JP2004012806A - Method for eliminating defect in levenson type phase shifting mask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately eliminate a defect in a Levenson type phase shifting mask having an undercut structure in such a way as not to cause lowering of light intensity. <P>SOLUTION: When a black or white defect is eliminated, a Cr pattern 1 on the defect is removed with focused ion beams 4, a quartz or glass substrate 3 including undercut width is shaved with the beams while feeding assist gas which does not lower transmittance from a gas gun 5, and then the undercut structure or a similar structure is accurately reproduced with a shielding film 8 formed by CVD using electron or ion beams 6 while feeding source gas for the shielding film from a gas gun 7, whereby the defect is accurately eliminated while maintaining light intensity even in the defect eliminated region. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a defect correction method for a Levenson mask type phase shift mask in which a part of a glass of a binary mask is dug.
[0002]
[Prior art]
With further miniaturization of Si semiconductor integrated circuits in recent years, it is required that patterns on a reticle also correspond to miniaturization. Reduction projection exposure apparatuses have responded to this demand by increasing the NA and shortening the wavelength. At the present time when it is required to advance the miniaturization, a phase shift mask, which is a kind of super-resolution technology, has been used to improve the resolution and the depth of focus without changing the size of the reduction projection exposure apparatus. There are two types of phase shift masks, the Levenson type and the halftone type, and it is known that the Levenson type has a greater effect of improving the resolution. However, it is difficult to optimize the arrangement of the phase shifter in the Levenson type, so there is little effect of improving the resolution.However, the halftone type, in which the shielding film is replaced with a halftone film, has fewer changes from the binary mask technology and is easier to introduce. , Is becoming widely used. However, even if the problems of the above design technique are overcome to further improve the resolution, the number of cases of producing a mask using a Levenson type having a large effect of improving the resolution is increasing. There are Levenson-type phase shift masks in which a transparent phase shifter film is disposed and those in which a glass or quartz substrate is dug to a depth where the phase is inverted. Currently, the type that is mainly put into practical use is a type in which a glass or quartz substrate is dug, and only a portion where a fine pattern is required with a binary mask is dug into a glass or quartz substrate to the depth where the phase is inverted. This is a Levenson type phase mask.
[0003]
In recent glass digging Levenson masks, a structure (single digging type) in which an undercut is added below the Cr pattern 1 on the phase shifter side as shown in FIG. It is becoming. The glass or quartz substrate 3 is not limited to the single engraving type, but also employs a double engraving type in which the non-phase shifter has an undercut structure on the non-phase shifter side as shown in FIG. It is becoming possible.
[0004]
As a method of shaving glass with a focused ion beam apparatus using a liquid metal Ga ion source which is typically used for defect correction of a binary mask, xenon fluoride (XeF ₂ ) (SPIE 3873, p127 (1999)) or iodine There is known a method in which an ion beam is irradiated in a gas (SPIE 4409, p563 (2001)) atmosphere to suppress the injection of Ga and etch a glass or quartz substrate while maintaining a high transmittance. If the conventional method of repairing a glass digging Levenson mask is directly applied to a Levenson mask having a structure in which a single digging type or a double digging type undercut is added, the light amount of a defect correction portion is reduced. There is also a demand for a Levenson mask having a structure in which an undercut of a single digging type or a double digging type is added so that high-accuracy and high-quality defect correction can be performed without a decrease in light amount.
[0005]
[Problems to be solved by the invention]
The defect correction of the Levenson type phase shift mask having the undercut structure is performed so that the light quantity does not decrease.
[0006]
[Means for Solving the Problems]
For the black defect region, after recognizing the black defect region, the Cr pattern on the defect is removed, and the black defect region is continuously removed including the undercut width so that the transmittance does not decrease due to the implantation of Ga. Removal is performed with a focused ion beam while flowing iodine or xenon fluoride. A black film is corrected by growing a shielding film on the Cr film receded by the undercut width by electron beam CVD so as to reproduce the undercut structure.
[0007]
After recognizing the white defect area with respect to the white defect area, the Cr pattern on the defect is removed, and the transmittance of the white defect area is further reduced by Ga implantation to a depth corresponding to a phase of 180 degrees. While removing iodine or xenon fluoride so as not to cause the removal, the focused ion beam including the undercut width is removed. For the Cr pattern receded by the undercut width, a shielding film is grown by electron beam CVD so as to reproduce the undercut structure, thereby correcting a white defect.
[0008]
Also, instead of growing a shielding film by electron beam CVD to reproduce the undercut structure for the Cr pattern recessed by the undercut width, a shielding film is formed on the Cr film recessed by the undercut width by FIB-CVD. Defects can also be corrected by forming an eaves and reproducing a structure equivalent to an undercut.
