JPH09197649A - Single layer half tone type phase shift mask blank and single layer half tone type phase shift mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the pattern edge shape reproducibility, and to shorten the edging time of a translucent shielding pattern by setting a composition ratio of oxygen/nitrogen in a film of a translucent shielding layer in the specified range. SOLUTION: A translucent shielding layer 2, which is composed of molybdenum, silicone, oxygen and nitrogen, is formed at the predetermined film thickness on a transparent board 1 so as to form a single layer half tone phase shift mask blank having the translucent shielding layer 2. As a method for forming a film, PDV and CVD is used. At this stage, film forming condition of the translucent shielding layer 2 is set at 1.4-2.1 of composition ratio of oxygen/nitrogen, at 5-10% of optical transmission, at 170-180 degree of phase difference by using a molybdenum silyside target at Si=1:2. Next, a chrome layer 3 is formed on the translucent shielding layer 2, and baking, exposure and development are performed so as to form a resist pattern 4a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single layer halftone type phase shift mask. More specifically, the present invention can be used in a conventional projection exposure apparatus like a conventional photomask, and further, a single-layer halftone phase shift mask that improves the resolution of a pattern as compared with the case of using a conventional photomask. Regarding

[0002]

2. Description of the Related Art In a conventional photomask, when a fine pattern is projected and exposed, light that has passed through a light transmitting portion of the mask is diffracted and interferes with an adjacent pattern.
There has been a problem that the patterns transferred onto the wafer are not separated and resolved by intensifying the light intensities at the pattern boundaries and exposing them to each other. This phenomenon is more likely to occur for finer patterns closer to the exposure wavelength. In principle, it was impossible to resolve a fine pattern having a wavelength equal to or less than the wavelength of light using a conventional photomask and a conventional exposure optical system. Therefore, a phase shift mask using a phase shift technique has been developed, in which the resolution of a fine pattern is improved by setting the phase difference between projection lights that pass through adjacent patterns to 180 degrees. In other words, by providing a phase shift portion on one side of the adjacent opening, when transmitted light is diffracted and interferes with each other, the light intensity at the boundary is weakened due to the phase inversion, so that the transfer pattern is separated. Resolve. Since this relationship is established before and after the focal point, even if the focal point is slightly shifted, the resolution is improved as compared with the conventional method, and the focus latitude is improved.

The phase shift method as described above is based on Le of IBM.
Proposed by Venson et al., JP-A-58-173
744 and Japanese Patent Publication No. 62-50811.
When the pattern is formed by a light-shielding layer, a phase shift portion is provided on one side of the opening adjacent to the light-shielding pattern to invert the phase, but the light-shielding layer does not have complete light-shielding properties, and the semitransparent light-shielding layer The same resolution improvement effect can be obtained even when the phase is inverted, and in this case, it is particularly effective in improving the resolution of the isolated pattern.

A phase shift mask which gives such an effect is generally called a halftone type. There are two types of this technique: a two-layer halftone mask in which a semitransparent film and a phase shift layer are laminated, and a single layer halftone mask in which a semitransparent light-shielding layer mask also has a phase shift effect. Here, if the effects of the single-layer and double-layer phase shift masks are the same, the single-layer halftone type phase shift mask is advantageous in view of the manufacturing process because it has fewer steps.

The present technique is applied to, for example, the 38th Spring Applied Physics Society Proceedings Second Volume p535, 29p-zc-3 (199).
1). To maximize the phase shift effect, a phase shift of 180 ° is desirable.
For this purpose, the semitransparent light-shielding layer should be formed so that the relationship of d = λ / {2 (n-1)} (d is the film thickness of the phase shift portion, λ is the exposure wavelength, and n is the refractive index) is established. Good.

FIG. 3 shows a conventional single layer halftone type phase shift mask blank. FIG. 3 shows Mo on the transparent substrate 1.
A semi-transparent light-shielding layer 13 of SiON system is provided. Although the semi-transparent light-shielding layer 13 satisfies the optical characteristics, the edge shape of the mask pattern becomes an inverse taper shape as shown in FIG. 4 or a taper shape as shown in FIG. However, there was a problem in the accuracy and reproducibility of the pattern shape. Further, there is a problem that the dry etching time required for pattern formation becomes long and the surface of the mask and the pattern edge shape are damaged. Normally, the dry etching time is preferably 300 seconds or less.
Here, the dry etching time means the RIE device MSDE.
7015 (manufactured by Nippon Vacuum Technology Co., Ltd.)
00W, pressure 0.1 Torr, electrode distance 60mm, C
_This is the time when the semi-transparent light-shielding layer is etched under the condition of ₂ F ₆ : O ₂ = 80: 20 (sccm) and the pattern processing is completed.

