JP2007155927A - Diffraction optical element manufacturing method, diffraction optical element and reticle mask used in the manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diffraction optical element and a manufacturing method of the diffraction optical element, wherein the deterioration of a characteristic of the optical element due to a manufacturing error is prevented from occurring, and further mass-productivity is drastically improved, in a manufacturing method of the step-like diffraction optical element in which a series of treatment processes comprising: plotting exposure treatment of performing selective plotting exposure and patterning by using a plotting exposure device; development treatment; and etching treatment or else are repeated. <P>SOLUTION: The diffraction optical element manufacturing method comprises: a process of disposing a photosensitive material layer on one surface of a working substrate, exposing the photosensitive material layer by a projection exposure method of using a reticle mask which controls a transmission light quantity (exposure quantity) distribution upon exposure in accordance with a distribution state of a fine dot-pattern, developing the exposed photosensitive material layer, and forming a first rugged pattern whose raw material is the photosensitive material layer; and a process of removing the first rugged pattern by performing etching from the first rugged pattern formation side, and forming a second rugged pattern corresponding to the rugged shape of the first rugged pattern on one surface itself of the working substrate as the ruggedness of the diffractive optical element. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a method for manufacturing a diffractive optical element in which one surface of a processing substrate is processed to provide unevenness, and a diffractive optical element manufactured by the manufacturing method.
In addition, examples of the field of application of such a diffractive optical element include the field of semiconductor lithography, the field of nanotechnology, the field of optical members, and the like, but are not limited thereto.

Conventionally, as an optical element for controlling an optical path, a photorefractive medium such as a lens or a prism or a reflective optical element such as a mirror has been known. However, in recent years, with the spread of optical communication or the optical industry, Research and development of devices that control the optical path based on the difference in the wavelength of light has become active.
In addition, when detecting or extracting a slight difference in the wavelength of light, there is an increasing demand for a diffractive optical element that is finely processed and controls the light traveling direction and phase according to the element shape. It is coming.
As shown in FIG. 18A, the surface of the diffractive optical element needs to have a sawtooth state in which the cross section is expressed in a step shape by the discontinuous slope portion 11, but such a cross section is nonlinear. It is difficult to finely process the sawtooth shape from the viewpoint of processing accuracy, and it is usually produced by approximating the staircase shape shown in FIG.
In FIG. 18, 12 is a staircase part and 12a is a step part.
A diffractive optical element having a stepped surface as shown in FIG. 18B is hereinafter also referred to as a stepped diffractive optical element, and a portion processed into a stepped shape is also referred to as a step.
The width (also referred to as the minimum width) δ for one step of the stairs is the same everywhere.
In the case of the step-like diffractive optical element shown in FIG. 18B, the sawtooth shape is made to be a staircase shape by reducing the width of one step (also referred to as the minimum width) δ to about ½ of the wavelength of light. And similar optical characteristics can be obtained.

As a method for manufacturing such a staircase portion of the diffractive optical element, a first manufacturing method is known in which patterning is performed using a mask exposure method as described in US Pat. No. 5,218,471 (Patent Document 1). Yes.
US Pat. No. 5,218,471 Note that Patent Document 1 relates to a method of manufacturing a microlens. In the case of this manufacturing method, mask exposure exposes accuracy, and it is premised on mask manufacturing. However, if high resolution is required, an error may occur in mask manufacturing itself. Then, it is necessary to produce masks corresponding to the number of steps of the staircase to be produced. Further, in semiconductor manufacturing applications such as a homogenizer inside a stepper, the minimum drawing unit of the diffractive optical element tends to become smaller as the wavelength of light becomes shorter. The influence of optical characteristics on dimensions and alignment errors tends to increase, and the method of Patent Document 1 has a limit. Also, design data suitable for the shape and size of each stage is created for each stage, and the design data is created for each stage by a drawing exposure apparatus such as an EB drawing apparatus (electron beam drawing apparatus) or a laser drawing apparatus. A second method is known in which drawing exposure is performed based on the above, development is performed, and dry etching corresponding to the depth of each step is performed. For example, a manufacturing method has been proposed in which a series of processing processes including a drawing exposure process that selectively performs pattern exposure and patterning using an EB drawing apparatus, a development process, an etching process, and the like are repeatedly performed and the manufacturing process is performed. Yes. The inventor of the present application has proposed a method for manufacturing a diffractive optical element capable of loosening the alignment accuracy in the second method, as described in JP-A-2002-350623 (Patent Document 2). JP, 2002-350623, A On the other hand, Fujita, Nishihara, Koyama et al., As a third production method, produced a blazed grating using electron beam lithography in 1982, Optical City America (Non-patent Document 1). The process is disclosed. A desired cross-sectional shape is obtained by changing the dose amount of electrons to the PMMA layer stepwise, drawing exposure with an EB drawing apparatus, and developing. 1982, Optical Science America

In recent years, the second manufacturing method has come to be mainly adopted from the viewpoint of patterning accuracy.
The diffractive optical element is manufactured by the second method, as described above, the drawing exposure process in which patterning is performed by selectively drawing exposure using a drawing exposure apparatus such as an EB drawing apparatus or a laser drawing apparatus, and development. A series of processing processes including processing and etching are repeatedly performed. In the drawing exposure using the drawing exposure apparatus in each series of processing processes, drawing data created in advance based on the design is used. .
For example, as shown in FIG. 19 showing an example of the manufacturing process, a series of processing steps including a drawing exposure process, a development process, and an etching process are repeated, and the characteristics of the manufactured diffractive optical element are inspected later. To do.

