JPH05127361A - Halftone phase shift photo mask - Google Patents

Abstract

(57) [Abstract] [Purpose] A halftone phase shift photomask with a simpler structure and easier manufacturing. [Structure] A transparent substrate 10 and a halftone light shielding layer / phase shift layer 11 made of a uniform composition material provided on a surface of the transparent substrate 10 in accordance with a predetermined pattern. When λ and its refractive index are n, the film thickness d is approximately d = λ / {2 (n-
1)} or an odd multiple thereof, and the transmittance is in the range of approximately 5 to 30%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask used in the manufacture of high density integrated circuits such as LSI and VLSI, and more particularly to a halftone phase shift used for forming a fine pattern with high accuracy. Regarding photomasks.

[0002]

2. Description of the Related Art Semiconductor integrated circuits such as ICs, LSIs, and VLSIs are formed by applying a resist onto a substrate to be processed such as a Si wafer, exposing a desired pattern with a stepper, and then developing and etching it. It is manufactured by repeating the lithography process.

Photomasks called reticles used in such lithography processes tend to be required to have higher precision as semiconductor integrated circuits have higher performance and higher integration. DRA which is LSI
Taking M as an example, the dimensional deviation of a 5 × reticle for a 1 Mbit DRAM, that is, a reticle having a size 5 × that of a pattern to be exposed is an average value of ± 3σ (σ is a standard deviation). Also, a precision of 0.15 μm is required, and similarly, a quintuple reticle for a 4 Mbit DRAM has a dimensional precision of 0.1 to 0.15 μm of 16M.
5 times reticle for bit DRAM is 0.05-0.1 μm
Dimensional accuracy is required.

Further, the line width of the device pattern formed by using these reticles is 1 Mbit DRAM.
1.2 μm, 0.8 μm for 4M bit DRAM, 1
The 6 Mbit DRAM is required to be further miniaturized to 0.6 μm, and various exposure methods are being researched to meet such a demand.

However, when the next-generation device patterns of the 64 Mbit DRAM class are used, the resolution of resist patterns becomes the limit in the stepper exposure method using the reticle that has been used up to now, for example, Japanese Patent Laid-Open No. 58-1737.
A reticle having a new concept of a phase shift mask as disclosed in Japanese Patent Publication No. 44, Japanese Patent Publication No. 62-59296, etc. has been proposed. Phase shift lithography using this phase shift reticle is a technique for improving the resolution and contrast of a projected image by manipulating the phase of light passing through the reticle.

A halftone phase shift photomask has been proposed as one of such phase shift masks. This halftone phase shift photomask will be briefly described with reference to the drawings. FIG. 3 is a diagram showing the principle of halftone phase shift lithography, FIG. 4 is a diagram showing a conventional method, and FIGS. 3 (a) and 4 (a) are sectional views of the reticle, FIG. 3 (b) and FIG. 3B shows the amplitude of light on the reticle, FIGS. 3C and 4C show the amplitude of light on the wafer, and FIGS. 3D and 4D show the light intensity on the wafer. 1 is a substrate, 2 is a 100% light-shielding film, 3 is 5
Halftone light shielding film having a transmittance of ˜30%, 4 is a phase shift layer, and 5 is incident light.

In the conventional method, as shown in FIG. 4 (a), a substrate 1 made of quartz glass or the like is formed on a substrate 1 made of chromium or the like.
Only the light-transmitting portion having a predetermined pattern is formed by forming the 00% light-shielding film 2, but in the halftone phase shift lithography, as shown in FIG. A phase shift layer 4 formed of a film and formed of a transmissive film for inverting the phase (phase difference of 180 °) is provided on the halftone light shielding film 3. Therefore, in the conventional method, the amplitude of the light on the reticle becomes in-phase as shown in FIG. 4B, and the amplitude of the light on the wafer also becomes in-phase as shown in FIG. 4C, from the opening of the mask. As it is distributed outward in a skirted pattern, the result is shown in Fig. 4.
As shown in (d), the light intensity distribution on the wafer does not have a shape corresponding to the mask pattern, but has a distribution that spreads outward from the mask opening. On the other hand, in the halftone phase shift lithography, the light transmitted through the halftone light shielding film 3 and the phase shift layer 4 is
As shown in (b), since the light has a phase opposite to that of the light transmitted through the opening, the light intensity becomes zero at the boundary of the pattern.
As shown in (d), it is possible to suppress the bottom spread of the light intensity distribution. As described above, in the halftone phase shift lithography, a pattern that could not be conventionally decomposed can be decomposed, and the resolution can be improved.

