JP2008185931A - Method for correcting defect in photomask using focused ion beam microfabrication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems caused by charge-up at the correction of the defects of an isolated pattern, in a photomask that uses a focused ion beam microfabrication device. <P>SOLUTION: After an aerial wiring 7 of a metal deposited film is by focused ion beam (FIB) CVD formed between isolated patterns and electrically conducted to eliminate the influences due to charge-up, a defect 3 is corrected. The aerial wiring 7 of the metal deposited film which becomes unnecessary after correction is removed by ion beam etching. After an aerial wiring of a metal deposited film is formed by FIB-CVD in an X direction and a Y direction on an isolated pattern to eliminate the influences due to charge-up, the aerial wiring of the metal deposited film in the X and Y directions is used as a marker for correcting the drift during fabrication, and a defect is corrected, while the drift is corrected. The aerial wiring of the metal deposited film, which becomes unnecessary after correction, is removed by ion beam etching or AFM (atomic force microscope) scratch processing. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an isolated pattern of a photomask using a focused ion beam microfabrication apparatus (an isolated pattern is one in which a chromium or MoSi conductive pattern having a small area exists in a floating island state on a glass substrate independently of other patterns) This is related to the defect correction method.

  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 conventionally performed using a laser or focused ion beam (FIB). The fine pattern defect at the tip cannot be corrected, and the imaging damage (decrease in transmittance) of the glass part due to the implantation of gallium used as the primary beam in the focused ion beam due to the shortening of the wavelength of the light source of the reduction projection exposure apparatus There has been a problem, and there is a need for a defect correction technique that can correct defects in fine patterns and that does not cause imaging damage. Recently, there has been proposed a method for recovering transmittance by removing a thin gallium injection layer by cleaning using a low acceleration voltage even with a focused ion beam (Non-patent Document 1). Also, mechanical microfabrication using photomask defect repair device (non-patent document 2) and atomic force microscope (AFM) technology using an electron beam that does not use an ion beam (in principle, there is no implantation in gallium) A photomask black defect correcting device by (scratch processing) has also been developed (Non-patent Document 3).

  However, since the photomask is a metal film deposited on the glass to block light, when the area of the metal film pattern is small, charge-up occurs due to excessive charge by ion beam irradiation. 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. Conventionally, a fine hole has been created with an ion beam and used as a drift marker. However, it is becoming difficult to make the pattern finer and shorten the exposure wavelength. If there is a vertical and horizontal pattern in the machining window, drift correction can be performed using the edge of the pattern as a drift marker, but there are many cases where there is no appropriate vertical and horizontal pattern in the machining window, so it can be used universally. A drift marker is desired.

In addition, it has been shown that an arbitrary three-dimensional nanostructure can be formed with a FIB-CVD film by converting the focused ion beam into an appropriate scan using 3D CAD data. Recently, Matsui et al. Reported an aerial wiring fabricated by FIB-CVD using the above technique (Non-patent Document 4).
Y. Itou, et al. Proc. Of SPIE 5992 59924Y-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) T. Robinson, A. Dinsdale, R. Bozak, R. White, DA Lee, and K. Roessler, Proc. Of SPIE 5992 59924Z-1-59924Z-13 (2005) Shinji Matsui, Applied Physics 73 445-454 (2004) JP2002-139827 ([0005], FIG. 1)

  The present invention relates to a photomask defect correction method using a focused ion beam microfabrication apparatus, and when the area of a metal film pattern is small, image quality deterioration or drift of secondary electron images due to charge-up by ion beam irradiation. The purpose is to prevent a decrease in machining accuracy due to the occurrence of the above.

  FIB-CVD metal deposition film connects isolated and non-isolated patterns with aerial wiring, then recognizes black or white defects and removes defects (in the case of black defects) or deposits light shielding film (white defects) ) And correct it. Aerial wiring is designed by 3D CAD, and it is realized by converting 3D CAD data into appropriate ion beam scanning. The aerial wiring can be realized by a known technique (for example, Patent Document 1). Metal deposition film aerial wiring that is no longer needed after correction is removed by ion beam etching or AFM scratch processing.

