JP4941233B2 - Solid-state imaging device and imaging apparatus using the same - Google Patents

Description

  The present invention relates to a solid-state imaging device and an imaging device, and more particularly, to a solid-state imaging device in which a plurality of light receiving units and minute condensing lenses (microlenses) are arranged, and an imaging device using the solid-state imaging device.

In recent years, digital cameras and video cameras that capture still images and moving images have become widespread in various fields. These cameras use solid-state image sensors such as CCDs and CMOSs. However, with the advancement of semiconductor technology, the pixels of the solid-state image sensors have been further miniaturized, and the cameras themselves have been downsized. In such a solid-state imaging device, a microlens for increasing the amount of light incident on the light receiving portion and improving the sensitivity is provided corresponding to the light receiving portion of each pixel.
Here, the solid-state imaging device has a phenomenon called shading in which the sensitivity decreases around the effective imaging region. In this shading, as shown in FIG. 17, the light incident from the camera lens is incident substantially perpendicularly at the center of the effective imaging area, whereas the incident angle increases toward the periphery of the effective imaging area, and the effective imaging area This is a phenomenon caused by a decrease in the amount of incident light on the light receiving unit 51 at the periphery.

Conventionally, in order to prevent shading, in consideration of the chief ray incident angle from the camera lens, the microlens 52 is arranged at the position of the light receiving unit 51 at the center of the effective imaging region, and light is received at the periphery of the effective imaging region. The micro lenses 52 are arranged so as to be shifted from the positions of the portions 51 (see FIG. 18). For example, the arrangement pitch of the microlenses is set slightly smaller than the arrangement pitch of the light receiving portions by arranging the microlenses by performing microscaling from the center of the effective imaging region toward the peripheral portion. (Patent Document 1). As a result, there is no deviation between the position of the light receiving unit and the microlens at the center of the effective imaging area, but the position of the microlens gradually shifts toward the center of the effective imaging area with respect to the corresponding position of the light receiving unit as it moves toward the periphery. It becomes. In addition, it has been proposed to correct shading by increasing the curvature of the microlens from the center of the effective imaging region toward the periphery (Patent Document 2). Here, it is proposed to change the curvature of the microlens, but there is no description of specific means.
JP-A-6-140609 JP-A-5-227468

As miniaturization of digital cameras, video cameras, etc. progresses, the camera lens optical system also becomes smaller and thinner, and the camera lens is arranged close to the solid-state image sensor, so the effective imaging area of the solid-state image sensor In the peripheral area, the incident angle of the chief ray incident from the camera lens becomes larger and more precise shading correction is required.
For example, in the method of correcting shading caused by camera lens characteristics as shown in FIG. 19 by changing the above-described microlens curvature to change the condensing efficiency of the microlens, the center of the effective imaging region is corrected. A method of changing the radius of curvature of the microlens gradually and nonlinearly from the periphery toward the periphery can be considered. In this case, it is conceivable that the curvature is slightly changed for each pixel, that is, between the adjacent microlenses. However, each design is performed over all the pixels from several million to ten million or more. Is a huge process. In addition, the amount of change in the curvature of the microlens is expected to be at most several tens of percent or less over the entire effective imaging region, and the amount of change is small to slightly change the curvature between adjacent microlenses. Too much.

  For example, assuming that the cross-section of the microlens is a part of a spherical surface and the curvature thereof is changed by 50%, an image pickup device having 2592 × 1944 pixels (about 5 million pixels) and a pixel size of 2 μm is used. Consider shading correction by changing the curvature. Here, the curvature is the strongest at the center of the effective imaging area and is 100% (the radius of curvature is the smallest), and then the curvature is set to 50% of the center of the effective imaging area at the 2592/2 = 1296th outermost pixel in the X-axis direction. (The radius of curvature is the maximum). Also, the height of the microlens is constant at 0.3 μm, the bottom shape of the microlens is circular, and the bottom diameter of the microlens at the outermost pixel is 2.0 μm. In this case, the microlens at the outermost peripheral pixel has a bottom diameter of 2.0 μm, a curvature radius of 1.817 μm (maximum curvature radius = 100%), and a height of 0.3 μm. The lens has a bottom diameter of 1.349 μm, a radius of curvature of 0.908 μm (curvature radius minimum = 50%), and a height of 0.3 μm. When the change of the difference of 0.651 μm between the bottom diameter 2.0 μm and the bottom diameter 1.349 μm is averaged over 1296 pixels, the change amount per pixel is 0.651 μm / 1295 = 0.5027 nm. Become.

  When a microlens is manufactured by a normal registry flow method, that is, by photolithography, for example, a cylindrical resist pattern is formed and then heated and melted to form a lens shape, a microlens photomask is used. The dimension corresponding to the bottom diameter of each microlens is changed by 0.5027 nm per pixel. This is 2.514 nm on the pentaploid photomask, and when the grid at the time of drawing the photomask is 5 nm, it does not conform to the grid. Further, even if mask drawing data is generated by ignoring fractions in the 1 nm grid of the minimum grid, the drawing data amount becomes enormous, resulting in a long mask drawing time and an increase in mask manufacturing cost.

On the other hand, shading correction can be performed by changing the curvature of the microlens stepwise. In this case, for example, in order to change the radius of curvature of the microlens as shown in FIG. 20 for shading correction, as shown in FIG. The radius of curvature is gradually changed between the partial regions. 21 represents the radius of curvature of the microlens shown in FIG. However, there is always a boundary line between the partial areas where microlenses with different radii of curvature exist (parts where the light collection efficiency changes stepwise). There is a problem in that adjacent portions are continuous, which causes linear sensitivity unevenness and greatly impairs product quality.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a solid-state imaging device that prevents shading and an imaging apparatus that uses such a solid-state imaging device.

