JPH11204403A - Mask correction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable removal of a black defect at a high selection ratio in a short period of time, by ejecting a reactive gas and radiating a converged ion beam to a black defect caused by a redundant defect of an absorber of an X-ray reduction exposure mask. SOLUTION: An X-ray exposure mask is manufactured by stacking a multilayer film 12 and a tungsten absorber 13, which is a shading part, on the upper part of a quartz substrate 11, subsequently carrying out predetermined patterning by electron beam lithography with an electron beam resist applied thereon, and etching the tungsten absorber 13 for pattern forming. When a redundant defect portion 14 of tungsten, presumably clue to the resist applying step, is generated on the multilayer film 12, the redundant defect portion 14 is irradiated with a converged ion beam 18 while xenon difluoride XeF2 16 is ejected near the redundant defect portion 14 through a nozzle. Thus, defect correction causing no damage to the underlying multilayer film 12 can be carried out in a short period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting a defect of a mask used for transferring a pattern having a high resolution using a beam in an X-ray region or a vacuum ultraviolet region, and a mask corrected by the defect correcting method. The present invention relates to a pattern transfer method using the same and a device manufactured using the pattern transfer method.

[0002]

2. Description of the Related Art In projection exposure for transferring a pattern of a semiconductor integrated circuit or the like drawn on a mask onto a wafer, resolution and depth of focus are important. Generally, assuming that the numerical aperture of the imaging optical system is NA and the exposure wavelength is λ, the resolution R and the depth of focus DOF are given by Equations 1 and 2, respectively.

[0003]

R = k ₁ λ / NA (1)

[0004]

## EQU2 ## DOF = k ₂ λ / NA ₂ (2) where k ₁ and k ₂ are constants.

At present, using a KrF excimer laser having a wavelength of 248 nm, a lens optical system having a NA of about 0.6, a phase shift mask, and a multilayer resist, the resolution is 0.13 μm.
A depth of focus of 1 μm has been realized. In order to increase the density of a semiconductor integrated circuit, a projection exposure method with higher resolution is required. As can be seen from Equation 1, the resolution increases as the NA increases or as the exposure wavelength decreases. However, when the NA is increased, the depth of focus is reduced according to Equation 2, and there is a limit to achieving high resolution by this method.

On the other hand, when the exposure wavelength is shortened to a soft X-ray range of several tens nm or several nm, it is possible to achieve a resolution of 0.1 μm or less while securing a depth of focus of 1 μm. However, since the refractive index of a substance is very close to 1 with soft X-rays, it is difficult to apply a lens type optical system, and it is necessary to use a mirror (reflection type) optical system.

In recent years, a multilayer mirror in which a large number of thin films of two kinds of materials having different refractive indices are alternately laminated has been put to practical use.
Lines can be reflected with high efficiency at any angle of incidence. Therefore, an X-ray projection exposure method using an imaging optical system using a multilayer mirror has been actively studied.

Assuming that the period length of the multilayer film is 反射, the reflection wavelength is λ, and the incident angle is θ (direct incidence at θ = 0 °), reflection occurs when the condition of Equation 3 is satisfied.

[0009]

2Λcos θ = nλ (n = 1, 2, 3, 4,...) (3) The reflection of the multilayer film has selectivity. It can be seen that the area changes.
The mask for X-ray reduction exposure forms this soft X-ray reflection multilayer film on a smooth substrate to form a soft X-ray reflection portion, and forms a soft X-ray absorbing substance on the reflection portion ( It has a reflective structure in which a non-reflective portion (light-shielding portion) is formed by patterning the absorber by means such as an absorber and etching.

[0010]

FIG. 4A shows a sectional structure of a reflective mask for X-ray reduction exposure. Smooth substrate 4
Mo / Si multilayer film 41 that reflects soft X-rays on the surface 5 with high efficiency
After a W (tungsten) absorber layer that does not reflect X-rays is formed on the multilayer film, a desired circuit pattern 42 is formed by means such as dry etching.

FIG. 4 shows a cross-sectional structure of a mask having such a structure in the case where there is an excess black defect in the absorber.
(B). Compared to FIG. 4A, extra W particles 43 about half the size of the W pattern are extraly attached between the W patterns on the mask surface.

Conventionally, such black defects have been removed by sputter etching using FIB. Compared to the lift-off method, there are advantages such as fewer steps and fewer new defects. However, for a mask for X-ray reduction exposure, the high-acceleration ions damage the underlying multilayer film layer of the defective portion, reducing the reflectance, and lowering the contrast of the transfer pattern in the corrected portion. There is a problem.

