JP5168190B2 - Method for producing photomask having pattern on both sides and photomask - Google Patents

Description

  The present invention relates to a method for producing a photomask having a pattern on one main surface of a transparent substrate and both surfaces on the other main surface, and the photomask produced, and more particularly, a light shielding film on one main surface of a transparent substrate. The present invention relates to a method and a photomask for producing a double-sided photomask in which a light shielding pattern is formed and a diffractive optical element pattern is formed on the other main surface.

  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 photomask formed on both surfaces of 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).

  In order to improve illumination efficiency, a photomask in which a light shielding pattern made of a light shielding film is formed on one main surface of a transparent substrate and a diffractive optical element pattern is formed on the other main surface has been proposed (for example, a patent). Reference 2 and Patent Reference 3). The photomasks described in Patent Documents 1 to 3 having patterns on both the front and back surfaces of the transparent substrate are called “double-sided photomasks”, and in the present invention also have patterns on both the front and back surfaces of the transparent substrate. A photomask is used as a “double-sided photomask”.

The photomask described in Patent Document 2 has a light-shielding film pattern and a diffraction means using a diffraction grating or a hologram, so that the photomask itself has an oblique illumination function. Since projection exposure based on illumination is possible, it is possible to improve the resolution while maintaining high illumination efficiency.
However, since the photomask described in Patent Document 2 forms a diffractive optical element pattern using optical interference, a substrate provided with a photosensitive layer on the surface of the transparent substrate is required, and the photomask is manufactured on a separate transparent substrate. Since the light-shielding pattern and the diffractive optical element pattern are bonded to form a single photomask, it is difficult to bond with high accuracy, and there is a problem in the alignment accuracy of the front and back patterns. In addition, when the photomask becomes dirty after bonding, there is a problem that mask cleaning becomes difficult.

  On the other hand, the photomask described in Patent Document 3 has a light shielding pattern on one main surface of one transparent substrate, and a diffractive optical element (DOE element: Diffraction Optical Effect element) pattern on the other main surface. The light shielding pattern and the diffractive optical element pattern are integrated through a transparent substrate.

JP 2006-285122 A JP-A-9-50117 Japanese Patent Laid-Open No. 2004-14865

  However, conventionally, in order to produce a diffractive optical element pattern on a photomask, it has been necessary to produce it while confirming the optical characteristics of the diffractive optical element. It was not easy to form. In particular, as in the photomask described in Patent Document 3, when a light shielding film is formed on the transparent substrate on the opposite side of the diffractive optical element pattern, the light shielding pattern arrangement, the size of the measurement point, and other patterns The optical characteristics of the diffractive optical element may not be able to be measured due to the above-mentioned relationship, etc., and the etching state of the transparent substrate cannot be accurately grasped, and the production conditions have to be controlled by estimation. . Therefore, there is a problem that the quality and yield of the double-sided photomask produced are lowered.

  Therefore, the present invention has been made in view of the above problems. That is, an object of the present invention is a method for producing a double-sided photomask in which a light shielding pattern made of a light shielding film is formed on at least one main surface of a transparent substrate and a diffractive optical element pattern is formed on the other main surface. The position accuracy of each pattern on both the front and back sides including the diffractive optical element is high, the etching state of the transparent substrate is accurately grasped, and the etching depth and pattern dimensions of the diffractive optical element pattern are formed with high accuracy to achieve the desired optical It is to provide a method for manufacturing a double-sided photomask capable of obtaining characteristics and a double-sided photomask.

  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 provided with a light shielding film on both main surfaces of one main surface and the other main surface of a transparent substrate, The light shielding film on the one main surface is partially removed to form a light shielding pattern, the light shielding film on the other main surface is partially removed to form an opening, and a diffractive optical element is formed in the opening. A method for producing a double-sided photomask for forming an element pattern, wherein the diffractive optical element pattern is formed by etching the whole or part of a transparent substrate exposed in an opening of a light shielding film on the other main surface. A monitor pattern when the monitor opening is provided in the light shielding film on the other main surface outside the effective surface at the time of pattern exposure of the double-sided photomask, and the diffractive optical element pattern is formed in the monitor opening Forming the monitor It is characterized in forming said diffractive optical element pattern with reference to the etching conditions of the pattern. According to the first aspect of the present invention, there is provided a method for producing a double-sided photomask, comprising: forming a diffractive optical element pattern by forming a monitor pattern and etching the transparent substrate while referring to an etching state of the monitor pattern. It is possible to form a double-sided photomask having a high-precision pattern with desired optical characteristics by forming the etching depth and the pattern dimension with high accuracy.

  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 diffractive optical element pattern is a computer generated hologram element pattern. . The method for producing a double-sided photomask according to the invention of claim 2 makes it possible to easily provide a function of condensing, diffusing, branching, and dispersing incident light from an exposure light source by using a computer generated hologram element pattern. It is possible to illuminate an arbitrary point or region of the surface pattern while controlling the intensity distribution.