In order to achieve such an object, a solid-state imaging device according to the present invention includes a plurality of light receiving units arranged two-dimensionally at a predetermined pitch, and a plurality of microlenses arranged two-dimensionally corresponding to each of the light receiving units. In the solid-state imaging device having at least the microlens array formed, the microlens constituting the microlens array is composed of two or more types of microlenses having different radii of curvature, and the effective imaging area extends from the center toward the periphery. A microlens having the same radius of curvature is arranged in each partial area, and each of the curvatures in the adjacent partial areas is adjacent to the boundary where the partial areas having different curvature radii are adjacent to each other. intermediate strip portion is present in which the radius of the microlenses are mixed, Ri difference der 10% or less of the radius of curvature of the adjacent microlenses, Mai The average radius of curvature of the Lorenz tends to increase from the center of the effective imaging area toward the periphery, and the arrangement of microlenses with different curvature radii in the intermediate band portion is a uniform arrangement with a mixture ratio of 1: 1. or mixed ratio of 1: 0 to 0: continuously arranged so as to vary within a range, or to obtain a random arrangement der so that configuration.

In addition, the present invention includes at least a plurality of light receiving portions that are two-dimensionally arranged at a predetermined pitch, and a microlens array in which a plurality of microlenses are two-dimensionally arranged corresponding to each of the light receiving portions. In the solid-state imaging device, the microlens constituting the microlens array includes two or more types of microlenses having different radii of curvature, and the effective imaging area is divided into a plurality of partial areas from the center toward the periphery, and the plurality of parts the area, there are partial areas such as the curvature radius of different microlenses are mixed, the difference is der 10% or less of the radius of curvature of the adjacent microlenses is, the average radius of curvature of the microlens, effective The radius of curvature tends to increase from the center of the imaging area toward the periphery, and the radius of curvature differs in the partial area where microlenses with different curvature radii are mixed. The arrangement of microlenses with different curvature radii varies along the direction from the center to the periphery of the effective imaging area within the partial area, and the microlenses with a small curvature radius have a curvature radius. at least one arrangement located around side of the effective image pickup area than the larger microlens, or mixed ratio is uniform arrangement in the partial area, or to a random arrangement der so that configuration.

As another aspect of the present invention, the partial region has a mosaic shape.
As another aspect of the present invention, the partial area is configured to be a concentric annular area centered on the center of the effective imaging area.
The imaging apparatus of the present invention is configured to include the above-described solid-state imaging device.

Such a solid-state imaging device of the present invention can arrange a microlens having an optimal radius of curvature suitable for lens characteristics such as a relationship between a principal ray incident angle of a camera lens and an image height, and performs precise shading correction. And the difference in the radius of curvature between adjacent microlenses is 10% or less, so that the sensitivity variation is small, and a pentaploid mask can be produced by electron beam drawing. The complicated operation of individually designing the microlenses for the entire region at the design stage is not necessary, and an effect is achieved that precise shading correction can be easily performed.
The image pickup apparatus of the present invention is of high quality with low loss of vignetting and the like due to oblique incidence within the effective image pickup area, and with a low efficiency distribution with respect to the amount of incident light. Thinning is possible.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Solid-state imaging device]
FIG. 1 is a schematic configuration diagram showing an example of a solid-state imaging device of the present invention. In FIG. 1, a solid-state imaging device 1 is opposed to a substrate 2 via a substrate 2 having a plurality of light receiving portions 3 and a light shielding film 4 provided at a constant arrangement pitch, and a passivation layer 5 having a light shielding layer 6. The lower planarization layer 7, the color filter 8, the upper planarization layer 9, and the microlens array 10 are stacked. The microlens array 10 includes a plurality of microlenses 11 that are two-dimensionally arranged so as to correspond to the individual light receiving units 3. And the microlens 11 which comprises the microlens array 10 with respect to the several light-receiving part 3 provided with the fixed arrangement | positioning pitch consists of 2 or more types of microlenses from which a curvature radius differs. In addition, the solid-state image sensor of this invention is not limited to the structure shown in FIG.

Here, formation of microlenses having different radii of curvature will be described.
First, an ordinary microlens forming method in which a photoresist is exposed and developed to form a resist pattern, which is melted by heat to form a convex lens will be described. In this case, the radius of curvature is changed by changing the size of the portion corresponding to the bottom surface of the microlens of the photomask for forming the microlens. FIG. 2 is a drawing showing one pixel of a photomask for forming a microlens. In FIG. 2, the black portion is a light shielding portion of the mask and is an octagon with a square corner cut off, but is not limited to this, and may be a rectangle or a polygon other than an octagon. Further, it may be circular, elliptical or the like. In the illustrated example, A is the pitch of the microlens arrangement, and D is the dimension corresponding to the microlens bottom surface dimension. Then, if a plurality of types of D are set according to the desired radius of curvature and a photomask having a desired arrangement is produced, a plurality of types of curvature radii can be obtained by one-time photoresist coating, exposure, development, and thermal melting. A microlens array can be formed. In the illustrated example, the X-axis direction and the Y-axis direction have the same dimensions, but the present invention is not limited to this. For example, in a digital camera application, many microlenses having the same dimensions in the X-axis direction and the Y-axis direction are used. However, in video camera applications, the dimensions in the X-axis direction and Y-axis direction may be different. In addition, the above-mentioned bottom octagonal microlens is strictly different in the cross-sectional shape between the direction connecting the opposing vertices of the octagon and the direction connecting the midpoints of the opposing sides. It is substantially equivalent and can be regarded as a spherical lens having a substantially circular bottom surface. In the following description, a case where the bottom surface shape of the microlens is rectangular is also shown. In this case, if the rectangle is a square, the cross-sectional shape of the microlens in the direction connecting the midpoints of the opposite sides of the square and the cross-sectional shape of the microlens in the diagonal direction of the square are different and have different curvatures. In such a case, the curvature based on the cross-sectional shape in the direction connecting the midpoints of the opposing sides will be discussed.

