JP2005077882A - Halftone phase shift mask blank, halftone phase shift mask, method for manufacturing halftone phase shift mask and method for transferring pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a halftone phase shift mask blank and a halftone phase shift mask using ZrSi having superior resistance against chemicals such as alkali, suppressing increase in transmittance in the inspection wavelength region and having sufficient contrast with respect to glass substrate at inspection, and to provide a method of manufacturing the mask and a method of transferring a pattern. <P>SOLUTION: The mask blank is to contain all of a Zr element, a Si element and a metal element, excluding Zr as structural elements of one or more layers in a semitransparent film region. The metal element, excluding Zr has such a property that when an oxide film of the metal element excluding Zr is compared with an oxide film of a Zr element, the extinction coefficient of the oxide film of the metal element is larger than the extinction coefficient of the oxide film of the Zr element. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a photomask for exposure transfer used in a photolithography process in a semiconductor manufacturing process and a photomask blank for manufacturing the photomask, and in particular, a halftone phase shift mask and the same. The present invention relates to a blank for a halftone type phase shift mask for manufacturing the same.

The phase shift method is one of techniques for improving the resolution when transferring a pattern onto a silicon wafer, and has been actively developed. In principle, by providing a phase shift unit in adjacent areas on the mask so that the phase difference of the transmitted light is 180 degrees, the transmitted light is diffracted and interferes with each other, reducing the light intensity at the boundary. As a result, the resolution of the transfer pattern is improved. This has the effect of improving the resolution of the fine pattern and the effect of improving the depth of focus, which are remarkably superior to those of a normal photomask.
As the phase shift method as described above, a Levenson type, a halftone type, and the like are known. In particular, the halftone phase shift mask sharpens the edge shape of transmitted light intensity by giving the semi-transparent film the role of phase inversion of transmitted light and the light shielding property within the pattern below the resist sensitivity. It has the effect of improving the resolution and depth of focus characteristics and faithfully transferring the mask pattern onto the wafer.

Many of the film materials used for the halftone phase shift mask and the blank for the halftone phase shift mask are formed of a compound of metal (Me) and silicon (Si), and a material for forming a metal silicide compound. The majority is using. As a specific metal, a material using a material such as MoSi, TaSi, ZrSi or the like has been proposed.
Incidentally, a photomask in which a pattern for transfer is formed by enlarging a pattern dimension formed by exposure transfer to a predetermined magnification is conventionally referred to as a reticle, but this is also used in the field of the phase shift mask according to the present invention. Is a reticle and is included in the category defined as a photomask.
JP 10-186632 A JP-A-10-73913

  Semiconductor integrated circuits have been miniaturized for the purpose of improving the degree of integration, and accordingly, a stepper (reduced projection exposure apparatus) for transferring a mask pattern onto a wafer and a lithography light source for a scanner are also a KrF excimer laser (wavelength 248 nm), ArF. The excimer laser (wavelength 193 nm) has shifted to a shorter wavelength region, and in the future, the F2 excimer laser (wavelength 157 nm) has shifted to a shorter wavelength.

  On the other hand, since the halftone phase shift mask material for F2 excimer laser exposure corresponds to a wavelength of 157 nm, the amount of oxygen contained in the film is smaller than that of the conventional ArF halftone phase shift film material. The transmittance is secured by increasing the degree of oxidation to increase the degree of oxidation. For this reason, the chemical resistance of oxide films, especially alkali resistance, etc. for MoSi materials has been raised as new issues in the future.

In this respect, ZrSi materials proposed as halftone phase shift mask materials have the advantage that compounds such as ZrO ₂ or ZrSiO ₄ are extremely excellent in chemical resistance such as alkali, and in the future, an oxide film will be almost indispensable. This is a very promising material for the F2 halftone phase shift mask.
However, ZrSi is likely to be highly transmissive with respect to the above-described problem, that is, light in the inspection wavelength range, and it remains difficult to obtain contrast during inspection.

