JP2006339051A - Electrically charged particle application apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent physical damage to a vacuum chamber by preventing build up of charge and electrifying on a surface of an object regardless of an irradiated portion or non-irradiated portion, in an electrically charged particle application apparatus carrying out analysis of the object or drawing of a pattern on the surface of the object by radiating charged particles such as an electron beam 2 on the object such as a sample 7 installed in the vacuum chamber 6. <P>SOLUTION: An electrically charged particle application apparatus includes a radical generating means for generating radical 19 coming into contact with a charged particle irradiated surface of the object such as the sample 7 in the vicinity of the object, for example, a gas supplying means such as a gas supplying source 14 and a gas conducting port 16 supplying gas 15 so that it comes into contact with the electrically charged particle irradiated surface of the object, and a UV radiating apparatus 18 radiating ultra violet rays 17 on the electrically charged particles irradiated surface of the object. Thus, the charge on the electrically charged particle irradiated surface of the object is speedily neutralized by the radical 19 and the build up of the charge and the electrifying can be prevented regardless of the irradiated portion or the non-irradiated portion of the charged particles. On the other hand, since the radical 19 is generated in the vicinity of the object and disappears in a short period of time, the physical damage to the vacuum chamber 6 can be prevented by the radical 19. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a charged particle application apparatus that irradiates an object with charged particles and analyzes the object or draws a pattern on the surface thereof, and particularly relates to a technique for preventing charge-up on the surface of the object.

  FIG. 4 shows a scanning electron microscope (SEM) which is one of charged particle application apparatuses. In general, in a scanning electron microscope, an electron beam (charged particle) 2 emitted from an electron gun 1 is focused by a focusing lens 3, deflected by a deflecting plate 4, and a semiconductor wafer placed in a vacuum chamber 6 by an objective lens 5. The secondary electron 8 is focused on the sample 7 such as a semiconductor chip, and the secondary electron 8 emitted from the sample 7 is detected by the secondary electron detector 9. The sample 7 is scanned with the electron beam 2. Based on the secondary electrons 8 detected at the time, image processing is performed by a device (not shown), and the uneven pattern on the sample surface is displayed on the screen. Reference numeral 10 denotes a vacuum pump that exhausts the inside of the vacuum chamber 6 to a predetermined degree of vacuum, and 11 denotes a sample stage.

  However, in the conventional scanning electron microscope, for example, when observing the shape of the insulating film formed on the Si wafer, the electrons irradiated by the electron gun 1 do not flow into the substrate side, and the surface of the insulating film is charged (charged). The secondary electron image may become invisible. In order to avoid this, a method of depositing and observing a conductive material such as Au or Cu thinly (about 10 nm) on the sample surface has been used for a long time, but Au, which is not originally necessary for forming a semiconductor integrated circuit element, An evaporation process of Cu or the like is required, and in-line observation for observing the product being diffused is not possible.

  In charged particle application equipment such as a scanning electron microscope, incident charges are accumulated in an insulating region such as a photoresist on the surface of the substrate, and a high electric field is generated in the insulating material. The electronic circuit may be destroyed.

Therefore, in the scanning electron microscope shown in FIG. 5 or the like, the plasma 13 generated by the plasma generator 12 is introduced so as to come into contact with the sample surface irradiated with the charged particles, so that the incident charge is generated on the sample surface. It has been proposed to neutralize and prevent accumulation (Patent Document 1).
Japanese Patent Laid-Open No. 7-45227

  However, in the method of introducing plasma as described above, charge accumulation and charging at the site where charged particles are irradiated can be avoided, but plasma diffuses to other sites and causes electrical damage to the sample (object). In addition to giving charge accumulation (charging to non-irradiated sites), physical damage to the inner wall of the vacuum chamber (sputtering by radicals, etc.), and contamination by heavy metals, etc. are also a concern.

  In view of the above problems, the present invention can prevent charge accumulation and charging on the surface of an object regardless of whether the charged particle is irradiated or non-irradiated, and can also prevent physical damage in a vacuum chamber. The object is to provide an apparatus.

  In order to solve the above-described problems, the present invention provides a charged particle application apparatus for performing analysis of an object or drawing a pattern on the surface of an object by irradiating the object placed in a vacuum chamber with charged particles. A radical generating means for generating radicals in contact with the charged particle irradiation surface in the vicinity of the object is provided. According to this, the charge on the charged particle irradiation surface of the target can be quickly neutralized by radicals, and charge accumulation and charging can be prevented regardless of whether the charged particle is irradiated or not. On the other hand, radicals are generated in the vicinity of the object, but since the time in which they can exist as radicals is short and the side walls of the vacuum chamber cannot be reached, physical damage to the vacuum chamber due to radicals can also be prevented.

  The radical generating means can be composed of a gas supply means for supplying a gas so as to come into contact with the charged particle irradiation surface of the object and a UV irradiation apparatus for irradiating the charged particle irradiation surface of the object with ultraviolet rays. The gas supplied to the charged particle irradiation surface is radicalized on the charged particle irradiation surface and used for neutralization.

