JP2005234047A - Method for repairing halftone defect in binary mask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To repair a halftone defect causing imperfect light shielding in a binary mask with high accuracy and excellent transfer properties. <P>SOLUTION: The following phenomenon is utilized; an FIB-CVD light shielding film 8 with little halo does not grow on a gallium implanted chromium film but can grow on a glass part 6 exposed by etching. Part of the halftone defect 2 in the binary mask to which the FIB-CVD light shielding film 8 is made less attachable by implantation of gallium of focused ion beams 1 is shaved up to a glass substrate by gas assisted etching. The FIB-CVD light shielding film 8 is then grown from the exposed glass part 6 to repair the halftone defect. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a defect correction method for a photomask used for pattern transfer onto a wafer.

  With the progress of miniaturization of semiconductor integrated circuits, the pattern on a photomask which is an original pattern transfer is also miniaturized. Since the photomask is an original plate, if there is a defect, a defect is created in all the transferred objects, and therefore it is required to be defect-free. Since defects are inevitably generated in the mask processing process, defects have been corrected using a laser. However, when the pattern is miniaturized, the number of defects that must be corrected becomes smaller, and the laser cannot handle such fine defects. Therefore, correction using a focused ion beam (FIB) has recently been used. ing.

  Mask defects include black defects, which are surplus patterns compared to normal patterns, white defects, which are insufficient patterns compared to normal patterns, and halftone defects where the light shielding film pattern is partially thin and allows light to pass through. is there. Black defects and white defects are corrected by FIB gas-assisted etching or FIB-CVD light shielding film (for example, Non-Patent Document 1). Halftone defects can also be corrected by FIB, but FIB-CVD light shielding film must be attached to the binary pattern. When correcting halftone defects that are not completely shielded, some of the FIB primary beam gallium is used. As described above, when the light-shielding film pattern is injected into chromium, there is a problem that an FIB-CVD film having excellent characteristics as a light-shielding film cannot be grown on the chromium film.

  The above problem can be corrected by cutting the entire halftone part with FIB gas-assisted etching and applying a FIB-CVD light shielding film. In some cases, overetching occurs in the periphery of the processed portion, thereby deteriorating the transfer characteristics of the defect correction portion.

  Halftone defects can also be corrected by depositing a FIB-CVD film using another FIB-CVD light shielding film source gas that adheres even to a gallium-implanted chromium film. There is a problem that an undesired thin film (halo component) is large in the periphery of the film, thereby deteriorating the transfer characteristics of the defect correction portion.

There is a need for a defect correction method with high accuracy and excellent transfer characteristics, without over-etching or halo, as described above, for half-tone defects in a chromium mask in which gallium of a focused ion beam is implanted and light shielding is not complete.
R. Hagiwara, A. Yasaka, K. Aita, O. Takaoka, Y. Koyama, T. Kozakai, T. Doi, M. Muramatsu, K. Suzuki, Y. Sugiyama, O. Matsuda, M. Okabe, M. Hasuda, T. Adachi, Y. Morikawa, M. Nishiguchi, Y. Sato, N. Hayashi, T. Ozawa, Y. Tanaka, and N. Yoshioka, Proc. Of SPIE 5130 510-519 (2003)

  The present invention seeks to enable correction of halftone defects where the light shielding of the binary mask is not perfect.

  Although the FIB-CVD light-shielding film with few halos does not grow on the chromium film implanted with gallium, it can be used to grow on the glass part exposed by etching. First, a glass substrate is formed by gas-assisted etching with a gap that can cover a part of the halftone defect of the binary mask, which has become difficult to attach to the FIB-CVD light shielding film by focused ion beam gallium implantation. Grind up to. Next, a FIB-CVD light shielding film is grown from the exposed glass portion to correct the halftone defect.

  Since the FIB-CVD light-shielding film with less halo can be grown from the glass portion exposed by etching, halo does not occur around the correction portion and the transfer characteristics of the correction portion are not deteriorated. The FIB-CVD light-shielding film grown from the glass part also grows in the horizontal direction, so it can cover the remaining halftone defects.

