JP2003322955A - Method for producing lithography mask blank, lithography mask and halftone phase shifting mask blank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a lithography mask blank capable of improving electric discharge stability in film deposition and stability of film deposition and capable of suppressing generation of particles. <P>SOLUTION: In the method for producing a lithography mask blank including a step of depositing a thin film comprising at least silicon on a transparent substrate by DC sputtering, a silicon target having ≤0.1 Ω.cm specific resistance is used in the step. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithographic mask for use in transferring a pattern of a semiconductor or the like, a lithographic mask blank as a raw material therefor, and a method for manufacturing the lithographic mask. The present invention relates to a halftone type phase shift mask blank which is a material for a halftone type phase shift mask capable of improving the resolution of the above.

[0002]

2. Description of the Related Art For DRAMs, a mass production system of 256 Mbit has been established at present, and further high integration from Mbit class to Gbit class is going to be made in the future. Along with this, the design rules of integrated circuits have become finer and finer, and it has become a matter of time that a fine pattern having a line width (half pitch) of 0.10 μm or less is required. As one of the means for dealing with the miniaturization of patterns,
The resolution of the pattern has been improved by shortening the wavelength of the exposure light source. As a result, the exposure light source in the current photolithography method is a KrF excimer laser (248 nm), A
The rF excimer laser (193 nm) is mainly used. However, while shortening the exposure wavelength improves resolution, it also reduces the depth of focus, which adversely affects the design of optical systems such as lenses and reduces the stability of the process.

In order to deal with such a problem, the phase shift method has come to be used. In the phase shift method, a phase shift mask is used as a mask for transferring a fine pattern. The phase shift mask is composed of, for example, a phase shifter portion that forms a pattern portion on the mask and a non-pattern portion where the phase shifter portion does not exist. By shifting the phase of light passing through both by 180 °, the pattern boundary The contrast of the transferred image is improved by causing mutual interference of light in the portion. It is known that the phase shift amount φ (rad) of light passing through the phase shifter portion depends on the complex refractive index real part n and the film thickness d of the phase shifter portion, and the relationship of the following mathematical expression (1) is established. φ = 2πd (n−1) / λ (1) where λ is the wavelength of the exposure light. Therefore, phase 1
In order to shift by 80 °, the film thickness d may be set to d = λ / {2 (n-1)} (2). With this phase shift mask, an increase in the depth of focus for achieving the required resolution can be achieved, and it becomes possible to simultaneously improve the resolution and the applicability of the process without changing the exposure wavelength.

Practically, the phase shift mask can be roughly divided into a complete transmission type (Levenson type) phase shift mask and a halftone type phase shift mask depending on the light transmission characteristics of the phase shifter portion forming the mask pattern. The former is a mask whose light transmittance of the phase shifter part is equivalent to that of the non-patterned part (light-transmitting part) and is almost transparent to the exposure wavelength, and is generally effective for line and space transfer. It is said that. On the other hand, in the latter halftone type, the light transmittance of the phase shifter portion (light semi-transmissive portion) is about several percent to several tens of percent of that of the non-pattern portion (light transmissive portion),
It is said to be effective for making contact holes and isolated patterns.

Among the halftone type phase shift masks, the single layer half made of metal, silicon and nitrogen, which has been put into practical use as a single layer type halftone type phase shift mask which has a simple structure and is easy to manufacture. Toned membranes are known.

[0006]