Next, a method of manufacturing the halftone phase shift photomask proposed so far will be described. FIG. 5 is a sectional view showing the manufacturing process.
9 is a substrate, 20 is a conductive layer, 21 is a halftone light shielding layer,
22 is a phase shift layer, 23 is a resist, 24 is a resist pattern, 25 is an etching gas, 26 is a halftone light shielding pattern, and 27 is a phase shifter pattern.

First, as shown in FIG. 5B, an ionization of chloromethylated polystyrene or the like is carried out on a halftone phase shift photomask blank which is manufactured by a conventional method as shown in FIG. The radiation resist 23 is uniformly applied by a conventional method such as spin coating, and heat-dried. The heating and drying treatment is usually performed at 80 to 150 ° C. for 20 to 60 minutes, though it depends on the type of resist used. Next, a pattern is drawn on the resist layer 23 by ionizing radiation by an exposure device such as an electron beam drawing device according to a conventional method, developed with a developing solution containing an organic solvent such as ethyl cellosolve or ester as a main component, and rinsed with alcohol. Thus, a resist pattern 24 as shown in FIG.

Next, after performing unnecessary heat treatment and discum treatment to remove unnecessary resist such as resist scraps and beards remaining on the edge portion of the resist pattern 24, as shown in FIG. So that the resist pattern 2
4, the portion to be processed exposed from the opening, that is, the phase shift layer 22 and the halftone light shielding layer 21 is continuously dry-etched by changing the conditions of the etching gas plasma 25, and the halftone light shielding pattern 26 and the phase shifter pattern 27. To form. It is apparent to those skilled in the art that the halftone light shielding pattern 26 and the phase shifter pattern 27 may be formed by wet etching instead of dry etching by the etching gas plasma 25.

After that, the resist pattern 24, that is, the remaining resist is removed by a solvent to obtain a photomask. After cleaning this photomask, it is inspected to complete a halftone phase shift photomask having a phase shifter pattern 27 as shown in FIG.

[0012]

However, in the conventional halftone phase shift photomask as described above, it is necessary to form two layers of a phase shift layer and a halftone light shielding layer, which increases the number of blanks manufacturing steps. To do.
Further, the mask manufacturing process is increased due to the different etching conditions of the halftone light shielding layer and the phase shift layer. The defect inspection also needs to be performed for each of the halftone light shielding layer and the phase shift layer. Therefore, there are many problems such as high cost, long manufacturing period, and frequent defects.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a halftone phase shift photomask having a further simplified structure and easier manufacturing.

[0014]

In view of the above problems, the present invention has been studied to develop a halftone phase shift photomask that is practical, highly accurate, and easier to manufacture. The inventors have found that the phase shift layer can be composed of one layer, and have completed the present invention based on such findings.

That is, the halftone phase shift photomask of the present invention comprises a transparent substrate and a halftone light shielding layer / phase shift layer made of a uniform composition material provided on the surface of the transparent substrate according to a predetermined pattern. When the wavelength used is λ and the refractive index thereof is n, the film thickness d of the light-shielding layer / phase shift layer is approximately d = λ / {2 (n−
1)} or an odd multiple thereof, and the transmittance is in the range of approximately 5 to 30%.

In this case, the halftone light shielding layer and the phase shift layer are made of CrO _x , CrN _x , CrO _x N _y and CrO _x.
It may be composed of any one of N _y C _z , or may be composed by dispersing a pigment or a dye in a transparent inorganic material or organic material. In the latter case, for example, the halftone light-shielding layer / phase shift layer can be composed of spin-on-glass in which light-shielding fine particles are dispersed.

