JP2010204264A - Method for manufacturing photomask having patterns on both surfaces thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a double-sided photomask, wherein there is not risk that a light shielding pattern on a front surface is damaged by abnormal discharge when a light shielding film is formed on a rear surface after formation of the light shielding pattern on the front surface. <P>SOLUTION: The method for manufacturing a double-sided photomask includes: a process of removing a first resist film on the outer edge part of a transparent substrate to expose a first light shielding film in the outer edge part after forming the first light shielding film and the first resist film in order on one principal surface of the transparent substrate; a process of patterning and developing the first resist film and etching the first light shielding film and peeling the first resist film to form a first light shielding pattern; and a process of forming a second light shielding film and a second resist film in order on the other principal surface of the transparent substrate and patterning and developing the second resist film and then etching the second light shielding film and peeling the second resist film to form a second light shielding pattern. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a photomask having different light shielding patterns on two opposing main surfaces of a transparent substrate, and in particular, after forming a light shielding pattern on one surface of a transparent substrate, the light shielding pattern is damaged. The present invention relates to a method for manufacturing a photomask for manufacturing a different light shielding pattern on the other surface of a transparent substrate.

  A photomask (also referred to as a reticle) used as an original plate when projecting and transferring a semiconductor circuit onto a wafer is generally provided with a light-shielding pattern made of a metal such as chromium on one main surface of a transparent substrate such as quartz glass. It has a formed structure. In recent years, in order to further improve the optical characteristics of the projection exposure apparatus and realize finer processing, the light shielding pattern is referred to as one opposing main surface (hereinafter also referred to as “surface” in the present invention) of the transparent substrate. There has been proposed a double-sided photomask formed on both surfaces on the two main surfaces of the other main surface (hereinafter also referred to as “back surface” in the present invention) (see, for example, Patent Document 1).

  As a manufacturing method of a double-sided photomask, a method using a double-sided blank with a light-shielding film formed on both sides of a transparent substrate as a starting material and a single-sided blank with a light-shielding film formed on one side of a transparent substrate as a starting material There is a method to use. Since single-sided blanks are the same as conventional photomask blanks, they are usually of high quality, reliable and inexpensive, and therefore single-sided blanks are usually used as a starting material in the manufacture of double-sided photomasks (see, for example, Patent Document 2). ).

JP 2006-80444 A JP 2006-285122 A

  However, in the conventional method using single-sided blanks described in Patent Document 2 as a starting material, after the light-shielding film on one surface is patterned to form a light-shielding pattern, the light-shielding film is formed on the other surface by sputtering or the like. When filming, abnormal discharge often occurs, which damages the already formed light-shielding pattern on one side, resulting in a defect in appearance of the double-sided photomask. Therefore, when the light-shielding pattern on one surface is damaged, it has to be re-created from the formation of the light-shielding film on the surface again, resulting in an increase in mask manufacturing time and manufacturing cost.

  Therefore, the present invention has been made in view of the above problems. That is, an object of the present invention is to cause damage to the light-shielding pattern on the surface side due to abnormal discharge when forming a light-shielding film on the back surface after forming the light-shielding pattern on the front surface in the method for producing a double-sided photomask. It is an object of the present invention to provide a method for manufacturing a double-sided photomask that does not have any.

