JP3350095B2 - How to fix the mask - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a phase shift mask and a method for repairing the mask.

[0002]

2. Description of the Related Art The demand for higher density and higher accuracy of semiconductor integrated circuits has been increasing year by year, and exposure methods, resist materials, and resist processes have been improved for the purpose of improving resolution. Under such circumstances, the improvement of the mask is no exception. In the case of a mask in which a light-shielding body is formed on a substrate that is transparent to light, the size of the light-shielding body is reduced, and the transmitted light from an adjacent opening is resolved. There is a problem that it will not work.

One technique for solving this problem is a phase shift method. This phase shift method is a technique for improving the resolution and contrast of a projected image by manipulating the phase of light transmitted through a mask. That is, in this method, a phase inversion layer is partially provided in the light transmitting portion, and the influence of diffraction of light from an adjacent pattern is removed.
Improve pattern accuracy. With the introduction of this method, the resolution and the depth of focus can be improved while following conventional processes other than the mask, such as a stepper and a resist process. However, on the other hand, when a phase shift mask is used, small shifter defects that could not be ignored in a conventional mask have been transferred onto a wafer, and have to be corrected.

[0004] Mask defects include convex defects and concave defects. Conventionally, the correction of the convex defect is performed by using laser evaporation, and the correction of the concave defect mask is caused by the fact that the light shielding body is not at a desired position. Therefore, the carbon film is deposited by FIB-assisted deposition. Has been done.

However, in the phase shift mask, FIG.
In both the case of a convex defect as shown in FIG. 18A and the case of a concave defect as shown in FIG. 18A, the defect to be repaired becomes smaller as described above, and the dimensional accuracy is insufficient with a laser. Such a defect has a phase shift of 18% for light passing through the defect.
A normal pattern is not transferred because it deviates from 0 degrees. Due to such shifter defects, the yield of mask manufacturing is 2
Since it is 5% or less, the shifter defect correction technology is an essential technology. Therefore, correction with a focused ion beam (FIB) that can be finely processed has been proposed. By using this FIB, in the case of a convex defect of the shifter of the phase shift mask, the defect can be corrected by removing the defect as shown in FIG. On the other hand, in the case of a concave defect, it is possible to correct it by excavating it to a desired phase as shown in FIG.

However, when defects are repaired by sputter etching using FIB, there is a problem in that the irradiated area is damaged by metal injection due to the use of a liquid metal ion source, and the transmittance of the shifter is reduced.

Therefore, a method of etching a damaged layer by using CF ₄ or CHF ₃ plasma has been proposed as a post-process for recovering the transmittance reduced by the damage. However, this method etches the entire mask so that the light-shielding member is etched. The anti-reflection film on the surface is etched at the same time, and the corner portion of the pattern has a higher etching rate, which causes a new problem that the side wall angle is deteriorated.

Further, since the focused ion beam assisted etching utilizes the reaction between the gas and the substance to be etched, the etching rate varies depending on the material of the defect, and the possibility of repair depends on the material of the defect. In other words, in order to maintain the transmittance, it is necessary to use a gas having a growth effect on the substrate as a gas. The problem is that the substrate is dug due to the rapid increase, and the desired pattern cannot be formed due to the effect of the edge of the dug region.

In order to avoid this decrease in transmittance, it is conceivable to locally deposit a light transmitting film without performing etching in the case of a concave defect of the phase shifter.
However, it is extremely difficult to locally deposit a light transmitting film having a light transmittance of 90% or more and a refractive index close to that of a shifter using a focused ion beam. A silicon oxide film can be deposited using a silicon focused ion beam of about 60 keV, but in this case, the light transmittance is 30%.
And it was impossible to use it for correcting a concave defect of a shifter.

Further, when performing focused ion beam etching, since the defect depth of the shifter is unknown, the etching end point cannot be determined only from the ion irradiation time from the etching rate of the ion beam. If the shifter can be etched and the substrate surface can be detected, the etching depth of the substrate can be determined by the ion irradiation time. However, when a silicon oxide film is used as the shifter, the shifter and the substrate usually have the same element. Since it is composed of (Si, O), surface detection by detecting secondary ions is impossible. As described above, when etching with a focused ion beam in defect correction of a shifter, there is a problem that it is difficult to detect an etching end point and high-precision correction cannot be performed.

[0011]

As described above, when defects are repaired by sputter etching by FIB, the irradiation area is damaged by metal injection because the liquid metal ion source is used, and the transmittance of the shifter decreases. There was a problem.

In order to avoid such a problem of a decrease in transmittance, in the case of a concave defect of a phase shifter, it is conceivable to deposit a light-transmitting film locally without performing etching. It has been extremely difficult to locally deposit a light transmitting film having a light transmittance of and a refractive index close to that of a shifter using a focused ion beam.

Furthermore, when focused ion beam etching is performed, since the shifter and the substrate are often made of the same element, it is impossible to detect the substrate surface by detecting secondary ions. For this reason, there is a problem that it is difficult to detect the etching end point, and it is not possible to perform a highly accurate correction.