On the other hand, with the miniaturization of LSI patterns, the exposure wavelength used for lithography is KrF excimer laser (wavelength 248 nm), A
The wavelengths are shortened to rF excimer laser (wavelength 193 nm) and F ₂ (fluorine dimer) excimer laser (wavelength 157 nm). It has also been proposed to use soft X-rays (13.4 nm) as the exposure light that provides a resolution of 157 nm or higher. On the other hand, the inspection light used for the pattern inspection of the lithography mask and the defect inspection is also shortened in wavelength to increase the resolution.
m, 257 nm, 198 nm wavelengths are being considered.
In order to cope with the shortening of the exposure wavelength and the inspection wavelength as described above, the optical characteristics of the lithography mask blank are adjusted to the deep ultraviolet region (200 nm to 350 nm) or the vacuum ultraviolet region (50 n).
There is a need to control over m-200 nm). The optical characteristics to be controlled include the transmittance, reflectance, and phase angle of the thin film formed on the blank. These characteristics depend on n (refractive index) and k (extinction coefficient) of the thin film. is doing. In order to control the reflectance and the transmittance of the thin film, the thin film needs to have a certain degree of transparency in the target wavelength region. However, materials having transparency in the deep ultraviolet region or vacuum ultraviolet region are limited to oxides of Si and Al, nitrides, oxynitrides, and fluorides such as CaF ₂ , MgF ₂ , and the like. Used in
Considering the chemical resistance in the cleaning process using an acid and an alkali, the most promising material that can be used for the lithography mask blank is an oxide, nitride, or oxynitride of Si. A thin film made of this material can be formed by sputtering a silicon target in an atmosphere containing a reactive gas containing oxygen and / or nitrogen. On the other hand, in the production of a thin film used for a lithographic mask blank, a DC sputtering method, which has few particles during film formation and high productivity, is generally used. In the DC sputtering method, when the conductivity of the target is small, it becomes difficult to apply a voltage to the target surface (erosion part),
Discharge becomes unstable. Further, arc discharge is likely to occur on the target, and particles are likely to occur. Further, there is a problem that the film forming rate is lowered and the productivity is deteriorated. However, since high-purity Si has low conductivity, discharge stability becomes a problem when silicon is used as a target. In particular, in the lithography mask blanks in recent years, further reduction of particle generation and production stability (reduction of characteristic variation between substrates) are required, and therefore discharge stability during sputtering needs to be controlled.

The present invention has been made in view of the above problems, and improves discharge stability, reduces film formation stability and reduces particle generation when performing DC sputtering using a silicon target, and The purpose is to improve the sex.

[0008]

The present invention has the following configurations. (Structure 1) In a method for manufacturing a lithographic mask blank including a step of forming a thin film containing at least silicon on a transparent substrate by using a DC sputtering method, in the step, the specific resistance is 0.1 Ω · cm or less. A method for manufacturing a lithographic mask blank, which comprises using a silicon target. (Structure 2) B, P, As are added to the silicon target.
And at least one element selected from Sb are contained, The method for manufacturing a lithographic mask blank according to the constitution 1, characterized in that. (Structure 3) The step of forming a thin film containing silicon is a step of forming a thin film containing a silicon compound, and in the step, a reactive gas is added to the sputtering atmosphere. 3. The method for manufacturing a lithographic mask blank according to 1 or 2. (Structure 4) A method of manufacturing a lithographic mask blank, wherein the thin film containing silicon is a thin film having a function of shifting a phase by a predetermined amount with respect to predetermined exposure light. (Structure 5) A lithographic mask blank manufactured by using the method for manufacturing a lithographic mask blank according to any one of Structures 1 to 4. (Structure 6) In a lithography mask blank having a thin film containing at least silicon on a transparent substrate, the thin film containing silicon contains at least one element selected from B, P, As and Sb. Characteristic lithography mask blank. (Structure 7) When B is contained, one kind of element selected from B, P, As, and Sb contained in the silicon-containing thin film, if B is contained, B is 6 × with respect to one silicon atom in the film. P, As and Sb at a ratio of 10 ⁻⁶ to 8 × 10 ⁻³
When one kind of element selected from is contained, it is contained in a ratio of 1.6 × 10 ^{−5 to} 6 × 10 ⁻³ per one silicon atom in the film. Lithography mask blank. (Structure 8) A lithographic mask manufactured using the lithographic mask blank according to any one of Structures 5 to 7. (Structure 9) A halftone phase shift mask blank having a light semitransmissive film having a predetermined phase angle and a predetermined transmittance with respect to a predetermined exposure light on a transparent substrate, the halftone phase shift mask blank comprising: The half-tone phase shift mask blank, wherein the semi-transmissive film contains silicon, oxygen and / or nitrogen, and at least one element selected from B, P, As and Sb. (Structure 10) A halftone phase shift mask manufactured by using the halftone phase shift mask blank according to Structure 9.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
In the method for manufacturing a lithographic mask blank of the present invention, by setting the specific resistance of the Si target to 0.1 Ω · cm or less, it is possible to obtain effects such as suppressing arc discharge that causes generation of particles and improving the film formation rate. That is. Although the specific resistance of the Si target capable of DC discharge is 5 Ω · cm or less, the specific resistance of the Si target is 0.1 Ω · cm as a result of measuring the number of times of oxygen and arc discharge.
It was found that the number of occurrences of arc discharge decreased when the height was less than or equal to cm. Further, the lower the specific resistance of the Si target, the higher the film formation rate at the same DC input power. The power that can be applied to the Si target is the cooling performance, the strength of the backing plate, and the bonding material (usually In).
Since it is limited by the melting point of, the lowering of the specific resistance of the Si target is effective in improving the productivity. S
In order to impart conductivity to the i target, it is possible to include at least one element selected from B, P, As and Sb in the Si target, and the desired concentration can be obtained by adjusting the concentration of the doped element. Conductivity having a specific resistance can be imparted. The specific resistance of the Si target and the concentration of the atoms to be doped have a relationship as shown in Equation 1 and Equation 2. ρN = 5 × 10 ¹⁵ / atomic concentration (Equation 1) In Equation 1, ρN: N type doping material (P, As, S
the resistivity of the silicon target when doping b),
Atomic concentration: The number of atoms of the doping substance contained in Si of 1 cc. ρP = 1.3 × 10 ¹⁶ / atomic concentration (Equation 2) In Equation 2, the resistivity of the silicon target when ρP: P type doping material (B) is doped, atomic concentration = 1
It is the number of atoms of the doping material contained in Si of cc. The sputtered Si target may be polycrystalline or single crystal. Further, as the sputtering gas used in the present invention, an inert gas such as Ar or Xe can be used. In the present invention, the thin film containing silicon is, for example, an EUV (Extreme Ultra Vi) film such as a light shielding film, an antireflection film in a photomask blank, a phase shift film in a phase shift mask blank, or the like.
olet) refers to any thin film in a lithographic mask blank, such as a thin film on a mask blank. Then, a lithography mask can be obtained by patterning a desired thin film in this lithography mask blank into a desired pattern.

