JP2005258349A - Method for forming a microlens array - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a microlens array capable of accurately controlling a lens shape.
Using a photomask pattern formation plane as an XY coordinate and using the coordinate values x and y as a function, the amount of transmitted light (exposure) at the time of exposure corresponding to a desired developed resist image shape (profile) Amount) distribution is obtained as a z value on the Z coordinate, and the dot pattern is arranged at a position on the XY coordinate corresponding to the obtained z value, and the transmitted light amount (exposure amount) distribution is controlled. Using the corrected photomask as a starting photomask and using the corrected photomask corrected from the starting photomask, the lens forming material made of a photosensitive resist material is exposed and further developed to form a microlens array into the developed resist. Get as an image.
[Selection] Figure 1

Description

The present invention provides a moving image in the form of color or luminance information in each pixel by two-dimensionally arranging photosensitive parts on a surface on which light passing through a camera lens forms an image and converting the intensity of the light into an electrical signal. Or a method of forming a microlens array used as a component of an imaging device that outputs a still image,
More specifically, the present invention relates to a method of forming a microlens array used as a component of an imaging apparatus such as a digital still camera, a digital video camera, a camera incorporated in a mobile phone, a security surveillance camera, or the like. .
However, the use of the microlens array produced by the forming method of the present invention is not limited to the above.

2. Description of the Related Art In recent years, an imaging apparatus that includes a camera lens and a solid-state imaging device in which photosensitive portions are two-dimensionally arranged on an imaging plane of light passing through the camera lens and outputs a moving image or a still image has For the purpose of improving sensitivity and reducing noise, as shown in FIG. 17, in order to increase the light collection efficiency to the photosensitive part, a micro condenser lens (hereinafter referred to as transparent condenser material) is formed on the light receiving part side surface of each cell. , Also referred to as a microlens).
Such a lens may be simply referred to as a refracting portion.
Here, based on FIG. 17 which is a schematic configuration diagram of the imaging apparatus, such an imaging apparatus will be briefly described.
In FIG. 17, D1 is a cross section of the central portion of the imaging unit, D2 is a cross section of the peripheral portion, and the others are omitted.
A combination of the photosensitive portion 125, the planarizing layer 171, the light-shielding portion 150, the color filter 140, and the planarizing layer microlens is referred to as a cell as a unit of photosensitive functional area, as indicated by D0 in FIG. Laid on the imaging surface side.
The cross section of the cell along the image sensor surface is often a square, but may be a rectangle or a regular hexagon, and the pitch size is generally about 3 μm to 12 μm at present.
The photosensitive unit 125 is disposed at the bottom of the cell, and converts the light intensity into an electric signal according to the intensity of light incident thereon.
A digital image is output by performing an interpolation process on the electrical signal output from the photosensitive unit 125.
Due to the necessity of arranging metal wiring or the like inside the cell, it is difficult to provide a photosensitive portion over the entire bottom surface of the cell, and the region of the photosensitive portion 125 is a portion of the bottom surface region of the cell.

A light beam passing on the optical axis 115 of the camera lens 110 enters the photosensitive portion 125 of the solid-state imaging device 120 perpendicularly and increases the incident angle θ0 that is obliquely incident as the distance from the optical axis 115 increases. In order to collect light efficiently, it is necessary to shift the positional relationship between the position of the microlens 130 from the optical axis 115 and the photosensitive portion by a predetermined amount.
Such shifting is referred to as pixel shifting, and conventionally, pixel shifting has prevented a decrease in the amount of light around.
The inventor previously changed the direction of the incident light normal by changing the shape of the microlens (referred to as a refracting portion) at each position in Japanese Patent Application No. 2003-307287 (Patent Document 1). A method has been proposed in which the effect of preventing a decrease in the amount of light received by the photosensitive portions of the peripheral cells is controlled more effectively.

In such a micro condensing lens (microlens), conventionally, a resin part formed on the upper side of the condensing part is formed in a lens shape by heat flow.
An example of this method will be briefly described below based on FIG.
In this example, a small concentration of light corresponding to each photosensitive portion 303 is obtained with respect to a device substrate 301 (FIG. 16A) in which a color filter 304 is disposed on the upper side of the photosensitive portion 303 formed on one surface of the silicon wafer 302. This is a case where a lens is provided.
First, a planarization layer 305 that covers the color filter 304 of the device substrate 301 is provided, and a resist layer 306 that is a photosensitive resin for forming a lens is applied on the planarization layer 305. (Fig. 16 (b))
Next, the resist layer 306 is selectively exposed in a state where the photomask 307 is close to the resist layer 306 (FIG. 16C), and development processing is performed so as to cover the photosensitive portions 303 in areas corresponding to the respective photosensitive portions 303. A square resist pattern 309 is formed. (Fig. 16 (d))
Thereafter, the resist pattern 309 is heat-flowed by heat treatment to form a convex lens 310 corresponding to each photosensitive portion 303. (Fig. 16 (e))
In the case of this method, since the resist pattern 309 is formed into a convex lens shape by heat flow, it is difficult to form a lens having a desired focal length and a high light collection efficiency.
In particular, in a CMOS image sensor having a long distance to the photosensitive portion, a lens shape as designed with a long focal length cannot be formed by natural flow by heat treatment.
A method for forming a microlens by such a manufacturing method is disclosed in, for example, Japanese Patent Laid-Open No. 10-98173 (Patent Document 2).