  The gas is preferably one of oxygen and ozone, or a mixture of both, and the UV irradiation device irradiates ultraviolet rays having wavelengths of 185 nm and 254 nm. This is because the oxygen radicals generated thereby are highly reactive.

  The charged particle application apparatus of the present invention can quickly neutralize the charge on the charged particle irradiation surface of the target object with radicals, thereby preventing charge accumulation and charging regardless of whether the charged particle is irradiated or not. It is possible to prevent physical damage to the vacuum chamber due to the radicals, and contamination of heavy metals and the like.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing the configuration of a scanning electron microscope, which is a charged particle application apparatus according to the first embodiment of the present invention. Members having the same functions as those of the prior art described above with reference to FIG. 4 are denoted by the same reference numerals as those in FIG.

  1 scans an electron beam (charged particle) 2 emitted from an electron gun 1 between a vacuum chamber 6 in which a sample 7 such as a semiconductor wafer or a semiconductor chip is installed and an electron gun 1. A focusing lens 3 for focusing, a deflection plate 4 for deflecting the electron beam 2, and an objective lens 5 for imaging the electron beam 2 on the sample 7 are arranged, and the sample 7 is placed in the vacuum chamber 6. A sample stage 11 and a secondary electron detector 9 for detecting the secondary electrons 8 emitted from the sample 7 are disposed outside the vacuum chamber 6 so that the inside of the tank has a predetermined degree of vacuum. A vacuum pump 10 is provided.

  This scanning electron microscope differs from the conventional one in that a gas inlet 16 for introducing a gas 15 into the vacuum chamber 6 so as to be in contact with the surface of the sample 7 connected to the gas supply source 14 and the surface of the sample 7 A UV irradiation device 18 that irradiates ultraviolet rays 17 is disposed on the surface of the sample 7 so that radicals 19 that contact the surface of the sample 7 can be generated in the vicinity of the surface of the sample 7. As the gas 15, a reactive gas such as ozone, specifically, a mixed gas of oxygen and ozone, or one of oxygen gas and ozone gas can be preferably used.

The operation when observing the surface of the sample 7 with the scanning electron microscope will be described.
The inside of the vacuum chamber 6 is evacuated by a vacuum pump 10 to a predetermined degree of vacuum, for example, about 0.1 to 30 Pa, and after completion of evacuation, the sample 7 is placed on the sample table 13 by a loading mechanism (not shown).

  Next, while the gas 15 is supplied from the gas supply source 14 through the gas inlet 16 so as to be evenly distributed on the surface of the sample 7, the degree of vacuum in the tank is adjusted to about 0.1 to 30 Pa by the vacuum pump 10. Next, the UV irradiation device 18 is turned on to irradiate the surface of the sample 7 with ultraviolet rays 17 having wavelengths of 185 nm and 254 nm.

  As a result, the ultraviolet rays 185 nm are absorbed by oxygen in the gas 15 to generate ozone, while the ultraviolet rays 254 nm are absorbed by ozone and oxygen radicals 19 are generated. In addition, it is necessary to arrange | position the gas inlet 16 and the UV irradiation apparatus 18 so that this photoexcitation reaction may occur on the sample 7 surface. Here, the gas inlet 16 opens to the side of the sample stage 13 so as to create a gas flow in the direction along the surface of the sample 7, and a plurality of UV irradiation devices 18 are arranged obliquely above the sample stage 13. The UV irradiation device 18 may be arranged to irradiate the entire surface of the sample 7 with ultraviolet rays, or may be arranged to irradiate only the observation portion locally.

  In this state, an electron beam (charged particle) 2 is emitted from the electron gun 1 and scanned on the sample 7 through the deflection plate 4 and the objective lens 5, and secondary electrons 8 emitted from the sample 7 are detected as secondary electrons. The image is detected by the device 9 and subjected to image processing by a device (not shown), and an image of the concavo-convex pattern on the surface of the insulating film such as a silicon oxide film formed on the sample 7 in a predetermined pattern is displayed on the screen.

  At that time, the oxygen radicals 19 (excited oxygen atoms) excited as described above and in contact with the surface of the sample 7 adsorb charged particles incident on the surface of the sample 7 to neutralize the charge. 7 Accumulation of charge on the surface and charging are avoided. As a result, the image of the uneven pattern on the surface of the sample 7 is clearly displayed. It is possible to prevent inconvenience due to charge accumulation that has occurred in the above-described conventional apparatus, for example, electric field due to charge is concentrated on the substrate side, and depending on the strength, the insulating film on the surface of the sample 7 can be destroyed.

  In this embodiment, the gas 15 is always introduced through the gas introduction port 16 and the surface of the sample 7 is always irradiated by the UV irradiation device 18. (Intermittent irradiation) or just after the observation is complete.

