JPH06242592A - Phase shift mask and its production - Google Patents

Abstract

(57) [Summary] [Object] To provide a phase shifter mask in which defects and the like do not enter the glass substrate and the phase shifter during the manufacturing process, and a manufacturing method thereof. [Structure] On the light-shielding film 2, there is one gap between the auxiliary film 3 and an auxiliary film 3 adjacent to the auxiliary film 3 whose total thickness together with the film thickness of the light-shielding film 2 is necessary to invert the phase of exposure light. It is provided so that it is wide for the rest. As a result, in the transparent film 4 formed on the entire surface of the glass substrate 1, in the region where the auxiliary film 3 is set wide, the depth thereof is equal to the sum of the film thicknesses of the light shielding film 2 and the auxiliary film 3. Are formed in a self-aligned manner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask for use in photolithography technology, and more particularly to a phase shift mask and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, there has been a remarkable increase in the degree of integration and miniaturization of semiconductor integrated circuits, and along with this, the miniaturization of circuit patterns formed on a semiconductor substrate (hereinafter simply referred to as a wafer) is rapidly progressing. is made of. Among them, photolithography technology is widely recognized as a basic technology for pattern formation, and various developments and improvements have been made to date. The demands are even stronger.

In general, the resolution limit R (nm) in the photolithography technique using the reduction exposure method is expressed as R = k ₁ · λ / (NA) (1). Where λ is the wavelength of the light used (nm),
NA is the number of apertures in the lens, and k ₁ is a constant that depends on the resist process.

As can be seen from the above equation, in order to improve the resolution limit, k ₁ and λ should be small and NA should be large. In other words, it is only necessary to reduce the constant depending on the resist process, and to shorten the wavelength and increase the NA, but it is technically difficult to improve the light source and the lens, and to shorten the wavelength and increase the NA. As a result, the depth of focus δ of light (δ = k ₂ · λ / (NA) ² ) becomes shallower, which causes a problem of lowering the resolution.

Referring to FIG. 12, there are shown a mask cross section, an electric field on the mask, and a light intensity on the wafer when a conventional photomask is used. In the figure, a metal mask pattern 2 made of chromium or the like is formed on a glass substrate 1, and when considering transfer of a fine pattern exceeding a resolution limit (R), a mask is formed on adjacent pattern images. And the light transmitted through the optical system reinforces each other in the overlapping portion of the light due to the diffraction phenomenon of the light and the interference effect. As a result, there is a problem that the difference in light intensity on the wafer becomes small and the resolution is lowered.

Photomasks for solving this problem are disclosed, for example, in Japanese Patent Laid-Open Nos. 57-62052 and 58-58.
In 173744, a phase shift exposure method using a phase shift mask is proposed.

Referring to FIG. 13, Japanese Patent Laid-Open No. 58-1737.
It is a cross section of the mask when the phase shift mask disclosed in Japanese Patent Publication No. 44-44 is used, an electric field on the mask, and a light intensity on the wafer. In the figure, a phase shift mask is formed by providing a phase shifter 6 made of a transparent insulating film such as a silicon oxide film at every other opening portion of the chromium mask pattern 2 formed on the glass substrate 1. .

Since the electric field on the mask due to the light transmitted through the phase shift mask is constructed by inverting the phases thereof alternately by 180 °, the light transmitted through the phase shift mask and the optical system in adjacent pattern images. Since the phases of the overlapping lights are reversed, the interference effects cancel each other at the overlapping parts of the lights. As a result, the difference in light intensity on the wafer becomes sufficient, and the resolution can be improved. This phase shift mask is very effective for a periodic pattern.

Next, a method of manufacturing the phase shift mask shown in FIG. 13 will be described with reference to FIGS.

First, referring to FIG. 14, a metal film such as a chromium film 2 is formed on a transparent glass substrate 1 by a sputtering method or the like.
Form a.

Next, referring to FIG. 15, an electron beam (hereinafter referred to as EB
A resist is applied to the entire surface, heat treatment is performed, a predetermined pattern is drawn on the EB resist using an EB drawing device, and development is performed to form a resist pattern 7a.

Then, referring to FIG. 16, using resist pattern 7a as a mask, chromium film 2a is etched by anisotropic or isotropic etching to form a metal pattern, for example, chromium pattern 2.

Next, referring to FIG. 17, the resist pattern 7a remaining on the chromium pattern 2 is entirely removed by exposing it to O ₂ plasma.

