JP3630935B2 - Defect correction method for halftone phase shift mask - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a defect correction method for a phase shift mask used in phase shift lithography, and more particularly to a defect correction method for a halftone phase shift mask.
[0002]
[Prior art]
A phase shift mask is used as one of photomasks used when a fine pattern is transferred by a projection exposure apparatus in the manufacture of a semiconductor LSI or the like. This phase shift mask can improve the resolution of the transfer pattern by providing a phase difference between the exposure light passing through the mask. As one of the phase shift masks, a phase shift mask described in Japanese Patent Laid-Open No. 4-136854 is known as a mask particularly suitable for transferring isolated hole and line & space patterns.
[0003]
This phase shift mask forms a semi-transparent film (half-tone phase shift film) on the transparent substrate, which transmits light of an intensity that does not substantially contribute to exposure and simultaneously shifts the phase of the light passing therethrough. By selectively removing a part of the light-transmitting film and forming a semi-light-transmitting film pattern, a light-transmitting portion (transparent substrate exposed portion) that transmits light having an intensity that substantially contributes to exposure, and substantially And a semi-transparent portion that transmits light having an intensity that does not contribute to exposure. This phase shift mask shifts the phase of the light passing through the semi-translucent portion, so that the phase of the light passing through the semi-transparent portion is substantially inverted with respect to the phase of the light passing through the translucent portion. Thus, the contrast of the boundary portion can be satisfactorily maintained so that the light passing through the vicinity of the boundary between the semi-translucent portion and the translucent portion cancels each other and cancels each other. This is commonly referred to as a halftone phase shift mask.
In this phase shift mask, when the wavelength of the exposure light is λ and the refractive index of the semi-transparent film with respect to the exposure light is n, the thickness t of the semi-transparent film is t = λ / {2 (n−1). )}
Generally, it is set to a value satisfying the above, and the transmittance of the semi-transparent film at the wavelength of the exposure light is usually set to about 1 to 50%.
[0004]
As described above, the halftone phase shift mask has two functions of a phase shift function for shifting the phase of the exposure light by the semi-transparent portion and a light shielding function for substantially blocking the exposure light. . That is, this semi-transparent portion functions as a phase shift layer at the boundary portion of the pattern, and functions as a light shielding layer at other portions. Therefore, a slight amount of light leaks even in a portion where it is ideal to completely block exposure light. Normally, the entire exposure amount is adjusted so that the substantial exposure is not reached even if this leakage light is present.
[0005]
Such a halftone phase shift mask requires higher accuracy than a normal photomask, and the accuracy of optical characteristics and the like of a defect-corrected portion is no exception.
Normally, missing defects generated in a photomask are corrected by using a focused ion beam (FIB) to dissociate and excite vapor such as pyrene by Ga ions to deposit a carbon film on the missing defects. On the other hand, the defect defect correction in the halftone phase shift mask is performed, for example, as disclosed in Japanese Patent Laid-Open No. 7-146544. It is almost the same as the film. Specifically, the phase difference is 120 to 240 ° and the transmittance is 5 to 15%.
[0006]
[Problems to be solved by the invention]
However, in the defect correction method described in the above-mentioned Japanese Patent Application Laid-Open No. 7-146544, a lift-off method or the like is adopted as a means for forming a film of substantially the same material as the semi-transparent film on the missing defect portion. The method is complicated and difficult to control in practice. The publication does not consider the relationship between the film quality and film thickness and the optical characteristics.
[0007]
Considering these, it is desirable that the defect defect correction in the halftone phase shift mask can be corrected by a method of depositing a carbon film by FIB on the defect defect part generally used in the past. It is desirable that the property of the correction film deposited on the defective portion matches the optical characteristics of the semi-transparent film as much as possible.
[0008]
The present invention has been made under the background described above, and a correction film having an optical property equivalent to or close to that of a semi-transparent film is deposited on a defect defect portion by a relatively simple method using an FIB apparatus. An object of the present invention is to provide a defect correction method for a halftone phase shift mask that can be used.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a defect correcting method for a halftone phase shift mask according to the present invention has the following configuration.