  Next, a case where microlenses having different radii of curvature are formed while keeping the size of the bottom area of the microlens constant will be described. In this case, in order to change the radius of curvature, the height of the microlens is changed. As described above, after the photoresist is exposed and developed, it is melted by heat and formed into a convex lens shape. The method cannot be used. For this reason, a method is used in which a photoresist is exposed and developed using a photomask in which gradation is expressed by a fine dot pattern that does not resolve at the exposure wavelength. FIG. 3 is a diagram showing an example of such a dot pattern, which has 20 × 20 dots expressed on an area for one pixel. In this example, the black part is a light-shielding part and the white part is a light transmission part. A plurality of types of dot patterns are designed according to a desired radius of curvature, and a photomask having a desired arrangement is produced. For example, a microlens array having a plurality of types of curvature radii can be formed by a single photoresist coating, exposure, and development. Although the microlenses formed in this way have a portion that is continuous on the bottom surface between adjacent microlenses (there is no gap), it can be considered that the bottom-side rectangular microlenses are continuously arranged. .

  The solid-state imaging device 1 of the present invention divides an effective imaging region into a plurality of partial regions from the center toward the periphery, and microlenses having the same curvature radius are arranged in each partial region, and the curvature radius of the microlens is An intermediate band portion in which microlenses having respective radii of curvature in adjacent partial regions are mixed is provided at a boundary portion where different partial regions are adjacent to each other. Further, the difference in curvature radius between adjacent microlenses is set to 10% or less, preferably 5% or less. If the difference in the radius of curvature exceeds 10%, the sensitivity difference between the pixels exceeds 10% as described below, which is not preferable because the sensitivity variation increases.

  Here, the difference in sensitivity when the radius of curvature of the microlens is changed will be described. FIG. 22 is a diagram for explaining the relationship between the radius of curvature and sensitivity. In FIG. 22, when the chief ray incident angle (CRA (Chief Ray Angle)) is 0 °, that is, the curvature radius of the microlens is adjusted so as to focus on the surface of the light receiving unit at the center of the effective imaging region. Is a curvature radius of 100%. As shown in FIG. 22, when the chief ray incident angle is 0 °, the sensitivity decreases when the curvature radius is changed by ± 20%, and the sensitivity may decrease by more than 10% per 10% of the curvature radius change. . However, the chief ray incident angle increases as the position of the light receiving part moves away from the central portion of the effective imaging region, and when the chief ray incident angle is 10 ° or 20 °, the radius of curvature is 110% or 120% with respect to the radius of curvature of 100%. In%, there is an example in which the sensitivity increases conversely. That is, at a principal ray incident angle of 20 °, a microlens with a curvature radius of 110% has a sensitivity improvement effect of about 10% with respect to a curvature radius of 100%. In addition, at a chief ray incident angle of 10 °, a microlens having a curvature radius of 110% has a sensitivity improvement effect of about 2% with respect to a curvature radius of 100%. On the other hand, by increasing the radius of curvature, the focal position becomes deeper than the light receiving portion, so it naturally becomes out of focus. However, when the chief ray incident angle is large, the focal position shifts to the back side, but the radius of curvature is increased compared to the deterioration of the focusing state due to the effect of coma aberration that occurs even when the radius of curvature of 100% is maintained. However, the condensing state is considered to be good. Therefore, it is effective as a countermeasure against shading to arrange a microlens having a larger radius of curvature than the central portion around the effective imaging region. Further, since it is meaningful to improve the shading particularly in an area where the chief ray incident angle is large around the effective imaging region, the sensitivity difference due to a 10% change in the radius of curvature near the chief ray incident angle of 0 °. If the sensitivity difference accompanying a change in the radius of curvature of 10% is 10% or less even in a region where the chief ray incident angle is large, the region where the chief ray incident angle is large is It is permissible to mix microlenses having a difference in curvature radius of 10%. Since the difference in sensitivity is preferably 5% or less, the difference in the radius of curvature between adjacent microlenses is more preferably 5% or less.

In the solid-state imaging device of the present invention described above, an example in which the radius of curvature of the microlens is changed as shown in the correction curve shown in FIG. 20 with respect to shading caused by the camera lens characteristics as shown in FIG. Will be described. In this case, as shown in FIG. 4, the X-axis direction of the effective imaging region is divided into nine partial regions (1) to (9), and within each partial region, as shown by the solid line in FIG. Microlenses with the same curvature radius are arranged. Then, an intermediate band portion in which microlenses having respective radii of curvature in the adjacent partial regions are mixed is provided at the boundary portion where the partial regions are adjacent.
The size of the partial region can be set as appropriate. For example, the width can be set in a range of 100 to 10,000 μm, or the number of pixels in the width direction can be set in a range of 50 to 2,000. Can do.

For example, when the mixing ratio of the micro lenses having different curvature radii in the intermediate band portion is 1: 1, the intermediate curvature radii of adjacent partial regions are set as shown by a solid line in FIG. A state in which the microlens is provided appears in the intermediate band portion. As a result, the step-like changes in the nine partial areas are subdivided, and it is possible to prevent the light receiving portions having slightly different sensitivities on the boundary lines between the partial areas, and to prevent defects such as linear sensitivity unevenness. can do.
Further, when the mixing ratio of the microlenses having different curvature radii in the intermediate band portion is changed continuously, that is, from 1: 0 to 0: 1, as shown by a chain line in FIG. The change in average curvature radius can be made smoother.
The width of the intermediate strip portion can be set as appropriate. For example, it can be set in the range of 1 to 50% of the width of the partial region, or in the range of 20 to 5,000 μm.
In the solid-state imaging device 1 of the present invention, the effective imaging region is divided into a plurality of partial regions from the center toward the periphery, and microlenses having different curvature radii are mixed in the plurality of partial regions. The difference in the radius of curvature of adjacent microlenses is 10% or less, preferably 5% or less. If the difference in radius of curvature exceeds 10%, the difference in sensitivity between pixels exceeds 10%, which is not preferable because sensitivity variation increases.