An almost similar correction method is described in, for example, OSA Proceedings Series (OSA Pr.
oceedings Series), vol.23, 204 (1991). Using 25 keV Ga ions (Mo
/ Si) Absorber on multilayer film (Au; 50 nn / Cr; 5)
nm), but the reflectivity of the multilayer film was greatly reduced due to the influence of soft X-ray absorption by the implanted Ga.

[0014] Further, regarding the method of correcting the mask in the case where the white defect 44 is missing from the absorber shown in FIG.
While supplying hydrocarbon-based gas to the vicinity of the white defect, the white defect is irradiated with FIB, and the elements contained in the ion beam
There is a method of forming a hydrocarbon-based film to form a light-shielding film and correcting defects.

An almost similar correction method is described in, for example, Journal of Vacuum Science and Technology (J. Vac. Sci. Technol.) B12, 3833 (19).
94). Here, a Ga beam is irradiated while supplying phenylacetylene to the white defect region to deposit a Ga—C film having a thickness of about 50 nm. Materials that compensate for the absence of the absorber must have the same X-ray absorptivity at the exposure wavelength as the absorber, have sufficient resistance to the mask cleaning process, and have good adhesion to the absorber material Is required. However, in the conventional method, the material deposited on the missing defect is limited to a substance constituting the ion beam or its compound, and it is very difficult to find a substance satisfying all the above-mentioned conditions.

As described above, no effective repair method has been disclosed for the surplus or missing defect of the absorber of the conventional mask for X-ray reduction exposure.

The present invention has been made in view of the above background, and is intended to correct a missing defect or an excess defect of an absorber of an X-ray reduction exposure mask without damaging the underlying multilayer film. It is an object of the present invention to provide a method for correcting a defect of an X-ray reduction exposure mask that allows a wide selection of materials.

[0018]

According to the present invention, with respect to a black defect caused by a surplus defect of an absorber of an X-ray reduction exposure mask, the defect is increased by injecting a reactive gas and irradiating an FIB. It became possible to remove in a short time with a selective ratio. Regarding white defects caused by missing defects of the absorber, the FIB is irradiated by injecting a reaction gas containing a substance constituting the absorber or a substance having similar optical properties to the substance of the absorber, and irradiating the FIB. Defects can be corrected with any kind of element or compound.

[0019]

(Embodiment 1) Hereinafter, the first embodiment of the present invention will be described.
Will be described with reference to the drawings. FIG. 1 shows a method of applying the defect repair method for an X-ray reduction exposure mask according to the first embodiment.
It is sectional drawing of the mask for X-ray reduction exposure which has an excess defect in an absorber, (a) is sectional drawing before correction, (b) is sectional drawing of a repair process, (c) is sectional drawing after repair. .

The mask for X-ray reduction exposure comprises a quartz substrate 11, a (Mo / Si) multilayer film 12 disposed on the quartz substrate 11, and a W (tungsten) absorber 13 as a light shielding portion. The (Mo / Si) multilayer film 12 was formed by ion beam sputtering to form a 50-layer pair having a period length of 6.7 nm, followed by forming the W absorber layer to a thickness of 100 nm. Thereafter, an electron beam resist was applied, predetermined patterning was performed by electron beam drawing, and the W absorber 13 was dry-etched to form a pattern, thereby manufacturing a mask. Then, as shown in FIG. 1A, a surplus defect portion 14 of W occurred on the multilayer film 12, which is considered to be caused by the resist coating process.

Therefore, as shown in FIG. 1B, the mask for X-ray reduction exposure is put into a mask defect correcting apparatus, and the mask is exposed to about 10 ^-6.
Evacuated to Torr. While spraying xenon difluoride XeF ₂ 16 through a nozzle in the vicinity of the surplus defect portion 14, the defect portion is irradiated with FIB 18. Thus, as shown in FIG. 1C, the surplus defective portion 14 is removed by etching, and the mask pattern is corrected.

In the conventional defect repair method for the X-ray reduction exposure mask, the (Mo / Si)
The reflectivity of the multilayer film 17 was only 50% of the multilayer film reflectivity of the reflective portion 15 of the mask. However, in the case of the correction method of the present embodiment, the multilayer reflectance of the reflective portion 15 of the mask is 99.
It was 5%. Considering the measurement error of the soft X-ray reflectometer, it can be said that the reflectance of the underlying multilayer film of the defective portion is substantially the same before and after the repair of the surplus defect. This is different from the conventional method.
This is probably because the selectivity of etching of the excess absorber to the (Mo / Si) multilayer film was improved by 15 times, and the underlying multilayer film of the excess defect was not damaged. In addition, the processing speed is four times that of the related art, and the time required for correcting the mask can be reduced to 70% of that of the related art.

