JPH09244219A - Phase shift mask blank and phase shift mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a halftone type halftone phase shift mask blank with which the prevention of electrification by the charge accumulation and static electricity at the time of electron beam plotting is made possible by simple film constitution and a halftone type phase shift mask made therefrom. SOLUTION: This halftone type phase shift mask blank (a) has a light translucent film 2a on a transparent substrate 1. This light translucent film 2a consists of a film consisting of a transition metal and silicon as well as oxygen and/or nitrogen as its main constituting elements and the silicon is incorporated in the form of at least silicone oxide and/or silicon nitride. This halftone type phase shift mask (b) is composed by forming the mask patterns consisting of light transparent parts 3 and light translucent parts 2 on the light translucent film 2a of the halftone type phase shift mask blank (a).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase shift mask blank, a phase shift mask and a lithographic method using the same. More specifically, the present invention relates to a halftone type phase shift mask blank capable of preventing charge accumulation and electrostatic charge due to static electricity during electron beam writing on a resist when forming a mask pattern with a simple film structure, and the phase shift. The present invention relates to a halftone type phase shift mask using a mask blank as a material, and a lithography method for performing pattern transfer using the phase shift mask.

[0002]

2. Description of the Related Art In the manufacture of semiconductor LSIs, a phase shift mask is used as one of photomasks for transferring a fine pattern. Among these phase shift masks, a halftone type phase shift mask is known as one which is particularly suitable for transferring a single hole, dot, or isolated pattern such as a line or space.

[0003] This halftone type phase shift mask is
A mask pattern formed on the surface of the transparent substrate is composed of a light transmitting portion that transmits light having an intensity substantially contributing to exposure and a light translucent portion that transmits light having an intensity substantially not contributing to exposure. And, by making the phase of the light passing through the light transmitting portion different from the phase of the light passing through the light semi-transmitting portion, the light passing near the boundary between the light transmitting portion and the light semi-transmitting portion is reduced. The contrast of the boundary portion can be maintained well by canceling each other out. For example, Japanese Patent Application Laid-Open No. 5-127361 discloses that the phase difference is 18
A halftone type phase shift mask with 0 ° is disclosed.

In the halftone type phase shift mask described in this publication, the light semi-transmissive film constituting the light semi-transmissive portion on the transparent substrate is made of CrO _x , CrN _x , CrO _x N _y , CrO _x.
x N _y C _z-like film such as, and a layer of film made of uniform material composition.

A halftone type phase shift mask having a light semi-transmissive portion formed of a light semi-transmissive film made of a single film as described above has a light transmissive portion which mainly has a transmittance which controls a phase angle. Compared with a halftone type phase shift mask having a multilayer structure composed of a plurality of types of a high layer (for example, SOG) and a low transmittance layer (for example, chromium) for mainly controlling light semi-transmission, the number of manufacturing steps is reduced. It has advantages such as simplification and reduction of the defect occurrence rate.

This CrO _x , CrN _x , CrO _x N _y or C
Regarding the method of forming the light semitransmissive film made of rO _x N _y C _z ,
The above publication discloses a method of depositing an oxide, nitride, oxynitride, or oxynitride carbide of chromium on a transparent substrate by putting a gas such as oxygen or nitrogen into a deposition atmosphere using chromium as a sputtering target, that is, A method using reactive sputtering is disclosed.

[0007]

However, the C formed by the above-described conventional method (reactive sputtering method) is not suitable.
The light semi-transmissive film made of rO _x , CrN _x , CrO _x N _y, or CrO _x N _y C _z has a property of transmitting light that does not contribute to exposure, that is, the transmittance for exposure light is 4 to
Those satisfying both the requirement of 20% and the requirement of the light semi-transmissive portion to provide a predetermined phase difference have poor conductivity.
For this reason, in drawing an electron beam on a resist for patterning the light semi-transmissive film, the injected electrons are charged in the resist, resulting in a problem that an accurate pattern cannot be formed.