  In such a solid-state imaging device of the present invention, a case where the radius of curvature of the microlens is changed as shown in a correction curve shown in FIG. 20 with respect to shading caused by camera lens characteristics as shown in FIG. This will be described as an example. In this case, as shown in FIG. 5, the X-axis direction of the effective imaging region is divided into nine partial regions (1) to (9). From FIG. 5, in the partial region (1), the curvature radius at the intersection point a between the left chain line and the curvature radius correction curve indicating the partial region (1) is 108%, and the right chain line and the curvature radius correction curve intersection point. The curvature radius at b is 106%, and in the partial area (2), the curvature radius at the intersection c of the right chain line indicating the partial area (2) and the curvature correction curve is 104%, and the partial area (3 ), The curvature radius at the intersection d of the right chain line indicating the partial region (3) and the curvature correction curve is 102%. In the partial region (4), the right chain line indicating the partial region (4) and the curvature radius The radius of curvature at the intersection e of the correction curve is 100%, and the radius of curvature is uniformly 100% in the partial region (5). Furthermore, in the partial area (6), the curvature radius at the intersection f of the left chain line indicating the partial area (6) and the curvature radius correction curve is 101%, and the partial area (7) indicates the partial area (7). The curvature radius at the intersection point g between the left chain line and the curvature radius correction curve is 104%, and in the partial region (8), the curvature radius at the intersection point h between the left chain line and the curvature radius correction curve indicating the partial region (8) is 106%, and in the partial region (9), the curvature radius at the intersection point i between the left chain line and the curvature radius correction curve indicating the partial region (9) is 108%, and at the intersection point j between the right chain line and the curvature radius correction curve. Let the curvature radius of be 110%. In the present invention, the number of partial areas from the center of the effective imaging area in both the X-axis direction and the Y-axis direction may be the same or different.

  Then, when the curvature is the strongest, that is, when the minimum curvature radius is 100%, the bottom of the microlens is a rectangle of 1.6 μm × 1.6 μm, and the height of the microlens is uniformly 0.3 μm. If the radius of curvature is changed by changing the bottom surface dimension, in the partial region (1), microlenses having two types of bottom surface dimensions of 1.671 μm × 1.671 μm and 1.654 μm × 1.654 μm are mixed and arranged. become. In the left-side chain line of the partial area (1), the mixing ratio of 1.671 μm × 1.671 μm microlenses is 100%, and the microlens of 1.654 μm × 1.654 μm is directed to the right side (center direction of the effective imaging region). The lens mixing ratio is gradually increased, and the mixing ratio of the 1.654 μm × 1.654 μm microlens is set to 100% in the right chain line of the partial region (1). Further, these two types of microlenses may be arranged at random while paying attention to the mixing ratio. Hereinafter, in the partial region (2), micro lenses having two kinds of bottom dimensions of 1.654 μm × 1.654 μm and 1.636 μm × 1.636 μm, and in the partial region (3), 1.636 μm × 1.636 μm and 1.618 μm. X1.618 μm two bottom dimension microlenses, partial area (4) 1.618 μm × 1.618 μm and 1.6 μm × 1.6 μm two bottom dimension microlenses, partial area (5) Is a microlens with one bottom dimension of 1.6 μm × 1.6 μm, and a microlens with two bottom dimensions of 1.6 μm × 1.6 μm and 1.636 μm × 1.636 μm in the partial region (6), part In the region (7), microlenses having two bottom dimensions of 1.636 μm × 1.636 μm and 1.654 μm × 1.654 μm, and in the partial region (8), 1.654 μm × 1.654 μm and 1.6 Microlenses with two types of bottom dimensions of 1 μm × 1.671 μm, and microlenses with two types of bottom dimensions of 1.671 μm × 1.671 μm and 1.687 μm × 1.689 μm in the partial region (9) Similar to 1), they are mixed and arranged.

As a result, the change in the radius of curvature according to the curvature radius correction curve shown in FIG. 20 almost continuously, that is, the average radius of curvature of the microlens for each partial region increases from the center to the periphery of the effective imaging region. Such a change can be realized as shown by a solid line in FIG. 6 (the chain line in FIG. 6 is the same as the curve for correcting the radius of curvature in FIG. 20). At this time, since the electron beam drawing grid at the time of manufacturing the haploid mask is 5 nm, electron beam drawing is possible, and a change in the radius of curvature of less than 1 nm, which is not originally on the mask drawing, can be expressed.
Here, the average radius of curvature in the present invention is an average value of the radius of curvature of a microlens in a set of adjacent pixels including a pixel when attention is paid to a pixel.
In the above description, the curvature radius is changed by changing the bottom surface dimension of the microlens with the height of the microlens being uniform, but as described above, the curvature is kept constant while keeping the size of the bottom area of the microlens constant. Of course, microlenses having different radii may be formed. The same applies to the description of the following embodiments.

Next, the solid-state imaging device of the present invention will be described with reference to embodiments.
(First embodiment)
FIG. 7 is a diagram for explaining the arrangement of microlenses in an embodiment of the solid-state imaging device of the present invention. The solid-state imaging device of this embodiment divides an effective imaging region into a plurality of partial regions from the center toward the periphery, and microlenses having the same curvature radius are arranged in each partial region, and the curvature radius of the microlens is In the boundary part where different partial areas are adjacent, an intermediate band-like part in which microlenses of respective curvature radii in the adjacent partial areas are mixed is provided, and further, the difference in curvature radius between adjacent microlenses is 10% or less, Preferably it is 5% or less. That is, as shown in FIG. 7, in a microlens array composed of a plurality of microlenses, the effective imaging area is divided into three in the X-axis direction from the center (0, 0) to the periphery, and three in the Y-axis direction. It is divided into nine types of partial areas (1) to (9) in a mosaic shape. Then, an intermediate band-like portion as shown by a chain line is set in the adjacent partial region.