  The method for producing a double-sided photomask according to claim 3 is the method for producing a double-sided photomask according to claim 1 or 2, wherein the monitor pattern is the same pattern as the diffractive optical element pattern or the diffractive optical element. An optically equivalent pattern obtained by extracting feature points of an element pattern and simplified, wherein the diffractive optical element pattern is formed with reference to at least the etching depth and pattern dimensions of the monitor pattern It is. The method for manufacturing a double-sided photomask according to the invention of claim 3 has the advantage that when the monitor pattern is the same pattern as the CGH element pattern, it can be used as it is because it is the same pattern. When the monitor pattern is an optically equivalent pattern to the CGH element pattern, the drawing time for producing the monitor pattern can be shortened, and the production time and cost for the double-sided photomask can be reduced.

  The method for producing a double-sided photomask according to the invention of claim 4 is the method for producing a double-sided photomask according to any one of claims 1 to 3, wherein the optically equivalent pattern is a line / space. It is characterized by being formed of one or more of patterns, dot patterns, hole patterns or chirp patterns. The method for producing a double-sided photomask according to the invention of claim 4 is a pattern in which an optically equivalent pattern is simplified, so that the pattern can be easily produced, and the pattern can be measured and evaluated quickly and accurately. Can do.

  The method for producing a double-sided photomask according to the invention of claim 5 is the method for producing a double-sided photomask according to any one of claims 1 to 4, wherein the transparent substrate on the opposite side of the monitor pattern is formed. An opening for inspection of the monitor pattern is opened in the light shielding film formed on one main surface, and the diffractive optical element pattern is formed using the inspection opening while referring to the etching state of the monitor pattern. It is characterized by forming. In the method for producing a double-sided photomask according to the invention of claim 5, by providing an opening, diffracted light such as 0th order light of the monitor pattern and noise around the illumination pattern are evaluated, and etching of the quartz substrate of the CGH element pattern is performed. It is possible to easily select the optimum depth value. Furthermore, the emitted light from the opening can be measured and evaluated by another apparatus such as a two-dimensional intensity distribution evaluation apparatus or a spectroscopic apparatus using a camera.

  The method for producing a double-sided photomask according to the invention of claim 6 is the method for producing a double-sided photomask according to any one of claims 1 to 5, wherein the reference to the etching state of the monitor pattern is the monitor. It includes one or more evaluations among 0th-order light evaluation, intensity distribution evaluation, and diffraction efficiency evaluation of the pattern. The method for producing a double-sided photomask according to the invention of claim 6 confirms the optimum depth of the quartz substrate etching by referring to and evaluating the monitor pattern during the etching of the transparent substrate in the production process of the double-sided photomask. However, a double-sided photomask having a highly accurate pattern can be manufactured.

  In the double-sided photomask according to the seventh aspect of the present invention, a light shielding film is provided on both main surfaces of the transparent substrate on one main surface and the other main surface, and the light shielding film on the one main surface is partially provided. A light-shielding pattern is formed by removing the light-shielding film on the other main surface, and an opening is formed by partially removing the light-shielding film on the other main surface. The entire or part of the transparent substrate exposed to the opening is etched and diffracted. A double-sided photomask in which an optical element pattern is formed, wherein a monitor opening is provided in a light-shielding film on the other main surface outside the effective surface during pattern exposure of the double-sided photomask, and the monitor opening A monitor pattern for producing the diffractive optical element pattern on the part is formed by etching the transparent substrate. The double-sided photomask according to the invention of claim 7 has high positional accuracy of each pattern on both the front and back surfaces, and the diffractive optical element pattern has a high-precision etching depth and pattern dimensions and has desired optical characteristics, so that it has high quality. Pattern exposure transfer is possible.

  A double-sided photomask according to an eighth aspect of the present invention is the double-sided photomask according to the seventh aspect, wherein the diffractive optical element pattern is a computer generated hologram element pattern. The double-sided photomask according to the invention of claim 8 can easily have a function of condensing, diffusing, branching, and splitting incident light from the exposure light source by the computer generated hologram element pattern, and can have an arbitrary surface pattern. It is possible to illuminate points and regions while controlling the intensity distribution.

  A double-sided photomask according to the invention of claim 9 is the double-sided photomask according to claim 7 or claim 8, wherein the monitor pattern has the same pattern as the diffractive optical element pattern or a feature point of the diffractive optical element pattern. An optically equivalent pattern extracted and simplified, and the optically equivalent pattern is formed of one or more of a line / space pattern, a dot pattern, a hole pattern, and a chirp pattern. It is characterized by that. The double-sided photomask according to the invention of claim 9 has an advantage that when the monitor pattern is the same pattern as the CGH element pattern, it can be used as it is because it is the same pattern. In addition, when the monitor pattern is a pattern optically equivalent to the CGH element pattern, the pattern is simplified, so that the optical characteristics can be measured and evaluated accurately and quickly.

  The double-sided photomask according to the invention of claim 10 is the double-sided photomask according to any one of claims 7 to 9, wherein the double-sided photomask is on one main surface of the transparent substrate on the opposite side of the monitor pattern. The formed light-shielding film has an opening for inspection of the monitor pattern. The double-sided photomask according to the invention of claim 10 can easily evaluate diffracted light such as the 0th order light of the monitor pattern and noise around the illumination pattern by providing the inspection opening. Become. Furthermore, the emitted light from the opening can be measured and evaluated by another apparatus such as a two-dimensional intensity distribution evaluation apparatus or a spectroscopic apparatus using a camera.