  In order to solve the above problems, a method for producing a double-sided photomask according to the invention of claim 1 of the present invention is such that a first light-shielding pattern is formed on one main surface of a transparent substrate, and then the transparent substrate. A method for producing a double-sided photomask in which a second light-shielding pattern is formed on the other principal surface of the transparent substrate and the light-shielding pattern is provided on both principal surfaces of the transparent substrate. Forming one light-shielding film and a first resist film in order, then removing the first resist film at the outer edge of the transparent substrate and exposing the first light-shielding film at the outer edge of the transparent substrate; The first resist film is pattern-drawn by a drawing device, developed, the exposed first light-shielding film is etched, the first resist film is peeled off, and one main surface of the transparent substrate A main surface pattern made of the first light-shielding film and a surface pattern are formed on the surface. Forming a first light-shielding pattern having an element mark, and sequentially forming a second light-shielding film and a second resist film on the other main surface of the transparent substrate, Patterning and developing the film, etching the exposed second light-shielding film, and then peeling off the second resist film to form a back surface alignment mark made of the second light-shielding film; A step of measuring a deviation amount based on the front surface alignment mark and the rear surface alignment mark, a third resist film is formed on the other main surface of the transparent substrate, and the deviation amount is corrected by a drawing apparatus. The third resist film is patterned, developed, and the exposed second light-shielding film is etched, and then the third resist film is peeled off to form a back surface book made of the second light-shielding film. Forming a turn and is characterized in that it comprises a step of forming a second light-shielding pattern having said rear surface present pattern on the other main surface of the transparent substrate and the back surface alignment mark.

  The method for producing a double-sided photomask according to the invention of claim 2 is the method for producing a double-sided photomask according to claim 1, wherein the removal of the first resist film on the outer edge of the transparent substrate is performed by the first method. While maintaining and rotating the transparent substrate on which the resist film is formed, a solvent or a developer for dissolving the first resist film is supplied to the outer edge portion of the transparent substrate, and the outer edge portion of the transparent substrate is The first resist film is dissolved and scattered to be removed.

  According to the method for manufacturing a double-sided photomask of the present invention, a first light-shielding film and a first resist film are sequentially formed on the surface of a transparent substrate, and then the first resist film on the outer edge portion of the transparent substrate is removed. As a result, during the pattern etching of the first light-shielding film, the light-shielding film on the outer edge portion of the transparent substrate including the end face is simultaneously etched away, and when the second light-shielding film is formed on the back surface by sputtering, The high-quality double-sided photomask eliminates the problem peculiar to the fabrication of the double-sided photomask that the first light-shielding pattern on the surface that has already been formed is damaged by the abnormal discharge caused by the conduction of the light-shielding film. Can be produced.

It is process cross-sectional schematic diagram which shows an example of the preparation methods of the double-sided photomask of this invention. It is process cross-sectional schematic diagram which shows an example of the preparation methods of the double-sided photomask of this invention following FIG.

  Hereinafter, the best embodiment of the method for producing a double-sided photomask of the present invention will be described in detail with reference to the drawings. FIG. 1 and subsequent FIG. 2 are process cross-sectional schematic diagrams showing an example of a method for producing a double-sided photomask of the present invention.

  As shown in FIG. 1, after the first light shielding film 11 (FIG. 1A) and the first resist film 12 are formed in this order on one main surface (front surface) of the cleaned transparent substrate 10. (FIG. 1B), the first resist film 12 on the outer edge 13 of the transparent substrate 10 is removed to expose the first light-shielding film 11 on the outer edge 13 (FIG. 1C).

  In the present invention, the transparent substrate 10 is preferably a synthetic quartz substrate used as a photomask substrate with a fine pattern. Further, as the first light shielding film 11, for example, a single layer or two or more kinds of various thin films such as chromium, chromium oxide, and chromium nitride used as a light shielding film for a photomask can be applied. Form a film. Further, as the first resist film 12, a photomask electron beam resist or a laser exposure resist is used, which is applied and formed by a method such as spin coating.

  In the present invention, any method can be applied to the removal of the first resist film 12 applied to the outer edge portion 13 as long as the resist film 12 is removed and the photomask fabrication is not hindered. While holding and rotating the transparent substrate 10 on which the first resist film 12 is formed, a solvent for dissolving the first resist film 12 or a developer dedicated to the resist film is supplied to the outer edge portion 13 of the transparent substrate, It is more preferable to use a method in which the first resist film 12 is dissolved, scattered and removed, in order to reduce the possibility of foreign matters adhering to the surface of the first resist film 12 in order to manufacture a high-quality photomask.

