JP2834466B2 - Ion beam device and control method thereof - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focused ion beam processing method, and in particular, performs pattern defect correction of an exposure mask such as a photomask or an X-ray mask, and correction of LSI wiring. And a control method therefor.

[Conventional technology]

2. Description of the Related Art Conventionally, as a method for correcting a defect of a photomask or an X-ray mask, a method of focusing an ion beam on a fine spot, irradiating a defect on a sample, and removing the defect by sputtering is performed.

In this case, it is necessary to set the processing depth with high accuracy in order to remove only the defective portion and not to damage a normal portion.

Conventionally, as described in, for example, Japanese Patent Application No.
The beam current is measured at predetermined time intervals, and the product is multiplied by the product of the processing speed coefficient (the processing volume of the workpiece per unit time by the unit current) determined in advance to obtain the processing volume, and this is used for beam scanning. A method of obtaining a processing depth by dividing by a region area has been proposed.

[Problems to be solved by the invention]

In the above conventional example, the ion beam current drifts during processing, and an error occurs when the processing depth is controlled by the processing time based on the beam current value at the start of processing, so that an attempt is made to measure the beam current during processing. Is what you do. As shown in FIG. 9, the method uses an ion beam extracted from an ion source 21 for first, second, and third lens electrodes (22, 23, 2 in the figure).
4), the beam is focused on the sample 28, and the beam is scanned in the beam processing area by the deflection voltage of the deflector electrode 27. The beam current is measured using any one of ammeter A ₁ or ammeter A ₂ or ammeter A _3. Ammeter A ₁ is intended for measuring the source current i _s entering the first lens electrode 22, the source current i _s is the beam current i _b, is represented by a function _{i b = f (i s)} , the The function is approximated by a linear function, and the coefficient of the linear function is obtained in advance by actual measurement.
From the obtained source current i _s value, the beam current i _b
Is what you want. A product of the obtained ion beam current and a previously obtained processing speed coefficient is integrated over time to obtain a processing volume, and the obtained processing volume is divided by a processing area to obtain a processing depth.

By the way, at the electrode 22, secondary electrons 35 are generated by the irradiation of the ion beam. At this time, if the electrode 22 is a flat plate electrode, out secondary electrons electrode external flows to the ground from the barrel, the value of the ammeter A ₁ represents a value greater than the ion current having flowed. In the prior art as a countermeasure, and by using the current value by the ammeter A _2. However, the aperture current i _A flowing into the third electrode (beam limiting aperture) 24 is determined by the ammeter A ₃ , and the beam current is determined from this. Therefore, there is a problem that the influence of the secondary electrons 36 generated from the electrode 24 cannot be avoided. However,
If only the beam current is determined, the current due to the secondary electrons is
Since it is proportional to the aperture current i _a flowing into the electrode,
It is possible to obtain the correct current value from the value of A _3.

Further, the prior art does not describe the blanking aperture 26 and the sample stage 29 that can directly measure the beam current without calculating the beam current as the current measurement points.
Therefore, the beam current measures the current flowing into the electrode,
It is obtained from a function of the beam current and the measured current that have been obtained in advance. However, there is a problem that an error is unavoidable, for example, this function is an approximate expression, and conditions change before and during processing. However, with respect to the sample stage 29, as shown in FIG. 10, the sample stage 27 is moved at predetermined time intervals during processing so that the ion beam 37 enters the Faraday cup 38 of the sample stage 27, It can be measured by a _4. However, in this method, since the sample stage 29 is moved every time the current is measured, there is a problem that the processing time is wasted or the processing position is shifted unless the positioning accuracy of the sample stage is improved.

The object of the present invention is to measure the beam current during processing,
An ion beam apparatus capable of performing high-accuracy, high-speed measurement and performing stable ion beam processing without eliminating the effects of errors in calculating the current and beam current due to secondary electrons and waste of processing time, and its control. It is to provide a method.

