JPH11143050A - Photomask and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photomask which allows inspection by a data base system and is optimum for application to a logic system device and a process for producing the same. SOLUTION: A main pattern 11 by a light shielding film 22 and auxiliary patterns 12 by translucent films which have a specified light shielding effect to exposure light and are constant in transmittance to inspection light at the time of mask inspection are formed on a photomask substrate 20. The photomask obtd. in such a manner allows the mask inspection by the data base system. Since the change in the shape and dimension by an optical proximity effect may be prohibited, the photomask is optimum for the application to the logic system device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a photomask for projection exposure, and more particularly to a photomask used for forming a fine pattern in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art At present, in a manufacturing process of a semiconductor device, optical lithography is mainly used for forming a pattern on a semiconductor substrate. In optical lithography, a predetermined pattern is obtained by transferring a pattern of a photomask on a semiconductor substrate coated with a resist by a reduction projection exposure apparatus and developing the photomask. In response to recent miniaturization of semiconductor element patterns, various development studies have been made on this optical lithography technology, and in particular, regarding an exposure apparatus, the NA of a projection lens has been increased. NA (numerical aperture) is a numerical value related to the radius of the aperture of the projection lens. The larger the numerical value, the higher the resolution and the brighter the image. However, since the depth of focus is reduced at the same time, there is a problem that a slight shift of the focal position cannot be tolerated.

Therefore, a technique for controlling the transmittance and the phase on the pupil plane of the illumination optical system, the photomask, and the projection lens system, that is, a super-resolution technique has been studied. Above all, attention has been paid to a method of improving resolution characteristics by optimizing an illumination optical system, a so-called modified illumination method. The deformed illumination method is a name derived from deforming the shape of an effective light source for illuminating a photomask, and uses various shapes of apertures or filters as a means for that. By these actions, the photomask is illuminated with light of a specific incident angle, and as a result, there is an effect of increasing the depth of focus for a periodic pattern in which diffracted light is generated.

However, the modified illumination method has no effect on isolated patterns. Therefore, a method of arranging a fine auxiliary pattern around such an isolated pattern is disclosed in, for example, Japanese Patent Application Laid-Open No. 4-268714. According to this method, the isolated main pattern and the newly provided auxiliary pattern form the same pattern configuration as the above-described periodic pattern, and the effect of increasing the depth of focus can be obtained. Further, since the auxiliary pattern is very fine and does not itself form an image on the semiconductor substrate, it is excellent in that it has no influence on the main pattern transfer process.

However, with the miniaturization of semiconductor element patterns, difficulties have arisen in the fabrication of photomasks. First, as described above, it is important that the auxiliary pattern does not form an image itself, and the auxiliary pattern must be smaller than the main pattern. As a result, the required dimensions have been reduced to one micron or less, or even smaller, and are now approaching the limits of manufacturing. Furthermore, the influence of the optical proximity effect caused by the dimensional difference between the main pattern and the auxiliary pattern has also been a problem. The optical proximity effect is a phenomenon in which the size or shape of a certain pattern changes due to the influence of a peripheral pattern. At the time of manufacturing with a mask drawing apparatus, particularly an electron beam drawing apparatus, the size of the auxiliary pattern is reduced due to the optical proximity effect,
As a result, there is a problem in that the effect of increasing the depth of focus is lost.

There is also a problem in the mask inspection process. Generally, the mask inspection method includes a die-to-die (d
ie to die) system and a database system. In the die-to-die method, when the same pattern is arranged on one photomask, the patterns are compared with each other. In this method, a dimensional error of a fine auxiliary pattern is detected as a defect.
Further, a fine pattern is easily affected by a batting error when moving a mask stage in writing by an electron beam lithography apparatus, and accurate inspection is more and more difficult.
The database type inspection is an inspection method for comparing mask design data with an inspection image of a manufactured photomask pattern, and is applied to a random pattern, for example, a logic device. A dimensional error caused by the proximity effect was detected as a defect, and application was difficult.

On the other hand, in Japanese Patent Application Laid-Open No. 9-073166, by setting the transmittance of the auxiliary pattern to about 40 to 80%, even if the auxiliary pattern has the same size as the main pattern, it is not transferred onto the semiconductor substrate. Is disclosed. The manufacturing method is shown in FIG. 4 and described in detail below. As shown in FIG. 4A, a translucent film 21 having a transmittance of about 40 to 80% is formed on a mask substrate 20.
Then, the light shielding film 22 is sequentially formed. Then, FIG.
As shown in (d), the light-shielding film 22 and the translucent film 21 are etched using the resist 23 to process a predetermined auxiliary pattern. Next, as shown in FIGS. 4E and 4F, the translucent film 21 of the main pattern portion is selectively removed.

