The present invention relates to a solid-state image pickup device which includes light receiving region where photoelectric conversion elements are two-dimensionally arranged, and microlenses each corresponding to the photoelectric conversion elements. The present invention particularly relates to a solid-state image pickup device which includes a microlens layer where microlenses are arranged to be deviated from locations directly above the photoelectric conversion elements toward the optical center of the light receiving region.
In the conventional solid-state image pickup device disclosed in Patent Document 2 and the like, a plurality of wiring layers each are deviated toward the central portion at different shrinkage rates (size-reduction rates). This improves the light collection rate of a peripheral portion even with the plurality of wiring layers.
The conventional solid-state image pickup devices have the incident angle characteristic indicated by the broken line in
Along with the miniaturization of recent cameras typified by a digital camera and a camera built into a mobile phone, their exit pupil distances become shorter. The term “exit pupil” means a virtual image of a lens (lens 11 in
In the conventional solid-state image pickup devices, however, the microlenses are arranged so as to have a pitch smaller than the pitch of the light receiving sections, and to deviate toward the central portion with distance from the central portion. If an incident angle characteristic is not proportional to an image height, for example, in a case when an incident angle becomes smaller in reverse halfway through, the conventional solid-state image pickup devices are disadvantageous in decreasing their light collection rate.
In light of the foregoing problem, it is an object of the present invention to provide a solid-state image pickup device as well as a mask manufacturing method which improve a light collection rate if an incident angle characteristic is not proportional to an image height.
In order to achieve the above object, the solid-state image pickup device according to the present invention includes: a light receiving region which includes photoelectric conversion elements that are arranged two-dimensionally; and a microlens layer which includes microlens that introduce incident light into the photoelectric conversion elements, wherein said microlens layer has a plurality of regions each of which has a pitch of the microlenses, the pitch being different depending on the region, and at least one of the regions has a plurality of microlenses whose pitch is different from a pitch of the photoelectric conversion elements.
According to this configuration, if an image height and an incident angle characteristic are not in proportional relation, a light collection rate is improved by allowing each of the regions to respond to an actual incident angle.
Further, each of the regions may include a plurality of microlenses, and a pitch of the microlenses may be constant within each of the regions, the pitch being different depending on the region.
According to this configuration, the pitch of the microlenses is constant within each region, and the pitch varies on a region to region basis. This allows each of the regions to respond to an actual incident angle appropriately so as to improve a light collection rate.
Furthermore, the regions may include: a plurality of first regions each having microlenses; and a second region having no microlens, the second region being a boundary region between the first regions, a pitch of the microlenses may be constant within each of the first regions, the pitch being different depending on the region and a pitch of a microlense which are arranged across the second region may be different from the pitch of the other microlenses within the first regions.
According to this configuration, the pitch of the microlenses being arranged across the second region is set appropriately so as to allow each of the first regions to respond to an actual incident angle appropriately, thereby improving a light collection rate.
Still further, the regions may be arranged concentrically.
Still further, the regions may be arranged polygonally.
Still further, the pitches of the microlenses in the respective regions may correspond to respective different incident angles of the incident light.
Moreover, the mask manufacturing method according to the present invention is for manufacturing a mask to be used for manufacturing a solid-state image pickup device which includes a light receiving region having photoelectric conversion elements arranged two-dimensionally. The mask manufacturing method may include steps of: drawing a partial pattern for a first region at a first correction size-reduction rate with reference to an optical center of the light receiving region, the partial pattern for the first region being a part of a pattern above the light receiving region and existing in the first region; and drawing a partial pattern for a second region different from the first region at a second correction size-reduction rate with reference to the optical center of the light receiving region, the partial pattern for the second region being another part of the pattern and existing in the second region, and the second region being different from the first region or having an edge overlapped with the first region.
According to this method, a mask suitable for manufacturing the above solid-state image pickup device is manufactured. Specifically, if an image height and an incident angle characteristic are not in proportional relation, but are brought into reverse relation halfway through, a mask for forming the first region and the second region which deal with the reversion is manufactured.
Further, the first region may be a concentrical region with the optical center as its center, and the second region may be a doughnut-shaped region with the optical center as its center.
Furthermore, the first region may be a polygonal region with the optical center as its center, and the second region may be a polygonal, doughnut-shaped region with the optical center as its center.
Still further, the first correction size-reduction rate may be equal to the second correction size-reduction rate, each of the partial patterns may represent elements which are arranged two-dimensionally and each of which corresponds to the photoelectric conversion elements, and in said drawing for the second region, a pitch of adjacent elements across a boundary between the first region and the second region may be larger than a pitch of the elements within the first region.
Still further, said drawing for the first region and said drawing for the second region may be performed at the same time.
According to this method, the partial patterns are drawn collectively so as to reduce the number of man-hours required for mask manufacturing.
Still further, the first correction size-reduction rate may be different from the second correction size-reduction rate.
Still further, each of the partial patterns in said drawing for the first and second regions may have a layout data for drawing, in which a value obtained by dividing a minimum width as a wiring rule in the solid-state image pickup device manufacturing process by its size-reduction rate is a design rule.
According to this method, even though the solid-state image pickup device is manufactured with a size-reduced pattern drawn on a mask, a minimum width is reserved as the wiring rule in the manufacturing process.
Still further, in said drawing for the first and second regions, the design rule may be applied to wiring drawing, contact drawing for connecting wires together, and microlens drawing as the elements.
According to the solid-state image pickup device and the mask manufacturing method according to the present invention, even if an image height and an incident angle characteristic are not in proportional relation, a light collection rate is improved.