  That is, the tracking of the light source used for the photomask inspection is delayed as compared with the movement of the lithography light source to shorten the wavelength, and light having a longer wavelength than that of the lithography light source is used. Therefore, a halftone phase shift mask manufactured with an appropriate transmittance (about 4 to 20%) at an exposure wavelength such as 157 nm or 193 nm has a high transmittance in an inspection wavelength region such as 257 nm, 266 nm, or 365 nm. As a result, there is a problem that the contrast with the glass substrate is insufficient at the time of inspection.

The present invention has been made to solve such problems, and is a blank for a halftone phase shift mask using a ZrSi material that is extremely excellent in chemical resistance such as alkali. It is an object of the present invention to provide a blank for a halftone phase shift mask and a halftone phase shift mask that do not have high transparency to light and therefore do not have insufficient contrast with a glass substrate during inspection. Is.
It is another object of the present invention to provide a method for manufacturing the halftone phase shift mask and a pattern transfer method.

  The present invention relates to a halftone type phase shift mask used for manufacturing a halftone type phase shift mask provided with a transparent region for exposure light on a glass substrate and a single-layer or multi-layer semitransparent film region with controlled phase and transmittance. A halftone phase shift mask characterized in that a Zr element, a Si element, and a metal element other than Zr are simultaneously contained as constituent elements of at least one layer of the translucent film region in the shift mask blank. Blank.

  Further, according to the present invention, in the blank for halftone phase shift mask according to the above invention, when the metal element other than the Zr is compared with the oxide film of the metal element other than the Zr, the mask inspection apparatus For a halftone phase shift mask characterized in that the extinction coefficient in the wavelength region of the light used in the above is a metal element other than Zr which becomes an oxide film having an extinction coefficient larger than that of the oxide film of Zr element It is blank.

  Further, according to the present invention, in the blank for a halftone phase shift mask according to the present invention, when a metal element other than Zr is compared with a nitride film of a metal element other than Zr, a mask inspection apparatus For a halftone phase shift mask characterized in that it is a metal element other than Zr that becomes a nitride film having an extinction coefficient larger than the extinction coefficient of the nitride film of Zr element. It is blank.

  Further, the present invention provides a blank for a halftone phase shift mask according to the above invention, wherein the metal element other than the Zr is compared with the oxynitride film of the metal element other than the Zr when compared with the oxynitride film of the Zr element. Halftone type characterized by being a metal element other than Zr which becomes an oxynitride film having an extinction coefficient larger than the extinction coefficient of the oxynitride film of Zr element in the wavelength region of light used in the inspection apparatus This is a blank for a phase shift mask.

  In the halftone phase shift mask blank according to the present invention, the metal element other than the Zr is an element selected from the group of Mo, Ta, Nb, W, and Ti. This is a blank for a halftone phase shift mask.

  In the blank for a halftone phase shift mask according to the present invention, the total content of the Zr element and the metal elements other than the Zr is a composition ratio having an atomic ratio of 10% or less. This is a blank for a halftone phase shift mask.

  Further, the present invention is a halftone phase shift mask manufactured using the blank for a halftone phase shift mask according to the above invention.

  Moreover, this invention is manufactured using the blank for halftone type phase shift masks by the said invention, It is a manufacturing method of the halftone type phase shift mask characterized by the above-mentioned.

  The present invention is also a pattern transfer method characterized in that a pattern is formed by exposure transfer by a photolithography method using the halftone phase shift mask according to the above invention.

In the blank for a halftone phase shift mask according to the present invention, since it contains simultaneously a Zr element, a Si element, and a metal element other than Zr as a constituent element of at least one layer of the translucent film region, an alkali or the like Therefore, it is a halftone phase shift mask blank that does not have high transparency with respect to light in the inspection wavelength range and does not have insufficient contrast with the glass substrate during inspection.
In addition, since the blank for the halftone phase shift mask is used, it is extremely excellent in chemical resistance such as alkali and does not have high transparency to light in the inspection wavelength range. This is a halftone phase shift mask and a method of manufacturing the same.

  Hereinafter, the present invention will be described based on embodiments.