As a material, the permeable film 22 has a thickness of 100
For the chromium of 21 nm and the translucent film 21, a thin film of molybdenum silicide having a thickness of 20 to 30 nm is used. These materials are conventionally used as photomask materials and are easy to form and etch. According to this method, a photomask having the same dimensions of the main pattern and the auxiliary pattern and having no influence of the optical proximity effect, that is, a photomask having high dimensional accuracy was obtained. In addition, this photomask was easy to perform a die-to-die type mask inspection.

[0009]

However, the above-mentioned photomask has a problem in that it is difficult to perform a database-based inspection. In the database system, mask design data serving as a comparison reference is CAD or format data unique to a mask drawing apparatus. In this data, both the main pattern and the auxiliary pattern are treated as transparent parts, and are recognized as having the same size. On the other hand, the inspection image of the photomask pattern is
When the pit map data is captured by the sub pattern, the auxiliary pattern formed by the translucent film has a different light intensity, so that the size of the main pattern is slightly different from that of the auxiliary pattern. Therefore, it was impossible to simply compare the mask design data with the pit map data. That is, it is difficult to apply the photomask to a logic device inspected by a database method.

It is an object of the present invention to provide a photomask which can be inspected by a database system and which is most suitable for application to a logic device, and a method of manufacturing the same.

[0011]

In order to solve the above-mentioned problems, a photomask of the present invention has a light-shielding film, a light-shielding effect on exposure light, and a light-shielding effect on inspection light, on a transparent substrate. And a translucent film that is transparent.

Further, the photomask of the present invention comprises, on a transparent substrate, a light-shielding film and a translucent film having a transmittance of 80% or less for exposure light and 90% or more for inspection light. It is characterized by becoming.

Further, the photomask of the present invention is characterized in that it comprises a main pattern formed by a light-shielding film and an auxiliary pattern formed by a translucent film.

Further, the photomask of the present invention is formed by a step of sequentially forming a translucent film and a light-shielding film on a transparent substrate, a step of etching predetermined portions of the light-shielding film and the translucent film, and an etching step. Inspecting and correcting the pattern, selectively removing only the light-shielding film of a predetermined portion of the pattern, and inspecting and correcting the pattern formed by the selective removal again. It is characterized by the following.

Further, the photomask of the present invention is characterized by comprising a semi-transparent film of a metal oxide such as tin oxide, indium oxide, ITO, alumina or hafnia.

Further, in the method of manufacturing a photomask according to the present invention, a light-shielding film and a translucent film having a constant light-shielding effect for exposure light and being transparent to inspection light are formed on a transparent substrate. It is characterized by forming.

Further, according to the method for manufacturing a photomask of the present invention, a light-shielding film and a translucent film having a transmittance of 80% or less for exposure light and 90% or more for inspection light are formed on a transparent substrate. Are formed.

Further, the method of manufacturing a photomask according to the present invention is characterized in that a main pattern is formed by a light-shielding film and an auxiliary pattern is formed by a translucent film.

The method for manufacturing a photomask according to the present invention comprises the steps of sequentially forming a translucent film and a light-shielding film on a transparent substrate, etching a predetermined portion of the light-shielding film and the translucent film, Inspecting and correcting the pattern formed by the method, selectively removing only the light-shielding film of a predetermined portion of the pattern, and inspecting and correcting the pattern formed by the selective removal again. It is characterized by consisting of.

The method of manufacturing a photomask according to the present invention is characterized in that a semi-transparent film of a metal oxide such as tin oxide, indium oxide, ITO, alumina or hafnia is formed.

The operation of the present invention will be described. FIG. 1 shows the relationship between the wavelength and the transmittance of a synthetic quartz on which a translucent film of tin oxide (SnO ₂ ) having a thickness of 15 nm was formed, where the transmittance of only the substrate was 100%. Generally, oxides, nitrides, and oxynitrides of metals and silicide materials have low transmittance on the short wavelength side and high transmittance on the long wavelength side. Again, 50% is used for a KrF excimer laser beam having a wavelength of 248 nm (representative exposure light), while 90% or more is used for a wavelength of 300 nm or more, and an Ar laser beam having a wavelength of 488 nm (representative light). 96% of the light (except for the mask inspection light). Therefore, the auxiliary pattern formed by such a translucent film is not developed on the semiconductor surface at the time of exposure as in the conventional case, but is recognized as a transparent portion at the time of taking in the pit map data. That is, since the comparison between the mask design data and the pit map data can be accurately performed, an inspection in a database format can be performed.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention is shown in FIG. 2 and described below. As shown in FIG. 2A, the main pattern 11 is an isolated pattern, and auxiliary patterns 12 of the same size are arranged on the left and right sides. FIG. 2B shows an AA ′ cross section of FIG. A translucent film 21 is formed on a transparent substrate 20 made of synthetic quartz, and a light-shielding film 22 is further formed thereon. The main pattern 11 is a laminate of the translucent film 21 and the light-shielding film 22, and the auxiliary pattern 12 is formed of the translucent film 21 only. The manufacturing method may be the same as the conventional method shown in FIG. 4, and the light-shielding film 22 may be a commonly used material such as chromium or chromium oxide, but the translucent film 21 uses tin oxide. As described above, since tin oxide exhibits a transmittance of 50% for the exposure light of the exposure apparatus and a transmittance of 95% for the mask inspection light, it is possible to perform a database-type mask inspection. It is.