In the present invention, the specific resistance is 0.1Ω.
-By using a silicon target of cm or less,
A reactive gas can be added to the sputtering atmosphere to form a thin film containing a silicon compound. As the reactive gas, O ₂ , N ₂ , or a compound gas containing oxygen, nitrogen, or another element such as carbon (for example, NO, NO ₂ ,
_{N 2 O, NH 3, CO} , CO 2, CH 4 , etc.) can be used, by introducing into the sputtering chamber together with the sputtering gas, it is possible to perform reactive sputtering. A thin film containing a silicon compound, such as SiO _x , SiN _x , SiO _x N _y , SiC _x , or Si, is formed by reactive sputtering using a silicon target as described above.
It is possible to form a thin film containing C _X N _Y , SiC _X O _Y , SiC _X O _Y N _Z, or the like.

Particularly, in recent years, the exposure wavelength has been shortened (especially, the exposure wavelength region of 140 nm to 200 nm).
Corresponding to, the SiO _x N _Y single layer film or Si is used as the light semi-transmissive film in the halftone type phase shift mask blank.
O _X N _Y film and, said SiO _x N _Y film and made of a 2-layer structure of an etching stopper film between the substrate has been proposed by the present inventors (Japanese Patent Application No. 2001-261025), the SiO _X The present invention can be used in the formation of N _Y. In this case, the SiO _x N _y film should be adjusted and controlled so that the real part n of the complex index of refraction n is in the range of n ≧ 1.7 and the imaginary part of the complex index of refraction k is in the range of k ≦ 0.450. Is preferred. By doing so, it is advantageous to satisfy the optical characteristics as a halftone type phase shift mask that accompanies the change of exposure light into a single wavelength. For F ₂ excimer laser, the range of k ≦ 0.40 is preferable, and 0.07 ≦
The range of k ≦ 0.35 is more preferable. For ArF excimer laser, the range of 0.10 ≦ k ≦ 0.45 is preferable. For F ₂ excimer laser, the range of n ≧ 2.0 is preferable, and the range of n ≧ 2.2 is more preferable. A
For rF excimer laser, the range of n ≧ 2.0 is preferable, and the range of n ≧ 2.5 is more preferable. In order to obtain the above optical characteristics, the composition range of the constituent elements is 35 to 45 atom% for silicon, 1 to 60 atom% for oxygen,
The nitrogen content is preferably 5 to 60 atom%.
That is, more than 45% silicon or 60 nitrogen
%, The light transmittance of the film becomes insufficient, and conversely, when the nitrogen content is less than 5% or the oxygen content exceeds 60%, the light transmittance of the film is too high, so that the half-tone phase shifter film cannot be obtained. Loss of functionality. If the silicon content is less than 35% or the nitrogen content exceeds 60%, the structure of the film becomes physically and chemically unstable. From the same viewpoint as above,
For the F ₂ excimer laser, the compositional ranges of the constituent elements are preferably 35 to 40 atomic% for silicon, 25 to 60 atomic% for oxygen, and 5 to 35 atomic% for nitrogen. Similarly, for ArF excimer lasers, the composition range of the constituent elements is 38 to 38 for silicon.
It is preferable that the amount of oxygen is 45 atom%, that of oxygen is 1 to 40 atom%, and that of nitrogen is 30 to 60 atom%. In addition to the above composition, trace impurities (metal, carbon, fluorine, etc.)
May be included.

