JPH10241588A - Focused ion beam processing method and apparatus - Google Patents

Abstract

(57) [Problem] In a focused ion beam processing apparatus, the beam is not blurred even if the ion beam current value is changed, and the moving trajectory of the beam remains even when a plurality of locations are continuously processed. Instead, an apparatus that can perform three-dimensional processing and copy processing is realized. In addition, the apparatus is capable of simultaneously stabilizing the ion beam current. A container for holding a plasma other than a reference electrode for applying a voltage to the plasma and an ion extraction electrode for extracting ions from the plasma is provided. The inner wall is covered with an insulator, and an ion extraction voltage is applied between the reference electrode 4 and the ion extraction electrode 5 so that the absolute value of the potential difference is 0 to 100 V and the absolute value of the ion beam current is 0 to 1
A means for continuously controlling to 0 μA was used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focused ion beam processing method and apparatus using a plasma ion source.
The present invention relates to a focused ion beam processing method and apparatus suitable for performing fine processing without damaging a sample.

[0002]

2. Description of the Related Art Focused ion beams are used in a wide variety of fields such as maskless ion implantation, ion exposure, mask correction, wiring correction, and analysis in the semiconductor manufacturing field. A liquid metal ion source is used for mask correction and wiring correction, and a duoplasmatron ion source is used in the analysis field.

In the field of semiconductor manufacturing, in each step of ion implantation, lithography, etching and the like in a manufacturing line, it is important to manage whether each step satisfies an expected specification in order to improve a manufacturing yield. It has become very important. Therefore, inspection is performed outside the production line after the semiconductor is completed, and the inspection information is fed back to the production line. The beam diameter of an ion beam that can be used for such applications is 0.1 μm or less, and an ion beam mainly extracted from a liquid metal ion source using gallium is narrowed down to 0.1 μm or less by a focusing lens. The focused ion beam is irradiated on the surface of the inspection object, secondary charged particles emitted from the irradiation area are detected, and brightness modulation is performed on the bright spot scanning on the monitor in synchronization with the scanning signal of the ion beam. By applying, it is possible to observe the unevenness of the irradiation surface and the difference in the material as an image (secondary charged particle image).

[0004]

At present, in a focused ion beam apparatus widely used as a tool for micromachining and observation, a liquid metal ion source of gallium is used as an ion source. The liquid metal ion source is LMIS (Liqu
id Metal Ion Source)
As shown in FIG. 2, the operation principle is as follows. Gallium 26, which is a liquid at room temperature, is stored in a reservoir 27, supplied to an ion emitter 28 by using a capillary phenomenon, and a strong electric field is applied to the ion emitter 28 and the extraction electrode 34, thereby causing the Emitter 2
The gallium 26 at the tip 8 is drawn out, the tip becomes an acute angle, and the gallium 26 is ionized by the strong electric field at the tip to emit gallium ions 29. FIG. 3 shows the relationship between the extraction voltage and the ion current. When the threshold voltage is reached, the tip of the ion emitter 28 becomes acute and the ions 29 begin to be rapidly emitted. After the extraction, if the extraction voltage is lower than the threshold voltage, the ions 29 continue to be extracted, but the ion emission stops at a certain voltage. In order to control the ion current value, it is necessary to control the extraction voltage on the order of kV. For this reason, when the ion current is changed by the extraction voltage, the condition of the focusing lens system that focuses the ion beam changes, which causes a problem that the beam is blurred.

[0005] As described above, since it is difficult to control the ion beam current value in the focused ion beam apparatus using the liquid metal ion source, the beam trajectory is greatly changed so as not to hit the object to be processed when processing and observation are not performed. I was ranking. Therefore, if such blanking is performed during machining, there is also an effect on the machining method that a trajectory of the beam 22 moving to the blanking position 30 as shown in FIG. 4 remains on the machining surface.

In order for the liquid metal ion source to operate stably, the gallium 26 from the reservoir 27 must be supplied stably to the tip of the ion emitter 28, but the gallium 26 on the surface of the emitter 28 is oxidized or extracted. The material sputtered by gallium from the electrode 34 or the like adheres to the emitter 28, and the operation becomes unstable, which has been a problem.

Accordingly, a first object of the present invention is to provide a method of controlling an ion beam current without affecting the beam focusing conditions in focused ion beam processing, and a processing method using the same.

Another object of the present invention is to provide a method for stabilizing the operation of an ion source for a focused ion beam.