Separately, Japanese Patent Application Laid-Open No. 5-1422752 (Patent Document 3) discloses a method of creating a micro condensing lens by changing the transmittance using a fine dot pattern distribution.
However, in the case of this method, microlenses are formed by etch back, and in the mask pattern creation, a method of arranging patterns by random numbers is adopted, so an accurate desired transmitted light amount profile is obtained. It was difficult to get.
In addition, the inventors of the present application previously described in Japanese Patent Application No. 2002-230593 (Patent Document 4), the transmitted light amount (exposure amount) distribution during exposure based on the distribution state of fine dot patterns that are not resolved at the exposure wavelength. Have proposed a method of producing pattern data for producing a photomask for controlling the photomask, and such a photomask.

Japanese Patent Application No. 2003-307287 JP-A-10-98173 Japanese Patent Laid-Open No. 5-142752 Japanese Patent Application No. 2002-230593

As described above, in recent years, in an imaging device such as a digital still camera, a digital video camera, a camera incorporated in a mobile phone, a security surveillance camera, a microlens array has been provided as a component, There is a need for a forming method that can accurately control the lens shape of the microlens array.
The present invention responds to this, and an object of the present invention is to provide a method for forming a microlens array in which the lens shape can be accurately controlled.

The method for forming a microlens array of the present invention uses a photomask 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. A method for forming a microlens array, wherein a microlens array comprising microlenses arranged two-dimensionally is obtained as a resist image after development by exposing and developing a lens forming material comprising: Using the pattern formation plane of the mask as XY coordinates and using the coordinate values x and y as a function, the transmitted light amount (exposure amount) distribution during exposure corresponding to the desired resist image shape (profile) is expressed as Z. Obtained as the z value on the coordinates, and corresponding to the obtained z value, the dot pattern is arranged at a position on the XY coordinates, and the transmitted light amount (exposure amount) For forming a lens made of a photosensitive resist material using a photomask with a controlled distribution as a starting photomask, using the starting photomask, or using a photomask in which the arrangement state of a part of the dot pattern of the starting photomask is changed The material is exposed, further developed, and a microlens array is obtained as a resist image after development. The shape (profile) of the resist image after development is measured, and the shape of the resist image after development is measured. A dot pattern is arranged by grasping the difference between the (profile) and the desired developed resist image shape (profile) and correcting the transmitted light amount (exposure amount) distribution of the photomask based on the difference. A new correction photomask that controls the distribution of the transmitted light amount (exposure amount) and uses the correction photomask to create a photosensitive register. Exposing the lens forming material comprising a preparative material, and further developed, a microlens array, it is characterized in that to obtain a resist image after development.
Alternatively, in the method for forming a microlens array of the present invention, a lens forming material made of a positive photosensitive resist material is exposed using a photomask, further developed, and then microlenses arranged two-dimensionally. A microlens array is obtained by developing a microlens array as a resist image after development, and the amount of transmitted light (exposure amount) during exposure depends on the distribution of fine dot patterns that are not resolved at the exposure wavelength. Exposure is performed with a photomask for controlling the distribution, and the pattern formation plane of the photomask is set to XY coordinates, and the coordinate values x and y are used as functions to correspond to the shape (profile) of a desired resist image after development. The transmitted light amount (exposure amount) distribution at the time is obtained as a z value on the Z coordinate, and the dot is placed at a position on the XY coordinate corresponding to the obtained z value. After the first exposure, the first photomask, which is a photomask in which turns are arranged and the distribution of the transmitted light amount (exposure amount) is controlled, is used to expose a lens forming material made of a photosensitive resist material. Furthermore, a second photomask having a pattern shape in which only a region corresponding to a predetermined region including a lens boundary portion of the microlens array to be formed is used, and a predetermined portion including the lens boundary portion of the microlens array to be formed is used. The region is exposed, second exposure is performed, and further development is performed to obtain a microlens array as a resist image after development.
Here, “the desired resist image shape (profile) after development” means the shape of the resist image after development corresponding to the design shape of the microlens array (workpiece) to be produced.