  Here, it is assumed that the curvature radius of the microlens in each of the partial areas (1) to (9) is changed by changing the bottom surface dimension of the microlens. The radius of curvature of the microlens in the partial area (1) located at the center of the effective imaging area is minimized, the bottom dimension of the microlens is a rectangle of 1.6 μm × 1.6 μm, and the height of the microlens is uniformly 0. When the curvature radius is changed by changing the bottom surface dimension of the microlens to 3 μm, a microlens having a desired bottom surface dimension can be arranged in each partial region as shown in Table 1 below. Here, the fact that there are places where the dimensions in the X-axis direction and the Y-axis direction are changed has the following implications. In the region close to the X axis (for example, the partial regions (2) and (3)), the principal ray incident angle of incident light only needs to be considered in the X axis direction, and therefore the bottom dimension of the microlens is only in the X axis direction. Is changed to change the cross-sectional shape of the microlens in the X-axis direction. In a region close to the Y axis (for example, the partial regions (4) and (7)), the principal ray incident angle of incident light is considered only in the Y axis direction, and the bottom surface dimension of the microlens is only in the Y axis direction. By changing, the cross-sectional shape of the microlens in the Y-axis direction is changed. On the other hand, in regions far from both the X axis and the Y axis (partial regions (5) and (9), or partial regions (6) and (8)), the chief ray incident angles in both the X axis direction and the Y axis direction are used. In consideration of the above, the cross-sectional shape of the microlens in the X-axis direction and the Y-axis direction is changed.

As a result, the microlens can be arranged with the curvature radius being changed substantially continuously from 1.217 μm to 1.338 μm (100% to 110%).
FIG. 8 is an enlarged view of the partial areas (1), (2), (4), and (5) surrounded by a circle in FIG. 7, and the intermediate band portion set in the adjacent partial area is surrounded by a chain line. This is an area and is shown with hatching. In the Y-axis direction of FIG. 8, microlenses having bottom surface dimensions of 1.6 μm × 1.6 μm and 1.6 μm × 1.645 μm are formed in an intermediate band-like portion at the boundary between the partial region (1) and the partial region (4). Arranged together. The mixing ratio of the two types of microlenses can be 1: 1 such that 1.6 μm × 1.6 μm and 1.6 μm × 1.645 μm alternate. Further, the mixing ratio of the two types of microlenses may be continuously changed within a range of 1: 0 to 0: 1. For example, on the partial region (1) side, 1.6 μm × 1.6 μm microlenses are mixed in a ratio of 2/3 and 1.6 μm × 1.645 μm microlenses at a ratio of 1/3, and the partial region (4) side Then, by continuously changing so that the microlenses of 1.6 μm × 1.6 μm are mixed at a ratio of 1/3 and the microlenses of 1.6 μm × 1.645 μm are 2/3, the partial region (1) And a smooth average curvature radius change in the vicinity of the boundary between the partial regions (4). Furthermore, the ratio of the microlens of 1.6 μm × 1.6 μm is almost 100% on the partial area (1) side, and the ratio of the microlens of 1.6 μm × 1.645 μm is increased toward the partial area (4), On the partial area (4) side, microlenses of 1.6 μm × 1.645 μm are mixed so as to be almost 100%, so that the microlens near the boundary between the partial area (1) and the partial area (4) The change in average radius of curvature is smoother.

Similarly, microlenses having bottom areas of 1.645 μm × 1.6 μm and 1.645 μm × 1.645 μm are provided in the middle band-like portion at the boundary between the partial region (2) and the partial region (5) in the Y-axis direction. Are mixed and arranged.
On the other hand, in the X-axis direction of FIG. 8 as well, the bottoms of 1.6 μm × 1.6 μm and 1.645 μm × 1.6 μm are formed on the intermediate band-shaped portion at the boundary between the partial region (1) and the partial region (2). The microlenses of the area are mixedly arranged, and the bottoms of 1.6 μm × 1.645 μm and 1.645 μm × 1.645 μm are formed in the middle strip portion at the boundary between the partial region (4) and the partial region (5). Microlenses of area are mixed and arranged. The mixing ratio of the two types of microlenses can be the same as that of the intermediate band-shaped portion in the Y-axis direction described above.

  In addition, as for the portion where the intermediate band portions intersect, for example, as shown in FIG. 9A, the boundary of the adjacent intermediate band portions can be provided in an oblique direction toward the intersection center. As shown in B), all types of microlenses arranged in the four partial areas (1), (2), (4), and (5) adjacent to the intersecting portion (hatched portion) are mixed. May be arranged. In this case, the mixture ratio increases from the lower left side to the upper right side of the intersecting portion (the direction indicated by the arrow in FIG. 9B), and the average bottom surface dimension around the portion continuously increases (curvature radius). May be arranged so as to be continuously increased), or microlenses having four types of bottom surface dimensions may be randomly arranged, so that the mixing ratio at the intersecting portions may be equalized.

(Second Embodiment)
In the first embodiment described above, the effective imaging area is divided in the X-axis direction and the Y-axis direction to set the partial areas in a mosaic shape. However, the effective imaging area is divided into concentric annular areas around the effective imaging area. It may be a partial area. FIG. 10 is a diagram showing such an embodiment, where the (0, 0) point indicates the center point of the effective imaging area, and the effective imaging area is divided into 4 concentric annular areas centered on this center point. Two partial regions (1) to (4) are defined. Further, an intermediate band-like portion as shown by a chain line is set in the adjacent partial region. Then, the microlens L1 having the smallest curvature radius is arranged in the partial region (1), the microlens L2 having the second smallest curvature radius is arranged in the partial region (2), and the partial region (3) is arranged. Arranges the micro lens L3 with the third smallest radius of curvature, and arranges the micro lens L4 with the largest radius of curvature in the partial region (4). For example, when the pixel pitch is 2 μm, the microlens L1 having the smallest curvature radius is 0.565 μm in height and the curvature radius is 1.944 μm, the curvature radius of 103% of the curvature radius of 1.944 μm is 2.003 μm, The height of the micro lens L2 is 0.545 μm. Further, the curvature radius of 106% of the minimum curvature radius of 1.944 μm is 2.061 μm, the height of the micro lens L3 is 0.527 μm, and the curvature radius of 110% of the minimum curvature radius of 1.944 μm is The height of the microlens L4 is 0.504 μm. In the partial region (1), a microlens having a curvature radius of 1.944 μm is disposed as the microlens L1 having the smallest curvature radius. Hereinafter, the curvature radius of 2.003 μm is set as the microlens L2, and the curvature radius of 2 is set as the microlens L3. A micro lens having a radius of curvature of 2.139 μm is arranged in the partial areas (2), (3), and (4) as the .061 μm micro lens L4.