  As a means for supplying the solvent or developer to the outer edge portion 13 of the transparent substrate, for example, a method in which the solvent or developer does not come into contact with the resist film of the main part of the transparent substrate and is discharged using a nozzle or the like is used. It is done.

  Any solvent can be used as the solvent for dissolving the first resist film 12 as long as the resist film 12 can be dissolved. For example, acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl cellosolve acetate and the like are candidates for the solvent. Can be mentioned.

  Further, in the present invention, when the first resist film 12 on the outer edge portion 13 of the transparent substrate is dissolved and scattered, the number of rotations for rotating the transparent substrate 10 and the flow rate of the supplied solvent or developer are as follows. Appropriate conditions are determined and determined according to the material, viscosity, film thickness, type of solvent or developer, dissolution rate of the resist film 12, and the like.

  In the present invention, the outer edge portion 13 of the transparent substrate indicates a region having a width of about 2 mm including the end surface from the end surface of the transparent substrate 10. If the outer edge portion from which the first resist film 12 is removed has a distance from the end surface exceeding about 2 mm in width, there is a risk of hindering the formation of the main surface pattern and the surface alignment mark made of the first light shielding film described later. Because.

  Next, a pattern having a main surface pattern and a surface alignment mark is drawn on the first resist film 12 by an electron beam (hereinafter also referred to as EB) or laser light 14 (FIG. 1D). )). If a double-sided mask aligner is used when forming a back surface alignment mark described later, a double-sided aligner mark is drawn in advance at the time of drawing. Since the surface pattern drawing requires a fine pattern and pattern accuracy, an electron beam drawing apparatus or a laser drawing apparatus is usually used.

  After drawing, the first resist film 12 is developed with a predetermined developer to form a first resist pattern 15 (FIG. 1E). Next, the exposed first light-shielding film 11 is etched, the first resist pattern 15 is peeled off, and a first light-shielding pattern having a main surface pattern 16 and a surface alignment mark 17 made of the first light-shielding film ( A surface pattern 18 is formed (FIG. 1 (f)). In the etching process for forming the first light shielding pattern 18, the exposed first light shielding film 11 of the outer edge portion 13 is simultaneously etched away, and the light shielding film 11 is formed on the outer edge portion 13 including the end face of the transparent substrate 10. A form in which is not left is obtained.

As the etching of the light shielding film 11, either wet etching or dry etching can be applied. However, dry etching is more preferable from the viewpoint of forming a fine pattern. For example, when the light shielding film is chromium, a mixed gas of Cl ₂ and O ₂ is used.
The first resist pattern 15 can be peeled by either a dry process that peels off using oxygen plasma or a wet process that peels off using a resist-dedicated stripping solution.

  Here, as a method for removing the light shielding film from the outer edge, when the light shielding film is formed by sputtering, the peripheral part of the transparent substrate is masked in advance, and the light shielding film is not formed on the peripheral part of the transparent substrate. It has been. However, when using a photomask blank that does not have a light-shielding film at the periphery of the transparent substrate, there is no conductive light-shielding film such as chrome at the outer edge, so that the outer edge can be grounded when drawing an electron beam. (Earth pin cannot be used because the pattern drawing area is scratched, and the entire mask is charged up, interacts with the negatively charged electron beam, the electron beam trajectory shifts, and the drawing pattern is distorted) There arises a problem that a good fine pattern cannot be obtained. Therefore, a method for producing a double-sided photomask using a photomask blank having no light shielding film around the transparent substrate as a starting material is not desirable.

  In the present invention, of two opposing main surfaces of the transparent substrate 10, one main surface is referred to as a front surface and the other main surface is referred to as a back surface. Means the light source side, and usually a finer pattern is formed on the surface side. In the present invention, the term “pattern” refers to a pattern that is exposed and transferred when a double-sided photomask is used as a photomask, and is distinguished from a pattern such as an alignment mark. In order to improve alignment accuracy, it is preferable to provide two or more alignment marks on one main surface of both the front and back surfaces.