[0008] Further, the lack of conductivity leads to the electrification of static electricity, so that there is a problem that dust is easily adsorbed during the manufacturing process and use of the mask. Therefore, in order to prevent the charging phenomenon, it is necessary to provide a conductive layer that conducts and diffuses electricity on, for example, a transparent substrate, which has a drawback that the number of manufacturing steps is increased.

Furthermore, when a conductive layer is formed between the transparent substrate and the light semi-transmissive film, it must be transparent to exposure light of short wavelength, and in particular, a high resolution pattern in recent years is required. With respect to the shortening of the wavelength of the exposure light associated with this, there is also a problem that a conductive layer material that is transparent to such exposure light must be newly developed.

The present invention has been made under the above-mentioned background, and is a halftone type phase shift mask blank capable of preventing charge accumulation and static charge at the time of electron beam writing with a simple film structure. It is an object of the present invention to provide a halftone type phase shift mask using a phase shift mask blank as a material, and a lithography method for performing pattern transfer using this phase shift mask.

[0011]

Means for Solving the Problems As a result of intensive studies by the present inventors, a halftone type phase shift mask blank capable of preventing charge accumulation at the time of electron beam writing and electrostatic charge due to static electricity with a simple film structure is obtained. , A halftone type having a light-semitransmissive film containing a transition metal, silicon, oxygen and / or nitrogen as main components on a transparent substrate, and containing silicon in the form of at least silicon oxide and / or silicon nitride It was found that the phase shift mask blank has the above-mentioned preferable properties and that the halftone type phase shift mask having a desired mask pattern can be obtained by subjecting this phase shift mask blank to a patterning process according to a conventional method. The present invention has been completed based on this finding.

That is, the present invention (1) has a light-semitransmissive film on a transparent substrate, and the light-semitransmissive film has a transition metal, silicon, oxygen and / or nitrogen as main constituent elements. And a silicon-containing semitransparent film containing at least silicon in the form of silicon oxide and / or silicon nitride. (2) The above phase-shift mask blank. The half-tone type which is characterized in that a mask pattern composed of a light-transmitting portion and a light-semitransmitting portion is formed by subjecting the light-semitransmitting film in Provided is a phase shift mask, and (3) a lithographic method characterized by performing pattern transfer using the halftone type phase shift mask. Than it is.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The halftone type phase shift mask blank of the present invention has a light-semitransmissive film on a transparent substrate, and there is no particular limitation on the material of the transparent substrate. Conventional mask blanks such as soda lime glass such as soda lime glass or white crown; low expansion glass such as borosilicate glass, alkali-free glass, aluminosilicate glass; quartz glass such as synthetic quartz, or A plastic film such as a polyester film is used, but as a substrate material for an LSI or LCD mask,
Soda-lime glass and quartz glass are preferred.

On the other hand, the light semi-transmissive film provided on the transparent substrate has a property of transmitting light of an intensity not substantially contributing to exposure and a property of shifting the phase of exposure light by a predetermined amount, and a mask. It has a conductivity higher than an electric charge is not charged when drawing an electron beam on a resist when forming a pattern. In the present invention, as the light-semitransmissive film having such characteristics, a film containing a transition metal, silicon, oxygen and / or nitrogen as main constituent elements is used.

The transition metal is not particularly limited,
It is preferable to appropriately select from metal elements belonging to groups IVB, VB and VIB of the periodic table. Examples of such transition metals include titanium, zirconium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, and the like. Among these, titanium,
Tantalum, chromium, molybdenum, and tungsten are preferable in terms of performance. These transition metals may be used alone or in combination of two or more.