[0009]
[Action]
For both black defect and white defect repair, the focused ion beam is used to cut the glass substrate including the undercut width, and the shielding film formed by electron beam CVD or FIB-CVD has the same undercut structure as the normal portion or equivalent Since a simple structure can be reproduced, it is possible to perform defect correction with high accuracy while maintaining the amount of light in the defect correction region.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
An undercut glass digging Levenson type having a defect in a focused ion beam-electron beam combined device having an ion optical system 11 perpendicular to a mask plane as shown in FIG. 4 and having an electron optical system 12 in an oblique direction. The phase shift mask 13 is introduced, and is moved by the XY stage 14 having a rotation mechanism to a position where a defect is detected by the defect inspection apparatus. In order to recognize the defect region, the ion optical system 11 scans the region including the defect with the ion beam 4 accelerated to 20￣30 kV and focused to about 0.1 μm, and detects the secondary ion detector or the secondary electron. The secondary ions or secondary electrons generated by the irradiation of the ion beam 4 are taken in by the vessel 15. The signal intensity of the secondary ion detector or the secondary electron detector 15 is made to correspond to the color or gradation of one pixel on the CRT, and is displayed in synchronization with the scanning of the deflection electrode of the ion optical system 11, thereby displaying the secondary ions. An image or a secondary electron image is formed. A defect region is determined from the secondary ion image or the secondary electron image. Simultaneously with the irradiation of the ion beam 4, the electron beam 6 of several hundred volts adjusted to an appropriate beam diameter by the electron optical system 12 in order to prevent charge-up of the glass-digging Levenson type phase shift mask 13 as an insulator is irradiated. To neutralize the charge.
[0011]
As shown in FIG. 1, for a black defect, after recognizing a black defect region 2 (FIG. 1A), a Cr pattern 1 on the defect is removed by a focused ion beam 4 (FIG. 1B). )) Concentrated ion beam while flowing iodine or xenon fluoride 5 from a gas gun 5 so that the transmittance of the quartz or glass substrate 3 is not reduced by the implantation of Ga including the undercut width in the black defect region. In step 4, the quartz or glass substrate 3 is shaved to remove defects (FIG. 1 (c)). During the Cr pattern or quartz or glass substrate removal processing, the electron beam 6 of several hundred volts adjusted to an appropriate beam diameter by the electron optical system 12 is irradiated to prevent charge-up, thereby neutralizing charges. The XY stage 14 having a rotating mechanism is rotated so that the Cr pattern 1 retreated by an undercut width faces the electron optical system mounted obliquely with respect to the mask. The focused electron beam 6 is scanned to obtain a secondary electron image of a region including the Cr pattern 1 receded by the undercut width, and a region requiring electron beam CVD is determined. The shielding film 8 is horizontally oriented so that the undercut structure can be accurately reproduced with the focused obliquely incident electron beam 6 of the high probe current while flowing the shielding film source gas from the gas gun 7 to the region where electron beam CVD is required. The black defect is corrected by growth (FIG. 1D). In order to prevent charge-up during secondary electron image acquisition and electron beam CVD, the electron beam 6 is used at a low acceleration voltage of about 600V￣1000V.
[0012]
As shown in FIG. 2, for the white defect, after recognizing the white defect region 9 (FIG. 2A), the Cr pattern 1 on the defect is removed by the focused ion beam 4 (FIG. 2B). )) Then, as in the case of correcting the black defect, the white defect region is further cut to a depth corresponding to a phase of 180 degrees while flowing iodine or xenon fluoride from the gas gun 5 so that the transmittance does not decrease due to the implantation of Ga. The focused ion beam 4 including the width is used to cut the quartz or glass substrate 3 to remove defects (FIG. 2C). At this time, during the removal processing of the Cr film, quartz or glass substrate, the electron beam 6 of several hundred volts adjusted to an appropriate beam diameter by the electron optical system 12 is applied to prevent charge-up, thereby neutralizing the charge. The XY stage 14 having a rotation mechanism is rotated so that the Cr pattern 1 receded by the undercut width faces the electron optical system obliquely attached to the mask as in the case of the black defect correction. The focused electron beam 6 is scanned to obtain a secondary electron image of a region including the Cr pattern 1 receded by the undercut width, and a region requiring electron beam CVD is determined. The undercut structure of the shielding film 8 can be accurately reproduced by selectively scanning the focused obliquely incident electron beam 6 with a high probe current while flowing the shielding film source gas from the gas gun 7 to the region where electron beam CVD is required. The white defect is corrected by growing in the horizontal direction (FIG. 2D). At the time of secondary electron image acquisition and electron beam CVD, the electron beam 6 is used at a low acceleration voltage of about 600V６００1000V in order to prevent charge-up.
