JP2009086428A - Photomask defect correction method and defect correction apparatus using charged particle beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently suppress charge-up of an isolated pattern without damaging the pattern in photomask defect correction using a charged particle beam.
SOLUTION: A conductive coil spring 3 is formed of a focused ion beam induced chemical vapor deposition metal film at the tip of a conductive probe 1 and the contact pressure with a mask pattern is relaxed by the coil spring 3 to form an isolated pattern 4 Defect correction is performed with the focused ion beam 7 after the continuity is taken and charge-up does not occur. The thickness and radius of the coil spring 3 produced by focused ion beam induced chemical vapor deposition are controlled by controlling the raw material gas pressure, the beam current, the scanning direction, and the speed so as to obtain an appropriate spring constant.
[Selection] Figure 1

Description

  The present invention relates to a method and apparatus for correcting a defect in an isolated pattern of a photomask using a charged particle beam apparatus, and more particularly, to a method and a mechanism for suppressing charge-up when an isolated pattern is corrected.

  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 a transfer original of a reduction projection exposure apparatus, has been conventionally performed using a laser or a focused ion beam (FIB). However, the resolution is insufficient with lasers, and defects in the most advanced fine patterns cannot be corrected. With focused ion beams, the wavelength of the light source of the reduction projection exposure apparatus is shortened, so that gallium is used as the primary beam. Imaging damage (decrease in transmittance) of the glass part has become a problem. Therefore, there is a demand for a defect correction technique that can correct a fine pattern defect and that does not cause imaging damage. Recently, a method has been proposed in which a gallium implantation layer is thinned using a low acceleration voltage even in a focused ion beam, and the transmittance is recovered by removing the thin gallium implantation layer by cleaning (Non-patent Document 1). In addition, a photomask defect repair apparatus using an electron beam without using an ion beam (in principle, no implantation into gallium) has been developed (Non-patent Document 2).

  However, since the photomask is a glass film on which a light-shielding metal film is deposited, charge-up occurs due to excessive charges caused by ion beam irradiation. The charge-up can be mitigated by irradiating the electron beam to neutralize the positive charge of the ion beam, but it is difficult to completely remove the charge-up when the area of the metal film pattern is small (isolated pattern) It is. When the charge-up occurs, there is a problem that the image quality of the secondary electron image is deteriorated and the drift is generated, so that the processing accuracy is lowered. The problem of charge-up remains even when a photomask defect is corrected using an electron beam. It is possible to eliminate the charge-up by bringing a grounded sharp conductive probe into contact with the isolated pattern, but it is difficult to make contact, and if the contact is weak, the continuity cannot be sufficiently obtained and the charge-up will not be improved. If it was strong, there was a problem of damaging the pattern.

Recently, micro-springs called nanosprings can be formed by focused ion beam induced chemical vapor deposition (FIB-CVD) films using FIB. It is possible to easily control the growth direction of the focused ion beam induced chemical vapor deposition film by controlling the source gas pressure, beam current, scanning direction and speed, and various nano shapes other than nano springs are formed. Yes. It has also been shown that the spring constant can be controlled by controlling the radius of the nanospring (Non-patent Document 3).
Y. Itou, et al. Proc. Of SPIE 599259924Y-1-59924Y-8 (2005) K. Edinger, H. Becht, J. Bihr, V. Boegli, M. Budach, T. Hofmann, HP Coops, P. Kuschnerus, J. Oster, P. Spies, and B. Weyrauch, J. Vac. Sci. Technol. B22 2902-2906 (2004) Kenichiro Nakamatsu, Kazuhiro Kanda, Yuichi Haruyama, Takashi Minato, Shinji Matsui, Proceedings of the 54th JSAP Related Lecture Meeting 793 (2007)

  An object of the present invention is to overcome the problems caused by charge-up at the time of defect correction of an isolated pattern of a photomask using a charged particle beam apparatus, and to prevent charge-up efficiently without damaging the isolated pattern. And

  A focused ion beam induced chemical vapor deposition metal film formed with a conductive coil spring at the tip of a conductive probe is used for grounding an isolated pattern. The coil spring is pressed against the isolated pattern to establish conduction while relaxing the contact pressure.