  In the intermediate band portion, microlenses having respective radii of curvature in adjacent partial regions are mixed. For example, the micro lens L2 and the micro lens L3 are mixed in the intermediate band portion of the partial region (2) and the partial region (3). For example, the mixing ratio can be 1: 1 such that the microlens L2 and the microlens L3 are alternately arranged. Further, the mixing ratio of the two types of microlenses may be continuously changed within a range of 1: 0 to 0: 1. For example, on the partial area (2) side, the microlens L2 is mixed in a ratio of 2/3 and the microlens L3 is mixed in a ratio of 1/3, and on the partial area (3) side, the microlens L2 is 1/3 and the microlens L3 is 2 By continuously changing so as to be mixed at a ratio of / 3, it is possible to smoothly change the average radius of curvature near the boundary between the partial region (2) and the partial region (3). Furthermore, the ratio of the microlens L2 is set to approximately 100% on the partial region (2) side, and the ratio of the microlens L3 is increased toward the partial region (3), and the microlens L3 is approximately 100% on the partial region (3) side. By mixing in such a manner, the change in the average radius of curvature of the microlens near the boundary between the partial region (2) and the partial region (3) becomes smoother.

(Third embodiment)
In the solid-state imaging device according to the present embodiment, the effective imaging region is divided into a plurality of partial regions from the center toward the periphery, and the plurality of partial regions are portions where microlenses having different curvature radii are mixed. It is assumed that there is a region, and the difference in radius of curvature between adjacent microlenses is 10% or less, preferably 5% or less.
FIG. 11 is a layout diagram of microlenses of the solid-state imaging device of the present embodiment. In FIG. 11, the (0, 0) point indicates the center point of the effective imaging region, and in order to avoid the complexity of the drawing, only 30 × 30 pixels in the upper right quarter region from the center point. Is shown. In the solid-state imaging device shown in FIG. 11, both the X-axis direction and the Y-axis direction are divided into partial regions every 5 pixels, the X-axis direction is divided into six (X1) to (X6), and the Y-axis direction ( Y1) to (Y6) are divided into six parts, and one partial region is composed of 5 × 5 pixels. The microlens is composed of two types, a microlens L1 having a small radius of curvature (shown in white in the figure) and a microlens L2 having a large radius of curvature (indicated by hatching in the figure). Has been. Then, as shown in FIG. 11, these microlenses L1 and L2 are arranged in 36 partial areas at a rate of 25 per partial area. FIG. 12 is a diagram showing the two microlenses L1 and L2 in a portion surrounded by a circle in FIG.

  First, the X-axis direction will be described. In the partial region (X1), all the five microlenses are microlenses L1 having a small curvature radius, and in the partial region (X2), one microlens L2 having a large curvature radius is a microlens having a small curvature radius. Four lenses L1 are arranged, and in the partial region (X3), two microlenses L2 having a large curvature radius and three microlenses L1 having a small curvature radius are arranged, and in the partial region (X4). Three microlenses L2 having a large radius of curvature and two microlenses L1 having a small radius of curvature are arranged. In the partial region (X5), four microlenses L2 having a large radius of curvature have a radius of curvature. One small microlens L1 is arranged, and in the partial region (X6), all five microlenses are microlenses L2 having a large curvature radius. There. Also in the Y-axis direction, the arrangement is similar to the arrangement of the two types of microlenses L1 and L2 from the partial area (Y1) to the partial area (Y6) and from the partial area (X1) to the partial area (X6). Is made.

Accordingly, the microlens L2 having a large curvature radius in each of the partial regions defined by being divided into six divisions (X1) to (X6) in the X-axis direction and six divisions (Y1) to (Y6) in the Y-axis direction. Is as shown in FIG. Therefore, the average curvature radius of the microlens in each partial region of 5 pixels × 5 pixels formed by the microlens L1 having a small curvature radius and the microlens L2 having a large curvature radius is an area of 30 pixels × 30 pixels. The region of 30 pixels × 30 pixels can be regarded as one partial region.
In the above example, for example, if the focal length of the microlens L1 having a small radius of curvature is 4 μm and the focal length of the microlens L2 having a large radius of curvature is 4.4 μm, the average focal length of the microlens is 4 μm to 4.4 μm. Can be expressed almost continuously. There are only two types of microlenses that are actually used: a microlens L1 having a small radius of curvature and a microlens L2 having a large radius of curvature, and mask data at the time of mask fabrication can be relatively easily produced.

In the example shown in FIG. 11, two types of microlenses having different curvature radii, that is, a microlens L1 having a small curvature radius and a microlens L2 having a large curvature radius are arranged almost uniformly and regularly in each partial region. However, the present invention is not limited to this. For example, two types of microlenses L1, L1 ′, L2 ′, and L2 having different curvature radii are used by adding two types of microlenses L1 ′ and L2 ′ whose curvature radius is intermediate between the microlenses L1 and L2. As a result, the change in the average curvature radius of the microlens within the 30 pixel × 30 pixel region can be made smoother. In addition, the arrangement of the microlenses in each partial region is not substantially uniform and regular, and may be a random arrangement.
The above-described embodiments are examples, and the solid-state imaging device of the present invention is not limited to these.