The production of a conventional diffractive optical element will be briefly described with reference to FIG.
Hereinafter, such a conventional method for manufacturing a diffractive optical element is also referred to as a method for manufacturing a stepped diffractive optical element.
In order to simplify the description, a case where a four-step staircase diffractive optical element as shown in FIG.
Data for drawing exposure is prepared for each dry etching process. Then, a chromium film 120 is formed on one surface of a plate-shaped processing material 110 made of a photorefractive medium by a sputtering method, a vapor deposition method, or the like, and a photosensitive positive resist is formed on the chromium film 120. 130 is formed. (FIG. 19 (a))
As the processing material 110, a quartz glass substrate (including a synthetic quartz substrate) is usually used, but is not limited thereto.
Next, a predetermined area is exposed and developed using predetermined drawing exposure data, and a (resist) opening 131 is provided in the predetermined area. (FIG. 19 (b))
Next, using the resist 130 provided with the opening 131 as an etching resistant mask, the chromium film 120 exposed from the opening 131 is removed by etching, and a chromium film opening corresponding to the resist opening 131 is provided (not shown). Then, dry etching is performed using the chromium film 120 having a predetermined region opened or the chromium film 120 and the resist 130 as an etching resistant mask, and etching is performed to a predetermined depth. (FIG. 19 (c))
Etching of the chromium film is performed by dry etching using a chlorine-based gas or wet etching with an etchant composed of perchloric acid and ceric ammonium nitrate. When the processing material 110 is a quartz glass substrate (including a synthetic quartz substrate), dry etching is performed using a fluorine-based gas such as CF4 or CFH3.
In this way, after the first dry etching process is performed, the resist 130 is removed, and a resist 135 is newly provided on the entire surface of the dry etching processed part 411a (FIG. 19D). Drawing exposure and development are performed using the exposure data, only a predetermined region is opened, and the chromium film 120 exposed from the opening 136 is removed by etching (FIG. 19E). Using the chrome film 120 or the chrome film 120 with the resist 135 as an anti-etching mask, dry etching is performed and etching is performed to a predetermined depth. (FIG. 19 (f))
In this way, after the second dry etching process is performed, the resist 135 and the chromium film 120 are sequentially removed to obtain a target diffractive optical element. (Fig. 19 (h))
As described above, in the conventional manufacturing method shown in FIG. 19, the processing material surface of the optical element to be manufactured is approximated in a staircase shape by dry etching, and in all cases, resist coating, exposure, development, and drying are performed. It is necessary to repeat the series of processes a plurality of times (also referred to as multistage, but here twice).
And in order to repeat such a series of processes and form the target step part, the precision of high alignment is essential in each series of processes.

However, in such an optical element manufacturing process, due to inaccuracy of each processing apparatus, etc., in each process such as a drawing exposure process and an etching process, a manufacturing error caused by manufacturing such as an alignment error, an etching depth error, and a dimensional error. An error has occurred, and when these production errors occur, the characteristics (strength, efficiency, SN ratio, etc.) of the originally designed optical element cannot be obtained.
For example, in the case of an eight-step step-like diffractive optical element, the cross section thereof is as shown in FIG.
However, when the drawing exposure step 212 is different from the design value and has an error, even if there is no alignment error, a groove 215 may be formed at the step boundary as shown in FIG. .
Further, when there is an alignment error, as shown in FIG. 20C, even if there is no problem in the drawing exposure, an extra protrusion 216 and a groove 215 may be generated.
Even if there is no alignment error and there is no problem with drawing exposure, the height of the stepped portion may differ from the design value due to instability of the etching process, as shown in FIG. .
When these production errors occur, it is necessary to start over from the beginning of the optical element production process, which wastes time and materials.

  Under such circumstances, recently, technological advancement in the field of semiconductor lithography, nanotechnology, and optical members has been remarkable, and in such fields, the demand for application of diffractive optical elements with complex concavo-convex shapes has increased, The means of mass production has been demanded.

As described above, in recent years, with the spread of optical communication or the optical industry, the demand for diffractive optical elements, which are elements for controlling the traveling direction and phase of light depending on the element shape, has been increasing. The progress in technology in the fields of semiconductor lithography, nanotechnology, and optical materials is remarkable, and the demand for application of diffractive optical elements with complex concavo-convex shapes has increased.
There has been a demand for mass production means for these diffractive optical elements having complicated concavo-convex shapes.
The present invention corresponds to this, and a series of processing processes including the above-described conventional drawing exposure processing for selectively drawing exposure and patterning using the drawing exposure apparatus, and development processing, etching processing, and the like are repeatedly performed. In the manufacturing method of the step-like diffractive optical element, it is possible to eliminate the deterioration of the characteristics of the optical element due to the manufacturing error such as the alignment error, the etching depth error, and the dimensional error, and further, it is drastically compared with the method. Another object of the present invention is to provide a method for manufacturing a diffractive optical element with improved mass productivity.
Then, an object of the present invention is to provide a diffractive optical element capable of eliminating the deterioration of the characteristics of the diffractive optical element due to a manufacturing error when it is manufactured by the conventional stepwise diffractive optical element manufacturing method.

The method for producing a diffractive optical element according to the present invention is a method for producing a diffractive optical element for forming a diffractive optical element having an uneven surface by processing one surface of the processing substrate, In addition, using a reticle mask that arranges a photosensitive material layer and controls the distribution of transmitted light amount (exposure amount) during exposure according to the distribution state of fine dot patterns that are not resolved at the exposure wavelength, in a stepper exposure method, A first concavo-convex pattern forming step of exposing and developing the photosensitive material layer to form a first concavo-convex pattern using the photosensitive material layer as a material on one surface of a processing substrate; The first concavo-convex pattern and the one surface of the processing substrate are etched together from the concavo-convex pattern forming side to eliminate the first concavo-convex pattern, and the first concavo-convex pattern on the one surface of the processing substrate itself Pair with uneven pattern Was, the second uneven patterns formed as unevenness of the diffractive optical element, and characterized in that performing the second concavo-convex pattern forming step.
A method for manufacturing the diffractive optical element is characterized in that the projection exposure method is a stepper exposure method.
Further, in any one of the above-described diffractive optical element manufacturing methods, the reticle mask has a pattern forming plane as an XY coordinate, and transmission at a desired exposure as a function of the coordinate values x and y. The light amount (exposure amount) distribution is obtained as z = F (x, y) where z is the value on the Z coordinate, and the dot is positioned at the position on the XY coordinate at a density corresponding to the obtained z value. In the exposure, the reticle mask has a uniform illuminance on the reticle mask surface during exposure, and has a predetermined reproducibility corresponding to the z value on the Z coordinate. For each XY coordinate area of a predetermined size that is not resolved at the exposure wavelength, the algorithm determines whether or not a dot pattern of the area size is arranged, and the XY of the predetermined size is determined to have the pattern arrangement. Coordinate region The produces arranged dot pattern, obtained by performing a process of generating a dot pattern, using the pattern data is rendered exposed, is characterized in that those produced by photo-etching process.
The diffractive optical element manufacturing method according to claim 4, wherein the predetermined algorithm is an error dispersion method or an ordered dither method.
Alternatively, in the method for manufacturing a diffractive optical element according to claim 4, the predetermined algorithm is configured such that the reticle mask pattern region corresponds to a z value on the Z coordinate and a predetermined range of the z value. This is a pattern area divided dot arrangement method in which the dot pattern is generated and arranged at a predetermined predetermined density corresponding to each divided area.
Alternatively, in the method for manufacturing a diffractive optical element according to claim 4, the predetermined algorithm is a dot pattern formed by any one of an error dispersion method, an ordered dither method, and a pattern area division dot arrangement method. The pattern data obtained by generating and arranging is created, and in the created pattern data, the dot pattern density change from the ground with the area of the dot pattern density corresponding to the area where the amount of transmitted light in the reticle mask is maximum For a portion corresponding to a steeply changed portion of the concavo-convex pattern with a predetermined constant value or more, adjacent to the ground, the amount of transmitted light at the steeply changed portion corresponds to a maximum or minimum region. The dot pattern density region is replaced with data having a predetermined width and arrangement.