  The double-sided photomask according to the invention of claim 11 is the double-sided photomask according to any one of claims 7 to 10, wherein the monitor pattern is a quality inspection pattern after the double-sided photomask is manufactured. It is also characterized by serving. The double-sided photomask according to the invention of claim 11 uses a monitor pattern outside the effective surface at the time of pattern exposure, and has zero-order light, intensity distribution, diffraction efficiency, etc. of the diffractive optical element pattern of the double-sided photomask. It can be evaluated and the quality of the double-sided photomask can be guaranteed.

  According to the method for producing a double-sided photomask of the present invention, an electron beam drawing apparatus or a laser drawing apparatus is used to measure the positional deviation between the front and back surfaces, and to draw a pattern while correcting it. A double-sided photomask with high pattern positional accuracy can be manufactured. Also, the etching depth and pattern dimensions of the diffractive optical element pattern can be formed with high accuracy by forming a monitor pattern and etching the transparent substrate while referring to the etching state of the monitor pattern to form the diffractive optical element pattern. A double-sided photomask having a desired optical characteristic and a highly accurate pattern can be obtained.

  According to the double-sided photomask of the present invention, the positional accuracy of each pattern on both the front and back surfaces is high, and the diffractive optical element pattern has a high-precision etching depth and pattern dimensions, and has desired optical characteristics. Exposure transfer is possible. In addition, it is possible to evaluate the zero-order light, intensity distribution, diffraction efficiency, etc. of the diffractive optical element pattern of the double-sided photomask using the monitor pattern outside the effective surface at the time of pattern exposure. It can be carried out.

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. It is a cross-sectional schematic diagram which shows an example of the double-sided photomask of this invention produced with the preparation method of the double-sided photomask of this invention. It is a perspective appearance schematic diagram which shows an example of the double-sided photomask of this invention produced by the preparation method of the double-sided photomask of this invention. It is an enlarged plane schematic diagram of the CGH element pattern formed in the opening part of the light shielding film. It is a perspective explanatory view showing a typical example of an illumination pattern formed on the light shielding pattern surface on the opposite side of the transparent substrate by light incident on the CGH element pattern. It is explanatory drawing which shows the typical example of the illumination pattern formed in the light-shielding pattern surface of the other side of a transparent substrate with the light which injected into the CGH element pattern, and the operation | work which extracts the feature point. It is a plane schematic diagram which shows the example of embodiment of the monitor pattern of this invention equivalent to a CGH element pattern. It is a schematic diagram which shows the example of the illumination pattern at the time of using the same pattern as a CGH element pattern as a monitor pattern. When a pattern similar to the CGH element pattern is used as the monitor pattern, it is an example of a light shielding film pattern formed on the opposite surface of the monitor pattern. It is a top view which shows the state of the noise of the illumination pattern outer peripheral part calculated | required by simulation using the light shielding film pattern for outer peripheral part noise evaluation. It is a schematic diagram which shows the example of the illumination pattern at the time of using the pattern equivalent to a CGH pattern as a monitor pattern. When a pattern equivalent to the CGH pattern is used as the monitor pattern, this is an example of a light shielding film pattern formed on the opposite surface of the monitor pattern.

  Hereinafter, a method for producing a double-sided photomask and an embodiment of a double-sided photomask of the present invention will be described in detail based on 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.

(Production method of double-sided photomask)
As shown in FIG. 1, a first light-shielding film 102 is formed on one main surface (front surface) of a cleaned transparent substrate 101 (FIG. 1A), and then a first resist film 103 is formed on this main surface (surface). Then, the first pattern is formed on the first resist film 103 with an electron beam (hereinafter also referred to as EB) or laser light 104 (FIG. 1B). As the transparent substrate 101, for example, a photomask substrate made of synthetic quartz having a thickness of 6.35 mm and a size of 154 mm × 154 mm square is used. The first light shielding film 102 is formed by depositing a light shielding material such as chromium by a sputtering method or the like. As a pattern to be drawn in the first drawing, at least three types of patterns including a main surface pattern, a surface alignment mark, and a pattern having a monitor pattern inspection opening are drawn. The monitor pattern inspection opening is formed outside the effective surface during pattern exposure so as not to hinder pattern transfer exposure.

  In the present invention, of two opposing main surfaces of the transparent substrate 101, one main surface is referred to as a front surface, and the other main surface is referred to as a back surface. The side and the back side mean the light source side, and usually a finer pattern is formed on the front side. In the present invention, this pattern is used when a double-sided photomask is used as a photomask, refers to a pattern transferred during pattern exposure, and is distinguished from patterns such as alignment marks. In order to increase the alignment accuracy of the front and back patterns, it is preferable to provide two or more alignment marks on one main surface on both the front and back surfaces.

  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 resist film 103 is developed to form a first resist pattern 105 (FIG. 1C), and then the exposed first light shielding film 102 is etched, and then the first resist pattern 105 is peeled off. Then, the surface pattern 106 made of the first light shielding film having at least the main surface pattern P1, the surface alignment mark A1, and the monitor pattern inspection opening (indicated as the inspection opening) M1 is formed (FIG. 1). (D)).

  Next, a second light shielding film 107 is formed on the other main surface (back surface) opposite to the surface pattern 106 of the transparent substrate (FIG. 1E), and then the second resist A film 108 is formed, and a second pattern drawing for forming a back surface alignment mark is performed on the second resist film 108 with an electron beam, laser beam, or ultraviolet ray 109 (FIG. 1F). The second light shielding film 107 is formed by depositing a light shielding material such as chromium by a sputtering method or the like.

