JP2006155983A - Destaticizing method of electron beam defect correction device and its device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove charges accumulated during the defect correction of a photomask by electron beams even in an electron beam defective correction device of which the test piece chamber is vacuum. <P>SOLUTION: Nitrogen introduced in the electron defect correction device by a gas introducing system 1 is ionized by α-rays generated by an α-ray source 2 such as polonium, and the ionized nitrogen is irradiated on a portion 4 charged up by the irradiation of electron beams, and destaticizes it. Otherwise, nitrogen or water vapor introduced in the electron beam defect correction device by the gas introducing system 1 is ionized by soft X-rays and the ionized nitrogen or vapor is irradiated on the portion charged up by the irradiation of the electron beams, and destaticizes it. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a charge eliminating method for a defect correcting apparatus using an electron beam, particularly a photomask defect correcting apparatus.

  Lithography has responded to the demand for miniaturization of semiconductor integrated circuits by shortening the wavelength of the light source of the reduction projection exposure apparatus and increasing the NA. Photomask defect correction, which is required to be defect-free in the transfer master of a reduction projection exposure apparatus, has been conventionally performed using a laser or a focused ion beam. In the focused ion beam, the imaging damage (decrease in transmittance) of the glass due to the implantation of gallium used in the focused ion beam has become a problem, and defects in fine patterns can be corrected and defect correction without imaging damage Technology is required.

  In response to the above-described demand, recently, an electron beam having a high resolution and a short wavelength and having no imaging damage has begun to be used for photomask defect correction. Since there is no photomask imaging damage in the electron beam, it is possible to pursue the processing accuracy by imaging at a high magnification and additional processing of correction points, and it is highly expected as a next-generation defect correction technology. However, when observing a photomask which is an insulator with an electron beam device, various ideas have been made because the image becomes invisible due to charge-up or the image drifts. As countermeasures for charge-up, observation and defect correction are performed with an acceleration voltage of about 1000 V, which balances the inflow of primary electrons and the emission of secondary electrons to the specimen so that charge accumulation does not occur (non-patented) Reference 1). In addition, irradiate a light positive ion beam such as helium or argon to neutralize the negative charge of the electron beam, or bring the conductive probe close to or in contact with the part charged up by irradiation of the electron beam. In some cases, charge is released to prevent charge-up.

  However, the conventional charge-up neutralization / relaxation measures described above do not completely remove the charge-up, and gradually accumulate charges on the glass and pattern edges. When it is sufficient to perform additional work on defect correction points, high-accuracy processing may not be possible due to the effects of charge-up as described above, so the charges accumulated on the glass and pattern edges can be removed efficiently. There is a need for a way to do that.

On the other hand, when neutralizing wafers and masks in the atmosphere, air molecules with a large static elimination effect are ionized with an α-ray source such as polonium or soft X-rays, and this ionized product is supplied to the place where it is charged up to eliminate static electricity. However, since there are no air molecules to ionize in the vacuum apparatus, neutralization using an α-ray source such as polonium or soft X-rays has not been performed (polonium: Non-Patent Document 2). Soft X-ray: Non-patent document 3).
T. Liang, T. Stivers, M. Penn, D. Bald, and C. Sethi, Proceedings of SPIE 5446 291-300 (2004) WV Brandt, Proceedings of SPIE 4562 600-608 (2001) Y. Tanaka, Y. Itou, N. Yoshioka, K. Matsuyama, and D. Dawson, Proceedings of SPIE 5446 751-758 (2004)

  An object of the present invention is to solve the above-mentioned problems and to remove charges accumulated during correction of electron beam defects in a photomask even in an electron beam defect correction apparatus in which a sample chamber is vacuum.

  Nitrogen is locally introduced into the working chamber of the electron beam defect correction apparatus by a gas introduction system having the same structure as the supply system used for supplying the etching gas and light shielding film raw material gas of the electron beam defect correction apparatus. This nitrogen is ionized by α rays emitted from an α ray source such as polonium, which is a radiation source arranged in the vicinity of the gas introduction system outlet in a vacuum. By supplying positively and negatively ionized nitrogen, the portion charged up by electron beam irradiation is discharged.

  Alternatively, nitrogen or water vapor is locally introduced into the working chamber of the electron beam defect correction apparatus using a gas introduction system having the same structure as described above. This nitrogen or water vapor is ionized by soft X-rays emitted from a soft X-ray irradiation apparatus, which is a radiation source arranged in the vicinity of the gas introduction system outlet in a vacuum. By supplying nitrogen or water vapor ionized positively and negatively, the portion charged up by electron beam irradiation is discharged.

  Since the locally supplied nitrogen is ionized in the gas introduction system, it is possible to remove the charge with α rays such as polonium in the vacuum apparatus. Since nitrogen is supplied locally, it does not place a heavy burden on the vacuum exhaust system, and it can return to the steady state in a short exhaust time after static elimination, and the effects of etching gas and light shielding film source gas used for correcting electron beam defects can be obtained. There is no hindrance. Nitrogen ionized positively and negatively can be transported to the place where it is charged up by the gas flow of the gas introduction system, so that excess charge can be neutralized efficiently. Excess ionized nitrogen is exhausted in the exhaust system, so no new charge-up occurs.