The solid-state image pickup device includes a semiconductor substrate 1, wiring layers 3, contact layers 4, light blocking layers/wiring layers 5a, color filter layers 5b, and microlens layers 6. The semiconductor substrate 1 includes light receiving sections 2 which are two-dimensionally arranged. The microlens layer 6, which collects light, includes a plurality of image pickup regions 1 and 2 each having microlenses, and a boundary region having no microlens between the image pickup regions. The pitch of the microlenses is constant in each of the image pickup regions. All the image pickup regions have their own pitches. However, a pitch of the microlenses arranged across the boundary region, is different from the pitch of the other microlenses in the same image pickup region. Each pitch between the microlenses is smaller than the pitch between the light receiving sections 2 (S0+L0). The microlenses are arranged to deviate toward the optical axis center. The light blocking layer/wiring layer 5a and the contact layer 4 are also arranged to deviate toward the optical axis center. The deviation amount for each pixel (shrinkage rate, or size-reduction rate) becomes smaller in the order of the microlens layer 6, the color filter layer 5b, and the light blocking layer/wiring layer 5a.
According to this configuration, if an incident angle characteristic is not proportional to an image height, the microlenses belonging to the second microlens group improve the light collection rate of all the microlenses on their outer periphery side.
In other words, the pitch of the adjacent opening portions across the boundary between the image pickup region 1 and the image pickup region 2 (S+L12 in
The image pickup regions each correspond to the angle of the light incident on each region.
As has been described above, according to the solid-state image pickup device of this embodiment, if an image height and an incident angle characteristic are not in proportional relation, but are brought into reverse relation halfway through, the light collection rate on the outer side is improved by the microlenses belonging to the second microlens group. In addition, the regions of the number according to the degree of an incident angle are provided so that the microlenses deviate suitably for the incident angle. This deviation is achieved by setting the distance between the microlenses or the distance L12 between the opening portions, across the boundary, to be larger than the corresponding distances within each of the regions.
Hereinafter, a description is given for a manufacturing method of the mask to be used for manufacturing the solid-state image pickup device according to the first and second embodiments.
In a mask manufacturing process, an incident angle characteristic is obtained in the apparatus to contain the solid-state image pickup device (S1), and the light receiving region is then divided into a plurality of regions based on the incident angle characteristic (S2). In this case, the light receiving region is divided according to incident angle characteristics as shown in
Next, layout data is created for each region (S2). The layout data defines the layout of the elements within each of the divided regions. Respective patterns denote elements to be arranged two-dimensionally corresponding to the photoelectric conversion elements. In this case, the elements include a microlens, a wiring line, a light blocking wiring line, and a contact.
Then, a pattern is drawn on a glass substrate to be an actual mask based on the layout data for each region (S3 and S4). The pattern drawing is performed by coating the glass substrate with a material for a reflection film, exposing the coated substrate to light, and then developing the substrate, so as to form a reflection film thereon. In this case, the partial pattern for each of the divided region is drawn by exposing to light, based on the layout data, with reference to the optical center of the light receiving region, at the correction size-reduction rate for each region. More specifically, the pattern for each region has layout data with the value obtained by dividing a minimum width as a wiring rule in the solid-state image pickup device manufacturing process by its size-reduction rate as a design rule. In other words, since the final result drawn by the whole solid-state image pickup device has to be based on the consistent design rule, the layout data before pattern drawing with size reduction has to be applied based on the design rule fitting the correction size-reduction rate. The design rule is applied for contact drawing for connecting wiring lines, wiring layer drawing, color filter drawing, and microlens drawing. In Step S3 and S4, when the pattern for each region is drawn, the pattern drawing is performed so that the pitch of the adjacent elements across the boundary between one region and another region is larger than the pitch of the elements within each region.
When pattern drawing is finished for all the regions, a complete mask is obtained (S5). A single mask is manufactured in each of the following steps included in the solid-state image pickup device manufacturing process: the step of forming the wiring layer 3; the step of forming the contact layer 5; the step of forming the light blocking layer/wiring layer 5; and the step of forming the microlens layer 6. Alternatively, one mask may be employed for common use, if applicable.
By employing the masks thus manufactured, the solid-state image pickup device according to the first and second embodiments is manufactured through the following steps: the step of forming the wiring layer 3 (S11); the step of forming the contact layer 4 (S12); the step of forming the light blocking layer/wiring layer 5a (S13); the step of forming the color filter layer 5b (S14); and the step of forming the microlens layer 6 (S15).
According to the above mask manufacturing process, a mask suited for manufacturing the above solid-state image pickup device is manufactured. Specifically, if an image height and an incident angle characteristic are not in proportional relation, but are brought into reverse relation halfway through, a mask for forming a plurality of regions which deal with the reversion is manufactured.
If there are a plurality of regions to be drawn at the same correction size-reduction rate, pattern drawing may be performed collectively instead of the individual drawing processes to be performed in Steps S4 and S5. The regions are exposed to light at the same time so as to improve efficiency.
The present invention is suitable for a solid-state image pickup device having microlenses included in each of the light-receiving elements formed on a semiconductor substrate, a manufacturing method of a mask used for manufacturing the solid-state image pickup device, and a camera having the solid-state image pickup device. Examples of the present invention's application include a CCD image sensor, an MOS image sensor, a digital still camera, a mobile phone with a camera, a camera built into a notebook computer, and a camera unit to be connected to information processing equipment.
Number | Date | Country | Kind |
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2004-362849 | Dec 2004 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2005/022382 | 12/6/2005 | WO | 00 | 6/13/2007 |