  Defects are corrected by forming aerial wiring with FIB-CVD metal deposition film in the X and Y directions in the isolated pattern, and using metal deposition film conductors in the X and Y directions as drift correction markers during processing To do. Metal deposition film aerial wiring that is no longer needed after correction is removed by ion beam etching or AFM scratch processing.

  If an isolated pattern is connected to another pattern with a conductive wire, charge-up due to excessive charge accumulation can be avoided, so that an image with good image quality can be obtained and the defect shape can be recognized accurately. Since there is no drift due to charging, highly accurate machining can be performed.

  Since the drift marker is created by an ion beam, the present invention can be applied even when there are no appropriate vertical and horizontal patterns for drift correction in the processing window. Since the charge-up can be avoided by the aerial wiring, the same effect as above can be expected. Since an image with good image quality can be obtained, it is possible to detect the drift amount with high accuracy. Therefore, it is possible to suppress a decrease in processing accuracy due to thermal drift by drift correction.

  Since it is an aerial wiring, even if it is removed after correction, the underlying glass substrate will not be damaged like a conventional deposition film. Since the glass substrate is not damaged, the transfer characteristic of the photomask at the glass portion is not deteriorated. Even if the portion formed on the pattern is slightly damaged after removal, the transfer characteristics are not greatly affected.

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

  First, a photomask having defects is placed on an XY stage of a focused ion beam microfabrication apparatus having a light shielding film source gas introduction system, a metal deposition film source gas introduction system, and a gas introduction system for gas assist etching, The XY stage is moved so that the defect position found by the optical defect inspection apparatus is at the center of the visual field.

  FIG. 1 is a schematic cross-sectional view illustrating a case where a black defect of an isolated pattern is corrected by the present invention after the photomask is installed, and FIG. 2 is a case of correcting a white defect of an isolated pattern by the present invention. It is a schematic sectional drawing explaining these.

  When a region including the photomask defect is observed with a focused ion beam microfabrication apparatus, an isolated defect or an isolated pattern 4 having a defect 3 is affected by charge-up, and a clear SIM image cannot be obtained. In some cases, a metal depletion such as hexacarbonyltungsten is introduced from the gas introduction system 2 in order to establish conduction by creating a wiring 7 (hereinafter referred to as an aerial wiring 7) that connects the normal pattern 5 and the isolated pattern 4 that are not isolated. While flowing the position film source gas, the ion beam 1 is selectively irradiated to the portion where the wiring 7 to be connected in the air is to be formed (FIGS. 1 (a) and 2 (a)).

 The aerial wiring 7 is designed by 3D CAD, and is realized by converting 3D CAD data into appropriate ion beam scanning in the deposition film source gas atmosphere. In other words, the amount of film material (gas pressure and supply time) supplied to the ion beam irradiation position, the residence time of the ion beam, the amount of beam current and the drawing interval are set so that the finished shape becomes the target size. Control and scan. Specifically, the height direction is sliced from the surface model created by 3D-CAD, and each slice is converted into an ion beam vector scan. 3D structures are constructed by stacking vector scans on each side in order from the bottom slice plane. At this time, a rule that balances the ion beam scanning speed and the lateral growth rate is applied so that the portion that becomes the aerial wiring 7 can be actually grown in the lateral direction (see, for example, Non-Patent Document 4). By changing the metal deposition film source gas, the aerial wiring 7 can be made not only of tungsten but also of platinum.

 After creating the aerial wiring 7, irradiate the focused ion beam 1 in the state without charge-up and retake the image again, and recognize the defect area 3 to be corrected by comparing it with a normal pattern without defects by pattern matching etc. 1 (b) and FIG. 2 (b)).

 In the case of a black defect, the ion defect 1 is selectively irradiated to the black defect region 3 while flowing a gas for gas-assisted etching such as iodine or xenon fluoride from the assist etching gas introduction system 8, and the black defect is removed by removing the surplus portion. Make corrections (Figure 1 (c)).