When pattern transfer was performed using the mask modified by the method described in the first embodiment, the portion that was an excess defect was transferred as a resist pattern on the wafer, and the formed resist was transferred. The pattern dimensions were also within acceptable limits.

(Embodiment 2) Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a cross-sectional view of an X-ray reduction exposure mask having a defect missing in an absorber, to which the method of correcting defects of the X-ray reduction exposure mask of the second embodiment is applied;
(A) is a cross-sectional view before correction, (b) is a cross-sectional view of a correction process,
(C) is a sectional view after correction.

An X-ray reduction exposure mask is formed in the same manner as in the first embodiment. Then, as shown in FIG. 2A, the missing defect portion 2 which is considered to be caused by the resist coating process
4 occurred in the absorber 23 which is a light shielding portion.

Therefore, as shown in FIG. 2B, the mask for X-ray reduction exposure is put into a mask defect repairing apparatus, and about 10 ^−6.
Evacuated to Torr. The tungsten carbonyl gas W (C) vaporized through the nozzle near the missing defect portion 24
O) while blowing ₆ 26, FIB28 in the defect
Is irradiated. As a result, as shown in FIG. 2C, a W film is deposited, a deposited portion 27 is formed, and the missing defect portion 24 is corrected.

Since the deposited portion 27 thus deposited is the same material as the absorber 23, there is no problem in adhesiveness.
No problems such as pattern peeling occurred in the cleaning for the line reduction exposure mask.

Pattern transfer was performed using the mask modified by the method of this embodiment, but the missing defect was not transferred onto the wafer. Also, the dimensional accuracy of the resist pattern corresponding to the reflective portion of the mask in contact with the missing defect portion was within the allowable range.

(Embodiment 3) Next, as a third embodiment of the present invention, an example in which a semiconductor device is manufactured will be described. N-substrate 3
0 was formed by a usual method to form a P well layer 31, a P layer 32, a field oxide film 33, a poly-Si / SiO ₂ gate 34, a P high concentration diffusion layer 35, an N high concentration diffusion layer 36 (FIG. 2 ( a)). Next, an insulating film 37 of BPSG or the like is formed by a usual method.
Was formed (FIG. 2B). After a resist 40 was applied thereon, inspection was performed using the method described in the first embodiment of the present invention, and a hole pattern was formed using a mask modified by an FIB apparatus (FIG. 2C). .

Next, using this resist as a mask, the insulating film 3 is formed.
7 was dry-etched to form a contact hole. Then, after forming the W / Ti electrode wiring 38 by a normal method, an interlayer insulating film 39 was formed by CVD (FIG. 2D). Subsequent steps were formed by the same method as usual. Although only the main manufacturing steps have been described in this embodiment,
The same process as the conventional process was used except that the mask used in the lithography process for forming the contact hole was modified using the first embodiment of the present invention. Since the processing accuracy of mask defect correction is improved compared to the conventional method, CMOS
-An LSI can be manufactured with a high yield.

In the above embodiment, the defect correction of the absorber of the X-ray reduction exposure mask was described. However, the present invention is directed to the correction of the shifter layer of the phase shift mask for X-ray reduction exposure, and the multilayer film and the absorber layer. The same method can be applied to the complete removal of the etching stopper layer that may be formed during the process, and is not limited to a mask device for X-ray reduction exposure at an exposure wavelength of 13 nm. It goes without saying that the present invention can be applied to any wavelength in the ultraviolet or extreme vacuum ultraviolet region.

Further, in the above embodiment, the chipping defect of the absorber was corrected by depositing a W film made of the same material as the absorber, but it is not always necessary to use the same material as the absorber. A film of a material having optical properties similar to a substance may be formed. Although the Ga beam is used as the FIB, it goes without saying that the configuration of the present invention is not limited to the type of the FIB beam.

[0033]

As described above, according to the present invention, the defect which does not damage the underlying multilayer film is corrected by correcting the excess defect of the absorber of the mask for X-ray reduction exposure using FIB-assisted etching. Modifications were made faster. Regarding the missing defect of the absorber, a gas containing a substance constituting the absorber or a substance having a similar optical property to the substance of the absorber is blown to the vicinity of the defect to irradiate the FIB with the defect. It becomes possible to correct by the kind of element or compound.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a method for correcting a defect of an X-ray reduction exposure mask according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a method of correcting a defect of an X-ray reduction exposure mask according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a cross-sectional structure of a device manufactured by using a third embodiment of the present invention.

