JP5347360B2 - Method for producing photomask having pattern on both sides - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a double-sided mask which allows easy repairing, when there is a misalignment in the production of a double-sided mask, without giving damages to a top face pattern which has been preliminarily produced. <P>SOLUTION: The method for manufacturing a photomask having different patterns on the top and the back faces of a transparent substrate comprises: forming a top face pattern comprising a light-shielding film on one major surface of the transparent substrate; forming a back face alignment mark comprising a resist film on the other major surface of the transparent substrate; measuring the amount of misalignment between the top and back alignment marks; forming a light-shielding film over the entire back face of the transparent substrate; subjecting the film to a lift-off process to form a back face alignment mark; re-forming a resist film, on the whole back face of the transparent substrate; drawing a pattern, by correcting the measured misalignment amount; remeasuring the amount of misalignment between the top and back alignment marks; forming a light-shielding film on the whole back face of the transparent substrate; and subjecting the film to a lift-off process to form a back face pattern that comprises the light-shielding film. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method of manufacturing a photomask having different patterns on two opposing main surfaces of a transparent substrate, and in particular, after forming a pattern on one surface of a transparent substrate, the pattern is transparent without damaging the pattern. The present invention relates to a method for manufacturing a photomask for manufacturing different patterns on the other surface of a 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 a light-shielding film pattern made of a metal such as chromium on one main surface of a transparent substrate such as quartz glass. Has a formed structure. In recent years, in order to improve the optical characteristics of the projection exposure apparatus with higher accuracy and realize finer processing, the light-shielding film pattern is formed on both surfaces of two opposing main surfaces (each referred to as a front surface and a back surface) of the transparent substrate. A photomask to be formed (hereinafter also referred to as a double-sided mask) has been proposed (see, for example, Patent Document 1). By the way, in such a photomask in which a light shielding film pattern is formed on both surfaces of a transparent substrate, it becomes a technical problem to eliminate a deviation from a design value between a front surface pattern and a back surface pattern.

  In order to deal with such a problem, in Patent Document 2, after forming the surface pattern on the surface of the double-sided mask blank, the positional accuracy of the surface pattern is measured, and then the alignment pattern is drawn on the back surface. Measure the centrality and rotation, find the difference between the centrality and rotation of the front surface pattern and the back surface alignment pattern, change the correction with the position coordinates of the alignment pattern, and then draw the back surface pattern based on the position coordinates of the alignment pattern Then, after development and etching, a method for producing a double-sided mask after confirming that there is no problem in the deviation of the front and back patterns has been proposed.

  However, the method described in Patent Document 2 has a problem in that when the light shielding layer is etched by dry etching, the surface pattern already formed is damaged due to abnormal discharge during etching or wraparound of plasma. . On the other hand, when the light shielding layer is etched by wet etching, the pattern already formed on one surface of the transparent substrate is damaged, and the pattern is damaged.

Therefore, in Patent Document 3, in the method for producing a double-sided mask, a protective layer such as a film sheet having an adhesive layer is provided on one surface on which a transparent substrate pattern is formed, and then a pattern is formed on the other surface of the transparent substrate. A method for manufacturing a double-sided mask to be formed is disclosed.
JP 2006-80444 A JP 2004-145174 A JP 2006-285122 A

However, the method of forming a pattern on the other surface of the transparent substrate after providing the protective layer described in Patent Document 3 is complicated, and is being etched between the film sheet serving as the protective layer and the patterned transparent substrate. In other words, it is difficult to maintain uniform adhesiveness, and etching gas or etching liquid may permeate from a part of the end face of the protective layer film to damage the fine pattern on the surface.
In addition, in both methods of manufacturing the double-sided mask described in Patent Document 2 and Patent Document 3 described above, the final positional deviation of the front and back surfaces can be measured only after the back surface chrome pattern is formed. If the measured value is out of spec from the target amount of misalignment, it cannot be redone, but must be recreated from the chromium film on the surface, resulting in an increase in mask manufacturing time and manufacturing cost. It was.