In any one of the above-described microlens array formation methods, the starting photomask according to claim 1 and the first photomask according to claim 2 are sequentially formed from (a) the photosensitive resist material. In order to obtain a desired post-development profile of a lens forming material, a photomask pattern exposure amount distribution is obtained, and the photomask pattern forming plane is taken as XY coordinates, and the coordinate values x and y are functions. Assuming that the transmitted light amount (exposure amount) distribution of the target photomask is expressed as a z value on the Z coordinate, and (b) uniform illumination on the photomask surface in the exposure. In accordance with the z value on the Z coordinate, a dot having the size of the region is obtained for each XY coordinate region of a predetermined size that is not resolved at the exposure wavelength by using a reproducible predetermined algorithm. The pattern obtained is determined by determining whether or not to place a turn and generating and arranging a dot pattern in an XY coordinate area of a predetermined size where the pattern is determined to be present. It is formed by drawing exposure using data.
In the microlens array forming method, the transmitted light amount (exposure amount) distribution grasping process is performed by exposing and developing a resist (photosensitive resist material) whose remaining film thickness changes according to the exposure amount. Then, from the obtained data on the relationship between the exposure amount and the residual film thickness of the resist and the profile of the shape of the desired workpiece (microlens array), the resist (photosensitive layer) whose residual film thickness changes according to the exposure amount In order to obtain a desired profile of the resist after development of the photosensitive resist material), the exposure amount distribution of the photomask pattern is obtained. A photomask having a flat mesh pattern was produced by using a predetermined number of gradations of flat mesh pattern data as drawing data, each having a predetermined number of white area ratio regions set in stages. Using a photomask, the lens forming material made of the photosensitive resist material is exposed and developed, and the change in the thickness of the lens forming material made of the photosensitive resist material at each gradation is measured. A tone curve showing the relationship between the white area ratio of the flat mesh pattern and the film thickness of the lens forming material made of the photosensitive resist material is obtained, and the transmitted light amount (exposure amount) distribution is obtained from the tone curve. It is characterized by this.

(Function)
The microlens array forming method of the present invention can provide a microlens array forming method capable of accurately controlling the lens shape by adopting such a configuration.
Specifically, it is a photomask 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 pattern formation plane of the photomask is an XY coordinate. Using the coordinate values x and y as a function, the transmitted light amount (exposure amount) distribution at the time of exposure corresponding to the desired resist image shape (profile) is obtained as the z value on the Z coordinate. Forming a lens made of a photosensitive resist material using only a photomask in which the dot pattern is arranged at a position on the XY coordinate corresponding to the z value and the transmitted light amount (exposure amount) distribution is controlled. When the material is exposed and further developed to obtain a microlens array as a developed resist image, the resist film thickness may be different even with the same transmitted light amount (exposure amount).
For example, a phenomenon occurs in which a portion that becomes a V-shaped valley between lenses of a microlens array is buried and smoothed in a developed resist image.
By adopting such a configuration, the shape accuracy is good, and in particular, it is possible to form a microlens array while suppressing smoothing of a V-shaped valley between adjacent lenses.

The starting photomask according to claim 1 and the first photomask according to claim 2 sequentially obtain (a) a desired post-development profile of the lens forming material made of the photosensitive resist material. For this purpose, the exposure amount distribution of the photomask pattern is obtained, the photomask pattern formation plane is taken as the XY coordinates, and the coordinate values x and y are used as functions, and the transmitted light amount (exposure amount) of the target photomask. Processing for grasping the transmitted light amount (exposure amount) distribution, which represents the distribution as a z value on the Z coordinate, and (b) a uniform illuminance on the photomask surface in the exposure, and reproduction corresponding to the z value on the Z coordinate Using a predetermined algorithm, the presence / absence of the dot pattern arrangement of the area size is determined for each area of the XY coordinate of the predetermined size that is not resolved at the exposure wavelength, and the pattern arrangement is determined to be present In the region of the XY coordinate of a predetermined size, a dot pattern is generated and arranged, a dot pattern generation process is performed, and the obtained pattern data is used to perform drawing exposure. The transmitted light amount (exposure amount) distribution grasping process is performed by exposing and developing a resist (photosensitive resist material) whose remaining film thickness changes according to the exposure amount, and obtaining the exposure amount and the remaining resist film thickness. Photo to obtain the desired profile of the resist after development of the resist (photosensitive resist material) whose remaining film thickness varies with the exposure amount from the relationship data and the profile of the desired workpiece shape An exposure amount distribution of the mask pattern is obtained.
Specifically, the preferable transmitted light amount (exposure amount) distribution grasping process uses a predetermined number of gradations of flat net pattern data having a predetermined number of areas of each white area ratio set in stages as drawing data. Then, a photomask having a flat mesh pattern is manufactured, and using the prepared photomask, the lens-forming material made of the photosensitive resist material is exposed and developed, and the lens made of the photosensitive resist material in each gradation. By measuring the change in film thickness of the forming material, a tone curve indicating the relationship between the white area ratio of the flat pattern of the photomask and the film thickness of the lens forming material made of the photosensitive resist material is obtained, From the tone curve, a transmitted light amount (exposure amount) distribution is obtained, and this process enables the actual process to be performed accurately and reliably.