[0009]

In order to achieve the above object, a focused ion beam processing method for processing a sample by using an ion beam generated by using a plasma ion source is described in which a plasma is generated inside a plasma ion source. A focused ion beam processing method characterized by changing conditions of an ion beam extracted from the plasma ion source by controlling an extraction voltage for extracting ions from the generated plasma to the outside of the plasma ion source; and did.

In order to achieve the above object, a focused ion beam processing apparatus includes a sample chamber having a sample table on which a sample is placed, and a plasma chamber having plasma generating means for generating plasma therein. An ion source, ion beam extracting means for extracting ions from the plasma generated inside the plasma ion source to the outside of the plasma ion source, and a voltage applied to the ion beam extracting means. Extraction voltage control means for changing the conditions of extraction of the ion beam, irradiation means for focusing the extracted ion beam and irradiating the sample placed on the sample table inside the sample chamber means, Secondary particle detecting means for detecting secondary particles generated from the sample by the irradiation, and secondary particles detected by the secondary particle detecting means. Constructed by a display means for displaying the secondary particle image on the sample surface.

A plasma ion source is used as an ion source for a focused ion beam, and an inner wall of a plasma holding container other than a reference electrode for applying a voltage to the plasma and an ion extraction electrode for extracting ions from the plasma is covered with an insulator. A means for applying an ion extraction voltage between the ion extraction electrodes and continuously controlling the absolute value of the ion beam current from 0 to 10 μA within the absolute value of the potential difference of 0 to 100 V was used.

(Embodiment 1) Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a diagram schematically showing a method of controlling an ion beam current in a focused ion beam apparatus using a plasma ion source. In FIG. 1, 1 is a plasma, 2 is an electron, and 3 is an ion. Reference numeral 4 denotes a reference electrode, and reference numeral 5 denotes an ion extraction electrode. On the other hand, in the ion optical system, 6 is a focusing lens, 7 is Aligner Stigma, 8 is Blanca,
9 denotes a Faraday cup, 10 denotes a deflector, and 11 denotes an objective lens. Reference numeral 19 denotes an object to be processed;
Is the stage. The power and control of the ion optical system are as follows: 14 is an acceleration power supply, 15 is a first power supply of a focusing lens, 16 is a second power supply of a focusing lens, 18 is an aligner / stigma, a blanker,
A controller for controlling and measuring the Faraday cup and the deflector, 20 is an objective lens power supply, and 17 is a computer for beam control. Further, 12 amplifiers and 13 isolation circuits are involved in controlling the ion beam current.

Although not shown in FIG. 1, the plasma holding vessel of the plasma ion source for generating the plasma 1 therein includes a reference electrode for applying a voltage to the plasma and an ion extraction electrode for extracting ions from the plasma. The other portion of the inner wall surface of the plasma holding container that is in contact with the generated plasma is covered with an insulator over substantially the entire surface.

Next, the operation will be described with reference to FIG. An inert gas or a reactive gas is filled with a constant pressure in a plasma holding container in which the inside surface is evacuated to a vacuum while the inside is evacuated, or a constant pressure is applied by using a vacuum pump. Let it be 1. Gas molecules are ionized in the plasma 1 to include electrons 2 and ions 3. Here, the acceleration power supply 14, the first power supply 15 for the focusing lens, the second power supply 16 for the focusing lens, the controller 18 and the power supply 20 for the objective lens are operated by the beam control computer 17, and the plasma 1 is applied to the reference electrode 4 and the ion extraction electrode 5. After the ions are extracted from the opened holes and passed through the focusing lens 6, the aligner-stigma 7, the blanker 8, the Faraday cup 9, and the deflector 10, the ion beam 22 is focused on the surface of the workpiece 19.

After the ion beam is focused, the blanker 8
Evacuates the beam by performing blanking with
The stage 21 is moved so that the focused ion beam 22 can be irradiated on a portion to be processed on the substrate 9. Furthermore, in order to obtain accurate coordinates of the processing position, the secondary charged particles 24 emitted from the surface by scanning the focused ion beam 22 with the deflector 10 on the surface of the processing object 19 are detected by the secondary charged particle detector 23. Detect and observe the secondary charged particle image on the processing object 19 surface. The operator determines the coordinates of the processing position by observation, and scans the focused ion beam 22 at the processing position at a constant scanning speed for a scanning time corresponding to the processing amount.
Conventionally, when this scanning is completed, the trajectory is changed by the blanker 8 to a position where the focused ion beam 22 does not hit the processing target 19, and the processing is completed. On the other hand, in the present invention, since the control of the ion beam current can be performed according to the principle shown in FIG. 5, it is not necessary to change the ion beam trajectory by the blanker 8 after the scanning is completed. The current is set to 0 to end the processing. As a result, unnecessary processing traces during blanking do not remain on the processing target 19.

