JP2002014458A - Halftone phase shift mask and blank - Google Patents

Abstract

(57) [Summary] [PROBLEMS] A region transparent to exposure light on a glass substrate,
Corresponds to shorter exposure wavelength and higher transmittance in blanks with a translucent film layer used for manufacturing a halftone type phase shift mask with a translucent film region with controlled phase and transmittance The present invention provides a halftone type phase shift mask and blank. A content ratio of a silicon element to a main constituent metal element included in a translucent film layer is higher than a stoichiometric ratio of a silicon content ratio which is the highest among the silicide compounds that can be formed by the two elements. It is characterized in that the content ratio is high.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask for exposure transfer used in a photolithography step in a semiconductor manufacturing process and a photomask blank for manufacturing the same, and more particularly to a halftone phase shifter. The present invention relates to a mask or a halftone type phase shift mask blank.

[0002]

2. Description of the Related Art The phase shift method used in recent photomask manufacturing is one of the resolution improving techniques for transferring a pattern onto a Si 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 between the transmitted light becomes 180 degrees, the light intensity at the boundary part is reduced when the transmitted light diffracts and interferes with each other. As a result, the resolution of the transfer pattern is improved. As a result, the resolution of fine patterns and the depth of focus can be greatly improved compared to ordinary photomasks.

[0003] The phase shift method described above is based on IBM's Leve.
Proposed by nson et al., JP-A-58-173744,
The principle is described in JP-B-62-50811, and Levenson type and halftone type are known. In particular, the halftone type phase shift mask makes the edge shape of transmitted light intensity sharp by making the translucent film have the function of phase inversion of transmitted light and the role of light shielding below the resist sensitivity inside the pattern. This has the effect of improving the resolution and the depth of focus characteristics and transferring the mask pattern onto the wafer faithfully.

Among these, Japanese Patent Application No. 9-169143 and Japanese Patent Application No.
Japanese Patent No. 274429 proposes a film material of a halftone type phase shift mask blank (hereinafter referred to as a halftone blank or blank) using a compound of Zr or ZrSi because of its excellent characteristics such as spectral characteristics. . Note that a photomask on which a transfer pattern is formed by enlarging a pattern dimension formed by exposure and transfer to a predetermined magnification is conventionally referred to as a reticle, but in the field of a phase shift mask according to the present invention. This is also called a reticle, and is included in the category defined as a phase shift mask.

[0005]

With the rapid miniaturization of semiconductors in recent years, lithography techniques for achieving the same have been advanced at the same time. In a reduction projection exposure apparatus (stepper) for transferring a mask pattern onto a wafer, the wavelength has been shortened in order to improve the resolution, and Kr has been reduced after i-line.
The transition to ultraviolet light such as F excimer laser and ArF excimer laser has been followed. In recent years, a high-transmittance halftone mask in which the transmittance of light in a shifter portion is increased in order to further enhance the resolution of a pattern transferred onto a wafer has been attracting attention. In the high transmittance halftone mask, the transmittance of the shifter film portion is high, and the intensity of the light transmitted with the phase inverted is increased. For this reason, the phase canceling effect is enhanced, and the resolution at the time of pattern transfer to the Si wafer is improved.

The shift to shorter wavelength light as described above,
In response to increasing the transmittance of the halftone mask,
The shifter material of the conventional photomask blank needs to be reviewed in terms of material in order to cope with these.

[0007] Among the film materials used for halftone masks and blank shifters that have been conventionally proposed, metal (M) is used.
e) and many of the compounds formed of silicon (Si) use a transition metal as the metal, and the composition ratio (molar ratio) of Me and Si in the target for the production thereof
Is mainly composed of a silicide compound having a stoichiometric ratio of Me: Si = 1: 2. Alternatively, a composition ratio based on another stoichiometric ratio is mainly used. For example, a mask or blank shifter film using a compound of zirconium and silicon as a main constituent element, which is proposed because it has excellent spectral characteristics as a mask material and is excellent in various resistances such as a chemical solution and exposure laser light, is also made of Me and Si. 2: 1 ratio (die silicide)
Often, targets are used.

However, when a shifter film is formed from a target having such a typical composition of MeSi, there arises a problem in coping with the transition as described above. This means that it is difficult for the halftone mask and the blank to cope with a shorter exposure wavelength and a higher transmittance. In other words, the transparency of the film constituting the shifter is insufficient, and this is due to the fact that the extinction coefficient k of the optical constant does not decrease.