  Therefore, the present invention has been made in view of the above problems. That is, the object of the present invention is to prevent the damage of the fine pattern on the surface by the etching gas or the etching solution which occurs when the back surface pattern is formed by etching after the surface pattern is prepared in advance in the method of manufacturing the double-sided mask, In the case of dry etching, there is no risk of damage to the surface due to abnormal discharge due to plasma wrapping around the surface or foreign matter, etc. It is an object of the present invention to provide a method for manufacturing a double-sided mask that can easily re-align the pattern on the back surface.

In order to solve the above-mentioned problems, a photomask manufacturing method according to the first aspect of the present invention is a photomask manufacturing method having different patterns on the front and back surfaces of a transparent substrate. Forming a first light-shielding film and a first resist film in order on one main surface of the transparent substrate, pattern-drawing and developing the first resist film, etching the exposed first light-shielding film; Stripping the first resist film to form a surface pattern including a surface main pattern and a surface alignment mark made of the first light-shielding film; and (2) a second surface on the other main surface of the transparent substrate. Forming a second resist film, pattern-drawing and developing the second resist film, and forming a back surface alignment mark and a back surface drawing mark made of the second resist film; A step of measuring a deviation amount of the front and back alignment marks based on an alignment mark and a back surface alignment mark made of the second resist film, and (4) forming a second light shielding film on the entire back surface of the transparent substrate. Next, the second resist film is lifted off and peeled off to form a back surface alignment mark and a back surface drawing mark made of the second light-shielding film, and (5) a first surface on the entire back surface of the transparent substrate. 3 is formed, a pattern is drawn based on the back surface drawing mark by correcting the measured deviation, and a back side main pattern and a back surface alignment mark made of the third resist film are formed. And (6) the front and back alignment masks again based on the front surface alignment mark and the back surface alignment mark made of the third resist film. And (7) forming a third light-shielding film on the entire back surface of the transparent substrate, then lifting off and peeling off the third resist film, possess a step of forming a back-side pattern including a back surface the pattern made of the light shielding film, and after forming a pattern on one surface of the transparent substrate, the other surface of the transparent substrate without damage to the pattern It is characterized in that different patterns are produced .

  A photomask manufacturing method according to a second aspect of the present invention is the photomask manufacturing method according to the first aspect, wherein the step (3) or the step (6) measures the amount of misalignment between the front and back alignment marks. When the deviation amount exceeds a predetermined value, a redo process of peeling the patterned resist film, forming a resist film on the transparent substrate again, drawing a pattern, and developing to form a resist pattern is performed. It is characterized by having.

  A photomask manufacturing method according to a third aspect of the present invention is the photomask manufacturing method according to the first or second aspect, wherein a back surface alignment mark made of the third resist film is the second resist film. The back surface alignment mark is a negative / positive inverted pattern.

  According to the photomask manufacturing method of the present invention, it is possible to reduce the risk of occurrence of damage to a previously formed front surface pattern during back surface pattern manufacturing. Furthermore, since the misalignment can be measured in the resist state, if the misalignment amount is larger than a predetermined value, the back surface pattern can be easily redone, and the mask manufacturing cost and the manufacturing period can be shortened. In addition, since pattern formation of the backside light-shielding film is performed by the lift-off method, for example, when a chromium light-shielding film is used, there is a problem of exhaust treatment using chlorine gas in the conventional dry etching method, or a problem of treatment of acidic waste liquid in the wet etching method Can be avoided.

  Hereinafter, the best embodiment of the method for producing a double-sided mask of the present invention will be described in detail with reference to the drawings. 1 to 3 are process cross-sectional schematic views showing an example of a method for producing a double-sided mask of the present invention.

  As shown in FIG. 1, a first light-shielding film 11 and a first resist film 12 are formed in this order on one main surface (front surface) of a cleaned transparent substrate 10 (FIG. 1 (a), FIG. 1). (B)) A pattern having a main surface pattern and a surface alignment mark is formed on the first resist film 12 with an electron beam (hereinafter also referred to as EB) or laser light 13 (FIG. 1 (1)). c)). 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 the drawing, the resist film 12 is developed, the exposed first light shielding film 11 is etched, the first resist film 12 is peeled off, and the main surface pattern 14 and the surface alignment mark 15 made of the first light shielding film are removed. A surface pattern 16 is formed (FIG. 1D).