The present invention has made it possible to provide a method for forming a microlens array in which the lens shape can be accurately controlled as described above.
As a result, it is possible to improve the sensitivity of the imaging device and reduce noise in the output image.
Of course, a microlens with a more ideal shape can be obtained as compared with a conventional manufacturing method by heat melting.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic flowchart showing a processing flow of a first example of an embodiment of a method for forming a microlens array of the present invention, and FIG. 2 is a flowchart of a first embodiment of a method for forming a microlens array of the present invention. FIG. 3 is a schematic flow chart showing the processing flow of Example 2, and FIG. 3 is a photomask having an exposure amount distribution corresponding to a desired developed resist image shape (profile) used in the first and second examples. FIG. 4A is a sectional view showing the shape (profile) of a resist image after development of the designed shape, and FIG. 4B is a resist after development of the designed shape. FIG. 4C and FIG. 4D are cross-sectional views showing the shape (profile) of a resist image after development when a photomask having a transmitted light amount distribution corresponding to the shape (profile) of FIG. , Second frame in the second example Is a plan view showing an example pattern of the mask.
1 to 4, reference numeral 10 denotes a processing substrate, 20 denotes a lens (also referred to as a microlens), 25 denotes a skirting portion, 31 denotes a light shielding portion, and 32 denotes an opening (light transmission portion).

First, a first example of an embodiment of a method for forming a microlens array of the present invention will be described with reference to FIG.
The microlens array forming method of the first example is a positive type using a photomask 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. A microlens array forming method of obtaining a microlens array consisting of two-dimensionally arranged microlenses as a resist image after development by exposing a lens forming material made of a photosensitive resist material and developing the same It is.
Briefly, the amount of transmitted light (exposure) in exposure corresponding to the shape (profile) of a desired developed resist image, using the pattern formation plane of the photomask as XY coordinates and the coordinate values x and y as functions. Amount) distribution is obtained as a z value on the Z coordinate, and the dot pattern is arranged at a position on the XY coordinate corresponding to the obtained z value, and the transmitted light amount (exposure amount) distribution is controlled. Using this photomask as a starting photomask, test exposure, development, grasping of the resist image shape after development, and pattern correction are performed at least once, and a part of the starting photomask is corrected. Producing a photomask, using the correction photomask for producing the product, exposing a lens-forming material made of a photosensitive resist material disposed on the processing substrate for the product, further developing, The Lee Black lens array, but obtained as the developed resist image.
First, from a design shape (S1) of a lens to be formed, a transmitted light amount (exposure amount) distribution at the time of exposure corresponding to a desired resist image shape (profile) after development is obtained as a z value on the Z coordinate. A photomask in which the dot pattern is arranged at a position on the XY coordinate corresponding to the obtained z value and the distribution of the transmitted light amount (exposure amount) is controlled is produced as a starting photomask (S2). deep.
A method for manufacturing the starting photomask (S2) will be described later.
Using the starting photomask (S2), the lens forming material of the test processing substrate (S3) coated with the photosensitive lens forming material is subjected to test exposure (S4), further developed (S5), and a microlens array. Is obtained as a resist image after development,
Measure the shape (profile) of the developed resist image (S6),
Grasp the difference between the measured shape (profile) of the developed resist image and the desired developed resist image (profile) (design shape S1) (S7);
Based on the difference, if necessary, the corrected photo of the transmitted light amount (exposure amount) distribution of the starting photomask is corrected (S9), the dot pattern is arranged and the transmitted light amount (exposure amount) distribution is controlled. A new mask (S10) is produced.
Then, this time, using the corrected photomask that has been corrected, the processing steps S4 to S7 are performed. If the difference is not required to be corrected, the correction photomask is used.
The substrate for the product (S11) on which the lens forming material is coated (photographed lens forming material) is exposed (S12), further developed (S13), and the microlens array is formed (substrate for the imaging device). (S14) is obtained.
In this way, it is possible to form a microlens array having a designed shape and excellent accuracy. Note that exposure and development using the correction photomask (S10) are still different from the design shape, and if it is determined that correction is necessary, a series of processing steps S9 to S10 and S4 to S8 are required. Repeat as needed.