[0013]
For both black defect correction and white defect correction, the shielding film 8 is shielded from the gas gun 7 by the electron beam 6 instead of growing the shielding film 8 in the horizontal direction so as to reproduce the undercut structure with respect to the Cr pattern 1 receded by the undercut width. While flowing the film raw material gas, the focused ion beam apparatus is focused on the Cr pattern 1 receded by the undercut width with the ion beam 4 focused by the ion optical system 12 vertically arranged on the quartz or glass substrate 3, as shown in FIG. The eaves (for example, J. Vac. Sci. Technol. B18, p3254 (2000)) of the shielding film 8 are formed when correcting a white defect of such a stencil mask, and a structure equivalent to the undercut structure is precisely formed. Defects can be corrected by reproducing well. Of course, while the shielding film 8 is being formed by the ion beam 4, the electron beam is irradiated with the electron beam 6 of several hundred volts adjusted to an appropriate beam diameter by the electron optical system 12 in order to prevent charge-up, thereby neutralizing the charge.
[0014]
For both the black defect correction and the white defect correction of the Levenson type phase shift mask having the undercut structure, the quartz or glass substrate 13 including the undercut width is cut while maintaining the high transmittance with the focused ion beam 4. Since the same undercut structure as a normal portion or a similar structure can be accurately reproduced by the shielding film 8 formed by the electron beam CVD or FIB-CVD, the defect correction area can perform high-precision defect correction while maintaining the magnitude of the light amount. It is possible.
[0015]
【The invention's effect】
As described above, according to the present invention, both the black defect and the white defect of the Levenson-type phase shift mask having the undercut structure in which the binary mask glass is dug, and the glass substrate including the undercut width by the focused ion beam By accurately reproducing the undercut structure or equivalent structure with the shaving film and the shielding film formed by electron beam CVD or FIB-CVD, the defect correction area realizes high-precision defect correction while maintaining the amount of light. it can.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a defect repair process (black defect repair) that best illustrates the features of the present invention.
FIG. 2 is a schematic sectional view illustrating a case where a white defect is corrected in the present invention.
FIG. 3 is a schematic sectional view illustrating a case where an eave is formed by FIB-CVD instead of forming an undercut structure by electron beam CVD.
FIG. 4 is a schematic diagram of a focused ion beam-electron beam combined processing apparatus used when correcting a defect of a Levenson mask having an undercut structure using the present invention.
FIG. 5 is a view for explaining a one-side engraving type Levenson mask and a two-side engraving type Levenson mask.
[Explanation of symbols]
Reference Signs List 1 Cr pattern 2 Black defect region 3 Quartz or glass substrate 4 Ion beam 5 Assist gas gas gun 6 for maintaining transmittance 6 Electron beam 7 Shielding film material gas gas gun 8 Shielding film 9 White defect region 10 Phase 180 A region in which a glass substrate is dug for inversion 11 An ion optical system 12 An electron optical system 13 A Levenson-type phase shift mask having an undercut structure 14 XY stage with a rotating mechanism 15 Secondary ion detector or secondary electron detection vessel

Claims (4)

A defect correction method for a Levenson-type phase shift mask, comprising growing a shielding film by electron beam CVD on a Cr pattern receded by an undercut width so as to reproduce an undercut structure, thereby correcting a black defect. With respect to the white defect region of the Levenson mask having the undercut structure, the white defect region is further removed by a focused ion beam including the undercut width to a depth corresponding to a phase of 180 degrees, and the Cr receded by the undercut width. A defect correction method for a Levenson-type phase shift mask, which comprises growing a shielding film on a pattern by electron beam CVD so as to reproduce an undercut structure and correcting a white defect. For the black defect region of the Levenson mask having an undercut structure, first, the black defect region including the undercut width is removed by a focused ion beam, and then a shielding film is formed on the Cr pattern receded by the undercut width by FIB-CVD. A defect correction method for a Levenson-type phase shift mask, wherein a black defect is corrected by forming an eaves with the same and reproducing a structure equivalent to an undercut. With respect to the white defect area of the Levenson mask having the undercut structure, the white defect area is further removed by a focused ion beam including the undercut width to a depth corresponding to a phase of 180 degrees, and then undercut by FIB-CVD. A defect correction method for a Levenson-type phase shift mask, comprising forming an eave with a shielding film on a Cr pattern receded by a width, and correcting a white defect by reproducing a structure equivalent to an undercut.

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