  Next, the second light-shielding film 21 is formed on the other main surface (back surface) opposite to the side on which the first light-shielding pattern 18 is formed on the transparent substrate by a film-forming method such as sputtering (FIG. 1 ( g)). FIG. 1 (g) is shown upside down with respect to FIG. 1 (f).

  Next, a second resist film 22 is formed on the second light-shielding film 21, and a second pattern for forming a back surface alignment mark on the second resist film 22 with an electron beam, laser light, or ultraviolet light 23. Drawing is performed (FIG. 2 (h)).

  After drawing, development is performed to form a second resist pattern 24 for a back surface alignment mark for measuring the amount of misalignment (FIG. 2 (i)).

  Next, the exposed second light shielding film 21 is etched, the second resist pattern 24 is peeled off, and a back surface alignment mark 25 is formed on the second light shielding film 21 (FIG. 2 (j)). FIG. 2J shows two back surface alignment marks 25. Here, the back surface alignment mark 25 can also be used as the EB drawing alignment mark used in the electron beam drawing step of the back side main pattern in the subsequent steps. Usually, the drawing apparatus is dedicated to each apparatus. Since an alignment mark shape is required, it is preferable to separately draw and form a dedicated EB drawing alignment mark (not shown) in order to improve drawing accuracy. For the drawing of the back surface alignment mark 25, drawing by an electron beam drawing apparatus or a laser drawing apparatus, or transfer exposure using a photomask provided with an alignment mark by a double-sided mask aligner is used.

  In the present invention, in pattern drawing of the back surface alignment mark 25, when a substrate on which a resist film is formed on the back surface is set for drawing in a drawing apparatus, it is not necessary to position it strictly, and it can be set with a register. It is drawn at a position that almost overlaps when viewed from the direction. That is, even if set with the register, the dimensional relationship is such that the back surface alignment mark 25 and the front surface alignment mark 17 are substantially overlapped. According to such a setting method, a positional deviation of several hundred μm occurs. However, it is only necessary to design the alignment mark in consideration of the deviation amount.

  Next, by observing the front surface alignment mark 17 and the back surface alignment mark 25 from the vertical direction with an optical microscope or the like, the amount of misalignment is measured, and in the x and y directions when the main pattern on the back surface is drawn. The parallel movement correction amount and the rotational movement correction amount in the θ direction are obtained in advance.

  If the amount of deviation between the front and back alignment marks is within a predetermined value, the process proceeds to the next step, and the third resist film 26 is formed on the second light-shielding film 21 on which the back surface alignment mark 25 is formed. The measured deviation amount is corrected, and the back side main pattern is drawn by the electron beam or the laser beam 27 (FIG. 2 (k)). Next, the third resist film 26 is developed with a predetermined developer to form a third resist pattern 28 for the back main pattern (FIG. 2L).

  In the above measurement of the amount of misalignment, if the amount of misalignment between the front and back alignment marks exceeds a predetermined value, the second light shielding film 21 on which the back surface alignment mark 25 is formed is peeled off, and the above FIG. Returning to the process, the process after the process of forming the second light shielding film 21 on the back surface of the transparent substrate 10 is performed again.

  Next, after etching the second light shielding film 21 exposed from the third resist pattern 28 for the back main pattern, the third resist pattern 28 is peeled off to form the back main pattern 29, A double-sided photomask 31 is obtained in which a second light-shielding pattern (back surface pattern) 30 having a back surface main pattern 29 and a back surface alignment mark 25 is formed on the other main surface (back surface) (FIG. 2 (m)).

  In the present invention, as the front and back patterns, not only the front and back main patterns and the front and back alignment marks, or the alignment marks for EB drawing, but also a pattern for inspection and measurement can be provided in the non-transfer area.

  In the above description, the first resist film 12, the second resist film 22, and the third resist film 26 may all be formed of the same type of resist, or may be two or three different resists. However, in order to simplify the manufacturing process, it is preferable to use the same type of resist.

