JP2008281721A - Method for correcting black defect in chromium mask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent overetching in glass caused when a black defect in a chromium mask is corrected by a photomask defect correcting device using a charged particle beam. <P>SOLUTION: An overetched portion 3 of glass is filled with a transparent film 6 by electron beam deposition using TEOS (tetraethoxy silane) or siloxane molecules as a material. The depth distribution in the overetched portion of the glass is obtained with an atomic force microscope, and the film thickness to fill the defect is controlled according to the distribution to flatten the surface of the filled transparent film. Otherwise, the transparent film is deposited to be higher than the normal glass surface, and the portion higher than the glass surface is scraped off by a mechanical process by an atomic force microscope with a fixed height so as to flatten the surface of the filled transparent film. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for correcting a black defect in a chrome mask of a charged particle beam photomask defect correcting apparatus, and more particularly, to a method for repairing an overetch of a glass substrate that occurs when a black defect in a chrome mask is corrected by etching.

  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 on the transfer master of a reduction projection exposure apparatus, has been performed using a laser or a focused ion beam. The defect of the pattern cannot be corrected, and the shortened wavelength of the light source of the reduction projection exposure apparatus causes the imaging ion damage (decrease in transmittance) of the glass part due to the implantation of gallium used as the primary beam in the focused ion beam. Therefore, there is a demand for a defect correction technique that can correct defects in fine patterns and that does not cause imaging damage.

  Under these circumstances, recently, an electron beam photomask defect correction device has been developed that corrects black defects by gas-assisted etching using an electron beam and deposits a light-shielding film by electron beam CVD to correct white defects (non-patent). Reference 1). Since imaging and processing are performed with an electron beam, the transmittance is not reduced due to high resolution and gallium implantation. In addition to the electron beam photomask defect correction apparatus, an apparatus that removes defects by mechanical processing using an atomic force microscope (AFM) technique has also been developed (Non-patent Document 2).

When correcting the black defect of the chrome mask by gas-assisted etching with the electron beam photomask defect correction device, if the correction is made so that overetching to the glass substrate part does not occur, the edge of the chrome film in the correction part will be required. However, if the edge of the chrome film in the correction part is raised, the etching selectivity of the chrome film and glass is low, so the glass part under the chrome film is also shaved and overetched. It was happening. This overetching of the glass part has a problem that a space line width is reduced due to a decrease in local transmittance of the correction part at the time of transfer and a line width at the time of defocusing is changed.
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) Y. Morikawa, H. Kokubo, M. Nishiguchi, N. Hayashi, R. White, R. Bozak, and L. Terrill, Proc. Of SPIE 5130 520-527 (2003) Special table 2006-504136

  The present invention relates to a problem of transfer characteristics such as a decrease in transmittance and a defocus characteristic in a defect correction portion caused by glass overetching that occurs when correcting a black defect in a chrome mask using a charged particle beam photomask defect correction apparatus. The object is to provide a means to overcome the points.

  In order to solve the above problems, the black defect correcting method according to the present invention is configured as follows.

  The black defect of the chrome mask is corrected by etching using a charged particle beam, and the overetched portion of the glass substrate of the chrome mask formed at the time of the correction is filled with a transparent film of electron beam deposition.

  When the charged particle beam is a focused ion beam, the overetched portion is further shaved with an AFM probe, and then filled with a transparent film of electron beam deposition.

  When the overetched portion is shaved with an AFM probe, the bottom surface of the shaved hole is made parallel to the surface of the glass substrate.

  In addition, the depth distribution of the overetched portion of the glass is obtained with an atomic force microscope, and the thickness of the transparent film to be filled is controlled according to the depth distribution so that the surface of the filled transparent film becomes flat. .

  Alternatively, in the above, the transparent film filling the overetched portion of the glass is filled so as to be higher than the surface of the glass substrate, and then the portion higher than the glass surface is scraped off using an atomic force microscope and buried. The film surface is flattened at the same height as the glass substrate surface.

  It is known that a transparent film can be deposited by electron beam CVD using tetraethoxysilane (TEOS) or siloxy acid as a source gas. In the present invention, this transparent electron beam CVD film is used to fill the overetched portion of the glass formed when the black defect of the chromium mask is corrected by electron beam gas assist etching.