  As shown in FIG. 2, the UV irradiation device 18 combines two types of UV lamps 18a and 18b that generate ultraviolet rays having different wavelengths, and emits ultraviolet rays of 185 nm with one UV lamp 18a, and the other UV lamp. It is convenient to emit ultraviolet light 254 nm at 18b. The two types of UV lamps 18a and 18b may be arranged alternately by using a plurality of UV lamps 18a and 18b as shown in the figure. Moreover, you may comprise and arrange as an independent UV irradiation apparatus for each wavelength, and you may use the lamp | ramp which can generate | occur | produce both wavelengths simultaneously like a quartz low pressure mercury lamp.

FIG. 3 is a cross-sectional view showing a configuration of a focused ion beam drawing apparatus which is a charged particle application apparatus according to the second embodiment of the present invention.
This focused ion beam drawing apparatus is different from the above-described scanning electron microscope in that an ion source 20, for example, a gallium ion source is installed in place of the electron gun 1 and the secondary electron detector 9, and this ion source 20 The ion beam 21 radiated from and accelerated by an acceleration electrode (not shown) is incident on the sample 7 to draw a fine pattern on an insulating film such as a silicon oxide film.

  Also in this focused ion beam drawing apparatus, radicals are generated on the surface of the sample 7 by the gas 15 supplied from the gas supply source 14 and the gas introduction port 16 and the ultraviolet rays 17 irradiated from the UV irradiation apparatus 18, thereby generating the ion beam 21. Since the charged particles incident on the sample 7 can be neutralized on the surface of the sample 7, an extremely fine pattern can be drawn with high accuracy. In the conventional apparatus, when the surface of the insulating film is charged, the ion beam is affected by the electric field, which is superior to the fact that it is difficult to accurately produce a fine pattern.

Also in this focused ion beam drawing apparatus, the introduction of the gas 15 and the irradiation of the ultraviolet rays 17 may be performed constantly, or may be performed only at regular intervals or after the end of observation.
In each of the above-described embodiments, the case where the surface insulator is a silicon oxide film has been described. However, a photosensitivity such as a silicon nitride film, a silicon oxynitride film, a refractory metal oxide film, a photoresist, or the like that is commonly used is used. Even if it is an organic polymer film | membrane, it can process similarly and can acquire the same effect.

  Moreover, although the scanning electron microscope has been described as an example of a charged particle applied analyzer and the focused ion beam drawing apparatus is described as an example of a charged particle applied drawing apparatus, the invention is not limited thereto. Charged particle application analyzers include transmission electron microscope (TEM), Auger Electron Spectroscopy (AES), secondary ion mass spectrometer (SIMS), etc. The charged particle application drawing apparatus may be an electron beam drawing apparatus, and both have the same operations and effects as described above.

  Furthermore, by applying the apparatus structure of the present invention, it is possible to remove organic contamination adhering to the sample surface due to charged particles from the electron gun 1 or the ion source 20. This uses the fact that the bond of organic compound is cut by UV, and the organic compound on the UV irradiation surface contains free radicals such as C, H, O, N radicals, and C, H, O, N. However, the excited oxygen atom (O radical) has a strong oxidizing power, and reacts with other free radicals or excited molecules to volatilize and remove. For this purpose, it is advantageous that the gas introduced into the vacuum chamber 6 is ozone or oxygen, but it is possible to generate radicals with other gases and other wavelengths and use them for neutralization of charged particles.

  The charged particle application apparatus of the present invention is useful for analysis and processing of semiconductor wafers and semiconductor chips.

Sectional drawing of the scanning electron microscope which is a charged particle application apparatus in 1st Embodiment of this invention Configuration diagram of UV irradiation apparatus used in charged particle application apparatus of the present invention Sectional drawing of the focused ion beam drawing apparatus which is a charged particle application apparatus in 2nd Embodiment of this invention Sectional view of a conventional scanning electron microscope Sectional view of another conventional scanning electron microscope

Explanation of symbols

1 Electron Gun 2 Electron Beam 6 Vacuum Chamber 7 Sample 8 Secondary Electron 9 Secondary Electron Detector
14 Gas supply source
15 gas
16 Gas inlet
17 UV
18 UV irradiation equipment
19 radical
20 Ion source
21 Ion beam

Claims (3)

  In a charged particle application apparatus for irradiating an object placed in a vacuum chamber with charged particles to analyze the object or to draw a pattern on the object surface, the radical contacting the charged particle irradiation surface of the object is A charged particle application apparatus provided with radical generating means for generating in the vicinity of an object.   The radical generating means includes a gas supply means for supplying a gas so as to come into contact with a charged particle irradiation surface of an object, and a UV irradiation device for irradiating the charged particle irradiation surface of the object with ultraviolet rays. 1. The charged particle application apparatus according to 1.   The charged particle application apparatus according to claim 2, wherein the gas is one of oxygen and ozone, or a mixture of both, and the UV irradiation apparatus irradiates ultraviolet rays having wavelengths of 185 nm and 254 nm.

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