  The thickness and radius of the coil spring produced by focused ion beam induced chemical vapor deposition are controlled by controlling the raw material gas pressure, the beam current, the scanning direction, and the speed so as to obtain an appropriate spring constant.

  It is possible to prevent the isolated pattern from being charged up by bringing a conductive coil spring provided at the tip of the conductive probe into contact with the isolated pattern to establish conduction. Since observation and defect correction can be performed without charge-up, defect correction with high processing accuracy can be performed even with an isolated pattern.

  By making the spring constant appropriate, the contact pressure between the coil spring and the mask pattern can be adjusted appropriately, conduction with the isolated pattern can be achieved without damaging the pattern, and charge-up during defect correction can be suppressed.

  Hereinafter, embodiments of the present invention using a focused ion beam will be described in detail with reference to the drawings.

  A photomask having defects is introduced into a photomask defect correcting apparatus having a focused ion beam column having a light shielding film source gas gun, a metal deposition film source gas gun, and a gas gun for gas assist etching. Next, the XY stage is moved so that the defect position found by the optical defect inspection apparatus comes to the center of the visual field.

FIG. 1 is a schematic cross-sectional view for explaining a case where a black defect of an isolated pattern is corrected using the photomask defect correcting apparatus according to the present invention. First, the photomask defect correcting apparatus according to the present invention will be described. A focused ion beam column 14 for irradiating the focused ion beam 7 above the black defect 8 of the isolated pattern 4 of the photomask is provided. A gas gun 9 is provided for spraying an etching gas on the irradiation position of the focused ion beam 7 from the focused ion beam column 14. The charge removal mechanism includes a conductive probe 1, a conductive coil spring 3, and a conductive probe drive mechanism 2. The conductive probe 1 is attached to the conductive probe driving mechanism 2 obliquely downward toward the photomask. The conductive coil spring 3 is attached below the tip of the conductive probe in a direction in which the spring axis is perpendicular to the photomask surface. The conductive probe driving mechanism 2 drives the conductive probe 1 three-dimensionally.

Next, a black defect correction method using this photomask defect correction apparatus will be described.
A focused ion beam 7 is irradiated from the focused ion beam column 14 to the isolated pattern 4 of the photomask in which the normal pattern 4 and the isolated pattern 5 are formed on the glass substrate 6, and the region including the defect is observed. At this time, if the isolated pattern 4 does not appear to be charged up even after charge neutralization with an electron beam of several hundreds eV from an electron beam irradiation apparatus (not shown), the lower end of the conductive coil spring 3 is the isolated pattern 4 The XY drive amount and direction of the conductive probe drive mechanism 2 are adjusted so that the position is directly above. Next, the conductive probe 1 is moved little by little in the Z direction by the conductive probe driving mechanism 2 to bring the coil spring 3 into contact with the isolated mask pattern 4 and the amount of movement in the Z direction is adjusted to adjust the coil spring 3 and the isolated mask pattern. Adjust the contact pressure with 4 to establish continuity. Since the conductive probe 1 is lowered to the ground potential, an image without charge-up can be taken by this conduction. The defect of the isolated pattern 4 is recognized with this image without charge-up, and in the case of the black defect 8, iodine or xenon fluoride is introduced as an assist gas from the physical sputtering or the assist etching gas gun 9 and only the black defect portion 10 The ion beam 7 accelerated to ˜30 kV is selectively irradiated, and the black defect 8 is removed and corrected by gas assist etching.