FIG. 4 is a sectional view showing a defect of an absorber of the X-ray reduction exposure mask.

[Explanation of symbols]

11 ... quartz substrate, 12 ... (Mo / Si) multilayer film, 13 ...
W absorber, 14 ... W absorber excess defect portion, 15 ... Multilayer film of reflective portion of mask, 16 ... Xenon difluoride, 17 ... Multilayer film of base of excess defect, 18 ... FIB, 23 ... W absorber, 2
4 ... W absorber missing defect part, 26 ... Tungsten carbonyl gas, 17 ... Deposition part, 18 ... FIB, 30 ... N-substrate, 31 ... P well layer, 32 ... P layer, 33 ... Field oxide film, 34 ... polySi / SiO ₂ gate, 35: P high concentration diffusion layer, 36: N high concentration diffusion layer, 37: insulating film, 3
8 W / Ti electrode wiring, 39 interlayer insulating film, 40 resist, 41 Mo / Si multilayer film, 42 W (tungsten) absorber pattern, 43 W particles (black defect), 44 W absorption White defect with missing body, 45 ... substrate.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroaki Oizumi 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside Central Research Laboratory, Hitachi, Ltd.

Claims (10)

[Claims] A mask having a structure in which a substance that hardly reflects soft X-rays is patterned on a multilayer film that reflects soft X-rays is illuminated with a beam in a soft X-ray region through an illumination optical system,
X-ray reduction exposure for reducing and transferring a fine pattern drawn on the mask onto a wafer substrate via an imaging optical system, and correcting a black defect caused by excess absorber on the mask. A method of repairing a defect in a mask, comprising: removing and correcting the defective portion by irradiating a focused ion beam (FIB) while injecting a gas into the black defective portion. 2. A mask having a structure in which a substance hardly reflecting soft X-rays is patterned on a multilayer film reflecting soft X-rays is illuminated with a beam in a soft X-ray region through an illumination optical system,
X-ray reduction exposure for reducing and transferring a fine pattern drawn on the mask onto a wafer substrate via an imaging optical system, a defect correction method for correcting a white defect caused by a missing absorber on the mask In the mask, wherein a gas containing an element constituting the absorber is injected into the defect portion and FIB is irradiated to deposit a reactant on the defect portion and correct the defect portion. Defect correction method. 3. A mask having a structure in which a substance that hardly reflects soft X-rays is patterned on a multilayer film that reflects soft X-rays is illuminated with a beam in the soft X-ray region through an illumination optical system,
X-ray reduction exposure for reducing and transferring a fine pattern drawn on the mask onto a wafer substrate via an imaging optical system, and correcting a black defect caused by excess absorber on the mask. An apparatus for repairing a defect of a mask, comprising: means for removing and repairing the defective portion by irradiating gas and FIB to the black defective portion. 4. A mask having a structure in which a substance that hardly reflects soft X-rays is patterned on a multilayer film that reflects soft X-rays is illuminated with a beam in a soft X-ray region through an illumination optical system;
X-ray reduction exposure for reducing and transferring a fine pattern drawn on the mask onto a wafer substrate via an imaging optical system, defect correction for correcting a white defect caused by a missing absorber on the mask. The apparatus may further include means for injecting a gas containing an element constituting the absorber into the defective portion and irradiating the FIB with FIB, thereby depositing a reactant on the defective portion and correcting the defective portion. Characteristic mask defect repair device. 5. A method according to claim 1, wherein said gas is a reactive gas containing an element such as Cl, H, F or the like. 6. The gas according to claim 2, wherein the gas is a reactive gas containing an element having substantially the same or similar optical properties as the element contained in the absorber at the exposure wavelength. To correct mask defects. 7. A method for transferring a fine pattern, comprising using a mask modified by the modification method according to claim 1. 8. An exposure apparatus comprising a mask corrected by the correction method according to claim 1. 9. A light source for emitting a beam in the soft X-ray region according to claim 7, wherein the light source is a synchrotron radiation light, a laser plasma X-ray source, an X-ray laser, an electron beam excitation type X-ray source, A fine pattern transfer method characterized by being one of an excimer laser and a semiconductor laser. 10. An electronic device manufactured by using the fine pattern transfer method and exposure apparatus according to claim 7.