A first object of the present invention is to provide a method of repairing a phase shift mask which does not cause a decrease in transmittance due to metal ion irradiation. It is another object of the present invention to suppress a decrease in transmittance and to locally correct a mask regardless of the material of a defect.

A second object of the present invention is to recover a decrease in transmittance due to correction. A third object of the present invention is to provide a method for correcting a concave defect of a phase shifter by local deposition.

A fourth object of the present invention is to provide a method of correcting a phase shift mask, which can easily detect the end point of etching and can perform high-precision correction.

[0017]

Therefore, in a first method of the present invention, a convex defect of a phase shifter including a light shield or a translucent film on a mask is removed by FIB assisted etching using a focused ion beam and a gas. It is characterized in that it is removed and a concave defect region of the phase shifter is dug to a desired depth.

Preferably, ion assisted etching is performed in the presence of a small amount of XeF ₂ gas so that the etching yield is 1.7 times or more that of sputter etching to remove defects in the mask.

More preferably, ion-assisted etching is performed in the presence of a small amount of XeF ₂ gas such that the etching yield is 1.7 times or more and 3 times or less of sputter etching to remove defects in the mask. .

Preferably, when the phase shifter is silicon or a silicon compound, a gas containing fluorine, chlorine or bromine is used as the gas.

More preferably, when the phase shifter is an organic film, O ₂ , O ₃ , NO or NO ₂ is used as a gas.

In the second aspect of the present invention, after removing defects using sputter etching of a focused ion beam, a substrate having reduced transmittance or a damaged layer of a phase shifter is removed by ion assist etching using XeF ₂ gas. Like that.

A third aspect of the present invention is characterized in that a thin film is deposited and corrected using a focused ion beam having an energy of 10 keV or less in a concave defect of the phase shifter.

Preferably, a silicon oxide film or a silicon nitride film is deposited and corrected in the concave defect of the phase shifter by using a silicon focused ion beam having an energy of 10 keV or less.

According to a fourth aspect of the present invention, an ion implantation layer is formed by implanting ions different from the shifter constituent elements into the surface of the substrate in a phase shift mask using a material whose main component is the same as the substrate as the phase shifter. are doing.

[0026]

According to the first aspect of the present invention, by performing focused ion beam assisted etching in the presence of a gas, the amount of etching per metal ion beam irradiation amount is increased, and a decrease in transmittance due to metal ion beam irradiation is prevented. Can be suppressed.

When the phase shifter is silicon or a silicon compound, if a gas containing fluorine or chlorine is used as a gas, not only a physical reaction but also a chemical reaction occurs, and volatile silicon is applied to the ion beam irradiation region. Since fluoride or silicon chloride is generated and the etching amount per ion increases, the number of irradiation ions for etching can be reduced. Therefore, it is possible to suppress a decrease in transmittance due to the metal ion beam irradiation.

Further, ion assisted etching was performed while changing the amount of XeF ₂ gas, and the change in transmittance with respect to the etching multiplication rate was measured. As a result, as shown in FIG. 4, if the ion assisted etching is performed using a small amount of XeF ₂ gas so that the etching yield becomes 1.7 times or more of the sputter etching, the defect of the mask can be removed. It was found that the decrease in transmittance was suppressed. Also,
By lowering the etching rate in the presence of a gas, the dependence of the etching rate on the material can be reduced, so that the processing can be performed with good controllability and the excavation accompanying exposure of the substrate can be suppressed. Here, the reason why the etching yield is set to 1.7 times or more of the sputter etching is based on an experimental result, and it is possible to prevent a decrease in transmittance. Also, the reason for setting it to be three times or less is that the material dependency becomes large after three times. This corrects not only the phase shifter but also all convex defects.

Further, when the phase shifter is an organic material film, if O ₂ , O ₃ , NO or NO ₂ is used as the gas, the organic material is decomposed in the ion beam irradiation region and carbon monoxide, carbon dioxide, Hydrocarbons, water, and the like are generated, and the amount of etching per metal ion beam irradiation amount increases, thereby suppressing a decrease in transmittance due to metal ion beam irradiation.

After the defect is removed by sputter etching with a focused ion beam, the damage layer of the phase shifter is removed by ion-assisted etching using XeF ₂ gas, and at the same time, the cause of the damage is increased by using the effect of increasing the etching rate due to the coexistence of gas. The amount of Ga ions to be implanted can be reduced, and a decrease in transmittance can be suppressed. Actually, as shown in FIG. 19, it was found that the transmittance can be recovered by removing the damaged layer of about 10 nm (at most 15 nm).