In the present invention, the formed film contains a trace amount of the element doped into the target. As for its content, when B is contained, 1 silicon atom in the film
In the ratio of 6 × 10 ⁻⁶ to 8 × 10 ⁻³ for B,
When one kind of element selected from P, As and Sb is contained, the element is 1.6 per 1 silicon atom in the film.
× contained in 10 ^-5 to 6 × 10 ^-3 or proportion. Therefore, in the case of the SiO _x N _Y film in the example of the halftone type phase shift mask blank shown above, similarly, in addition to the above-described composition, a small amount of the element doped into the target is contained in the formed film. A small amount of the element doped into the target is contained in the formed film. In this case, when B is contained, B in the film is 1 × 10 ¹⁷ to 2 × 10 ²⁰ atms / cc.
And when one kind of element selected from P, As and Sb is contained, the element in the film is 2 × 10 ¹⁶ to 1 × 10
²⁰ atms / cc.

Further, in the above-mentioned example of the halftone type phase shift mask blank, a possible etching stopper is a metal made of one or more alloys of chromium, molybdenum, tantalum, titanium, tungsten, hafnium, zirconium and the like. It is preferable to use a film, or an oxide, nitride, oxynitride, or silicide of these metals or alloys. The exposure light when using such a halftone type phase shift mask is
Exposure wavelength region of 0 nm to 200 nm, specifically, F ₂
Excimer laser wavelength around 157 nm and Ar
A wavelength of 193 nm, which is the wavelength of the F excimer laser, can be used. A high transmittance product in which the halftone phase shifter portion is set to a high transmittance (transmittance 8 to 30%) can also be manufactured. The phase shift amount of the halftone phase shifter film is ideally 180 °, but it is practically 1
It should be within the range of 80 ° ± 5 °. Further, the transmittance is 3 to 20%, preferably 6 to 20%, for the exposure light.
The exposure light reflectance is preferably 30% or less, and more preferably 20% or less in terms of pattern transfer. Further, it is preferable that the inspection light transmittance is 40% or less in order to perform the defect inspection using the transmitted light of the mask, and the inspection light transmittance is 60% or less and the inspection light reflectance is 12% or more. It is preferable for performing a defect inspection using transmitted light and reflected light of the mask. Further, as the transparent substrate in the present invention, a synthetic quartz substrate or the like can be used, and particularly when an F ₂ excimer laser is used as the exposure light, an F-doped synthetic quartz substrate, a calcium fluoride substrate or the like can be used.

[0014]

EXAMPLES The present invention is described in detail below with reference to examples, but the present invention is not limited to the following examples. (Example 1) In this example, a thin film was formed using a DC sputtering apparatus as shown in FIG. A Si target was attached to the sputtering cathode 1. Since the Si target has conductivity, a small amount of boron is doped. The electric resistance of the target is 7 × 10 ⁻⁴ Ω · cm, which corresponds to a boron concentration of about 2 × 10 ²⁰ (atms / cc). Next, after evacuating the vacuum chamber to 2 × 10 ⁻⁵ Pa or less, a quartz substrate is mounted on the substrate holder. A
Mixed gas of r, N ₂ and O ₂ (Ar: N ₂ : O ₂ = 20: 2)
8.7: 1.3) was introduced and the pressure was set to 0.13 Pa. After introducing the gas, open the shutter on the Si target, apply a negative voltage to the Si target, and power 0.35k.
An SiON film was formed on the substrate with W. At this time, Si
In order to reduce the SiON film deposition on the target, the negative voltage applied to the Si target is the pulse generation unit (AE
Company: Sparc-LeV), frequency 20 kHz
Pulse voltage. The pulse generation unit has an arc count function and can measure the number of arc generations during film formation. The number of arcs generated during the formation of the SiON film of Example 1 was zero. The SiON film thickness of Example 1 is 1126
The film forming rate was 33.1 angstrom / min. When the B concentration of the SiON film of Example 1 was measured using SIMS, the B concentration was 3.7 × 10 ¹⁸ (atms / cc), and the ratio of Si in the film was 37 atomic%.

