JP4806877B2 - Correction method for halftone phase shift mask - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for correcting a residual defect of a phase shift mask used in a photolithography process in the manufacture of a semiconductor element.
[0002]
[Prior art]
Conventionally, various types of phase shift masks have been proposed. For example, a Levenson-type phase shift mask having a structure in which a transparent film that reverses the phase is provided on one side adjacent to the opening on the mask, or a phase shifter below the resolution limit is formed in the periphery of the pattern to be formed There are a phase shift mask having a structure auxiliary pattern, a self-aligned phase shift mask having a structure in which a chrome pattern is formed on a substrate and an overhang of a phase shifter is formed by overetching.
[0003]
Apart from the above structure, a transmission phase shift mask, a halftone type phase shift mask, and the like are also known as a phase shift mask formed only by a shifter pattern. The transmission type phase shift mask is a phase shift mask that separates patterns by utilizing the fact that the light intensity is zero at the boundary portion between the light transmitted through the transparent portion and the light transmitted through the phase shifter. It is also called an edge-based phase shift mask.
[0004]
The halftone phase shift mask forms a so-called translucent phase shifter pattern on the substrate that is partially transmissive to the projection exposure light, and the light intensity formed at the boundary of the phase shifter pattern is zero. This is a phase shift mask in which the pattern resolution is improved at a portion. Since the transmission phase shift mask and the halftone phase shift mask have a simple structure, they have an advantage that the manufacturing process is easy and there are few defects on the mask.
[0005]
As shown in FIGS. 2A to 2E, it is a side sectional view showing a manufacturing process of a halftone phase shift mask. The manufacturing process will be briefly described with reference to FIG.
[0006]
In FIG. 2A, a halftone material film 3 is formed on one surface of the transparent substrate 2. As a film forming method, a vacuum deposition method or a sputtering method is generally employed. A predetermined metal film is formed to a predetermined film thickness. Next, products that pass the appearance inspection and the standard inspection are selected.
[0007]
In FIG. 2B, an electron beam sensitive resist film 7 is formed on the entire surface of the halftone material film 3 formed on the surface of one side of the substrate 2. The resist coating method is manufactured using a spin coating method. Only non-defective products are selected after all side inspections. The transparent substrate 2 (photomask blank 6) on which the resist film is formed is put into the process.
[0008]
Next, in FIG. 2 (c), drawing is performed on the resist layer 7 of the photomask blank 6 by electron beam irradiation by means of an electron beam irradiation device using necessary mask data prepared in advance.
[0009]
Next, as shown in FIG. 2D, the development and the halftone material film 3 exposed by the development are etched.
[0010]
In FIG. 2E, a halftone phase shift mask is completed by peeling off the unnecessary resist layer 7 and cleaning it.
[0011]
Next, as shown in FIG. 3, (a) is a plan view of the halftone phase shift mask, and (b) is a side sectional view thereof.
[0012]
Next, FIG. 3C is a plan view having a shifter residual defect, and FIG. 3D is a side sectional view. In the process of manufacturing the halftone phase shift mask 1, the mask preparation process may be completed while the halftone material film 3 remains in a place where the halftone material film 3 should not exist. Hereinafter, the remaining halftone material film 3 is referred to as a shifter residual defect 5.
[0013]
The residual shifter defect 5 shown in FIGS. 3C and 3D does not contribute to improving the resolution of the mask pattern when used as the mask 1 as it is. It is transferred to cause a defect in a device pattern or the like. Therefore, in order to put it into practical use, it is necessary to make a correction for removing the residual defect 5 of the shifter. Conventional techniques often employ a method of irradiating the remaining defect 5 with a focused ion beam and evaporating and removing the remaining defect 5. As a correction method using a focused ion beam, a film is formed using a focused ion beam apparatus (FIB apparatus) of a gas such as gallium or argon, and correction is performed by trimming, or a predetermined gas is excited by an ion beam and etching is performed. There is also a way to fix it.
[0014]
However, this method has a problem that the transparent substrate 2 around the remaining defect portion 5 is inevitably damaged by irradiation of the ion beam, and it is required to accurately irradiate only the remaining defect portion 5 with the ion beam. ing.
[0015]
In general, in order to distinguish between the residual defect portion 5 of the shifter and the transparent substrate 2 around it, a method of monitoring the amount of secondary electrons emitted is employed. The difference between the amount of secondary electrons emitted from the residual defect portion 5 of the shifter and the amount of secondary electrons emitted from the surrounding transparent substrate 2 is displayed and identified by replacing it with light and dark on the screen of the correction device. It is.