  After drawing, development is performed to form a second resist pattern 110 (FIG. 1G), and then the exposed second light-shielding film 107 is etched, and then the second resist pattern 110 is peeled off, A light-shielding pattern 111 made of a second light-shielding film having a back surface alignment mark A2 for measuring a deviation amount is formed (FIG. 1 (h)). Here, as the EB drawing alignment mark used in the electron beam drawing process of the back surface pattern in the subsequent steps, the above back surface alignment mark can also be used. Usually, the drawing apparatus has a dedicated alignment mark for each apparatus. Since a shape is required, it is preferable to separately draw and form a dedicated EB drawing alignment mark (not shown: illustration is omitted because the drawing becomes complicated) in order to improve drawing accuracy. . For the drawing of the back surface alignment mark A2, 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.

  Next, the amount of positional deviation between the front and back surfaces is measured using the front surface alignment mark A1 and the back surface alignment mark A2. The amount of misalignment can be measured by observing from the vertical direction with an optical microscope or the like, and the amount of parallel movement correction in the x and y directions and the amount of rotational movement correction in the θ direction when drawing the pattern on the back surface are obtained. deep. If the deviation amount of the front and back alignment marks is within a predetermined value, the process proceeds to the next step. If it exceeds the predetermined value, the light shielding pattern 111 made of the second light shielding film is etched by a method such as etching. Then, the process returns to the process of FIG. 1E, and the processes after the second light shielding film formation are performed again.

  Next, a third resist film 112 is formed on the light shielding pattern 111 made of the second light shielding film on which the back surface alignment mark A2 is formed. The pattern is drawn (FIG. 2 (i)). As a pattern to be drawn, at least two types of patterns, that is, a pattern having a back surface pattern opening and a monitor opening are drawn. The monitor opening is formed outside the effective surface during pattern exposure so as not to hinder pattern transfer exposure.

  After drawing, the resist film 112 is developed to form a third resist pattern 114 (FIG. 2 (j)), and then the light-shielding pattern 111 made of the exposed second light-shielding film is etched, and then the second resist The pattern 112 is peeled off to form a back surface pattern 115 made of a second light shielding film having at least a back surface pattern opening P2, a monitor opening M2, and a back surface alignment mark A2 (FIG. 2 (k)).

  Next, a fourth resist film 116 is formed on the back surface pattern 115 made of the second light-shielding film (FIG. 2L), and the fourth resist film 116 is subjected to a fourth time with an electron beam or laser light 117. The pattern is drawn (FIG. 2 (m)). As the drawing pattern, at least two types of patterns are drawn: a diffractive optical element pattern as a back surface pattern to be drawn in the back surface pattern opening P2, and a monitor pattern to be drawn in the monitor opening M2.

  After the drawing, the fourth resist film 116 is developed to form a fourth resist pattern 118 having at least a diffractive optical element pattern and a monitor pattern, and the transparent substrate 101 is exposed in each pattern portion (FIG. 2 (n )). Next, the exposed transparent substrate 101 is etched to a predetermined depth to form a recess 119 in the monitor opening M2 and a recess 120 in the back pattern opening P2 (FIG. 2 (o)).

  For the etching of the transparent substrate 101, a conventionally known wet etching method using a hydrofluoric acid aqueous solution or a dry etching method using a fluorine-based gas can be applied, but dry etching is more preferable from the viewpoint of forming a fine pattern.

  In the present invention, in the etching of the transparent substrate 101, the diffractive optical element pattern is formed while referring to the etching state of the monitor pattern. The etching state of the monitor pattern can be monitored using the inspection opening of the light shielding layer formed on the transparent substrate on the opposite side of the monitor pattern.

  The etching state of the monitor pattern is observed and measured, and if the etching state is within a predetermined numerical range, the etching process is terminated, the fourth resist pattern 118 is peeled off, and the back surface pattern is formed on the back surface. A double-sided photomask having at least the optical element pattern P3, the monitor pattern M3, and the alignment mark A2 is formed (FIG. 2 (p)).

  In the above description, the first resist film 103, the second resist film 108, the third resist film 112, and the fourth resist film 116 may all be formed of the same type of resist, or 2 A plurality of different types of resists may be used, but it is preferable to use the same type of resist in order to simplify the manufacturing process.

  In addition, as the first light shielding film 102 and the second light shielding film 107, the same kind of light shielding film may be used, or two kinds of light shielding films having different front and back surfaces may be used. In order to simplify the above, it is preferable to use the same type of light shielding film. The light-shielding film is not limited to a single-layer film, and may be a two-layer film having a surface low reflection layer or a three-layer film having a low reflection layer on the front and back surfaces. Examples of the above include a chromium film as a single layer film, a chromium oxide film / chromium film as a two layer film, and a chromium oxide film / chromium film / chromium nitride film as a three layer film.