The principle of controlling the ion beam current will now be described with reference to FIGS. The plasma 1 in FIG. 1 has a potential of Vex + Vamp, which is the sum of the voltage Vex applied from the acceleration power supply 14 by the reference electrode 4 and the output voltage Vamp of the amplifier 12. The current drawn from the plasma 1 is determined by the I-Vamp characteristic shown in FIG. 5, and when the voltage of Vamp = V0 at which the drawn current becomes 0, when Vamp <V0, the ion extraction electrode 5 Since the potential becomes higher, the electrons 2 in the plasma 1 are extracted and the electron beam current Ie flows, and Va
When mp> V0, the potential of the ion extraction electrode 5 becomes lower than that of the plasma 1, so that the ions 3 in the plasma 1 are extracted and the ion beam current Ii flows. The voltage required to change from an electron beam to an ion beam may be 100 V or less, depending on the state of the plasma, and is typically 10 V or less.
It is about 30V. Therefore, the control voltage of the ion beam current does not need to be on the order of kV as in the prior art, and is 100 V
Because of the following low voltage, the beam was not blurred.

In this embodiment, the ion extraction voltage applied between the reference electrode and the ion extraction electrode is set to 0 to 1
By changing the control voltage of the ion beam current by changing it between 00 V, the ion beam current can be continuously controlled from 0 to 10 μA.

In this embodiment, as described above, the ion beam current is controlled by changing the ion extraction voltage applied between the reference electrode and the ion extraction electrode.
Furthermore, the ion beam current can also be controlled by changing the power applied by the external power supply, thereby changing the density of the plasma generated inside the plasma holding container.

(Embodiment 2) When the ion beam current control means of the present invention is used, the ion beam current value can be changed during the focused ion beam processing. Therefore, processing as shown in FIGS. 7 to 11 can be performed. The processing method will be described below.

First, a method of continuous machining at a plurality of locations will be described with reference to FIGS. FIG. 6 shows a conventional processing method for a plurality of locations using a focused ion beam having no ion beam current control means. In conventional processing, when two processings as shown in the figure are performed consecutively, the trajectory of the focused ion beam moving as a processing mark remains after processing the first processing position and then moving to the second processing position. I have. On the other hand, when the ion beam current control means of the present invention is used as shown in FIG. 7, the voltage Vamp of the amplifier 12 is controlled to
After processing the first processed portion, the focused ion beam current is set to 0 when the first processed portion is moved to the second processed portion, so that no trace of the movement remains. As described above, if the current control means of the present invention is used, unnecessary beam trajectories do not remain on the processing object 19 even when a plurality of locations are continuously processed.

Further, by further finely controlling the ion beam current, for example, as shown in FIG. 8, the ion beam current value at the first processing location and the ion beam current value at the second processing location can be changed. It is also possible to arbitrarily set the machining depth at the machining location.

FIG. 9 shows a three-dimensional processing in which the processing depth is different in one processing area by continuously changing the ion beam current value in one processing area by finer control of the ion beam current. It became possible to do.
If this is used, for example, it is easy to flatten the processed surface by controlling the ion beam current based on the depth information of the cross section of the processing target having a cross section as shown in FIG.

Further, as shown in FIG. 11, a certain area is scanned by the focused ion beam 22, and the data of the secondary charged particle image is recorded in the control computer 17, and is stored in a place different from the place where the observation was made. If the ion beam current is controlled with the same ion beam scanning signal and the Vamp signal based on the recorded data, it is possible to create surfaces having exactly the same shape. Furthermore, if the scanning area is enlarged or reduced, a surface having an enlarged shape or a surface having a reduced shape of the original shape can be created.

(Embodiment 3) The instability of the supply of gallium from the reservoir to the tip of the ion emitter, which is observed in the liquid metal ion source, is a problem because it directly affects the processing accuracy of the focused ion beam. Was. This problem can also be easily solved by the ion beam current control means of the present invention. For example, the amount of ions entering from the plasma 1 is monitored as a current by the ammeter 25 in FIG. 1 and the output voltage V of the amplifier 12 is controlled by the control computer 17 so that this current value becomes constant.
By controlling the amp, a stable ion beam current can always be obtained.