[Means for solving the problem]

The object is an ion source, an extraction optical system for extracting an ion beam generated by the ion source, a focusing optical system for converging the extracted ion beam and scanning and irradiating the sample on a sample. A mounting table on which a sample is mounted, a beam current measuring unit for measuring a current value of the ion beam as a state where an incident portion of the ion beam is maintained at a positive potential, and the beam current measured by the beam current measuring unit. This is achieved by providing a control unit that controls the processing depth of the sample by converging the ion beam based on the current value of the ion beam and scanning and irradiating the ion beam on the sample.

Further, as a control method, in an ion beam apparatus that focuses an ion beam extracted from an ion source by an extraction optical system, scans the sample on a sample, and irradiates the sample with the ion beam, By measuring the current of the ion beam by making a part or all of the light incident on an electrode maintained at a positive potential,
It is achieved by controlling the extraction voltage for extracting the ions of the extraction optical system based on the measurement result.

[Action]

When either all or part of the ion beam is incident on either the electrode or the sample on the sample stage, secondary electrons are generated from either the electrode or the sample.

Therefore, when an ammeter is connected to either the electrode or the sample stage and the ion beam current value is measured, the current value is calculated by dividing the current value of the ion beam incident on either the electrode or the sample by the secondary electron. Only increase.

At that time, a number is assigned to either the electrode or the sample stage.
When a DC voltage of 10 V is applied, the secondary electrons generated from either the electrode or the sample return to either the electrode or the sample again, and the ammeter indicates that the entire or part of the ion beam is either the electrode or the sample. The true current value incident on is measured.

During the blanking period, the entire ion beam to be measured is incident on the sample on the sample stage during the blanking period, unlike other electrodes during ion beam scanning.

Therefore, when a DC voltage of several tens of volts is applied to one of the blanking aperture and the sample stage to measure the current, the ion beam current value can be directly measured without conversion.

At this time, the measurement time is a horizontal and vertical blanking period during ion beam scanning in the blanking aperture, and a beam irradiation period during ion beam scanning in the sample stage. Since the measurement can be performed by using the processing time, it is possible to save the processing time.

Furthermore, since the ion beam current is detected and used for controlling the processing depth and the ion beam current is stabilized, the processing accuracy can be improved.

〔Example〕

Hereinafter, FIGS. 1 to 4 showing an ion beam processing apparatus according to a first embodiment of the present invention will be described.

As shown in FIG. 1, the ion beam processing apparatus according to the present embodiment includes a high-intensity liquid metal ion source 1 at a position above a sample 8 which is positioned in both the X and Y directions by a sample stage 9. 1, an extraction electrode 2 for extracting an ion beam, a lens electrode 3 including one or more electrodes for focusing the extracted ion beam 10, and an ion beam 10.
A beam limiting aperture 4 for narrowing the beam, a blanking electrode 5 for turning on / off the ion beam 10, and a plurality of electrodes for scanning the processing area of the sample 8 with the blanking aperture 6 and the focused ion beam 10. And a deflection electrode 7. The liquid metal ion source 1 is connected to an acceleration power source 12 for accelerating the ion beam 10 and is connected to an extraction power source.
11 is connected to the electrode 2. The lens electrode 3 is connected to a lens power supply 13. The beam limiting aperture 4 includes a DC power supply 14 for suppressing secondary electrons generated from the beam limiting aperture 4, an ammeter 15 for measuring an ion beam current, and an A / D converter for converting the measured current value. A / D converter 16 and a microcomputer 17 for inputting the converted current value.

 Next, the operation will be described.

When a high voltage of several kV is applied to the extraction electrode 2 by the extraction power source 11 and the ion beam 10 is extracted from the liquid metal ion source 1, the extracted ion beam 10 It is focused by the electrode 3.

The focused ion beam 10 is narrowed down by the beam limiting aperture 4 so as to obtain a desired beam diameter. At this time, as shown in FIG. 2A, the ion beam 10 blocked by the beam limiting aperture 4 is
Secondary electrons 40 are generated by the incident ion beam 10 at the beam limiting aperture 4 while flowing into the beam limiting aperture 4.

The secondary electrons 40 flow from the lens barrel to ground, and do not return to the beam limiting aperture 4.

Therefore, if the current of the ion beam 10 flowing into the beam limiting aperture 4 is i _a , and the current i _e due to the generation of the secondary electrons 40 is i _e , the current value by the ammeter 15 is i _a + i _e , and the beam limiting aperture Current flowing into 4
The value is larger than i _a by i _e .