[0017]

In the present invention, the halftone phase shift photomask is composed of the transparent substrate and the halftone light shielding layer / phase shift layer made of a uniform composition material provided on the surface of the transparent substrate according to a predetermined pattern. Is extremely simple, and by reducing the number of manufacturing steps, the occurrence of defects can be suppressed, and at the same time, the manufacturing cost can be kept low. And, nevertheless, a high resolution that cannot be obtained with a normal photomask, which is a feature of the halftone phase shift photomask, is possible.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the halftone phase shift photomask of the present invention will be described below with reference to FIG. Figure 1
FIG. 3 is a sectional view of a halftone phase shift photomask (reticle) according to the present invention.
It comprises a quartz substrate 10 and a halftone light shielding layer / phase shift layer 11 provided on the surface thereof according to a predetermined pattern. Halftone light shielding layer and phase shift layer 11
Is the film thickness d, where λ is the wavelength used and n is its refractive index.
Is set to be d = λ / {2 (n-1)} or an odd multiple thereof, and the transmittance is set to 5 to 30%. Specifically, for example, the halftone light-shielding layer / phase shift layer 11 uses CrO _x , CrN _x , CrO _x N _y , and CrO _x with chromium as a sputtering target and a gas such as oxygen in the vapor deposition atmosphere. N
It is formed by depositing a chromium oxide such as _y C _z , a nitride, an oxynitride, or an oxynitride carbide on the substrate 10.
The film forming conditions are changed to control the content of chromium with respect to oxygen and the like so that both the film thickness condition and the transmittance condition are satisfied.

Therefore, as described with reference to FIG. 3, the halftone phase shift photomask having such a structure can suppress the spread of the light intensity distribution.
Even fine patterns that could not be decomposed conventionally can be decomposed. Moreover, as is apparent from the cross-sectional view of FIG. 1, the photomask is such that the substrate 10 is coated with a single halftone light-shielding layer / phase shift layer 11 and a resist layer is coated thereon. In the most basic method, a predetermined pattern is drawn by an exposure device such as an electron beam drawing device, developed and rinsed to form a resist pattern, and the layer 11 exposed from the opening of the resist pattern is dry-etched or wet-etched. It can be manufactured by performing the lithography process only once.

The halftone light-shielding layer / phase shift layer 11 is made of a transparent inorganic material or organic material in which pigments and dyes are dispersed in place of the chromium oxide or the like. It can also be configured to be satisfactory.

Next, as one example thereof, an embodiment will be described in which a halftone light shielding layer / phase shift layer is formed by spin-on-glass (SOG). FIG. 2 is a sectional view showing the manufacturing process in this case. First, a halftone phase shift photomask blank as shown in FIG. In the figure, 39 is a substrate, 40 is a conductive layer, 41 is a halftone light-shielding layer and phase shift layer (thickness is about 405 nm for i line, for example, and constitutes a 180 ° phase shifter,
The transmittance is in the range of 5 to 30%). The halftone light-shielding layer / phase shift layer 41 is made of carbon, Si in an SOG solution.
Light-shielding fine particles such as N _x and Si (particle diameter: several to several tens nm)
Are mixed by a dispersion method, spin-coated, and baked to prepare. The amount of light-shielding fine particles such as carbs to be mixed is adjusted while monitoring the transmittance of the fired substrate. In addition, ultrasonic treatment or the like is appropriately performed to uniformly mix. The transmittance is selected in the range of 5 to 30% as described above, but as an example, carbon fine particles are used so as to be about 16%.

Next, a defect inspection of such a halftone phase shift photomask blank is performed, and FIG.
As shown in FIG. 4, an ionizing radiation resist 42 such as chloromethylated polystyrene is uniformly applied thereon by a conventional method such as spin coating, and a heat drying treatment is performed. The heat-drying treatment, depending on the type of resist used, is usually
It is carried out at 80 to 150 ° C. for about 20 to 60 minutes. Next, a pattern is drawn on the resist layer 42 with ionizing radiation by an exposure device such as an electron beam drawing device according to a conventional method, developed with a developing solution containing an organic solvent such as ethyl cellosolve or ester as a main component, and rinsed with alcohol. A resist pattern 43 as shown in FIG.