Further, as a result of various experiments, the present inventors have found that when changing the energy of the focused ion beam, 1
It was found that the thin film formed by using a focused ion beam having an energy of 0 keV or less has less damage and does not lower the transmittance, and further improves the deposition efficiency.
The third aspect of the present invention is made by paying attention to this point.
A thin film formed using a focused ion beam having an energy of eV or less has small damage and exhibits a light transmittance of 90% or more, so that a concave defect of a phase shifter can be satisfactorily corrected. Further, the transmittance does not decrease due to the metal ion beam irradiation unlike the case of etching, and the yield is greatly improved. A thin film (silicon oxide film or silicon nitride film) formed by using a focused ion beam such as a silicon focused ion beam having an energy of 10 keV or less exhibits a light transmittance of 90% or more, so that the concave defect of the phase shifter can be satisfactorily corrected. can do. In addition, etching does not cause a decrease in transmittance due to metal ion beam irradiation as in the case,
Yield is greatly improved.

According to a fourth aspect of the present invention, in a phase shift mask using a material in which the main component is composed of the same element as the substrate as the phase shifter, ions different from the element constituting the shifter are implanted into the surface of the substrate. Since the implanted layer is formed and a phase shifter is formed on the upper layer, the substrate and the phase shifter can be made of the same material if the implanted ions on the surface are detected by the secondary detector. In this case, the end point of the etching can be easily detected.

[0033]

Next, embodiments of the present invention will be described in detail with reference to the drawings.

Embodiment 1 In this embodiment, a method of correcting a phase shift mask in which a phase shifter is formed of silicon oxide will be described.

This phase shift mask forms a light shielding pattern 2 made of a Cr film on a quartz substrate 1 and
This is a Levenson-type phase shift mask in which a shifter 3 made of silicon oxide is formed adjacent to a light-shielding body pattern 2. Here, as shown in FIG. 1 (a) or (b), a convex defect 4 is formed. Now, a method for removing this defect will be described. Incidentally, the shifter film thickness t required for phase inversion is represented by an odd multiple of λ / (2n-1), where λ is the wavelength of a light source used for exposure and n is the transmittance of the shifter. Within this ± 5% is acceptable. Here, Kr is formed by a liquid phase growth method using a phase shifter.
An F excimer laser was used as a light source. Since the measured value of n was 1.474, it was set to 261.6 nm. Wavelength 3
When using an i-line of 65 nm, n becomes 1.445, so it is necessary to set it to 410.1 nm. here,
Although the phase shifter is formed by a liquid phase growth method, spin-on-glass (SOG) may be used.

The convex defect 4 remaining in the phase shifter formation stage is removed by using a focused ion beam apparatus while introducing gas to obtain a defect-free mask as shown in FIG. 1 (c). As shown in FIG. 2, this apparatus is provided with a gas introduction nozzle 101,
A sample 103 is placed on a stage 102 installed therein, and an ion beam emitted from an ion source 104 is focused on a defect position of the sample 13 via a magnifying lens 105, a deflector 106, and an objective lens 107. Focused ion beam etching is performed while introducing XeF ₂ gas from a gas introduction concave defect nozzle.

At the time of etching, gas was constantly flowed so that the gas pressure behind the nozzle became 1.0 Torr. The ion source 104 is composed of a Ga liquid metal ion source and has an acceleration voltage of 3
At 0 kV, the beam current was 110 pA. To determine the end point, the shape and height of the convex defect 4 are measured in advance by a laser microscope (not shown), and the defect region is divided into small regions.
This was performed by determining the irradiation amount of the system. The convex defect is 0.8 μm square in each of FIGS. 1 (a) and 1 (b),
The thickness was 261.6 nm. Since the etching rate of the silicon oxide film formed by the liquid phase growth method is 14.5 nm in one scan in FIB assisted etching, 18 scans were performed. Neither the light-shielding film 2 nor the quartz substrate 1 spontaneously etched, and etching occurred only in the beam irradiation area.

In the conventional sputter etching using Ga ion beam alone, the transmittance of the beam irradiation region after removal of the convex defects is reduced to 60% with respect to light having a wavelength of 247 nm. When a transfer experiment was performed using this method, the resist in the beam irradiation area was dissolved. However, the FI of the present invention which irradiates Ga ion beam in the presence of gas
When the B assisted etching is used, the etching rate becomes ten times that in the case of sputter etching, the removal of the Ga-implanted layer is accelerated as compared with the case of sputter etching, the decrease in transmittance due to Ga ions is suppressed, and the transmittance is 99%. % Could be obtained. Also, no defect in the beam irradiation area was transferred onto the wafer. Example 2 In this example, a 5 μm square and a thickness of 7 μm formed on a photomask were used.
A method for correcting a defect of the 0 nm Cr light shield will be described.

As shown in FIG. 3A, this photomask was obtained by forming a light-shielding pattern 2 made of a Cr film on a quartz substrate 1 and having a defect 2 'of the light-shielding pattern formed thereon. Shall be. It is assumed that the surface of the light-shielding body pattern 2 is covered with a 30 nm Cr oxide film as an antireflection film.

For correction, a focused ion beam apparatus as shown in FIG. 2 was used.

First, the surface of the sample was irradiated with a focused ion beam, and a defect position was specified by taking in a SIM image.