Therefore, in the present embodiment, as shown in FIG. 2B, a DC voltage is applied from the DC power supply 14 having a value of several tens of volts so that the beam limiting aperture 4 side becomes an anode. Then, the secondary electrons 40 generated from the beam limiting aperture 4 are returned to the beam limiting aperture 4 again, thereby suppressing the generation of the secondary electrons 40.

In this case, the amount of the secondary electrons 40 drawn back to the beam limiting Aperture 4, the voltage value V _B to be applied is gradually increased according to increase, the 0 current i _e due to occurrence of secondary electrons 40 Approaching.

On the other hand, the current flowing into the beam limiting aperture 4
i _a is independent of the increase in the applied voltage value V _B.

Thus, as shown in FIG. 3, the current value I _m is measured by the ammeter 15, continue to decrease with increasing voltage value V _B,
A constant value upon reaching V ₀ to a certain value.

This reduced amount is a current value i _e due to occurrence of secondary electrons 40, minutes became constant is flowing current i _b of the true beam limiting Aperture 40.

Further, the voltage value V ₀ when the voltage becomes constant is set as the set value of the DC power supply 14 at the time of measuring the ion beam current.

Next, the current value measured by the ammeter 15 is read by the A / D converter 16
, And input to the microcomputer 17.

Thus the current value obtained is a current value flowing into the beam limiting Aperture 4, to obtain the ion beam current value flowing into the sample 8, before processing, pre-aperture inflow current i _a and the ion beam it is necessary to determine the relationship between the current i _b.

Therefore, as shown in FIG. 4 when determining the relationship between aperture inflow current i _a and the beam current i _b, since it is possible to a linear function approximation and store its parameters in advance in the microcomputer 17.

Then the ion beam current i _b is calculated by using the microcomputer 17 from the current i _a flowing into the beam limiting Aperture 4 obtained using this function.

However, when the ion beam current i _b is obtained by such a calculation method, the current i _e due to the secondary electrons 40 is proportional to the current i _a flowing into the beam limiting aperture 4. even if there is influence of _e, it is possible to determine the current i _a flowing into the beam limiting Aperture 4.

When determining the working depth, by the value of the resulting ion beam current i _b in the manner described above was measured at predetermined time intervals, you add the measured values by the microcomputer 17 obtains the integration with respect to time, The processing volume is obtained by multiplying the processing speed coefficient, and the processing depth is obtained by dividing the processing volume by the processing scan area.

By doing so, together with the current i _a flowing into the beam limiting Aperture 4 can be measured without being affected by secondary electrons 40, it is possible to calculate the ion beam current i _a, the it can be calculated even when the ion beam current i _b is gradually varied with time, thereby it is possible to control the machining depth with high accuracy from the ion beam current i _b.

Next, FIGS. 5 and 6 showing an ion beam processing apparatus according to a second embodiment of the present invention will be described.

Ion beam processing apparatus of the present embodiment shown in Fig. 5, as compared to the embodiment shown in the first figure, the ammeter 15 for measuring the ion beam current i _b is connected to the flop Index Aperture 6 Only the points are different, and the other points are the same. Therefore, they are denoted by the same reference numerals and the different points will be described.

In the present embodiment, determined directly unlike the method of calculating by using an approximate expression from a current i _a flowing an ion beam current i _b as in the first embodiment shown in FIG. 1 to the beam limiting Aperture 4 Things.

 Next, the operation will be described.

The ion beam 10 extracted by the extraction electrode 2 is focused on the sample 8 by the lens electrode 3. At this time, when the voltage of the blanking electrode 5 is applied, the ion beam 10
Is bent and blocked by the blanking aperture 6, so that the ion beam 10 does not reach the sample 10.