The method for forming the light semi-transmissive film in the halftone type phase shift mask blank of the present invention is not particularly limited, and a conventionally known method such as a sputtering method,
The method can be appropriately selected from the EB vapor deposition method, the ion plating method, and the like using a tablet in which the composition of the transition metal and silicon is adjusted, and among these, the sputtering method is particularly preferable. For example, a target containing the transition metal and silicon is sputtered in a sputtering gas containing at least one selected from oxygen, nitrogen and nitrogen oxides to form a light semi-transmissive film on a transparent substrate. As a result, the halftone phase shift mask blank of the present invention can be manufactured. Here, as the sputtering gas, a mixed gas of oxygen, nitrogen, a nitrogen oxide gas and argon or another inert gas is used. The oxygen gas and the nitrogen gas are for introducing oxygen (O) and nitrogen (N) into the film, respectively, while the nitrogen oxide gas is for introducing oxygen (O) and nitrogen (N) into the film. Is for introducing. The nitrogen oxide gas is not particularly limited, but nitric oxide (NO) gas and nitrogen dioxide gas (NO ₂ ) are preferable.

Further, in order to control the permeability and conductivity of the film, when only oxygen gas is used as the reaction gas,
It is desirable to introduce oxygen gas in an amount of about 15 to 60% of the total sputter gas flow rate, and when only nitrogen gas is used as a reaction gas, the sputter gas total flow rate is 15 to 100%.
It is desirable to introduce nitrogen gas of about%. Further, when oxygen gas and nitrogen gas are used as the reaction gas, it is desirable to introduce oxygen gas of about 15 to 55% and nitrogen gas of about 15 to 80% of the total flow rate of the sputtering gas.
The method of introducing N or O into the film is not limited to the use of the above oxygen gas, nitrogen gas, or nitrogen oxide gas, and when the above effects can be expected, other oxygen compounds or Nitrogen compounds (eg NH ₃ gas) may also be used. Moreover, there is no particular limitation as to the sputtering method,
A conventionally known method such as a DC sputtering method or an RF magnetron sputtering method is preferably used. Note that substrate heating during sputtering, annealing after film formation, and the like may be performed as appropriate. Further, the target composition has an atomic ratio of transition metal to silicon of 30:
It is preferably in the range of 1 to 1:20.

The film thickness d of the light-semitransmissive film thus formed is determined by the following equation (I), where φ is the phase shift amount, n is the refractive index, and λ is the wavelength of the exposure light. .

D = (φ / 360) × {λ / (n−1)} (1) In the equation (1), the phase shift amount φ is ideally 180 °, but it is practical. Phase shift amount is 160 °
It is sufficient that ≦ φ ≦ 200 °.

In the halftone type phase shift mask of the present invention, the light semitransmissive film in the halftone type phase shift mask blank obtained as described above is subjected to a patterning process for removing a part thereof in accordance with a predetermined pattern. It can be obtained by forming a mask pattern including a light transmitting portion and a light semi-transmitting portion.

FIG. 1 is a diagram showing a halftone type phase shift mask blank and a halftone type phase shift mask of the present invention. More specifically, FIG. 1A shows an example of a halftone type phase shift mask blank. FIG. 1B is a cross-sectional view of the halftone phase shift mask 1
It is sectional drawing of an example.

As shown in FIG. 1A, the halftone type phase shift mask blank has a light semitransmissive film 2a formed on a transparent substrate 1. Further, as shown in FIG. 1 (b), the halftone type phase shift mask
The light semi-transmissive film 2a of the halftone type phase shift mask blank shown in FIG. 1A is subjected to a patterning process for removing a part of the light semi-transmissive film 2a according to a predetermined pattern. Is formed.

In the light-semitransmissive film in the phase shift mask blank of the present invention, the silicon in the film has at least a form of silicon oxide and / or silicon nitride. Usually, a transition metal element and a silicon element are contained. The light transmittance with respect to the exposure light depends on the sensitivity of the resist used for the light transfer of the mask pattern, but is generally preferably 4 to 20%, particularly preferably 5 to 15%. this is,
If the light transmittance is less than 4%, in FIG. 1B, the offset effect due to the phase shift between the light passing through the boundary between the light semi-transmissive portion 2 and the light transmissive portion 3 cannot be sufficiently obtained, and , 20%
This is because the resist may be exposed to light even if it passes through the light semi-transmissive portion 2 when the value exceeds.
The light transmissivity per unit film thickness of the light semi-transmissive film 2a and the light semi-transmissive part 2 can be selected by selecting the content rates of the transition metal, silicon, oxygen and / or nitrogen.