[0010]
(Configuration 1) A correction film made of the film material or a reaction product thereof is irradiated with an ion beam while supplying the film material to a missing defect of a halftone phase shift mask having at least a semi-transparent film pattern on a transparent substrate. In the defect correction method of the halftone phase shift mask that corrects the missing defect of the semi-transparent film pattern by depositing, after grasping the relationship between the light transmittance and the phase difference with respect to the thickness of the correction film to be deposited in advance, A defect correction method for a halftone phase shift mask, comprising depositing a correction film having a light transmittance and a phase difference substantially the same as those of the semi-transparent film based on these relationships.
[0011]
(Configuration 2) A defect correction method for a halftone phase shift mask according to Configuration 1, wherein the correction film to be deposited is a single layer film.
[0012]
(Configuration 3) In the defect correction method of the halftone phase shift mask manufacturing method according to Configuration 1 or 2, the diameter of the aperture mounted on the focused ion beam apparatus and the thickness of the correction film to be deposited are changed. A defect correction method for a halftone phase shift mask.
[0013]
(Structure 4) In the defect correcting method of the halftone phase shift mask manufacturing method according to structures 1 to 3, the correction film to be deposited is a carbon-based film. Defect correction method.
[0014]
(Configuration 5) A correction film made of the film material or a reaction product thereof is irradiated with an ion beam while supplying the film material to the missing defect of the halftone phase shift mask having at least a semi-transparent film pattern on the transparent substrate. In the defect correcting method of a halftone phase shift mask for correcting a defect defect of a semi-transparent film pattern by depositing, the correction film to be deposited substantially includes a light transmittance and a phase difference of the semi-transparent film. A defect correcting method for a halftone phase shift mask, characterized by being a single layer film that is the same.
[0015]
(Configuration 6) A correction film made of the film material or a reaction product thereof is irradiated with an ion beam while supplying the film material to the missing defect of the halftone phase shift mask having at least a semi-transparent film pattern on the transparent substrate. In a defect correction method for a halftone phase shift mask that corrects a missing defect of a semi-transparent film pattern by depositing, a correlation between a light transmittance and a phase difference with respect to a film thickness for each specific reaction condition in the correction film. The correction film is deposited by selecting the reaction conditions in advance so that the light transmittance and the phase difference of the correction film are substantially the same as the light transmittance and the phase difference of the semi-transparent film. A defect correction method for a halftone phase shift mask.
[0016]
[Action]
In the present invention, a method of depositing a carbon film or the like on the missing defect portion of the halftone phase shift mask by FIB is adopted, and the property of the correction film deposited on the missing defect portion is changed to the optical characteristic of the semi-transparent film. By bringing them closer, it is possible to obtain a halftone phase shift mask capable of efficiently correcting a defect and having high optical accuracy of a defect-corrected portion, and as a result, capable of transferring a pattern onto a wafer with high accuracy.
[0017]
Hereinafter, the present invention will be described in detail.
[0018]
FIG. 1 shows a schematic diagram of a focused ion beam (FIB) apparatus. In the FIB apparatus, the missing defect of the halftone phase shift mask 1 having at least a semi-transparent film pattern on a transparent substrate is irradiated with an ion beam 12 while supplying the film material from the nozzle 11, and the film material or its The defect defect of the semi-transparent film pattern is corrected by depositing a correction film made of a reactant.
[0019]
FIG. 2 shows the characteristics of the carbon film at the exposure wavelength i line (365 nm) deposited by the FIB apparatus. FIG. 3 shows the characteristics of the carbon film at the exposure wavelength g-line (436 nm) deposited by the FIB apparatus.
[0020]
In the present invention, after grasping the relationship between the light transmittance and the phase difference with respect to the film thickness of the film material to be deposited in advance, the light transmittance and the phase difference are substantially the same as the semi-transparent film based on these relationships. A correction film is deposited. Specifically, for example, as shown in FIG. 2 and FIG. 3, the optical characteristics of the correction film are controlled by changing the diameter of the aperture of the FIB apparatus, and the relationship between the film thickness, the transmittance, and the phase difference is controlled. Change. That is, as shown in FIG. 2 and FIG. 3, when the aperture diameter is not changed, the transmittance and phase difference corresponding to the film thickness can be obtained only uniquely (only a set of relational curves can be obtained). In the present invention, an optimum curve is selected from a plurality of relational curves obtained by changing the diameter of the aperture (having a phase difference of 180 ° and a transmittance closer to that of the semi-transparent film) By selecting the relationship curve) and strictly controlling the thickness of the correction film, the optical characteristics of the correction film can be matched or brought close to those of the semi-transparent film. The optical characteristics of the correction film can be changed by changing the aperture diameter because the amount of Ga ions in the ion beam irradiated from the ion source, in other words, the amount of energy per unit time depends on the size of the aperture diameter. This is considered to be because the refractive index changes by affecting the composition of the correction film (carbon film or the like) deposited by being controlled.