  In the above-described double-sided photomask manufacturing method, the main manufacturing procedure of the embodiment is to form a front surface pattern having a front surface main pattern and an inspection opening, a back surface pattern forming having a back surface pattern opening and a monitor opening. Although the backside CGH element pattern and the monitor pattern formation are described in this order, the manufacturing method of the present invention is not limited to the manufacturing procedure of the above embodiment. For example, as another embodiment of the method for producing a double-sided photomask of the present invention, it is also possible to produce a surface pattern, a backside CGH element pattern and a monitor pattern, and a backside pattern. Further, as another embodiment, it is possible to fabricate the back surface CGH element pattern and the monitor pattern, the back surface pattern, and the front surface pattern in this order. Furthermore, as another embodiment, it is also possible to manufacture in the order of back surface pattern formation, back surface CGH element pattern and monitor pattern formation, and surface pattern formation.

  The method for manufacturing a double-sided photomask 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 transmits light at the exposure wavelength. The present invention can also be applied to a halftone semi-transparent light shielding film having a rate of 5 to 40%.

(Double-sided photomask)
FIG. 3 is a schematic cross-sectional view showing an example of the double-sided photomask of the present invention produced by the method for producing a double-sided photomask of the present invention. In FIG. 3, when the same part as FIG. 2 is shown, the same code | symbol is used. In FIG. 3, a surface pattern 106 made of a first light-shielding film having at least a main surface pattern P1, a surface alignment mark A1, and a monitor pattern inspection opening M1 is formed on one main surface (front surface) of the transparent substrate 101. A second diffractive optical element pattern P3 formed by etching the transparent substrate 101, a rear surface alignment mark A2, and a monitor pattern M3 used when producing the diffractive optical element pattern P3 is formed on the other main surface (back surface). The monitor pattern M3 is formed by etching the transparent substrate exposed at the opening of the second light-shielding film outside the effective surface during pattern exposure of the double-sided photomask. It is what.

  In the manufacturing process of the double-sided photomask substrate manufacturing method according to the present embodiment, the surface alignment mark A1 provided on the front surface pattern 106 made of the first light shielding film and the back surface pattern 115 made of the second light shielding film are provided. The back surface alignment mark A2 includes a main surface pattern P1 and a monitor pattern inspection opening M1 formed on the surface of the transparent substrate 101, and a back surface pattern opening P2, a diffractive optical element pattern P3, and a monitor pattern formed on the back surface. This is used when aligning the front and back with M3. As a technique used when aligning the front and back with such an alignment mark, the methods described in Japanese Patent Application Nos. 2008-262439 and 2008-262440 already filed by the present applicant can be used. The front surface alignment mark A1 and the rear surface alignment mark A2 shown in FIG. 3 are not used for transfer exposure using the completed double-sided photomask, but are provided outside the exposure region. In FIG. 3, alignment marks used between the mask and the transfer target during exposure are omitted.

  FIG. 4 is a schematic perspective external view showing an example of the double-sided photomask of the present invention manufactured by the double-sided photomask manufacturing method of the present invention, with the back side on which the diffractive optical element pattern is provided on the upper side. In FIG. 4, a surface pattern 106 (pattern is not shown) made of a light shielding film is formed on one main surface (front surface) of the transparent substrate 101, and the transparent substrate is etched on the other main surface (back surface). A computer generated hologram (CGH) element pattern (also referred to as a CGH element pattern) P3 as a diffractive optical element pattern and a monitor pattern M3 are formed in the opening of the light shielding film. In FIG. 4, only one monitor pattern is shown, but in the present invention, it is preferable to provide a plurality of locations outside the effective surface during pattern exposure. In FIG. 4, the alignment pattern is omitted because the figure becomes complicated.

  In the present invention, the entire or part of the transparent substrate exposed at the opening of the light shielding film on the other main surface (back surface) of the transparent substrate 101 is etched. A mask having a light shielding film pattern in which the transparent substrate is not etched on the back side is also included in the double-sided photomask of the present invention.

  In the present invention, a diffraction grating, a holographic optical element, or the like can be applied as the diffractive optical element, but a computer generated hologram (CGH) element designed in advance so as to generate a light pattern having a desired light intensity distribution. The one consisting of is preferred. The computer generated hologram element is a hologram that is produced by calculating an interference fringe pattern obtained by interference between object light and reference light, and directly outputting the result by a drawing apparatus. An interference fringe shape for obtaining a desired light intensity distribution as reproduction light can be obtained by optimization using iterative calculation by a computer. The computer generated hologram element is a diffractive optical element that can be produced by etching a transparent synthetic quartz substrate in a stepped manner in multiple steps based on the above-described interference fringe shape.

  5 is an enlarged plan view of the CGH element pattern portion of the double-sided photomask according to the embodiment of the present invention in which the CGH element pattern P3 is formed in the opening of the light shielding film of the back surface pattern 115 made of the second light shielding film shown in FIG. It is a schematic diagram.

  When performing exposure using the double-sided photomask of the present invention, as described above, the back surface pattern 115 made of the second light shielding film is set to the exposure light source side, and the surface pattern 106 made of the first light shielding film is transferred. Used by setting on the exposure side. A circuit pattern or the like is formed on the front surface pattern 106, while a diffractive optical element pattern P3 is formed on the transparent substrate where the opening of the back surface pattern 115 made of the second light shielding film is exposed. Hereinafter, a CGH element pattern will be described as an example of the diffractive optical element pattern P3.