If a halftone mask is formed from a conventional film, the transmittance in the inspection wavelength range becomes extremely high when a short wavelength or high transmittance halftone mask such as ArF excimer laser exposure is used. As a result, the spectral characteristics are deteriorated, for example, the height is increased, and as a result, problems such as difficulty in inspection are caused. Alternatively, when the phase difference is set to 180 degrees, it becomes completely impossible to obtain a desired transmittance. An object of the present invention is to solve the above problems.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a halftone type phase shift mask and a halftone type phase shift mask blank containing a metal element such as Zr and a Si element. The ratio is determined in consideration of the optical characteristics, film characteristics, and the like.

Specifically, in order to solve the above-mentioned problems, in a halftone type phase shift mask and a semi-transparent film provided on a glass substrate of a mask blank according to the manufacture, It defines a composition ratio that achieves film transparency that cannot be obtained from a metal silicide compound target based on a predetermined elemental stoichiometric ratio, and at the same time, satisfies the refractive index condition required for a halftone mask. That is, the composition ratio of metal and Si in the semi-transparent film of the halftone mask is determined within a certain range, thereby solving the problems listed in the above problem. .

In the present invention, the problem is solved by the above-described method, and the means are listed below.

According to a first aspect of the present invention, there is provided a method of manufacturing a halftone type phase shift mask having a transparent region for exposure light and a translucent film region having a controlled phase and transmittance on a glass substrate. In the blank having the translucent film layer used for the above, the content ratio of the silicon element to the main constituent metal elements contained in the translucent film layer is the most silicon content ratio among the silicide compounds that can be constituted by the two elements. The blank is characterized in that the silicon content ratio is higher than the high stoichiometric ratio.

According to a second aspect of the present invention, there is provided a method for manufacturing a halftone type phase shift mask having a region transparent to exposure light and a translucent film region having a controlled phase and transmittance on a glass substrate. In the blank having the translucent film layer used for the above, the content ratio of the silicon element to the main constituent metal element contained in the translucent film layer is determined by the stoichiometric ratio of the die silicide compound that can be composed of the two elements. Is also a blank characterized by a high silicon content.

According to a third aspect of the present invention, there is provided the blank according to the first or second aspect, wherein a main constituent element of the translucent film layer is composed of a compound of a transition metal and silicon. It is what it was.

According to a fourth aspect of the present invention, in the blank of the third aspect, the constituent elements of the translucent film layer are a transition metal,
A blank comprising silicon and oxygen, wherein the atomic ratio of transition metal to silicon (silicon / transition metal) is in the range of 1.85 to 3.43.

According to a fifth aspect of the present invention, in the blank according to the third aspect, the constituent elements of the translucent film layer include a transition metal, silicon, and oxygen / nitrogen or nitrogen. A blank characterized in that the ratio (silicon / transition metal) is in the range of 1.85 to 7.44.

According to a sixth aspect of the present invention, there is provided the blank according to any one of the first to fifth aspects, wherein the main constituent metal element or transition metal of the translucent layer is zirconium. It is what it was.

According to a seventh aspect of the present invention, there is provided a halftone type phase shift mask manufactured by using the blank according to any one of the first to sixth aspects.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A photomask according to the present invention, in particular, a halftone type phase shift mask and a halftone type phase shift mask blank, are provided with a translucent film shifter patterned on a transparent substrate such as synthetic quartz. However, in order to make this translucent film compatible with a shorter wavelength of the exposure light source and a high transmittance halftone, the element composition ratio of the translucent film is specifically determined.

In determining the composition range, a plurality of shifter films having different compositions were formed by a two-source sputtering method for simultaneously forming films from two different targets on the same substrate. The details are described below. still,
In the experiment, a film containing Zr and Si as main constituent elements is mainly used, but other metals such as Hf, Ti, and Mo other than Zr have the same tendency as long as they are transition metals, so that these metals may be used. It is possible.

In the experiment, an existing ZrSi ₂ sputtering target and a Si sputtering target were simultaneously formed by sputtering, and the composition ratio of the film was changed by controlling the power applied to each sputtering target. XPS analysis was used for the composition analysis of the formed film. Target: Si, ZrSi ₂ film formation _{atmosphere: Ar + O 2 = 40 [} SCCM] ( reactive _{sputtering) O 2 = 1.0~5.0 [SCCM]} (O 2 / (Ar + O 2) * 100 = 2.5% ~12.5 %) Pressure: 0.25 [Pa] Power: DC300 [W] (Total) Si / (Si + ZrSi 2) = 0% (ZrSi 2) ~100% (Si) ··· Power ratio Take Bu Tsu bets - substrate distance: 200 [mm ] Anneal: 250 ℃, 1h (Oven) Quantitative analysis of composition: XPS (Zr + Si + O = 100%) Etching and analysis up to the steady state layer