(Embodiment 2) The specific resistance of the Si target is set to 1
X10 ^-2 Ω · cm, SiON was formed in the same manner as in Example 1.
A membrane was prepared. The number of arcs generated during the formation of the SiON film of Example 2 was four. The SiON film thickness of Example 2 is 1038 Å, and the film formation rate is 30.
It was 5 Å / min. Si of Example 2
When the B concentration of the ON film was measured using SIMS, the B concentration was 6.1 × 10 ¹⁹ (atms / cc), and the Si ratio in the film was 38 atomic%.

(Comparative Example 1) The specific resistance of the Si target is set to 1
Ω · cm, and a SiON film was formed in the same manner as in Example 1. The number of arcs generated during the formation of the SiON film of Comparative Example 1 was 127. The SiON film thickness of Comparative Example 1 is 8
It was 89 angstroms, and the film forming rate was 26.1 angstroms / min.

SiON of Examples 1, 2 and Comparative Example 1
When the film was observed in a dark room using a high-intensity halogen lamp of 150 W, almost no particles were observed in Examples 1 and 2, and a large number of particles were observed in the SiON film of Comparative Example 1. .

In the above embodiment, the number of sputtering targets (cathodes) is one, but the number of sputtering targets (cathodes) may be two or more. Also, DC sputtering is D of about 1 to 250 kHz.
Also includes C pulse sputtering.

[0019] In the above embodiment has been described only formation of SiO _X N _Y film, for example, SiO _X on a thin film of a metal such as
Needless to say, a halftone phase shift mask blank having a light-semitransmissive film having a two-layer structure can be manufactured by forming the N _Y film. In addition, SiO _x
The same effect can be obtained regardless of the N _Y film, for example, a silicon thin film, a Si oxide film, a nitride film, or an oxynitride film. Further, it is possible to reduce defects in the mask blank formed on the light-shielding film by using the Si oxide film, the nitride film, and the oxynitride film as the antireflection film, and improve the productivity.

[0020]

According to the present invention, it is possible to improve discharge stability at the time of forming a thin film on a substrate at the time of manufacturing a lithographic mask blank, and thus to reduce film formation stability and generation of particles. You can Further, the film forming rate can be increased and the productivity can be improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a sputtering device used in Examples.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hideaki Mitsui             2-7-5 Nakaochiai, Shinjuku-ku, Tokyo Ho             Within Ya Co., Ltd. F term (reference) 2H095 BB03 BB25 BB31 BC05 BC08

Claims (10)

[Claims] 1. A method of manufacturing a lithographic mask blank, comprising a step of forming a thin film containing at least silicon on a transparent substrate by using a DC sputtering method, wherein the specific resistance in the step is 0.1 Ω · cm or less. A method for manufacturing a lithographic mask blank, comprising using the above silicon target. 2. The silicon target comprises B, P and A
The method for manufacturing a lithographic mask blank according to claim 1, wherein at least one element selected from s and Sb is contained. 3. The step of forming a thin film containing silicon is a step of forming a thin film containing a silicon compound, and in the step, a reactive gas is added to a sputtering atmosphere. The method for manufacturing a lithographic mask blank according to claim 1. 4. A method of manufacturing a lithographic mask blank, wherein the thin film containing silicon is a thin film having a function of shifting a phase by a predetermined amount with respect to predetermined exposure light. 5. A lithographic mask blank manufactured by using the method for manufacturing a lithographic mask blank according to claim 1. 6. A lithographic mask blank having a thin film containing at least silicon on a transparent substrate, wherein the thin film containing silicon is B, P, As or Sb.
A lithographic mask blank containing at least one element selected from the group consisting of: 7. The one element selected from B, P, As and Sb contained in the silicon-containing thin film is B
When B is included, B is added to one silicon atom in the film.
Is 6 × 10 ⁻⁶ to 8 × 10 ⁻³ , P, As and S
When one kind of element selected from b is contained, it is contained at a ratio of 1.6 × 10 ^{−5 to} 6 × 10 ⁻³ per one silicon atom in the film. A lithographic mask blank as described. 8. A lithographic mask manufactured by using the lithographic mask blank according to claim 5. 9. A halftone phase shift mask blank comprising a light-semitransmissive film having a predetermined phase angle and a predetermined transmittance with respect to a predetermined exposure light, which is composed of one layer or two or more layers on a transparent substrate. The half-tone phase shift mask blank, wherein the light-semitransmissive film contains silicon, oxygen and / or nitrogen, and at least one element selected from B, P, As and Sb. 10. A halftone type phase shift mask manufactured by using the halftone type phase shift mask blank according to claim 9.