Then, referring to FIG. 18, a phase shifter film 8 is formed by applying a heat treatment, for example, an SOG film, which is a material of the phase shifter, to the entire surface of the substrate and performing heat treatment.

Next, referring to FIG. 19, an EB resist is applied to the entire upper surface of the phase shifter film 8 in the same manner as described above, heat treatment is performed, and then the phase shifter film 8 is left using an EB drawing device. A resist pattern 7c is formed at desired places.

Then, referring to FIG. 20, the phase shifter film 8 is etched using the resist pattern 7c as a mask to form the phase shifter 6.

Next, referring to FIG. 21, the resist pattern 7c is exposed to O ₂ plasma to completely remove the resist pattern 7c to complete the phase shift mask.

[0018]

However, the above-mentioned prior art has the following problems.

First, after the normal phase shift mask is produced, the finish inspection of the phase shift mask is performed. This finish inspection is mainly for inspecting defects such as cracks in the glass substrate and the phase shift mask, which are caused by peeling of the resist film in the manufacturing process.
In this inspection, if a defect is found in the phase shift mask, the defective portion is to be corrected.
Particularly, in the above-described conventional method for manufacturing a phase shift mask, in the steps of FIGS. 19 to 21, the EB resist film 7c is formed into a predetermined pattern, and then the phase shifter film 8 is used as a mask with the EB resist film 7c. However, there is a problem in that the above-mentioned defects are likely to occur because the above is etched into a predetermined shape. Further, in the finish inspection, an inspection using an optical method is performed, and since the substrate and the phase shifter are both made of a transparent material,
There is a problem in that it cannot be inspected and corrected because it is not possible to distinguish between the location where the phase shifter is not added and the location where the phase shifter is added.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a phase shift mask in which defects and the like do not enter the glass substrate and the phase shifter in the manufacturing process, and a manufacturing method thereof. .

[0021]

In a phase shift mask according to the present invention, a substrate which transmits exposure light, a light-shielding film disposed on the substrate, and the light-shielding film on the light-shielding film are provided. An auxiliary film having a predetermined width smaller than that of the auxiliary film, which is alternately arranged at the left end and the right end of the light-shielding film, and whose sum of the film thickness of the light-shielding film is a thickness for inverting the phase of exposure light; Recesses formed along the entire surface of the substrate and having a depth equal to the sum of the film thickness of the light shielding film and the film thickness of the auxiliary film in a region where the intervals between adjacent auxiliary films are set to be wide at intervals of one by one. And a transparent film having.

Next, the method of manufacturing a phase shift mask according to the present invention includes the following steps.

First, a light shielding film is formed on a substrate that transmits exposure light. After that, on the light-shielding film, the light-shielding film has a predetermined width smaller than that of the light-shielding film and is alternately arranged at the left end and the right end of the light-shielding film. An auxiliary film having a thickness for reversing the phase is formed. Next, deposit along the entire surface of the substrate,
A transparent film having a recess having a depth equal to the sum of the film thickness of the light-shielding film and the film thickness of the auxiliary film is formed in a region where the intervals between the adjacent auxiliary films are set to be large at intervals of one interval. .

[0024]

According to the phase shift mask and the method of manufacturing the same according to the present invention, the auxiliary film is provided on the light-shielding film so that the sum of the film thickness of the light-shielding film and the phase of the exposure light is inverted. To be In addition, the intervals of the auxiliary films are set to be wide every other space.

As a result, in the transparent film formed on the entire surface of the substrate, in the region where the auxiliary film is widely set,
A recess is formed whose depth is equal to the sum of the film thickness of the light shielding film and the film thickness of the auxiliary film.

Therefore, it is possible to provide a predetermined difference in light intensity between the exposure light transmitted through the transparent film having the above-mentioned recesses in the wide area between the auxiliary films and the exposure light transmitted through the narrow area between the auxiliary films. Become. Further, since the transparent film can be formed only by depositing it on the substrate, it is possible to reduce the possibility of occurrence of defects and the like.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described below with reference to the drawings.

First, the sectional structure of the phase shift mask in this embodiment will be described with reference to FIG.

On a glass substrate 1 made of quartz or the like, a light shielding film 2 made of chromium or the like having a predetermined width and arranged at a predetermined pitch is formed. The light-shielding film 2 has a width smaller than that of the light-shielding film 2 and is alternately arranged at the left end and the right end of the light-shielding film 2. The total thickness of the light-shielding film 2 is the exposure light. The auxiliary film 3 having a film thickness (d) for inverting the phase of is formed.