Next, a second example of the embodiment of the method for forming a microlens array of the present invention will be described with reference to FIG.
Similarly to the first example, the microlens array forming method of the second example is a photo that controls the distribution of transmitted light amount (exposure amount) at the time of exposure according to the distribution state of fine dot patterns that are not resolved at the exposure wavelength. Using a mask, the lens-forming material made of a positive photosensitive resist material is exposed and further developed to obtain a microlens array made up of microlenses arranged two-dimensionally as a resist image after development. In the case of the second example, the microlens array forming method is simply adjacent to the first photomask that performs exposure for forming the lens shape (referred to as first exposure). Using a second photomask that performs exposure (referred to as second exposure) for correcting a phenomenon in which the portion between the lenses that is designed to have a V-shaped valley is in a skirted state, the processing substrate is exposed to light. Sex Regis The exposure to the lens forming material comprising a material performed twice, and developed, it is a method of forming a microlens array.
In terms of design, as shown in FIG. 4A, the boundary between adjacent lenses 20 is V-shaped valleys so as to reach the substrate 10, but exposure is performed using the first photomask. In the case of development, normally, as shown in FIG. 4B, the boundary between adjacent lenses 20 does not reach the substrate 10, and the space between the lenses 20 is filled with a lens forming material (this is referred to as a skirt 25). This was a problem.
The second example is an attempt to form a lens without a tail (25 in FIG. 4).
First, from the design shape and arrangement (S21) of the microlens array, the pattern formation plane of the photomask is taken as the XY coordinates, and the coordinate values x and y are used as functions, and the shape (profile) of the desired resist image after development. The transmitted light amount (exposure amount) distribution at the time of exposure corresponding to is obtained as a z value on the Z coordinate, and the dot pattern is arranged at a position on the XY coordinate corresponding to the obtained z value. A photomask whose transmission light amount (exposure amount) distribution is controlled is prepared as a first photomask (S22),
On the other hand, from the design shape and arrangement (S21) of the microlens array, a photomask for exposing a predetermined area including a boundary area between adjacent lenses is created and placed as a second photomask (S23).
As the second photomask, for example, as shown in FIG. 4C, a picture having an opening in the shape of a cross, a part of the opening shown in FIG. The thing of the pattern shape as shown in FIG.4 (d) which replaced the opening of the vicinity by the light-shielding part is used.
Then, the first exposure using the first photomask (S22) is performed on the lens forming material of the processing substrate (S24) for manufacturing the product coated with the lens forming material made of a positive photosensitive resist material. (S25), followed by second exposure (S26) using the second photomask (S23) and further development (S27) to obtain a substrate on which a microlens array is formed. (S28)
In this way, it is possible to form a microlens array with no tailing and excellent accuracy.

Here, a manufacturing method of the starting photomask in the first example and the first photomask in the second example will be described based on the flow shown in FIG.
In advance, a photosensitive resist material (also simply referred to as a resist) that is a microlens forming material for obtaining a desired post-development profile and an exposure wavelength for exposing the photosensitive resist material are determined. (S31, S32)
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. (S33) The relationship data between the exposure amount and the remaining film thickness of the resist is obtained. (S34)
It is good also as the relational data of the exposure amount and the residual film thickness of the resist which were numerically represented.
When a positive resist is used as the photosensitive resist material, the relationship between the transmitted light amount (exposure amount) and the remaining film thickness is usually as shown in FIG.
In FIG. 14, the transmitted light amount (exposure amount) and the remaining film thickness are also normalized.
Depending on the developed resist image to be developed, the relational data of the exposure amount 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 exposure amount of the photosensitive resist material for obtaining a desired post-development profile is known, the relationship data between the exposure amount and the remaining film thickness is obtained each time. It is not always necessary.
More specifically, a photomask having a flat mesh pattern is prepared by using a predetermined number of gradations of flat mesh pattern data having a predetermined number of stepwise set white area ratio regions as drawing data. By using the produced photomask, exposing and developing a lens forming material made of a photosensitive resist material, and measuring the change in film thickness of the lens forming material made of the photosensitive resist material at each gradation, Data on the relationship between the exposure amount and the residual film thickness of the resist is obtained by a method of obtaining a tone curve indicating the relationship between the white area ratio of the flat mesh pattern of the photomask and the film thickness of the lens forming material made of the photosensitive resist material. From the viewpoint of reproducibility in product production, it is preferable.

