JP2003133206A - Method of correcting white defect of mask for euv lithography - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a white defect correction which is also applicable to a EUVL mask that has not a buffer layer without causing great damage thereto and achieves high throughput. SOLUTION: A defect correction apparatus has a focused electron beam and a focused ion beam, wherein a white defect is recognized by the focused electron beam 2, and then an absorber film 25 is deposited on the outer edge of the defect by an electron beam CVD with a thickness enough not to be effected by a tail component of a focused ion beam of a subsequent stage while making absorber source gas such as W(CO)6 or the like flow into the recognized white defect region from a gas gun 10. Next, a absorber film 26 is deposited at a high speed on a cavity of the absorber formed by the electron beam CVD by FIB-CVD of the focused ion beam 12 while making the absorber source gas such as W(CO)6 or the like from the gas gun 10. Thus, white defect correction is performed without causing damage to the buffer layer 28 as a substrate (Mo/Si multilayer film 29 in the case of EUVL mask having no buffer layer).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of correcting white defects in a reflective mask for EUV lithography.

[0002]

2. Description of the Related Art At present, an optical projection exposure apparatus using a KrF or ArF excimer laser is used to transfer a pattern onto a wafer. Up to the 0.10 μm rule can be handled with an optical projection exposure system, but since the 0.07 μm rule and beyond reach the resolution limit, electron beam projection lithography (EB) other than direct writing and cell projection of the electron beam lithography system (EB) Electronb
eam Projection Lithography (EPL) and Low Energy Electron beam Projec
There are proposed new transfer methods such as ionization projection lithography (LEEPL), ion beam projection lithography (IPL), and soft X-ray reduction exposure (Extreme Ultra Violet Lithography, EUVL). EUVL is about wavelength
A technology that reduces the exposure of 13-nm soft X-rays with a reflective optical system.
It is regarded as the limit of shortening the wavelength of UV exposure, and has recently attracted particular attention as a lithographic technique that can be used for more than two generations.

In EUVL, an absorber pattern such as TaN or TiN formed on a reflection mask made of a Mo / Si multilayer film or Mo / S
An i multilayer film that is etched according to a pattern is used. EUVL masks are similar to photomasks
If there is a defect in the original mask, the defect will be transferred to the wafer and cause the yield to be reduced.Therefore, if there is a defect, the defect correction device must perform a defect correction process before transferring to the wafer. I won't.

Regarding the defect repair of the EUVL mask of the type having an absorber, a repair method using an ion beam has been reported (J. Vac. Sci. Technol. B18 3216 (2000)). In this report, a buffer layer such as Ru or SiO ₂ is provided between the absorber and the Mo / Si multilayer in order to reduce ion beam damage to the EUV mask. The black defect is corrected by removing the absorber by gas-assisted etching with Cl ₂ or Br ₂ and then removing the buffer layer by etching. White defect is W on the buffer layer
It has been corrected by forming the absorber film by FIB-CVD of (CO) ₆ .

In the above report, an ion beam with a high acceleration voltage is used for both the white defect repair and the black defect repair, and the ion beam is inevitably damaged during the defect recognition and the defect repair. It was necessary. In addition to increasing the mask generation process, the buffer layer had to be removed by selective etching after defect correction. If dry etching is used for selective etching of the buffer layer, Mo / S during selective etching
i It is necessary to consider damage to the multilayer film. Defect recognition and W
Although an absorber film can be formed by electron beam CVD of (CO) _6.
(For example, J. Vac. Sci. Technol. B11 2219 (1993)), the film forming rate is lower than that of FIB-CVD, and high throughput modification cannot be performed.

[0006]

SUMMARY OF THE INVENTION The present invention is intended to enable low-defect and high-throughput white defect correction applicable to an EUVL mask without a buffer layer.

[0007]

A defect repairing apparatus having a focused electron beam and a focused ion beam is used to recognize a white defect by the focused electron beam, and then W (CO) ₆ is added to the recognized white defect region.
In the electron beam CVD while flowing the absorber raw material gas such as, a thick absorber film is deposited on the outer edge of the defect so that the influence of the tail component of the focused ion beam in the next step is not affected, and at the same time, the ion beam An absorber film is deposited to a thickness that does not damage the implant (Fig. 1 (a)). Then electron beam CV
White defects are corrected by rapidly depositing an absorber film by FIB-CVD with a focused ion beam while flowing an absorber source gas such as W (CO) _{6 in} the cavity of the absorber made of D ( Figure 1
(b)).

[0008]

[Function] Since the recognition of defects and the formation of the thick absorber film at the outer edge of the defect and the thin absorber film inside thereof are performed by the electron beam,
There is almost no damage to the EUVL mask. FI to recess
In the B-CVD film deposition, the tail component of the ion beam has a thick absorber film at the outer edge portion, so that the EUVL mask is hardly damaged. If the thickness of the inner absorber film deposited by the electron beam is made thicker than the implantation depth of the ion beam considering the implantation distribution, the EUVL mask is hardly damaged by the implantation of the ion beam. Therefore, the buffer layer layer can be thinned, and there is a possibility that it can be applied to an EUVL mask where the buffer layer layer is not provided. When correcting a large white defect, since a high-volume recessed portion can be formed by high-speed FIB-CVD film formation, the throughput can be improved as compared with the case where all are formed by electron beam CVD.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention using an ion beam defect repairing apparatus will be described below.