  In order to avoid a decrease in optical characteristics due to unevenness, the buried film is made to be the same height as the glass surface. For this purpose, the depth distribution of the overetched portion of the glass is obtained by AFM, the transparent film thickness distribution is controlled according to the depth distribution, and the buried transparent film surface is flat at the same height as the glass substrate surface. To do.

  Alternatively, the transparent film is first filled so as to be higher than the normal glass surface, and then the portion higher than the glass surface (glass substrate surface) is flattened to the height of the glass surface by the AFM photomask defect correction device. Sharpen.

  Since the overetched portion is filled with a transparent film whose material is close to that of a glass substrate, the transmittance does not decrease (the line width decreases during transfer) when exposed at the exposure wavelength. Since the material is a transparent film close to the glass substrate, the phase effect is also close to that of the glass substrate, and the defocus characteristic deterioration (line width fluctuation at the time of focus fluctuation) can be mitigated.

  By flattening the surface of the buried transparent film, it is possible to avoid an increase in reflectivity and a decrease in optical characteristics (transfer characteristics) such as phase effect due to unevenness of the buried film.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  The present invention can be applied to the case where a black defect is corrected by etching with a charged particle beam including a focused ion beam.

  FIG. 1 is a schematic cross-sectional view for explaining a case where an electron beam transparent film deposit fills an overetched portion with an electron beam.

  A chrome mask having a mask pattern 1 having a black defect and a glass substrate 2 is introduced into an electron beam photomask defect correcting apparatus, and the black defect position found by the defect inspection apparatus is moved so as to come to the electron beam irradiation position. Black defects are corrected by etching with beam 4. A region where the electron beam gas assist etching process is performed when correcting the black defect of the chrome mask and a relative position from the drift marker for correcting the drift of the electron beam are recorded in advance.

  When the black defect is corrected using the electron beam, the overetched portion 3 is generated. The region including the overetched portion 3 is observed, and the region to be filled with the transparent film is determined from the stored two-dimensional shape information of the processing region and relative position information from the drift marker of the processing region (FIG. 1 (a )). Scan the electron beam 4 of several pA to several tens of pA only in the region determined while supplying TEOS or siloxy acid-based molecules from the supply system 5 as the transparent film source gas to the beam irradiation position, and deposit the transparent film 6 by electron beam CVD. Then, the overetched portion 3 of the glass at the black defect correction portion of the chrome mask is filled (FIG. 1 (b)).

  Next, a method for avoiding a decrease in optical characteristics (transfer characteristics) due to the unevenness of the buried transparent film will be described. A chrome mask with black defects corrected by etching using an electron beam is taken out of the electron beam photomask defect correction apparatus, and a 6-inch mask is introduced into an AFM apparatus that can observe the entire surface. Move the AFM probe 9 to the position of the black defect relatively found by the defect inspection device, and use the probe 9 with a small tip diameter and high aspect like carbon nanotubes to include the glass overetched part 3 To obtain a high-fidelity depth distribution (Fig. 2 (a)). The chromium mask whose depth distribution has been obtained is returned to the electron beam photomask defect correcting apparatus. The electron beam is moved to the position of the black defect found by the defect inspection apparatus, and the region including the overetched portion 3 is observed. The region to be filled with the transparent film is determined from the stored two-dimensional shape information of the processing region and the relative position information from the drift marker of the processing region, and the electron beam CVD is performed according to the obtained depth distribution of the overetched portion. The surface of the filled transparent film 6 is flattened by controlling the film thickness filled with (by making the transparent film thicker at deeper locations and by making the transparent film thinner at shallower locations) (FIG. 2 (b)).

  Alternatively, the transparent film 6 is buried by electron beam CVD so as to be higher than the normal glass surface 2 (FIG. 3 (a)), and a portion higher than the glass surface of the buried portion is scraped off by an AFM probe.

  Specifically, it is as follows.

  After the transparent film 6 is filled so as to be higher than the normal glass surface 2 by electron beam CVD (FIG. 3 (a)), the chromium mask is taken out from the electron beam photomask defect correcting apparatus. Next, the chrome mask is introduced into the AFM photomask defect correction apparatus, and the AFM probe is moved relative to the black defect position found by the defect inspection apparatus. Observe the area including the place where the transparent film 6 was applied, set the height of the tip of the tip higher than the glass surface 2 to the height of the glass surface, and the area with the surplus portion at that height By scanning, the portion higher than the glass surface is scraped off by mechanical processing of the processing probe 8 so that the surface of the buried transparent film 6 becomes flat (FIG. 3 (b)).