  The diffractive optical element of the present invention is a diffractive optical element in which one surface of a processing substrate is processed to provide unevenness, and is manufactured by the diffractive optical element manufacturing method according to any one of claims 1 to 7. It is characterized by this.

The reticle mask of the present invention is used when a photosensitive material layer disposed on one surface of a substrate is exposed by a stepper exposure method, and is exposed by a fine dot pattern distribution state that is not resolved at an exposure wavelength. A reticle mask for controlling the distribution of the transmitted light amount (exposure amount) of light, and the transmitted light amount (exposure amount) at the time of desired exposure as a function of the coordinate values x and y with the pattern formation plane as the XY coordinates The distribution is obtained by assuming that the value on the Z coordinate is z and z = F (x, y), and the dot pattern is arranged at the position on the XY coordinate at a density corresponding to the obtained z value. XY coordinates of a predetermined size that are not resolved at the exposure wavelength using a reproducible predetermined algorithm corresponding to the z value on the Z coordinate, assuming that the reticle mask surface is uniformly illuminated during exposure. For each area Dot pattern generation processing is performed in which the presence or absence of the dot pattern of the area size is determined, and the dot pattern is generated and arranged in the XY coordinate area of the predetermined size where the pattern arrangement is determined to be present. The obtained pattern data is used for drawing exposure and is produced by a photoetching process.
In the reticle mask, the error distribution method or the ordered dither method is used as the predetermined algorithm, the pattern data obtained by generating and arranging the dot pattern, or the error distribution as the predetermined algorithm. Method or ordered dither method is used, and a partial area of the pattern data obtained by generating and arranging the dot pattern corresponds to the predetermined algorithm, and the pattern area of the reticle mask corresponds to the z value on the Z coordinate. A dot pattern using a pattern area division dot arrangement method in which the dot pattern is generated and arranged at a predetermined predetermined density corresponding to each divided area. Of the pattern data obtained by generating and arranging the dot pattern arrangement of the area corresponding to the partial area, Obtained location, using the pattern data is rendered exposed, is characterized in that which has been produced by photo-etching process.

(Function)
The manufacturing method of the diffractive optical element of the present invention has such a configuration, so that the manufacturing error such as the alignment error, the etching depth error, and the dimensional error that occurs in the conventional stepwise diffractive optical element manufacturing method described above. It is possible to provide a method of manufacturing a diffractive optical element that can eliminate the deterioration of the characteristics of the optical element due to the above.
At the same time, it is possible to produce such a fine diffractive optical element.
Specifically, a photosensitive material layer is arranged on one surface of the processing substrate, and the transmitted light amount (exposure amount) distribution during exposure is controlled by the distribution of fine dot patterns that are not resolved at the exposure wavelength. The photosensitive material layer is exposed and developed by a projection exposure method using a reticle mask to form a first concavo-convex pattern using the photosensitive material layer as a material on one surface of a processing substrate. From the first concavo-convex pattern forming step and the first concavo-convex pattern forming side, the first concavo-convex pattern and one surface of the processing substrate are etched together, the first concavo-convex pattern disappears, and the processing By performing a second concavo-convex pattern forming step of forming a second concavo-convex pattern corresponding to the concavo-convex shape of the first concavo-convex pattern on one surface of the substrate for use as a concavo-convex pattern of the diffractive optical element, Achieve this That.
Specifically, the first first uneven pattern is formed using a reticle mask that controls the distribution of transmitted light amount (exposure amount) during exposure according to the distribution state of fine dot patterns that are not resolved at the exposure wavelength, and The first concavo-convex pattern and one surface of the processing substrate are etched together to eliminate the first concavo-convex pattern, and the one surface of the processing substrate itself corresponds to the concavo-convex shape of the first concavo-convex pattern. By forming the second concavo-convex pattern as the concavo-convex pattern of the diffractive optical element, the diffractive optical element can cope with the complicated concavo-convex shape, and has a diffraction efficiency higher than that of a conventional stepped diffractive optical element. It is possible to improve and improve the SN ratio.
At the same time, a fine diffractive optical element can be created.
Further, the projection exposure method is a stepper exposure method, and by adopting the aspect of the invention of claim 2, that is, adopting a stepper exposure method for exposure by reducing projection, the mass-productivity is improved. In addition, pattern data can be easily created. Compared with the conventional method of manufacturing a stepped diffractive optical element, mass productivity can be dramatically improved.
In addition, when the form performed by dry etching is adopted, a desired etching shape can be easily obtained and controlled as compared with wet etching.