Next, after heat treatment and discum treatment are carried out as necessary to remove unnecessary resist such as resist scraps and beards remaining on the edge portions of the resist pattern 43, it is shown in FIG. So that the resist pattern 4
The processed portion exposed from the opening of 3, that is, the halftone light shielding layer / phase shift layer 41 is dry-etched by the etching gas plasma 44 to form the halftone phase shifter pattern 45. It is obvious to those skilled in the art that the shifter pattern 45 may be formed by wet etching instead of dry etching by the etching gas plasma 44.

Thereafter, as shown in FIG. 3E, the resist pattern 43, that is, the remaining resist is removed by solvent to form a photomask. After cleaning this photomask,
Inspected, the halftone phase shift photomask having the halftone phase shifter pattern 45 is completed.

As described above, in the case of the halftone phase shifter pattern made of SOG in which the carbon fine particles are dispersed so that the transmittance becomes about 16%, the transmittance of the photomask blanks is an average value ± 3σ (σ is The standard deviation was ± 0.8%. In addition, the positional deviation of the halftone phase shifter of the halftone phase shift photomask manufactured by the process having a small number of steps is ± 3σ (σ is a standard deviation) when the average value is ± 3σ.
It was confirmed that a high-precision halftone phase shift photomask was obtained, showing a value within 0.1 μm, and no pattern distortion or the like was observed.

[0026]

With the recent high integration of LSIs and VLSIs, the precision of photomasks is required more and more, and the mask structure is complicated, and accordingly, the number of processes is increased, and defects such as dust are frequently generated. Is a problem. Also, the cost is inevitably high.

In the present invention, as described above, the halftone phase shift photomask comprises the transparent substrate and the halftone light shielding layer / phase shift layer made of a uniform composition material provided on the surface of the transparent substrate according to a predetermined pattern. Since the structure is used, the structure is extremely simple, and the number of manufacturing steps can be reduced, so that the occurrence of defects can be suppressed, and at the same time, the manufacturing cost can be kept low. And, nevertheless, a high resolution that cannot be obtained with a normal photomask, which is a feature of the halftone phase shift photomask, is possible.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a halftone phase shift photomask according to the present invention.

FIG. 2 is a sectional view showing an example of a manufacturing process of a halftone phase shift photomask of the present invention.

FIG. 3 is a diagram showing the principle of halftone phase shift lithography.

FIG. 4 is a diagram showing a conventional method.

FIG. 5 is a cross-sectional view showing a manufacturing process of a conventional halftone phase shift photomask.

[Explanation of symbols]

 10 ... Quartz substrate 11 ... Halftone light shielding layer / phase shift layer 39 ... Substrate 40 ... Conductive layer 41 ... Halftone light shielding layer / phase shift layer 42 ... Ionizing radiation resist 43 ... Resist pattern 44 ... Etching gas plasma 45 ... Halftone phase Shifter pattern

Claims (4)

[Claims] 1. A transparent substrate and a halftone light-shielding layer / phase shift layer made of a uniform composition material provided on a surface of the substrate in accordance with a predetermined pattern. When λ and its refractive index are n, the film thickness d is set to be approximately d = λ / {2 (n-1)} or an odd multiple thereof, and the transmittance is approximately 5 to 30. %, A halftone phase shift photomask, which is configured to have a range of%. 2. The halftone light-shielding layer / phase shift layer comprises CrO _x , CrN _x , CrO _x N _y , and CrO _x N _y.
The halftone phase shift photomask according to claim 1, wherein the halftone phase shift photomask is composed of any one of C _z . 3. The halftone phase shift photomask according to claim 1, wherein the halftone light shielding layer / phase shift layer is formed by dispersing a pigment or a dye in a transparent inorganic material or an organic material. .. 4. The halftone phase shift photo according to claim 3, wherein the halftone light-shielding layer / phase shift layer is composed of spin-on-glass in which light-shielding fine particles are dispersed. mask.