Next, when the gas pressure behind the nozzle 101 is 0.2
Sample 1 with XeF ₂ gas from nozzle
A focused ion beam having an acceleration energy of 30 kV and a beam current of 400 pA was applied to the surface of the substrate. At this time, the etching rate of the sample (quartz substrate) 193 is about 1.7 times that in the case of sputter etching. Irradiation of the focused ion beam to the defect area does not have the effect of increasing the etching rate of Cr by XeF ₂ , but the Cr is removed as shown in FIG. 3B by the sputtering phenomenon. Here, the etching end point is detected by the photo channel plate 108.
This is performed by monitoring Cr ions.

Thus, a good mask can be obtained without a decrease in transmittance.

Next, ion-assisted etching of the quartz substrate was performed while changing the amount of the XeF ₂ gas, and the change in transmittance with respect to the etching growth rate was measured. As a result, as shown in FIG. 4, if the ion assisted etching is performed using a small amount of XeF ₂ gas so that the etching yield becomes 1.7 times or more of the sputter etching, the defect of the mask can be removed. It was found that the decrease in transmittance was suppressed. Further, as shown below, the etching rate in the coexistence of gas is reduced to reduce the material dependency of the etching rate, and it is possible to suppress the excavation due to the exposure of the substrate.

FIGS. 5 (a) to 5 (c) show the results of measurement of the change in transmittance when the light shielding member defect is removed by changing the gas pressure behind the nozzle. Here, (a) is a case where only the focused ion beam is irradiated, (b) is a case where the gas pressure behind the nozzle is 1.0 Torr, and (c) is a case where the gas pressure behind the nozzle is 0.2 Torr. This is the case. Here, the transmittance at the g-line of the defect correction region R measured by scanning the slit in the direction indicated by the arrow A in FIG. 6 is shown. These figures 5
As is apparent from the comparison of (a) to (c), the transmittance of the corrected portion was reduced to 83% without XeF ₂ , and the PFR having a thickness of 1.2 μm was actually used as the resist.
I7A with IX500 as a stepper (NA = 0.5,
When an exposure experiment was performed using σ = 0.6), a resist residue was observed in the corrected region. On the other hand, 1.0
When XeF ₂ is present so as to be Torr, the etching rate of the quartz substrate becomes about 11 times that of Cr. Therefore, when the quartz substrate is exposed, the etching proceeds rapidly, and even if the irradiation of the beam is stopped at the end point, the quartz substrate is dug deep, and as shown in FIG. 5B, a dark portion is formed due to the edge effect. Was observed. When an i-line transfer experiment was performed, in this case, a resist residue was observed at a portion corresponding to the edge of the defect. When XeF ₂ is present at 0.2 Torr behind the nozzle, the etching rate is reduced, so that deep substrate digging as in the case of 1.0 Torr does not occur, and as shown in FIG. No dark part due to the edge was observed, and no decrease in transmittance as shown in FIG. 5 (a) was observed.

In an exposure experiment using the quartz substrate thus modified as a mask, no resist residue was observed.

The upper limit of the proliferation rate at which no resist remains at the edge varies depending on the exposure conditions. However, if the proliferation rate is kept at about three times or less, no resist residue attributable to the edge occurs.

Although the defect correction in the case where Cr is used as the light-shielding member has been described, it goes without saying that the present invention is also applicable to the case where MoSi or the like is used. Further, the present invention can be applied to not only a normal photomask but also a phase shift mask. The light-shielding body of the phase shift mask is the same as described above. In addition, according to this method, since the transmittance of the substrate does not decrease, even a convex defect made of a Cr oxide film or a silicon nitride film as a halftone film is used. It is valid.
Further, the present invention can be used for a transparent phase shifter containing silicon oxide as a main component such as a SOG, a quartz substrate, or a convex defect or a concave defect of a silicon oxide formed by a liquid phase growth method.

Further, an X-ray mask made of a film containing a silicon element is effective because the transmittance does not decrease.

As described above, the gas pressure is reduced in order to lower the etching rate. However, this reduction in the gas pressure can simultaneously suppress the influence of the gas on the apparatus and can be used stably for a long period of time.

Embodiment 3 Next, as a third embodiment of the present invention, recovery from damage using XeF ₂ gas will be described.

In this example, as in the case of the second embodiment, a method of correcting a defect of a 5 μm square, 70 nm thick Cr light shield on a photomask will be described.

This photomask has a light-shielding pattern 2 made of a Cr film formed on a quartz substrate 1 in the same manner as shown in FIG.
'Has been formed. It is assumed that the surface of the light-shielding body pattern 2 is covered with a 30 nm Cr oxide film as an antireflection film.

At the time of the correction, first, the sample surface was irradiated with a focused ion beam, and the defect position was specified by taking in the SIM image.

Next, the beam current amount of 400 pA is applied to the correction area.
Of focused ion beams. XeF ₂ gas is introduced from the nozzle to the surface of the sample 103, and the acceleration energy is 30 kV.
Irradiation with a focused ion beam having a beam current of 400 pA was performed to remove defects by a sputtering effect.