As a reticle mask, the pattern formation plane is set as an XY coordinate, and the transmitted light amount (exposure amount) distribution at the time of desired exposure is set as a function of the coordinate values x and y, and the value on the Z coordinate is set as z. The form of the invention of claim 3 is obtained by arranging z = F (x, y) and arranging the dot pattern at a position on the XY coordinate at a density corresponding to the obtained z value. It is done. Specifically, the reticle mask has a predetermined size that is not resolved at the exposure wavelength by a predetermined algorithm with reproducibility corresponding to the z value on the Z coordinate, with a uniform illuminance on the reticle mask surface during exposure. For each XY coordinate area, the presence / absence of a dot pattern arrangement of the area size is determined, and a dot pattern is generated and arranged in an XY coordinate area of a predetermined size where the pattern arrangement is determined to be present The form of the invention of claim 4 is produced by a photo-etching process in which drawing exposure is performed using pattern data obtained by performing a dot pattern generation process.
More specifically, the predetermined algorithm may be an error dispersion method or an ordered dither method.
In this case, the concavo-convex shape of the diffractive optical element can be expressed continuously, and improvement in diffraction efficiency and improvement in the SN ratio can be expected.
Alternatively, the predetermined algorithm divides the pattern area of the reticle mask into a predetermined range of the z value corresponding to the z value on the Z coordinate, and corresponds to each divided area. The form of the invention of Claim 6 which is the pattern area division | segmentation dot arrangement | positioning method which produces | generates and arrange | positions the said dot pattern with a predetermined fixed density is mentioned.
In the form of the invention of claim 5, it is difficult to obtain steep unevenness by an actual process. However, in the form of the invention of claim 6, in order to obtain steep unevenness, the form of the invention of claim 5 is used. This is advantageous.
Alternatively, the predetermined algorithm is prepared by creating pattern data obtained by generating and arranging a dot pattern by any one of an error distribution method, an ordered dither method, and a pattern area division dot arrangement method. In the pattern data, the dot pattern density area corresponding to the area where the amount of transmitted light through the reticle mask is maximum is the ground, the change in the dot pattern density from the ground is a predetermined constant value or more, and the uneven pattern is abruptly changed. For a portion corresponding to a portion, a dot pattern density region corresponding to a region where the amount of transmitted light at the steeply changing portion is maximum and / or minimum adjacent to the ground is set to data having a predetermined width. The form of the invention of claim 7 which is to be replaced is mentioned.
In this case, the steep uneven area of the target diffractive optical element can be formed without impairing the actual process, thereby improving the diffraction efficiency and improving the S / N ratio. It is said.
When the photosensitive material layer is a negative type, the change in the dot pattern density from the ground is an area having a dot pattern density of 0 (0%), and the uneven pattern For a portion corresponding to the steep change portion, a dot pattern density region corresponding to the region where the amount of transmitted light in the steep change portion is maximum and minimum is arranged adjacent to the ground with a predetermined width. It replaces the data.
The same applies to the positive type.

  With such a configuration, the diffractive optical element of the present invention has characteristics of the optical element due to a manufacturing error in the case of the diffractive optical element manufactured by the above-described conventional stepwise diffractive optical element manufacturing method. It is possible to provide a diffractive optical element that can eliminate deterioration, improve the diffraction efficiency, and improve the SN ratio.

  With such a configuration, the reticle mask of the present invention is used in the method for manufacturing a diffractive optical element of the present invention, and the reticle mask of the diffractive optical element manufactured by the conventional method for manufacturing a stepped diffractive optical element is used. In this case, it is possible to manufacture a diffractive optical element that can eliminate the deterioration of the characteristics of the optical element due to a manufacturing error, and that can further improve the diffraction efficiency and improve the SN ratio. Yes.

As described above, the present invention eliminates the deterioration of the characteristics of the optical element due to the production errors such as the alignment error, the etching depth error, and the dimension error that occur in the conventional method for producing the stepped diffractive optical element. In addition, it is possible to provide a method for manufacturing a diffractive optical element, which is dramatically improved in mass productivity as compared with the method.
At the same time, it was possible to produce such a fine diffractive optical element.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a process flow chart of an example of an embodiment of a method for manufacturing a diffractive optical element of the present invention, FIG. 2 is a process flow chart for explaining a reticle mask manufacturing process, and FIG. FIG. 4 is a schematic diagram for explaining a simulation for obtaining a concavo-convex shape, FIG. 4 is a diagram showing the concavo-convex of a partial region of the diffractive optical element in shades, and FIG. 5 is a diagram showing a dot pattern corresponding to FIG. FIG. 6A is a view showing a desired uneven state of a resist for forming uneven portions of a desired diffractive optical element, and FIG. 6B is a view for a reticle mask manufactured by a pattern region dividing dot arrangement method. FIG. 6C is a diagram showing the dot pattern density of the portion corresponding to the portion of FIG. 6A of the pattern data, and FIG. 6C is a case where the dot pattern density of the portion shown in FIG. FIG. 7 (a) shows the location. FIG. 7B is a view showing a desired uneven state of the resist for forming the unevenness of the diffractive optical element, and FIG. 7B is a pattern data for the reticle mask produced by the ordered dither method in FIG. 7A. FIG. 7C is a diagram showing a case where the dot pattern density at a portion corresponding to the portion is replaced, and FIG. 7C is a diagram showing a case where the dot pattern density at the portion shown in FIG. FIG. 8A is a view showing an exposure amount distribution of a photomask pattern for obtaining a desired resist profile after development. FIG. 8B is a diagram showing a predetermined X in the exposure amount distribution shown in FIG. FIG. 9 is a diagram showing a list of values z on the Z coordinate at the Y coordinate position, FIG. 9 is a diagram for explaining the ordered dither method, and FIG. 10 is a diagram showing a dither matrix with a maximum value of 1. FIG. 11 is a diagram for explaining the error dispersion method. FIG. 13 is a diagram showing a result of performing the error variance method based on a list of values z on the Z coordinate at predetermined XY coordinate positions shown in FIG. 8, and FIG. 13 shows an error variance method using an error variance matrix. FIG. 14 is a diagram illustrating examples of various dither matrices, FIG. 15A is a diagram illustrating various scanning directions of the error dispersion method, and FIG. FIG. 16 is a diagram showing an example of an error dispersion matrix, FIG. 16 is a diagram showing the relationship between the remaining resist film thickness after development and the amount of transmitted light, and FIG. 17 is an explanation from stepper exposure to the formation of irregularities on one surface of the processing substrate. It is process drawing for doing.
S1-S9 in FIG. 1 and S11-S23 in FIG. 2 indicate processing steps in S31-S39 in FIG.
In FIG. 4, the whiter is convex and the black is concave, and in FIG. 5, the region with more white parts has a larger amount of transmitted light (exposure amount).
In FIG. 17, the optical system (lens system) is omitted.
6, 7, and 17, 310 is a reticle mask, 320 and 320 A are exposure light, 330 is a resist, 335 is a resist residual film portion, 336 is a first uneven pattern, 340 is a processing substrate, and 346 is a first substrate. 2 is an uneven pattern, 350 is an XY stage, 410 is a ground, 420 is a steep portion, 430 is a replacement portion, D0 is a (predetermined) constant value, and W0 is a predetermined width.