As the halftone type phase shift mask blank of the present invention, it is preferable that the light semitransmissive film has a transmittance in the visible region of 30 to 70%.
By having such a transmittance in the visible range,
It is not necessary to form a new film for forming an alignment mark for mask alignment.

Further, in the halftone type phase shift mask blank of the present invention, the sheet resistance of the light semi-transmissive film is preferably 5 × 10 ⁷ Ω / □ or less. The reason is that if the sheet resistance exceeds 5 × 10 ⁷ Ω / □, it is difficult to sufficiently conduct electrons injected by electron beam irradiation.
In order to obtain this conductivity, it can be selected by selecting the content rates of oxygen (O) and nitrogen (N). In this case, as described above, increasing the content of oxygen (O) or nitrogen (N) increases the light transmittance, but on the other hand, tends to decrease the conductivity. Further, characteristics such as a refractive index, a reflectance and an absorption coefficient can be suitably selected depending on the composition of transition metal, Si, O and N.

In the halftone type phase shift mask blank of the present invention, the ratio of each constituent element in the light semi-transmissive film may be appropriately selected so that the light semi-transmissive film has the characteristics described above, and there is no particular limitation. But in general,
The ratio of transition metal: silicon: oxygen and / or nitrogen is selected in the atomic ratio range of 10 to 55%: 15 to 80%: 70% or less.

Next, a preferred example of the method of manufacturing the halftone type phase shift mask of the present invention will be described with reference to FIG.

FIG. 2 is an explanatory view of an example of the manufacturing process of the halftone type phase shift mask of the present invention. First, the light semitransmissive film 2a is formed on the surface of the transparent substrate 1 as described above. The obtained phase shift mask blank is prepared [Fig. 2
(A)]. Next, an electron beam resist film having a thickness of about 4000 to 6000 Å is formed on the light semi-transmissive film 2a of the phase shift mask blank [(FIG.
(See (b)], and after irradiating an electron beam according to a predetermined pattern, the resist is developed to form a resist pattern 4 [see FIG. 2 (c)]. Next, using the resist pattern 4 as a mask, After the light semi-transmissive film 2a is dry-etched [see FIG. 2 (d)], the residual resist pattern 4 is peeled off to obtain the half-tone phase of the present invention having the light semi-transmissive portion 2a and the light transmissive portion 3. A shift mask is obtained [(see FIG. 2E)].

The halftone phase shift mask of the present invention obtained in this manner, as shown in the illustration of FIG. 3, when the exposure light L ₀ is emitted, the exposure light L _0,
It breaks up into a light L ₂ reaching the light semi-transmitting portion 2 passes through the through the light L ₁ and the light transmitting portion 3 to reach the transfer object (not shown) similarly the transfer member. In this case, the intensity of the light L ₁ that has passed through the light semi-transmissive portion 2 is weak so that it does not substantially contribute to the exposure of the resist. On the other hand, the light L _{2 that} has passed through the light transmitting portion 3 is a strong light that substantially contributes to the exposure. Therefore, this enables pattern exposure. At this time, the light passing through the boundary between the light semi-transmissive portion 2 and the light transmissive portion 3 wraps around to the other region due to the diffraction phenomenon. In the vicinity, the light cancels each other, so that the substantial light intensity is attenuated. This makes the boundaries very clear and improves the resolution.

The present invention also provides a lithographic method for transferring a pattern using the halftone type phase shift mask.

The lithography method is not particularly limited as long as it is a method using the halftone type phase shift mask of the present invention as a mask, and a method conventionally used in the manufacture of LSI or the like can be used.

For example, after a resist layer is provided on a substrate having a layer to be processed formed on it, ultraviolet rays and g are applied to the resist layer through the halftone type phase shift mask of the present invention.
Line, i-line, deep UV, excimer laser light, X-ray, etc. are selectively irradiated. Then, the resist layer of an unnecessary portion in the developing step is removed, after forming a resist pattern on the substrate, the layer to be processed is subjected to etching treatment using this resist pattern as a mask, and then the resist pattern is removed, A pattern faithful to the mask pattern can be formed on the substrate.