The end point was detected by analyzing the secondary ions using the photo channel plate 108 and monitoring the Cr signal.

At this time, the state is the same as that shown in FIG. 5A, and the transmittance decreases to 83% at the g-line due to damage caused by the irradiation of the focused ion beam. In the transfer experiment, a resist remains in the correction area.

Next, the XeF ₂ gas is steadily adjusted so that the gas pressure behind the nozzle 101 becomes 1.0 Torr, the XeF ₂ gas is introduced into the surface of the sample 103 into the chamber, and a focused ion beam having a beam current of 20 pA is introduced. Irradiated to etch the damaged area. Under this condition, the etching yield of the quartz substrate is 8 per Ga, which is 11 times that in the case where no gas coexists, and the etching coexisting with the gas reduces the number of implanted ions that cause a decrease in transmittance. The transmittance can be suppressed, and the transmittance can be restored.

FIG. 19 shows the change in the transmittance with respect to the etching amount in the damaged region of a substrate whose transmittance has decreased due to damage due to ion implantation. From this figure, 10 nm
The transmittance recovers with a slight etching amount, and recovers completely at a maximum of 15 nm. As described above, by performing processing with good controllability while suppressing the beam current amount, the amount of engraving can be suppressed low, and the transmittance of the correction region by the g-line is similar to that shown in FIG. 5 (c). That is, no dark portion due to the edge is formed. For example, as a resist, a PFR-
Using IX500 as a stepper, i7A (NA = 0.5,
When an exposure experiment was performed using σ = 0.6), no resist residue was observed in the corrected area. If the etching amount is about 10 nm, the phase shift amount at the i-line is about 5 degrees at most in the case of a quartz substrate, and this method can be used for a phase shift mask. In addition, this method uses C
Shielding body made of a material are etched by F ₄ and CHF ₃ plasma, it is also available on the mask using the phase shifter, the antireflection film of the deterioration or the mask surface of the pattern shape due to the incident angle dependency of the etching rate Can also be avoided.

Embodiment 4 Next, as a fourth embodiment of the present invention, as shown in FIG. 7A, an embodiment will be described for a concave defect 8 in the case where silicon oxide is deposited to form a shifter. . As in the case where the convex defect is removed, XeF ₂ is steadily flowed so that the gas pressure behind the nozzle becomes 1.0 Torr, and the accelerating voltage is 30 k.
Etching was performed by irradiating V ions and Ga ions with a beam current of 110 pA. The end point was detected by obtaining the beam irradiation amount for each small area from the shape and height of the concave defect measured in advance using the etching rate of the shifter. As shown in FIG. 7B, the digging amount m of the quartz substrate is equal to the thickness t of the shifter (26 due to the KrF excimer laser).
It was set to 1.6 nm. ), The phase of the light passing through the defect area should be the same as the phase of the shifter. Here, m = t.

In this case also, the sputter etching using Ga ion beam alone reduced the transmittance of the beam irradiation area to 60% after the removal of the convex defect, and the beam irradiation area was transferred. According to the method of the present invention using FIB-assisted etching in the presence of gas, the transmittance was hardly reduced to 99%, and there was no transfer in the beam irradiation area.
Embodiment 5 In the case of a phase shift mask in which a shifter is formed by excavating a quartz substrate, the correction can be made in the same manner as in the above embodiment. This example will be described.

As shown in FIG. 8A, when a convex defect 4 is generated in the phase shift mask formed by dug the quartz substrate 1 and used as the shifter 3, a focused ion beam etching using gas is performed. As shown in (b), the etching of the convex defect 4 may be performed. Further, when the concave defect 8 occurs as shown in FIG. 9A, as shown in FIG. 9B, the digging amount k of the defect portion becomes the digging amount t required for inverting the phase.
Etching may be performed so as to be an even multiple of.

Here, XeF ₂ is used as the gas, but CHF ₃ can also be used.

In the above embodiment, the Levenson type phase shift mask has been described. However, the present invention can be similarly applied to a shifter-edge utilizing type and a self-alignment type.

Embodiment 6 Next, as a sixth embodiment of the present invention, a case where the shifter is formed of a resist will be described.

As shown in FIG. 10 (a) or (b), a phase shift mask made of resist is placed on a Levenson-type phase shift mask in which a light shielding film 2 made of Cr and a phase shifter 13 made of resist are arranged on a quartz substrate 1. It is assumed that a convex defect 10 is formed in the mask. Here, the light source was i-line and the resist was PMMA. Therefore, the film thickness t at which the phase is inverted
Is an odd multiple of 370.0 nm, and within ± 5% of this is acceptable. Here, it was set to 370.0 nm. Wavelength 24
251. When using 8 nm KrF excimer laser
It must be an odd multiple of 4 nm. Also in this case, the FIB apparatus shown in FIG. 2 is used to steadily flow O ₂ so that the gas pressure behind the nozzle becomes 1.0 Torr, and irradiate Ga ions at an acceleration voltage of 30 kV and a beam current of 110 pA. Etching was performed to correct as shown in FIG. As in Example 1, the end point was detected by calculating the beam irradiation amount for each small area from the shape and height of the convex defect measured in advance and taking into account the etching rate of the shifter. As shown in FIG. 10A, when the ions remain in the region where the shifter 13 is not necessary, the secondary ions can be monitored by the multi-channel plate 108. This defect had a size of 1.0 μm square and a thickness of 370.0 nm. Since the etching rate of the PMMA resist was 12.0 nm in one scan in FIB assisted etching, 31 scans were performed.
The sputter etching using Ga ion beam alone has a transmittance of 70 for i-line in the beam irradiation region for removing the convex defect.
%, And the beam-irradiated area has been transferred. However, when FIB-assisted etching in the presence of gas is used, the transmittance is slightly reduced to 99%, and the beam-irradiated area is transferred. There was no.