An example of an embodiment of a method for producing a diffractive optical element of the present invention will be described below.
The method for producing a diffractive optical element of this example is a method for producing a diffractive optical element for forming a diffractive optical element having an uneven surface by processing one surface of a processing substrate. As a general rule, the process shown in FIG. The processing is performed as shown in the flowchart.
First, the outline of the processing flow in this example will be described with reference to FIG.
First, a plate-shaped processing substrate made of a photorefractive medium is prepared (S1), and a negative photosensitive material layer is disposed on one surface of the processing substrate (S2). Using a reticle mask (S9) for controlling the distribution of transmitted light amount (exposure amount) during exposure according to the distribution state of fine dot patterns that do not image, the photosensitive material layer is exposed by a stepper exposure method (S3), Development (S4) is performed to form a first concavo-convex pattern made of a cured material using the photosensitive material layer on one surface of the processing substrate. (S5)
Next, from the first concavo-convex pattern forming side, the first concavo-convex pattern and one surface of the processing substrate are etched together by a dry etching method so that the first concavo-convex pattern disappears, and the processing substrate A second concavo-convex pattern forming step is performed in which a second concavo-convex pattern corresponding to the concavo-convex shape of the first concavo-convex pattern is formed on one surface itself as the concavo-convex pattern of the diffractive optical element. (S6-S7)
As shown in FIG. 17A, the pattern of the reticle mask 210 is reduced and projected onto a resist 230 applied on one surface of the processing substrate 240 through an optical system (lens system) (not shown). Exposed.
Thereafter, development is performed to form a first concavo-convex pattern 236 as shown in FIG.
Further, dry etching is performed to form a second concavo-convex pattern 246 as shown in FIG.
Normally, after forming the first concavo-convex pattern 236 as described above, the method of further forming the second concavo-convex pattern 246 by dry etching is also referred to as a back etching method.
Then, a diffractive optical element is obtained through a cleaning process and the like. (S8)

The reticle mask used in the processing flow shown in FIG. 1 can be manufactured by the manufacturing process shown in FIG.
A photosensitive resist material (also simply referred to as a resist) that obtains a desired post-development profile and an exposure wavelength for exposing the photosensitive resist material are determined in advance. (S11, S12)
First, a predetermined photosensitive resist material is applied on a substrate equivalent to the substrate on which the developed profile is formed to a predetermined film thickness, and an area of a predetermined size is exposed and developed with various exposure amounts. (S13), the relationship data of the exposure amount and the remaining film thickness of the resist is obtained. (S14)
From this, it is good also as the relationship data of the exposure amount and the residual film thickness of the resist which were formulated.
When a negative resist is used as the photosensitive resist material and exposure is performed with a reticle mask, the relationship between the exposure amount, that is, the amount of light transmitted through the reticle mask and the remaining film thickness is usually as shown in FIG.
In FIG. 16, both the transmitted light amount (exposure amount) and the remaining film thickness are normalized.
Depending on the resist image after development, the relational data of the amount of transmitted light and the remaining film thickness varies depending on the shape and density of the pattern, so it is necessary to incorporate several types of data corresponding to the pattern state.
In addition, if the remaining film thickness characteristic with respect to the transmitted light amount of the photosensitive resist material for obtaining a desired post-development profile is known, the relationship data between the transmitted light amount and the remaining film thickness is obtained each time. It is not always necessary.
Using the relational data between the transmitted light amount (exposure amount) and the residual film thickness of the resist, the exposure amount distribution of the photomask pattern corresponding to the desired profile (S16) of the workpiece is obtained. (S17)
The desired profile of the diffractive optical element can be obtained, for example, by simulation as shown in FIG.
A series of processes from S13 to S14 and S15 to S16 to S17 is a transmitted light amount (exposure amount) distribution grasping process.
Normally, a correction formula optimized for the resist, exposure system, etc. is applied to the profile function to be obtained.
The pattern formation plane of the reticle mask is taken as an XY coordinate, and the transmitted light amount (exposure amount) distribution is expressed as a z value on the Z coordinate with the coordinate values x and y as a function.
Here, z = F (x, y) and the transmitted light amount (exposure amount) distribution are represented.
For example, the exposure dose distribution of a simple spherical recess is represented as shown in FIG.
On the other hand, the size of the pattern area of the reticle mask that is not resolved by stepper exposure with a predetermined exposure wavelength is determined to be a predetermined size. (S18)
Here, it is set as the X direction width a and the Y direction width a.
As described above, in addition to the optical resolution depending on the exposure wavelength, the desired profile of the resist after development and the performance constraints of the lithography tool used for reticle mask fabrication are determined. .
Next, exposure is performed by using a predetermined algorithm (S19) having reproducibility based on the obtained relationship data of z = F (x, y) and the size of the pattern area that is not resolved at the determined exposure wavelength. Presence / absence of arrangement of a dot pattern of a predetermined size that is not resolved at the wavelength is determined for each region divided into the size on the XY coordinates. (S20)
Examples of the predetermined algorithm include an error dispersion method, an ordered dither method, and a pattern area division dot arrangement method.
Based on this determination, a CAD tool creates a pattern data by arranging a dot pattern at a predetermined position on the XY coordinates. (S21)
A series of processes from S19 to S21 described above is a dot pattern generation process.
In this way, the pattern data can be created. For example, in the case of the uneven shape shown in FIG. 4, the pattern data corresponding to the transmitted light amount (exposure amount) distribution z = F (x, y) is error variance. According to the method and the ordered dither method, it is as shown in FIG.
In FIG. 4, it is shown that the white is convex and the black is concave, and in FIG. 5, the region where the white part is large indicates that the transmitted light amount (exposure amount) is large.
In FIG. 5, the smallest square black dot portion is an area of unit dots (also referred to as a unit pattern), the black portion area is configured as a set of black dot portions of this unit, and the white portion is the unit It is an area without dots.
The size of the unit dot is a predetermined size that is not resolved at the exposure wavelength.