In addition, in a region which is formed along the entire surface of the glass substrate 1 and in which the intervals between the adjacent auxiliary films 3 are set to be wide at intervals of one by one, the film thickness d1 of the light shielding film 2 and the auxiliary film 3 are formed. A transparent film 4 having a recess 5 having a depth equal to the total film thickness d2 is formed.

The film thickness d (nm) is a film thickness required for the phase shifter and can be expressed by the following equation.

D = λ / (2 (n-1)) λ is the wavelength of light (nm) n is the refractive index of the phase shifter Therefore, when the i-line is used for the exposure light and the silicon oxide film is used for the phase shifter, λ = 365 nm, n = 1.42, and d
= 434.5 nm.

Therefore, when exposure is performed using the phase shift mask, it is possible to provide a predetermined light intensity difference between the light transmitted through the concave portion 5 and the light transmitted through the portion where the concave portion is not provided. Therefore, it becomes possible to perform high-resolution transfer.

Next, referring to FIG. 2, the electric field on the mask and the light intensity on the wafer when the phase shift mask having the above structure is used are shown. Similar to the conventional phase shift mask shown in FIG.
Since the recesses 5 are provided at alternate intervals, the phases of the electric fields on the mask are alternately inverted by 180 °. Therefore, in the adjacent pattern images, the light transmitted through the phase shift mask and the optical system overlap each other. Since the phase is reversed, the interference effects cancel each other at the overlapping portions of the light, and the difference in the light intensity on the wafer becomes sufficient, and the resolution can be improved.

Next, a method of manufacturing the phase shift mask having the above structure will be described with reference to FIGS.

First, referring to FIG. 3, on a transparent glass substrate 1 made of quartz or the like, a metal film,
For example, the chromium film 2a is formed. Generally, the metal film in the photomask is formed with a thickness of about 100 nm.

Next, referring to FIG. 4, an EB resist is applied on the entire surface of the glass substrate 1 to a thickness of about 500 nm to 700 nm,
After the heat treatment, a predetermined pattern is drawn by using an EB drawing device and a development process is performed to form the resist pattern 7a.
To form.

Next, referring to FIG. 5, the chrome film 2a is etched using the resist pattern 7a as a mask to form the light shielding film 2. At this time, in the isotropic etching method, wet etching is performed using ammonium cerium nitrate and perchloric acid, and in the anisotropic etching method, dry etching is performed using a mixed gas of carbon tetrachloride and oxygen. Etch.

Next, referring to FIG. 6, the resist pattern 7a is entirely removed by exposing it to O ₂ plasma.

Next, referring to FIG. 7, a material different from the light-shielding film 2, for example, a MoSi film 3a is formed on the entire surface by a sputtering method or the like. At this time, when the film thickness required for the phase shifter is 434.5 nm, the MoSi film 3a is formed because the light-shielding film 2 previously formed has a film thickness of 100 nm.
A film is formed with a thickness of 334.5 nm.

Next, referring to FIG. 8, resist patterns 7b are formed on the upper surface of the MoSi film 3a, which are alternately arranged at the left end and the right end above the light shielding film 2.

Then, referring to FIG. 9, MoSi film 3a is etched using resist pattern 7b as a mask to form auxiliary pattern 3. The etching is performed by using an anisotropic etching method. At this time, C
Dry etching is performed using a mixed gas of F ₄ + O ₂ .

Next, referring to FIG. 10, the resist pattern 7b is exposed to O ₂ plasma to remove the entire surface.

Next, referring to FIG. 11, a silicon oxide film 4 is deposited on the entire surface of the glass substrate 1 by the CVD method. At this time, as shown in FIG. 11, the deposition of the silicon oxide film 4 is performed until the region of the auxiliary film 3 having a narrow interval is completely covered with the silicon oxide film.

At this time, in the region where the distance between the auxiliary films 2 is wide, the concave portion 5 having a depth equal to the height of the sum of the film thicknesses of the light shielding film 2 and the auxiliary film 3 is formed.
As described above, since the phase shifter can be formed only by depositing the silicon oxide film on the substrate,
Since there is no need to process this silicon oxide film,
It is possible to reduce the possibility of occurrence of defects and the like, and substantially no defect inspection and repair of the silicon oxide film are required.

[0046]

According to the phase shift mask and the method of manufacturing the same according to the present invention, the sum of the film thickness of the light-shielding film and the film thickness necessary for inverting the phase of the exposure light is provided on the light-shielding film. The auxiliary films are formed, and the intervals between the auxiliary films are set to be wide every other interval.