  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 used when a double-sided mask is used as a photomask, and is distinguished from a pattern such as an alignment mark. It is preferable to provide two or more alignment marks on one main surface, both front and back.

  Next, a second resist film 17 is formed on the other main surface (back surface) opposite to the surface pattern 16 of the transparent substrate (FIG. 1E), and an electron beam, a laser beam, A second pattern drawing for forming a back surface alignment mark is performed on the second resist film 17 with the ultraviolet rays 18 (FIG. 1F).

  After drawing, development is performed to form a back surface alignment mark 20 for measuring the amount of misalignment made of the second resist film (FIG. 2A). The back surface alignment mark 20 is drawn and developed so that the portion where the light shielding film is to be formed is removed and the transparent substrate 10 is exposed. Here, as the EB drawing alignment mark used in the electron beam drawing process of the back side main pattern in the subsequent steps, the above back side alignment mark can also be used. Usually, the drawing apparatus has a dedicated alignment for each apparatus. Since a mark shape is required, a dedicated EB drawing alignment mark (not shown: illustration is omitted because the drawing is complicated) is drawn and formed separately in order to improve drawing accuracy. preferable. For the drawing of the back surface alignment mark, 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 20, when a substrate having a resist film formed on the back surface for drawing is set in a drawing apparatus, it is not necessary to position it precisely and can be set with a register, and the vertical 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 20 and the front surface alignment mark 15 substantially overlap. 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, when the back surface alignment mark 20 made of the front surface alignment mark 15 and the second resist film is observed from the vertical direction with an optical microscope or the like, the amount of positional deviation is measured, and the back surface main pattern is drawn. The parallel movement correction amount in the x and y directions and the rotational movement correction amount in the θ direction are obtained (FIG. 2B).

  If the amount of deviation of the front and back alignment marks is within a predetermined value, the process proceeds to the next step, and the second light shielding film 22 is formed on the entire back surface of the transparent substrate 10 to a predetermined thickness by sputtering or the like ( FIG. 2 (c)).

  Next, the second resist film on which the back surface alignment mark 20 is formed is lifted off and peeled off to form a back surface alignment mark 23 made of a second light shielding film (FIG. 2D). In the lift-off, a dedicated stripping solution for the second resist film or a solution that strips the resist film relatively easily and does not affect the surface pattern 16 and the second light shielding film 22 is used.

  If the amount of misalignment between the front and back alignment marks exceeds a predetermined value, as shown by NG in FIG. 2B, the back surface alignment mark 20 is formed and the patterned resist film is peeled off, and the above FIG. Returning to the step e), a resist film is formed again on the back surface of the transparent substrate 10, a pattern is drawn, and development is performed again after the step of forming a resist pattern.

  Next, a third resist film 24 is formed on the entire back surface including the back surface alignment mark 23 made of the second light shielding film of the transparent substrate 10 (FIG. 2E).

  Next, the measured deviation amount is corrected, and the back side main pattern and the back side alignment mark are drawn on the third resist film 24 by the electron beam 30 based on the EB drawing alignment mark (not shown) ( 3A), development is performed to form a back main pattern 31 and a back surface alignment mark 32 made of a third resist film (FIG. 3B). The back side main pattern 31 and the back side alignment mark 32 are drawn and developed so that a portion where the light shielding film is to be formed is removed and the transparent substrate 10 is exposed.

  Since the back surface alignment mark 23 made of the second light-shielding film has already been formed on the transparent substrate 10, the back surface alignment mark 32 made of the third resist film becomes the back surface alignment mark made of the second resist film. It is more preferable that the pattern of the mark 20 is a negative / positive inversion because the alignment mark can be easily identified. The negative / positive reversal pattern can be formed by a method of reversing the negative / positive of the back surface alignment mark region of the pattern drawing data, or a method of using a resist for forming a resist film separately for a positive type and a negative type.