Here, a simulation for obtaining desired phase information or profile data of the diffractive optical element shown in FIG. 3 will be briefly described.
In FIG. 3, the optical conditions on the input surface and the output surface are set to predetermined optical conditions, respectively, and the target intensity distribution on the output surface is Fourier-transformed from the phase distribution, The first processing step (S32 to S34) for generating phase information of the diffractive optical element and inverse Fourier transform from the phase information obtained in the first processing step under a predetermined convergence condition to obtain the target intensity An intensity distribution and a phase distribution on the output surface as a simulation result of an image corresponding to the distribution are obtained (S34 to S37), and a new target value is set based on the distribution and the first processing step. The phase information of the diffractive optical element is obtained by an iterative algorithm that repeatedly performs the second processing step as input data (S38).
When the target intensity distribution falls within a predetermined allowable range, the phase information of the diffractive optical element at that time is used as processing data as information of a newly produced diffractive optical element.
The predetermined optical condition is, for example, that the constraint condition on the input surface of the diffractive optical element is a constant intensity distribution, and the constraint condition on the output surface is a target intensity distribution.
In this manner, data of a desired profile of the diffractive optical element can be obtained from the phase information of the obtained folding optical element.
The convergence condition in the simulation is, for example, that the number of iterations of the iterative algorithm is N, and when N is reached, the phase information of the diffractive optical element at that time indicates the desired profile of the diffractive optical element. Data.
As another method, the target value and the calculated value are constantly compared, the diffraction efficiency, the SN ratio, the flatness of the intensity distribution, etc. are obtained, and the phase information at the time when the predetermined condition is satisfied is used. The data of the desired profile is used.

The ordered dither method is known as a method mainly used for halftone processing in printing such as newspapers and magazines, comparing the density value of the original image with a sequence of numbers called a dither matrix, Compare the original image and the dither matrix, as shown in the illustration, by determining whether the pixel is white or black. If the number in the original image is larger, the point is black. The white operation is performed on the entire image while shifting.
By doing this, pixels with intermediate density values are converted into white and black at an appropriate ratio, and white and black pixels are mixed appropriately when viewed from a distance, as in the case of halftone processing. Accordingly, intermediate gradations can be expressed.
As will be described later, the error diffusion method first classifies the pixel density value as white or black depending on whether it is larger or smaller than an intermediate density value (for example, 128 for 256 gradations), and then the original image. This is a method in which the error between the density value after conversion and the density value after conversion is distributed to the intervening pixels at an appropriate ratio. If the original image is converted to black, it becomes black in the surrounding pixels. The pixel is changed to a white pixel at an appropriate ratio.
In this way, pseudo gradation can be expressed in the entire image.
In addition, the pattern region divided dot arrangement method referred to here is an XY region (pattern) for each predetermined range of the z value corresponding to the z value with respect to the transmitted light amount (exposure amount) z = F (x, y). Area), and for each divided area, the dot pattern is generated and arranged at a predetermined constant density corresponding to each of the divided areas.
The ordered dither method, error diffusion method, and pattern area division dot arrangement method are all reproducible methods.

Here, the exposure dose distribution for obtaining a desired developed profile is the exposure dose distribution shown in FIG. 8A, z = F1 (x, y), and the z value at each position (x, y) is shown in FIG. Only the procedure for applying the ordered dither method will be briefly described with reference to FIG.
The table shown in FIG. 8B is the same as the table of FIG. 9A, but the z values at the respective positions are arranged as in the table of FIG. 9A.
On the other hand, for example, in accordance with the arrangement of the table shown in FIG. 9A, a dither matrix of 4 rows × 4 columns with the maximum value shown in FIG. 10 as 1 is arranged as shown in FIG.
Here, the arrangement of the table of FIG. 10A and the arrangement of the table of FIG. 10B are compared for each corresponding position, and the front side of FIG. As shown in FIG. 10 (c), a similar arrangement is obtained with 1 being smaller than the side and 0 being not.
Here, in the case of the 1 region, the dot pattern is not arranged, and in the case of the 0 region, the dot pattern is arranged.
Although it is preferable in terms of accuracy to make the X-direction and Y-direction sizes of the dot pattern the same as the distances between positions shown in FIG. 9A, the amount of calculation becomes large.
Note that the X-direction and Y-direction sizes of the dot pattern and the distances between positions shown in FIG. 9A are not necessarily the same.
Further, various patterns as shown in FIG. 14 are conceivable for the dither matrix, which are appropriately selected and used according to the exposure distribution to be obtained.

Next, a case where the error variance method is applied will be described.
First, the procedure of the error dispersion method will be briefly described with reference to FIG.
For example, the horizontal direction of the table is the vertical direction as the X direction and the Y direction, and cells (also referred to as pixels, which have a size corresponding to the pitch) are provided at predetermined pitches, and each cell is as shown in FIG. When the values are arranged, the following processing is sequentially performed from the upper left to the lower right of the table.
First, binarization is performed for the upper left cell P0 with the intermediate value (0.5) as a threshold value. (FIG. 11 (b)
The value 0.1 of the upper left cell P0 becomes 0 by binarization.
Next, weighted addition (or subtraction) is performed on the cells adjacent to the cell P0, as shown in FIG.
In FIG. 11B, circles 1, 2, and 3 indicate adjacent cells to be weighted (or subtracted) from the cell P0 and their values.
Next, the process moves to the adjacent cell P1, and binarization and weighted addition (or subtraction) are performed to obtain FIG. 11 (d).
Further, the process moves to the cell P2 next to it, and similarly, it is converted into a value and weighted (or subtracted) to obtain FIG. 11 (e).
Thereafter, the same processing is sequentially performed on each cell in the direction of the arrow in FIG. 11E, and the obtained result is obtained.