Embodiment 7 Next, as a seventh embodiment of the present invention, a case where the concave defect 11 is corrected when the shifter is formed of a resist will be described.

In this case, similarly, for the concave defect 11 as shown in FIG. 11A, until the etching of the defective portion reaches the interface between the resist 13 and the quartz substrate 1, the convex portion made of the resist described above is used. FIB assist etching was performed under the same conditions as in the case of a defect. The secondary ions are monitored by the multi-channel plate 108, and when the quartz substrate 1 is sufficiently exposed as shown in FIG.
After the irradiation of the film was interrupted and O ₂ was sufficiently drawn by a turbo molecular pump, the quartz substrate was etched by irradiating Ga ions under a XeF ₂ atmosphere under the same conditions as in Example 1. As shown in FIG. 11C, the depth m of the quartz substrate 1 is set such that the phase difference between the light transmitted only through the quartz substrate and the defect portion is one.
This is a thickness required to be 80 degrees, and was 410.1 nm. It is 261.6 nm in the case of a KrF excimer laser. Also in this case, in the conventional sputter etching using the Ga ion beam alone, the transmittance of the beam irradiation area after the correction of the concave defect was reduced to 70% at the i-line, and the beam irradiation area was transferred. However, when FIB assisted etching in the presence of gas was used, the transmittance was only slightly reduced to 99%, and there was no transfer in the beam irradiation area. In the above embodiment, the PMMA film thickness was set to 370.0 nm.
When the A film thickness is set to 1110.0 nm, the concave defect area is set to 740.0 nm by FIB assisted etching in an O ₂ atmosphere.
You only have to dig.

Although O ₂ was used as the gas here,
O ₃ , NO ₂ , NO, and N ₂ can also be used.

Embodiment 8 Next, as an eighth embodiment of the present invention, a case of correcting a convex defect 14 of a halftone type phase shift mask will be described.

Here, silicon is used as the phase shifter, and the phase is 180 g at the g-line as shown in FIG.
By patterning a 58.0 nm-thick Si halftone film (transmittance: 1.7%), which is inverted, a convex defect 14 of a phase shifter made of the Si halftone film is formed. Consider the case. Using the FIB apparatus shown in FIG. 2, Cl ₂ was steadily flowed so that the gas pressure behind the nozzle became 1.0 Torr, Ga ions were accelerated at 30 kV, and beam current was 11
Irradiation was performed at 0 pA to perform etching. The end point was detected when the secondary substrate was monitored by the multi-channel plate 108 and the quartz substrate 1 was exposed. The end point can also be detected by calculating the beam irradiation amount for each small area from the shape and height of the convex defect 14 measured in advance using the etching rate of the shifter. In the sputter etching using Ga ion beam alone, the transmittance of the beam irradiation region after removal of the convex defect is 75 g-lines.
%, And the beam-irradiated area was transferred. However, when FIB-assisted etching in the presence of gas was used, the transmittance was 99%, which was a small decrease. In the transfer experiment, no difference was observed between the beam irradiated area and the beam unirradiated area.

Ninth Embodiment Next, as a ninth embodiment of the present invention, an example in which Ar ions are implanted into the surface of a phase shift mask to easily detect the end point of etching when correcting a defect will be described.

FIG. 13 is a view showing the manufacturing process of this phase shift mask. As shown in FIG.
A light-shielding pattern composed of a two-layer film of Cr22 and CrO23 is formed thereon, and an energy of 20 ke
Ar ions 24 are implanted with V. The range of these ions in the fused quartz is about 20 nm, and Ar ions exist almost near the surface. The dose of the ion implantation is 1 × 10 ¹¹ ions / cm ² . After ion implantation in this way,
The spectral transmittance of the fused quartz substrate was measured, and there was almost no difference from that before the ion implantation, and the decrease in the spectral transmittance due to the ion implantation was negligible.

Next, a resist is applied to the surface on which the ion-implanted layer 26 is formed as described above, and is patterned by performing EB lithography. As shown in FIG. 13B, a resist pattern having a film thickness of 224 nm is formed. Is formed.