As a result, in the transparent film formed on the entire surface of the substrate, a recess having a depth equal to the sum of the film thickness of the light shielding film and the film thickness of the auxiliary film is formed in the region where the auxiliary film is set wide. It is formed in a self-aligned manner.

Therefore, a predetermined phase difference is provided between the exposure light transmitted through the transparent film having the above-mentioned recesses in the wide area between the auxiliary films and the exposure light transmitted through the transparent film in the narrow area between the auxiliary films. As a result, it becomes possible to transfer a highly accurate image like the conventional phase shift mask.

Further, since the transparent film can be formed only by depositing it on the substrate, there is no need to process the transparent film, and it is possible to prevent defects and the like that occur during this processing. In addition, the defect inspection and repair are substantially unnecessary, and it is possible to provide an extremely high-quality phase shift mask.

[Brief description of drawings]

FIG. 1 is a sectional structural view of a phase shift mask based on the present invention.

FIG. 2 is a schematic diagram showing the relationship between the electric field on the mask and the light intensity on the wafer when the phase shift mask according to the present invention is used.

FIG. 3 is a cross-sectional view showing a first manufacturing process of a phase shift mask according to the present invention.

FIG. 4 is a sectional view showing a second manufacturing step of the phase shift mask based on the present invention.

FIG. 5 is a sectional view showing a third manufacturing process of the phase shift mask based on the present invention.

FIG. 6 is a sectional view showing a fourth manufacturing process of a phase shift mask based on the present invention.

FIG. 7 is a cross-sectional view showing a fifth step of manufacturing a phase shift mask according to the present invention.

FIG. 8 is a sectional view showing a sixth manufacturing step of the phase shift mask according to the present invention.

FIG. 9 is a sectional view showing a seventh manufacturing step of the phase shift mask according to the present invention.

FIG. 10 is an eighth phase shift mask according to the present invention.
It is sectional drawing which shows a manufacturing process.

FIG. 11 is a ninth phase shift mask according to the present invention.
It is sectional drawing which shows a manufacturing process.

FIG. 12 is a schematic diagram showing the relationship between the electric field on the mask and the light intensity on the wafer of the photomask in the conventional technique.

FIG. 13 is a schematic diagram showing the relationship between the electric field on the mask and the light intensity on the wafer of the phase shift mask in the prior art.

FIG. 14 shows a first phase shift mask according to the related art.
It is sectional drawing which shows a manufacturing process.

FIG. 15 is a second phase shift mask according to the related art.
It is sectional drawing which shows a manufacturing process.

FIG. 16 is a third phase shift mask according to the related art.
It is sectional drawing which shows a manufacturing process.

FIG. 17 shows a fourth phase shift mask according to the related art.
It is sectional drawing which shows a manufacturing process.

FIG. 18 shows a fifth phase shift mask according to the related art.
It is sectional drawing which shows a manufacturing process.

FIG. 19 shows a sixth phase shift mask according to the related art.
It is sectional drawing which shows a manufacturing process.

FIG. 20 shows a seventh phase shift mask according to the related art.
It is sectional drawing which shows a manufacturing process.

FIG. 21 shows an eighth conventional phase shift mask.
It is sectional drawing which shows a manufacturing process.

[Explanation of symbols]

 1 Glass substrate 2 Light-shielding film 3 Auxiliary film 4 Transparent film 5 Recess 6 Phase shifter part In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] 1. A substrate that transmits exposure light, a light-shielding film disposed on the substrate, and a light-shielding film having a predetermined width smaller than the light-shielding film on the light-shielding film. Of the auxiliary film, which is alternately arranged at the left end and the right end of the light-shielding film, and has a total thickness with which the light-shielding film inverts the phase of the exposure light. A phase shift mask comprising: a transparent film having a recess having a depth equal to the sum of the film thickness of the light-shielding film and the film thickness of the auxiliary film in regions where the intervals are set to be wide. 2. A step of forming a light-shielding film on a substrate that transmits exposure light, and a left end of the light-shielding film having a predetermined width smaller than the light-shielding film on the light-shielding film. And a step of forming an auxiliary film which is alternately arranged at the right end and has a total thickness with the film thickness of the light-shielding film that inverts the phase of the exposure light. Forming a transparent film having a recess having a depth equal to the sum of the film thickness of the light-shielding film and the film thickness of the auxiliary film in the regions where the film intervals are set to be wide every other film. For manufacturing a phase shift mask.