FIG. 2 is a schematic sectional view for explaining a case where a white defect of an isolated pattern is corrected.
Similar to the case of correcting the black defect, an image without charge-up is obtained and the defect recognition of the isolated pattern 4 is performed. If the defect is a white defect 11, a carbon-containing light-shielding film source gas such as naphthalene or phenanthrene is introduced from the gas gun 10 for introducing the light-shielding film raw material gas, and the ion beam 7 accelerated to 10 to 30 kV is selected only for the white defect portion. Irradiating and depositing a light-shielding film 12 on the defect portion by focused ion beam induced chemical vapor deposition to correct the white defect 11.

FIG. 3 is a schematic cross-sectional view illustrating a method for producing a coil spring at the tip of a conductive probe.
The coil spring of the focused ion beam induced chemical vapor deposition metal film formed at the tip of the conductive probe 1 is formed as follows. The conductive probe 1 is rotated around the horizontal component in the probe axial direction so that its tip is directed upward and toward the focused ion beam column, and the tip is irradiated with an ion beam from above and the metal deposition film raw material Metal deposition film such as W (CO) ₆ (hexacarbonyltungsten) or C ₉ H ₁₆ Pt ((trimethyl) methylcycropentadienyl-platinum) as source gas from gas gun 13 for gas introduction Supply raw material gas. At this time, the coil spring 3 is manufactured by controlling the raw material gas pressure, the beam current, or the scanning direction and speed of the ion beam so as to have an appropriate thickness and radius. After the production, the conductive probe 1 is rotated again and the coil spring 3 is directed downward.

  Although the case where the defect of the isolated pattern of the photomask is corrected with the focused ion beam has been described above, the present invention similarly corrects the defect of the isolated pattern of the photomask using an electron beam with a low acceleration voltage so as not to be charged up. Can also adapt.

It is a schematic sectional drawing explaining the case where the black defect of an isolated pattern is corrected. It is a schematic sectional drawing explaining the case where the white defect of an isolated pattern is corrected. It is a schematic sectional drawing explaining the production method of a coil spring at the electroconductive probe front-end | tip.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive probe 2 Conductive probe drive mechanism 3 Coil spring 4 Isolated pattern 5 Normal pattern 6 Glass substrate 7 Focused ion beam 8 Black defect 9 Assist etching gas gun 10 Light-shielding film material gas gun 11 White defect 12 Deposited light-shielding film 13 Metal Position film source gas gun 14 Focused ion beam column

Claims (6)

  A conductive coil spring is formed at the tip of the conductive probe, and the conductive probe is driven in the X, Y, or Z direction so that the coil spring is brought into contact with the isolated pattern while suppressing the charge-up of the isolated pattern. A defect correction method for a photomask using a charged particle beam, wherein a defect of a pattern is corrected using a charged particle beam.   2. The photomask defect correcting method according to claim 1, wherein the coil spring is a focused ion beam induced chemical vapor deposition metal film.   3. The photomask defect correcting method according to claim 2, wherein a contact pressure between the coil spring and the isolated pattern is adjusted by controlling a thickness and a radius of the coil spring. A charged particle beam column for irradiating the defect position of the isolated pattern of the photomask with a charged particle beam;
A gas gun for spraying an etching gas or a deposition gas to an irradiation position of the charged particle beam from the charged particle beam column;
A charge removing mechanism having a conductive probe, a conductive coil spring attached to the tip of the conductive probe, and a conductive probe driving mechanism for three-dimensionally driving the conductive probe;
A photomask defect correcting device comprising:   The charged particle beam column is a focused ion beam column, the conductive probe is attached obliquely downward toward a photomask, and the conductive probe driving mechanism moves the conductive probe around the horizontal component in the probe axial direction. The photomask defect correction device according to claim 4, further comprising a rotation mechanism for rotating the photomask.   The coil spring rotates the conductive probe so that the tip of the conductive probe faces the focused ion beam column side, blows a deposition gas from the gas gun on the tip, and the focused ion beam mirror. 6. The photomask defect correcting device according to claim 5, wherein the photomask defect correcting device is formed by induced chemical vapor deposition by irradiation with a focused ion beam from a cylinder.

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