[0033]

The halftone phase shift mask blank of the present invention described above has a light-semitransmissive film for forming a light-semitransmissive portion, and this light-semitransmissive film contains a transition metal, silicon, oxygen and / or It is composed of a film containing nitrogen as a main component, and this film has a property of transmitting light having an intensity that does not substantially contribute to exposure and a property of shifting a phase of exposure light by a predetermined amount, Since it has a conductivity that is not higher than the amount of charge that is not charged during electron beam writing, and also has a wide range of controllability of conductivity, it has a simple film structure that allows it to accumulate charge and prevent static electricity during electron beam writing. Patterning with high reproducibility is possible while preventing the influence of electrification.

Further, a suitable phase shift mask can be obtained by using the halftone type phase shift mask blank of the present invention.

[0035]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 (1) Manufacture of Halftone Phase Shift Mask Blank The halftone phase shift mask blank shown in FIG. 1A was manufactured as follows.

A quartz glass substrate whose main surface is mirror-polished is used as the transparent substrate 1, and a target composition ratio of tungsten (W) to silicon (Si) is 1: 1 on the substrate, and a sputtering gas is used. A half-tone phase shift mask blank was manufactured by forming an optical semi-transmissive film having a film thickness of 1240 Å by RF magnetron sputtering under the condition that the composition was 1: 1 by volume ratio of argon and oxygen. The formed light-semitransmissive film has a refractive index n of 2.0 and a transmittance of 8.0% when λ = 248 nm.
The atomic ratio of W: Si: O was 26:29:45, and the sheet resistance was less than 3.0 × 10 ⁶ Ω / □.

FIG. 4 is a diagram showing the dependence of the light transmittance on the wavelength of the light semi-transmissive film of the halftone type phase shift mask blank thus obtained.

With respect to this light-semitransmissive film, the distribution of atoms in the depth direction from the film surface was determined by ESCA (Elect
ron Spectroscopy for Chemical Analysis). The result is shown in FIG. In FIG. 5, the X axis is the binding energy (BINDING ENERGY).
(EV), the Y axis represents the amount corresponding to the number of atoms, and the Z axis represents the cycle number (CYCLES) (corresponding to the depth from the film surface, the smaller the number, the closer to the initial film surface). From this figure, it can be seen that the film contains SiO ₂ .

(2) Manufacture of halftone type phase shift mask Using the halftone type phase shift mask blank obtained in (1) above, a halftone type phase shift mask was manufactured according to the process chart of FIG.

First, an electron beam resist film 4a (manufactured by Tosoh Corporation: CM) is formed on the light semitransmissive film 2a of the phase shift mask blank.
S-M8) was formed to a thickness of 6000 angstroms (see FIG. 2B), irradiated with an electron beam according to a predetermined pattern, and then subjected to a resist developing process to form a resist pattern 4 (FIG. 2). (C)).

Next, using the resist pattern 4 as a mask, the light semi-transmissive film 2a is subjected to a reactive dry etching method (RI
E) Dry etching was performed using a parallel plate type dry etching apparatus (see FIG. 2D).

After the dry etching treatment, the residual resist pattern 4 was peeled off to obtain a phase shift mask having a light semi-transmissive portion 2 and a light transmissive portion 3 (FIG. 2 (e)).
reference).

According to this embodiment, the light-semitransmissive film 2a in the phase shift mask blank is 3.0 × as described above.
Since it has a sheet resistance of less than 10 ⁶ Ω / □, it is possible to sufficiently prevent the electrons hit by the electron beam irradiation for forming the resist pattern in the production of the phase shift mask blank from being charged.

Further, the light semi-transmissive film 2a in the phase shift mask blank of this embodiment has an etching selection ratio (etching rate of the light semi-transmissive film / etching rate of the transparent substrate) of 3 or more with respect to the transparent substrate 1. By performing the etching under appropriate conditions, the light semi-transmissive film 2a could be etched with almost no damage to the transparent substrate 1.