Further, by providing a simple feedback stabilizing circuit 32 as shown in FIG. 12, a stable ion beam current can be obtained without using a control computer.

[0027]

As described in detail above, the intended object has been achieved by the present invention. That is, according to the present invention, a plasma ion source is used as an ion source for a focused ion beam, and the inner wall of a container holding plasma other than a reference electrode for applying voltage to the plasma and an ion extraction electrode for extracting ions from the plasma is insulated. Since a means for continuously controlling the ion beam current value by covering with an object and applying an ion extraction voltage between the reference electrode and the ion extraction electrode was used, the beam was not blurred even when the ion current value was changed.

Further, since the ion beam current value can be changed during the scanning of the focused ion beam, unnecessary beam trajectories do not remain on the workpiece even when a plurality of locations are continuously processed. Furthermore, by continuously changing the ion beam current value in the processing region, three-dimensional processing with different processing depths in one processing region could be performed.

Monitoring the ion beam current value;
Alternatively, by providing a feedback stabilization circuit, the focused ion beam current could be stabilized.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a control method of a focused ion beam processing apparatus using an ion beam current control means for explaining a first embodiment of the present invention.

FIG. 2 is a diagram schematically showing a conventional liquid metal ion source.

FIG. 3 is a diagram showing a relationship between an extraction voltage and an ion current of a conventional liquid metal ion source.

FIG. 4 is a view for explaining blanking traces in focused ion beam processing using a conventional liquid metal ion source.

FIG. 5 is a diagram for explaining an ion beam current control method of the present invention.

FIG. 6 is a view for explaining a continuous processing method at a plurality of locations in a focused ion beam processing using a conventional liquid metal ion source.

FIG. 7 is a view for explaining a method of continuously processing a plurality of locations in focused ion beam processing using the ion beam current means of the present invention.

FIG. 8 is a view for explaining a method of processing a plurality of portions having different processing depths in focused ion beam processing using the ion beam current means of the present invention.

FIG. 9 is a view for explaining a three-dimensional processing method in focused ion beam processing using the ion beam current means of the present invention.

FIG. 10 is a diagram showing an example in which a processing surface in focused ion beam processing using the ion beam current means of the present invention is flattened.

FIG. 11 is a diagram illustrating a copy processing method in focused ion beam processing using the ion beam current means of the present invention.

FIG. 12 is a diagram showing a feedback stabilization circuit for stabilizing an ion beam current using the ion beam current means of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Plasma 2 ... Electron 3 ... Ion 4 ... Reference electrode 5 ... Ion extraction electrode 6 ... Focusing lens 7 ... Aligner / Stigma 8 ... Blanker 9 ... Faraday cup 10 ... Deflector 11 ... Objective lens 12 ... Amplifier 13 ... Isolation circuit 14 ... Acceleration power supply 15 ... First power supply for focusing lens 16 ... Second power supply for focusing lens 17 ... Computer for beam control 18 ... Controller for controlling and measuring the aligner, stigma, blanker, Faraday cup and deflector 19 ... Workpiece 20 ... Objective lens Power supply 21 Stage 22 Focused ion beam 23 Secondary charged particle detector 24 Secondary charged particle 25 Ammeter 26 Gallium 27 Reservoir 28 Ion emitter 29 Gallium ion 30 Blanking position 31 Surface step Total 32 ... Feedback Stabilization circuit 33: Leader power supply 34: Leader electrode

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H01L 21/3065 H01L 21/302 D (72) Inventor Norimasa Nishimura 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Pref. In the laboratory (72) Inventor Akira Shimase 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Pref.

Claims (16)