Next, using this phase shift mask, the defect of the shifter was corrected by the focused ion beam. FIG.
As shown in FIG. 4 (a), Xe is formed in the concave defect 28 of the shifter 25.
The concave defect 28 is further etched by irradiating a 30 keVGa focused ion beam in the presence of F ₂ . At this time, Ar ions are detected by the secondary ion detector 208. Then, as shown in FIG. 14B, when the surface of the molten substrate 21 is exposed by etching the shifter 27, Ar is detected by the secondary ion detector 208, and the surface of the fused quartz plate can be detected. The etching was terminated by irradiating the Ga focused ion beam for another 30 seconds from the time when Ar was detected in this way (FIG. 14C. Ga focused ion beam).
The etching rate of the fused quartz substrate by the system was determined in advance. The etching depth of this fused quartz substrate is a depth (244 nm) at which the phase is shifted by 180 ° with respect to krF laser light (248 nm) used for pattern transfer.

As described above, the defect generated in the shifter can be corrected with extremely high precision by etching the shifter and the fused quartz substrate.

Although the Levenson-type phase shift mask has been described in the above embodiment, an edge-based phase shift mask in which a transfer pattern is formed only by a shifter can also be used.
The same effect as described above can be obtained by implanting ions and forming a shifter thereon.

Here, etching is performed while introducing a gas using an apparatus as shown in FIG.

Further, in the above embodiment, Ar is used as the ion to be implanted into the surface. However, the present invention is not limited to this, and other ions may be used.

Embodiment 10 Next, as a tenth embodiment of the present invention, a method for depositing a silicon oxide film using a low-energy focused ion beam in a concave defect of a shifter of a phase shift mask will be described. Since correction requires high-precision processing technology,
It is necessary to use a focused ion beam having a beam diameter of 0.1 μm or less.

In the present invention, 10 keV or less, especially 1 keV
In order to obtain a beam diameter of 0.1 μm or less even with an irradiation energy of about V, the low energy shown in FIG.
A focused ion beam device was used. In this apparatus, the ion acceleration voltage is 30 kV, but the potential of the sample stage 213 is set to 29 kV.
By setting to kV, the ion irradiation energy to the sample 212 becomes 1 keV, and a beam diameter of 0.1 μmφ can be obtained. Here, the ion optical column 20
The sample 212 is irradiated with the ion beam 205 selected by the mass separator 203 on the way from the ions emitted from the one ion source 202. Further, the ion beam is converged on the sample 212 by an electrostatic lens or the like in the ion optical column 201. A reference numeral 215 denotes a retarding electrode for shielding the electric field by maintaining the same potential as that of the sample and suppressing the influence of the electric field change due to the irradiation of the beam, and improves the convergence condition of the ion beam. The sample stage 213, the gas introduction system 207, and a charge riser 214 for irradiating electrons to prevent charge-up of the substrate surface are insulated by a glass 211 to make them equal potentials. 216 is a flow control valve.

Here, as shown in FIG.
1. Correction in the case where a concave defect 34 is formed in a Levenson-type phase shift mask in which a light-shielding pattern 32 made of a Cr film is formed on 1 and a shifter 33 made of silicon oxide is formed adjacent to the light-shielding pattern 32 I do. That is, this phase shift mask is placed on the sample stage 213 in the apparatus shown in FIG. 17, and Si (OCH ₃ ) ₄ is supplied from the silicon supply system 208 by the gas supply system 207 and the mixture thereof is supplied from the oxygen supply system 209. Gas 2
10 is sprayed on a phase shift mask serving as a sample 212, and a focused ion beam of Si having an irradiation energy of 1 keV is irradiated thereon. In this case, Si ions are selected by the mass separator 203 using an Au.Si ion source.
Here, the Si focused ion beam 38 is irradiated only on the concave defect 34 to deposit a silicon oxide film 35 inside the concave defect. At this time, the electron beam 37 is emitted from the charge riser 36 to prevent the sample from being charged up.

The transmittance of the thus deposited silicon oxide film having a thickness of 300 nm to the g-line (wavelength 436 nm) was 95%. The refractive index of the film deposited at this time is smaller than that of the shifter, but satisfies the condition required for correction. The transmittance is 90% when using a Si focused ion beam with an irradiation energy of 10 keV, and the transmittance decreases to 60% at 20 keV. This is because as the irradiation energy increases, the damage of the deposited film increases.

As described above, by using the Si ion beam having the irradiation energy of 10 keV or less, it is possible to form a silicon oxide film having a light transmittance of 90% or more required for correcting the shifter. When a silicon nitride film is used as the shifter, the Si ion beam and the Si
When a silicon nitride film formed using a mixed gas of (OCH ₃ ) ₄ and NH ₃ is used for repairing a concave defect, both the light transmittance and the refractive index satisfy the conditions required for the repair.

In the above embodiment, an example in which a silicon oxide film and a silicon nitride film are used for repairing a concave defect has been described. However, it is needless to say that the present invention can be applied to other thin films.