Since the ion beam 10 cut off by the blanking aperture 6 has the same current value as the ion beam incident on the sample 8, the voltage is applied to the blanking aperture 6 and the measured value is obtained by the ammeter 15. The beam current value can be obtained directly. When the ion beam 10 is incident on blanking Aperture 6, since the secondary electrons are emitted from the blanking Aperture 6, it correspondingly, the current value I _m is measured by the ammeter 15 increases However, when a DC voltage is applied from the DC power supply 14 to the blanking aperture 6 as in the first embodiment, the emission of secondary electrons from the blanking aperture 6 is suppressed. is there. At that time, the setting method of the bias voltage V ₀ which the DC power source 14 is performed by the same method as the embodiment shown in Figure 1.

By the way, regarding the measurement time point of the ion beam current, it is possible to apply a blanking at regular time intervals during processing and measure the current value of the ion beam 10 at the time point when the ion beam 10 is cut off. .

However, when processing a rectangle as shown in FIG. 6A, the ion beam 10 is scanned in a rectangular shape, so that the deflection electrode 7 shown in FIG. 5 has a saw-toothed shape as shown in FIG. Apply a wave. At this time, in the-and-flyback portions, a voltage is applied to the blanking electrode 5 as shown in FIG. 6 (c). Accordingly, as shown in FIG. 6 (d), by inputting a current measurement trigger to the microcomputer 17 corresponding to the blanking period, the measurement can be performed during the blanking period.

Also, by measuring the current value in this way,
Ion beam 10 without being affected by secondary electrons
Can be measured directly, and there is no approximation error due to calculation or errors due to changes in conditions before and during machining, and measurement can be performed without stopping machining during machining. it can.

Further, the fact that the processing depth can be controlled using the ion beam current value is the same as in the first embodiment shown in FIG.

Next, an ion beam apparatus according to a third embodiment of the present invention will be described with reference to FIG.

The third embodiment shown in FIG. 7 is different from the first and second embodiments in that an ammeter 15 for measuring the ion beam current is connected to the sample stage 9. Otherwise, they are the same.

In this embodiment, as in the second embodiment, it is to directly measure the current i _b of the ion beam 10.

As in the first and second embodiments, the ion beam 10 focused by the lens electrode 3 is applied to the sample 8 by the deflection electrode 7.
Scan above.

At this time, secondary electrons are generated from the surface of the sample 8. Therefore, the current flowing through the ammeter 15 is the current of the ion beam 10.
It is larger than i _{b by the} current i _e due to the generation of secondary electrons.

Therefore, by applying a DC voltage from the DC power source 14 to the sample stage 9 to make the sample stage 9 an anode, the generation of secondary electrons from the sample 8 can be suppressed. it can be measured 10 current i _a direct.

Measurement time point in this case the ion beam current i _a is not performed during the blanking period unlike the case of the second embodiment, the scanning period of the ion beam 10 in FIG. 6 (b) -, -
Do with.

Also in the sample stage 9 by doing so, it is possible to measure the ion beam current i _b without moving the sample stage 9, to prevent waste and positioning error of processing time with the movement of the sample stage 9 Can be.

In addition, the fact that the processing depth can be controlled using the ion beam current value measured as described above is the same as in the above embodiment.

Next, an ion beam apparatus according to a fourth embodiment of the present invention will be described with reference to FIG.

The fourth embodiment shown in FIG. 8 is compared with the first embodiment,
The difference is that a feedback circuit 17 'from the microcomputer 17 to the extraction power supply 11 is provided, and the other points are the same. Therefore, the differences will be described.

In the fourth embodiment, the ion beam current value obtained in the first embodiment is fed back to the extraction power source 11, thereby varying the voltage of the extraction power source 11 to try to constant ion beam current i _a Things.

In this case, the ion beam current i _a resulting will vary depending on the state change, such as a liquid metal ion source 1, to a constant ion beam current value by changing the extraction voltage in response to a change in current value Can be.

This method is also possible in the second and third embodiments.

This method can also be used when the current value of the ion beam 10 is simply monitored at the electrode into which part or all of the ion beam 10 flows.

Therefore, in each of the above embodiments, when correcting a pattern defect of an exposure mask such as a photomask or an X-ray mask and correcting an LSI wiring by using a focused ion beam, the secondary electron beam is not moved without moving the sample stage. Since it is possible to directly measure only the current of the ion beam corresponding to the processing depth while suppressing the occurrence, it is possible to eliminate errors due to secondary electron current, ion beam current calculation errors, and waste of processing time, and to eliminate ion beam defects. This can be removed by applying only to the portion, and ion beam processing can be performed with high accuracy without damaging a normal portion.

