JPH063725B2 - Electronic beam positioning method in stroboscopic electronic beam device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a stroboscopic electron beam device for measuring a potential distribution image or the like on the surface of an IC at a specific phase when a periodic signal is supplied to the IC, and more particularly to the above. It is intended to realize a method for accurately determining the irradiation position of a strobe electron beam.

"Background of the Invention" FIG. 2 shows a schematic view of the strobe electron beam apparatus.
This supplies a signal synchronized with the periodic signal supplied from the terminal 20 to the IC 16 from the terminal 18 to the blanking deflector 12. Then, the electron beam generated from the electron gun 11 is deflected to scan the diaphragm 13. At this time, the electron beam passes through the opening 23 of the diaphragm 13 at regular time intervals. The electron beam that has passed through the opening 23 of the diaphragm 13 is
Deflection is performed by the signal supplied to the beam scanning coil 14 from the terminal 19 and the predetermined position of the IC 16 is irradiated. At this time, the intensity of secondary electrons reflected from the IC 16 is detected by the secondary electron detector 15 and output from the terminal 21. By measuring this output voltage, the potential at the position irradiated with the electron beam can be obtained.

For example, the signal shown in FIG. 3A is supplied from the terminal 20 to the IC 16, and the signal shown in FIGS. 3B and 3C is supplied from the terminal 18. The signals in FIGS. 3B and 3C are synchronized with the signal in FIG. 3A. The voltages shown in FIG. 3B are -V _X and V _X.
The trapezoidal wave signal that changes between the
2 X-axis deflection plates. A rectangular wave signal whose voltage changes between 0 (V) and V _Y shown in FIG. 3C is supplied to the Y-axis deflection plate of the blanking deflector 12. Therefore, as shown in FIG. 4, the irradiation position of the electron beam on the diaphragm 13 changes in the direction of the arrow. When the signal supplied to the Y-axis deflection plate is 0 (V) and the signal supplied to the X-axis deflection plate changes from -V _X to V _X , the signal supplied to the X-axis deflection plate is 0 (V). V) near the aperture 2 of the aperture 13 of the electron beam
Pass 3. FIG. 3D shows the electron beam passing through the opening 23. This electron beam is synchronized with the signal shown in FIG.
The surface of the IC 16 is scanned by being deflected by 4. Therefore, the potential distribution image on the surface of the IC 16 at a specific phase of the periodic signal from the terminal 20 can be measured.

In addition, the scanning coil 14 transmits the stroboscopic electron beam to the IC1.
Deflection to a predetermined position on the surface of 6. Then, the opening 23 of the electron beam with respect to the phase of the signal supplied to the IC 16
By sequentially shifting the time passing through IC1, IC1
It is possible to measure the potential waveform at the above positions of 6.

However, in the apparatus shown in FIG. 2, when the electron beam passes through the opening 23 of the diaphragm 13, the blanking deflector 1
Voltage supplied to the second X-axis deflector changes from -V _X to V _X. The time that the electron beam passes through the blanking deflector 12 cannot be ignored, and the trajectory of the electron beam is bent during that time. That is, the electron beam that has passed through the opening 23 of the diaphragm 13 is not emitted from the electron gun 11 perpendicularly to the diaphragm 13, but its orbit is bent by the blanking deflector 12 and passes through the opening 23. It is a thing. Therefore, when the electron beam is deflected by the beam scanning coil 14 and irradiated on the IC 16, there is a problem that the electron beam deviates from the actually designated position. This problem becomes particularly fatal when the potential waveform is measured by irradiating a predetermined position on the surface of the IC 16 with an electron beam. In addition, the above deviation is caused by the electron gun 1
The lower the beam accelerating voltage at 1 is, the larger it is.

"Means for Solving Problems" In the electron beam positioning method according to the present invention, a calibration mark is added, for example, on a stage. Then, the electron beam is irradiated perpendicularly to the diaphragm to pass through the opening, and the electron beam is continuously scanned to detect the accurate mark position.
Next, a predetermined signal is supplied to the blanking controller to obtain a strobe electron beam, and the strobe electron beam is scanned to detect the mark position. The correction amount is obtained from these two mark positions. When measuring a potential waveform or the like at a predetermined position of the IC, the irradiation position of the electron beam is accurately determined by using the correction amount.

[Embodiment] FIG. 1 shows a flowchart of a method of calculating a correction amount used when a stroboscopic electron beam is applied to a predetermined position of an IC. At this time, for example, the calibration mark 22 provided on the stage 17 moves under the electron gun 11 by moving the stage 17. The calibration mark 22 may have any shape as long as its center position can be obtained by beam scanning.