Further, in this embodiment, the light semi-transmissive film 2a is used.
The (light-semitransmissive portion 2) has sufficient adhesiveness with the transparent substrate 1, and can withstand ultrasonic cleaning and scrub cleaning performed in a cleaning process for producing a normal photomask.
Further, since it is excellent in acid resistance, it can sufficiently withstand washing with hot concentrated sulfuric acid or washing with a mixed solution of hydrogen peroxide and concentrated sulfuric acid performed in the washing step.

Further, as shown in FIG. 4, the transmittance in the visible region is about 42%, and a film for forming a new alignment mark for alignment (alignment) of the mask as in the first embodiment. Need not be formed.

When the phase shift mask of this embodiment was used, the same depth of focus as that of the conventional phase shift mask was obtained.

(Example 2) Regarding the sample of Example 1 36
The refractive index at 5 nm was measured, a light-semitransmissive film was formed at a film thickness that satisfied the conditions as a halftone type phase shift mask blank, and the transmittance thereof was measured. It was confirmed that it can be used as a halftone shift mask blank and a halftone phase shift mask even at a wavelength of 365 nm.

(Embodiment 3) Of the gas introduction conditions in Embodiment 1, the amount of oxygen gas introduced is 5% to 10% of the total amount, respectively.
A semi-transmissive film was prepared by reducing the film thickness to a certain degree, and the transmittance was measured at a film thickness satisfying the conditions as a halftone type phase shift mask blank from the refractive index at 436 nm. It was confirmed that it can be used as a halftone type shift mask and a halftone type phase shift mask blank even at a wavelength of 436 nm while satisfying sufficient characteristic values for all other characteristics including the ratio.

[0051]

As described above in detail, the halftone type phase shift mask blank and the halftone type phase shift mask of the present invention have a light translucent film for forming a light transmissive part on a transparent substrate. The light translucent film has a property of transmitting light having an intensity that does not substantially contribute to exposure and a property of shifting the phase of exposure light by a predetermined amount, and at the same time, does not charge the electron beam at the time of drawing. Since it also has the above conductivity and can be freely controlled, it has become possible to prevent charge accumulation and electrification due to static electricity during electron beam drawing with a simple film configuration.

[Brief description of drawings]

FIG. 1 is a diagram showing a halftone type phase shift mask blank of the present invention and a halftone type phase shift mask of the present invention. FIG. 1A is a cross-sectional view of an example of a halftone type phase shift mask blank. FIG. 1B is a sectional view of an example of a halftone type phase shift mask.

FIG. 2 is an explanatory view showing an example of a manufacturing process of a halftone type phase shift mask of the present invention.

FIG. 3 is an operation explanatory view of a halftone type phase shift mask.

FIG. 4 is a diagram showing the dependence of the light transmittance on the wavelength of the light semi-transmissive film of the halftone type phase shift mask blank obtained in Example 1.

5 is a diagram showing the results of ESCA analysis of atom distribution in the depth direction from the film surface of the light semitransmissive film in the halftone phase shift mask blank obtained in Example 1. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Light semi-transmission part 2a Light semi-transmission film 3 Light transmission part 4 Resist pattern 4a Resist film

Claims (3)

[Claims] 1. A light-semitransmissive film is provided on a transparent substrate, and the light-semitransmissive film is composed of a film containing a transition metal, silicon, oxygen and / or nitrogen as main components, and A halftone phase shift mask blank, characterized in that silicon is contained in at least the form of silicon oxide and / or silicon nitride in the transparent film. 2. The light-semitransmissive film in the phase shift mask blank according to claim 1 is subjected to a patterning process for removing a part of the light-semitransmissive film according to a predetermined pattern,
A halftone phase shift mask, comprising a mask pattern formed of a light transmitting portion and a light semi-transmitting portion. 3. A lithography method, wherein pattern transfer is performed by using the halftone type phase shift mask according to claim 2.