In addition, since the extraction voltage can be changed based on the measured current value of the ion beam to keep the ion beam current constant, highly accurate and stable ion beam processing can be performed.

〔The invention's effect〕

As described above, in the ion machining method according to the present invention, the current due to the secondary electrons, the calculation error of the current of the ion beam, and the waste of machining time are eliminated, and only the defect portion of the ion beam is removed. It is possible to perform highly accurate and stable ion beam processing without damaging a portion.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a main part of an ion beam apparatus according to a first embodiment of the present invention. FIGS. 2 (a) and 2 (b) are ion beam current measurement explanatory views in the first embodiment, and FIG. Figure 1
FIG. 4 is an explanatory diagram showing the relationship between the bias voltage and the ion beam measurement current in the embodiment of FIG. 4, FIG. 4 is an explanatory diagram showing the relationship between the aperture current and the ion beam current in the first embodiment, and FIG. FIG. 6 is an explanatory view showing a main part of an ion beam apparatus according to a second embodiment, FIG. 6 is a timing chart of an ion beam measurement time in the second embodiment, and FIG.
FIG. 9 is an explanatory view showing a main part of an ion beam apparatus according to a third embodiment of the present invention. FIG. 8 is an explanatory view showing a main part of the ion beam apparatus according to a fourth embodiment of the present invention. Is an explanatory view of a main part showing a conventional ion beam processing apparatus, and FIG. 10 is an explanatory view of ion beam current measurement in the conventional ion beam processing apparatus. 1 ... liquid metal ion source, 2 ... extraction electrode, 3 ... lens electrode, 4 ... beam limiting aperture, 5 ...
... blanking electrode, 6 ... blanking aperture, 7
…… Deflecting electrode, 8 …… Sample, 9 …… Sample stage, 10…
... Ion beam, 11 ... Extraction electrode, 1 ... Acceleration power supply,
13: Lens power supply, 14: DC power supply, 15: Ammeter, 16
…… A / D converter, 17 …… Microcomputer, 19 ……
Secondary electron detector.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01J 37/30-37/305

Claims (8)

(57) [Claims] An ion source, an extraction optical system for extracting an ion beam generated by the ion source, a focusing optical system for converging the extracted ion beam and scanning and irradiating the sample on a sample, A mounting table for mounting the sample, a beam current measuring unit for measuring the current value of the ion beam as a state where the incident portion of the ion beam is maintained at a positive potential, and a beam current measuring unit An ion beam apparatus comprising: a control unit that controls a processing depth of the sample by focusing the ion beam based on a current value of the ion beam, and scanning and irradiating the ion beam on a sample. 2. An ion beam apparatus according to claim 1, wherein said beam current measuring section is a beam limiting aperture provided in said focusing optical system section. 3. The ion beam apparatus according to claim 1, wherein said beam current measuring section is a blanking electrode provided in said focusing optical system section. 4. An ion beam apparatus according to claim 1, wherein said beam current measuring section is provided on said mounting table. 5. An ion beam apparatus which focuses an ion beam extracted from an ion source by an optical system and scans and irradiates a sample onto a sample, and a part of the ion beam is irradiated during the irradiation. Alternatively, the current of the ion beam is measured by irradiating the ions to an electrode maintained at a positive potential, and the extraction voltage for extracting the ions of the extraction optical system is controlled based on the measurement result. Control device for an ion beam device. 6. The method according to claim 5, wherein the measurement of the ion beam current is performed by measuring the ion beam incident on the electrode provided in the focusing optical system. . 7. The method according to claim 1, wherein the measurement of the ion beam current is performed by causing the ion beam to be incident on the electrode at a retrace portion of scanning when the ion beam is scanned and irradiated on a sample. The method for controlling an ion beam apparatus according to claim 5, wherein 8. The method according to claim 1, wherein the measurement of the ion beam current is performed by detecting a current flowing from the sample to the sample stage when the ion beam is scanned and irradiated on the sample. Item 6. A method for controlling an ion beam device according to Item 5.