Here, the flat screen pattern will be briefly described by taking a 16-tone flat screen pattern as an example.
When a predetermined entire area is divided into 4 × 4 minute square unit areas, and each unit area is regarded as one unit block (also referred to as one dot) for gradation expression, a unit block The predetermined whole area composed of 16 can express 17 gradations with white area ratios of 0/16, 1/16, 2/16,..., 16/16.
However, 0/16 is excluded because there is no step between the peripheral portion of the exposure amount 0 and the pattern is meaningless. That is 16 gradations.
As described above, each gradation level of 16 gradations having a predetermined whole area composed of 16 unit blocks and having a white area ratio of 1/16, 2/16,..., 16/16. A pattern that expresses a uniform gray level within a predetermined area (entire area) is called a “16-gradation flat screen pattern”.
The unit area is an individual dot constituting a halftone image.
A binary image in which intermediate gray is expressed by a minute dot pattern consisting of binary values of white and black, such as this 16 gradation flat mesh pattern, is called a halftone image.
For example, 400 mm, 320 mm, or the like is used as the dot pitch that is the length of one side of the unit region.
Such a 16-tone flat screen pattern is usually generated using the “ordered dither method”.

Next, using such relationship data between the exposure amount and the residual film thickness of the resist, the exposure amount distribution of the photomask pattern that matches the desired profile (S35) of the workpiece is obtained. (S37)
A series of processes from S33 to S35 to S37 or from S36 to S37 is a transmitted light amount (exposure amount) distribution grasping process.
Normally, a correction formula optimized for a resist exposure system or the like is applied to a profile function to be obtained.
The photomask pattern formation plane is taken as an XY coordinate, and the exposure value distribution is expressed as a z value on the Z coordinate by using the coordinate values x and y as a function.
Here, it is expressed as z = F (x, y), and is obtained as shown in FIG.
On the other hand, the size of the pattern area of the photomask that is not resolved at the determined exposure wavelength is determined to be a predetermined size. (S38)
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 expression of the resist after development and the performance restrictions of the lithography tool used for photomask production are determined. .
Next, exposure is performed by using a predetermined algorithm (S39) having reproducibility from the obtained relational 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. (S40)
Examples of the predetermined algorithm include an error dispersion method and an ordered dither 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. (S41)
A series of processes from S19 to S21 described above is a dot pattern generation process.
In this way, pattern data can be produced. The pattern data corresponding to the exposure amount distribution, z = F (x, y) shown in FIG. 5A is as shown in FIG. 5B. .

Here, the exposure amount distribution for obtaining a desired post-development profile is the exposure amount distribution shown in FIG. 6A, z = F1 (x, y), and the z value at each position (x, y) is shown in FIG. For the case shown in the table of FIG. 6 (b), only the procedure will be briefly described based on FIG. 4 for the case where the ordered dither method is applied.
The table shown in FIG. 6B is the same as the table in FIG. 7A, but the z values at each position are arranged as in the table in FIG. 7A.
On the other hand, for example, in accordance with the arrangement of the table shown in FIG. 7A, a dither matrix of 4 rows × 4 columns with the maximum value shown in FIG. 8 as 1 is arranged as shown in FIG.
Here, the arrangement of the table of FIG. 7A and the arrangement of the table of FIG. 7B are compared for each corresponding position, and the front side of FIG. As shown in FIG. 7C, a similar arrangement is obtained, where 1 is smaller than the side and 0 is not otherwise.
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 the positions shown in FIG. 7A, the amount of calculation increases.
Note that the X-direction and Y-direction sizes of the dot pattern and the distances between the positions shown in FIG.
Further, various patterns as shown in FIG. 12 are conceivable for the dither matrix, and they are appropriately selected and used according to the exposure distribution desired 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 are sizes 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. 9 (b)
The value 0.1 of the upper left cell P0 becomes 0 by binarization.
Next, weighting addition (or subtraction) is performed on a cell adjacent to the cell P0, as shown in FIG. 9C.
In FIG. 9B, numbers 1, 2, and 3 surrounded by circles (circled numbers) indicate adjacent cells to be weighted (or subtracted) from the cell P0 and their values.
Next, the process proceeds to the adjacent cell P1, and binarization and weighted addition (or subtraction) are performed to obtain FIG. 9D.
Furthermore, it moves to the cell P2 next to it, and similarly, it is converted into a value and weighted (or subtracted) to obtain FIG. 9 (e).
Thereafter, the same processing is sequentially performed on each cell in the direction of the arrow in FIG. 6E, and the obtained result is obtained.