  Next, the deviation amount of the front and back alignment marks is measured again based on the front surface alignment mark 15 and the back surface alignment mark 32 made of the third resist film (FIG. 3C). The deviation amount measurement at this stage is the final deviation amount measurement in the process of the present embodiment. After this, since the light shielding film for the back side main pattern is formed, if there is a misalignment, the light shielding film on the back side must be removed and the process must be started again. Because it occurs.

  If the amount of deviation between the front and back alignment marks is within a predetermined value, a third light-shielding film 34 is formed on the entire back surface of the transparent substrate 10 to a predetermined thickness by sputtering or the like (FIG. 3D). ).

  Next, the third resist film on which the back main pattern 31 and the back surface alignment mark 32 are formed is lifted off and peeled off to obtain a double-sided mask 36 on which the back pattern 35 including the back main pattern made of the third light shielding film is formed. (FIG. 3E). For the lift-off, a dedicated stripping solution for the third resist film or a solution that strips the resist film relatively easily and does not affect the already formed light shielding film pattern is used.

  If the amount of misalignment between the front and back alignment marks exceeds a predetermined value, as shown by NG in FIG. 3C, the patterned resist film on which the back surface alignment marks 32 are formed is peeled off, and the above-described FIG. Returning to the step e), a resist film is formed again on the back surface of the transparent substrate 10, a pattern is drawn, and development is performed again after the step of forming a resist pattern.

  In the above description, the first resist film 12, the second resist film 17, and the third resist film 24 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.

  Further, the first light-shielding film 11, the second light-shielding film 22, and the third light-shielding film 34 may all be the same type of light-shielding film, or two or three different types of light-shielding films may be used. However, in order to simplify the manufacturing process, it is preferable to use the same type of light shielding film.

  As described above, the photomask manufacturing method of the present invention is a method in which separate patterns are formed on the front and back surfaces of a photomask. After a pattern is formed on the surface of a transparent substrate, a resist applied on the back surface of the transparent substrate. In this method, a back surface pattern is drawn and developed, a light shielding film is formed thereon, and lift-off is performed. In the alignment of the front and back patterns, a process is used that makes it easy to redo when a misalignment occurs by using a back surface alignment mark made of a resist before forming a light shielding film on the back surface.

The photomask manufacturing method of the present invention can be applied even if the first light shielding film has a phase shift film, and the first light shielding film has a light transmittance at the exposure wavelength. The present invention can also be applied to a halftone semi-transparent light shielding film 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 washed, and chromium was deposited on one main surface (surface) as a light-shielding film to a thickness of 60 nm under the following conditions. Formed.
<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, an electron beam resist was applied on the light-shielding film to a thickness of 300 nm, prebaked, and then subjected to pattern exposure with an electron beam drawing apparatus and developed to form a resist pattern having a desired shape.

Next, using the resist pattern as a mask, the light-shielding film chrome exposed from the resist pattern was dry-etched under the following conditions by a dry etching apparatus and patterned.
<Chrome light shielding film 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 with oxygen plasma to form a surface pattern including a main surface pattern made of a chromium light-shielding film and two surface alignment marks.

  Next, on the other main surface (back surface) of the transparent synthetic quartz substrate, the same electron beam resist as described above is applied to a thickness of 300 nm, and after prebaking, pattern exposure is performed with an electron beam drawing apparatus, and development is performed. Resist patterns of two back surface alignment marks and two back surface drawing marks were formed.

  Next, based on the front surface alignment mark made of a chrome light-shielding film and the back surface alignment mark made of a resist, the amount of positional deviation between the front and back alignment marks was measured. The amount of deviation is within a predetermined value, and movement correction amounts in the x direction, y direction, and θ direction were obtained.

  Next, chromium is deposited as a light-shielding film on the entire back surface of the synthetic quartz substrate on which the resist pattern is formed to a thickness of 60 nm under the same conditions as the chromium film formation on the front surface side. The resist pattern was lifted off and peeled off to form a back surface alignment mark and a back surface drawing mark made of chromium.