From the above experimental results, the power ratio to Si (Si
FIG. 1 and Table 1 show the results for (content). Figure 1 is horizontal
The axis is the refractive index, the vertical axis is the extinction coefficient, and the power ratio is changed.
The result of the time is shown. The results are shown in data
Table 1 shows the results. Ar / O _Two= 35/5 SCCM
FIG. 2 and Table 2 show the results of re-testing the conditions. Figure
2, the horizontal axis represents the power ratio, the vertical axis represents the extinction coefficient (Fig. (A)), and
Is the refractive index (Fig. (B)), and when the power ratio is changed
Indicates the result. These results are shown in the table below.
2. From this result, the extinction occurs when the Si content in the film is increased
Because the coefficient k decreases, the transparency of the film increases, and the wavelength becomes shorter.
The transparency to exposure light is increased. Also deteriorated the spectral characteristics
KrF excimer laser or ArF excimer
Shapes a high transmittance halftone mask corresponding to Marazu
Is possible. However, the content of Si
There is a great effect that k decreases with increasing, but at the same time refraction
The value of the ratio n also decreases. Since a decrease in n is accompanied by an increase in film thickness
It is necessary to ensure a certain level of refractive index. Figure 2 above
The optimal range for the halftone mask from the results of
Power ratio (: Si / (Si + ZrSi_Two)) = 0 range to 30% (n: 2.255)
~ 1.781). At power ratios higher than this, n suddenly increases.
It is not suitable because it lowers.

[0024]

[Table 1]

[0025]

[Table 2]

Table 3 shows the results obtained by examining the element composition ratio of the film by XPS. From this result, the range of the element composition ratio that can achieve the object described above can be determined as Si / Zr = 1.85 to 3.43.

[0027]

[Table 3]

When N ₂ , NO, N ₂ O, or the like is used as a gas introduced during sputtering and nitrogen is contained in the film, the value of the refractive index n becomes larger than when nitrogen is not contained. Ar + N ₂ using a ZrSi ₂ target
When the film is formed by reactive sputtering of O, n = 2.8,
In the case of Ar + NO reactive sputtering, n = 2.
6, which is increased as compared with the case where no nitrogen is contained.
For this reason, when the film contains nitrogen, the constraint of n is alleviated and the range of the power ratio described above is expanded,
/Zr=1.85 to 7.44 is optimal. No more S
When the content ratio of i is increased, selectivity with synthetic quartz at the time of etching becomes a problem.

These ranges mean that the silicon content in the content ratio of silicon to the main constituent metal is higher than the stoichiometric ratio of the di-silicide compound that can be formed by the two elements, In the content ratio of the silicon element with respect to the main constituent metal, the same as the case where the silicon content ratio is higher than the stoichiometric ratio in which the silicon content ratio is the highest among the silicide compounds that can be formed by the two elements. is there.

The halftone phase shift mask blank of the present invention can be formed by using reactive sputtering. A magnetron sputtering device is used as a sputtering device, and a ZrSi oxide film is formed on a glass substrate in an atmosphere of Ar and O ₂ gas.
Incidentally, by appropriately changing the introduced gas, it is also possible to obtain a thin film similarly nitrided or fluorinated.

The spatter used for producing the blank of the present invention is
Turing target is silicidized Zr and Si
The target can be the subject. The manufacturing method is
First, Zr and Si are mixed from the powder at a ratio based on the stoichiometric ratio.
After combining, heating and silicide reaction between Zr and Si
Promotes ZrSi and ZrSi_TwoAnd other silicide materials
You. The compound of Zr and Si is also Zr_FiveSi_FourAnd Zr
_ThreeSi_Two, Zr_FiveSi_Three, Zr _TwoSi or the like may be used. After this,
The material is crushed again and Zr or S
Add and mix i-powder slightly to adjust the composition ratio and use it as a target
Press molding. In addition, Zr and Si are converted from a powder state.
Mixing based on the composition ratio, then press working and molding
No particular problem arises with the target mixture.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A halftone type phase shift mask according to the present invention will be described with reference to embodiments. In this embodiment, a target having a composition of ZrSi _{3.0 by} the above-described manufacturing method was used. The film was formed under a gas condition of Ar + O ₂ = 40 SCCM at a power of 300 W DC. Here, optical constants of n = 1.80 and k = 0.021 were obtained when the film was formed under the oxygen partial pressure condition of Ar / O ₂ = 35/5 SCCM. Since this film had a smaller value of k than the conventional shifter film, it had good light transmittance. Also, 1
By superimposing a film having the above-mentioned optical constant of 171 ° and a film having an optical constant of n = 2.25 and k = 0.15 with a thickness of 169 °, the spectral characteristics are good and the position with respect to the ArF laser exposure light is good. A halftone blank with a phase difference of 180 ° and a high transmittance of 20% was obtained.