  Since only a part of the halftone defect is etched, a large over-etched portion that deteriorates transfer characteristics does not occur. It can also be corrected in a shorter time than growing a thick FIB-CVD light shielding film that can cut off all the halftone defects and sufficiently shield the light.

  A binary mask having a halftone defect with incomplete light shielding is introduced into the focused ion beam apparatus and moved to the coordinates where the defect is found by the defect inspection apparatus. The ion beam 1 accelerated from several kV to several tens of kV and focused by ion optics to a few nm to several hundred nm is scanned in a region including a halftone defect, and a secondary electron signal or The secondary ion signal is taken in to acquire a secondary electron image or secondary ion image of the region including the halftone defect, and the defect region 2 to be corrected is recognized. When scanning a focused ion beam, the binary mask is a glass or quartz substrate, which is an insulator, with a chrome film pattern. If only the ion beam is charged, the image will be distorted or invisible. The irradiation is performed while irradiating an electron beam of several hundred pA to several nA over a wide area at the same position to neutralize excessive charges. As shown in FIG. 1 (a), while the portion 6 of the recognized halftone defect 2 is supplied from the etching assisting gas supply system 5, the focused ion beam 1 is selectively irradiated and etched to the glass substrate 3 by the etching function. The interval d at which a part of the halftone defect is etched away is an interval that can cover the halftone defect left by the lateral growth of the light shielding film. As shown in FIG. 1 (b), the defect area including the shaved portion is recognized again, and only the area that was originally a halftone defect is focused while supplying the light shielding film raw material gas from the light shielding film raw material supply system 7. If the ion beam is selectively irradiated, the FIB-CVD light shielding film 8 grows from the glass portion 6 exposed by etching, and this FIB-CVD film also grows in the lateral direction, so that it can also cover the remaining halftone defects. Incomplete halftone defects in the light shielding of the binary mask can be corrected.

  In addition to the stripe shape as shown in FIG. 2, a lattice shape as shown in FIG. 3 or a spiral as shown in FIG. 4 is used as a method of exposing part of the halftone defect 2 in the first process by etching. If the spacing is sufficient to cover the halftone defect 2 left by the lateral growth of the light-shielding film, the FIB-CVD light-shielding film 8 can be grown. Tone defects can be corrected.

  If the etching of a part of the halftone defect 2 in the first step is not a vertical cross section as shown in FIG. 1, but a tapered cross section as shown in FIG. Since the lateral growth of 8 is promoted, even if etching at a wider interval than in the case of a vertical cross section as shown in FIG. Can do.

It is a schematic sectional drawing which best expresses the feature of the present invention. It is a top view which shows one Example of the method of etching a part of halftone defect by this invention. It is a top view which shows one Example of the method of etching a part of halftone defect by this invention. It is a top view which shows one Example of the method of etching a part of halftone defect by this invention. It is a schematic sectional drawing which shows one Example of the method of etching a part of halftone defect by this invention.

Explanation of symbols

1 Focused ion beam
2 Incomplete shading halftone defect
3 Glass substrate
4 Chromium film
5 Etching support gas supply system
6 Etching part
7 Shading film source gas supply system
8 FIB-CVD light shielding film

Claims (5)

  A part of the half-tone defect with incomplete light shielding of the binary mask is cut into the glass substrate by the etching function of the focused ion beam, and a focused ion beam CVD light-shielding film is grown from the etched part to correct the half-tone defect. A method for correcting a halftone defect in a photomask, which is characterized in that:   2. The method for correcting a halftone defect in a photomask according to claim 1, wherein a part of the halftone defect is etched in a stripe shape.   2. The method of correcting a halftone defect in a photomask according to claim 1, wherein a part of the halftone defect is etched in a lattice shape.   2. The method for correcting a halftone defect in a photomask according to claim 1, wherein a part of the halftone defect is cut in a spiral shape.   2. The method for correcting a halftone defect of a photomask according to claim 1, wherein a cross-sectional shape of a part of the halftone defect is tapered.

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