[0016]
[Problems to be solved by the invention]
However, in the conventional technique, the difference in the amount of secondary electrons between the residual defect portion 5 of the shifter and the surrounding transparent substrate 2 is small on the screen of the correction device, so that the shifter remains on the screen of the correction device. In many cases, the boundary between the defective portion 5 and the surrounding transparent substrate 2 cannot be clearly recognized, and the ion beam cannot be accurately irradiated only to the remaining defective portion 5 of the shifter.
[0017]
The present invention provides a method for correcting the remaining defect portion 5 of the halftone phase shift mask 1 in order to solve the above-mentioned problems, and the remaining defect portion of the shifter using the conventional FIB apparatus. This method provides a method for confirming and correcting only 5 on the monitor screen.
[0018]
[Means for Solving the Problems]
The invention according to claim 1 of the present invention is a method for correcting a residual defect in a phase shift mask in which a halftone material film is provided as a phase shifter patterned in a desired shape on an upper surface of a transparent substrate. A halftone phase characterized in that after the ions are filled, the position of the remaining defect portion is specified, and the remaining defect portion is irradiated with a focused ion beam to remove and correct the remaining defect portion. This is a method for correcting a shift mask.
[0019]
According to a second aspect of the present invention, in the method for correcting a residual defect of the halftone phase shift mask according to the first aspect, the halftone material film is made of a zirconium silicide compound. This is a method for correcting a phase shift mask.
[0020]
The invention according to claim 3 of the present invention is the method for correcting a residual defect of the halftone phase shift mask according to claim 1 or 2, wherein the ions filling the residual defect portion are gallium ions. This is a method for correcting the halftone phase shift mask.
[0023]
[Action]
In the modified method of residual defects of the halftone type phase shift mask 1 by a child prefilled with ions remaining defect 5, the amount of secondary electrons emitted from the remaining defect portion 5 is increased, the correction device On the screen, the contrast between the residual defect portion 5 of the shifter and the transparent substrate 2 is increased. As a result, the position and boundary line of the residual defect portion 5 of the shifter can be accurately grasped, and the defect portion is repaired. Thus, only the remaining defect portion 5 of the shifter can be accurately irradiated with the ion beam.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail below along the embodiments.
[0025]
FIG. 1 shows an embodiment of the present invention and is a process diagram illustrating a method for correcting a remaining defect portion of a halftone phase shift mask.
[0026]
FIG. 1A is a side sectional view showing the remaining defect portion of the halftone phase shift mask, and is used in the correction process of the present invention in order to correct the remaining defect portion 5.
[0027]
Next, in FIG. 1B, the surface of the halftone material film layer 3 is filled with a predetermined ion beam using an FIB apparatus.
[0028]
In the irradiation method, first, an ion gas to be filled is prepared by means prescribed by the FIB apparatus. In the present invention, gallium ions were selected. As described above, the evaluation was made based on the effect of increasing the amount of secondary electrons emitted. Next, the irradiation condition of the focused ion beam is set to an upper limit at which the surface of the exposed transparent substrate 2 is not damaged. As an example, the conditions were set by selecting optimum conditions in the range of an acceleration voltage of 30 kV, a beam diameter of 25 nm to 35 nm , and a dose amount of 0.020 nC / μm ^{2 to} 0.030 nC / μm ² .
[0029]
In the present invention, a zirconium silicide compound was selected as the halftone material film layer 3.
[0030]
In FIG. 1C, a full inspection is performed using a defect inspection machine.
[0031]
Next, in FIG. 1D, the position of the remaining defect portion 5 and the defect portion 5 are displayed and identified on the screen of the correction device by means of the FIB apparatus.
[0032]
Next, the unnecessary remaining defect portion 5 is removed by using a correction means (gas assist etching method) of the FIB apparatus. As an example of the conditions, the acceleration voltage is 30 kV, the beam diameter is 25 nm to 35 nm , the dose amount is in the range of 0.075 nC / μm ^{2 to} 0.090 nC / μm ² , and the conditions are set. did. A predetermined gas is excited by the focused ion beam under the above conditions, and unnecessary defect portions 5 are removed by etching and corrected.
[0033]
【Example】
Next, the halftone phase shift mask manufacturing process of the present invention will be described below according to specific examples.
[0034]
<Example 1>
As shown in FIG. 2, the manufacturing process of the halftone phase shift mask will be described. First, in FIG. 2A, a halftone material film layer (semi-transparent phase shifter layer) 3 made of ZrSiOx having a required thickness is formed on one side of a photomask substrate (transparent substrate) 2 made of quartz glass.
[0035]
Next, in FIG. 2B, an electron beam sensitive resist film layer 7 having a required thickness is formed on the entire surface of the halftone material film 3. In general, a material in which the material film layer 3 is formed on the transparent substrate 2 and the electron beam sensitive resist film layer 7 is formed is referred to as a photomask blank 6.