[0007]

As described above, the conventional M
The oSiON film has excellent optical characteristics and acid resistance,
There is a problem in pattern accuracy and reproducibility in the pattern forming process, and there is a problem in that transfer accuracy is deteriorated. The present invention has been made in view of the above problems, and is a single layer that is excellent in pattern edge shape reproducibility when patterning a semitransparent light-shielding layer and that can form a semitransparent light-shielding pattern in a shorter etching time. It is an object to provide a halftone type phase shift mask blank and a single-layer halftone type phase shift mask manufactured using the blank.

[0008]

[Means for Solving the Problems] In order to achieve the above objects in the present invention, as a result of various studies and experiments, MoSiO
It was found that the composition ratio of oxygen and nitrogen in the film of the N-based semitransparent light-shielding layer influences the shape reproducibility of the pattern edge and the etching time when pattern processing is performed by dry etching, and to complete the present invention. I arrived. That is, first, claim 1
In a single-layer halftone phase shift mask blank and a mask comprising a MoSiON-based semitransparent light-shielding layer, the composition ratio of oxygen / nitrogen in the film of the semitransparent light-shielding layer is in the range of 1.4 to 2.1. The single-layer halftone type phase shift mask blank is characterized in that

According to a second aspect of the present invention, there is provided a single layer halftone type phase shift mask manufactured by using the single layer halftone type phase shift mask blank of the first aspect.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing a single-layer halftone phase shift mask blank having a semitransparent light-shielding layer of the present invention, a single-layer halftone phase shift mask manufactured using the blank, and a manufacturing process thereof. First, the transparent substrate 1 is made of an optically transparent material such as synthetic quartz glass that is generally used for photomasks, and the thickness thereof is not particularly limited, but usually 1.5 to 7 mm. Used.

Next, a semi-transparent light-shielding layer 2 made of molybdenum, silicon, oxygen, and nitrogen is formed on the transparent substrate 1 to a predetermined thickness, and the semi-transparent light-shielding layer of the present invention shown in FIG. A single-layer halftone phase shift mask blank having layers is produced. A PVD method or a CVD method is used as a film forming method. At this time, the semitransparent light-shielding layer 2 uses a molybdenum silicide target of Mo: Si = 1: 2 so that the composition ratio of oxygen / nitrogen is 1.4 to 2.1, and the optical transmittance at that time is The film forming conditions are set so that the phase difference is 5 to 10% and the phase difference is 170 to 180 °. Here, the film forming conditions include, for example, in the case of reactive sputtering, the film forming vacuum degree in the chamber, power, and gas flow rates of argon, oxygen, and nitrogen.

Next, a chrome layer 3 is formed on the semitransparent light-shielding layer 2, a resist layer 4 is further formed, and baking, exposure, and
Development is performed to form a resist pattern 4a. This step is a conventional lithographic process. Further, the chrome layer 3 is etched using the resist pattern 4a as a mask to form a chrome pattern 3a (see FIG. 1C). The etching method for the chrome layer 3 is wet,
Any method of dry etching may be used.

Finally, after removing and removing the resist pattern 4a, dry etching is performed using the chrome pattern 3a as a mask resist to form a semitransparent light-shielding pattern 2a (see FIG. 1D). After forming the semi-transparent light-shielding pattern 2a, the chromium pattern 3a is removed by a chromium etching solution or the like to complete the single-layer halftone phase shift mask of the present invention shown in FIG. 1 (e).

As a result of forming a mask using the semi-transparent light-shielding layer 2 of the present invention, the pattern edge after dry etching became almost rectangular. Further, as shown in FIG. 2, the dry etching time could be set within 300 seconds.

[0015]

EXAMPLES The present invention will be described in more detail below with reference to FIG. 1 by way of examples.

