JP2003287872A - Pattern transfer method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pattern transfer method by which resolution on a wafer is enhanced using a halftone phase shifting mask adaptable to excimer laser exposure, satisfying optical constants as a phase shifting mask, controlling reflectance to exposure light and transmittance at an inspection wavelength and having high pattern forming accuracy with respect to a pattern transfer method including exposure using a halftone phase shifting mask. <P>SOLUTION: The above halftone phase shifting mask is obtained by disposing a transparent film and a translucent film in order on a light-transmissive substrate and patterning the transparent film and translucent film to form a transparent region comprising only the light-transmissive substrate and a translucent region having the patterned transparent film and translucent film on the light- transmissive substrate. Each of the transparent film and translucent film comprises a zirconium compound film and has 5-15% transmittance to exposure light, reflectance of ≤25% at an exposure wavelength and transmissivity of ≤30% at an inspection wavelength. <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 pattern transfer method in which a pattern is formed in a photolithography process in a semiconductor manufacturing process by exposing using a halftone type phase shift mask.

[0002]

2. Description of the Related Art In a conventional photomask, when projection exposure of a fine pattern is performed, light passing through a light transmitting portion of the mask is diffracted to interfere with each other, thereby enhancing the light intensity at the pattern boundary portion. Since the photoresist is exposed to light, there has been a problem that the pattern transferred onto the wafer is not separated and resolved. This phenomenon has a stronger tendency for finer patterns closer to the exposure wavelength, and in principle it has been impossible to resolve fine patterns below the wavelength of light with 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 making the phase difference between projection lights passing through adjacent patterns 180 degrees from each other. That is, by providing a phase shift part on one side of the adjacent openings, when the transmitted lights are diffracted and interfere with each other, the light intensities at the boundaries weaken because the phases are inverted, and as a result, the transfer pattern is separated. Resolve. Since this relationship holds before and after the focus, the resolution is improved and the focus margin is improved even if the focus is slightly deviated.

The phase shift method as described above is based on IBM's Le.
Proposed by Venson et al. and described in Patent Documents 1 and 2. When the mask pattern is formed of 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. The phase is inverted by the semitransparent layer, and the same resolution improving effect is obtained. In this case, it is particularly effective for improving the resolution of the isolated pattern.

[0005]

[Patent Document 1] JP-A-58-173744

[Patent Document 2] Japanese Patent Publication No. 62-50811

FIGS. 5A to 5C are explanatory views for explaining the resolution of a transfer pattern when projection exposure is performed on a wafer using a halftone type phase shift mask. As shown in this figure, of the exposure light incident perpendicularly to the mask surface, the exposure light I and III attenuate in amplitude when passing through the semitransparent light-shielding pattern 32, but about 8% of the light is transmitted. Since the exposure light II is the transmission light that passes through the transparent substrate 31 by 100%, the amplitude distribution of the exposure light on the wafer is as shown in FIG. 5B. Here, since the square of the amplitude of the light is proportional to the light intensity, the intensity distribution of the exposure light projected on the wafer surface is as shown in FIG. 5C, and the semitransparent light-shielding pattern 32 and the transmissive portion are shown. The light intensity at the boundary between and becomes zero. From this, the contrast of the pattern edge is improved and the resolution of the pattern is improved. Further, since the same effect is maintained before and after the focus, the resolution is improved even if the focus is slightly deviated, and thus the focus margin is improved.

A phase shift mask that gives such an effect is generally called a halftone type.

[0008]

[Patent Document 3] JP-A-7-168343

[Patent Document 4] JP-A-7-043887

[0009]

In the halftone type phase shift mask, in addition to the phase inversion amount which is an optical constant as the original phase shift mask: 180 degrees and the transmittance at the exposure wavelength: 5 to 15%, Some optical conditions such as reflectance at exposure wavelength: 25% or less and transmittance at inspection wavelength: 30% or less must be satisfied at the same time.

As a reason for this, if the reflectance of the photomask at the exposure wavelength is high, multiple reflection occurs between the semitransparent film and the wafer during photolithography, resulting in a decrease in pattern accuracy. Moreover, in the inspection and dimension measurement of the phase shift mask, the i-line (365n
m) or Ar + laser light (488 nm) in the visible light range is used, but the transmittance for this inspection wavelength is 3
If it exceeds 0%, the contrast between the transmissive part and the semi-transparent part is lowered, and there arises a problem that inspection / dimension measurement becomes difficult.

In order to avoid the above problems, 2
A multi-layered phase shift mask in which films of more than one layer are stacked is used. For example, in a halftone phase shift mask mainly composed of molybdenum silicide or chromium,
Problems such as difficulty in achieving the above optical conditions, controllability and reproducibility of the film in the sputtering process, and poor rectangular shape of the pattern shape in the etching process have been pointed out.