  The CGH element has a function of condensing, diffusing, branching, and splitting light incident from the exposure light source, and can illuminate any point or region of the surface pattern 106 while controlling the intensity distribution. Light can be applied to each part of the surface pattern 106 from the entire region of the CGH element pattern P3. For example, the CGH element pattern P3 can realize that a specific region of the surface pattern 106 is irradiated with light having high intensity and other regions are irradiated with weak light having low intensity. Conversely, when viewed from an arbitrary point or region on the surface pattern 106 surface, the angle, direction, and intensity distribution of incident light can be selectively controlled. For example, it is possible to consider the arrangement and functions of the CGH elements in consideration of the arrangement of the entire optical system of the exposure apparatus including the light source, the surface pattern surface 106 of the double-sided photomask, and the imaging plane. With such a function of the CGH element pattern P3 in the opening of the back surface pattern 115, it becomes possible to realize lithography that is finer than the conventional one using the double-sided photomask of the present invention.

(Monitor pattern)
As described above, when light enters the CGH element pattern, it is diffracted and a reproduction pattern having an arbitrary shape and intensity distribution is illuminated on the opposite surface. Based on this illumination pattern, a monitor pattern is designed, placed on a photomask, and with reference to the monitor pattern, the etching depth control of the pattern on the transparent substrate (synthetic quartz substrate), the critical dimension CD (Critical Dimension) Perform management.

  As a preferred embodiment of the method for producing a double-sided photomask of the present invention, the above monitor pattern is the same pattern as the diffractive optical element pattern or an optically equivalent pattern that is simplified by extracting feature points of the diffractive optical element pattern. The diffractive optical element pattern is formed with reference to at least the etching depth and pattern dimensions of the monitor pattern.

  For example, when the monitor pattern is the same pattern as the CGH element pattern, there is an advantage that it can be used as it is because it is the same pattern. However, if the monitor pattern is the same as the diffractive optical element pattern, the monitor pattern becomes complicated and the drawing time for creating it increases, resulting in an increase in the production time and cost of the double-sided photomask, making it suitable for practical use. There may be no cases.

  Therefore, in the present invention, as a preferred embodiment, an optically equivalent pattern obtained by extracting and simplifying feature points of a complicated pattern of a CGH element pattern is used as a monitor pattern. Next, an optically equivalent monitor pattern will be described.

  6 is formed on the light shielding pattern surface on the surface side of the double-sided photomask (thickness 6.35 mm) by the light 601 incident on the CGH element pattern on the backside (light source side) of the double-sided photomask shown in FIG. It is a perspective explanatory view showing a typical example of a lighting pattern. In FIG. 6, FIG. 6A shows a case where the reproduced illumination pattern is a rectangular pattern, FIG. 6B shows a case where the rectangular pattern is hollowed out in a rectangular shape, and FIG. This is the case of a circular pattern.

  FIG. 7 shows a representative example of an illumination pattern formed by reproducing light incident on the CGH element pattern shown in FIG. It is explanatory drawing which shows. FIG. 8 is a schematic plan view showing an example of an embodiment of the monitor pattern of the present invention equivalent to the CGH pattern.

  FIG. 7A shows a case where the reproduced illumination pattern is a rectangular pattern. When the maximum diffraction angle shown in FIG. 7A is θ, a monitor pattern equivalent to the illumination pattern is shown in FIG. It can be represented by a line / space pattern having a pitch d shown in a-1) or a dot pattern having a pitch d shown in FIG. The dot pattern (dot width is d / 2) may be either a positive type or a negative type.

  FIG. 7B shows a case of a rectangular pattern in which the reproduced illumination pattern is hollowed out. The diffraction angle of the far part of the illumination pattern shown in FIG. 7B is θ1, and the diffraction angle of the inner part is θ2. Or, if the reference point is at the corner of the hollow rectangular pattern, an equivalent monitor pattern is a line / space pattern having a plurality of pitches d1 and d2 shown in FIG. 8 (b-1), or FIG. It can be represented by a line / space pattern having an oblique component shown in b-2).

  FIG. 7C-1 shows a case where the reproduced illumination pattern is a circular pattern having a center of gravity. In this case, as a monitor pattern equivalent to the illumination pattern, a chirp pattern in which the pitch of the line / space pattern is not uniform but gradually changes as a function of the position is individually arranged in the above d1 to d2. Can be represented.

  FIG. 7C-2 shows a case where the reproduced illumination pattern has an intensity distribution. For example, FIG. 7C-3 shows a plurality of concentric intensity distributions and weights in order from the left side of the figure. An example of an intensity distribution of a certain rectangular intensity distribution, a rectangular intensity distribution having a weight in four directions, and a Gaussian distribution is shown. In this case, referring to the intensity distribution of the illumination pattern, the pitch of the diffraction grating is calculated from the feature points such as p1 and p2, the average position, and the half width (in the case of Gaussian distribution), and the monitor pattern equivalent to the diffractive optical element pattern Form. Alternatively, a monitor pattern equivalent to the diffractive optical element pattern is formed at the pitch of the diffraction grating obtained by using a statistical method, image processing, or numerical calculation method.

  As described above, the method for manufacturing a double-sided photomask according to the present invention has a simplified monitor pattern optically equivalent to the CGH element pattern, but the line / space pattern, dot pattern, hole pattern, or pitch changes. The chirp pattern is preferably formed of any one or more of the chirp patterns. By using a simplified monitor pattern that is optically equivalent to the CGH element pattern, the drawing time for producing the monitor pattern can be shortened, and the production time and cost for the double-sided photomask can be reduced.