On the cleaned synthetic quartz glass substrate 1 (thickness: 2.3 mm, size: 5 inch square), Mo: Si = 1:
The semi-transparent light-shielding layer 2 was formed by a reactive sputtering method using a molybdenum silicide of No. 2 as a target and Ar as a carrier gas and oxygen and nitrogen as additive gases. The film forming conditions are a DC power supply and Ar / O ₂ / N ₂ = 33.2.
A mixed gas of /15.0/3.5 (sccm) was used, and the power was 300 W and the gas pressure was 0.25 Pa. After film formation, 2
Heat treatment was carried out at 50 ° C. for 1 hour to prepare a single-layer halftone type phase shift mask blank of the present invention having the semitransparent light-shielding layer 2 shown in FIG. The optical characteristics of this single-layer halftone type phase shift mask blank are as follows.
% And the phase difference was 180 degrees. Further, the composition ratio of oxygen / nitrogen in the film of this single-layer halftone type phase shift mask blank was 1.7. This composition ratio is measured by X-ray photoelectron spectroscopy (XPS) method in JPS-90MXVmi.
It was measured by cro (manufactured by JEOL Ltd.).

A step of patterning the single-layer halftone type phase shift mask blank produced by the above method to produce a mask will be described. First, the semitransparent light-shielding layer 2
A chromium film 3 was formed on the above by a sputtering method.
Furthermore, a novolac resin electron beam resist is coated,
The resist coat layer 3 was formed by baking (FIG. 1B).
reference).

Next, a pattern was drawn by an electron beam exposure apparatus and developed to form a resist pattern 4a. Further, the chrome layer 3 was etched using the resist pattern 4a as a mask to form a chrome pattern 3a. The etching method may be either wet or dry etching, but this time, wet etching was used (see FIG. 1C).

Next, after removing and removing the resist pattern 4a, dry etching was performed using the chrome pattern 3a as a mask to form a semitransparent light-shielding pattern 2a (see FIG. 1 (d)). The dry etching method is R
Using an IE apparatus MSDE7015 (manufactured by Nippon Vacuum Technology Co., Ltd.), power 100 W, pressure 0.1 Torr, electrode distance 60 mm, C ₂ F ₆ : O ₂ = 80: 20 (scc
m) under the condition of 250 seconds, continuously, power 90 W, pressure 0.3 Torr, electrode distance 60 mm,
30 under the condition of C ₂ F ₆ : O ₂ = 80: 20 (sccm)
Second etched. After forming the semi-transparent light-shielding pattern 2a, the chromium pattern 3a was removed with an etching liquid for exclusive use of chromium to complete the single-layer halftone phase shift mask of the present invention (see FIG. 1 (e)).

[0020]

As described above in detail, MoSiON
The composition ratio of oxygen / nitrogen in the semi-transparent light-shielding layer of the system is 1.4
When using a single-layer halftone type phase shift mask blank controlled in the range of to 2.1 to dry-etch the mask, the single layer halftone type phase shift mask has good pattern rectangularity and excellent shape reproducibility. Can be created. Furthermore, the dry etching time during pattern processing can be set within 300 seconds, and damage to the mask surface and the pattern side surface can be prevented.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a single-layer halftone phase shift mask blank of the present invention, a single-layer halftone phase shift mask manufactured by using the blank, and a manufacturing process thereof.

FIG. 2 is an explanatory diagram showing a relationship between a composition ratio of oxygen and nitrogen and a dry etching time in a MoSiON-based semitransparent light-shielding layer.

FIG. 3 is a cross-sectional view showing a conventional single-layer halftone type phase shift mask blank.

FIG. 4 is a partial cross-sectional view showing a pattern shape when a conventional single-layer halftone phase shift mask blank is patterned.

FIG. 5 is a partial cross-sectional view showing a pattern shape when a conventional single-layer halftone phase shift mask blank is patterned.

[Explanation of symbols]

 1 ... Transparent substrate 2 ... Semi-transparent light-shielding layer 2a ... Semi-transparent light-shielding pattern 3 ... Chrome layer 3a ... Chrome pattern 4 ... Resist layer 4a ... Resist pattern 13 ... Semi-transparent light-shielding layer 13a ... Semi-transparent light-shielding pattern 13b … Semi-transparent light-shielding pattern

Claims (2)

[Claims] 1. A single-layer halftone phase shift mask blank comprising a MoSiON-based semitransparent light-shielding layer and a mask, wherein the composition ratio of oxygen / nitrogen in the film of the semitransparent light-shielding layer is 1.4 to 2.1. A single-layer halftone type phase shift mask blank characterized in that 2. A single-layer halftone phase shift mask manufactured by using the single-layer halftone phase shift mask blank according to claim 1.