Particularly, in exposure using an excimer laser beam having a short wavelength, there is a problem that the reflectance and the transmittance at the inspection wavelength become high even if the transmittance and the phase difference at this wavelength are satisfied. Further, in electron beam drawing for patterning a resist, if the conductivity of the film is low, electrons are charged up and a pattern cannot be accurately formed. Alternatively, there is also a problem that static electricity is generated, and dust is likely to be adsorbed during the mask manufacturing process or use.

In order to solve the above-mentioned problems of the conventional halftone type phase shift mask, the present invention can be applied to excimer laser light exposure in particular, satisfying the optical constants of the phase shift mask and exposing at the exposure light. An object of the present invention is to provide a pattern transfer method in which the resolution and the inspection wavelength are controlled and a halftone phase shift mask having a high pattern formation accuracy is used to improve the resolution on a wafer.

[0014]

In order to solve the above problems in the present invention, first, in claim 1, in a pattern transfer method which is performed by exposure using a halftone type phase shift mask, the halftone Type phase shift mask, a transparent film and a semitransparent film are sequentially laminated on a transparent substrate,
Halftone formed by patterning the transparent film and the semitransparent film to form a transparent region consisting only of a translucent substrate, and a patterned transparent film and a semitransparent region having the translucent film on the translucent substrate. Type phase shift mask, wherein the transparent film and the semitransparent film are zirconium compound films, the transmittance of the exposure light is 5 to 15%, and the reflectance at the exposure wavelength is 25%.
The pattern transfer method is characterized in that the transmittance at the inspection wavelength is 30% or less.

Further, in the present invention, the zirconium compound film is a zirconium compound film selected from the group consisting of a zirconium oxide film, a zirconium nitride film, a zirconium oxynitride film and a zirconium halide film. The pattern transfer method according to claim 1 is used.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The halftone type phase shift mask according to the pattern transfer method of the present invention is provided with a transparent film and a semitransparent film made of a zirconium compound film on a transparent glass substrate. It is a patterned one that can be used for excimer laser light exposure,
In addition to the optical constants that should be satisfied as a phase shift mask (transmittance of exposure light passing through a transparent film and a semitransparent film: 5 to 15%, phase difference between light passing through a transparent region and a semitransparent region: 180 degrees) It also satisfies the optical conditions that the reflectance at the exposure wavelength is 25% or less and the transmittance at the inspection wavelength is 30% or less, and further imparts a predetermined conductivity to the upper semi-transparent film to render the electron beam drawing. The charge transfer is prevented, the pattern forming accuracy is improved, and the pattern transfer method of the present invention is intended to improve the pattern resolution at the time of exposure and transfer in total.

First, zirconium whose refractive index, extinction coefficient, and film thickness are adjusted on a transparent quartz glass substrate by sputtering using a zirconium or zirconium compound target in a mixed gas atmosphere of nitrogen, oxygen, halogen gas, or the like. A transparent film and a semitransparent film made of a compound film are formed, and a halftone phase shift mask blank is produced. Further, a resist is applied to this halftone type phase shift mask blank, and a halftone type phase shift mask is obtained through a series of patterning process steps such as electron beam drawing, development, baking, etching, resist peeling and cleaning.

[0018]

EXAMPLES Examples of a halftone type phase shift mask and a halftone type phase shift mask blank according to the pattern transfer method of the present invention will be described more specifically with reference to the drawings. <Example 1> Example 1 corresponds to KrF excimer laser (wavelength 248 nm) exposure, and is shown in FIG.
(C) is a schematic cross-sectional view showing a manufacturing process and a structure of a blank for a halftone type phase shift mask and a halftone type phase shift mask which are composed of a transparent film and a semitransparent film.

First, using a DC sputtering apparatus, argon (Ar) gas: 20 SCCM, oxygen (O ₂ ) gas: 3 SCCM, and nitrogen (N ₂ ) gas: 4 S in the chamber.
Reactive sputtering is performed using a zirconium target in a mixed gas atmosphere containing CCM to form a transparent film 12 made of a zirconium oxynitride film having a thickness of 858Å on a transparent substrate 11 made of transparent quartz glass. did. At this time, the refractive index of the transparent film 12 at a wavelength of 248 nm is 2.2.
0, the extinction coefficient was 0.21.