Next, a resist (positive resist ZEP-7000) is applied to the thus obtained phase shift mask blank, electron beam exposure is performed in a predetermined pattern, and dry etching is performed through a resist process such as development to form a pattern. Then, a halftone type phase shift mask was obtained. Dry etching conditions were as follows.
An RIE device was used as a dry etching device. Etching gas: BCl3 Pressure: 1.0 Pa 12 Pa POWER: 200 W 100 W The etching can be performed even when other chlorine-based gas or fluorine-based gas is used as the etching gas.

[0034]

The present invention is applicable to a halftone type phase shift mask containing metal and silicon at present, and in particular, zirconium (Zr) or silicon (Si) is a main constituent element. However, it is applicable to those mainly composed of a transition metal such as Ti, Hf, and Mo having properties similar to Zr.
Further, the present invention has been made in view of the above-mentioned halftone type phase shift mask, and is an effective means for improving the quality of a mask particularly corresponding to future miniaturization of semiconductors. As the method, the content of Si with respect to the content of metal such as Zr contained in a film provided on a glass substrate is defined.

That is, in a halftone type phase shift mask and a semi-transparent film provided on a glass substrate of a mask blank according to this manufacturing method, a semi-transparent film obtained from a metal silicide compound target based on a predetermined stoichiometric ratio is obtained. It is intended to provide a composition ratio capable of realizing no film transparency and at the same time satisfying the condition of the refractive index required as a halftone mask. Specifically, by setting the content ratio of the silicon element to the metal element contained in the film within the above-described range, the value of the refractive index necessary for the halftone mask is secured, and the extinction coefficient k It is possible to obtain a reduced film. Therefore, by using this film in a single-layer film or a multilayer film forming a halftone mask and a shifter of a blank, it becomes possible to cope with a shorter wavelength of exposure light. In addition, at a specific exposure light wavelength such as an ArF excimer laser or a KrF excimer laser, there has been a limitation on the upper limit of the transmittance that can be produced conventionally due to the problem of the transparency of the film. Accordingly, it is possible to realize a halftone mask having a high transmittance. As a result, by using this high transmittance halftone mask, high resolution can be obtained at the time of pattern transfer to a Si wafer.

As a supplement, it has been confirmed that by increasing the Si content in this range, the resistance to chemicals such as hot sulfuric acid and SC-1 cleaning solution and annealing can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing experimental results according to an example of a halftone phase shift mask and a blank sputtering target of the present invention.

FIGS. 2A and 2B are explanatory diagrams showing another experimental result according to the embodiment of the halftone phase shift mask and the blank sputtering target of the present invention. FIG. 2A is a diagram showing the result of the relationship between the power ratio and the extinction coefficient. FIG. 3B is an explanatory diagram showing the result of the relationship between the power ratio and the refractive index.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koichiro Kanayama 1-5-1, Taito, Taito-ku, Tokyo Letterpress Printing Co., Ltd. (72) Inventor Tsukasa Yamazaki 1-15-1 Taito, Taito-ku, Tokyo Letterpress F-term (reference) in Printing Co., Ltd. 2H095 BB03

Claims (7)

[Claims] 1. A semi-transparent film layer used for manufacturing a half-tone type phase shift mask having a region transparent to exposure light and a semi-transparent film region having a controlled phase and transmittance on a glass substrate. In the blank having, the content ratio of the silicon element to the main constituent metal elements contained in the translucent film layer is higher than the stoichiometric ratio in which the silicon content is the highest among the silicide compounds that can be formed by the two elements,
A blank characterized by a high silicon content. 2. A semi-transparent film layer used for manufacturing a halftone type phase shift mask having a region transparent to exposure light and a semi-transparent film region having a controlled phase and transmittance on a glass substrate. In the blank having, the content ratio of silicon element to the main constituent metal element contained in the translucent film layer is higher than the stoichiometric ratio of the di-silicide compound that these two elements can constitute. A blank characterized by the following. 3. The blank according to claim 1, wherein the main constituent element of the translucent film layer is a compound of a transition metal and silicon. 4. A blank according to claim 3, wherein the constituent elements of the translucent film layer comprise a transition metal, silicon and oxygen,
A blank having an atomic ratio of transition metal to silicon (silicon / transition metal) in the range of 1.85 to 3.43. 5. The blank according to claim 3, wherein the constituent elements of the translucent film layer are a transition metal, silicon, and oxygen / nitrogen or nitrogen, and the atomic ratio of transition metal to silicon (silicon / transition metal) is A blank characterized by being in the range from 1.85 to 7.44. 6. The blank according to claim 1, wherein the main constituent metal element or transition metal of the translucent layer is zirconium. 7. A halftone type phase shift mask manufactured using the blank according to claim 1. Description: