JP2003133203A - Method of correcting defect of stencil mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove a black defect on the side of a stencil mask and perform a black defect correction that prevents a white defect film from depositing from the side and a sag on the side thereof without slanting a stage. SOLUTION: The side of the stencil mask is selectively scanned by a grazing incidence ion beam or an electron beam 5 which is focused by a condenser lens 1 and deflected by a deflector 2a, which is above an objective lens 3, and forms a locking point 6 in the vicinity of the stencil mask by swinging back the objective lens 3. In the case of a black defect, the defect is removed by physical sputtering or gas assisted etching. In the case of a white defect, scattere containing carbon is formed on the mask for EPL by FIB-CVD or electron beam CVD from the side, and scattere containing platinum is formed on a mask for IPL, thus the defects being corrected. The above method is applied to a portion where the black defect is corrected by a vertical incidence ion beam (a portion that has a sag in a cross section), and the side is weighed according to the length and selectively scanned for the removal of the sag.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stencil mask defect correction method for electron beam projection lithography and ion beam projection 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. Optical projection exposure equipment can be used up to the 0.10 μm rule, but since the resolution limit is reached after the 0.07 μm rule, electron beam projection lithography (Electron beam Projection Lithography, EPL) and low energy are used in addition to EB direct writing. Electron Beam Projection Lithography (Low Energy Elec
tron beam Projection Lithography (LEEPL) and ion beam projection lithography (Ion beam Projection Lithography)
aphy, IPL) and soft X-ray reduction exposure (Extreme Ultra Violet Lit
New transfer methods such as hography, EUVL) have been proposed. Of these, EPL, LEEPL, and IPL are all photomasks (light-shielding film) used in optical projection exposure equipment.
A stencil mask with a thickness of 0.5 to 4 μm is used instead of (about 0.1 μm). In the stencil mask as well as in the photo mask, if there is a defect in the mask photo mask, the defect will be transferred to the wafer and cause the yield to be reduced. Defect repair processing must be performed.

Regarding the defect correction of the stencil mask,
Defect repair methods using ion beams have been reported for both IPL and EPL (EPL: J. Vac. Sci. Technol. B
18 3254 (2000), IPL: J. Vac. Sci. Technol. B17 3154
(1999)). Regarding the correction of white defects, FIB-C was constructed by bridging the defect parts of the stencil mask as shown in Fig. 2.
With VD, a carbon-containing film is grown for an EPL mask to form a scatterer that scatters electron beams, and for an IPL mask, a platinum-containing film is grown to form a scatterer that scatters an ion beam. It is fixed by doing. Regarding black defects,
This is done by selectively scanning and removing the defective portion by physical sputtering of the ion beam.

However, when there is a black defect on the side surface of the stencil mask as shown in FIG. 3 (a), a conventional vertically incident ion beam is accurate due to defocusing due to the thickness of the stencil mask and the beam divergence angle. It was not possible to remove various defects. Even when the pattern defect of the black defect was corrected, the sagging occurred in the processed cross section due to the beam divergence angle and the beam profile. This caused the defect correction accuracy to decrease. If you tilt the stage holding the mask,
Although it is possible to correctly recognize and correct the black defect and correct the cross-section sag at the black defect correction point as shown in (a), it is not possible to perform the positioning with high accuracy in the tiltable stage as in the plane biaxial stage. If there is a white defect as shown in Fig. 4 (a),
The defect could be repaired only by bridging the defect site. Although the white defect can be corrected by tilting the stage holding the mask, the tiltable stage cannot perform positioning with a higher degree of accuracy than the planar biaxial stage. In the cross-linking structure, since a film with a thickness of several μm is formed on a stencil mask with a thickness of several μm, there are various problems due to the difference in height when correcting defects with high accuracy and after checking with a defect inspection machine. Will occur. Although the white defect can be corrected without any step by tilting the stage holding the mask, the tiltable stage cannot perform the positioning with high accuracy as in the case of the biaxial planar plane. In addition, the source gas supply system and the secondary electron (secondary ion) detector cannot be placed near the mask at the same time in order to avoid interference when the stage is tilted. When the raw material gas supply system is moved away, the gas pressure must be increased in order to increase the gas supply amount, and when the secondary electron (secondary ion) detector is moved away, the S / N decreases and the image quality deteriorates. .

[0005]

SUMMARY OF THE INVENTION The present invention is intended to enable removal of black defects on the side surface of a stencil mask, growth of a white defect film from the side surface, and correction of a black defect on the side surface without sagging without tilting the stage. To do.

[0006]

[Means for Solving the Problems] A method using a beam locking method for observing the side surface of a deep hole or a protrusion with a scanning electron microscope has been reported (for example, Rev. Sci. Ins.
trum. 67 1458 (1996)). This method is applied to a scanning ion microscope having a two-stage deflection system between a condenser lens and an objective lens, and observation of the side wall of a stencil mask where the correction is determined and removal of black defects by physical sputtering and correction of raw material gas for white defects or White defects and black defects on the sidewall are corrected by scanning only the selected area while flowing the assist gas for black defect correction. When this method is applied to a scanning electron microscope having a two-stage deflection system between a condenser lens and an objective lens, the side wall of a stencil mask where the correction is determined is observed and the source gas for the white defect correction is made to flow while the selected area is selected. The white defect on the side wall is corrected by scanning only.

In order to realize the black defect correction without side sagging, the cross section of the stencil mask in which the black defect is corrected by the vertically incident ion beam is selectively weighted according to the depth by using the beam locking method. Then, the side surface is scanned with an ion beam to remove anyone. The sag on the cross section is removed by physical sputtering or gas-assisted etching while flowing an assist gas.

[0008]

[Function] In the beam locking method, the beam is scanned by only one stage of the two-stage deflection as shown in FIG. 1, and the focusing is performed by the condenser lens. The objective lens is used to set a deflection fulcrum (locking point) near the sample. In the beam locking method, the focused beam can be incident obliquely as shown in FIG. 1, so that the side surface of the stencil mask can be observed without inclining the sample by scanning and capturing signals. The black defect on the side surface can be removed by specifying the defective region and selectively scanning the defective region with the ion beam. If gas-assisted etching is performed using an assist gas according to the material, it is possible to process in a short time due to the speed-up effect. By selectively scanning only the defect region with the ion beam or the electron beam while flowing the raw material gas of the scatterer for correcting the white defect, the white defect film can be grown from the side surface. Since the stage is not tilted, highly accurate positioning can be performed, and the gas supply system and the detector can be arranged near the mask.

In the beam locking method, only the side surface can be selectively scanned. Therefore, the number of scans is weighted according to the depth of any cross section that occurs when a black defect is corrected by a vertically incident ion beam. By scanning the side surface, it is possible to remove any part by physical sputtering.
By using the assist gas according to the material, the etching can be accelerated by the chemical effect and the processing time can be shortened.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention using an ion beam defect repairing apparatus will be described below.
A stencil mask containing defects is introduced into the vacuum chamber of the ion beam defect repair device as shown in Fig. 5, and the defects on the stencil mask 4 mounted on the XY stage are emitted from the ion source 11 and accelerated to 20 to 30 kV. Ion beam 1
4 is focused by the electric field of the electrostatic condenser lens 12,
It is deflected by the deflector 2 on the upper side of the two-stage deflector, is swung back by the electric field of the electrostatic objective lens 13 and is incident on the side surface of the stencil mask 4, and the secondary ion detector or the secondary electron detector 15
Secondary ion or secondary electron generated from the side of the mask at 16
Are captured in synchronization with scanning to display a secondary ion image or a secondary electron image. From this image, a defect region on the side surface as shown in FIG. 3 (a) or 4 (a) is recognized. Scanning range is objective lens
It is determined by the combination of the setting of 13 beam locking points and the deflection amount of the upper deflector 2.

For the black defect area 9 as shown in FIG. 3 (a), only the defect area is selectively scanned with an ion beam.
As shown in (b), the black defect on the side surface is removed by physical sputtering. Of course, the gas gun 10 may be brought close to the stencil mask to flow an assist gas according to the material of the stencil mask to perform gas-assisted etching, and it is possible to process in a short time due to the speed-up effect. For the white defect region 8 as shown in FIG. 4 (a), in the case of a mask for EPL (LEEPL), the ion beam is selectively supplied only to the defect region while flowing a carbon-containing source gas (for example, phenanthrene). The carbon-containing film scatterer 7 as shown in FIG. 4 (b) is grown from the side by scanning. Raw material gas when the mask containing platinum for IPL (e.g. _{(CH 3) 3 (CH 3} C 5 H 4) Pt) or raw material gas containing tungsten (e.g. W (CO) ₆₎ is flowed while the ion beam Are selectively scanned only in the defect region to grow a scatterer 7 of a platinum- or tungsten-containing film as shown in FIG. 4 (b) from the side surface.

Next, an embodiment of the present invention using a scanning electron microscope capable of introducing a carbon-containing gas will be described. Similar to the ion beam defect repair device, a stencil mask containing defects is introduced into the vacuum chamber of the scanning electron microscope as shown in FIG. 6, and the defects on the stencil mask 4 mounted on the XY stage are emitted from the electron source 21. 15kV ~ 20k
The electron beam 24 accelerated to V is focused by the magnetic field of the electromagnetic condenser lens 22, and the upper deflector 2a of the two-stage deflector is deflected.
The secondary electron image is reflected by the electromagnetic objective lens, is incident on the side surface of the stencil mask 4, and is incident on the side surface of the stencil mask 4. Is displayed. In the beam locking method, the excitation condition of the objective lens is different from that in normal observation, so the rotation angle is corrected and displayed. From this image, a white defect area 8 as shown in FIG. 4 (a) is recognized. The scanning range is determined by the swing width of the lower deflector and the objective lens. In the case of a mask for EPL (LEEPL) by bringing the gas gun 10 close to the white defect region 8, the electron beam 24 is selectively scanned only in the defect region while flowing the raw material gas containing carbon, and FIG. The scatterer 7 of the carbon-containing film as shown in b) is grown. In the case of a mask for IPL, the electron beam 24 is applied to the defect area while flowing a source gas containing platinum (for example, C ₅ H ₅ Pt (CH ₃ ) ₃ ) or a source gas containing tungsten (for example, W (CO) ₆ ). Only Selectively Scan from Side View 4
The platinum- or tungsten-containing film scatterer 7 as shown in (b) is grown.