 In the case of a white defect, the ion beam 1 is selectively irradiated to the white defect region 10 while flowing a light shielding film material gas such as naphthalene or phenanthrene from the light shielding film material gas introduction system 9 to form the light shielding film 11 to correct the white defect. (Figure 2 (c)).

 After the defect correction, the metal deposition film aerial wiring 7 made for the unnecessary conduction is removed by physical sputtering with the ion beam 1 (FIGS. 1 (d) and 2 (d)). Alternatively, the metal deposition film aerial wiring 7 is selectively irradiated with the ion beam 1 while flowing a gas assist etching gas such as iodine or xenon fluoride and removed.

  When there is no appropriate vertical and horizontal pattern for drift correction in the processing window, the FIB-CVD metal deposition film aerial wiring 7 deposited for conduction is used as a drift correction marker. Metal deposition film aerial wiring 7 is deposited by FIB-CVD in X direction and Y direction on isolated pattern 4 including isolated defect or defect 3 (Fig. 3 (b)), and metal deposition film in X direction and Y direction The white defect or black defect 3 is corrected by the same method as described above by using pattern matching or the like for the aerial wiring 7 as a marker for drift correction at the time of processing (FIG. 3 (c)). Note that FIG. 3C shows a case of black defect correction, and is not displayed in the case of white defect correction.

 After the correction, the metal deposition film aerial wiring 7 used as a drift correction marker that is no longer necessary is removed by physical sputtering using the ion beam 1 (FIGS. 1 (d) and 2 (d)). Alternatively, the metal deposition film aerial wiring 7 is selectively irradiated with the ion beam 1 while flowing a gas assist etching gas such as iodine or xenon fluoride and removed.

  FIG. 4 is a schematic cross-sectional view showing a method of removing the unnecessary metal deposition film aerial wiring by AFM scratch processing.

  As shown in Fig. 4 (a) to Fig. 4 (c), the normal pattern and the isolated pattern in the FIB-CVD metal deposition film are aerialized in the same way as in Fig. 1 (a) to Fig. 1 (c). After correcting the black defect by making the wiring 7 connected by, or as shown in Fig. 2 (a) to Fig. 2 (c), normal pattern and isolated pattern in the FIB-CVD metal deposition film in the air After making the wiring 7 to be connected and correcting the white defect, the aerial wiring 7 that has become unnecessary may be removed by scratching with the AFM machining probe 12 that is harder than the wiring material (FIG. 4 (d)). FIG. 4 (d) shows a case where black defects are corrected, and is not displayed when white defects are corrected. Machining waste generated by AFM scratch processing is removed by wet cleaning or cleaning with a dry ice cleaner.

It is a schematic sectional drawing explaining the case where the black defect of an isolated pattern is corrected by this invention. It is a schematic sectional drawing explaining the case where the white defect of an isolated pattern is corrected by this invention. It is a top view explaining the case where a metal deposition film aerial wiring is used as a drift marker. It is a schematic sectional drawing which removes the metal deposition film | membrane air wiring which became unnecessary by AFM scratch processing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ion beam 2 Metal film raw material gas introduction system 3 Black defect 4 Isolated defect or isolated pattern 5 Normal pattern 6 Glass substrate 7 Metal deposition film aerial wiring 8 Assist etching gas introduction system 9 Light shielding film raw material gas introduction system 10 White defect 11 Light shielding Membrane 12 AFM processing probe

Claims (3)

  Between the isolated pattern on the photomask and the non-isolated pattern, the FIB-CVD metal deposition film is used to connect the pattern with the aerial wiring, and then the black or white defect is corrected. A photomask defect correction method using a focused ion beam micromachining apparatus, wherein the metal deposition film aerial wiring is removed by ion beam etching.   The FIB-CVD metal deposition film aerial wiring deposited for the isolated pattern conduction is used as a drift correction marker, and the modified metal deposition film is removed by ion beam etching. A photomask defect correction method using a focused ion beam micromachining apparatus.   2. A photomask defect correcting method using a focused ion beam micromachining apparatus according to claim 1, wherein the metal deposition film after correction is removed by AFM scratch processing.

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