Further, as a material of the translucent film 21, another metal and a refractory metal silicide exhibiting the same effect and oxides, nitrides and nitrided oxides thereof may be used. Especially i
Materials used as an etching stopper of a phase shift mask for a line (wavelength: 365 nm), that is, indium oxide, ITO, alumina, hafnia and the like can all be used as a material of the translucent film 21.

Next, a second embodiment of the present invention is shown in FIG. As shown in FIG. 3A, the main pattern 1
Reference numeral 1 denotes a line pattern adjacent in a T-shape, and an auxiliary pattern 12 is arranged at the end of the line. The manufacturing method and materials are the same as those of the above-described embodiment, and a database-type mask inspection can be performed. Further, in the present embodiment, the auxiliary pattern 12 made of the translucent film 21 also has an effect of reducing the exposure amount at the line tip and preventing the line tip from shrinking in dimension. That is, by applying the present invention to a portion where a change in shape or size due to the optical proximity effect is likely to occur, the present invention also has an effect of preventing this.

[0025]

As described above, according to the present invention, in a photomask using a translucent film as an auxiliary pattern, a database-type mask inspection can be performed. Further, at the same time, it is possible to prevent a change in the shape and dimensions due to the optical proximity effect, so that it is most suitable for application to logic devices.

[Brief description of the drawings]

FIG. 1 is a diagram showing data for explaining the operation of the present invention.

FIG. 2 is an explanatory diagram showing an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a second embodiment of the present invention.

FIG. 4 is an explanatory diagram for explaining a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Main pattern 12 Auxiliary pattern 20 Photomask substrate 21 Translucent film 22 Light shielding film 23 Resist

Claims (10)

[Claims] 1. A photomask comprising, on a transparent substrate, a light-shielding film and a translucent film having a constant light-shielding effect for exposure light and being transparent to inspection light. . 2. A light-shielding film, comprising: a transparent substrate; and a translucent film having a transmittance of 80% or less for exposure light and 90% or more for inspection light. The photomask according to claim 1. 3. The photomask according to claim 1, further comprising: a main pattern formed by a light-shielding film; and an auxiliary pattern formed by a translucent film. 4. A step of sequentially forming a translucent film and a light-shielding film on a transparent substrate, a step of etching predetermined portions of the light-shielding film and the translucent film, and inspecting and correcting a pattern formed by the etching. A step of selectively removing only a light-shielding film in a predetermined portion of the pattern, and a step of again inspecting and correcting the pattern formed by the selective removal. 1
4. The photomask according to any one of Items 1 to 3. 5. The photomask according to claim 1, further comprising a translucent film of a metal oxide such as tin oxide, indium oxide, ITO, alumina or hafnia. 6. A photomask comprising a light-shielding film and a translucent film having a constant light-shielding effect on exposure light and being transparent to inspection light, on a transparent substrate. Production method. 7. A light-shielding film and a translucent film having a transmittance of 80% or less for exposure light and 90% or more for inspection light are formed on a transparent substrate. Item 6
3. The method for manufacturing a photomask according to 1. 8. A main pattern is formed by a light shielding film,
8. The method for manufacturing a photomask according to claim 6, wherein the auxiliary pattern is formed by a translucent film. 9. A step of sequentially forming a translucent film and a light-shielding film on a transparent substrate, a step of etching predetermined portions of the light-shielding film and the translucent film, and inspecting and correcting a pattern formed by the etching. 7. The method according to claim 6, further comprising the steps of: performing a step of selectively removing only a light-shielding film in a predetermined portion of the pattern; and inspecting and correcting the pattern formed by the selective removal again. 10. The method for manufacturing a photomask according to any one of items 9 to 9. 10. Tin oxide, indium oxide, ITO,
The method for manufacturing a photomask according to any one of claims 6 to 9, wherein a translucent film of a metal oxide such as alumina or hafnia is formed.