[Imaging device]
FIG. 14 is a schematic cross-sectional view showing an embodiment of the imaging apparatus of the present invention. In FIG. 14, an imaging device 31 of the present invention includes a substrate 33 including the solid-state imaging device 32 of the present invention, a sealing member 34 disposed outside the solid-state imaging device 32, and the sealing member 34. And a protective material 35 disposed to face the solid-state imaging device 32 with a desired gap. The solid-state imaging device 32 is connected to an external terminal 38 via a wiring 36 and front and back conductive vias 37. Such a ceramic package type image pickup device 31 can be used for various digital cameras, video cameras, and the like, and the sensitivity, size and thickness of the camera can be reduced.

FIG. 15 is a schematic sectional view showing another embodiment of the imaging apparatus of the present invention. An imaging device 41 of the present invention shown in FIG. 15 is an example of a camera module for a mobile phone, and includes a substrate 43 provided with the solid-state image sensor 42 of the present invention, and a sealing member disposed outside the solid-state image sensor 42. 44, an infrared cut filter 45 disposed so as to face the solid-state imaging device 42 with a desired gap, a lens barrel 46 disposed on the infrared cut filter 45, and the inside of the lens barrel 46 The lens unit 47 attached to the lens is provided. Such an image pickup apparatus 41 can be reduced in size and thickness because the solid-state image pickup element 42 of the present invention is subjected to shading correction and has high sensitivity.
The image pickup apparatus of the present invention is not limited to the above-described embodiment, and any structure that includes the solid-state image pickup element of the present invention as the solid-state image pickup element may be used. it can.

Next, an Example is shown and this invention is demonstrated further in detail.
[Example]
First, a wafer on which a CMOS image sensor having a pixel light receiving portion pitch of 2.0 μm and a pixel number of 2592 × 1944 was formed.
Next, a lower planarization layer, a color filter, an upper planarization layer, and a microlens were formed on the wafer as described below.

(Formation of lower planarization layer)
After cleaning the wafer surface with a spin scraper, a photo-curing acrylic transparent resin material (CT-2020L manufactured by Fuji Microelectronics Materials Co., Ltd.) is spin-coated, and then pre-baking, UV exposure and post-baking are performed. A lower planarizing layer (thickness 0.3 μm) was formed.

(Formation of color filter)
The following materials were prepared as negative photosensitive red materials (R materials), green materials (G materials), and blue materials (B materials).
Material for R: SR-4000L manufactured by Fuji Microelectronic Materials Co., Ltd.
Material for G: SG-4000L manufactured by Fuji Microelectronic Materials Co., Ltd.
Material for B: SB-4000L manufactured by Fuji Microelectronic Materials Co., Ltd.
In the order of formation of G, R, and B, the above materials are spin-coated, and an RGB color filter (thickness 0.8 μm) is formed by performing pre-baking, exposure with a 1/5 reduction type i-line stepper, development, and post-baking. did. As a developing solution, a 50% diluted solution of CD-2000 manufactured by Fuji Microelectronic Materials Co., Ltd. was used. The arrangement pitch of the color filters was 1.998 μm (scaling rate = 99.900%).

(Formation of upper planarization layer)
A light curable acrylic transparent resin material (CT-2020L manufactured by Fuji Microelectronics Materials Co., Ltd.) is spin-coated on the RGB color filter, followed by pre-baking, ultraviolet exposure and post-baking, and an upper flattening layer (Thickness 0.3 μm) was formed.

(Formation of microlenses)
On top flattening layer, spin coating of MFR401L made by JSR Co., Ltd. as a microlens material to 0.7 μm thickness, pre-baking, exposure with 1/5 reduction type i-line stepper, development, post-exposure and post-baking Thus, a microlens was formed. A 1.19% solution of TMAH (tetramethylammonium hydroxide) was used as the developer.

  The above exposure is a method of exposing a photoresist with a fine dot pattern that does not resolve at the exposure wavelength as described in the above embodiment, and a mask pattern for forming a microlens as shown in FIG. The exposure was performed using. As a result, as shown in FIG. 10, four types of microlenses having curvature radii of 1.944 μm, 2.003 μm, 2.061 μm, and 2.139 μm were sequentially arranged in the partial regions (1) to (4). Further, in the intermediate band portion, the mixture ratio of the microlenses having different curvature radii is set to 1: 1. In this case, the partial area (1) is from the center of the effective imaging area on the X axis to 208 pixels, the partial area (2) is from 209 pixels to 558 pixels on the X axis, and the partial area (3) is on the X axis. The partial area (4) is from 955 pixels on the X axis to 1296 pixels on the outermost periphery, from 559 pixels to 954 pixels. The intermediate band between the partial areas is 50 pixels on each side of the boundary lines of (1) and (2), (2) and (3), and (3) and (4), totaling 100 pixels. And the width. In addition, the arrangement pitch of the micro lenses was set to 1.9973 μm (scaling rate = 99.865%).

Next, the bonding pad portion was opened. That is, a positive resist (i-line positive resist PFI-27 manufactured by Sumitomo Chemical Co., Ltd.) is spin-coated, and after pre-baking, exposure and development are performed using a photomask having a pattern corresponding to the bonding pad portion and the scribe portion. Then, the resist in the bonding pad portion and the scribe portion was removed, and then oxygen ashing was performed, and the upper planarization layer and the lower planarization layer on the portion were removed by etching. Next, the positive resist was removed using a resist stripping solution.
Next, the wafer was diced and package assembled to produce the solid-state imaging device of the present invention.

[Comparative example]
A solid-state imaging device was fabricated in the same manner as in the example except that the microlens was formed as follows.
(Formation of microlenses)
On top flattening layer, spin coating of MFR401L made by JSR Co., Ltd. as microlens material, pre-baking, exposure with 1/5 reduction type i-line stepper, development, post-exposure, post-baking, Formed. A 1.19% solution of TMAH (tetramethylammonium hydroxide) was used as the developer.
In the above exposure, exposure was performed using only one type of mask pattern for forming a microlens as shown in FIG. 3, and the radius of curvature of the formed microlens was set to 1.944 μm.