[0036]
Subsequently, FIG. 2 (c) is drawn by electron beam irradiation on the electron beam sensitive resist film layer 7 of the photomask blank 6 by using an electron beam drawing device 8 and using photomask data prepared in advance. To do.
[0037]
Next, as shown in FIG. 2D, an unnecessary electron beam sensitive resist film layer 7 is removed and washed by a development process to form a required electron beam sensitive resist film layer 7.
[0038]
Next, as shown in FIG. 2 (e), the exposed halftone material film layer 3 made of ZrSiOx is etched using the electron beam sensitive resist film layer 7 as a mask to obtain a required halftone material made of ZrSiOx. A film layer was formed, and then the electron beam sensitive resist film layer 7 was peeled off to prepare a halftone phase shift mask 1.
[0039]
In the halftone phase shift mask 1, the shifter residual defect 5 shown in FIGS. 3C and 3D was present.
[0040]
The process of correcting the remaining defect portion 5 of the halftone phase shift mask 1 will be described below with reference to FIGS.
[0041]
As shown in FIG. 1A, it is a side sectional view of the halftone phase shift mask 1 having a remaining defect portion 5, and is put into a correction process for removing the remaining defect portion 5.
[0042]
In FIG. 1B, the defect portion of the halftone material layer surface (ZrSiOx film) 3 on the halftone phase shift mask 1 having the remaining defect portion 5 is intensively irradiated with a gallium focused ion beam to obtain ZrSiOx. The surface of the film was filled with gallium ions. The FIB apparatus is used as the gallium focused ion beam irradiation apparatus, the irradiation condition is set to an acceleration voltage of 30 kV, the gallium focused ion beam diameter is limited to 30 nm , and the dose (current density) is 0.025 nC / μm ² . The gallium focused ion beam was irradiated. The above conditions were that the gallium focused ion beam was irradiated at a dose (current density) lower than that in the case of removing the remaining defect portion 5 by normal focused ion beam irradiation.
[0043]
In FIG. 1C, a full inspection is performed using a defect inspection machine. Next, the residual defect portion 5 that needs to be removed and corrected is confirmed on the screen of the inspection and correction device, and transferred to the FIB device for removal and correction.
[0044]
Next, as shown in FIG. 1D, a region including the remaining defect portion 5 is designated on the correction screen of the FIB apparatus, and a portion that is brightly displayed on the screen (a lot of secondary electrons are emitted). The remaining defect portion 5 was removed by irradiating only the remaining defect portion 5 with the gallium focused ion beam. (See Figure 1e)
[0045]
The irradiation conditions of the focused gallium beam shown in FIG. 1 (e) are an acceleration voltage of 30 KV, a gallium focused ion beam diameter of 30 nm , and a dose of 0.08 nC / μm ² . As a result, only the remaining defect portion 5 could be removed, and the transparent substrate 2 around the remaining defect portion 5 was not damaged at all.
[0046]
【The invention's effect】
According to the present invention, there is an effect that a defect-free halftone phase shift mask can be manufactured by removing and correcting the remaining defective portion of the halftone phase shift mask without damaging the transparent substrate, thereby eliminating the problem.
[Brief description of the drawings]
FIGS. 1A to 1E are process diagrams showing a method of correcting a remaining defect portion of a halftone phase shift mask according to the present invention.
FIGS. 2A to 2E are process diagrams showing a manufacturing process of a halftone phase shift mask of the present invention.
FIGS. 3A and 3B are schematic views showing an example of a conventional halftone phase shift mask, in which FIG. 3A is a plan view, FIG. 3B is a side sectional view, and FIG. 3C is a halftone having a residual defect; It is a top view of a type | mold phase shift mask, (d) is a sectional side view of the halftone type | mold phase shift mask which has a residual defect.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Halftone type phase shift mask 2 ... Transparent substrate 3 ... Halftone material film layer (Semitransparent phase shifter material layer)
4 ... Main pattern 5 ... Residual defect 6 ... Photomask blank 7 ... Electron beam sensitive resist film 8 ... Electron beam drawing apparatus 9 ... Gallium focused ion beam irradiation 10 ... Gas-assisted etching focused ion beam irradiation

Claims (3)

In a method for correcting a residual defect of a phase shift mask in which a halftone material film is provided as a phase shifter patterned in a desired shape on the upper surface of a transparent substrate, after filling the residual defect with ions, the residual defect A method for correcting a halftone phase shift mask, characterized in that a position is specified and the remaining defect portion is irradiated with a focused ion beam to remove and correct the remaining defect portion. 2. The method for correcting a residual defect of a halftone phase shift mask according to claim 1, wherein the halftone material film is made of a zirconium silicide compound. 3. A method for correcting a residual defect of a halftone phase shift mask according to claim 1 or 2, wherein ions filling the residual defect portion are gallium ions. .

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