JPH0246642A - Focused charged particle beam device - Google Patents

Abstract

PURPOSE:To make it possible to radiate a focused charge particle beam on a sample accurately without deviation of position and with no need for processing of the sample even when the sample is an insulator by detecting the amount of secondary electrons relating to the charged potential of the sample and supplying electrons corresponding to the detected result to the sample. CONSTITUTION:The amount of secondary electrons 3 when an insulator sample 1 is uncharged is measured previously, and the measured value is used as the reference value of a feedback circuit 7. During the actual operation, the detected result by a secondary electron detector 6 is always compared with the reference value, and the compared result is outputted to an electron supplier 5. The amount of electrons to be supplied from the electron supplier 5 is determined basing on the compared result. Therefore an amount of electrons 4 corresponding to the charged state of an irradiation area 1a of an insulator sample 1 is supplied to the said irradiation area 1a, and the electrical neutralization of the said area 1a can be carried out speedy and reliably. Thereby a focused charged particle beam can be irradiated on the sample accurately without deviation of position and with no need to process the insulator sample.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention uses a focused charged beam to scan in two dimensions.
This invention relates to a focused charged beam device that performs image observation, pattern inspection, etc.

[Conventional technology]

A technique using a focused charged beam is a scanning electron microscope (S
EM), electron beam exposure equipment, X-ray microanalyzer (XMA), analysis equipment such as Auger electron spectroscopy, photomask repair equipment using focused ion beam (FIB), etc.
It is applied in various fields. The focused charged beam is: ■Can be focused to micrometer order or less using a lens.■Can be deflected at high speed by electric and magnetic fields.■Additional 3! It has the advantage that the beam energy can be easily changed by changing the voltage, but on the other hand, it requires a high vacuum atmosphere when using the charged beam.It is difficult to use the charged beam for insulating samples. There are also drawbacks. Defect (2) will be explained below.

When a sample of an insulator (including materials with very high resistance) is irradiated with a focused charged beam, the amount of electrons supplied to the irradiated area of the sample and the amount of irradiation! ) Since the amount of secondary electrons emitted from the l region is different, positive or negative charges accumulate in the irradiated region (charging phenomenon).

When charged, the potential of the irradiated area changes and the electric field distribution around the sample changes. As a result, the focused charged beam is affected by changes in the electric field distribution around the sample and is deflected, causing a positional shift in the irradiation position of the focused charged beam on the sample.

When the amount of charge accumulated in the above-mentioned irradiated region increases and the resulting potential increases to a certain extent, a discharge phenomenon occurs, and the charge escapes to the ground through an easy-to-pass path in the sample. In this way, the irradiated area is repeatedly charged and discharged, and the electric field distribution around the sample is constantly changing.

For this reason, it is extremely difficult to accurately irradiate a focused charged beam to a predetermined position on an insulator sample, and it is extremely difficult to apply a focused charged beam to an insulator sample.

[Problem to be solved by the invention]

The following methods can be used to prevent the above-mentioned charging and discharging phenomena.

The first method is to coat an insulator sample with a metal such as gold or platinum, and is often used when observing an insulator sample with an SEM. However, this method has the problem that the sample is coated with metal and cannot be reused.

The second method is to reduce the amount of secondary electrons emitted from the beam irradiated area by lowering the accelerating voltage of the focused charged beam to a few kilovolts or less, and to reduce the amount of secondary electrons emitted from the beam irradiated area, and to This method maintains a balance between the two and makes it difficult for charging phenomena to occur. This method is used in SEM. However, this method has the problem of being restricted to fixing the accelerating voltage to several kilovolts or less.

The third method is to install a simple electron gun called a charge neutralizer, that is, an electron supply device, near the sample.
This is a method in which a sample is irradiated with a low energy (about 7500 eV) electron beam during or within a short time after irradiation with a focused charged beam.

In this method, by increasing the amount of electrons supplied to the irradiated area of the sample, the amount of secondary electrons emitted from the irradiated area is balanced with the amount of secondary electrons, so that charging does not occur. This method is used in FIB, photomask repair equipment, etc.

FIG. 3 is a block diagram showing an example of irradiation of an insulator sample by a focused charged beam device in the third method described above. As shown in the figure, when an insulator sample 1 is irradiated with a focused charged beam 2, secondary electrons 3 are emitted from an irradiated area tiff11a of the insulator sample 1. At this time, when the focused charged beam 2 is a positive ion, it is of course positively charged, but even in the case of electrons, the amount of charge of the emitted secondary electrons usually exceeds the amount of charge of the incident focused charged beam 1, so The irradiated area 1a is positively charged. Therefore, by supplying electrons 4 having almost no acceleration energy to the irradiated region 1a from the electron supply device 5, the irradiated region 1a is electrically neutralized and charging is prevented.

By the way, a focused charged beam device is often used for fIi observation. The signal source used for this image observation is often secondary electrons 3, and in order to clearly distinguish between the electrons 4 supplied from the electron supplier 5 and the secondary electrons 3, as shown in FIG. The focused charged beam irradiation time T1 and the electron supply time T2 by the electron supplier 5 are often time-divided.

By the way, the focused charged beam device equipped with the electron supply device 5 described above does not detect a change in the degree of charging in the irradiated tJJ region 1a of the insulator sample 1.

