applied to the auxiliary focusing electrode S2s according to the working distance to control the focusing speed of the electron beam B. The accelerating electrode S2 accelerates electrons of the electron beam B passing through the auxiliary focusing electrode S2s. The limiting electrode S3 limits the amount and size of the electron beam B passing through the accelerating electrode aperture to a predetermined value. Thereafter, the deflector D deflects the electron beam B that has passed through the limiting electrode S3 and is scanned into the sample. Here, B 'denotes the trajectory of the electron beam emitted from the electron emission source but not reaching the actual sample.

FIG. 8 is a graph comparing electron beam sizes in a sample of a micro-electro-optical column according to an embodiment of the present invention having the configuration of FIG. 7 and a conventional micro-electro-optical column. Referring to FIG. 8, the void may be formed by the method described in Reference 1 (J. Vac. Sci. Technol. B, Vol. 7, No. 6, pp. The dark filled circle indicates the position of the auxiliary focusing electrode S2s at a position of 150 占 퐉 from the extraction electrode S1, and FIG. And the open triangle represents the case where the position of the auxiliary focusing electrode S2s is 200 μm from the extraction electrode S1 and the quadrangular square represents the position of the auxiliary focusing electrode S2s from the extraction electrode S1 250 占 퐉. The micro-electron column including the source lens of the quadrupole lens layer without such a focus lens is an example of a miniature electron column having a reduced size and simplified structure, and excellent performance. It is possible to perform the role of a miniature electron column even without a focus lens, and it is possible to make the aperture diameter of the extraction electrode and the limiting electrode, which are the main features of the present invention, Do.

In the above embodiment, it was confirmed that the limiting electrode works well even when the diameter of the limiting electrode is 10 micrometers or more. However, considering the size of the auxiliary focusing electrode and the extraction electrode, the size of the auxiliary focusing electrode is limited and the size of the auxiliary focusing electrode is reduced. Therefore, even if the size of the auxiliary focusing electrode is reduced, It is possible to operate it largely.

In addition, the diameter of the extraction electrode is made larger than the diameter of the auxiliary focusing electrode, and the electrons are focused on the auxiliary focusing electrode, thereby achieving high resolution as a sufficiently high-performance electron column. When the resolution is adjusted according to the use of the microelectronic column, the diameter of the extraction electrode and the limiting electrode can be increased by controlling the auxiliary focusing electrode.

9 is a perspective view showing a configuration of a multi-microminiature electron column of a silicon wafer scale (Si wafer) according to an embodiment of the present invention. 9, a multi-electron optical column of a silicon wafer scale includes an electron emission source t, an extraction electrode S1, an auxiliary focusing electrode S2s, an acceleration electrode S2, a limiting electrode S3 A deflector D and a focus lens F are formed on a single silicon wafer substrate using a micro electro mechanical system (MEMS) process, and the silicon substrates are sequentially assembled to form a plurality of miniature electron columns .

t - electron emission source tip S1 - extraction electrode
S2s - auxiliary focusing electrode S2 - accelerating electrode
S3 - Restriction electrode

Claims (4)

1. An electron microcolumn comprising an electron emitting source that emits electrons, at least one electrostatic field electron lens that forms and controls the electron beam, and a deflector that scans the electron beam,
Wherein the microelectronic column comprises a source lens as an electrostatic field electron lens for forming and controlling electrons emitted from the electron emission source as a beam,
Wherein the source lens comprises: an extraction electrode for guiding the electron emission in the electron emission source; An auxiliary focusing electrode for adjusting a focusing speed of an electron beam generated from the electron emission source; An acceleration electrode for accelerating the electrons emitted by the extraction electrode; And a limiting electrode for controlling the amount and size of the electron beam by the electrons accelerated by the accelerating electrode,
The diameter of the extraction electrode is larger than the diameter of the limiting electrode, and
Wherein the diameter of the limiting electrode is between one fifth or more of the diameter of the auxiliary focusing electrode or 10 micrometer,
Characterized in that the micro-column comprises a plurality of columns. The method according to claim 1,
And the diameter of the extraction electrode is equal to or larger than the diameter of the auxiliary focusing electrode. The method according to claim 1,
The electron emission source; At least one electron lens; And a deflector; A plurality of electron-optical columns are formed on a single silicon substrate, and the plurality of electron-optical columns are formed by sequentially assembling the substrates. 4. The method according to any one of claims 1 to 3,
Wherein the microelectronic column comprises an electron emitter, the source lens, and a deflector, wherein the deflector is disposed between the limiting electrode and the sample.

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