The present invention provides a specific third element selected from an extinction coefficient in the inspection wavelength region in order to overcome the problems while utilizing the characteristics of ZrSi in a mask blank such as a blank for a halftone phase shift mask. In other words, it is specifically determined that Zr element, Si element, and three specific metal elements other than Zr are contained simultaneously.
By using this combination of materials, it is possible to obtain a halftone phase shift mask blank that is excellent in chemical resistance and can improve the contrast at the time of inspection.

Hereinafter, specific examples will be described.
[Comparison of extinction coefficients of various metal nitrides in the inspection wavelength range]
Table 1 compares the extinction coefficients of various metal nitride films in the inspection wavelength region. In comparison, extinction coefficients were compared for films containing both metal and Si at the same time as actual halftone phase shift masks instead of single metal oxides or nitrides. In the comparison, the ratio of metal to Si is uniform in each film, so this comparison is a comparison of the extinction coefficients between the metals.

Looking at the extinction coefficient at wavelengths that can be used as inspection light from 193 nm to 365 nm, the nitride film using Mo, Ta, Nb, W, and Ti has a higher extinction coefficient than Zr. . That is, when forming a halftone phase shift mask blank, the transmittance at the inspection wavelength can be suppressed lower than that of the nitride film using Zr, which is advantageous in terms of inspection contrast.
[Comparison of extinction coefficients of various metal oxides in the inspection wavelength range]
Next, Table 2 compares extinction coefficients of various metal oxide films in the inspection wavelength region. As in Table 1, the extinction coefficient is compared for a film that contains both metal and Si at the same time as the actual halftone phase shift mask, rather than an oxide or nitride of a single metal. did. In the comparison, the ratio of metal to Si in each film is the same as in the nitride film.

As shown in Table 2, in the case of oxides, when looking at the extinction coefficients at wavelengths that can be used as inspection light from 193 nm to 365 nm, Mo, Ta, Nb, An oxide film using W or Ti has a higher extinction coefficient.
That is, when forming a halftone phase shift mask blank, the transmittance at the inspection wavelength can be suppressed to be lower than that of the oxide film using Zr, which is advantageous in terms of inspection contrast.
[Comparison of metal / silicon ratio in film]
Table 3 shows the results of examining the characteristics of the etching rate with respect to the metal ratio in the film in a dry etching process performed when patterning is performed on a blank for a halftone phase shift mask and processing as a photomask. Processing was performed under the following conditions.

Etching gas: C ₂ F ₆ = 50 SCCM
・ Pressure: 5mTorr
・ Resist: ZEP700
・ Applied power: RF = 150W, IPC300W

From the results shown in Table 3, there is a large difference in the etch rate when the metal ratio is 10% and 20%, and when it is 20%, the workability is extremely impaired. Therefore, the total content of Zr and metal elements other than Zr contained in at least one layer of the semitransparent film region in the blank for halftone phase shift mask is a composition ratio of 10% or less in atomic ratio. It is preferable.
[Fabrication of halftone phase shift mask]
In Example 1, a film containing Mo as a metal element other than Zr, Si, and Zr is examined for an extinction coefficient in an inspection wavelength region, and a blank for a halftone phase shift mask and a halftone phase shift A mask was prepared.

The halftone phase shift mask blank was formed by reactive sputtering. A magnetron sputtering apparatus is used as the sputtering apparatus. The oxide film is formed on the glass substrate in an atmosphere of Ar and O ₂ gas, and the nitride film is formed in an atmosphere of Ar and N ₂ .
It is also possible to obtain a thin film that has been similarly fluorinated by appropriately changing the introduced gas.

  Film formation was performed using sintered targets 1 to 4 containing Zr, Si, and Mo in the proportions shown in Table 4 as targets. Table 5 shows the results. It is confirmed that the extinction coefficient in the inspection wavelength region after the wavelength of 193 nm is increased by the inclusion of Mo.

In Example 1, a half-tone type phase shift mask blank was produced using a two-layer film. As the elemental composition ratio of the shifter film provided on the synthetic quartz substrate, the conditions of the target 4 in Table 4 were used, a nitride film was used as the lower layer film, and an oxide film was used as the upper layer film. Here, the nitrogen gas conditions for forming the nitride film and the oxygen gas conditions for forming the oxide film are reactive when compared with a blank for a halftone phase shift mask configured with other composition ratios. In order to eliminate the influence of the difference between the two, each reactive gas was deposited under a saturated flow rate condition.