[0021]
In the present invention, the FIB correction film is matched with the characteristics of the halftone film, and therefore can be used regardless of the film material constituting the halftone film. Further, the defect correction of the light shielding film in the halftone phase shift mask of the type in which the light shielding film is formed in the non-transfer area of the mask can be performed simultaneously with the same apparatus.
In the case of the carbon correction film, it is possible to match the correction film by FIB to the characteristics of the halftone film within a range of 180 ° phase difference and transmittance of 1 to 50%.
[0022]
Examples of the raw material gas for forming the carbon correction film by FIB include hydrocarbon gases such as pyrene, styrene, methyl methacrylate, 2,4,4-trimethyl-1-pentene, and isoprene, or carbonization thereof. A mixed gas of hydrogen-based gas and hydrogen can be used.
[0023]
Examples of FIB correction films other than carbon-based films include W (tungsten), Mo (molybdenum), and Cr (chromium). The source gas for the tungsten correction film is WF ₆ , W (CO) ₆ , WCl _6, etc., and the source gas for the molybdenum correction film is MoF ₆ , Mo (CO) ₆ , MoCl _5, etc. Examples of the source gas include Cr (C ₆ H ₆ ) ₂ .
[0024]
In addition to changing the aperture diameter, the film quality can be controlled by changing the ion current of the FIB apparatus or changing the supply gas pressure.
[0025]
In the present invention, a correction film having a light transmittance and a phase difference substantially the same as that of the semi-transparent film can be formed with a single layer film by FIB, and thus correction is easy.
Here, “substantially the same” means that the optical characteristics of the semi-transparent film are not substantially changed. Specifically, in terms of the light transmittance, the light transmittance of the semi-transparent film is the same. The phase difference is within ± 2%, preferably within ± 1%, more preferably within ± 0.5%. The phase difference is within ± 20 ° of the phase difference of the semi-transparent film, preferably ± 10. It means that it falls within the range of °, more preferably within ± 5 °.
[0026]
【Example】
Hereinafter, the present invention will be described in detail based on examples.
[0027]
Example 1
4 to 5 are views for explaining a method for correcting a defect defect in a halftone phase shift mask according to an embodiment of the present invention.
[0028]
FIGS. 4A and 4B show a halftone phase obtained by patterning a semi-transparent film (halftone film) 3 made of a molybdenum silicide nitride film (MoSiN film) formed on the transparent substrate 2. It is the top view of the shift mask 1, and AA arrow sectional drawing. This mask is formed by applying an electron beam resist on a MoSiN film formed on a transparent substrate by sputtering and drawing using an electron beam drawing apparatus, developing the resist, and using the resist pattern as a mask, the MoSiN film Was obtained by patterning by etching, but had a missing defect 4 generated for some reason in these manufacturing processes. As a result of measuring the optical characteristics of the mask after manufacturing the mask, the phase difference was 180 ° and the transmittance was 4.0% at the exposure wavelength g-line (436 nm).
[0029]
Next, based on FIG. 3 obtained by preconditioning, the aperture diameter of the FIB apparatus is set to 50 μm, the film thickness is strictly controlled, and the carbon film 5 is deposited with a film thickness of 1620 Å to correct the missing defect. (FIGS. 5A and 5B). The carbon film had a phase difference of 180 ° at the exposure wavelength g-line (436 nm) and a transmittance of 3.8%, which was close to 4.0%.
[0030]
Although transfer onto the wafer was performed using the mask after correcting the missing defect, no abnormality due to the corrected portion was observed, and it was confirmed that the control of the optical characteristics of the corrected portion according to the present invention was highly accurate. It was.
[0031]
Example 2
A halftone phase shift mask obtained by patterning a semi-transparent film made of a molybdenum silicide nitride film (MoSiN film) formed on a transparent substrate was produced. This mask is formed by applying an electron beam resist on a MoSiN film formed on a transparent substrate by sputtering and drawing using an electron beam drawing apparatus, developing the resist, and using the resist pattern as a mask, the MoSiN film Was obtained by patterning by etching, but had missing defects caused for some reason in these manufacturing processes. As a result of measuring the optical characteristics of the mask after manufacturing the mask, the phase difference was 180 ° and the transmittance was 2.0% at the exposure wavelength i-line (365 nm).