  The first light-shielding film 11 and the second light-shielding film 21 may be the same kind of light-shielding film, or two or more different light-shielding films may be used, but in order to simplify the manufacturing process. It is preferable to use the same kind of light-shielding film for all.

  As described above, the photomask manufacturing method of the present invention is a method of forming different patterns on the front and back surfaces of the photomask. The first light-shielding film and the first resist film are sequentially formed on the surface of the transparent substrate. After the formation, by removing the first resist film at the outer edge portion of the transparent substrate, the light shielding film at the outer edge portion of the transparent substrate including the end face is also etched away at the time of pattern etching of the first light shielding film, When the second light-shielding film is formed on the back surface by sputtering, the first light-shielding pattern on the surface that has already been formed is prevented from being damaged due to abnormal discharge caused by conduction of the light-shielding films on the front and back surfaces. This is a manufacturing method that makes it possible to manufacture a double-sided photomask.

The photomask manufacturing method of the present invention can be applied even when the first light-shielding film has a phase shift film, and the first light-shielding film has light transmittance at the exposure wavelength. The present invention can also be applied to a halftone semi-transparent light-shielding film having a thickness of 5 to 40%. Further, the photomask manufacturing method of the present invention can be applied even if the photomask has a diffractive optical element such as CGH (Computer Generated Hologram) on the incident light side of the transparent substrate. is there.
Hereinafter, the present invention will be described in detail by way of examples.

The optically polished 6-inch square, 0.25-inch thick synthetic quartz substrate was cleaned, and chromium was formed on one main surface (surface) as a first light-shielding film to a thickness of 60 nm under the following conditions. A film was formed. Chromium was formed on the entire surface of the transparent substrate and thinly on the end surface.
<Sputtering conditions for light shielding film>
Film forming apparatus: Planar type DC magnetron sputtering apparatus Target: Metal chromium gas and flow rate: Argon gas 50 sccm
Sputtering pressure: 0.3 Pascal sputtering current: 3.5 Ampere

  Next, a first electron beam resist is applied to a thickness of 300 nm on the first light-shielding film, and then the synthetic quartz substrate on which the first resist film is formed is held horizontally and spin rotated. Then, the developing solution of the first electron beam resist is supplied to the outer edge portion with a nozzle, and the first resist film is dissolved and scattered to be removed, and the first edge width including the end face of the transparent substrate is reduced to 2 mm. The light shielding film chrome was exposed.

  Next, after prebaking the first electron beam resist, pattern exposure was performed with an electron beam drawing apparatus and development was performed to form a first resist pattern having a desired shape.

Next, using the first resist pattern as a mask, the light-shielding film chrome exposed from the resist pattern was dry-etched under the following conditions and patterned by a dry etching apparatus. At this time, the light shielding film chrome on the outer edge of the substrate including the exposed end face was also etched at the same time.
<Light-shielding film chromium etching conditions>
Etching gas Cl ₂ + O ₂ gas (2: 3)
Pressure 10mTorr
ICP power (high density plasma generation) 500W
Bias power (drawer power) 25W

  Next, the resist pattern was peeled off by oxygen plasma to form a first light-shielding pattern (surface pattern) having a main surface pattern made of light-shielding film chrome and two surface alignment marks.

  Next, on the other main surface (back surface) of the transparent synthetic quartz substrate, chromium is formed by sputtering to a thickness of 60 nm under the same conditions as those for forming the front surface chromium, thereby forming a second light-shielding film. did.

  Next, the same electron beam resist as described above is applied to the second light-shielding film chrome to a thickness of 300 nm, and after pre-baking, pattern exposure is performed with an electron beam drawing apparatus, development, and two back surface alignment marks are formed. A resist pattern was formed.