Next, using the same DC sputtering apparatus as described above, reactive sputtering was carried out using a zirconium target in a mixed gas atmosphere in which argon gas: 20 SCCM and oxygen gas: 2 SCCM were introduced into the chamber to obtain a transparent film. A semi-transparent film 13 made of a zirconium oxide film having a film thickness of 484 Å was formed on the film 12. At this time, the semitransparent film 13 has a refractive index of 1.79 and an extinction coefficient of 0.
It was 72. Through the above steps, the halftone phase shift mask blank 10 for KrF excimer laser (248 nm) exposure, which is composed of the transparent film 12 and the semitransparent film 13, is obtained on the transparent substrate 11 made of transparent quartz glass. (See FIG. 1 (a)).

FIG. 3 shows the spectral transmittance characteristics and spectral reflectance characteristics of the blank 10 for halftone type phase shift mask. The transmittance of the KrF excimer laser at the wavelength of 248 nm is 5%, and the transmittance at the inspection wavelength of 488 nm is 1.
It is 5.7%, and the contrast at the time of inspection can be sufficiently obtained. Further, the reflectance of the exposure light at a wavelength of 248 nm was 12.2%, which was a value that was not problematic in terms of the effect of multiple reflection during exposure.

Next, an electron beam resist is applied on the halftone type phase shift mask blank 10 by a spinner to form an electron beam resist layer, and a predetermined pattern is drawn with an electron beam and developed to have an opening 15. A resist pattern 14 was formed (see FIG. 1 (b)). Here, the sheet resistance of the semitransparent film 13 made of a zirconium oxide film is 3.4.
Since it was 3 × 10 3 Ω / □, charge-up during electron beam writing was not a problem.

Next, a blank for a halftone type phase shift mask on which the resist pattern 14 is formed is used as SiCl.
After patterning by dry etching using a halogen gas such as ₄ or SF ₆ or CF ₄ , the resist pattern 14 is stripped, and a KrF excimer laser (248 nm) exposure including a transparent film pattern 12a and a semitransparent film pattern 13a is performed. A corresponding halftone type phase shift mask 20 was obtained (see FIG. 1 (c)). The dry etching conditions here are pressure: 30 mTorr, power: 300
w, SiCl ₄ : 50 SCCM.

<Embodiment 2> Embodiment 2 corresponds to ArF excimer laser (wavelength 193 nm) exposure.
(A)-(c) is a schematic cross section which shows the manufacturing process and structure of the blank for halftone type phase shift masks which consists of a transparent film and a semitransparent film, and a halftone type phase shift mask.

Argon (Ar) gas: 14 SCCM and oxygen (O 2) were used in the chamber using the same apparatus as in Example 1.
₂ ) Gas: 8 SCCM and nitrogen (N ₂ ) gas: 8 SCC
Reactive sputtering is performed using a zirconium target in a mixed gas atmosphere containing M to form a transparent film 22 made of a zirconium oxynitride film having a film thickness of 484 Å on a transparent substrate 21 made of transparent quartz glass. did. At this time, the transparent film 22 has a refractive index of 2.80 at a wavelength of 193 nm.
The extinction coefficient was 0.33.

Next, using the same DC sputtering apparatus as described above, reactive sputtering was carried out using a zirconium target in a mixed gas atmosphere in which argon gas: 20 SCCM and oxygen gas: 2 SCCM were introduced into the chamber to obtain a transparent film. A semi-transparent film 23 made of a zirconium oxide film having a film thickness of 858Å was formed on the film 12. At this time, the semi-transparent film 23 has a refractive index of 2.15 and an extinction coefficient of 1.
It was 08. Through the above steps, the halftone phase shift mask blank 30 for ArF excimer laser (wavelength 193 nm) exposure, which is composed of the transparent film 22 and the semitransparent film 23, is obtained on the transparent substrate 11 made of transparent quartz glass. (See FIG. 2 (a)).

This ArF excimer laser (wavelength 193
FIG. 4 shows the spectral transmittance characteristics and the spectral reflectance characteristics of the blank 30 for a halftone phase shift mask that is compatible with exposure.
Shown in. ArF excimer laser wavelength 193 nm
The phase difference between the semi-transparent region and the transparent region is 180 degrees, and the transmittance of the semi-transparent region is 5%. The ArF excimer laser (19
It was confirmed that the blank was a halftone type phase shift mask blank that can be exposed to 3 nm).

Next, an electron beam resist is applied on the halftone type phase shift mask blank 30 by a spinner to form an electron beam resist layer, and a predetermined pattern is drawn with an electron beam and developed to have an opening 25. A resist pattern 24 was formed (see FIG. 2B). Here, the sheet resistance of the semitransparent film 23 made of a zirconium oxide film is 3.4.
Since it was 3 × 10 ³ Ω / □, charge-up at the time of electron beam drawing hardly caused a problem.