An EUVL mask containing white defects is introduced into a vacuum chamber of a defect repairing apparatus having a focused electron beam and a focused ion beam as shown in FIG. 2, and a white EUVL mask 7 mounted on a highly accurate stage 6 is white. The defect is focused on the electron beam 2 emitted from the field emission electron source 1 and accelerated to 20 to 30 kV by the electromagnetic condenser lens 3 and the objective lens 4, and the EUVL mask 7 is scanned by the electromagnetic deflector 4. The secondary electron detector 8 synchronously takes in the secondary electrons 9 and displays an image corresponding to the secondary electron intensity. From this image, the white defect area 21 as shown in FIG. 3 is recognized. At the same time, the mark 20 is generated by electron beam CVD while flowing the absorber raw material gas such as W (CO) ₆ from the gas gun 10 onto the absorber. The recognized white defect area is used in the next step. Considering the tail component of the ion beam, Fig. 4
It is divided into an outer edge portion 22 and an inner portion 23 thereof as shown in FIG. Gas gun
The electron beam 2 is selectively and repeatedly scanned while flowing the absorber raw material gas such as W (CO) ₆ from 10 to the outer edge portion by electron beam CVD.
The absorber 22 is deposited with a sufficient thickness as an absorber, and the absorber 23 with a thickness equal to or greater than the implantation depth of the ion beam in consideration of the implantation distribution is deposited on the inside 23 (FIG. 1 (a)). Regarding the film thickness of the absorber, a calibration curve for the number of electron beam scans and the film thickness of the absorber generated by electron beam CVD is obtained in advance, and the required film thickness is achieved by controlling the number of electron beam scans. After the completion of the electron beam CVD absorber film formation, the relative positions of the white defect region and this mark are stored and used for alignment during correction with an ion beam.

Next, the stage 6 is moved to a position where the ion beam can be vertically incident, and is emitted from the liquid metal ion source 11 20
The ion beam 14 accelerated to ~ 30 kV is focused by the electrostatic condenser lens 12 and the objective lens 13 and scanned by the electrostatic deflector 15 while the secondary electron 9 is synchronized by the secondary electron detector 8. Display the captured secondary electron image. The mark 20 generated and recognized by the electron beam is detected from this secondary electron image, and the mark 20 is aligned with the defect recognition area 21 obtained by the electron beam. Next, the focused ion beam 14 is selectively repeated only in the recessed region 24 as shown in FIG. 1 (a) while flowing the absorber raw material gas such as W (CO) ₆ from the gas gun 10. The absorber film 26 is scanned at a higher speed than the scanning of the beam and the absorber film 26 is deposited at a higher speed to correct the white defect (FIG. 1 (b)). At this time, since the tail part of the ion beam has an absorber of the white defect outer edge part generated by electron beam CVD, it damages the underlying buffer layer 28 (Mo / Si multilayer film 29 in the EUVL mask without the buffer layer). Absent. Similarly, since an absorber having a film thickness equal to or larger than the ion beam implantation depth is formed inside the white defect, the underlying buffer layer 28 or the Mo / Si multilayer film 29 is not damaged. As in the case of electron beam film formation, the film thickness of the absorber is adjusted in advance by the number of ion beam scans and FIB-
A calibration curve of the film thickness of the absorber produced by CVD is obtained in advance, and the required film thickness is achieved by controlling the number of ion beam scans.

[0012]

As described above, according to the present invention, by combining the low damage defect recognition by the electron beam and the absorber film formation with the high-speed film formation by FIB-CVD, the EUVL without the buffer layer can be obtained. High-throughput white defect correction with low damage that can be applied to masks can be performed.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view best showing the features of the present invention.

FIG. 2 is a conceptual diagram illustrating an example of the present invention.

FIG. 3 is a diagram for explaining a processing procedure of an example.

FIG. 4 is a diagram for explaining a processing method according to an embodiment.

[Explanation of symbols]

1 Field emission electron source 2 electron beam 3 Electromagnetic condenser lens 4 Electromagnetic objective lens 5 Electromagnetic deflector 6 stages 7 EUVL mask 8 Secondary electron detector 9 Secondary electron 10 Gas gun for supplying absorber raw material gas 11 Liquid metal ion source 12 ion beam 13 Electrostatic condenser lens 14 Electrostatic objective lens 15 Electrostatic deflector 20 Alignment mark 21 White defect area 22 Outer edge of white defect 23 Inside of white defect 24 Indentation of correction film 25 Electron beam CVD film 26 FIB-CVD film 27 absorber pattern 28 buffer layer 29 Mo / Si multilayer

Claims (2)

[Claims] 1. A defect repairing apparatus having a focused electron beam and a focused ion beam, wherein an absorber film having a sufficient thickness is provided at an outer edge portion of the defect so that the focused electron beam does not damage the focused ion beam in the next step. A method of repairing a white defect in a mask for EUV lithography, which comprises repairing by depositing a thin absorber film on the inside and then rapidly depositing the absorber film with a focused ion beam. 2. A method of repairing a white defect of a mask for EUV lithography by using a focused electron beam and a focused ion beam while flowing an absorber source gas, wherein the focused electron beam is scanned to detect defects. An absorber film having a sufficient thickness as an absorber at the outer edge and a thinner film inside the absorber film,
In addition, by depositing an absorber film having a sufficient thickness so that the focused ion beam does not damage the mask, and thereafter, scanning the focused ion beam at a higher speed than scanning of the focused electron beam, A white defect repairing method for a mask for EUV lithography, which comprises repairing a white defect by depositing an absorber film on a portion.