  The transparent film filling the overetched portion 3 can be produced not only by electron beam CVD using TEOS or siloxy acid-based molecules as raw materials, but also by dip pen nanolithography transparent films using transparent film materials as ink (see Patent Document 1). It is. Even when the overetched portion of the glass is filled with the transparent film of the dip pen nanolithography, in order to avoid the deterioration of the optical characteristics due to the unevenness of the filled transparent film, the surfaces of the above two kinds of transparent films to be filled are used. A planarization method can be applied.

  The present invention can also be applied to an over-etched portion that is formed when a black defect is corrected using a focused ion beam. FIG. 4 is a schematic cross-sectional view in the case where the present invention is applied to an overetched portion that can be formed at the time of correcting a black defect using a focused ion beam.

  When the ion source of the focused ion beam is gallium, gallium is implanted into the overetched portion. Gallium implanted into the overetched portion is removed with an AFM probe. For this purpose, a mask in which overetching has occurred due to the correction by the focused ion beam is introduced into the AFM photomask defect correction apparatus, and the AFM probe is moved relative to the black defect position found by the defect inspection apparatus. A region including the overetched portion 3 is observed by AFM in a three-dimensional shape, and the overetched portion 3 is dug deeper by mechanical processing of the processing probe 8 (FIG. 4B). At this time, the depth of the hole 9 is measured while making the bottom surface of the hole 9 further dug parallel to the surface of the glass substrate 2. Next, the mask is taken out from the AFM photomask defect correcting apparatus and introduced into the electron beam photomask defect correcting apparatus. The deep hole 9 is moved to the electron beam irradiation position, the region including the deep hole 9 is observed, and the two-dimensional shape information is stored. The region 9 to be filled with a transparent film is determined from the two-dimensional shape information of the stored processing region and the relative position information from the drift marker of the processing region, and the hole 9 in which the glass of the over-etched portion is deeply dug The depth of the measured hole 9 is filled with a transparent film 6 of electron beam CVD (FIG. 4C). When the unevenness of the buried transparent film becomes a problem, one of the two kinds of surface flattening methods is applied.

It is a schematic sectional drawing in the case of filling an overetched part with a transparent film deposit of an electron beam that best represents the characteristics of the present invention. FIG. 5 is a schematic cross-sectional view when an electron beam transparent film is attached so as to be flattened by measuring the overetch shape with AFM. FIG. 6 is a schematic cross-sectional view in the case where the protruding portion of the raised transparent deposition film is flattened by scraping with an AFM scratch. It is a schematic sectional drawing at the time of applying this invention to the overetching part of focused ion beam black defect correction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pattern 2 Glass substrate 3 Overetch part 4 Electron beam 5 TEOS or siloxy acid system molecule supply system 6 Transparent deposit film 7 Observation probe 8 Processing probe 9 Hole further cut by AFM

Claims (5)

  The black defect of the chrome mask is corrected by etching using a charged particle beam, and the overetched portion of the glass substrate of the chrome mask formed at the time of the correction is filled with a transparent film of electron beam deposition. And chrome mask black defect correction method.   2. The over-etched portion is further shaved with a probe of an atomic force microscope when the charged particle beam is a focused ion beam, and then filled with a transparent film of electron beam deposition. Chrome mask black defect correction method.   3. The chrome mask black according to claim 2, wherein when the overetched portion is shaved with a probe of an atomic force microscope, the bottom surface of the bored hole is parallel to the surface of the glass substrate. Defect correction method.   The step of obtaining the depth distribution of the over-etched portion of the glass with an atomic force microscope, and the step of controlling the thickness of the transparent film to be buried according to the depth distribution so that the buried transparent film surface becomes flat. The chrome mask black defect correcting method according to any one of claims 1 to 3, further comprising:   The step of filling the transparent film filling the overetched portion of the glass so as to be higher than the surface of the glass substrate, and the transparent film obtained by scraping and filling the portion higher than the glass surface using a probe of an atomic force microscope The method for correcting a black defect in a chrome mask according to any one of claims 1 to 3, further comprising a step of making the surface flat at the same height as the surface of the glass substrate.

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