(Evaluation by monitor pattern)
As a method of measuring the etching depth and pattern dimension of the CGH element pattern by evaluating the etching state of the transparent substrate with the monitor pattern, high-magnification pattern observation with a scanning electron microscope (SEM), length measurement, atomic spacing A method such as etching depth measurement using a force microscope (AFM) is used. In the case of the above measurement, observation and measurement can be performed from the upper surface side on the monitor pattern side. However, it is more preferable to evaluate the reproduced illumination pattern for optical evaluation, and in the case of optical evaluation, by devising the light shielding pattern on the surface on the opposite side of the transparent substrate, Optical evaluation is possible.

  Therefore, as a preferred embodiment of the present invention, an opening for inspecting the monitor pattern is formed in the light shielding film formed on one main surface (front surface) of the transparent substrate on the opposite side of the monitor pattern, and this inspection is performed. The diffractive optical element pattern is formed by using the opening for the reference while referring to the etching state of the monitor pattern.

  Furthermore, as a preferred embodiment of the present invention, the reference of the etching state of the monitor pattern includes one or more of evaluations of 0th-order light evaluation, intensity distribution evaluation, and diffraction efficiency evaluation of the monitor pattern. .

  Next, regarding the method for evaluating the optical characteristics of the CGH element pattern P3 using the monitor pattern M3 according to the present invention, a case where the same pattern as the CGH element pattern is used as the monitor pattern, and a pattern equivalent to the CGH element pattern are used. More detailed description will be given for each case.

  FIG. 9 is a schematic diagram showing an example of an illumination pattern when a pattern similar to the CGH element pattern is used as the monitor pattern. FIG. 9A shows the other main surface (back surface) of the transparent substrate where the incident light 901 is transmitted. FIG. 9B is a schematic perspective view showing a state where the light is diffracted by the CGH element pattern 902 and reproduced as the illumination pattern 904 on the light shielding film surface 903 on the one main surface (front surface) side of the transparent substrate. FIG. 6 is a plan view of an illumination pattern 904. As shown in FIG. 9B, zero-order light and noise 905 generated around the illumination pattern are observed in the illumination pattern 904 formed on the light shielding film surface 903 on the surface side of the transparent substrate.

  Therefore, by providing an opening that emits diffracted light on the light shielding film surface 903 on the surface side of the transparent substrate, diffracted light such as the 0th order light of the monitor pattern and noise around the illumination pattern are evaluated, and the 0th order light is It is possible to easily select the location where the noise is minimized, the location where the noise is minimized, or the location where the signal portion is maximized as the optimum value of the quartz substrate etching depth of the CGH element pattern. Furthermore, the light emitted from the inspection pattern opening can be measured and evaluated by a separate device such as a two-dimensional intensity distribution evaluation device or a spectroscopic device using a camera.

  As described above, the pattern formed on the one main surface (front surface) side of the transparent substrate, which is the opposite surface of the monitor pattern provided on the other main surface (back surface) of the transparent substrate, causes the diffracted light of the CGH element pattern. Zero-order light, intensity distribution, diffraction efficiency, etc. can be evaluated. FIG. 10 is an example of a light shielding film pattern formed on the opposite surface of the monitor pattern. 10A is a light-shielding film pattern for evaluating zero-order light, FIG. 10B is a light-shielding film pattern for evaluating an illumination pattern, and FIG. 10C is a partial evaluation for evaluating a CGH signal at an arbitrary place. FIG. 10D shows a light shielding film pattern for evaluating the outer peripheral noise. FIG. 11 is a plan view showing the state of noise in the outer peripheral portion of the illumination pattern obtained by simulation using the light shielding film pattern for outer peripheral noise evaluation shown in FIG.

  FIG. 12 is a schematic diagram illustrating an example of an illumination pattern when a pattern equivalent to the CGH element pattern is used as the monitor pattern. In FIG. 12A, incident light 121 is diffracted by the CGH element pattern 122 on the other main surface (back surface) of the transparent substrate, and an illumination pattern 124 is formed on the light shielding film surface 123 on the one main surface (front surface) side of the transparent substrate. FIG. 12B is a schematic perspective view showing a state formed by reproduction, and FIG. 12B shows an example of a monitor pattern (line / space pattern and dot pattern) and a plan view of the illumination pattern. ± 1st order light is generated. When the monitor pattern produced by the method described with reference to FIGS. 7 and 8 is used, diffracted light is generated as shown in FIG. 12. Therefore, the 0th-order light and the ± 1st-order light are simultaneously or separated. measure.

  FIG. 13 shows an example of a light shielding film pattern formed on the opposite surface of the monitor pattern, which is a light shielding film pattern for 0th order light evaluation and a light shielding film pattern for ± first order light evaluation.

  As described above, in order to reduce the zero-order light of the diffractive optical element or to evaluate the diffracted light intensity, the monitor pattern is created in consideration of the diffractive optical element pattern. By referring to the monitor pattern during the etching of the substrate, a double-sided photomask having a highly accurate pattern can be manufactured. For example, by using an appropriate monitor pattern, it is possible to manufacture while monitoring the zero-order light and confirming the optimum depth of the quartz substrate etching.