Therefore, the amount of electrons supplied from the electron supply device 5 must be adjusted by trial and error. Furthermore, even if the -degree adjustment is possible, if the physical properties of the insulating material 1 change due to irradiation of the focused charged beam 2 to the irradiated region 1a, etc., the amount of electrons supplied from the electron supply device 5 must be readjusted, and if this change is too fast, adjustment is not possible.

For the reasons described in , F, the trial-and-error method of supplying electrons using the electron supply device 5 had the problem that it was not possible to sufficiently prevent the irradiated area 1a of the insulator sample 1 from being charged, and accurate beam irradiation could not be performed. .

This invention was made to solve the above-mentioned problems, and when irradiating a focused charged beam, even if the sample is an insulator, it is possible to irradiate the focused charged beam without processing the insulating sample. It is an object of the present invention to provide a focused charged beam device that can accurately irradiate a focused charged beam without positional deviation without imposing any restrictions on accelerating voltage.

[Means to solve the problem]

A focused charged beam device according to the present invention includes a beam irradiation unit that irradiates a sample with a focused charged beam, and a secondary electron beam that detects the suspension of secondary electrons emitted from the sample when the beam irradiation unit irradiates the focused charged beam. electronic detection means;
and electron supply means for supplying an amount of electrons to the sample according to the detection result of the secondary electron detection means.

[Effect]

The secondary electron detection means in this invention detects the ω of secondary electrons which has a correlation with the charged potential of the sample, and the electron supply means supplies electrons to the sample at a time corresponding to the detection result of the secondary electron detection means. supply to.

〔Example〕

FIG. 1 is a block diagram showing a focused charged beam device which is an embodiment of the present invention. As shown in the figure, a secondary electron detector 6 is newly provided, the detection result of this secondary electron detector 6 is inputted to a feedback circuit 7, and based on the output of this feedback circuit 7, an electron supplier 5 M of the electrons 4 supplied to the insulator sample 1 is changed accordingly. The other configurations are the same as the conventional one, so explanations will be omitted.

FIG. 2 is a graph showing the energy distribution of the secondary electrons 3. When the insulator sample 1 is not charged, secondary electrons 3 with full energy are emitted from the irradiated region 1a and detected by the secondary electron detector 6.

However, the irradiated area 1a of the insulator sample 1 is
O) When charged to V, the secondary electrons 3 having an energy of less than X1ev, shown by diagonal lines in FIG. 2, cannot reach the secondary electron detector 6 at the ground level and are not detected. Therefore, the amount of electrons detected by the secondary electron detector 6 is reduced compared to when the irradiated area 1a is not charged. Therefore, the charged state of the irradiated area 1a can be determined from this decreased amount of electrons.

The focused charged beam device shown in FIG. 1 is constructed using the above points. That is, the suspension of the secondary electrons 3 when the insulator sample 1 is not charged is measured in advance, and the reference value of the feedback circuit 7 is set to that value. During actual operation, the detection result by the secondary electron detector 6 is constantly compared with a reference value, and the comparison result is output to the electron supply device 5.

Based on this comparison result, by determining the amount of electrons to be supplied from the electron supply device 5, the irradiated area of the insulator sample 1 is
The skewer electrons 4 corresponding to the charging state of a are supplied to the irradiated area 1a, and the irradiated area 1a of the insulator sample 1 is quickly and accurately
Electrical neutralization can be achieved.

Therefore, the insulator sample 1 can be accurately irradiated with the focused charged beam 1, and highly accurate image observation, pattern inspection, pattern correction, pattern drawing, and microfabrication can be performed.

Furthermore, since the insulator sample 1 is not processed, it is possible to reuse the insulator sample 1, and the acceleration voltage of the focused charged beam is not limited.

〔Effect of the invention〕

As explained above, according to the present invention, the secondary electron detection means detects ω of the secondary electrons which has a correlation with the charged potential of the sample, and the electron supply means responds to the detection result of the secondary electron detection means. Since the mother electrons are supplied to the sample, even if the sample is an insulator, the electron supply means can always supply electrons so as to maintain electrical neutralization of the irradiated region.

As a result, it is possible to accurately irradiate a sample with a focused charged beam without positional deviation, without processing the insulator sample or limiting the accelerating voltage of the focused charged beam.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing a focused charged beam device which is an embodiment of the present invention, and FIG. 2 is a graph showing the energy distribution of secondary electrons emitted from a sample during focused charged beam irradiation.
Figure 3 is a configuration diagram showing a conventional focused charged beam device;
The figure is a timing chart showing the control timing of the focused charged beam device shown in FIG. 3. In the figure, 1 is an insulator sample, 2 is a focused charged beam, and 3 is a
4 is a secondary electron, 4 is an electron, 5 is an electron supplier, 6 is a secondary electron detector, and 7 is a feedback circuit. Note that the same symbols in each figure indicate the same or equivalent parts. Diagram

Claims (1)

[Claims] (1) beam irradiation means for irradiating a sample with a focused charged electric beam; secondary electron detection means for detecting the amount of secondary electrons emitted from the sample when the beam irradiation means irradiates the focused charged electric beam; and electron supply means for supplying an amount of electrons to the sample according to the detection result of the secondary electron detection means.