・ Upper layer film thickness: 534 [Å]
・ Under film thickness: 260 [mm]
-Phase difference: 180 degrees, transmittance at an exposure wavelength of 157 nm: 6%
As a result, a halftone phase shift mask blank having excellent spectral characteristics and resistance to chemicals was obtained.

  Next, a pattern was formed on the thus obtained blank for halftone phase shift photomask by performing a resist process such as resist coating, exposure and development, and dry etching. The dry etching conditions are as follows. An ICP dry etching apparatus was used as the dry etching apparatus.

Etching gas: C ₂ F ₆ = 50 SCCM
・ Pressure: 5mTorr
・ Applied power: RF = 150W, IPC300W
It should be noted that the etching gas can be etched even when other gases are used.

  In the first embodiment, the halftone phase shift mask blank in the case of containing a metal having a higher extinction coefficient in the inspection wavelength region than Zr has been described, but the halftone phase shift without containing any metal other than Zr. A mask blank was produced as Comparative Example 1, and a comparison was made below. The manufacturing method is the same as in the case of Example 1 above.

・ Upper layer film thickness: 567 [Å]
・ Under film thickness: 247 [Å]
Table 6 compares the transmittance at each wavelength in Example 1 with the transmittance at each wavelength in Example 2. As shown in Table 6, in Example 1, a decrease in transmittance is observed.

From the above results, it is confirmed that the spectral transmittance at the inspection wavelength is lowered in the halftone phase shift photomask blank according to the present invention. Moreover, the fall of the tolerance which becomes a problem with respect to a washing | cleaning liquid was not recognized.

Claims (9)

  Blank for halftone phase shift mask used for the production of a halftone phase shift mask having a transparent region for exposure light on a glass substrate and a single layer or multilayer semitransparent film region with controlled phase and transmittance. A blank for a halftone type phase shift mask, wherein a Zr element, a Si element, and a metal element other than Zr are simultaneously contained as constituent elements of at least one layer in the semitransparent film region.   When the metal element other than Zr is compared with the oxide film of the metal element other than Zr, the extinction coefficient in the wavelength region of the light used in the mask inspection apparatus has an extinction coefficient of the oxide film of the Zr element. 2. The blank for a halftone phase shift mask according to claim 1, wherein the blank is a metal element other than Zr which becomes an oxide film having an extinction coefficient larger than the extinction coefficient.   When the nitride film of the metal element other than Zr is compared with the nitride film of the Zr element when the nitride film of the metal element other than the Zr is compared with the nitride film of the Zr element, the extinction coefficient in the wavelength region of light used in the mask inspection apparatus is The blank for a halftone phase shift mask according to claim 1, wherein the blank is a metal element other than Zr which becomes a nitride film having an extinction coefficient larger than the extinction coefficient.   When the metal element other than Zr is compared with the oxynitride film of the metal element other than Zr and the oxynitride film of the Zr element, the extinction coefficient in the wavelength region of light used in the mask inspection apparatus is oxynitride of the Zr element 2. The blank for a halftone phase shift mask according to claim 1, wherein the blank is a metal element other than Zr which becomes an oxynitride film having an extinction coefficient larger than that of the film.   The metal element other than Zr is an element selected from the group of Mo, Ta, Nb, W, and Ti, for a halftone phase shift mask according to claim 1, blank.   6. The halftone phase according to claim 1, wherein the total content of the Zr element and the metal element other than the Zr is a composition ratio having an atomic ratio of 10% or less. Blank for shift mask.   A halftone phase shift mask manufactured using the blank for halftone phase shift mask according to any one of claims 1 to 6.   It manufactures using the blank for halftone phase shift masks of any one of Claims 1-6, The manufacturing method of the halftone phase shift mask characterized by the above-mentioned.   A pattern transfer method using the halftone phase shift mask according to claim 7 to perform pattern formation by exposure transfer by a photolithography method.