[0086]

As described above, according to the present invention, F
By using FIB assisted etching using IB and gas, it is possible to suppress a decrease in transmittance of the mask substrate due to metal ion beam irradiation and to remove a convex defect of the phase shifter on the mask or to dig a concave defect. Removal can be performed.

According to the second aspect of the present invention, after sputter etching, damage is recovered by focused ion beam etching using XeF _2, and a decrease in transmittance is prevented.

According to the third aspect of the present invention, the phase shift mask can be corrected by satisfactorily embedding a concave defect.

According to the fourth aspect of the present invention, by implanting foreign ions into the substrate surface, the surface level can be easily detected at the time of repair, and the phase shift mask can be repaired with high accuracy.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a defect correcting process according to a first embodiment of the present invention.

FIG. 2 is an explanatory view of a focused ion beam etching apparatus used in an embodiment of the present invention.

FIG. 3 is an explanatory view of a process of correcting a defect according to a second embodiment of the present invention.

FIG. 4 is an explanatory view of a focused ion beam etching apparatus used in an embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a transmittance change after the defect repair of the present invention and a conventional defect repair.

FIG. 6 is an explanatory diagram showing a defect correction area and a scanning direction according to the embodiment of the present invention.

FIG. 7 is an explanatory view of a process of defect correction according to a fourth embodiment of the present invention.

FIG. 8 is an explanatory view of a defect correcting process according to a fifth embodiment of the present invention.

FIG. 9 is an explanatory view of a defect correcting process according to a sixth embodiment of the present invention.

FIG. 10 is an explanatory diagram of a defect correcting process according to a seventh embodiment of the present invention.

FIG. 11 is an explanatory diagram of a defect correcting process according to an eighth embodiment of the present invention.

FIG. 12 is an explanatory diagram of a defect correcting process according to a ninth embodiment of the present invention.

FIG. 13 is a view showing a phase shift mask according to a tenth embodiment of the present invention.

FIG. 14 is an explanatory diagram of a defect correcting step of the phase shift mask according to the tenth embodiment of the present invention.

FIG. 15 is an explanatory view of a focused ion beam film forming apparatus used in an embodiment of the present invention.

FIG. 16 is a diagram showing defect correction according to the eleventh embodiment of the present invention.

FIG. 17 is an explanatory view of a defect repairing process in a conventional example.

FIG. 18 is an explanatory view of a defect repairing process in a conventional example.

FIG. 19 is a diagram showing a relationship between a transmittance and an etching amount.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fused quartz substrate 2 Light-shielding body pattern 3 Shifter 4 Convex defect 10 Defect 100 Container 101 Gas introduction nozzle 102 Stage 103 Sample 104 Ion source 105 Magnifying lens 106 Deflector 107 Objective lens 108 Photomultiplier 109 Charge neutralizer 203 Mass separation Vessel 207 Gas introduction system 208 Silicon supply system 213 Sample table 214 Charger riser 215 Retarding electrode 216 Flow control valve

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-280759 (JP, A) JP-A-4-449 (JP, A) JP-A-4-155339 (JP, A) JP-A-3-28039 105344 (JP, A) JP-A-4-288542 (JP, A)

Claims (3)

(57) [Claims] 1. A light-transmitting substrate, and a phase shifter for forming a predetermined phase difference with respect to light transmitted through a light-shielding film, a halftone film, or a light-transmitting substrate disposed on the light-transmitting substrate. In the method of repairing a mask having the above, while supplying an XeF ₂ gas in such an amount that the etching yield of the light-transmitting substrate due to the coexistence of the focused ion beam and the gas becomes 1.7 times or more that of the focused ion beam alone, A focused ion beam is irradiated on a convex defect on the mask to obtain a FI.
A method of repairing a mask, comprising performing B-assisted etching to remove the convex defect. 2. A light-transmitting substrate, and a phase shifter for forming a predetermined phase difference with respect to light transmitted through the light-shielding film, the halftone film, or the light-transmitting substrate disposed on the light-transmitting substrate. In the method of repairing a mask having a focused ion beam, an XeF ₂ gas is supplied in such an amount that the etching yield of a light-transmitting substrate in the coexistence of a focused ion beam and gas is 1.7 times or more that of a focused ion beam alone, A beam is applied to the concave defect region of the phase shifter, and the concave defect region is FIB-assisted etched to a depth at which the phase of light transmitted through the concave defect region becomes the same as the phase when the concave defect does not occur. A method of correcting a mask, characterized in that: 3. A light-transmitting substrate, and a phase shifter for forming a predetermined phase difference with respect to light transmitted through the light-shielding film, the halftone film, or the light-transmitting substrate disposed on the light-transmitting substrate. An etching step of irradiating a focused region with a focused ion beam to remove a defect, and a method of repairing a mask having a focused ion beam and an etching yield of a light-transmitting substrate caused by coexistence of gas. At least 1.7 times the amount of XeF ₂ gas is supplied, and the focused ion beam is applied to the defect area to perform FIB assisted etching, thereby damaging the surface of the light transmitting substrate formed in the etching step. And a damaged region removing step of removing a region.