[0032]
Next, based on FIG. 2 obtained by preconditioning, the aperture diameter of the FIB apparatus was set to 80 μm, the film thickness was strictly controlled, and a carbon film was deposited with a film thickness of 1400 Å to correct the missing defect. . The carbon film had a phase difference of 180 ° at an exposure wavelength i-line (365 nm) and a transmittance of 1.8%, which was close to 2.0%.
[0033]
Although the transfer onto the wafer was performed using the mask after correcting the missing defect, no abnormality due to the corrected portion was observed, and it was confirmed that the correction according to the present invention was highly accurate.
[0034]
Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to the above embodiments.
[0035]
For example, the semi-transparent film is not limited to those made of molybdenum, silicon, and nitrogen. For example, the semi-transparent film made of molybdenum, silicon, and oxygen, molybdenum, silicon, oxygen, and nitrogen, tungsten, titanium, and tantalum. A semi-transparent film made of a metal selected from chromium, silicon, oxygen, and / or nitrogen may be used.
[0036]
In addition, in a halftone phase shift mask of a type in which a light shielding film is formed in addition to a semi-transparent film, it is possible to simultaneously correct defects in the light shielding film with the same apparatus. As the light shielding film in this case, for example, a material containing at least one selected from chromium, oxygen, nitrogen, and carbon and chromium, a film of aluminum, titanium, tungsten, molybdenum silicide (MoSi), Or what consists of the material which included at least 1 type chosen from oxygen, nitrogen, and carbon in these is mentioned.
[0037]
Furthermore, in addition to the missing defect on the edge, it can be used to correct a missing defect such as a pinhole.
[0038]
【The invention's effect】
As described above, according to the defect correction method for a halftone phase shift mask of the present invention, a correction film having optical characteristics equivalent to or close to that of a semi-transparent film is missing by a relatively simple method using an FIB apparatus. Since the defect can be deposited and corrected, as a result, the influence of the defect is eliminated on the actual wafer transfer, and a high-quality halftone phase shift mask can be obtained efficiently and with a high yield.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of an FIB apparatus.
FIG. 2 is a diagram showing characteristics of a carbon film at an exposure wavelength i line (365 nm) deposited by an FIB apparatus.
FIG. 3 is a view showing characteristics of a carbon film at an exposure wavelength g-line (436 nm) deposited by an FIB apparatus.
4A and 4B are diagrams for explaining a method for correcting a defect defect in a halftone phase shift mask according to an embodiment of the present invention, in which FIG. 4A is a plan view, and FIG. It is A line arrow sectional drawing.
FIGS. 5A and 5B are diagrams for explaining a method for correcting a defect defect in a halftone phase shift mask according to an embodiment of the present invention, where FIG. 5A is a plan view, and FIG. It is B line arrow sectional drawing.
[Explanation of symbols]
1 Halftone phase shift mask 2 Transparent substrate 3 Translucent film (halftone film)
4 Missing defect 5 Carbon film 11 Nozzle 12 Focused ion beam

Claims (3)

The missing defect of the halftone phase shift mask having at least a semi-transparent film pattern on a transparent substrate is irradiated with an ion beam while supplying the film material using a focused ion beam apparatus, and the film material or its reaction product is irradiated. In a defect correction method for a halftone phase shift mask for correcting a missing defect in a semi-transparent film pattern by depositing a correction film,
In advance , the relationship between the light transmittance and the phase difference with respect to the thickness of the correction film to be deposited is grasped with respect to the diameters of the different apertures of the focused ion beam device, and then the light transmittance and the level are determined based on these relationships. The aperture diameter and film thickness of the focused ion beam apparatus are selected so that the phase difference is substantially the same as that of the semi-transparent film, and the correction film is deposited with the selected aperture diameter and film thickness. Defect correction method for halftone phase shift mask. The defect correction method for a halftone phase shift mask according to claim 1,
A defect correction method for a halftone phase shift mask, wherein the correction film to be deposited is a single layer film. The defect correction method for a halftone phase shift mask according to claim 1 or 2 ,
A defect correction method for a halftone phase shift mask, wherein the correction film to be deposited is a carbon-based film.

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