The table shown in FIG. 6B is as shown in FIG.
That is, in the case of the exposure amount distribution shown in FIG. 6A, Z = F1 (x, y), the area 1 shown in FIG. 10 is an area where no dot pattern is arranged, and the area 0 shown in FIG. In this case, it is an area where a dot pattern is arranged.
In the above description, as shown in FIG. 13A, the processing is sequentially performed from the upper left to the lower right of the table. However, the present invention is not limited to this.
Processing may be performed in the direction of FIGS. 13B and 13C.

Error variance is repeated for all cells in sequence starting from coordinates (0, 0) using an error variance matrix as shown in FIGS. 13 (b) (a) and 13 (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 in equations (1) to (5) in FIG.
Based on these relational expressions, an array corresponding to FIG. 10 can be obtained in the same manner as described above.

Next, using the pattern data in which the dot patterns are arranged as described above, the resist on the light shielding layer of the photomask substrate is exposed and drawn with an electron beam drawing exposure apparatus (S42). A photomask (S43) of the present invention is manufactured through process processes such as development and etching.
For example, when forming a lens with a photosensitive resist material on a substrate to be processed (image sensor substrate) using a photomask manufactured in this manner, as shown in FIG. The pattern of the mask 210 is exposed to a resist 230 on a substrate to be processed (image sensor substrate) by reduction projection, developed, and then on the substrate to be processed (image sensor substrate) 240 as shown in FIG. A lens can be obtained directly.
In this way, the starting photomask of the first example and the first photomask of the second example are manufactured.

As described above, it is effective to obtain the relationship between the exposure amount and the remaining film thickness in accordance with the pattern of the resist image after development to be produced, but it is not practical when there are many types to be obtained. Therefore, there is a method in which the pattern of the developed resist image to be produced is made to correspond by using simulation (S36).

It is the general | schematic flowchart which showed the process flow of the 1st example of embodiment of the formation method of the micro lens array of this invention. It is the general | schematic flowchart which showed the processing flow of the 2nd example of embodiment of the formation method of the micro lens array of this invention. It is a flowchart for demonstrating the manufacturing flow of the photomask of the exposure amount distribution corresponding to the shape (profile) of the resist image after the desired image development used for the 1st example and the 2nd example. 4A is a cross-sectional view showing the shape (profile) of a resist image after development of the designed shape, and FIG. 4B is a transmitted light amount distribution corresponding to the shape (profile) of the resist after development of the designed shape. FIGS. 4C and 4D are cross-sectional views showing the shape (profile) of a resist image after development when the photomask of FIG. 4 is used, respectively. It is the top view which showed the pattern of one example of. FIG. 5A shows the pattern formation plane of the photomask as XY coordinates, the coordinate values x and y as functions, and the transmitted light amount (exposure amount) distribution during desired exposure as a value z on the Z coordinate. FIG. 5B shows a photomask pattern. FIG. 6A shows a photomask pattern exposure dose distribution for obtaining a desired resist profile after development, and FIG. 6B shows the exposure dose distribution shown in FIG. 6A. 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. 13A is a diagram showing various scanning directions of the error variance method, and FIG. 13B 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 the figure which showed the relationship between the mask and the residual film profile of the photosensitive lens material (resist) after image development. It is process sectional drawing which showed the process of the formation method of the conventional minute condensing lens. It is a schematic block diagram of an example of the conventional imaging device.

Explanation of symbols

10 processing substrate 20 lens (also called microlens)
25 Bottoming part 31 Shading part 32 Opening part (light transmission part)
DESCRIPTION OF SYMBOLS 110 Camera lens 115 Optical axis 120 Image pick-up element 125 Photosensitive part 130 Micro lens (it is also called a refractive part)
140 Color filter 150 Light-shielding part 160 Light rays 171 and 172 Flattening layer 210 Photomask 211 Transparent substrate 212 Light-shielding film 220 and 220A Exposure light 230 Photosensitive material layer 235 that is a material for forming a microlens (refractive part) Refraction after development Photosensitive material layer 240 that is a material for forming a part 240 Substrate substrate (image sensor substrate) for forming a microlens (refractive part) 301 Device substrate (image sensor substrate)
302 Silicon wafer 303 Photosensitive portion (also referred to as light receiving portion)
304 Color filter 304a Flattening layer 305 Flattening layer 306 Resist layer 307 Photomask 308 Exposure light 309 Resist pattern (resist image after development)
310 Convex lens (resist image after heat flow)

Claims (5)