The table shown in FIG. 8B is as shown in FIG.
That is, in the case of the exposure amount distribution shown in FIG. 8A and Z = F1 (x, y), in the case of the 1 area shown in FIG. 12, the dot pattern is not arranged, and the 0 area shown in FIG. In this case, it is an area where a dot pattern is arranged.
In the above, the processing is sequentially performed from the upper left to the lower right of the table as shown in FIG. 15A, but the present invention is not limited to this.
You may process in the direction of FIG.15 (b) and FIG.15 (c).

Error variance is repeated for all cells in sequence starting from coordinates (0, 0) using an error variance matrix as shown in FIGS. 15 (b), (b), and (b), (b). There is also a method. f (x, y) is original data, fnew (x, y) is data after error variance, g (x, y) is binarized with a threshold value of 0.5, and Exy is binarized. In the case of an error that has occurred, the respective relationships are expressed as equations (1) to (5) in FIG.
Based on these relational expressions, an array corresponding to FIG. 12 can be obtained in the same manner as described above.

As described above, the manufacturing method of the diffractive optical element of this example is performed, but the method is not limited to this. For example, in the pattern data obtained by generating and arranging the dot pattern for the reticle mask of this example, the dot pattern density from the area corresponding to the area where the amount of transmitted light in the reticle mask is maximum is the ground. For locations where the change in density is equal to or greater than a predetermined constant value and corresponds to a steeply changed portion of the concavo-convex pattern, the dot pattern density corresponding to the region where the amount of transmitted light in the reticle mask is minimum is adjacent to the ground. A form example using pattern data in which an area is replaced with data having a predetermined width is also included.
For example, when producing a diffractive optical element using a negative photosensitive material layer, the desired concavo-convex state of the resist for forming the concavo-convex of the desired diffractive optical element is as shown in FIG. In FIG. 6B, the dot pattern density of the pattern data for the reticle mask produced by the pattern area division dot arrangement method corresponding to this is as shown in FIG.
Here, in FIG. 6B, assuming that the dot pattern density is 0 (0%) in the ground 410, the change in the dot pattern density from the ground 410 is a predetermined constant value or more, and the uneven pattern is abruptly changed. As shown in FIG. 6C, the portion corresponding to the portion (the steep portion 420) is adjacent to the ground 410 and has an area where the dot pattern density is 1 (100%) and 0 (0%). Are replaced with data arranged in a predetermined width.
Here, the predetermined constant value of the change in the dot pattern density is D0, and the predetermined width is W0.
By doing so, it is possible to prevent the unevenness of the actually produced diffractive optical element from being reduced and the high frequency characteristics from being deteriorated.
Further, when the uneven state of a desired cross section of the resist for forming the unevenness of the desired diffractive optical element is expressed as shown in FIG. 7A, it is produced by an ordered dither method corresponding to this. The dot pattern density of the reticle mask pattern data is as shown in FIG. 7B. Similarly, the steep portion 420 is adjacent to the ground 410 as shown in FIG. 7C. Then, by replacing the area where the dot pattern density is 1 (100%) and the area where the dot pattern density is 0 (0%) with the predetermined data W0 and the arranged data, the unevenness of the actually produced diffractive optical element Therefore, it is possible to prevent the high frequency characteristics from being deteriorated.

It is a processing flowchart of one example of embodiment of the manufacturing method of the diffractive optical element of this invention. It is a processing flowchart for demonstrating the manufacturing process of a reticle mask. It is the schematic for demonstrating the simulation which obtains the uneven | corrugated shape of a diffractive optical element. It is the figure which displayed the unevenness | corrugation of the one part area | region of a diffractive optical element with the shading. It is the figure which showed the dot pattern corresponding to FIG. FIG. 6A is a view showing a desired uneven state of a resist for forming uneven portions of a desired diffractive optical element, and FIG. 6B is a view for a reticle mask manufactured by a pattern region dividing dot arrangement method. FIG. 6C is a diagram showing the dot pattern density of the portion corresponding to the portion of FIG. 6A of the pattern data, and FIG. 6C is a case where the dot pattern density of the portion shown in FIG. FIG. FIG. 7A is a view showing a desired uneven state of a resist for forming uneven portions of a desired diffractive optical element, and FIG. 7B is a pattern data for a reticle mask manufactured by an ordered dither method. FIG. 7C shows a dot pattern density at a location corresponding to the location of FIG. 7A, and FIG. 7C shows a case where the dot pattern density at the location shown in FIG. 7B is partially replaced. It is a figure. FIG. 8A shows a photomask pattern exposure distribution for obtaining a desired resist profile after development, and FIG. 8B shows the exposure distribution shown in FIG. 8A. It is the figure which showed the list of the value z on the Z coordinate in a predetermined XY coordinate position. It is a figure for demonstrating the ordered dither method. It is the figure which showed the dither matrix which made the maximum value 1. It is a figure for demonstrating an error dispersion method. It is the figure which showed the result of having implemented the error dispersion method based on the list of the value z on the Z coordinate in the predetermined XY coordinate position shown in FIG. It is a figure for demonstrating the error dispersion method using an error dispersion matrix by numerical formula. It is a figure showing the example of various dither matrices. FIG. 15A is a diagram showing various scanning directions of the error variance method, and FIG. 15B is a diagram showing examples of various error variance matrices. It is the figure which showed the relationship between the residual film thickness of the resist after image development, and the transmitted light amount. It is process drawing for demonstrating from stepper exposure to the uneven | corrugated formation to one surface of the board | substrate for a process. It is a figure for demonstrating a step-like diffractive optical element. It is a figure for demonstrating the manufacturing method of a step-like diffractive optical element. It is a figure for demonstrating a production error.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Processing material 11 Discontinuous slope part 12 Step part 12a Step part 110 Processing material 111, 111a Dry etching processing part 120 Chromium film 130 Resist 131 Opening 135 Resist 136 Opening 210 Processing material 212 Step part 215 Groove part 216 Protrusion part (Wall)
217 Defect defect portion 218 Depth defect portion 310 Reticle mask 320, 320A Exposure light 330 Resist 335 Resist residual film portion 336 First uneven pattern 340 Processing substrate 346 Second uneven pattern 350 XY stage 410 Base 420 Steep portion 430 Replacement unit D0 (predetermined) constant value W0 predetermined width