Next, a blank for a halftone type phase shift mask on which the resist pattern 24 is formed is used as SiCl.
After patterning by dry etching using a halogen gas such as ₄ , ₄ , SF ₆ , CF _4, etc., the resist pattern 24 is stripped, and an ArF excimer laser (wavelength 193 nm) composed of a transparent film pattern 22a and a semitransparent film pattern 23a. A halftone type phase shift mask 40 corresponding to exposure was obtained (see FIG. 2C). The dry etching conditions here are pressure: 30 mTorr, power: 30
0w, SiCl ₄ : 50 SCCM.

[0030]

The pattern transfer method of the present invention uses a zirconium compound film such as zirconium oxide for the transparent film and the semitransparent film of the halftone type phase shift mask according to the present invention, whereby the excimer laser (wavelength: (248, 193 nm), the reflectance with exposure light and the transmittance at the inspection wavelength can be easily controlled in addition to the optical constants as a phase shift mask, and there is no effect of multiple reflections with exposure light, which is high. This is a pattern transfer method capable of obtaining pattern formation accuracy. That is, 1) KrF (wavelength 248 nm), ArF (wavelength 193n)
In the low wavelength excimer laser exposure of m), it has high pattern formation accuracy and is excellent in pattern shape reproducibility. 2) Transmittance of 3 at inspection wavelength such as Ar + laser light
Since 0% or less can be controlled, sufficient contrast at the time of inspection can be obtained. 3) Since the reflectance for the exposure wavelength can be 25% or less, the adverse effect of multiple reflection can be reduced and the pattern accuracy can be improved. 4) Since the semitransparent film has appropriate conductivity, it is possible to prevent charge-up during electron beam writing. 5) Since the transparent film and the semi-transparent film made of a zirconium compound such as zirconium oxide are hard, it is possible to suppress defects due to damage and scratches in the process of manufacturing the phase shift mask and the inspection process.

[Brief description of drawings]

FIG. 1A is a schematic cross-sectional view showing the configuration of Example 1 of a halftone type phase shift mask blank according to the pattern transfer method of the present invention. (B)-(c) is a schematic cross section which shows the manufacturing process and structure of Example 1 of the halftone type phase shift mask which concerns on the pattern transfer method of this invention.

FIG. 2A is a schematic cross-sectional view showing the configuration of Example 2 of the halftone phase shift mask blank according to the pattern transfer method of the present invention. (B)-(c) is a schematic cross section which shows the manufacturing process and structure of Example 2 of the halftone type phase shift mask which concerns on the pattern transfer method of this invention.

FIG. 3 is a spectral transmittance and a spectral reflectance of a transparent film and a semi-transparent film that constitute Example 1 of the halftone phase shift mask blank and the halftone phase shift mask according to the pattern transfer method of the present invention. It is explanatory drawing which shows a characteristic.

FIG. 4 is a halftone phase shift mask blank according to the pattern transfer method of the present invention and a spectral transmittance and a spectral reflectance of a transparent film and a semitransparent film that constitute Example 2 of the halftone phase shift mask. It is explanatory drawing which shows a characteristic.

FIG. 5A is an explanatory diagram showing a case where projection exposure is performed using a halftone type phase shift photomask.
(B) is an explanatory view showing an amplitude distribution of exposure light on a wafer. (C) is an explanatory view showing an intensity distribution of exposure light on a wafer.

[Explanation of symbols]

Blanks for halftone type phase shift masks 11, 21, 31 ... Transparent substrates 12, 22 ... Transparent films 12a, 22a ... Transparent film patterns 13, 23 ... Semitransparent films 13a, 23a ...... Semitransparent film pattern 14, 24 ...... Resist pattern 15, 25 ...... Aperture 20, 40 ...... Halftone type phase shift mask 32 ...... Semitransparent light shielding pattern

Claims (2)

[Claims] 1. A pattern transfer method in which exposure is performed using a halftone type phase shift mask, wherein the halftone type phase shift mask comprises a transparent film and a semitransparent film sequentially laminated on a transparent substrate, Halftone type in which a transparent film and a semitransparent film are patterned to form a transparent region consisting only of a translucent substrate, and a patterned transparent film and a semitransparent region having the semitransparent film are formed on the translucent substrate. A phase shift mask, wherein the transparent film and the semitransparent film are zirconium compound films, the transmittance of exposure light is 5 to 15%, the reflectance at the exposure wavelength is 25% or less, and at the inspection wavelength. The pattern transfer method is characterized by having a transmittance of 30% or less. 2. The pattern according to claim 1, wherein the zirconium compound film is a zirconium compound film selected from the group consisting of a zirconium oxide film, a zirconium nitride film, a zirconium oxynitride film, and a zirconium halide film. Transfer method.