First, in step 1, the electron beam is continuously scanned to obtain an accurate mark position. At this time, the blanking deflector 12
Since no signal is supplied to the aperture, the electron beam from the electron gun 11 irradiates the diaphragm 13 vertically, and passes through the opening 23 as it is. The electron beam that has passed through the opening 23 of the diaphragm 13 is deflected by the beam scanning coil 14 to scan the calibration mark 22 a plurality of times. For example, when the edge of the calibration mark 22 is stepped, the intensity of the secondary electrons detected by the secondary electron detector 15 when the electron beam passes through this edge changes abruptly. Therefore, a threshold voltage is set, and when the output voltage from the secondary electron detector 15 crosses this threshold voltage, the irradiation position of the electron beam is obtained from the voltage supplied to the beam scanning coil 14 and stored in the storage means. Remember. When a plurality of beam scans are completed, the irradiation positions of the plurality of electron beams stored in the storage means are averaged to obtain an accurate mark position (X ₁ ,
Y ₁ ) is required.

Next, in step 2, the blanking deflector 12 is supplied with the signals shown in FIGS. 3B and 3C through the terminal 18, for example. At this time, when the signal supplied to the X-axis deflection plate of the blanking deflector 12 changes from the negative voltage −V _X to the positive voltage V _X , the electron beam passing through the opening 23 of the diaphragm 13 is changed to the beam scanning coil 14. The calibration mark 22 is deflected by scanning with a plurality of times. Then, the mark position (X ₂ , Y ₂ ) is obtained by the same method as in step 1.

Finally, in step 3, the mark position (X ₁ , Y ₁ ) obtained by continuous scanning of the beam and a predetermined signal are supplied to the blanking deflector 12 to generate a strobe electron beam, and the strobe electron beam is scanned. The mark position (X ₂ ,
Correction amount by calculating the difference between Y ₂₎ obtaining the (ΔX, ΔY).

When a signal is supplied to the IC 16 and the surface of the IC 16 is irradiated with a strobe electron beam to measure a potential waveform or the like, a correction amount (ΔX, ΔY) is added to the irradiation position (X, Y) of the beam, and this addition is performed. By supplying the signal corresponding to the value to the beam scanning coil 14 from the terminal 19, the electron beam can be accurately applied to the designated position.

The pulse width of the strobe electron beam used may be changed according to the density of the pattern on the surface of the IC 16. For example, when a desired position is irradiated with an electron beam in a region having a high pattern density to measure a potential waveform or the like, it is better to use an electron beam having a smaller pulse width. This is changing the pulse width of the electron beam, for example, a voltage of a trapezoidal wave shown in Figure 3 B may be changed the slope of the portion changes from -V _X to V _X. If the pulse widths of a plurality of strobe electron beams to be used are known in advance, in step 2, blanking the signals as shown in FIGS. 3B and 3C corresponding to the strobe electron beams having respective pulse widths. It is supplied to the deflector 12. The mark position (X ₂ ,
In step 3, the correction amount (ΔX, ΔY) is calculated from Y ₂ ) and stored in the storage means. Then, when the measurement is performed using the stroboscopic electron beam, a correction amount corresponding to the pulse width of the stroboscopic electron beam used at the irradiation position of the beam is added, and a signal corresponding to this added value is supplied to the beam scanning coil 14. You may do it.

[Advantages of the Invention] As described above, the electron beam positioning method in the stroboscopic electron beam apparatus according to the present invention has the mark position (X ₁ , which is obtained by continuously scanning the electron beam without supplying a signal to the blanking controller). Y ₁ ) and a signal to the blanking controller to generate a stroboscopic electron beam,
A correction amount (ΔX, ΔY) is calculated from the mark position (X ₂ , Y ₂ ) obtained while scanning the stroboscopic electron beam. Then, when various measurements are performed using the strobe electron beam, the correction position is used to correct the irradiation position of the electron beam, so that the electron beam can be accurately irradiated to the specified position, and the accuracy can be improved. It can be measured well.

[Brief description of drawings]

FIG. 1 is a flow chart showing a method of calculating a correction amount used when irradiating a predetermined position with a strobe electron beam used in the present invention, FIG. 2 is a schematic diagram of a strobe electron beam apparatus, and FIG. 3 is shown in FIG. FIG. 4 is a plan view for explaining the operation of the electron beam on the diaphragm 13 of the device shown in FIG. 2, and a timing chart for explaining the operation of the device.

Claims (1)

[Claims] 1. A strobe electron beam apparatus, wherein a calibration mark is added at a predetermined position where an electron beam can be irradiated, and the calibration mark is obtained by scanning the calibration mark with a continuous electron beam without supplying a signal to a blanking deflector. Mark position,
A strobe electron beam is obtained by supplying a predetermined signal to a blanking deflector, and a correction amount is calculated from the difference between the strobe electron beam and the mark position obtained by scanning the calibration mark with the strobe electron beam. When the measurement is performed, the signal corresponding to the electron beam irradiation position is added to the signal corresponding to the correction amount, and the added signal is supplied to the beam scanning coil to deflect the strobe electron beam. An electron beam positioning method characterized by the above.