  In order to minimize the zero-order light of the CGH element, the accuracy is improved by managing each illumination pattern for each CGH element. Moreover, it is preferable that the arrangement relationship between the CGH element pattern and the monitor pattern is an arrangement in consideration of an etching manufacturing error of the synthetic quartz substrate. Therefore, in the method for producing a double-sided photomask of the present invention, it is preferable to provide monitor patterns at several locations outside the effective surface at the time of pattern exposure of the double-sided photomask.

  Since there is a fine light-shielding film pattern on the light-shielding film pattern side opposite to the CGH element pattern, it cannot always be said that it is always possible to directly measure the optical characteristics of the CGH element pattern itself. In the double-sided photomask of the present invention, the monitor pattern can be used as a quality inspection pattern after the double-sided photomask is manufactured. Using the monitor pattern and the opening for inspection of the monitor pattern, the 0th-order light, intensity distribution, diffraction efficiency, etc. of the diffracted light of the CGH element pattern can be evaluated, the quality of the double-sided photomask can be assured, A high-quality double-sided photomask can be provided.

DESCRIPTION OF SYMBOLS 101 Transparent substrate 102 1st light shielding film 103 1st resist film 104 Electron beam or laser beam 105 1st resist pattern 106 Surface pattern P1 Surface main pattern A1 Surface alignment mark M1 Inspection opening 107 2nd light shielding film 108 Second resist film 109 Electron beam or laser beam or ultraviolet ray 110 Second resist pattern A2 Back surface alignment mark 111 Light shielding pattern 112 Third resist film 113 Electron beam or laser beam 114 Third resist pattern P2 Back surface pattern opening M2 Monitor opening 115 Back pattern 116 Fourth resist film 117 Electron beam or laser beam 118 Fourth resist pattern 119, 120 Concavity P3 Diffractive optical element pattern (Back side main pattern)
M3 monitor pattern 901, 121 incident light 902, 122 CGH element pattern 903, 123 light shielding film surface 904, 124 illumination pattern 905 noise

Claims (11)

A light-shielding film is provided on both main surfaces of the one main surface and the other main surface of the transparent substrate, and a light-shielding pattern is formed by partially removing the light-shielding film on the one main surface, and the other main surface A method for producing a double-sided photomask in which the light shielding film on the top is partially removed to form an opening, and a diffractive optical element pattern is formed in the opening.
When forming the diffractive optical element pattern by etching the entire or part of the transparent substrate exposed in the opening of the light shielding film on the other main surface,
A monitor opening is provided in the light shielding film on the other main surface outside the effective surface at the time of pattern exposure of the double-sided photomask, and the monitor pattern for producing the diffractive optical element pattern in the monitor opening is provided. And forming the diffractive optical element pattern with reference to the etching state of the monitor pattern.   The method for producing a double-sided photomask according to claim 1, wherein the diffractive optical element pattern is a computer generated hologram element pattern.   The monitor pattern is the same pattern as the diffractive optical element pattern or an optically equivalent pattern obtained by extracting feature points of the diffractive optical element pattern, and at least the etching depth and pattern dimension of the monitor pattern are set. 3. The method for producing a double-sided photomask according to claim 1, wherein the diffractive optical element pattern is formed with reference to the double-sided photomask.   4. The double-sided photo according to claim 3, wherein the optically equivalent pattern is formed of one or more of a line / space pattern, a dot pattern, a hole pattern, and a chirp pattern. A method for manufacturing a mask.   An opening for inspection of the monitor pattern is opened in a light shielding film formed on one main surface of the transparent substrate on the opposite side of the monitor pattern, and the opening of the monitor pattern is formed using the inspection opening. The method for producing a double-sided photomask according to any one of claims 1 to 4, wherein the diffractive optical element pattern is formed while referring to an etching state.   6. The reference to the etching state of the monitor pattern includes one or more evaluations of zero-order light evaluation, intensity distribution evaluation, and diffraction efficiency evaluation of the monitor pattern. The method for producing a double-sided photomask according to any one of the above. A light shielding film is provided on both main surfaces of the one main surface and the other main surface of the transparent substrate, and a light shielding pattern is formed by partially removing the light shielding film on the one main surface, and the other main surface A double-sided photomask in which an opening is formed by partially removing the light shielding film on the top, and a diffractive optical element pattern is formed by etching the entire or part of the transparent substrate exposed in the opening,
A monitor pattern is provided when a light-shielding film on the other main surface outside the effective surface at the time of pattern exposure of the double-sided photomask is provided with a monitor opening, and the diffractive optical element pattern is produced in the monitor opening. A double-sided photomask formed by etching the transparent substrate.   The double-sided photomask according to claim 7, wherein the diffractive optical element pattern is a computer generated hologram element pattern.   The monitor pattern is the same pattern as the diffractive optical element pattern or an optically equivalent pattern obtained by extracting feature points of the diffractive optical element pattern, and the optically equivalent pattern is a line / space. 9. The double-sided photomask according to claim 7 or 8, wherein the double-sided photomask is formed of at least one of a pattern, a dot pattern, a hole pattern, and a chirp pattern.   8. An inspection opening for the monitor pattern is formed in a light shielding film formed on one main surface of the transparent substrate on the opposite side of the monitor pattern. 10. The double-sided photomask according to any one of 9 above.   The double-sided photomask according to any one of claims 7 to 10, wherein the monitor pattern also serves as a quality inspection pattern after the double-sided photomask is manufactured.

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