  Using a photomask that controls the distribution of the transmitted light amount (exposure amount) during exposure according to the distribution state of fine dot patterns that cannot be resolved at the exposure wavelength, the lens forming material made of a photosensitive resist material is exposed. A method for forming a microlens array, which is developed to obtain a microlens array composed of two-dimensionally arranged microlenses as a resist image after development, wherein the pattern formation plane of the photomask is an XY coordinate Using the coordinate values x and y as a function, the transmitted light amount (exposure amount) distribution at the time of exposure corresponding to the desired resist image shape (profile) is obtained as the z value on the Z coordinate. A photomask in which the dot pattern is arranged at a position on the XY coordinate corresponding to the z value and the transmitted light amount (exposure amount) distribution is controlled is set as a starting photomask. Using the starting photomask, or using a photomask in which the arrangement of part of the dot pattern of the starting photomask is changed, the lens forming material made of a photosensitive resist material is exposed and further developed. Then, a microlens array is obtained as a resist image after development, the shape (profile) of the resist image after development is measured, and the shape (profile) of the resist image after development and the desired development after development are measured. The difference between the resist image shape (profile) and the distribution of the transmitted light amount (exposure amount) of the photomask is corrected based on the difference. A correction photomask with a control method is newly prepared, and the correction photomask is used to expose a lens forming material made of a photosensitive resist material. And developed, forming a microlens array, characterized in that a microlens array is obtained as the developed resist image.   A lens-forming material made of a positive photosensitive resist material is exposed using a photomask, further developed, and a microlens array made up of two-dimensionally arranged microlenses is used as a developed resist image. A method for forming a microlens array, comprising: a photomask that controls a distribution of a transmitted light amount (exposure amount) at the time of exposure according to a distribution state of a fine dot pattern that is not resolved at an exposure wavelength; Using the pattern formation plane as the XY coordinates and the coordinate values x and y as functions, the transmitted light amount (exposure amount) distribution corresponding to the shape (profile) of the desired developed resist image on the Z coordinate The dot pattern is arranged at a position on the XY coordinate corresponding to the obtained z value, and the transmitted light amount (exposure amount) distribution is controlled. The first photomask, which is a photomask, is used to expose a lens forming material made of a photosensitive resist material. After the first exposure, the first photomask further includes a lens boundary portion of the microlens array to be formed. Using a second photomask having a pattern shape in which only the region corresponding to the region is opened, a predetermined region including the lens boundary portion of the microlens array to be formed is exposed, subjected to the second exposure, and further developed. A method of forming a microlens array, wherein the microlens array is obtained as a resist image after development.   3. The method of forming a microlens array according to claim 1, wherein the starting photomask according to claim 1 and the first photomask according to claim 2 are: ) Obtaining the exposure distribution of the photomask pattern to obtain the desired post-development profile of the lens forming material comprising the photosensitive resist material, and using the photomask pattern forming plane as the XY coordinates, A transmitted light amount (exposure amount) distribution grasping process for expressing the transmitted light amount (exposure amount) distribution of the target photomask as a z value on the Z coordinate using the coordinate values x and y as a function, and (b) a photo in exposure. The mask surface has a uniform illuminance, and corresponding to the z value on the Z coordinate, using a reproducible predetermined algorithm, for each XY coordinate area of a predetermined size that is not resolved at the exposure wavelength, Determine the presence or absence of the arrangement of the dot pattern of the area size, perform the dot pattern generation processing to generate and arrange the dot pattern in the area of the XY coordinates of the predetermined size, where the pattern arrangement is determined to be present, A method of forming a microlens array, wherein the pattern data obtained is used for drawing exposure.   4. The method for forming a microlens array according to claim 3, wherein the transmitted light amount (exposure amount) distribution grasping process is performed by exposing a resist (photosensitive resist material) whose remaining film thickness changes according to the exposure amount, and developing Then, from the obtained data on the relationship between the exposure amount and the residual film thickness of the resist and the profile of the shape of the desired workpiece (microlens array), the resist whose residual film thickness changes according to the exposure amount A method for forming a microlens array, which is to obtain a photomask pattern exposure distribution to obtain a desired resist profile after development of (photosensitive resist material). 5. The method of forming a microlens array according to claim 4, wherein the transmitted light amount (exposure amount) distribution grasping process includes a predetermined number of gradation areas each having a predetermined white area ratio area. Using the net pattern data as drawing data, a photomask having a flat net pattern is produced, and using the produced photomask, the lens forming material made of the photosensitive resist material is exposed and developed, By measuring the change in the film thickness of the lens forming material made of the photosensitive resist material in the tone, the white area ratio of the flat mesh pattern of the photomask and the film thickness of the lens forming material made of the photosensitive resist material A method for forming a microlens array, wherein a tone curve indicating a relationship is acquired, and a transmitted light amount (exposure amount) distribution is obtained from the tone curve.

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