Next, a case where the present method is applied to a normal finishing process for correcting a black defect will be described. First, a black defect is repaired by taking into consideration the influence of cross-section sag with a vertically incident ion beam (Fig. 7 (a)). Next, using the beam rocking method, the relationship between the depth direction and the sag (Fig. Converted to Fig. 8 (b)) and selectively scan the side surface of the stencil mask to remove the portion of the stencil, thereby repairing the black defect with no sag in the cross section (Fig. 7).
(b)).

As can be seen from FIG. 1, in the beam locking method, not only the objective lens is used for focusing but also the beam is not passed through the center of the objective lens, so that the resolution is lowered by the aberration. However, the aberration caused by not passing through the center of the objective lens is the Curvilinear Variable Axis Le proposed by IBM.
If you optimize using aberration correction technology like ns (CVAL),
The reduction in resolution can be improved.

[0015]

As described above, according to the present invention, the black defect on the side surface of the stencil mask can be removed and the white defect film can be repaired from the side surface without tilting the stage. Further, if the present invention is applied to the finish processing for black defect correction, it is possible to perform black defect correction without side sagging.

[Brief description of drawings]

FIG. 1 is a conceptual diagram that best shows the features of the present invention.

FIG. 2 is a schematic cross-sectional view showing a conventional white defect correction method.

FIG. 3 is a schematic cross-sectional view illustrating a method of correcting a black defect.

FIG. 4 is a schematic cross-sectional view illustrating a method of correcting a white defect.

FIG. 5 is a schematic diagram for explaining a case where the present invention is applied to an ion beam defect repairing device.

FIG. 6 is a schematic diagram for explaining a case where the present invention is applied to a scanning electron microscope capable of introducing a carbon-containing gas.

FIG. 7 is a schematic cross-sectional view illustrating a case where the present invention is applied to correction of sag of a black defect processing cross section.

FIG. 8 is a diagram showing conversion of a relationship between a depth direction and a droop into a relationship between a side surface position and the number of scans.

[Explanation of symbols]

1 Condenser lens 2a Upper deflector 2b Lower deflector 3 Objective lens 4 Stencil mask 5 Ion beam or electron beam 6 Rocking point 7 Scatterer made of carbon-containing film 8 White defect region 9 Black defect region 10 Gas gun 11 Ion source 12 Electrostatic condenser lens 13 Electrostatic objective lens 14 Ion beam 15 Secondary ion detector or secondary electron detector 16 Secondary ion or secondary electron 21 Electron source 22 Electromagnetic condenser lens 23 Electromagnetic objective lens 24 Electron beam 25 Secondary electron detector 26 Secondary electron 27 Area where black defect is corrected by vertically incident ion beam 28 Dullness of cross section when black defect is corrected by vertically incident ion beam

Claims (5)

[Claims] 1. A defect repairing apparatus using an ion beam, wherein a deflector located above an objective lens is used to deflect, and an obliquely incident ion beam is used to form a deflection fulcrum near the stencil mask by swinging back the objective lens. A black defect repair method for a stencil mask, which comprises repairing a black defect on a side surface by physical sputtering. 2. The method of correcting a black defect according to claim 1, wherein an obliquely incident ion beam is used, which is deflected by a deflector above an objective lens, and a deflection fulcrum is formed near a stencil mask by swinging back the objective lens. A method for repairing a black defect in a stencil mask, which comprises repairing a black defect on a side surface of the stencil mask by gas-assisted etching. 3. The stencil according to claim 1, wherein a sag of a cross section when a black defect is repaired by a vertically incident beam is deflected by a deflector above the objective lens, and the objective lens is swung back. A stencil mask characterized by performing a black defect correction on a stencil mask with no cross-section sag by selectively scanning and removing according to the shape of the droop using an obliquely incident ion beam that forms a deflection fulcrum near the mask. How to fix black defects. 4. An ion beam defect repairing apparatus, wherein a stencil mask is formed by using an oblique incidence ion beam that is deflected by a deflector above an objective lens and forms a deflection fulcrum near the stencil mask by swinging back the objective lens. A method for repairing white defects in a stencil mask, which comprises repairing white defects by growing them from the side by FIB-CVD. 5. A scanning electron microscope capable of introducing a carbon-containing gas, using an obliquely incident electron beam which is deflected by a deflector above an objective lens and forms a deflection fulcrum near a stencil mask by swinging back the objective lens. A stencil mask white defect repairing method characterized by growing a white defect of a stencil mask by laterally growing it by an electron beam CVD method.