[Evaluation]
For the solid-state imaging device manufactured as described above, the sensitivity was measured under the following conditions, and the results are shown in FIG. As shown in FIG. 16, the solid-state imaging device of the present invention is effectively subjected to shading correction, and the sensitivity distribution (shown by a solid line in FIG. 16) is the sensitivity distribution (solid line in FIG. 16) of the solid-state imaging device of the comparative example. It was confirmed that the improvement was about 10% compared to (shown).
(Sensitivity measurement conditions)
For the manufactured solid-state imaging device, a camera lens having the characteristics shown in FIG. 19 is used.
The sensitivity distribution in the X-axis direction with respect to the white light source was measured.

  The present invention can be applied to various fields in which a small and highly reliable solid-state imaging device and imaging device are required.

It is a schematic block diagram which shows an example of the solid-state image sensor of this invention. It is a figure which shows 1 pixel part of the photomask for microlens formation. It is a figure for demonstrating the photomask for microlens formation. It is a figure which shows the curvature radius of the micro lens for every partial area for demonstrating the solid-state image sensor of this invention. It is a figure which shows the curvature radius of the micro lens for demonstrating the solid-state image sensor of this invention. It is a figure which shows the curvature radius of the micro lens for every partial area for demonstrating the solid-state image sensor of this invention. It is a figure for demonstrating arrangement | positioning of the micro lens in one Embodiment of the solid-state image sensor of this invention. FIG. 8 is an enlarged view of a partial region surrounded by a circle in FIG. 7. It is a figure for demonstrating arrangement | positioning of the micro lens in the cross | intersection part of the intermediate | middle strip | belt-shaped part shown by FIG. It is a figure for demonstrating arrangement | positioning of the micro lens in other embodiment of the solid-state image sensor of this invention. It is a figure for demonstrating arrangement | positioning of the micro lens in other embodiment of the solid-state image sensor of this invention. It is a figure which shows the micro lens from which a curvature radius differs. It is a figure which shows the number in the partial area | region of a micro lens with a big curvature radius in arrangement | positioning of the micro lens shown by FIG. It is a figure for demonstrating an example of the imaging device of this invention. It is a figure for demonstrating the other example of the imaging device of this invention. It is a figure which shows the result of the sensitivity measurement in an Example. It is a figure for demonstrating the shading phenomenon in a solid-state image sensor. It is a figure for demonstrating correction | amendment of the shading in a solid-state image sensor. It is the figure which showed the relationship between the chief ray incident angle of a lens used for an imaging device, and image height. It is a figure which shows correction | amendment of the curvature radius of the micro lens for shading correction | amendment. It is a figure which shows changing the curvature radius of a micro lens in steps for shading correction. It is a figure for demonstrating the relationship between a curvature radius and a sensitivity.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Solid-state image sensor 2 ... Board | substrate 3 ... Light-receiving part 4 ... Light-shielding film 5 ... Passivation layer 6 ... Light-shielding layer 7 ... Lower planarization layer 8 ... Color filter 9 ... Upper planarization layer 10 ... Micro lens array 11 ... Micro lens 31 , 41 ... Imaging device 32, 42 ... Solid-state imaging device

Claims (5)

In a solid-state imaging device comprising at least a plurality of light receiving portions arranged two-dimensionally at a predetermined pitch, and a microlens array in which a plurality of microlenses are two-dimensionally arranged corresponding to the respective light receiving portions,
The microlens constituting the microlens array is composed of two or more kinds of microlenses having different radii of curvature, and the effective imaging area is divided into a plurality of partial areas from the center to the periphery, and the radius of curvature is included in each partial area. Are located at the boundary where adjacent microregions have different radiuses of curvature, and there is an intermediate band where microlenses with different radii of curvature in the adjacent partial regions are mixed. difference in curvature radius of the microlenses is Ri der 10% or less,
The average radius of curvature of the microlens tends to increase from the center of the effective imaging area toward the periphery,
The arrangement of the micro lenses having different curvature radii in the intermediate band portion is such that the mixture ratio is 1: 1 and uniform, or the mixture ratio continuously changes within the range of 1: 0 to 0: 1. arrangement, or a solid-state imaging device characterized random arrangement der Rukoto. In a solid-state imaging device comprising at least a plurality of light receiving portions arranged two-dimensionally at a predetermined pitch, and a microlens array in which a plurality of microlenses are two-dimensionally arranged corresponding to the respective light receiving portions,
The microlens constituting the microlens array is composed of two or more types of microlenses having different radii of curvature, and the effective imaging area is divided into a plurality of partial areas from the center toward the periphery, and the plurality of partial areas include a curvature. there is partial region such as having different radii microlenses are mixed, Ri difference der 10% or less of the radius of curvature of the adjacent microlenses,
The average radius of curvature of the microlens tends to increase from the center of the effective imaging area toward the periphery,
The arrangement of microlenses with different curvature radii in the partial area where microlenses with different curvature radii are mixed is such that the mixing ratio of microlenses with different curvature radii is from the center of the effective imaging area to the periphery in the partial area. An arrangement in which at least one microlens that changes along the direction and has a small radius of curvature is closer to the periphery of the effective imaging region than a microlens that has a large radius of curvature, or the mixing ratio is uniform in the partial region arrangement is, or the solid-state imaging device characterized random arrangement der Rukoto. The solid-state imaging device according to claim 1 or claim 2 wherein the partial region is characterized by a mosaic. 3. The solid-state imaging device according to claim 1, wherein the partial area is a concentric annular area centering on an effective imaging area center. 4. An imaging apparatus comprising the solid-state imaging device according to claim 1 .

Images