Claims (10)

  A method for producing a diffractive optical element for processing a surface of a processing substrate to form a diffractive optical element having unevenness, wherein a photosensitive material layer is disposed on one surface of the processing substrate, The photosensitive material layer is exposed and developed by a projection exposure method using a reticle mask that controls the distribution of transmitted light amount (exposure amount) during exposure according to the distribution of fine dot patterns that cannot be resolved at the exposure wavelength. Then, a first concavo-convex pattern forming step of forming a first concavo-convex pattern using the photosensitive material layer as a raw material on one surface of the processing substrate, and the first concavo-convex pattern forming side from the first concavo-convex pattern forming side The first concavo-convex pattern and the one surface of the processing substrate are etched together to eliminate the first concavo-convex pattern, and the second surface of the processing substrate itself corresponds to the concavo-convex shape of the first concavo-convex pattern. Concave and convex pattern on diffractive optical element Formed as unevenness, a method for manufacturing a diffractive optical element, characterized in that it performs a second concavo-convex pattern forming step.   2. The method for producing a diffractive optical element according to claim 1, wherein the projection exposure method is a stepper exposure method.   3. The method of manufacturing a diffractive optical element according to claim 1, wherein the reticle mask has a pattern forming plane as an XY coordinate and a desired function as a function of coordinate values x and y. The distribution of the transmitted light amount (exposure amount) at the time of exposure is obtained as z = F (x, y) where z is the value on the Z coordinate, and on the XY coordinate at a density corresponding to the obtained z value. A method for producing a diffractive optical element, wherein the dot pattern is arranged at the position of.   4. The method of manufacturing a diffractive optical element according to claim 3, wherein the reticle mask has a reproducible predetermined value corresponding to a z value on the Z coordinate, with a uniform illuminance on the reticle mask surface in exposure. For each XY coordinate area of a predetermined size that is not resolved at the exposure wavelength, the algorithm determines whether or not a dot pattern of the area size is arranged, and the XY of the predetermined size is determined to have the pattern arrangement. Diffraction characterized by being produced by a photo-etching process in which a pattern of pattern data obtained by performing dot pattern generation processing is used to generate and place a dot pattern in the coordinate area. A method for manufacturing an optical element.   5. The method for manufacturing a diffractive optical element according to claim 4, wherein the predetermined algorithm is an error dispersion method or an ordered dither method.   5. The method for producing a diffractive optical element according to claim 4, wherein the predetermined algorithm is configured to change a pattern area of the reticle mask for each predetermined range of z values corresponding to z values on the Z coordinates. A method for producing a diffractive optical element, which is a pattern area divided dot arrangement method, wherein the dot pattern is generated and arranged at a predetermined predetermined density corresponding to each divided area.   5. The method for manufacturing a diffractive optical element according to claim 4, wherein the predetermined algorithm generates and arranges a dot pattern by any one of an error dispersion method, an ordered dither method, and a pattern area division dot arrangement method. The pattern data obtained in the above is created, and in the created pattern data, a dot pattern density change corresponding to the area where the amount of transmitted light through the reticle mask corresponds to the maximum area is a predetermined change in the dot pattern density from the ground. For locations that are equal to or greater than a certain value and that correspond to the steeply changed portion of the concavo-convex pattern, the dot pattern density corresponding to the region where the amount of transmitted light at the steeply changed portion is maximum and minimum adjacent to the ground. A method for producing a diffractive optical element, wherein the region is replaced with data having a predetermined width.   A diffractive optical element in which a surface of a processing substrate is processed to provide unevenness, wherein the diffractive optical element is manufactured by the method for manufacturing a diffractive optical element according to any one of claims 1 to 7. element.   The amount of transmitted light (exposure amount) at the time of exposure due to the distribution of fine dot patterns that are not resolved at the exposure wavelength used when exposing the photosensitive material layer disposed on one side of the substrate by the stepper exposure method A reticle mask for controlling the distribution, wherein the pattern formation plane is an XY coordinate, and the transmitted light amount (exposure amount) distribution at the time of desired exposure is expressed as a function of the coordinate values x and y on the Z coordinate. The value is z, and z = F (x, y) is obtained, and the dot pattern is arranged at a position on the XY coordinate at a density corresponding to the obtained z value. A uniform illuminance on the surface, corresponding to the z value on the Z coordinate, using a reproducible predetermined algorithm, for each area of the XY coordinate of a predetermined size that is not resolved at the exposure wavelength Size dot pattern Pattern data obtained by performing dot pattern generation processing in which a dot pattern is generated and arranged in an area of XY coordinates of a predetermined size where the presence or absence of the pattern is determined and the pattern is determined to be present A reticle mask, which is produced by a photo-etching process, which is drawn and exposed using a mask. The reticle mask according to claim 9, wherein the predetermined algorithm uses an error dispersion method or an ordered dither method, uses pattern data obtained by generating and arranging a dot pattern, or as the predetermined algorithm. Using the error dispersion method or the ordered dither method, a partial area of the pattern data obtained by generating and arranging the dot pattern is used as the predetermined algorithm, and the pattern area of the reticle mask is changed to the z value on the Z coordinate. Correspondingly, using a pattern area divided dot arrangement method that divides into each predetermined range of the z value and generates and arranges the dot pattern with a predetermined predetermined density for each divided area. Replace the pattern data obtained by generating and arranging the dot pattern with the dot pattern arrangement of the area corresponding to the partial area. Arrangement was obtained, using the pattern data is rendered exposure, the reticle mask which is characterized in that which has been produced by photo-etching process.