[Claims] 1. A focused ion beam processing method for processing a sample using an ion beam generated by using a plasma ion source, wherein a plasma is generated inside the plasma ion source, and ions are generated from the generated plasma. A focused ion beam processing method, wherein the condition of an ion beam extracted from the plasma ion source is changed by controlling an extraction voltage for extracting the ion beam to the outside of the plasma ion source. 2. The method according to claim 1, wherein the condition of the ion beam extracted from the plasma ion source is changed by using a reference electrode disposed inside a region where the plasma is generated inside the plasma ion source and a region where the plasma is generated. 2. The focused ion beam processing method according to claim 1, wherein the method is performed by controlling a voltage applied to an externally provided ion extraction electrode. 3. The focused ion beam processing method according to claim 1, wherein changing the condition of the ion beam extracted from the plasma ion source includes outputting and stopping the ion beam. 4. The focused ion beam processing according to claim 1, wherein changing the condition of the ion beam extracted from the plasma ion source is changing the voltage or the beam current of the ion beam. Method. 5. A plasma is generated inside a plasma ion source, and ions are extracted from the generated plasma to the outside of the plasma ion source to form an ion beam.
Focusing the ion beam to scan and irradiate a desired area on a sample, and controlling irradiation conditions of the focused ion beam according to a position on the sample to be scanned. Processing method. 6. The focused ion beam processing method according to claim 5, wherein controlling the irradiation condition of the focused ion beam includes controlling an acceleration voltage or a beam current of the ion beam. 7. A focused ion beam processing method for processing a sample with a focused ion beam generated using a plasma ion source, wherein the condition of the irradiation is controlled while irradiating the sample with the focused ion beam. A focused ion beam processing method characterized by the following. 8. The focused ion beam processing method according to claim 7, wherein controlling the irradiation condition of the focused ion beam includes controlling an acceleration voltage or a beam current of the ion beam. 9. The method according to claim 7, wherein controlling the irradiation condition of the focused ion beam includes temporarily stopping the irradiation of the ion beam on the sample.
The focused ion beam processing method described in the above. 10. A focused ion beam processing method using a plasma ion source, wherein a secondary charged particle image at a location different from a processing location is stored as data, and a secondary charged particle image already observed is stored. The same scanning signal is used to continuously change the ion beam current value based on the luminance signal of the secondary charged particle image at the processed location, and three-dimensionally process the same. A focused ion beam processing method characterized by reproducing a cross section of a shape. 11. A focused ion beam processing method using a plasma ion source, wherein a secondary charged particle image of a location different from a processing location is stored as data, and a secondary charged particle image of an already observed secondary charged particle image is stored. By increasing the period of the scanning signal and the luminance signal, and continuously changing the ion beam current value based on the signal at the processing location and processing it three-dimensionally, the uneven shape of the location where the secondary charged particle image was obtained A focused ion beam processing method characterized in that a cross section is enlarged and reproduced. 12. A focused ion beam processing method using a plasma ion source, wherein a secondary charged particle image of a location different from a processing location is stored as data, and a secondary charged particle image of an already observed secondary charged particle image is stored. By shortening the period of the scanning signal and the luminance signal, and continuously changing the ion beam current value based on the signal at the processing location and performing three-dimensional processing, the unevenness of the location where the secondary charged particle image was obtained A focused ion beam processing method characterized in that a cross section is reduced and reproduced. 13. A plasma chamber having a sample table on which a sample is placed, a plasma ion source having plasma generating means for generating plasma therein, and a plasma generated inside the plasma ion source. Ion beam extraction means for extracting ions from inside in the form of a beam to the outside of the plasma ion source, and extraction voltage control means for controlling a voltage applied to the ion beam extraction means to change conditions for extracting the ion beam. Irradiating means for converging the extracted ion beam and irradiating the sample placed on the sample table inside the sample chamber means, and detecting secondary particles generated from the sample by the irradiation. Secondary particle detection means, and display means for displaying a secondary particle image on the surface of the sample detected by the secondary particle detection means. Focused ion beam processing apparatus according to claim. 14. The ion beam extracting means includes: a reference electrode portion disposed inside a region where the plasma is generated inside the plasma ion source; and an ion extraction electrode portion disposed outside a region where the plasma is generated. Has,
14. The focusing method according to claim 13, wherein the extraction voltage control means controls a voltage applied between the reference electrode unit and the ion extraction electrode unit to change conditions for extracting the ion beam. Ion beam processing equipment. 15. The ion beam extracting means further comprises an ion beam current measuring unit for measuring a current value of the extracted ion beam, and the extracting voltage is set based on the ion beam current value measured by the ion beam current measuring unit. 14. The focused ion beam processing apparatus according to claim 13, wherein a voltage applied between the reference electrode unit and the ion extraction electrode unit is controlled by a control unit. 16. The plasma ion source according to claim 1, wherein a portion in contact with the plasma generated by said plasma generating means is covered with an insulator over substantially the entire surface except for said reference electrode portion and said ion extraction electrode portion. Claim 1.
3. The focused ion beam processing apparatus according to 3.