  Even with soft X-rays, the nitrogen or water vapor locally supplied by the gas introduction system is ionized, so that the static electricity can be removed even in a vacuum apparatus. Similar to α rays, nitrogen or water vapor ionized positively and negatively can be transported to the place where it is charged up by the gas flow of the gas introduction system, so that excess charge can be neutralized efficiently. Of course, excess ionized nitrogen and ionized water vapor are discharged through the exhaust system, so no new charge-up occurs.

Examples of the present invention will be described in detail below.
The photomask 14 in which the defect is found is introduced into the electron beam defect repair apparatus, and the XY stage is moved to the defect position found in the defect inspection apparatus. The defect-containing region is imaged by imaging the region including the defect with an electron beam 8 with an acceleration voltage that is difficult to charge up to about 1000 V, and a gas supply system 12 supplies an appropriate etching gas or light shielding film source gas according to the material of the defect 9 The black and white defects are corrected by repeatedly performing selective scanning only on the defective area while supplying the defect.

  The state where the etching gas and light shielding film source gas used in the electron beam defect correction are sufficiently exhausted if the high-precision additional processing of the defect correction location cannot be performed due to the accumulation of the electron beam irradiated in the above correction process Then, as shown in FIG. 1 (a), the valve of the gas introduction system 1 attached to the work chamber of the electron beam defect correction apparatus is opened, and nitrogen is locally introduced into the work chamber. Α rays 3 emitted from an α ray source 2 such as polonium disposed in the vicinity of the gas introduction system outlet in the vacuum are emitted toward the outlet of the gas introduction system 1. The α rays ionize the nitrogen to plus and minus, and the ionized nitrogen 5 is irradiated to the portion 4 that has been charged up due to the irradiation of the electron beam 8, and the excess charge is neutralized and neutralized. Of course, no electron beam irradiation is performed during the above-described static elimination step. After neutralization is completed, the nitrogen used for static elimination is exhausted sufficiently so as not to impede the effects of the etching gas and light shielding film raw material gas used for correcting electron beam defects.

  FIG. 2 (a) shows another embodiment. As shown in FIG. 2 (a), nitrogen or water vapor locally introduced into the work chamber by the gas introduction system 1 attached to the work chamber of the electron beam defect correction apparatus is arranged near the gas introduction system outlet in the vacuum. Soft X-rays 7 emitted from the X-ray irradiation device 6 are emitted toward the outlet of the gas introduction system 1. Nitrogen or water vapor is ionized positively and negatively by soft X-rays, and the ionized nitrogen or water vapor 5 is irradiated to the charged up portion 4 due to the irradiation of the electron beam 8, and the excess charge is neutralized and neutralized. Also in this case, the nitrogen or water vapor used for static elimination after the static elimination is sufficiently exhausted so as not to hinder the effects of the etching gas and the light shielding film raw material gas used for correcting the electron beam defects.

  After removing the charge by the above method, as shown in Fig. 1 (b) and Fig. 2 (b), recognize the portion 9 to be reworked with an electron beam 8 with an acceleration voltage that is difficult to charge up to about 1000V, and perform appropriate etching While supplying the gas and the light shielding film source gas 13 from the gas supply system 12, the selective scanning of the electron beam 8 is repeated only in the additional processing region 9, and the additional processing of the defect is performed. Furthermore, when additional work for the defect repair area is required and accuracy cannot be obtained due to charge-up, the above-mentioned alpha ray or soft X-gland static elimination and additional work using an electron beam are repeated to perform highly accurate defect repair.

It is a schematic sectional drawing in the case of neutralizing charge-up by an electron beam with nitrogen molecules ionized by α rays. FIG. 3 is a schematic cross-sectional view in the case of removing charge-up by an electron beam with nitrogen molecules or water molecules ionized by soft X-rays.

Explanation of symbols

1 Nitrogen (water vapor) gas introduction system
2 α-ray source (polonium)
3 alpha rays
4 Charge-up portion due to charge accumulation
5 Ionized nitrogen (water) molecules
6 Soft X-ray irradiation equipment
7 Soft X-ray
8 electron beam
9 Defects (additional machining area)
10 Glass or quartz substrate
11 Light-shielding film pattern
12 Etching gas or light shielding film source gas supply system
13 Etching gas or light shielding film source gas
14 Photomask

Claims (8)

Introducing nitrogen into the electron beam defect repair device;
Ionizing the introduced nitrogen;
Irradiating the ionized nitrogen to the part where the electrons on the sample are charged up, and removing electricity;
A method of neutralizing an electron beam defect correcting apparatus comprising:   The ionization method of the electron beam defect correction apparatus according to claim 1, wherein the ionization of nitrogen is performed using α rays.   The method of claim 2, wherein the nitrogen is introduced from a gas introduction system for spraying a gas to a sample, and the α-ray is irradiated toward a gas near an outlet of the gas introduction system. .   3. The method for neutralizing an electron beam defect correcting apparatus according to claim 2, wherein the α-ray source is polonium.     2. The method of claim 1, wherein the ionization of nitrogen is performed using soft X-rays. Introducing water vapor into the electron beam defect correcting device;
Ionizing the introduced water vapor;
Irradiating the ionized water vapor to the charged part of the electrons on the sample;
A method of neutralizing an electron beam defect correcting apparatus comprising:   7. The method for removing electricity from an electron beam defect correcting apparatus according to claim 6, wherein the ionization of the water vapor is performed using soft X-rays. A gas introduction system for spraying nitrogen or water vapor on the sample;
An electron beam defect correcting apparatus provided with a radiation source for irradiating the nitrogen or water vapor with ionizing radiation toward the vicinity of an outlet of the gas introduction system.

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