  Next, using the resist pattern as a mask, the light shielding film chrome exposed from the resist pattern by a dry etching apparatus is dry-etched under the same etching conditions as those for the first light shielding film chrome. The resist pattern was peeled off with oxygen plasma to form a back surface alignment mark on the second light shielding film.

  Next, based on the front surface alignment mark and the back surface alignment mark, the amount of positional deviation between the front and back alignment marks was measured. The deviation amount is within a predetermined value, and movement correction amounts in the x, y, and θ directions were obtained.

  Next, the same electron beam resist as described above is applied to a thickness of 300 nm on the second light-shielding film chrome on which the back surface alignment mark is formed, and after pre-baking, the above-mentioned measured deviation amount is corrected and electron beam drawing is performed. Pattern exposure was performed with an apparatus, development was performed, and a third resist pattern for the back main pattern was formed.

  Next, the second light-shielding film chrome exposed from the third resist pattern is dry-etched under the same etching conditions as those for the first light-shielding film chrome, and then the third resist pattern is stripped with oxygen plasma. Then, a second light-shielding pattern (back surface pattern) having a back main pattern and a back surface alignment mark was formed, and a double-sided photomask having different patterns on the front and back surfaces of a transparent synthetic quartz substrate was produced.

  The method for producing a double-sided photomask according to this example is such that when the second light-shielding film chrome is formed on the back surface by sputtering, abnormal discharge due to conduction of the light-shielding films on the front and back surfaces does not occur. A quality double-sided photomask could be produced.

DESCRIPTION OF SYMBOLS 10 Transparent substrate 11 1st light shielding film 12 1st resist film 13 Outer edge part 14 Electron beam or laser beam 15 1st resist pattern 16 Surface main pattern 17 Surface alignment mark 18 1st light shielding pattern 21 2nd light shielding film 22 Second resist film 23 Electron beam or laser beam or ultraviolet ray 24 Second resist pattern 25 Back surface alignment mark 26 Third resist film 27 Electron beam or laser beam 28 Third resist pattern 29 Back surface main pattern 30 Second Shading pattern 31 Double-sided photomask

Claims (2)

A first light-shielding pattern is formed on one main surface of the transparent substrate, then a second light-shielding pattern is formed on the other main surface of the transparent substrate, and the light-shielding patterns are formed on both main surfaces of the transparent substrate. A method for producing a provided double-sided photomask,
After sequentially forming a first light-shielding film and a first resist film on one main surface of the transparent substrate, the first resist film on the outer edge of the transparent substrate is removed, and the outer edge of the transparent substrate Exposing the first light-shielding film of
The first resist film is pattern-drawn by a drawing apparatus, developed, and the exposed first light-shielding film is etched, and then the first resist film is peeled off, on one main surface of the transparent substrate Forming a first light-shielding pattern having a main surface pattern made of the first light-shielding film and a surface alignment mark;
A second light-shielding film and a second resist film are sequentially formed on the other main surface of the transparent substrate, and the second resist film is pattern-drawn by a drawing apparatus, developed, and exposed. Etching the film, and then peeling the second resist film to form a back surface alignment mark made of the second light shielding film;
Measuring the amount of deviation based on the front surface alignment mark and the back surface alignment mark;
A third resist film is formed on the other main surface of the transparent substrate, and the third resist film is pattern-drawn by correcting the shift amount by a drawing apparatus, developed, and exposed. After etching the light shielding film, the third resist film is peeled off to form a back main pattern made of the second light shielding film, and the back main pattern and the back surface are formed on the other main surface of the transparent substrate. Forming a second light-shielding pattern having an alignment mark;
A method for producing a double-sided photomask, comprising:   The removal of the first resist film on the outer edge portion of the transparent substrate is a solvent that dissolves the first resist film while horizontally holding and rotating the transparent substrate on which the first resist film is formed. 2. The double-sided photomask according to claim 1, wherein a developer is supplied to an outer edge portion of the transparent substrate, and the first resist film on the outer edge portion of the transparent substrate is dissolved and scattered to be removed. Manufacturing method.

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