  Next, the same electron beam resist as described above is applied to the entire back surface of the transparent synthetic quartz substrate to a thickness of 300 nm. After pre-baking, pattern exposure is performed with an electron beam drawing apparatus based on the movement correction amount, and development is performed. Then, a back surface main pattern and a back surface alignment mark resist pattern were formed.

  Next, when the amount of deviation of the front and back alignment marks was measured again based on the front surface alignment mark made of chromium and the back surface alignment mark made of resist, the amount of deviation was within a predetermined value.

  Next, chromium is again formed on the entire back surface of the transparent synthetic quartz substrate as a light-shielding film, and then the resist pattern is lifted off with a stripping solution dedicated to the resist, and then the back surface including the back main pattern made of chromium. A double-sided mask having different patterns on the front and back surfaces of a transparent synthetic quartz substrate was formed.

It is process cross-sectional schematic diagram which shows an example of the preparation methods of the double-sided mask of this invention. It is process cross-sectional schematic diagram which shows an example of the manufacturing method of the double-sided mask of this invention following FIG. FIG. 3 is a process cross-sectional schematic diagram illustrating an example of a method for producing a double-sided mask of the present invention following FIG. 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Transparent substrate 11 1st light shielding film 12 1st resist film 13 Electron beam or laser beam 14 Main surface pattern 15 Surface alignment mark 16 Surface pattern 17 Second resist film 18 Electron beam, laser beam, or ultraviolet ray 20 Back surface alignment mark 21 Displacement measurement location 22 Second light shielding film 23 Back surface alignment mark 24 Third resist film 30 Electron beam 31 Back surface main pattern 32 Back surface alignment mark 33 Deviation amount measurement location 34 Third light shielding film 35 Back surface pattern 36 Double-sided mask

Claims (3)

A method for producing a photomask having different patterns on both front and back surfaces of a transparent substrate,
(1) A first light shielding film and a first resist film are sequentially formed on one main surface of the transparent substrate, and the first resist film is patterned, developed, and exposed. Etching the first resist film to form a surface pattern including a surface main pattern and a surface alignment mark made of the first light shielding film; and
(2) A second resist film is formed on the other main surface of the transparent substrate, the second resist film is patterned and developed, and a back surface alignment mark and back surface drawing made of the second resist film are formed. Forming a mark for use;
(3) measuring a deviation amount of the front and back alignment marks based on the front surface alignment mark and the back surface alignment mark made of the second resist film;
(4) A second light-shielding film is formed on the entire back surface of the transparent substrate, and then the second resist film is lifted off and peeled off to form a back-surface alignment mark and back-surface drawing made of the second light-shielding film. Forming a mark for use;
(5) forming a third resist film on the entire back surface of the transparent substrate, correcting the measured shift amount, drawing a pattern based on the back surface drawing mark, developing the third resist film; Forming a back side main pattern and a back side alignment mark,
(6) A step of measuring a deviation amount of the front and back alignment marks again based on the front surface alignment mark and the back surface alignment mark made of the third resist film;
(7) A third light-shielding film is formed on the entire back surface of the transparent substrate, and then the third resist film is lifted off and peeled off, and the back surface including the back-side main pattern made of the third light-shielding film. forming a pattern, was perforated,
After forming a pattern in one surface of the said transparent substrate, a different pattern is produced in the other surface of the said transparent substrate, without damaging this pattern, The manufacturing method of the photomask characterized by the above-mentioned .
  2. The photomask manufacturing method according to claim 1, wherein in the step of measuring a displacement amount of the alignment marks on the front and back surfaces in the step (3) or the step (6), if the displacement amount exceeds a predetermined value, a pattern A method for producing a photomask, comprising: a step of peeling off the resist film, forming a resist film on the transparent substrate again, drawing a pattern, and developing to form a resist pattern.   3. The photomask fabrication according to claim 1, wherein the back surface alignment mark made of the third resist film is a negative-positive-inverted pattern of the back surface alignment mark made of the second resist film. 4. Method.